ADS LNA simulation example
ADS documentation
• Apart from the handed-out ADS tour: a lot more info on ADS and simulation tricks, know-how on http://www.agilent.com
Project data
• Project name: LNA_PRJ• Technology: CMOS 0.25 um (included via netlist
statement)• Number of networks: 9 (plus one sub-network)
• Description: Shows how to simulate all important specifications of a (common-source cascode) LNA. Output matching is not done, because after the LNA no external (50 Ohm) filter is anticipated: hence no need for matching (which cost 3 dB in gain)
Simulation of MOS characteristics
Set gate and drain voltage sweep limits as needed. If the transistor instance name changes (for example, MOSFET2 instead of MOSFET1), then the MOS_Gm equation must also be changed. If a library part is used on this schematic, then the MOS_Gm equation will have to be set to something like A1.Device.Gm.
FET Curve Tracer
MOSFET_NMOSMOSFET1
Width=100 umLength=0.25 umModel=nfet
DCDC1
Other=Step=0.1Stop=2.5Start=0SweepVar="VDS"
DCParamSweepSweep1
Step=0.1Stop=1.4Start=0SimInstanceName[6]=SimInstanceName[5]=SimInstanceName[4]=SimInstanceName[3]=SimInstanceName[2]=SimInstanceName[1]="DC1"SweepVar="VGS"
PARAMETER SWEEP
MeasEqnMeas1MOS_Gm=MOSFET1.Gm
EqnMeas
NetlistIncludeNetlistInclude1IncludeFiles[1]=generic025.lib
NETLIST INCLUDE
VARVAR1
VDS=0VGS=0
EqnVar
V_DCSRC1Vdc=VDS
V_DCSRC3Vdc=VGS
I_ProbeIDS
Schematic: FET_curve_tracer
Example of simulation output
m 1VDS=IDS.i=0.010VGS=0.900000
1.000m 1VDS=IDS.i=0.010VGS=0.900000
1.000
0.5 1.0 1.5 2.00.0 2.5
5
10
15
20
25
30
35
0
40
VGS=0.000VGS=0.100VGS=0.200VGS=0.300VGS=0.400VGS=0.500VGS=0.600VGS=0.700
VGS=0.800
VGS=0.900
VGS=1.000
VGS=1.100
VGS=1.200
VGS=1.300
VGS=1.400
VDS
IDS
.i, m
A
m 1
Device I-V Curves
m 2VDS=MOS_Gm =0.003VGS=0.500000
2.300m 2VDS=MOS_Gm =0.003VGS=0.500000
2.300
0.5 1.0 1.5 2.00.0 2.5
0.000
0.005
0.010
0.015
0.020
0.025
0.030
-0.005
0.035
VGS=0.000VGS=0.100VGS=0.200VGS=0.300VGS=0.400VGS=0.500
VGS=0.600
VGS=0.700
VGS=0.800
VGS=0.900VGS=1.000VGS=1.100VGS=1.200VGS=1.300VGS=1.400
VDS
MO
S_G
m
m 2
DC Transconducta nce ve rsus VDS
DC transfer curves to determine proper biasing voltage Vgs
DC and S-parameter simulation
Vdra in
Vga te
The S pa ra me te rs a re s imula te d to c he c k ga ina nd s ta bility.
I_P robeID
Te rmTe rm2
Z=300 OhmNum=2 V_DC
S RC1Vdc =2.5 V
V_DCS RC2Vdc =0.75 V
MOSFET_NMOSMOSFET1
Trise=Width=100 umLength=.25 umModel=nfet
MuP rimemup1mu_loa d=mu_prime (S )
MuP
rime
Mumu1mu_s ourc e =mu(S )
Mu
DCDC1
DC
Ne tlis tInc ludeNe tlis tInc lude 1Inc lude File s [1]=ge ne ric 025.lib
NETLIST INCLUDE
DC_Fe e dDC_Fe e d1
S _P a ra mS P 1
S te p=10 MHzS top=3.0 GHzS ta rt=10 MHz
S-PARAMETERSDC_Bloc kDCBloc k1
Te rmTe rm1
Z=50 OhmNum=1
Schematic: DC_and_Sparams
Port-impedance: “term” for Sparam simulation
Port-impedance: “term” for Sparam simulation
Stabilitymeasures
Example of simulation output
freq0.000 Hz
Vgate750.mV
Vdra in1.19 V
freq0.000 Hz
ID.i4.35mA Dc conditions
m2fre q=dB(S (2,1))=8.982
2.000GHzm2fre q=dB(S (2,1))=8.982
2.000GHz
0.5 1.0 1.5 2.0 2.50.0 3.0
-40
-20
0
-60
20
freq, GHz
dB(S
(1,2
))dB
(S(2
,1))
m2
freq (10.00MHz to 3.000GHz)
S(1
,1)
S(2
,2)
S-parameters
Target for S11: 50 Ohm
gain
Reverse-isolation
DC and S-parameter simulation: cascode LNA
Vg a te
Vin
Vdra in
Vout
T he S pa ra m e te r s a r e s im ula te d to c he c k g a ina nd s ta b ility.D A_S m ithC ha r tM a tc h1_D C _a nd_S pa r a m s _c a s c a de
D A_S m ithC ha r tM a tc h1
Z 0= 50 O hmZ l= (50 .00- j*127.5) O hmZ s = 50 O hmF = 1.9 G H z
S _P a ra mS P 1
S te p= 10 M H zS top= 3 .0 G H zS ta r t= 10 M H z
S -P A R A M E T E R S
M uP r im em up1m u_loa d= m u_pr im e (S )
MuP
rime
D CD C 1
D C
M um u1m u_s our c e = m u( S )
Mu
I_P robeID
LL1
R =L= 1.05 nH
T e r mT e r m 2
Z = 100 O hmN um = 2
M e a s E q nM e a s 1Vds _c a s c a de = Vout- Vdra in
Eq nMe a s
D C _Bloc kD C Bloc k1
T e rmT e rm 1
Z = 50 O hmN um = 1
V_D CS R C 2Vdc = 0.75 V
MO S F E T _ N MO SMO S F E T 2
T ris e =W id th =1 0 0 u mLe n g th = 0 .2 5 u mMo d e l=n fe t
MO S F E T _ N MO SMO S F E T 1
T ris e =W id th = 1 0 0 u mLe n g th = 0 .2 5 u mMo d e l= n fe t
V_D CS R C 3Vdc = 1.8 V
V_D CS R C 1Vdc = 2.5 V
D C _F e e dD C _F e e d1
N e tlis tInc ludeN e tlis tInc lude 1Inc lude F ile s [1 ]= g e ne r ic 025 .lib
N E T L IS T IN C LU D E
Smith –chart component first disabled and shorted to see un-matched S11
Cascode LNA for improved stability and isolation and less miller effect
Schematic: DC_and_Sparams_cascode
Example of simulation output
m3freq=S(1,1)=0.793 / -37.940impedance = Z0 * (0.983 - j2.579)
1.900GHz
freq (10.00MHz to 3.000GHz)
S(1
,1)
m3S
(2,2
)
Coil in source has right value, but inductive matching network needed
m2freq=dB(S(2,1))=9.109
2.000GHz
0.5 1.0 1.5 2.0 2.50.0 3.0
-80
-60
-40
-20
0
-100
20
freq, GHz
dB(S
(1,2
))dB
(S(2
,1))
m2
Improved isolation due to cascode stage (and thus stability)
DC and S-parameter simulation: cascode LNA
• Same schematic but smith-chart component enabled
Vgate
Vin
Vdrain
Vout
The S parameters are s imulated to check gainand s tability.DA_SmithChartMatch_DC_and_Sparams_cascode
DA_SmithChartMatch1
Z0=50 OhmZl=(50+j*0) OhmZs=(50+j*0) OhmF=1 GHz
S_ParamSP1
Step=10 MHzStop=3.0 GHzStart=10 MHz
S -P ARAMETERS
MuPrimemup1mu_load=mu_prime(S)
MuP
rime
DCDC1
DC
Mumu1mu_source=mu(S)
Mu
I_ProbeID
LL1
R=L=1.05 nH
TermTerm2
Z=100 OhmNum=2
MeasEqnMeas1Vds_cascade=Vout-Vdrain
E qnMeas
DC_BlockDCBlock1
TermTerm1
Z=50 OhmNum=1
V_DCSRC2Vdc=0.75 V
MOSFET_NMOSMOSFET2
Tris e =Width=100 umLe ngth=0.25 umMode l=nfe t
MOSFET_NMOSMOSFET1
Tris e =Width=100 umLe ngth=0.25 umMode l=nfe t
V_DCSRC3Vdc=1.8 V
V_DCSRC1Vdc=2.5 V
DC_FeedDC_Feed1
Netlis tIncludeNetlis tInclude1IncludeFiles[1]=generic025.lib
NETLIS T INCLUDE
Schematic: DC_and_Sparams_cascode
Use design guide to match input (I)
• In schematic, ADS Menu: DesignGuide→filter→smith chart control window
Set frequency at 1.9 GHzunmark: normalized impedances
Click On Zl
Fill in S11impedance
Use design guide to match input (II)
S1149.1-j128.95
After entry, press enter
Use design guide to match input (III)
Select series inductance
Move around smith chart until matched
Last step: build ADS circuit
Click on this button
Lumped Element Low P as s Filter Des ign As s is tantNeed Help? P leas e s ee the appropriate Des ignGuide Us er Manual
P ortP 2Num=2
LL1
R=1e-12 OhmL=10.756248 nH
P ortP 1Num=1
VARVAR1P arameters ="#1.9 GHz#50 Ohm#(49.10-j*128.9) Ohm#50 Ohm"
EqnVar
Automatically creates this sub-network
Repeat simulation of schematic:DC_and_Sparams_cascode
m2freq=dB(S(2,1))=13.063
2.000GHz
0.5 1.0 1.5 2.0 2.50.0 3.0
-80
-60
-40
-20
0
-100
20
freq, GHz
dB(S
(1,2
))dB
(S(2
,1))
m2
m3freq=S(1,1)=0.010 / -148.430impedance = Z0 * (0.983 - j0.010)
1.900GHz
freq (10.00MHz to 3.000GHz)
S(1
,1) m3
S(2
,2)
Improved gain (4 dB) and minimum return loss due to input matching.
DC and S-parameter simulation: cascode LNA
• Same schematic as previous schematic but with smith chart component replaced by coil (~ 10 nH)
Vgate
Vin
Vdra in
Vout
The S parameters a re s imulated to check ga inand s tability .
LL2
R=L=10.6 nH
S_ParamSP1
Step=10 MHzStop=3.0 GHzStart=10 MHz
S -P ARAMETERS
Mumu1mu_s ource=mu(S)
Mu
Netlis tIncludeNetlis tInclude1Inc ludeFiles [1]=generic025.lib
NETLIS T INCLUDE
MuPrimemup1mu_load=mu_prime(S)
MuP
rime
DCDC1
DC
I_ProbeID
LL1
R=L=1.05 nH
TermTerm2
Z=100 OhmNum=2
Meas EqnMeas 1Vds _cas cade=Vout-Vdrain
EqnMe a s
DC_BlockDCBlock1
TermTerm1
Z=50 OhmNum=1
V_DCSRC2Vdc=0.75 V
MOS FET_NMOSMOS FET2
Tris e=Width=100 umLe ngth=0.25 umModel=nfe t
MOS FET_NMOSMOS FET1
Tris e =Width=100 umLe ngth=0.25 umMode l=nfe t
V_DCSRC3Vdc=1.8 V
V_DCSRC1Vdc=2.5 V
DC_FeedDC_Feed1
Schematic: DC_and_Sparams_cascode_match
AC simulation for noise figure
N o t ic e t h a t f o r t h is f irs tn o is e s im u la t io n t h e q u a lit yf a c t o r o f t h e t w o in d u c t o rsis in if it e (o n re a lis t ic : s e ef o r a m o re re a lis t ic n o is ef ig u re LN A _ n o is e _ re a l_ Q ).
V in V g a t e
V o u t
V d ra in
N e t lis t In c lu d eN e t lis t In c lu d e 1In c lu d e F ile s [1 ]= g e n e r ic 0 2 5 . lib
NETLIS T INC LUDE
LL1
R =L= 1 . 0 n H
LL2
R =L= 1 0 . n H
Te rmTe rm 2
Z = 1 0 0 O h mN u m = 2
M O S F E T _ N M O SM O S F E T 2
T r is e =W id th = 1 0 0 u mLe n g th = 0 .2 5 u mM o d e l= n fe t
A CA C 1
In c lu d e P o rt N o is e = y e sS o r t N o is e = S o r t b y v a lu eN o is e N o d e [2 ]= "V in "N o is e N o d e [1 ]= "V o u t "C a lc N o is e = y e sS t e p = 1 0 0 MH zS t o p = 3 G H zS t a rt = 1 0 0 MH zS w e e p V a r= "f re q "
A C
M O S F E T _ N M O SM O S F E T 1
T r is e =W id th = 1 0 0 u mLe n g th = 0 .2 5 u mM o d e l= n fe t
P _ A CP O R T1
F re q = f re qP a c = p o la r(d b m t o w (0 ), 0 )Z = 5 0 O h mN u m = 1
I_ P ro b eID
D C _ B lo c kD C B lo c k 1
V _ D CS R C 2V d c = 0 . 7 5 V
V _ D CS R C 3V d c = 1 . 8 V
V _ D CS R C 1V d c = 2 . 5 V
D C _ F e e dD C _ F e e d 1
Schematic: LNA_noise
Coils are ideal here: no losses included yet
Example of simulation output
Eqn NF=20*log((Vout.noise/(mag(Vout/Vin)))/PORT1.t1.v.noise)
Measurement equation used to calculated the noise figure
m1freq=NF=0.703
1.900GHz
0.5 1.0 1.5 2.0 2.50.0 3.0
1
2
3
4
0
5
freq, GHz
NF
m1
Noise figure versus frequency
AC simulation for noise figure with realistic coils
Both Induc tors nowhave a s e rie s re s is tormaking the qua lity fac torof the c ompone nt approx7
Vin Vga te
Vout
Vdra in
LL1
R=1.7L=1 nH
LL2
R=18L=10. nH
Ne tlis tInc ludeNe tlis tInc lude 1Inc ludeFile s [1]=gene ric025.lib
NETLIST INCLUDETermTerm2
Z=100 OhmNum=2
MOSFET_NMOSMOSFET2
Trise=Width=100 umLength=0.25 umModel=nfet
ACAC1
Inc ludeP ortNois e =ye sS ortNois e=S ort by va lueNois e Node[2]="Vin"Nois e Node[1]="Vout"Ca lcNois e=yesS te p=100 MHzS top=3 GHzS ta rt=100 MHzS weepVa r="fre q"
AC
MOSFET_NMOSMOSFET1
Trise=Width=100 umLength=0.25 umModel=nfet
P _ACP ORT1
Freq=freqP ac =pola r(dbmtow(0),0)Z=50 OhmNum=1
I_P robeID
DC_Bloc kDCBlock1
V_DCS RC2Vdc =0.75 V
V_DCS RC3Vdc =1.8 V
V_DCS RC1Vdc=2.5 V
DC_Fee dDC_Fee d1
Resistance in coils set to have a quality factor of about 7
Schematic: LNA_noise_real_Q
Example of simulation output
m1freq=NF=1.471
1.900GHzm1freq=NF=1.471
1.900GHz
0.5 1.0 1.5 2.0 2.50.0 3.0
2
3
4
1
5
fre q, GHz
NF
m1
Notice tha t the nois e figurehas degraded s ignificantlydue to the the rmal nois e of the s e rie s re s is tancesin the inductors
Example of sweeping a parameter
Vin Vga te
Vout
Vdra in
Netlis tInc ludeNetlis tInc lude1Inc ludeFile s [1]=gene ric025.lib
NETLIST INCLUDE
P aramS weepS weep1
S tep=0.5e-9S top=15e -9S ta rt=1e -9S imIns tanceName[6]=S imIns tanceName[5]=S imIns tanceName[4]=S imIns tanceName[3]=S imIns tanceName[2]=S imIns tanceName[1]="AC1"S weepVar="s ource ind"
PARAMETER SWEEPLL2
R=L=s ource ind
VARVAR1s ource ind=1e -9
E qnVar
LL1
R=L=1.0 nH
TermTerm2
Z=100 OhmNum=2
MOSFET_NMOSMOSFET2
Tris e =Width=100 umLe ngth=0.25 umMode l=nfe t
ACAC1
Inc ludeP ortNois e=yesS ortNois e=S ort by va lueNois eNode [2]="Vin"Nois eNode [1]="Vout"CalcNois e=yesS tep=100 MHzS top=3 GHzS ta rt=100 MHzS weepVar="freq"
AC
MOSFET_NMOSMOSFET1
Tris e =Width=100 umLe ngth=0.25 umMode l=nfe t
P _ACP ORT1
Freq=freqP ac=pola r(dbmtow(0),0)Z=50 OhmNum=1
I_P robeID
DC_BlockDCBlock1
V_DCS RC2Vdc=0.75 V
V_DCS RC3Vdc=1.8 V
V_DCS RC1Vdc=2.5 V
DC_FeedDC_Feed1 Parameter
sweep block included
Schematic: LNA_noise_sweep
Matching inductor is varied from 1 to 15 nH(coils have infinite Q)
Example of simulation output
m1freq=NF=0.669sourceind=1.100000E-8
1.900GHz
0.5 1.0 1.5 2.0 2.50.0 3.0
2
4
6
0
8
freq, GHz
NF
m1
Lg ~ 10.7 nH close to the optimum value
Gain and 1dB compression simulation
Vin Vg a te
Vou t
Vdra in
Me a s E q nMe a s 1Vo u t_ dBm =d Bm (Vou t[1 ])
Eq nMe a s
VARVAR 1R F _powe r=-3 5
Eq nVa r
H a rm o n ic Ba la nc eH B1
S te p =1S top =10S ta rt=-50S we e pVa r="R F _po we r"O rd e r[1 ]=3F re q [1 ]=1 .9 G H z
HAR MO NIC BALANCE
V_D CS R C 1Vdc =2 .5 V
V_D CS R C 3Vdc =1 .8 V
N e tlis tInc lud eN e tlis tInc lud e 1In c lude F ile s [1 ]=ge n e ric 0 25 . lib
NE T LIS T INCLUDE
P _1 ToneP O R T1
F re q=1 .9 G H zP =d bm tow(R F _p owe r)Z =5 0 O h mN um =1
LL1
R =1 .7L=1 nH
LL2
R =18L=1 0 . nH
Te rmTe rm 2
Z =1 00 O hmN um =2
MOS FE T _ NMOSMOS FE T 2
T ris e =W id th =1 0 0 u mLe n g th =0 .2 5 u mMo d e l=n fe t
MOS FE T _ NMOSMOS FE T 1
T ris e =W id th =1 0 0 u mLe n g th =0 .2 5 u mMo d e l=n fe t
I_ P robeID
D C _Bloc kD C Bloc k 1
V_D CS R C 2Vdc =0 .75 V D C _F e e d
D C _F e e d1
From sources-freq. domain: P_1 tone source.RF_power is the sweep variable
Schematic: LNA_1dB_by_power_sweep
Initialization by means of Var (main menu) needed
HBcontroller
Meas eq.
Example of simulation output
Equation defining the line
Eqn Line =RF_power+dB_ga in[0]
m4ind De lta =de p De lta =-1.025de lta mode ON
0.000
m3RF_powe r=Line =8.016
-7.000
m4ind De lta =de p De lta =-1.025de lta mode ON
0.000
m3RF_powe r=Line =8.016
-7.000
-40 -30 -20 -10 0-50 10
-30
-20
-10
0
10
20
-40
30
RF_power
Vou
t_dB
m
m4Li
ne
m3
m1RF_power=Vout_dBm=9.265
-4.000
-40 -30 -20 -10 0-50 10
-30
-20
-10
0
10
-40
20
RF_power
Vou
t_dB
m
m1
Voltage gain ~ 15 dB
Input power for 1 dB compression
Simulation of IIP3
Vin Vg a te
Vd ra in
O rd e r 4 me a n s th a t Fre q [1 ] w illb e c a lc u la te d w ith 4 h a rmo n ic s
O u tp u t IP3 (O IP3 )
1 5 is th e s ma ll s ig n a l p o w e rg a in in d B o f th e LN A, w h ic h is ta k e n fro mth e 1 d B c o mp re s s io n s imu la tio ns c h e ma tic .
In p u t IP3 (IIP3 )To c a lc u la te th e in p u t IP3th e g a in o f th e LN A is n e e d e d
Vo u t
VARVAR 1
R F_ p o w e r=-3 5R F_ fre q =1 .9 G H zs p a c in g =1 MH z
E q nVa r
P_ n To n ePO R T1
P[2 ]=d b mto w (R F_ p o w e r)P[1 ]=d b mto w (R F_ p o w e r)Fre q [2 ]=R F_ fre q - s p a c in g /2Fre q [1 ]=R F_ fre q + s p a c in g /2Z=5 0 O h mN u m=1
H a rmo n ic Ba la n c eH B1
O rd e r[2 ]=4O rd e r[1 ]=4Fre q [2 ]=R F_ fre q -s p a c in g /2Fre q [1 ]=R F_ fre q +s p a c in g /2
HARMO NIC BALANCE
IP3 o u tip o 2ip o _ lo w e r=ip 3 _ o u t(Vo u t,{1 ,0 },{-1 ,2 },5 0 )
P0
Pin
IP 3out
IP3 o u tip o 1ip o _ u p p e r=ip 3 _ o u t(Vo u t,{1 ,0 },{2 ,-1 },5 0 )
P0
Pin
IP 3out
IP3 inIP3 in 1IP3 in 1 =ip 3 _ in (Vo u t,1 5 ,{1 ,0 },{2 ,-1 },5 0 )
P0
Pin
IP 3in
N e tlis tIn c lu d eN e tlis tIn c lu d e 1In c lu d e File s [1 ]=g e n e r ic 0 2 5 .lib
NE TLIS T INCLUDE
Me a s Eq nMe a s 2to n e s =[{1 ,0 },{0 ,1 },{2 ,-1 },{-1 ,2 }]
E q nM e a s
LL1
R =1 .7L=1 n H
Me a s Eq nMe a s 1Vo u t_ d Bm=d Bm(Vo u t[1 ])
E q nM e a s
MOS FE T_NMOSMOS FE T1
Tris e=W idth=100 umLength=0.25 umModel=nfe tL
L2
R =1 8L=1 0 .6 n H
V_ D CSR C 1Vd c =2 .5 V
V_ D CSR C 3Vd c =1 .8 V
Te rmTe rm2
Z=1 0 0 O h mN u m=2
MOS FE T_NMOSMOS FE T2
Tris e=W idth=100 umLength=0.25 umModel=nfet
I_ Pro b eID
D C _ Blo c kD C Blo c k 1
V_ D CSR C 2Vd c =0 .7 5 V D C _ Fe e d
D C _ Fe e d 1
Schematic: LNA_IIP3
From sources-freq. domain: P_ntone source.Two tones are defined
Predefined equationsDef. of tones of interest
Mix –function in ADS
• Purpose: Returns a component of a spectrum based on a vector of mixing indices.
• Synopsis mix(xOut, harmIndex{, Mix}) – where – xOut is a voltage or a current spectrum. – harmIndex is the desired vector of harmonic frequency
indices (mixing terms). – Mix is a variable consisting of all possible vectors of
harmonic frequency indices (mixing terms) in the analysis.• Example: y = mix(vOut, {2, -1})
Example of simulation output
IP 3in11.333
ipo_lower16.332
ipo_upper16.333
Notice tha t the upper and lower third orde r inte rceptpoints a re a lmos t symmetrica l (ipo_uppe r and ipo_lower). The input IP 3 (IP 3in1) is s imply 15 dBlower (the small s igna l ga in) than the output IP 3
freq
0.0000 Hz1.000MHz2.000MHz1.898GHz1.899GHz1.901GHz1.902GHz3.798GHz3.799GHz3.800GHz3.801GHz3.802GHz5.698GHz5.699GHz5.700GHz5.702GHz7.598GHz7.599GHz7.600GHz7.601GHz7.602GHz
MixMix(1) Mix(2)
012
-1012
-10123012301234
0-1-2210
-13210
-1321043210
This is the so-ca lled mix table of the ha rmonic ba lance s imula tion. Number 1 represents the RF tone (with spacing). Zero means tha t notone is present (DC). And two represents two times the RF s imula tion tone (of Freq[1] or Freq[2]).
m1freq=dBm(mix(Vout,tones))=-19.934
1.899GHz
m2freq=dBm(mix(Vout,tones))=-19.939
1.901GHz
1.8990 1.8995 1.9000 1.9005 1.90101.8985 1.9015
-80
-60
-40
-20
-100
0
freq, GHz
dBm
(mix
(Vou
t,ton
es)) m1 m2