Research ArticleDesign of CDTA and VDTA Based Frequency Agile Filters
Neeta Pandey1 Aseem Sayal2 Richa Choudhary2 and Rajeshwari Pandey1
1Department of Electronics and Communication Engineering Delhi Technological University Delhi 110042 India2Department of Electrical Engineering Delhi Technological University Delhi 110042 India
Correspondence should be addressed to Neeta Pandey n66pandeyrediffmailcom
Received 21 May 2014 Revised 3 November 2014 Accepted 3 November 2014 Published 23 December 2014
Academic Editor Weisheng Zhao
Copyright copy 2014 Neeta Pandey et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited
This paper presents frequency agile filters based on current difference transconductance amplifier (CDTA) and voltage differencetransconductance amplifier (VDTA)The proposed agile filter configurations employ grounded passive components and hence aresuitable for integration Extensive SPICE simulations using 025 120583mTSMCCMOS technologymodel parameters are carried out forfunctional verification The proposed configurations are compared in terms of performance parameters such as power dissipationsignal to noise ratio (SNR) and maximum output noise voltage
1 Introduction
The rapid evolution of wireless services has led to demandfor one-fits-all ldquoanalogrdquo front end solution These servicesuse different standards and therefore necessitate developmentof integrated multistandard transceivers as they result inreduction of size price complexity and power consumptionThe parameters of integrated transceiver can be modified inorder to be able to adapt to the specifications of each standard[1] Practically the designs employ either elements handlingvarious standards in parallel or reconfigurable elementsThe frequency agile filter (FAF) [1ndash10] characterized byadjustment range reconfigurability and agility may be usedin transceivers The term shadow filters is sometimes used inliterature to refer to FAF [11 12] The literature survey showsthat a limited number of topologies of active FAF are availableand are based on op-amp [1] and current mode active block[2 3] and CMOS [4]
There is a wide range of current mode building blocksavailable in open literature Among these blocks currentdifference transconductance amplifier (CDTA) [11] is mostsuitable for current mode signal processing owing to its lowinput and high output impedances respectivelyTheVDTA isyet another recently introduced building block which workson a principle similar to that of CDTA except that theinput current differencing unit is replaced by the voltage
differencing circuit Many applications such as filters andoscillators based on CDTA and VDTA are available and havebeen reported in the literature [13ndash27] and references citedtherein
The main intention of this paper is to present CDTA andVDTA based frequency agile filter topologies The proposedfilters are suitable for integration as these employ groundedcapacitors and a resistor The paper is organised as followsThe FAF implementation scheme is briefly reviewed inSection 2 The CDTA based Class 0 Class 1 and Class 2FAF are presented in Section 3 Section 4 deals with therealization ofVDTAbasedClass 0 Class 1 andClass 2 FAF InSection 5 nonideal analysis of filters is presented Simulationresults are provided in Section 6 to substantiate the proposedFAF topologies The performance characteristics of filtertopologies are described in Section 7The paper is concludedin Section 8
2 Implementation Scheme of FAF
The implementation scheme of frequency agile filter (FAF)[3] is briefly reviewed in this section
21 Class 0 FAF Aclassical second order filter with band pass(119868BP) and low pass (119868LP) outputs of Figure 1 is designated as
Hindawi Publishing CorporationAdvances in ElectronicsVolume 2014 Article ID 176243 15 pageshttpdxdoiorg1011552014176243
2 Advances in Electronics
ILP
IBP
IIN Class 0 FAF
Figure 1 Class 0 FAF [3]
ILP
IBPIIN Class 0 FAF
A
+
+
Figure 2 Class 1 FAF
Class 0 FAF [3] The transfer functions of Class 0 FAF aregiven by
119879BP (119904) =119868BP119868IN
=119896119904
1 + 120572119904 + 1205731199042
119879LP (119904) =119868LP119868IN
=119901
1 + 120572119904 + 1205731199042
(1)
The center frequency (1198910) and quality factor (119876) of the
filter are represented by (2) and (3) respectively
1198910=
1
2120587radic120573 (2)
119876 =radic120573
120572 (3)
22 Class 1 FAF The basic block diagram of Class 1 FAF isshown in Figure 2 wherein the low pass output of the Class0 FAF is amplified (with variable gain 119860) and fed back to theinput The characteristic frequency (119891
0119860) and quality factor
(119876119860) of Class 1 FAF are given by (4) and (5) respectively
1198910119860
= 1198910radic(1 + 119860119901) (4)
119876119860= 119876radic(1 + 119860119901)
(5)
23 Class n FAF The method outlined for Class 1 FAFrealization can be extended for Class 119899 FAF implementationas shown in Figure 3 This requires 119899 amplifiers each withgain 119860 (119860
1= 1198602= sdot sdot sdot = 119860
119899minus1= 119860119899) to be placed in 119899
feedback paths obtained in the same way as done in Class 1implementationThe characteristic parameters of Class 119899FAFare given by
1198910119860119899
= 1198910(1 + 119860119901)
1198992
119876119860119899
= 119876 (1 + 119860119901)1198992
(6)
Class (n minus 1) FAF
ILP
IBPIIN
A
+
+
Figure 3 Class 119899 FAF
Vp
Vn
Vz
IBias
CDTA
p
z
n
Iz
In g
Ip
x+
xminus
Ix+
Ixminus
Vx+
Vxminus
Figure 4 Symbol of CDTA
3 CDTA Based FAF
The CDTA [11ndash18] consists of a unity-gain current sourcecontrolled by the difference of the input currents and atransconductance amplifier providing electronic tunabilitythrough its transconductance gain The CDTA symbol isshown in Figure 4 and its terminal characteristics in matrixform are given by
[[[[[
[
119881119901
119881119899
119868119911
119868119909+
119868119909minus
]]]]]
]
=
[[[[[
[
0 0 0 0 0
0 0 0 0 0
1 minus1 0 0 0
0 0 119892 0 0
0 0 119892 0 0
]]]]]
]
[[[[[
[
119868119901
119868119899
119881119911
119881119909+
119881119909minus
]]]]]
]
(7)
where 119892 is transconductance of the CDTA The CMOSimplementation of CDTA [16] is given in Figure 5 The tran-sistor network comprising transistors Mc1ndashMc17 performs[16] current differencing operation on the currents entering at119901 and 119899 nodes which is available at119885 terminalThe voltage of119911 terminal drives the source coupled pair (transistors (Mc18ndashMc21)) [16] of differential amplifier (Mc18ndashMc26) giving atransconductance of 119892 The value of transconductance (119892) isexpressed as
119892 = radic2120583119862119900119909(119882
119871)1921
119868Bias (8)
which can be adjusted by bias current 119868Bias of CDTA
Advances in Electronics 3
Mc1
Mc2
Mc3
Mc4
Mc5
Mc6
Mc7
Mc8
Mc9
Mc10
Mc11
Mc12Mc15
Mc13
Mc14
Mc16
Mc22 Mc24
Mc18
Mc19
Mc20
Mc21
Mc23Mc17
Mc25
Mc26
n
p
z
IBias
VDD
VSS
VSS
x+xminus
Figure 5 CMOS implementation of CDTA [16]
31 CDTA Based Class 0 FAF The CDTA based secondorder filter employing two CDTA blocks and two groundedcapacitors is shown in Figure 6 The second CDTA blockuses additional TA block with its current output terminalsdenoted by 119909+
119888and 119909
minus
119888 It provides both low pass and band
pass responses at high output impedance and can be usedas Class 0 FAF The current flowing through 119909
+ and 119909minus
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923 The low pass and band pass transfer functions of CDTA
based Class 0 FAF are given by (9) and (10) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922
(9)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
11198923+ 11989211198922
(10)
The center frequency and quality factor of Class 0 FAF areexpressed as
1198910=
1
2120587radic11989211198922
11986211198622
(11)
119876 =1
1198923
radic119892111989221198622
1198621
(12)
It may be noted that the 119876 of the Class 0 FAF can becontrolled independent of 119891
0by varying 119892
3
32 CDTA Based Class 1 FAF The CDTA based Class 1 FAFis shown in Figure 7 It employs Class 0 FAF of Figure 6 alongwith an additional TA block (provides an output current
which is product of its transconductance and voltage differ-ence between noninverting (+) and inverting (minus) terminals)and one grounded resistorThe TA block in the feedback pathfunctions as an amplifier with tunable gain 119860 as given in
119860 = 1198924119877 (13)
where 1198924is the transconductance of TA block and is given by
radic2120583119862119900119909(119882119871)
1921119868Bias4
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (14) and (15) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4) (14)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4) (15)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (16) and (17) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
radic(1 + 1198924119877) (16)
119876119860=
1
1198923
radic119892111989221198622
1198621
radic(1 + 1198924119877) (17)
33 CDTA Based Class 2 FAF The CDTA based Class 2FAF is shown in Figure 8 It employs two CDTA blocks twogrounded capacitors three TA blocks and two groundedresistors The TA blocks in the feedback path are used asamplifier with tunable gain 119860 The gain 119860 of TA based
4 Advances in Electronics
IBias1
p
nz
p
nz zc
ILP
IBP
IBP
IIN
C1 C2
CDTAg1
CDTAg2 g3
x+
xminus x+c
xminusc
x+
xminus
IBias3IBias2
Figure 6 CDTA based Class 0 FAF
R
IBias1 IBias2 IBias3
p
z
CDTA CDTAp
n nz zc
ILPIBP
IBP
IIN
C1 C2
g1 g2 g3 x+cxminusc
x+
xminusx+
xminus
g4TA +
minus
Figure 7 CDTA based Class 1 FAF
R
R
IBias1
p
z
CDTACDTA
p
nnz
zc
ILPIBP
IBP
IIN
C1
C2
g1g2 g2 g3
x+x+
xminus
xminus
x+cxminusc
xminuscc
x+cc
g4TA +
minus
g4TA +
minus
g4
TA+
minus
IBias2 IBias2 IBias3
Figure 8 CDTA based Class 2 FAF
Advances in Electronics 5
g
TA+
minus
IIN
VIN
Figure 9 TA realization of a grounded resistor
VDTA
z
p
n
zc
Ip
In
Iz
Vz
Vp
Vn
g1 g2
Ix+
Ixminus
Vx+
Vxminus
x+
xminus
Vzc
Izc
IBias2IBias1
Figure 10 Symbol of VDTA
amplifier is given by (18) The second CDTA block uses twoadditional TA blocks It provides both low pass and bandpass responses at high output impedance and can be used asClass 0 FAF The current flowing through 119909+ 119909minus 119909+
119888119888 and 119909minus
119888119888
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923
119860 = 1198924119877 (18)
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (19) and (20) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (19)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (20)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (21) and (22) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
(1 + 1198924119877) (21)
119876119860=
1
1198923
radic119892111989221198622
1198621
(1 + 1198924119877) (22)
The proposed filter uses grounded resistor of value 119877 (=
1119892) which can easily be implemented using the TA basedstructure given in Figure 9
4 The VDTA Based FAF
The circuit symbol and the CMOS realization of VDTA [2021] are shown in Figures 10 and 11 respectively The VDTAconsists of two transconductance (TC) stages termed as inputand output stages The input differential voltage (119881
119901minus 119881119899) is
converted to current 119868119911through TC gain (119892
1) of input stage
and second stage converts the voltage at 119911 terminal (119881119911) to
current (119868119909) through its TC gain (119892
2) The port relations of
VDTA can thus be defined by the following matrix
[[[
[
119868119911
119868119911119888
119868119909+
119868119909minus
]]]
]
=[[[
[
1198921
minus1198921
0
minus1198921
1198921
0
0 0 1198922
0 0 minus1198922
]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(23)
The TC 1198921and TC 119892
2are expressed by (24) which can be
adjusted by bias currents 119868Bias1 and 119868Bias2 respectively
1198921= radic2120583119862
119900119909(119882
119871)12
119868Bias1
1198922= radic2120583119862
119900119909(119882
119871)56
119868Bias2
(24)
41 VDTA Based Class 0 FAF The VDTA based Class 0FAF employing single VDTA and two grounded capacitorsis shown in Figure 12 This circuit configuration is basedon second order filter presented in [21] However to allowindependent control of quality factor and center frequency anadditional TA block with transconductance 119892
2is included in
VDTA The current flowing through 119911 terminal is controlledby transconductance 119892
1whereas current flowing through 119911
119888
terminal is controlled by 1198922 The terminal characteristics of
the modified VDTA block are given by (25)The low pass andband pass transfer functions of VDTA based Class 0 FAF aregiven by (26) and (27) respectively
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1198921minus1198921
0
minus1198921
1198921
0
1198922
minus1198922
0
minus1198922
1198922
0
0 0 1198923
0 0 minus1198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(25)
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923
(26)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
21198922+ 11989211198923
(27)
The center frequency and quality factor of Class 0 FAF areexpressed by (28) The center frequency can be controlled by
6 Advances in Electronics
M12
p
z
M11
M8
M5
M7
M6
M9 M10
M4
M1
M3
M2
M13
n
zc
M14M15
M16
M17 M18
iz
IBias1 IBias 2
+VDD
minusVSS
x+xminus
Figure 11 CMOS implementation of VDTA [21]
IBias1
p
z
n
zc
ILP
IBP
IINVDTA
z998400 z998400c
I998400BP
C1
C2
g1 g2 g3
x+
xminus
IBias2 IBias3
Figure 12 The VDTA based Class 0 FAF
119868Bias1 and 119868Bias3 whereas quality factor can be independentlycontrolled by 119868Bias2
1198910=
1
2120587radic11989211198923
11986211198622
119876 =1
1198922
radic119892111989231198621
1198622
(28)
42 VDTA Based Class 1 FAF The VDTA based Class 1 FAFis shown in Figure 13 It employs two VDTA blocks and twogrounded capacitors The second VDTA block is used asamplifier with tunable gain 119860 The gain 119860 of VDTA basedamplifier is given by
119860 =1198924
1198923
(29)
and can be adjusted by varying 119868Bias3 and 119868Bias4
The low pass and band pass transfer functions of VDTAbased Class 1 FAF are given by (30) and (31) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (30)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (31)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (32) and (33) respectivelyThe center frequency can be independently controlled byvarying 119868Bias2 without changing center frequency
1198910119860
=1
2120587radic11989211198923
11986211198622
(radic1 +1198924
1198923
) (32)
119876119860=
1
1198922
radic119892111989231198621
1198622
(radic1 +1198924
1198923
) (33)
43 VDTA Based Class 2 FAF The VDTA based Class 2FAF is shown in Figure 14 which employs three VDTAstwo grounded capacitors and one grounded resistor Thesecond VDTA block is used as amplifier with tunable gain 119860The gain 119860 of VDTA based amplifier is given by (34) Theproposed filter uses grounded resistor which can easily beimplemented using the TA with transconductance equal to1198923based structure given in Figure 9 To realize second order
filter 119868Bias7 is set to value of 119868Bias4 such that 1198927is equal to 119892
4
and 119868Bias6 is set to value such that 1198926 is equal to sum of 1198923and
1198924 that is 119892
6= 1198923+ 1198924 Consider
119860 =1198924
1198923
(34)
which can be adjusted by varying 119868Bias3 and 119868Bias2 therebymaking 119891
0119860tunable
Advances in Electronics 7
IBias1
p
z zn
p
n
zczc
ILP
IBP
IIN
z998400 z998400c
I998400BP
VDTA VDTAg1 g2 g3 g4 g5
C1
C2
x+
xminus
x+
xminus
IBias3 IBias4 IBias5IBias2
Figure 13 VDTA based Class 1 FAF
IBias1
p
zz zn
p
n
p
nzczc zc
IBP
IIN
z998400 z998400c
I998400BP
ILP
VDTAg1 g2 g3
VDTAg4 g5
VDTAg6 g7
C1
C2
1g3
x+
xminus
x+
xminus
x+
xminus
IBias3 IBias4 IBias5 IBias6 IBias7IBias2
Figure 14 VDTA based Class 2 FAF
01
025 05
10
20
30
50
100
150
200
300
0
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
0495MHz
15MHz
245MHz
323MHz
IBias =
IBias =
IBias =IBias =
1120583A10120583A
30120583A60120583A
Figure 15 Frequency response of CDTA based Class 0 FAF with119868Bias1 = 119868Bias2 = 119868Bias
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (35) and (36) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (35)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (36)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (37) and (38) respectively
1198910119860
=1
2120587radic11989211198923
11986211198622
(1 +1198924
1198923
) (37)
119876119860=
1
1198922
radic119892111989231198621
1198622
(1 +1198924
1198923
) (38)
5 Nonideal Analysis
In this section nonideal analysis of CDTA and VDTA basedClass 0 FAF is presented
51 Nonideal Analysis of Class 0 CDTA Based FAF In prac-tice the transfer functions (9) and (10) modify due to non-idealities which are classified as tracking errors and parasitesThe tracking errors cause current transfer from 119901 and 119899 portsto 119911 port to differ from unity value and are represented by 120572
119901
and 120572119899 There is deviation in transconductance transfer from
119911 to 119909+ and 119909minus ports which is modeled by 120573119892119881119911The parasites
denoted by resistances 119877119901and 119877
119899are at 119901 and 119899 terminals
shunt output impedances (119877119862) are present at terminals 119911119911119888 119909+ and 119909
minus and 119909+
119888and 119909
minus
119888 The effect of the parasites
is highly dependent on the topology A close inspection ofthe circuit of Figure 6 shows that the parasitic capacitances
8 Advances in Electronics
05 10 20 30 50 70 100 200 3000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
121MHz
363MHz
575MHz
741MHz
IBias =
IBias =
IBias =
IBias =1120583A10120583A
30120583A60120583A
Figure 16 Frequency response of CDTA based Class 1 FAF with119868Bias1 = 119868Bias2 = 119868Bias
05 10 20 30 50 70 100 200 300 5000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
158MHz
485MHz
78MHz
995MHz
IBias =
IBias =
IBias =
IBias =10120583A30120583A60120583A
1120583A
Figure 17 Frequency response of CDTA based Class 2 FAF with119868Bias1 = 119868Bias2 = 119868Bias
present at 119911 terminal can be easily accommodated in externalcapacitances
Reanalysis of the proposed circuit (Figure 6) yields thefollowing nonideal transfer functions
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
Class 0 FAF [3] The transfer functions of Class 0 FAF aregiven by
119879BP (119904) =119868BP119868IN
=119896119904
1 + 120572119904 + 1205731199042
119879LP (119904) =119868LP119868IN
=119901
1 + 120572119904 + 1205731199042
(1)
The center frequency (1198910) and quality factor (119876) of the
filter are represented by (2) and (3) respectively
1198910=
1
2120587radic120573 (2)
119876 =radic120573
120572 (3)
22 Class 1 FAF The basic block diagram of Class 1 FAF isshown in Figure 2 wherein the low pass output of the Class0 FAF is amplified (with variable gain 119860) and fed back to theinput The characteristic frequency (119891
0119860) and quality factor
(119876119860) of Class 1 FAF are given by (4) and (5) respectively
1198910119860
= 1198910radic(1 + 119860119901) (4)
119876119860= 119876radic(1 + 119860119901)
(5)
23 Class n FAF The method outlined for Class 1 FAFrealization can be extended for Class 119899 FAF implementationas shown in Figure 3 This requires 119899 amplifiers each withgain 119860 (119860
1= 1198602= sdot sdot sdot = 119860
119899minus1= 119860119899) to be placed in 119899
feedback paths obtained in the same way as done in Class 1implementationThe characteristic parameters of Class 119899FAFare given by
1198910119860119899
= 1198910(1 + 119860119901)
1198992
119876119860119899
= 119876 (1 + 119860119901)1198992
(6)
Class (n minus 1) FAF
ILP
IBPIIN
A
+
+
Figure 3 Class 119899 FAF
Vp
Vn
Vz
IBias
CDTA
p
z
n
Iz
In g
Ip
x+
xminus
Ix+
Ixminus
Vx+
Vxminus
Figure 4 Symbol of CDTA
3 CDTA Based FAF
The CDTA [11ndash18] consists of a unity-gain current sourcecontrolled by the difference of the input currents and atransconductance amplifier providing electronic tunabilitythrough its transconductance gain The CDTA symbol isshown in Figure 4 and its terminal characteristics in matrixform are given by
[[[[[
[
119881119901
119881119899
119868119911
119868119909+
119868119909minus
]]]]]
]
=
[[[[[
[
0 0 0 0 0
0 0 0 0 0
1 minus1 0 0 0
0 0 119892 0 0
0 0 119892 0 0
]]]]]
]
[[[[[
[
119868119901
119868119899
119881119911
119881119909+
119881119909minus
]]]]]
]
(7)
where 119892 is transconductance of the CDTA The CMOSimplementation of CDTA [16] is given in Figure 5 The tran-sistor network comprising transistors Mc1ndashMc17 performs[16] current differencing operation on the currents entering at119901 and 119899 nodes which is available at119885 terminalThe voltage of119911 terminal drives the source coupled pair (transistors (Mc18ndashMc21)) [16] of differential amplifier (Mc18ndashMc26) giving atransconductance of 119892 The value of transconductance (119892) isexpressed as
119892 = radic2120583119862119900119909(119882
119871)1921
119868Bias (8)
which can be adjusted by bias current 119868Bias of CDTA
Advances in Electronics 3
Mc1
Mc2
Mc3
Mc4
Mc5
Mc6
Mc7
Mc8
Mc9
Mc10
Mc11
Mc12Mc15
Mc13
Mc14
Mc16
Mc22 Mc24
Mc18
Mc19
Mc20
Mc21
Mc23Mc17
Mc25
Mc26
n
p
z
IBias
VDD
VSS
VSS
x+xminus
Figure 5 CMOS implementation of CDTA [16]
31 CDTA Based Class 0 FAF The CDTA based secondorder filter employing two CDTA blocks and two groundedcapacitors is shown in Figure 6 The second CDTA blockuses additional TA block with its current output terminalsdenoted by 119909+
119888and 119909
minus
119888 It provides both low pass and band
pass responses at high output impedance and can be usedas Class 0 FAF The current flowing through 119909
+ and 119909minus
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923 The low pass and band pass transfer functions of CDTA
based Class 0 FAF are given by (9) and (10) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922
(9)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
11198923+ 11989211198922
(10)
The center frequency and quality factor of Class 0 FAF areexpressed as
1198910=
1
2120587radic11989211198922
11986211198622
(11)
119876 =1
1198923
radic119892111989221198622
1198621
(12)
It may be noted that the 119876 of the Class 0 FAF can becontrolled independent of 119891
0by varying 119892
3
32 CDTA Based Class 1 FAF The CDTA based Class 1 FAFis shown in Figure 7 It employs Class 0 FAF of Figure 6 alongwith an additional TA block (provides an output current
which is product of its transconductance and voltage differ-ence between noninverting (+) and inverting (minus) terminals)and one grounded resistorThe TA block in the feedback pathfunctions as an amplifier with tunable gain 119860 as given in
119860 = 1198924119877 (13)
where 1198924is the transconductance of TA block and is given by
radic2120583119862119900119909(119882119871)
1921119868Bias4
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (14) and (15) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4) (14)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4) (15)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (16) and (17) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
radic(1 + 1198924119877) (16)
119876119860=
1
1198923
radic119892111989221198622
1198621
radic(1 + 1198924119877) (17)
33 CDTA Based Class 2 FAF The CDTA based Class 2FAF is shown in Figure 8 It employs two CDTA blocks twogrounded capacitors three TA blocks and two groundedresistors The TA blocks in the feedback path are used asamplifier with tunable gain 119860 The gain 119860 of TA based
4 Advances in Electronics
IBias1
p
nz
p
nz zc
ILP
IBP
IBP
IIN
C1 C2
CDTAg1
CDTAg2 g3
x+
xminus x+c
xminusc
x+
xminus
IBias3IBias2
Figure 6 CDTA based Class 0 FAF
R
IBias1 IBias2 IBias3
p
z
CDTA CDTAp
n nz zc
ILPIBP
IBP
IIN
C1 C2
g1 g2 g3 x+cxminusc
x+
xminusx+
xminus
g4TA +
minus
Figure 7 CDTA based Class 1 FAF
R
R
IBias1
p
z
CDTACDTA
p
nnz
zc
ILPIBP
IBP
IIN
C1
C2
g1g2 g2 g3
x+x+
xminus
xminus
x+cxminusc
xminuscc
x+cc
g4TA +
minus
g4TA +
minus
g4
TA+
minus
IBias2 IBias2 IBias3
Figure 8 CDTA based Class 2 FAF
Advances in Electronics 5
g
TA+
minus
IIN
VIN
Figure 9 TA realization of a grounded resistor
VDTA
z
p
n
zc
Ip
In
Iz
Vz
Vp
Vn
g1 g2
Ix+
Ixminus
Vx+
Vxminus
x+
xminus
Vzc
Izc
IBias2IBias1
Figure 10 Symbol of VDTA
amplifier is given by (18) The second CDTA block uses twoadditional TA blocks It provides both low pass and bandpass responses at high output impedance and can be used asClass 0 FAF The current flowing through 119909+ 119909minus 119909+
119888119888 and 119909minus
119888119888
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923
119860 = 1198924119877 (18)
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (19) and (20) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (19)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (20)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (21) and (22) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
(1 + 1198924119877) (21)
119876119860=
1
1198923
radic119892111989221198622
1198621
(1 + 1198924119877) (22)
The proposed filter uses grounded resistor of value 119877 (=
1119892) which can easily be implemented using the TA basedstructure given in Figure 9
4 The VDTA Based FAF
The circuit symbol and the CMOS realization of VDTA [2021] are shown in Figures 10 and 11 respectively The VDTAconsists of two transconductance (TC) stages termed as inputand output stages The input differential voltage (119881
119901minus 119881119899) is
converted to current 119868119911through TC gain (119892
1) of input stage
and second stage converts the voltage at 119911 terminal (119881119911) to
current (119868119909) through its TC gain (119892
2) The port relations of
VDTA can thus be defined by the following matrix
[[[
[
119868119911
119868119911119888
119868119909+
119868119909minus
]]]
]
=[[[
[
1198921
minus1198921
0
minus1198921
1198921
0
0 0 1198922
0 0 minus1198922
]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(23)
The TC 1198921and TC 119892
2are expressed by (24) which can be
adjusted by bias currents 119868Bias1 and 119868Bias2 respectively
1198921= radic2120583119862
119900119909(119882
119871)12
119868Bias1
1198922= radic2120583119862
119900119909(119882
119871)56
119868Bias2
(24)
41 VDTA Based Class 0 FAF The VDTA based Class 0FAF employing single VDTA and two grounded capacitorsis shown in Figure 12 This circuit configuration is basedon second order filter presented in [21] However to allowindependent control of quality factor and center frequency anadditional TA block with transconductance 119892
2is included in
VDTA The current flowing through 119911 terminal is controlledby transconductance 119892
1whereas current flowing through 119911
119888
terminal is controlled by 1198922 The terminal characteristics of
the modified VDTA block are given by (25)The low pass andband pass transfer functions of VDTA based Class 0 FAF aregiven by (26) and (27) respectively
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1198921minus1198921
0
minus1198921
1198921
0
1198922
minus1198922
0
minus1198922
1198922
0
0 0 1198923
0 0 minus1198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(25)
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923
(26)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
21198922+ 11989211198923
(27)
The center frequency and quality factor of Class 0 FAF areexpressed by (28) The center frequency can be controlled by
6 Advances in Electronics
M12
p
z
M11
M8
M5
M7
M6
M9 M10
M4
M1
M3
M2
M13
n
zc
M14M15
M16
M17 M18
iz
IBias1 IBias 2
+VDD
minusVSS
x+xminus
Figure 11 CMOS implementation of VDTA [21]
IBias1
p
z
n
zc
ILP
IBP
IINVDTA
z998400 z998400c
I998400BP
C1
C2
g1 g2 g3
x+
xminus
IBias2 IBias3
Figure 12 The VDTA based Class 0 FAF
119868Bias1 and 119868Bias3 whereas quality factor can be independentlycontrolled by 119868Bias2
1198910=
1
2120587radic11989211198923
11986211198622
119876 =1
1198922
radic119892111989231198621
1198622
(28)
42 VDTA Based Class 1 FAF The VDTA based Class 1 FAFis shown in Figure 13 It employs two VDTA blocks and twogrounded capacitors The second VDTA block is used asamplifier with tunable gain 119860 The gain 119860 of VDTA basedamplifier is given by
119860 =1198924
1198923
(29)
and can be adjusted by varying 119868Bias3 and 119868Bias4
The low pass and band pass transfer functions of VDTAbased Class 1 FAF are given by (30) and (31) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (30)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (31)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (32) and (33) respectivelyThe center frequency can be independently controlled byvarying 119868Bias2 without changing center frequency
1198910119860
=1
2120587radic11989211198923
11986211198622
(radic1 +1198924
1198923
) (32)
119876119860=
1
1198922
radic119892111989231198621
1198622
(radic1 +1198924
1198923
) (33)
43 VDTA Based Class 2 FAF The VDTA based Class 2FAF is shown in Figure 14 which employs three VDTAstwo grounded capacitors and one grounded resistor Thesecond VDTA block is used as amplifier with tunable gain 119860The gain 119860 of VDTA based amplifier is given by (34) Theproposed filter uses grounded resistor which can easily beimplemented using the TA with transconductance equal to1198923based structure given in Figure 9 To realize second order
filter 119868Bias7 is set to value of 119868Bias4 such that 1198927is equal to 119892
4
and 119868Bias6 is set to value such that 1198926 is equal to sum of 1198923and
1198924 that is 119892
6= 1198923+ 1198924 Consider
119860 =1198924
1198923
(34)
which can be adjusted by varying 119868Bias3 and 119868Bias2 therebymaking 119891
0119860tunable
Advances in Electronics 7
IBias1
p
z zn
p
n
zczc
ILP
IBP
IIN
z998400 z998400c
I998400BP
VDTA VDTAg1 g2 g3 g4 g5
C1
C2
x+
xminus
x+
xminus
IBias3 IBias4 IBias5IBias2
Figure 13 VDTA based Class 1 FAF
IBias1
p
zz zn
p
n
p
nzczc zc
IBP
IIN
z998400 z998400c
I998400BP
ILP
VDTAg1 g2 g3
VDTAg4 g5
VDTAg6 g7
C1
C2
1g3
x+
xminus
x+
xminus
x+
xminus
IBias3 IBias4 IBias5 IBias6 IBias7IBias2
Figure 14 VDTA based Class 2 FAF
01
025 05
10
20
30
50
100
150
200
300
0
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
0495MHz
15MHz
245MHz
323MHz
IBias =
IBias =
IBias =IBias =
1120583A10120583A
30120583A60120583A
Figure 15 Frequency response of CDTA based Class 0 FAF with119868Bias1 = 119868Bias2 = 119868Bias
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (35) and (36) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (35)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (36)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (37) and (38) respectively
1198910119860
=1
2120587radic11989211198923
11986211198622
(1 +1198924
1198923
) (37)
119876119860=
1
1198922
radic119892111989231198621
1198622
(1 +1198924
1198923
) (38)
5 Nonideal Analysis
In this section nonideal analysis of CDTA and VDTA basedClass 0 FAF is presented
51 Nonideal Analysis of Class 0 CDTA Based FAF In prac-tice the transfer functions (9) and (10) modify due to non-idealities which are classified as tracking errors and parasitesThe tracking errors cause current transfer from 119901 and 119899 portsto 119911 port to differ from unity value and are represented by 120572
119901
and 120572119899 There is deviation in transconductance transfer from
119911 to 119909+ and 119909minus ports which is modeled by 120573119892119881119911The parasites
denoted by resistances 119877119901and 119877
119899are at 119901 and 119899 terminals
shunt output impedances (119877119862) are present at terminals 119911119911119888 119909+ and 119909
minus and 119909+
119888and 119909
minus
119888 The effect of the parasites
is highly dependent on the topology A close inspection ofthe circuit of Figure 6 shows that the parasitic capacitances
8 Advances in Electronics
05 10 20 30 50 70 100 200 3000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
121MHz
363MHz
575MHz
741MHz
IBias =
IBias =
IBias =
IBias =1120583A10120583A
30120583A60120583A
Figure 16 Frequency response of CDTA based Class 1 FAF with119868Bias1 = 119868Bias2 = 119868Bias
05 10 20 30 50 70 100 200 300 5000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
158MHz
485MHz
78MHz
995MHz
IBias =
IBias =
IBias =
IBias =10120583A30120583A60120583A
1120583A
Figure 17 Frequency response of CDTA based Class 2 FAF with119868Bias1 = 119868Bias2 = 119868Bias
present at 119911 terminal can be easily accommodated in externalcapacitances
Reanalysis of the proposed circuit (Figure 6) yields thefollowing nonideal transfer functions
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
31 CDTA Based Class 0 FAF The CDTA based secondorder filter employing two CDTA blocks and two groundedcapacitors is shown in Figure 6 The second CDTA blockuses additional TA block with its current output terminalsdenoted by 119909+
119888and 119909
minus
119888 It provides both low pass and band
pass responses at high output impedance and can be usedas Class 0 FAF The current flowing through 119909
+ and 119909minus
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923 The low pass and band pass transfer functions of CDTA
based Class 0 FAF are given by (9) and (10) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922
(9)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
11198923+ 11989211198922
(10)
The center frequency and quality factor of Class 0 FAF areexpressed as
1198910=
1
2120587radic11989211198922
11986211198622
(11)
119876 =1
1198923
radic119892111989221198622
1198621
(12)
It may be noted that the 119876 of the Class 0 FAF can becontrolled independent of 119891
0by varying 119892
3
32 CDTA Based Class 1 FAF The CDTA based Class 1 FAFis shown in Figure 7 It employs Class 0 FAF of Figure 6 alongwith an additional TA block (provides an output current
which is product of its transconductance and voltage differ-ence between noninverting (+) and inverting (minus) terminals)and one grounded resistorThe TA block in the feedback pathfunctions as an amplifier with tunable gain 119860 as given in
119860 = 1198924119877 (13)
where 1198924is the transconductance of TA block and is given by
radic2120583119862119900119909(119882119871)
1921119868Bias4
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (14) and (15) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4) (14)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4) (15)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (16) and (17) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
radic(1 + 1198924119877) (16)
119876119860=
1
1198923
radic119892111989221198622
1198621
radic(1 + 1198924119877) (17)
33 CDTA Based Class 2 FAF The CDTA based Class 2FAF is shown in Figure 8 It employs two CDTA blocks twogrounded capacitors three TA blocks and two groundedresistors The TA blocks in the feedback path are used asamplifier with tunable gain 119860 The gain 119860 of TA based
4 Advances in Electronics
IBias1
p
nz
p
nz zc
ILP
IBP
IBP
IIN
C1 C2
CDTAg1
CDTAg2 g3
x+
xminus x+c
xminusc
x+
xminus
IBias3IBias2
Figure 6 CDTA based Class 0 FAF
R
IBias1 IBias2 IBias3
p
z
CDTA CDTAp
n nz zc
ILPIBP
IBP
IIN
C1 C2
g1 g2 g3 x+cxminusc
x+
xminusx+
xminus
g4TA +
minus
Figure 7 CDTA based Class 1 FAF
R
R
IBias1
p
z
CDTACDTA
p
nnz
zc
ILPIBP
IBP
IIN
C1
C2
g1g2 g2 g3
x+x+
xminus
xminus
x+cxminusc
xminuscc
x+cc
g4TA +
minus
g4TA +
minus
g4
TA+
minus
IBias2 IBias2 IBias3
Figure 8 CDTA based Class 2 FAF
Advances in Electronics 5
g
TA+
minus
IIN
VIN
Figure 9 TA realization of a grounded resistor
VDTA
z
p
n
zc
Ip
In
Iz
Vz
Vp
Vn
g1 g2
Ix+
Ixminus
Vx+
Vxminus
x+
xminus
Vzc
Izc
IBias2IBias1
Figure 10 Symbol of VDTA
amplifier is given by (18) The second CDTA block uses twoadditional TA blocks It provides both low pass and bandpass responses at high output impedance and can be used asClass 0 FAF The current flowing through 119909+ 119909minus 119909+
119888119888 and 119909minus
119888119888
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923
119860 = 1198924119877 (18)
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (19) and (20) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (19)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (20)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (21) and (22) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
(1 + 1198924119877) (21)
119876119860=
1
1198923
radic119892111989221198622
1198621
(1 + 1198924119877) (22)
The proposed filter uses grounded resistor of value 119877 (=
1119892) which can easily be implemented using the TA basedstructure given in Figure 9
4 The VDTA Based FAF
The circuit symbol and the CMOS realization of VDTA [2021] are shown in Figures 10 and 11 respectively The VDTAconsists of two transconductance (TC) stages termed as inputand output stages The input differential voltage (119881
119901minus 119881119899) is
converted to current 119868119911through TC gain (119892
1) of input stage
and second stage converts the voltage at 119911 terminal (119881119911) to
current (119868119909) through its TC gain (119892
2) The port relations of
VDTA can thus be defined by the following matrix
[[[
[
119868119911
119868119911119888
119868119909+
119868119909minus
]]]
]
=[[[
[
1198921
minus1198921
0
minus1198921
1198921
0
0 0 1198922
0 0 minus1198922
]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(23)
The TC 1198921and TC 119892
2are expressed by (24) which can be
adjusted by bias currents 119868Bias1 and 119868Bias2 respectively
1198921= radic2120583119862
119900119909(119882
119871)12
119868Bias1
1198922= radic2120583119862
119900119909(119882
119871)56
119868Bias2
(24)
41 VDTA Based Class 0 FAF The VDTA based Class 0FAF employing single VDTA and two grounded capacitorsis shown in Figure 12 This circuit configuration is basedon second order filter presented in [21] However to allowindependent control of quality factor and center frequency anadditional TA block with transconductance 119892
2is included in
VDTA The current flowing through 119911 terminal is controlledby transconductance 119892
1whereas current flowing through 119911
119888
terminal is controlled by 1198922 The terminal characteristics of
the modified VDTA block are given by (25)The low pass andband pass transfer functions of VDTA based Class 0 FAF aregiven by (26) and (27) respectively
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1198921minus1198921
0
minus1198921
1198921
0
1198922
minus1198922
0
minus1198922
1198922
0
0 0 1198923
0 0 minus1198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(25)
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923
(26)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
21198922+ 11989211198923
(27)
The center frequency and quality factor of Class 0 FAF areexpressed by (28) The center frequency can be controlled by
6 Advances in Electronics
M12
p
z
M11
M8
M5
M7
M6
M9 M10
M4
M1
M3
M2
M13
n
zc
M14M15
M16
M17 M18
iz
IBias1 IBias 2
+VDD
minusVSS
x+xminus
Figure 11 CMOS implementation of VDTA [21]
IBias1
p
z
n
zc
ILP
IBP
IINVDTA
z998400 z998400c
I998400BP
C1
C2
g1 g2 g3
x+
xminus
IBias2 IBias3
Figure 12 The VDTA based Class 0 FAF
119868Bias1 and 119868Bias3 whereas quality factor can be independentlycontrolled by 119868Bias2
1198910=
1
2120587radic11989211198923
11986211198622
119876 =1
1198922
radic119892111989231198621
1198622
(28)
42 VDTA Based Class 1 FAF The VDTA based Class 1 FAFis shown in Figure 13 It employs two VDTA blocks and twogrounded capacitors The second VDTA block is used asamplifier with tunable gain 119860 The gain 119860 of VDTA basedamplifier is given by
119860 =1198924
1198923
(29)
and can be adjusted by varying 119868Bias3 and 119868Bias4
The low pass and band pass transfer functions of VDTAbased Class 1 FAF are given by (30) and (31) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (30)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (31)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (32) and (33) respectivelyThe center frequency can be independently controlled byvarying 119868Bias2 without changing center frequency
1198910119860
=1
2120587radic11989211198923
11986211198622
(radic1 +1198924
1198923
) (32)
119876119860=
1
1198922
radic119892111989231198621
1198622
(radic1 +1198924
1198923
) (33)
43 VDTA Based Class 2 FAF The VDTA based Class 2FAF is shown in Figure 14 which employs three VDTAstwo grounded capacitors and one grounded resistor Thesecond VDTA block is used as amplifier with tunable gain 119860The gain 119860 of VDTA based amplifier is given by (34) Theproposed filter uses grounded resistor which can easily beimplemented using the TA with transconductance equal to1198923based structure given in Figure 9 To realize second order
filter 119868Bias7 is set to value of 119868Bias4 such that 1198927is equal to 119892
4
and 119868Bias6 is set to value such that 1198926 is equal to sum of 1198923and
1198924 that is 119892
6= 1198923+ 1198924 Consider
119860 =1198924
1198923
(34)
which can be adjusted by varying 119868Bias3 and 119868Bias2 therebymaking 119891
0119860tunable
Advances in Electronics 7
IBias1
p
z zn
p
n
zczc
ILP
IBP
IIN
z998400 z998400c
I998400BP
VDTA VDTAg1 g2 g3 g4 g5
C1
C2
x+
xminus
x+
xminus
IBias3 IBias4 IBias5IBias2
Figure 13 VDTA based Class 1 FAF
IBias1
p
zz zn
p
n
p
nzczc zc
IBP
IIN
z998400 z998400c
I998400BP
ILP
VDTAg1 g2 g3
VDTAg4 g5
VDTAg6 g7
C1
C2
1g3
x+
xminus
x+
xminus
x+
xminus
IBias3 IBias4 IBias5 IBias6 IBias7IBias2
Figure 14 VDTA based Class 2 FAF
01
025 05
10
20
30
50
100
150
200
300
0
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
0495MHz
15MHz
245MHz
323MHz
IBias =
IBias =
IBias =IBias =
1120583A10120583A
30120583A60120583A
Figure 15 Frequency response of CDTA based Class 0 FAF with119868Bias1 = 119868Bias2 = 119868Bias
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (35) and (36) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (35)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (36)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (37) and (38) respectively
1198910119860
=1
2120587radic11989211198923
11986211198622
(1 +1198924
1198923
) (37)
119876119860=
1
1198922
radic119892111989231198621
1198622
(1 +1198924
1198923
) (38)
5 Nonideal Analysis
In this section nonideal analysis of CDTA and VDTA basedClass 0 FAF is presented
51 Nonideal Analysis of Class 0 CDTA Based FAF In prac-tice the transfer functions (9) and (10) modify due to non-idealities which are classified as tracking errors and parasitesThe tracking errors cause current transfer from 119901 and 119899 portsto 119911 port to differ from unity value and are represented by 120572
119901
and 120572119899 There is deviation in transconductance transfer from
119911 to 119909+ and 119909minus ports which is modeled by 120573119892119881119911The parasites
denoted by resistances 119877119901and 119877
119899are at 119901 and 119899 terminals
shunt output impedances (119877119862) are present at terminals 119911119911119888 119909+ and 119909
minus and 119909+
119888and 119909
minus
119888 The effect of the parasites
is highly dependent on the topology A close inspection ofthe circuit of Figure 6 shows that the parasitic capacitances
8 Advances in Electronics
05 10 20 30 50 70 100 200 3000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
121MHz
363MHz
575MHz
741MHz
IBias =
IBias =
IBias =
IBias =1120583A10120583A
30120583A60120583A
Figure 16 Frequency response of CDTA based Class 1 FAF with119868Bias1 = 119868Bias2 = 119868Bias
05 10 20 30 50 70 100 200 300 5000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
158MHz
485MHz
78MHz
995MHz
IBias =
IBias =
IBias =
IBias =10120583A30120583A60120583A
1120583A
Figure 17 Frequency response of CDTA based Class 2 FAF with119868Bias1 = 119868Bias2 = 119868Bias
present at 119911 terminal can be easily accommodated in externalcapacitances
Reanalysis of the proposed circuit (Figure 6) yields thefollowing nonideal transfer functions
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
amplifier is given by (18) The second CDTA block uses twoadditional TA blocks It provides both low pass and bandpass responses at high output impedance and can be used asClass 0 FAF The current flowing through 119909+ 119909minus 119909+
119888119888 and 119909minus
119888119888
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923
119860 = 1198924119877 (18)
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (19) and (20) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (19)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (20)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (21) and (22) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
(1 + 1198924119877) (21)
119876119860=
1
1198923
radic119892111989221198622
1198621
(1 + 1198924119877) (22)
The proposed filter uses grounded resistor of value 119877 (=
1119892) which can easily be implemented using the TA basedstructure given in Figure 9
4 The VDTA Based FAF
The circuit symbol and the CMOS realization of VDTA [2021] are shown in Figures 10 and 11 respectively The VDTAconsists of two transconductance (TC) stages termed as inputand output stages The input differential voltage (119881
119901minus 119881119899) is
converted to current 119868119911through TC gain (119892
1) of input stage
and second stage converts the voltage at 119911 terminal (119881119911) to
current (119868119909) through its TC gain (119892
2) The port relations of
VDTA can thus be defined by the following matrix
[[[
[
119868119911
119868119911119888
119868119909+
119868119909minus
]]]
]
=[[[
[
1198921
minus1198921
0
minus1198921
1198921
0
0 0 1198922
0 0 minus1198922
]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(23)
The TC 1198921and TC 119892
2are expressed by (24) which can be
adjusted by bias currents 119868Bias1 and 119868Bias2 respectively
1198921= radic2120583119862
119900119909(119882
119871)12
119868Bias1
1198922= radic2120583119862
119900119909(119882
119871)56
119868Bias2
(24)
41 VDTA Based Class 0 FAF The VDTA based Class 0FAF employing single VDTA and two grounded capacitorsis shown in Figure 12 This circuit configuration is basedon second order filter presented in [21] However to allowindependent control of quality factor and center frequency anadditional TA block with transconductance 119892
2is included in
VDTA The current flowing through 119911 terminal is controlledby transconductance 119892
1whereas current flowing through 119911
119888
terminal is controlled by 1198922 The terminal characteristics of
the modified VDTA block are given by (25)The low pass andband pass transfer functions of VDTA based Class 0 FAF aregiven by (26) and (27) respectively
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1198921minus1198921
0
minus1198921
1198921
0
1198922
minus1198922
0
minus1198922
1198922
0
0 0 1198923
0 0 minus1198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(25)
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923
(26)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
21198922+ 11989211198923
(27)
The center frequency and quality factor of Class 0 FAF areexpressed by (28) The center frequency can be controlled by
6 Advances in Electronics
M12
p
z
M11
M8
M5
M7
M6
M9 M10
M4
M1
M3
M2
M13
n
zc
M14M15
M16
M17 M18
iz
IBias1 IBias 2
+VDD
minusVSS
x+xminus
Figure 11 CMOS implementation of VDTA [21]
IBias1
p
z
n
zc
ILP
IBP
IINVDTA
z998400 z998400c
I998400BP
C1
C2
g1 g2 g3
x+
xminus
IBias2 IBias3
Figure 12 The VDTA based Class 0 FAF
119868Bias1 and 119868Bias3 whereas quality factor can be independentlycontrolled by 119868Bias2
1198910=
1
2120587radic11989211198923
11986211198622
119876 =1
1198922
radic119892111989231198621
1198622
(28)
42 VDTA Based Class 1 FAF The VDTA based Class 1 FAFis shown in Figure 13 It employs two VDTA blocks and twogrounded capacitors The second VDTA block is used asamplifier with tunable gain 119860 The gain 119860 of VDTA basedamplifier is given by
119860 =1198924
1198923
(29)
and can be adjusted by varying 119868Bias3 and 119868Bias4
The low pass and band pass transfer functions of VDTAbased Class 1 FAF are given by (30) and (31) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (30)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (31)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (32) and (33) respectivelyThe center frequency can be independently controlled byvarying 119868Bias2 without changing center frequency
1198910119860
=1
2120587radic11989211198923
11986211198622
(radic1 +1198924
1198923
) (32)
119876119860=
1
1198922
radic119892111989231198621
1198622
(radic1 +1198924
1198923
) (33)
43 VDTA Based Class 2 FAF The VDTA based Class 2FAF is shown in Figure 14 which employs three VDTAstwo grounded capacitors and one grounded resistor Thesecond VDTA block is used as amplifier with tunable gain 119860The gain 119860 of VDTA based amplifier is given by (34) Theproposed filter uses grounded resistor which can easily beimplemented using the TA with transconductance equal to1198923based structure given in Figure 9 To realize second order
filter 119868Bias7 is set to value of 119868Bias4 such that 1198927is equal to 119892
4
and 119868Bias6 is set to value such that 1198926 is equal to sum of 1198923and
1198924 that is 119892
6= 1198923+ 1198924 Consider
119860 =1198924
1198923
(34)
which can be adjusted by varying 119868Bias3 and 119868Bias2 therebymaking 119891
0119860tunable
Advances in Electronics 7
IBias1
p
z zn
p
n
zczc
ILP
IBP
IIN
z998400 z998400c
I998400BP
VDTA VDTAg1 g2 g3 g4 g5
C1
C2
x+
xminus
x+
xminus
IBias3 IBias4 IBias5IBias2
Figure 13 VDTA based Class 1 FAF
IBias1
p
zz zn
p
n
p
nzczc zc
IBP
IIN
z998400 z998400c
I998400BP
ILP
VDTAg1 g2 g3
VDTAg4 g5
VDTAg6 g7
C1
C2
1g3
x+
xminus
x+
xminus
x+
xminus
IBias3 IBias4 IBias5 IBias6 IBias7IBias2
Figure 14 VDTA based Class 2 FAF
01
025 05
10
20
30
50
100
150
200
300
0
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
0495MHz
15MHz
245MHz
323MHz
IBias =
IBias =
IBias =IBias =
1120583A10120583A
30120583A60120583A
Figure 15 Frequency response of CDTA based Class 0 FAF with119868Bias1 = 119868Bias2 = 119868Bias
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (35) and (36) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (35)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (36)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (37) and (38) respectively
1198910119860
=1
2120587radic11989211198923
11986211198622
(1 +1198924
1198923
) (37)
119876119860=
1
1198922
radic119892111989231198621
1198622
(1 +1198924
1198923
) (38)
5 Nonideal Analysis
In this section nonideal analysis of CDTA and VDTA basedClass 0 FAF is presented
51 Nonideal Analysis of Class 0 CDTA Based FAF In prac-tice the transfer functions (9) and (10) modify due to non-idealities which are classified as tracking errors and parasitesThe tracking errors cause current transfer from 119901 and 119899 portsto 119911 port to differ from unity value and are represented by 120572
119901
and 120572119899 There is deviation in transconductance transfer from
119911 to 119909+ and 119909minus ports which is modeled by 120573119892119881119911The parasites
denoted by resistances 119877119901and 119877
119899are at 119901 and 119899 terminals
shunt output impedances (119877119862) are present at terminals 119911119911119888 119909+ and 119909
minus and 119909+
119888and 119909
minus
119888 The effect of the parasites
is highly dependent on the topology A close inspection ofthe circuit of Figure 6 shows that the parasitic capacitances
8 Advances in Electronics
05 10 20 30 50 70 100 200 3000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
121MHz
363MHz
575MHz
741MHz
IBias =
IBias =
IBias =
IBias =1120583A10120583A
30120583A60120583A
Figure 16 Frequency response of CDTA based Class 1 FAF with119868Bias1 = 119868Bias2 = 119868Bias
05 10 20 30 50 70 100 200 300 5000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
158MHz
485MHz
78MHz
995MHz
IBias =
IBias =
IBias =
IBias =10120583A30120583A60120583A
1120583A
Figure 17 Frequency response of CDTA based Class 2 FAF with119868Bias1 = 119868Bias2 = 119868Bias
present at 119911 terminal can be easily accommodated in externalcapacitances
Reanalysis of the proposed circuit (Figure 6) yields thefollowing nonideal transfer functions
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
amplifier is given by (18) The second CDTA block uses twoadditional TA blocks It provides both low pass and bandpass responses at high output impedance and can be used asClass 0 FAF The current flowing through 119909+ 119909minus 119909+
119888119888 and 119909minus
119888119888
is controlled through transconductance 1198922whereas current
flowing through terminals 119909+119888and 119909
minus
119888is controlled through
1198923
119860 = 1198924119877 (18)
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (19) and (20) respectively
119868LP119868IN
=11989211198922
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (19)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
11198923+ 11989211198922(1 + 119877119892
4)2 (20)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (21) and (22) respectively
1198910119860
=1
2120587radic11989211198922
11986211198622
(1 + 1198924119877) (21)
119876119860=
1
1198923
radic119892111989221198622
1198621
(1 + 1198924119877) (22)
The proposed filter uses grounded resistor of value 119877 (=
1119892) which can easily be implemented using the TA basedstructure given in Figure 9
4 The VDTA Based FAF
The circuit symbol and the CMOS realization of VDTA [2021] are shown in Figures 10 and 11 respectively The VDTAconsists of two transconductance (TC) stages termed as inputand output stages The input differential voltage (119881
119901minus 119881119899) is
converted to current 119868119911through TC gain (119892
1) of input stage
and second stage converts the voltage at 119911 terminal (119881119911) to
current (119868119909) through its TC gain (119892
2) The port relations of
VDTA can thus be defined by the following matrix
[[[
[
119868119911
119868119911119888
119868119909+
119868119909minus
]]]
]
=[[[
[
1198921
minus1198921
0
minus1198921
1198921
0
0 0 1198922
0 0 minus1198922
]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(23)
The TC 1198921and TC 119892
2are expressed by (24) which can be
adjusted by bias currents 119868Bias1 and 119868Bias2 respectively
1198921= radic2120583119862
119900119909(119882
119871)12
119868Bias1
1198922= radic2120583119862
119900119909(119882
119871)56
119868Bias2
(24)
41 VDTA Based Class 0 FAF The VDTA based Class 0FAF employing single VDTA and two grounded capacitorsis shown in Figure 12 This circuit configuration is basedon second order filter presented in [21] However to allowindependent control of quality factor and center frequency anadditional TA block with transconductance 119892
2is included in
VDTA The current flowing through 119911 terminal is controlledby transconductance 119892
1whereas current flowing through 119911
119888
terminal is controlled by 1198922 The terminal characteristics of
the modified VDTA block are given by (25)The low pass andband pass transfer functions of VDTA based Class 0 FAF aregiven by (26) and (27) respectively
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1198921minus1198921
0
minus1198921
1198921
0
1198922
minus1198922
0
minus1198922
1198922
0
0 0 1198923
0 0 minus1198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(25)
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923
(26)
119868BP119868IN
=11990411986221198921
119862111986221199042 + 119904119862
21198922+ 11989211198923
(27)
The center frequency and quality factor of Class 0 FAF areexpressed by (28) The center frequency can be controlled by
6 Advances in Electronics
M12
p
z
M11
M8
M5
M7
M6
M9 M10
M4
M1
M3
M2
M13
n
zc
M14M15
M16
M17 M18
iz
IBias1 IBias 2
+VDD
minusVSS
x+xminus
Figure 11 CMOS implementation of VDTA [21]
IBias1
p
z
n
zc
ILP
IBP
IINVDTA
z998400 z998400c
I998400BP
C1
C2
g1 g2 g3
x+
xminus
IBias2 IBias3
Figure 12 The VDTA based Class 0 FAF
119868Bias1 and 119868Bias3 whereas quality factor can be independentlycontrolled by 119868Bias2
1198910=
1
2120587radic11989211198923
11986211198622
119876 =1
1198922
radic119892111989231198621
1198622
(28)
42 VDTA Based Class 1 FAF The VDTA based Class 1 FAFis shown in Figure 13 It employs two VDTA blocks and twogrounded capacitors The second VDTA block is used asamplifier with tunable gain 119860 The gain 119860 of VDTA basedamplifier is given by
119860 =1198924
1198923
(29)
and can be adjusted by varying 119868Bias3 and 119868Bias4
The low pass and band pass transfer functions of VDTAbased Class 1 FAF are given by (30) and (31) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (30)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (31)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (32) and (33) respectivelyThe center frequency can be independently controlled byvarying 119868Bias2 without changing center frequency
1198910119860
=1
2120587radic11989211198923
11986211198622
(radic1 +1198924
1198923
) (32)
119876119860=
1
1198922
radic119892111989231198621
1198622
(radic1 +1198924
1198923
) (33)
43 VDTA Based Class 2 FAF The VDTA based Class 2FAF is shown in Figure 14 which employs three VDTAstwo grounded capacitors and one grounded resistor Thesecond VDTA block is used as amplifier with tunable gain 119860The gain 119860 of VDTA based amplifier is given by (34) Theproposed filter uses grounded resistor which can easily beimplemented using the TA with transconductance equal to1198923based structure given in Figure 9 To realize second order
filter 119868Bias7 is set to value of 119868Bias4 such that 1198927is equal to 119892
4
and 119868Bias6 is set to value such that 1198926 is equal to sum of 1198923and
1198924 that is 119892
6= 1198923+ 1198924 Consider
119860 =1198924
1198923
(34)
which can be adjusted by varying 119868Bias3 and 119868Bias2 therebymaking 119891
0119860tunable
Advances in Electronics 7
IBias1
p
z zn
p
n
zczc
ILP
IBP
IIN
z998400 z998400c
I998400BP
VDTA VDTAg1 g2 g3 g4 g5
C1
C2
x+
xminus
x+
xminus
IBias3 IBias4 IBias5IBias2
Figure 13 VDTA based Class 1 FAF
IBias1
p
zz zn
p
n
p
nzczc zc
IBP
IIN
z998400 z998400c
I998400BP
ILP
VDTAg1 g2 g3
VDTAg4 g5
VDTAg6 g7
C1
C2
1g3
x+
xminus
x+
xminus
x+
xminus
IBias3 IBias4 IBias5 IBias6 IBias7IBias2
Figure 14 VDTA based Class 2 FAF
01
025 05
10
20
30
50
100
150
200
300
0
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
0495MHz
15MHz
245MHz
323MHz
IBias =
IBias =
IBias =IBias =
1120583A10120583A
30120583A60120583A
Figure 15 Frequency response of CDTA based Class 0 FAF with119868Bias1 = 119868Bias2 = 119868Bias
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (35) and (36) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (35)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (36)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (37) and (38) respectively
1198910119860
=1
2120587radic11989211198923
11986211198622
(1 +1198924
1198923
) (37)
119876119860=
1
1198922
radic119892111989231198621
1198622
(1 +1198924
1198923
) (38)
5 Nonideal Analysis
In this section nonideal analysis of CDTA and VDTA basedClass 0 FAF is presented
51 Nonideal Analysis of Class 0 CDTA Based FAF In prac-tice the transfer functions (9) and (10) modify due to non-idealities which are classified as tracking errors and parasitesThe tracking errors cause current transfer from 119901 and 119899 portsto 119911 port to differ from unity value and are represented by 120572
119901
and 120572119899 There is deviation in transconductance transfer from
119911 to 119909+ and 119909minus ports which is modeled by 120573119892119881119911The parasites
denoted by resistances 119877119901and 119877
119899are at 119901 and 119899 terminals
shunt output impedances (119877119862) are present at terminals 119911119911119888 119909+ and 119909
minus and 119909+
119888and 119909
minus
119888 The effect of the parasites
is highly dependent on the topology A close inspection ofthe circuit of Figure 6 shows that the parasitic capacitances
8 Advances in Electronics
05 10 20 30 50 70 100 200 3000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
121MHz
363MHz
575MHz
741MHz
IBias =
IBias =
IBias =
IBias =1120583A10120583A
30120583A60120583A
Figure 16 Frequency response of CDTA based Class 1 FAF with119868Bias1 = 119868Bias2 = 119868Bias
05 10 20 30 50 70 100 200 300 5000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
158MHz
485MHz
78MHz
995MHz
IBias =
IBias =
IBias =
IBias =10120583A30120583A60120583A
1120583A
Figure 17 Frequency response of CDTA based Class 2 FAF with119868Bias1 = 119868Bias2 = 119868Bias
present at 119911 terminal can be easily accommodated in externalcapacitances
Reanalysis of the proposed circuit (Figure 6) yields thefollowing nonideal transfer functions
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
119868Bias1 and 119868Bias3 whereas quality factor can be independentlycontrolled by 119868Bias2
1198910=
1
2120587radic11989211198923
11986211198622
119876 =1
1198922
radic119892111989231198621
1198622
(28)
42 VDTA Based Class 1 FAF The VDTA based Class 1 FAFis shown in Figure 13 It employs two VDTA blocks and twogrounded capacitors The second VDTA block is used asamplifier with tunable gain 119860 The gain 119860 of VDTA basedamplifier is given by
119860 =1198924
1198923
(29)
and can be adjusted by varying 119868Bias3 and 119868Bias4
The low pass and band pass transfer functions of VDTAbased Class 1 FAF are given by (30) and (31) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (30)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923)) (31)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (32) and (33) respectivelyThe center frequency can be independently controlled byvarying 119868Bias2 without changing center frequency
1198910119860
=1
2120587radic11989211198923
11986211198622
(radic1 +1198924
1198923
) (32)
119876119860=
1
1198922
radic119892111989231198621
1198622
(radic1 +1198924
1198923
) (33)
43 VDTA Based Class 2 FAF The VDTA based Class 2FAF is shown in Figure 14 which employs three VDTAstwo grounded capacitors and one grounded resistor Thesecond VDTA block is used as amplifier with tunable gain 119860The gain 119860 of VDTA based amplifier is given by (34) Theproposed filter uses grounded resistor which can easily beimplemented using the TA with transconductance equal to1198923based structure given in Figure 9 To realize second order
filter 119868Bias7 is set to value of 119868Bias4 such that 1198927is equal to 119892
4
and 119868Bias6 is set to value such that 1198926 is equal to sum of 1198923and
1198924 that is 119892
6= 1198923+ 1198924 Consider
119860 =1198924
1198923
(34)
which can be adjusted by varying 119868Bias3 and 119868Bias2 therebymaking 119891
0119860tunable
Advances in Electronics 7
IBias1
p
z zn
p
n
zczc
ILP
IBP
IIN
z998400 z998400c
I998400BP
VDTA VDTAg1 g2 g3 g4 g5
C1
C2
x+
xminus
x+
xminus
IBias3 IBias4 IBias5IBias2
Figure 13 VDTA based Class 1 FAF
IBias1
p
zz zn
p
n
p
nzczc zc
IBP
IIN
z998400 z998400c
I998400BP
ILP
VDTAg1 g2 g3
VDTAg4 g5
VDTAg6 g7
C1
C2
1g3
x+
xminus
x+
xminus
x+
xminus
IBias3 IBias4 IBias5 IBias6 IBias7IBias2
Figure 14 VDTA based Class 2 FAF
01
025 05
10
20
30
50
100
150
200
300
0
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
0495MHz
15MHz
245MHz
323MHz
IBias =
IBias =
IBias =IBias =
1120583A10120583A
30120583A60120583A
Figure 15 Frequency response of CDTA based Class 0 FAF with119868Bias1 = 119868Bias2 = 119868Bias
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (35) and (36) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (35)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (36)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (37) and (38) respectively
1198910119860
=1
2120587radic11989211198923
11986211198622
(1 +1198924
1198923
) (37)
119876119860=
1
1198922
radic119892111989231198621
1198622
(1 +1198924
1198923
) (38)
5 Nonideal Analysis
In this section nonideal analysis of CDTA and VDTA basedClass 0 FAF is presented
51 Nonideal Analysis of Class 0 CDTA Based FAF In prac-tice the transfer functions (9) and (10) modify due to non-idealities which are classified as tracking errors and parasitesThe tracking errors cause current transfer from 119901 and 119899 portsto 119911 port to differ from unity value and are represented by 120572
119901
and 120572119899 There is deviation in transconductance transfer from
119911 to 119909+ and 119909minus ports which is modeled by 120573119892119881119911The parasites
denoted by resistances 119877119901and 119877
119899are at 119901 and 119899 terminals
shunt output impedances (119877119862) are present at terminals 119911119911119888 119909+ and 119909
minus and 119909+
119888and 119909
minus
119888 The effect of the parasites
is highly dependent on the topology A close inspection ofthe circuit of Figure 6 shows that the parasitic capacitances
8 Advances in Electronics
05 10 20 30 50 70 100 200 3000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
121MHz
363MHz
575MHz
741MHz
IBias =
IBias =
IBias =
IBias =1120583A10120583A
30120583A60120583A
Figure 16 Frequency response of CDTA based Class 1 FAF with119868Bias1 = 119868Bias2 = 119868Bias
05 10 20 30 50 70 100 200 300 5000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
158MHz
485MHz
78MHz
995MHz
IBias =
IBias =
IBias =
IBias =10120583A30120583A60120583A
1120583A
Figure 17 Frequency response of CDTA based Class 2 FAF with119868Bias1 = 119868Bias2 = 119868Bias
present at 119911 terminal can be easily accommodated in externalcapacitances
Reanalysis of the proposed circuit (Figure 6) yields thefollowing nonideal transfer functions
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
Figure 15 Frequency response of CDTA based Class 0 FAF with119868Bias1 = 119868Bias2 = 119868Bias
The low pass and band pass transfer functions of CDTAbased Class 1 FAF are given by (35) and (36) respectively
119868LP119868IN
=11989211198923
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (35)
119868BP119868IN
=11990411989211198622
119862111986221199042 + 119904119862
21198922+ 11989211198923(1 + (119892
41198923))2 (36)
The center frequency and quality factor of the CDTAbased Class 1 FAF are expressed by (37) and (38) respectively
1198910119860
=1
2120587radic11989211198923
11986211198622
(1 +1198924
1198923
) (37)
119876119860=
1
1198922
radic119892111989231198621
1198622
(1 +1198924
1198923
) (38)
5 Nonideal Analysis
In this section nonideal analysis of CDTA and VDTA basedClass 0 FAF is presented
51 Nonideal Analysis of Class 0 CDTA Based FAF In prac-tice the transfer functions (9) and (10) modify due to non-idealities which are classified as tracking errors and parasitesThe tracking errors cause current transfer from 119901 and 119899 portsto 119911 port to differ from unity value and are represented by 120572
119901
and 120572119899 There is deviation in transconductance transfer from
119911 to 119909+ and 119909minus ports which is modeled by 120573119892119881119911The parasites
denoted by resistances 119877119901and 119877
119899are at 119901 and 119899 terminals
shunt output impedances (119877119862) are present at terminals 119911119911119888 119909+ and 119909
minus and 119909+
119888and 119909
minus
119888 The effect of the parasites
is highly dependent on the topology A close inspection ofthe circuit of Figure 6 shows that the parasitic capacitances
8 Advances in Electronics
05 10 20 30 50 70 100 200 3000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
121MHz
363MHz
575MHz
741MHz
IBias =
IBias =
IBias =
IBias =1120583A10120583A
30120583A60120583A
Figure 16 Frequency response of CDTA based Class 1 FAF with119868Bias1 = 119868Bias2 = 119868Bias
05 10 20 30 50 70 100 200 300 5000
2
4
6
8
10
12
14
16
18
Frequency (MHz)
Gai
n
158MHz
485MHz
78MHz
995MHz
IBias =
IBias =
IBias =
IBias =10120583A30120583A60120583A
1120583A
Figure 17 Frequency response of CDTA based Class 2 FAF with119868Bias1 = 119868Bias2 = 119868Bias
present at 119911 terminal can be easily accommodated in externalcapacitances
Reanalysis of the proposed circuit (Figure 6) yields thefollowing nonideal transfer functions
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
It is clear that the transfer functions and filter parameters((40a) (40b) and (41a) (41b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
01 02 03 05 10 20 30 50 1000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
0650MHz
1160MHz
1820MHz
2454MHz
IBias =
IBias =
IBias =IBias =
5120583A10120583A
30120583A60120583A
Figure 22 Frequency response of VDTA based Class 1 FAF with119868Bias1 = 119868Bias3 = 119868Bias
52 Nonideal Analysis of Class 0 VDTA Based FAF Con-sidering the nonideal characteristics of the VDTA the portrelations of current and voltage in (25) can be rewritten as
[[[[[[[
[
119868119911
119868119911119888
1198681015840
119911
1198681015840
119911119888
119868119909+
119868119909minus
]]]]]]]
]
=
[[[[[[[
[
1205731198921
minus1205731198921
0
minus1205731198921
1205731198921
0
1205731198922
minus1205731198922
0
minus1205731198922
1205731198922
0
0 0 1205731198923
0 0 minus1205731198923
]]]]]]]
]
[
[
119881119901
119881119899
119881119911
]
]
(42)
where 120573 represents the tracking error Apart from trackingerror the parasites appear as shunt impedances (119877119862) at
10 Advances in Electronics
05 10 20 30 50 100 2000
05
1
15
2
25
3
35
4
Frequency (MHz)
Gai
n
1125MHz2239MHz
417MHz
5625MHz
IBias =
IBias =
IBias =
IBias =5120583A10120583A
30120583A60120583A
Figure 23 Frequency response of VDTA based Class 2 FAF with119868Bias1 = 119868Bias3 = 119868Bias
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
Figure 26 ((a) and (c)) Input and its frequency spectrum ((b) and (d)) Output and its frequency spectrum for Class 0 FAF
5 10 15 20 25 30 35 40 45 50 55 60120
125
130
135
140
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 27 SNR of CDTA based FAF
And the filter parameters are calculated as
1198910=
1
2120587radic
120573211989211198923
1198621eq1198622eq
(47a)
119876 =1
1198922
radic119892111989231198622eq
1198621eq
(47b)
It is clear that the transfer functions and filter parameters((46a) (46b) and (47a) (47b)) deviate from the ideal valuein presence of nonidealities The change can however beaccommodated by adjusting bias currents
1 5 10 15 20 25 30 35 40 45 50 55 60
165
170
175
180
185
SNR
(dB)
Class 0 FAFClass 1 FAFClass 2 FAF
IBias1 = IBias2 = IBias (120583A)
Figure 28 SNR of VDTA based FAF
6 Simulation Results
In this section the functionality of the proposed filters hasbeen verified The SPICE simulations results for CDTA andVDTAbased filters have been presented usingTSMC025 120583mCMOS process model parameters and supply voltages of119881DD = minus119881SS = 18V
61 Simulation of CDTA Based FAF The CMOS schematicof Figure 5 is used for verifying CDTA based FAF and theaspect ratios of the MOS transistors are given in Table 1The additional TA blocks in CDTA providing current ports(119909+119862 119909minus119862 119909+119888119888 and 119909
minus
119888119888) use aspect ratios same as that for 119909+
and 119909minus The capacitors 1198621and 119862
2are chosen as 50 pF each
12 Advances in Electronics
Table 1 Aspect ratios of MOS transistors used in CDTA
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
The grounded resistor of Figure 7 is realized using TA blockThe bias current is set as 085 120583A to realize a resistor of value10 kΩThe frequency responses of CDTA based Class 0 Class1 and Class 2 FAF topologies are depicted in Figures 15 16and 17 respectively The responses are obtained by varyingbias currents 119868Bias1 and 119868Bias2 (119868Bias = 119868Bias1 = 119868Bias2) to1 120583A 10 120583A 30 120583A and 60 120583A while keeping 119868Bias3 and 119868Bias4respectively at 05 120583A and 10 120583A It can be clearly noticed thatcenter frequency 119891
0increases on increasing the bias current
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 CDTAbased FAF is plotted in Figures 18 and 19 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 18 for different values of119868Bias3 while setting 119868Bias1 and 119868Bias2 to 30 120583A Figure 19 depictsthe analytical and simulated responses for center frequencyvariation for different values of 119868Bias1 and 119868Bias2 (119868Bias1 = 119868Bias2)while setting 119868Bias3 to 05 120583A To plot responses for Class 1 andClass 2 CDTA based FAF the bias current 119868Bias4 is taken as10 120583A
The transient behaviour of proposed CDTA based FAF isalso studied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 and 119868Bias2 each to 10 120583A and 119868Bias3 to 05 120583AFigure 20 shows the input and output waveforms along withtheir frequency spectrum for CDTA based Class 0 FAF Itmay clearly be noted that the CDTA based Class 0 FAFallows only 1MHz signal to pass and significantly attenuatessignals of frequencies 100KHz 500KHz and 10MHz Similarresponses for Class 1 and Class 2 FAF were also obtained
62 Simulation of VDTA Based FAF The CMOS schematicof Figure 12 is used for verifying VDTA based FAF and theaspect ratios of the MOS transistors are given in Table 2The capacitors 119862
1and 119862
2are taken as 50 pF each In the real-
ization of Class 2 FAF the grounded resistor is implementedby TA block The frequency responses of VDTA based Class0 Class 1 and Class 2 FAF topologies are shown in Figures21 22 and 23 respectively The responses are obtained bykeeping 119868Bias2 to 5 120583A and setting bias currents 119868Bias1 and 119868Bias3(119868Bias = 119868Bias1 = 119868Bias3) to 5 120583A 10 120583A 30 120583A and 60120583A In
Table 2 Aspect ratios of MOS transistors used in VDTA
realization of Class 1 FAF 119868Bias4 is set to obtain 11989241198923 = 3 whilekeeping 119868Bias5 equal to 119868Bias1 In realization of Class 2 FAF 119868Bias6is selected such that 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
The electronic tunability of quality factor and centerfrequency for proposed Class 0 Class 1 and Class 2 VDTAbased FAF is plotted in Figures 24 and 25 respectively Theanalytical and simulated responses describing variation ofquality factor are shown in Figure 24 for different values of119868Bias2 while setting 119868Bias1 and 119868Bias3 to 30 120583A in Class 0 To plotresponses forClass 1 119868Bias4 is set to get11989241198923 =3 and 119868Bias5 is setequal to 119868Bias1 Class 2 FAF responses are plotted by selecting119868Bias6 to obtain 119892
6= 1198923+ 1198924while 119868Bias7 is equal to 119868Bias4
Figure 25 depicts the analytical and simulated responses forcenter frequency variation for different values of 119868Bias1 and119868Bias3 (119868Bias1 = 119868Bias3) and keeping 119868Bias2 to 5 120583A To plotresponses for Class 1 119868Bias4 is set to a value in such a mannerthat 119892
41198923= 3 whereas 119868Bias5 is set equal to 119868Bias1 The Class 2
FAF responses are plotted by setting 119868Bias6 to value such that1198926= 1198923+ 1198924whereas 119868Bias7 is equal to 119868Bias4
The transient behaviour of proposed agile filter is alsostudied by applying input signals of frequencies 100KHz500KHz 1MHz and 10MHz each having an amplitude of10 120583A The responses for Class 0 FAF are obtained by settingbias currents 119868Bias1 119868Bias2 and 119868Bias3 each to 30 120583A The inputand output waveforms along with their frequency spectrumfor VDTA based Class 0 FAF are shown in Figure 26 It mayclearly be noted that the VDTA based Class 0 FAF allows only1MHz signal to pass partially attenuates signal of frequency500KHz and significantly attenuates signals of frequencies100KHz and 10MHz Similar responses for Class 1 and Class2 FAF are also obtained
7 Performance Evaluation
The performance of proposed CDTA and VDTA based FAFcircuits is studied in terms of power dissipation output noisevoltage and SNRThe overall performance characteristics aresummarized in Table 3 Figures 27 and 28 depict the signal tonoise ratio (SNR) for the proposed CDTA and VDTA basedfilter topologies for Class 0 Class 1 and Class 2 respectivelyThe VDTA based FAF proved to be optimum concerning thepower dissipation and signal to noise ratio The maximumoutput noise voltage is better in VDTA based FAF
8 Conclusion
In this paper CDTA and VDTA based frequency agile filtersare presented The proposed FAF configurations employ
Advances in Electronics 13
Table3Perfo
rmance
characteris
ticso
fCDTA
andVDTA
basedClass0
Class1andClass2
FAF
Perfo
rmance
characteris
tics
Type
ofFA
F119868Bias=1120583
A119868Bias=10120583A
119868Bias=30
120583A
119868Bias=60
120583A
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Class0
Class1
Class2
Power
dissipation(m
W)
CDTA
0359
0997
163
334
399
463
998
107
113
199
206
212
VDTA
0089
0177
040
5032
119
345
0835
334
957
160
628
174
SNR(dB)
CDTA
1249
1221
1192
1355
1342
1313
1402
1379
1353
1421
1395
1372
VDTA
17582
1704
1650
1817
1805
17096
1820
1793
1716
1820
1797
51732
Maxoutpu
tnoise
voltage
(nV)
CDTA
7937
7492
7549
15502
8299
5897
21046
7069
4085
29059
6056
3192
VDTA
285
2885
281
3892
3743
513
4610
444
381
5162
5263
256
14 Advances in Electronics
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
grounded passive components and are suitable for integra-tion The filter configurations are designed in such a waythat quality factor can be independently controlled withoutchanging the center frequency The simulation results areincluded to demonstrate the workability of the circuits Theperformance of the proposed FAF is evaluated in terms ofpower dissipation SNR and noise performance The VDTAbased FAF proved to be optimum concerning the powerdissipation and signal to noise ratio
Conflict of Interests
The authors declare that there is no conflict of interestsregarding the publication of this paper
References
[1] P I Mak U Seng-Pan and R P Martins Analog-BasebandArchitecture and Circuits for Multistandard and Low VoltageWireless Transceivers Analog Integrated Circuits and SignalProcessing 2007
[2] Y Lakys and A Fabre ldquoMultistandard transceivers state ofthe art and a new versatile implementation for fully activefrequency agile filtersrdquo Analog Integrated Circuits and SignalProcessing vol 74 no 1 pp 63ndash78 2013
[3] Y Lakys and A Fabre ldquoA fully active frequency agile filter formultistandard transceiversrdquo in Proceedings of the InternationalConference on Applied Electronics (AE rsquo11) pp 1ndash7 September2011
[4] S Kaehlert D Bormann T D Werth M-D Wei L Liao andS Heinen ldquoDesign of frequency agile filters in RF frontend cir-cuitsrdquo in Proceedings of the IEEE Radio andWireless Symposium(RWS 12) pp 13ndash16 Santa Clara Calif USA January 2012
[5] A J X Chen YWu J Hodiak and P K L Yu ldquoFrequency agiledigitally tunablemicrowave photonic filterrdquo inProceedings of theInternational Topical Meeting on Microwave Photonics (MWP03) pp 89ndash92 September 2003
[6] G Subramanyam F W van Keuls and F A Miranda ldquoA K-band-frequency agile microstrip bandpass filter using a thin-film htsferroelectricdielectric multilayer configurationrdquo IEEETransactions on Microwave Theory and Techniques vol 48 no4 pp 525ndash530 2000
[7] H Chandrahalim S A Bhave R G Polcawich J Pulskampand R Kaul ldquoA Pb(Zr
055Ti045
) O3-transduced fully differential
mechanically coupled frequency agile filterrdquo IEEE ElectronDevice Letters vol 30 no 12 pp 1296ndash1298 2009
[8] M W Wyville R C Smiley and J S Wight ldquoFrequency agileRF filter for interference attenuationrdquo in Proceedings of the 6thIEEE Radio and Wireless Week (RWW rsquo12) pp 399ndash402 SantaClara Calif USA January 2012
[9] H H Sigmarsson J Lee D Peroulis and W J Chap-pell ldquoReconfigurable-order bandpass filter for frequency agilesystemsrdquo in Proceedings of the IEEE MTT-S InternationalMicrowave Symposium (MTT rsquo10) pp 1756ndash1759 AnaheimCalif USA May 2010
[10] Y Lakys B Godara and A Fabre ldquoCognitive and encryptedcommunications part 2 a new approach to active frequency-agile filters and validation results for an agile bandpass topologyin SiGe-BiCMOSrdquo in Proceedings of the 6th International Con-ference on Electrical and Electronics Engineering (ELECO rsquo09)pp II16ndashII29 November 2009
[11] V Biolkova and D Biolek ldquoShadow filters for orthogonal modi-fication of characteristic frequency and bandwidthrdquo ElectronicsLetters vol 46 no 12 pp 830ndash831 2010
[12] Y Lakys and A Fabre ldquoShadow filtersmdashnew family of second-order filtersrdquo Electronics Letters vol 46 no 4 pp 276ndash277 2010
[13] D Biolek ldquoCDTA-building block for current-mode analogsignal processingrdquo in Proceedings of the European Conference onCircuit Theory and Design (ECCTD rsquo03) vol III pp 397ndash400Krakow Poland 2003
[14] D Biolek V Biolkova and Z Kolka ldquoCurrent-mode biquademploying single CDTArdquo Indian Journal of Pure and AppliedPhysics vol 47 no 7 pp 535ndash537 2009
[15] M Kumngern P Phatsornsiri and K Dejhan ldquoFour inputs andone output current-modemultifunction filter usingCDTAs andall-grounded passive componentsrdquo in Proceedings of the 10thInternational Conference on ICT and Knowledge EngineeringICT and Knowledge Engineering pp 59ndash62 BangkokThailandNovember 2012
[16] S K Pandey A P Singh M Kumar S Dubey and P TyagildquoA current mode second order filter using dual output CDTArdquoInternational Journal of Computer Science amp CommunicationNetworks pp 210ndash213 2012
[17] F Kacar and H Kuntman ldquoA new cmos current differencingtransconductance amplifier (CDTA) and its biquad filter appli-cationrdquo inProceedings of the IEEE (EUROCON rsquo09) pp 189ndash196St Petersburg Russia May 2009
[18] D Biolek E Hancioglu and A U Keskin ldquoHigh-performancecurrent differencing transconductance amplifier and its appli-cation in precision current-mode rectificationrdquo InternationalJournal of Electronics and Communications vol 62 no 2 pp92ndash96 2008
[19] A Uygur H Kuntman and A Zeki ldquoMulti-input multi-output CDTA-based KHN filterrdquo in Proceedings of the IEEEInternationalMicrowave SymposiumDigest pp 1756ndash1759 2010
[20] W Chiu S I Liu H W Tsao and J J Chen ldquoCMOSdifferential difference current conveyor and their applicationsrdquoIEE Proceedings-Circuits Devices Systems vol 143 no 2 pp 91ndash96 1996
[21] Z Wang ldquo2-MOSFET transresistor with extremely low distor-tion for output reaching supply voltagesrdquo Electronics Letters vol26 no 13 pp 951ndash952 1990
[22] D Biolek M Shaktour V Biolkova and Z Kolka ldquoCurrent-input current-output universal biquad employing two bulk-driven VDTAsrdquo in Proceedings of the 4th International Congresson Ultra Modern Telecommunications and Control Systems(ICUMT rsquo12) pp 484ndash489 St Petersburg Russia October 2012
[23] J Satansupa and W Tangsrirata ldquoSingle VDTA based currentmode electronically tunable multifunction filterrdquo in Proceedingsof the 4th International Science Social Science Engineering andEnergy Conference (ISEEC 12) pp 1ndash8 2012
[24] P Phatsornsiri P Lamun M Kumngern and U TorteanchaildquoCurrent-mode third-order quadrature oscillator using VDTAsand grounded capacitorsrdquo in Proceedings of the 4th JointInternational Conference on Information and CommunicationTechnology Electronic and Electrical Engineering (JICTEE rsquo14)pp 1ndash4 IEEE Chiang Rai Thailand March 2014
[25] T Pourak P Suwanjan W Jaikla and S Maneewan ldquoSimplequadrature sinusoidal oscillator with orthogonal control usingsingle active elementrdquo in Proceedings of the International Con-ference on Signal Processing and Integrated Networks (SPIN 14)pp 1ndash4 2014
Advances in Electronics 15
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
[26] M Srivastava D Prasad and D R Bhaskar ldquoNew ParallelR-L impedance using single VDTA and its high pass filterapplicationrdquo in Proceedings of the International Conference onSignal Processing and Integrated Networks (SPIN rsquo14) pp 535ndash537 2014
[27] K Chumwangwapee W Jaikla W Sunthonkanokpong WJaikhang S Maneewan and B Sreewirote ldquoHigh inputimpedance mixed-mode biquad filter with orthogonal tune ofnatural frequency and quality factorrdquo in Proceedings of the 4thJoint International Conference on Information and Communica-tion Technology Electronic and Electrical Engineering (JICTEErsquo14) pp 1ndash4 Chiang Rai Thailand March 2014
