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70-MHz IF 10-MHz bandwidth bandpass RD modulator for WCDMA applications Herve ´ Caracciolo Edoardo Bonizzoni Piero Malcovati Franco Maloberti Received: 15 June 2011 / Revised: 23 September 2011 / Accepted: 24 September 2011 / Published online: 4 October 2011 Ó Springer Science+Business Media, LLC 2011 Abstract A MASH bandpass RD modulator for wide- band code division multiple access (WCDMA) applications is presented. The signal bandwidth of the proposed mod- ulator is 10 MHz centered around an intermediate fre- quency (IF) of 70.5 MHz. Two two-path second-order bandpass RD modulators make the MASH architecture, which realizes a noise transfer function with four couples of complex conjugate zeros. The proposed circuit, fabri- cated with a 0.18 lm CMOS technology, uses a sampling frequency of 180 MHz to obtain a resolution of about 12 bits in the 10 MHz bandwidth around the IF. The measured modulator power consumption is 95 mW with a supply voltage of 1.8 V. The achieved figure-of-merit (FoM BP ) is 0.37 pJ/conversion-level. Keywords Analog-to-digital conversion Sigma-delta modulation Bandpass 1 Introduction In modern communication systems, the direct conversion into the digital domain of a signal at an intermediate fre- quency (IF), typically in the range 40 100 MHz, is becoming quite popular. These communication standards foresee wide signal bandwidths (5 10 MHz) while requiring medium-high resolution (10–14 bits). High-res- olution Nyquist-rate analog-to-digital converters (ADCs) with sampling-rate embracing the IF interval consume significant power, thus making their use affordable only in base stations. For portable applications, solutions based on bandpass RD modulators, either with continuous-time and sampled-data implementations, are preferable because they reduce power consumption [19]. This paper describes the design of a bandpass RD modulator for wideband code division multiple access (WCDMA) applications. The considered signal bandwidth is 10 MHz centered around an IF equal to 70.5 MHz. The proposed bandpass RD modulator is based on a multi-stage noise shaping (MASH) architecture which realizes a noise transfer function (NTF) with four couples of complex conjugate zeros around the unity circle. The MASH structure consists of two second-order bandpass RD mod- ulators, each implemented with a two-path architecture and cross-coupled integrators. The two-path scheme allows reducing the power consumption and easily implements the desired NTF zeros. The RD modulator works with a sam- pling frequency (f s ) of 180 MHz, so that each path runs at f s /2 = 90 MHz. The proposed RD modulator, fabricated using a 0.18 lm CMOS technology, achieves a resolution of about 12 bits consuming 95 mW. The paper is organized as follows. Section 2 describes the modulator architecture while Section 3 presents the behavioral level study. Section 4 discusses the circuit H. Caracciolo E. Bonizzoni (&) F. Maloberti Department of Electronics, University of Pavia, Via Ferrata, 1, 27100 Pavia, Italy e-mail: [email protected] H. Caracciolo e-mail: [email protected] F. Maloberti e-mail: [email protected] P. Malcovati Department of Electrical Engineering, University of Pavia, Via Ferrata, 1, 27100 Pavia, Italy e-mail: [email protected] 123 Analog Integr Circ Sig Process (2012) 71:411–419 DOI 10.1007/s10470-011-9795-2
Transcript

70-MHz IF 10-MHz bandwidth bandpass RD modulatorfor WCDMA applications

Herve Caracciolo • Edoardo Bonizzoni •

Piero Malcovati • Franco Maloberti

Received: 15 June 2011 / Revised: 23 September 2011 / Accepted: 24 September 2011 / Published online: 4 October 2011

� Springer Science+Business Media, LLC 2011

Abstract A MASH bandpass RD modulator for wide-

band code division multiple access (WCDMA) applications

is presented. The signal bandwidth of the proposed mod-

ulator is 10 MHz centered around an intermediate fre-

quency (IF) of 70.5 MHz. Two two-path second-order

bandpass RD modulators make the MASH architecture,

which realizes a noise transfer function with four couples

of complex conjugate zeros. The proposed circuit, fabri-

cated with a 0.18 lm CMOS technology, uses a sampling

frequency of 180 MHz to obtain a resolution of about

12 bits in the 10 MHz bandwidth around the IF. The

measured modulator power consumption is 95 mW with a

supply voltage of 1.8 V. The achieved figure-of-merit

(FoMBP) is 0.37 pJ/conversion-level.

Keywords Analog-to-digital conversion � Sigma-delta

modulation � Bandpass

1 Introduction

In modern communication systems, the direct conversion

into the digital domain of a signal at an intermediate fre-

quency (IF), typically in the range 40� 100 MHz, is

becoming quite popular. These communication standards

foresee wide signal bandwidths (5� 10 MHz) while

requiring medium-high resolution (10–14 bits). High-res-

olution Nyquist-rate analog-to-digital converters (ADCs)

with sampling-rate embracing the IF interval consume

significant power, thus making their use affordable only in

base stations. For portable applications, solutions based on

bandpass RD modulators, either with continuous-time and

sampled-data implementations, are preferable because they

reduce power consumption [1–9].

This paper describes the design of a bandpass RDmodulator for wideband code division multiple access

(WCDMA) applications. The considered signal bandwidth

is 10 MHz centered around an IF equal to 70.5 MHz. The

proposed bandpass RD modulator is based on a multi-stage

noise shaping (MASH) architecture which realizes a noise

transfer function (NTF) with four couples of complex

conjugate zeros around the unity circle. The MASH

structure consists of two second-order bandpass RD mod-

ulators, each implemented with a two-path architecture and

cross-coupled integrators. The two-path scheme allows

reducing the power consumption and easily implements the

desired NTF zeros. The RD modulator works with a sam-

pling frequency (fs) of 180 MHz, so that each path runs at

fs/2 = 90 MHz. The proposed RD modulator, fabricated

using a 0.18 lm CMOS technology, achieves a resolution

of about 12 bits consuming 95 mW.

The paper is organized as follows. Section 2 describes

the modulator architecture while Section 3 presents the

behavioral level study. Section 4 discusses the circuit

H. Caracciolo � E. Bonizzoni (&) � F. Maloberti

Department of Electronics, University of Pavia, Via Ferrata, 1,

27100 Pavia, Italy

e-mail: [email protected]

H. Caracciolo

e-mail: [email protected]

F. Maloberti

e-mail: [email protected]

P. Malcovati

Department of Electrical Engineering, University of Pavia,

Via Ferrata, 1, 27100 Pavia, Italy

e-mail: [email protected]

123

Analog Integr Circ Sig Process (2012) 71:411–419

DOI 10.1007/s10470-011-9795-2

implementation details and Section 5 illustrates the mea-

surement results. Finally, Section 6 draws some conclusions.

2 Proposed bandpass RD modulator architecture

The proposed MASH architecture consists of two second-

order bandpass RD modulators. Each second-order modu-

lator gives rise to two couples of complex conjugate zeros

in the NTF.

2.1 Second-order bandpass RD Modulator

The NTF of second-order bandpass RD modulator with

complex zeros on the unity circle is

NTF ¼ 1þ a1z�1 þ z�2� �

1þ a2z�1 þ z�2� �

; ð1Þ

where a1,2 are real coefficients in the range �2; 2½ �: If a1 or

a2 are equal to 1, two zeros are at �1=2� jffiffiffi3p

=2: Other

values move the zeros toward that limit. Figure 1 shows the

zero placement for a1 = 12/8 and a2 = 15/8.

To achieve the desired in-band noise shaping, the pro-

posed second-order modulator uses resonators, as shown in

the block diagram of Fig. 2. In particular, we use two

resonators with transfer function equal to

Hi;j zð Þ ¼ z�1

1þ ai;jz�1 þ z�2ð2Þ

The modulator signal transfer function (STF) becomes

STF ¼ z�2

DjDi � P1z�2 � P2z�1Dj; ð3Þ

where Di,j = 1 ? ai,j z-1 ? z-2. Since the degree of the

denominator is four, it is necessary to adjust the value of

four parameters to make it equal to 1. Therefore, the blocks

P1 zð Þ and P2 zð Þ must be

P1 zð Þ ¼ b1 þ c1z�1

P2 zð Þ ¼ b2 þ c2z�1 ð4Þ

The values of coefficients b1, b2, c1, and c2 are the

solution of the system of equations

1� c2 ¼ 0

2þ ajai � b1 � b2aj � c2 ¼ 0

aj þ ai � c1 � b2 � c2aj ¼ 0

ai þ aj � b2 ¼ 0

8>><

>>:: ð5Þ

Thus, STF = z-2.

After defining the design parameters, it is necessary to

identify the circuit architecture. For the scheme of Fig. 2,

the task is not easy because of the second order denomi-

nators. An effective method that allows implementing that

scheme foresees the use a two-path architecture operated at

half of the clock frequency fs. This implements a z! z2

transformation. Halving the clock frequency reduces the

power consumption of each op-amp by almost four and the

overall power consumption is then halved.

Consider the scheme of Fig. 3. By inspection, it results

ðx� ayÞ z�1

1þ z�2¼ y ð6Þ

that yields the requested response

y ¼ xz�1

1þ az�1 þ z�2: ð7Þ

The advantage of the circuit of Fig. 3 is that the main

block is 1/(1 ? z-2) that, possibly, can be realized through

a z! z2 transformation. This is what Fig. 4 implements. It

is made by two paths, one processing the even samples, the

other the odd samples. Because of the delay in the numer-

ator of the block in Fig. 3, the inputs of the z-1/(1 ? z-2)

block are the even input signal and the odd output signal or

vice-versa. Therefore, the scheme of Fig. 4 uses cross

coupled connections. Notice that, since the injection on the

top path occurs at even times, the output remains constant

for two clock periods. For this reason, the delay on the

z-transfer function can be removed.

−1 −0.8 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1

−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

Real Part

Imag

inar

y P

art

a1

a2

Fig. 1 Desired position of the NTF zeros around the unity circle Fig. 2 Block diagram of the second-order bandpass RD modulator

412 Analog Integr Circ Sig Process (2012) 71:411–419

123

The use of two choppers and square wave modulators in

each path implements the block of Fig. 4 [10], as shown in

Fig. 5.

2.2 Fourth-order bandpass MASH RD modulator

The goal of this design is, as mentioned, to obtain four

couples of complex conjugate zeros in the modulator noise

transfer function

NTF ¼Y4

i¼1

1þ aiz�1 þ z�2

� �; ð8Þ

where ai (i = 1, 2, 3, 4) are real coefficients in the range

�2; 2½ �: Figure 6 shows the zero position around the unity

circle, with the chosen coefficient values ai: a1 = 12/8,

a2 = 13/8, a3 = 14/8, a4 = 15/8. With these values, the

zeros are near the Nyquist frequency. This keeps the

sampling frequency as low as possible.

This RD modulator architecture, illustrated in Fig. 7, is

based on a two-stage MASH structure. Both stages are

implemented with the two-path second-order scheme dis-

cussed in Section 2.1. The first stage ðRD1Þ realizes the

external zeros, corresponding to a1 = 12/8 and a4 = 15/8,

while the second stage ðRD2Þ implements the zeros corre-

sponding to a2 = 13/8 and a3 = 14/8. These coefficients are

implementable with unity capacitors. The NTF of the second

order bandpass modulator RD1 is, therefore, given by

NTF1 ¼ 1þ a1z�1 þ z�2� �

1þ a4z�1 þ z�2� �

; ð9Þ

while the NTF of RD2 is

NTF2 ¼ 1þ a2z�1 þ z�2� �

1þ a3z�1 þ z�2� �

ð10Þ

The modulator RD2 receives as input the quantization error

�1 of RD1 The digital outputs, Y1 and Y2, of RD1 and RD2;

z-1

1+z-2

X Y

a

_+

Fig. 3 Implementation of the z-1/(1 ? az-1 ? z-2) transfer function

z-1

1+z-2

z-1

1+z-2

a

X

a

Y

even

evenodd

odd+

+_

_

Fig. 4 Implementation with cross coupled paths

++

z-1

z-1 xx

++

z-1

z-1 xx

1 0 -1 0 0 1 0 -1

0 1 0 -1 -1 0 1 0

X Y

Fig. 5 Implementation of the block used in Fig. 4

−1 −0.8 −0.6 −0.4 −0.2 0 0.2 0.4 0.6 0.8 1

−1

−0.8

−0.6

−0.4

−0.2

0

0.2

0.4

0.6

0.8

1

Real Part

raP

yranigamI

t

a1

a2

a3

a4

Fig. 6 Desired position of the NTF zeros around the unity circle

Fig. 7 Block diagram of the proposed MASH bandpass RDmodulator

Analog Integr Circ Sig Process (2012) 71:411–419 413

123

respectively, are processed by a digital filter that cancels

the quantization error of RD1 and realizes the overall NTF

given by (8). Since the outputs of RD1 and RD2 are

Y1 ¼ In � STF1 þ �1 � NTF1

Y2 ¼ �1 � STF2 þ �2 � NTF2

�; ð11Þ

respectively, where STF1 = STF2 = z-2, the digital filter

implements the function

Out ¼ Y1 � z�2 � Y2 � NTF1: ð12Þ

The result cancels the quantization error of RD1 shaped by

NTF1 and gives rise to the desired output, given by

Out ¼ In � z�4 þ �2 �Y4

i¼1

1þ aiz�1 þ z�2

� �: ð13Þ

3 Behavioral level study

The proposed MASH bandpass RD modulator architecture

has been verified at the behavioral level with Matlab-

SimulinkTM [11]. The simulations use oversampling ratio

(OSR) equal to nine and an input signal frequency (fin) of

73.74 MHz (fin ¼ fs � Nper=N; where fs = 180 MHz,

Nper = 839, and N = 211). Figure 8 shows the output

spectrum of the ideal modulator. The four zeros in the

signal band are clearly visible. The achieved signal-to-

quantization-noise ratio (SQNR) is about 116 dB.

The errors caused by real integrators and capacitive

mismatches affect the STF and the NTF of both modula-

tors. Mismatches change the coefficients of the design

equations and give rise to a shift of zeros. They move on

the unity circle until becoming coincident. Then, one of

them goes out of the unity circle. The limits of real active

elements are difficult to study, however, finite gain and

bandwidth move the zero inside the unity circle, blurring

the shaping due to zeros and making difficult the cancel-

lation of the quantization noise in the MASH structure. The

effect has been studied at the behavioral level, [12].

A sampling capacitance equal to 1.2 pF is used for

modeling the kT/C noise. The output spectrum is reported

in Fig. 9. The four zeros are not visible but the noise

shaping is still good in the signal band. The integral of the

spectrum leads to a signal-to-noise ratio (SNR) higher than

80 dB with a signal bandwidth of 10 MHz.

The kT/C noise limitation reduces the SNR. The tone at

fs/4 is due to path mismatch. The limit caused by capacitors

mismatch affects less the SNR, as shown by a statistical

study with a random error on matching with r ¼ 5 � 10�3:

The results, achieved over 100 simulations as depicted in

Fig. 10, show a minimum SNR of 94 dB. The result is in

line with performance sensitivity of other RD designs, [13].

4 Circuit implementation

The modulator is implemented at the transistor level using

a 0.18-lm CMOS technology and a voltage supply of

1.8 V. The two second-order modulators realizing the

MASH structure are implemented using four switched-

capacitor (SC) integrators and two 5-bit flash ADCs each.

Since the solutions of (5) are integer multiples of the

fraction 1/8, with the considered values of coefficients ai

(i = 1, 2, 3, 4), it is relatively easy to implement the

feedback coefficients by capacitive ratios in the SC cir-

cuits. The used unity capacitor value for the SC network

driving the first op-amps of the first modulator (RD1 of

Fig. 7) is 150 fF to respect the kT/C noise limit. The

capacitors of the remaining integrators use, as unity

0 1 2 3 4 5 6 7 8 9

x 107

−180

−160

−140

−120

−100

−80

−60

−40

−20

0

Frequency [Hz]

PS

D [d

B]

SQNR = 116.3dB @ OSR=9

ENOB = 19.03 bits @ OSR=9

Fig. 8 Output spectrum of the proposed RD modulator under ideal

conditions

10 2 3 4 5 6 7 8 9

x 107

Frequency [Hz]

PS

D [d

B]

SNR = 84.2dB @ OSR=9

ENOB = 13.7 bits @ OSR=9

−180

−160

−140

−120

−100

−80

−60

−40

−20

0

Fig. 9 Simulated output spectrum of the MASH RD modulator

414 Analog Integr Circ Sig Process (2012) 71:411–419

123

element value, 50 fF. This ensures the required matching

accuracy. Fig. 11 depicts the circuital implementation of

the cross coupled structure of Fig. 4 together with its

driving phases. in± is the input signal while Vdac1± and

Vdac2± are the signals coming from the DACs of the two

paths. Vb is the analog ground. The scheme includes

feedback signals coming from the DACs which realize

P1 and P2 of (4).

The eight operational amplifiers are designed using a

conventional two-stage fully-differential architecture with

RC compensation and discrete-time common mode feed-

back network. To define the op-amps specifications, the

modulator is studied at transistor level with CadenceTM

simulations. Table 1 summarizes the amplifiers specs. The

implemented op-amps, whose features are given in

Table 2, meet the specifications derived from the simula-

tion analysis and the power consumption constraints of the

project. Notice that the specifications of the amplifiers used

to realize second integrators in the first modulator (RD1 of

Fig. 7) and of the op-amps used in the second modulator

(RD2 of Fig. 7) can be slightly relaxed, thus saving power.

The comparators used in the flash ADCs consist of a

pre-amplification stage and a latch. The pre-amplifier is a

fully differential structure made by two cross-coupled

differential pairs and continuous-time common mode

feedback. The simulated power consumption is 0.11 mW.

Montecarlo analysis with 100 runs shows that with a half

LSB sensitivity, the outputs of the comparators are correct

in 95% of the total cases. The DACs are Kelvin dividers

implemented with poly-silicon resistors. Table 3 summa-

rizes the power consumption of the circuits used in the

modulator. The simulated total power consumption is about

90 mW.

Figure 12 shows the output spectrum of the MASH

architecture implemented and simulated at transistor level,

94 96 98 100 102 104 106 108 110 112 1140

5

10

15

20

25

SNR [dB]

Sam

ples

Fig. 10 Simulated SNR (100 runs) considering errors in all the

coefficient values (r ¼ 5� 10�3)

+

_

Cf

O1+

O1-

Cf

a

b

Vdac2-

Vdac1-

c 1

d

2

Vdac2+

Vb

C2

Vdac1+

a

b

Vb

in-

c 1

d

2

Vb

Vb

C1

in+

a

b

Vb

in+

c 1

d

2

Vb

Vb

C1

in-

c

d

Vdac2+

O2-

a1

b

2

Vdac2-

Vb

C3

O2+

+

_

Cf

O2+

O2-

Cf

d

a

Vdac2+

Vdac1+

b2

c

1

Vdac2-

Vb

C2

Vdac1-

d

a

Vb

in+

b2

c

1

Vb

Vb

C1

in-

b

c

Vb

in+

d2

a

1

Vb

Vb

C1

in-

d

a

Vdac2+

O1-

b 2

c

1

Vdac2-

Vb

C3

O1+

a

b

c

d

1

2

Fig. 11 Circuital implementations of the resonator structure

Analog Integr Circ Sig Process (2012) 71:411–419 415

123

using an OSR equal to 9, an input frequency of

73.74 MHz, fs = 180 MHz, and 211 points for the FFT.

The obtained signal-to-noise and distortion ratio SNDR is

about 80 dB with a signal bandwidth of 10 MHz, leading

to an effective number of bits (ENOB) equal to 13.09.

The SNDR degradation with respect to the SNR value

obtained in Fig. 9 is mainly due to switch and DAC

non-idealities.

5 Measurement results

As mentioned, the circuit has been fabricated using a

0.18 lm CMOS technology with two poly-silicon and six

metal layers. The nominal power supply voltage and

Table 1 Op-amp specifications

Gain (dB) Slew-rate (V/ls) fT

First 65 500 1 GHz

Others 55 500 950 MHz

Table 2 Op-amp features

Gain

(dB)

Slew-rate

(V/ls)

fT(MHz)

Phase

Margin

(degree)

Power

consumption

(mW)

First 63 490 950 61 10

Others 54 480 870 65 7.3

Table 3 Power consumption at 1.8-V voltage supply

Circuit Power consumption (mW) Number Total (mW)

Op-amp1 10 2 20

Op-amp2 7.3 6 43.8

Comparator 0.11 124 13.64

DAC 2 4 8

Logic 5 1 5

Total power consumption 90.44

0 1 2 3 4 5 6 7 8 9

x 107

−150

−100

−50

0

Frequency [Hz]

PS

D [d

B]

SNDR = 80.6dB @ OSR=9

ENOB = 13.09 bits @ OSR=9

Fig. 12 Output spectrum of the proposed RD modulator obtained

with transistor-level simulation

1

2

Path 1

Path 2

Path 1

Path 2

Fig. 13 Chip microphotograph

0 1 2 3 4 5 6 7 8 9

x 107

Frequency [Hz]

PS

D [d

B]

−160

−140

−120

−100

−80

−60

−40

−20

0

Fig. 14 Measured spectrum of the second-order bandpass RDmodulator (RD1)

416 Analog Integr Circ Sig Process (2012) 71:411–419

123

sampling frequency are 1.8 V and 180 MHz, respectively.

Figure 13 shows the chip microphotograph with layout on

the background in which the first and the second modula-

tors (RD1 and RD2; respectively) have been indicated. In

addition, the two paths used for each modulator are clearly

visible. The chip area is 3.38 mm2, including the pad-ring.

The digital processing is done off-chip.

For testing purposes, the output of the first modulator

(RD1) can be disconnected from the input of the second

modulator (RD2) of the MASH structure and connected to

the output pins. The measured spectrum at the output of

RD1 is depicted in Fig. 14. With an input signal at

70.5 MHz, the achieved resolution is 9.2 bits on a band-

width of 10 MHz. The tone at fs/4 is caused by path

mismatch.

Figure 15 shows the measured output spectrum of the

MASH RD modulator. The input frequency is 70.5 MHz

and the FFT uses 217 points. The tone at fs/4 is due to path

mismatch. The measured SNDR over a signal bandwidth of

10 MHz is 73.5 dB, corresponding to an ENOB of

11.9 bits. The 7-dB loss in SNDR with respect to what

achieved in simulation (Fig. 12) is mainly ascribed to

quantization noise leakage due to the mismatch between

the NTF actually implemented by the RD1 and the NTF

implemented in the digital filter, given by (9). Figure 16

shows the measured SNR as a function of the input signal

amplitude. The peak of the SNR is for input at -4 dBFS.

The measured power consumption is 95 mW, a value

slightly higher than what expected from simulations. A

useful figure-of-merit for bandpass RD modulators is

defined as [8]

FoMBP ¼ P

2ENOB2B 1þ 3fIFfN

� � ¼ FoM

1þ 3fIFfN

; ð14Þ

where P is the power consumption, ENOB the effective

number of bits, B the signal bandwidth, fIF the intermediary

frequency, fN = fs/2, and FoM, defined as

FoM ¼ P

2ENOB2B; ð15Þ

is the usual figure-of-merit used for ADCs. The definition

of FoMBP basically accounts for the extra power con-

sumption needed for handling high-frequency input signals

(around fIF) even for small values of B. The resulting

0 1 2 3 4 5 6 7 8 9

x 107

Frequency [Hz]

PS

D [d

B]

−160

−140

−120

−100

−80

−60

−40

−20

0

Fig. 15 Measured output spectrum of the proposed fourth-order

MASH bandpass RD modulator

Fig. 16 Measured SNR as a function of the input signal amplitude

Table 4 State of the art of bandpass RD modulator

P (mW) @ VDD (V) fs (MHz) IF (MHz) BW (MHz) SNDR (dB) FoMBPpJ

conversion�level

� Reference

95 @ 1.8 180 70.5 10 73.5 0.37 This work

16 @ 1.8 120 40 1 65.1 1.8 [8]

150 @ 1.8 120 40 2.5 69 4.3 [7]

88 @ 1.8 37.5 10.7 0.2 71 28 [4]

37 @ 3.3 240 60 0.2 72 11.4 [3]

47.5 @ 3.3 92 23 0.27 80 4.3 [2]

160 @ 1.8 800 200 10 70 1.27 [14]

Analog Integr Circ Sig Process (2012) 71:411–419 417

123

FoMBP for the proposed RD modulator is 0.37 pJ/conver-

sion-level, which is well below the state of the art. Table 4

compares the achieved results with some bandpass RDmodulators published in the literature.

6 Conclusions

In this paper a MASH bandpass RD modulator that uses

two second-order modulators implemented with two paths

and resonators and that features four couples of complex

conjugate zeros in the noise transfer function is described.

The circuit, fabricated with a 0.18 lm CMOS technology,

uses a sampling frequency of 180 MHz and achieves a

resolution of about 12 bits considering a signal bandwidth

of 10 MHz centered around the 70.5 MHz IF. The mea-

sured power consumption is 95 mW.

Acknowledgment The authors wish to thank National Semicon-

ductor for chip fabrication and FIRB, Italian National Program

#RBAP06L4S5, for partial economical support.

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in 0.35 lm CMOS technology. In Proceedings of IEEE CustomIntegrated Circuit Conference (pp. 123–126).

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Venes, A. G. (1999). A sixth-order continuous-time bandpass

sigma-delta modulator for digital radio IF. IEEE Journal of Solid-State Circuits , 34(12), 1753–1764.

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band pass RD modulator with 72 dB SNR and 86 dB SFDR. In

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bandpass RD modulator with 72 dB DR consuming 16 mW.

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switched-capacitor sigma-delta modulators.IEEE Transactions onCircuits and Systems—Part I: Fundamental Theory and Appli-cations , 50(3), 352–364.

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14. Lu, C. Y., Silva-Rivas, J. F., Kode, P., Silva-Martinez, J., &

Hoyos, S. (2010). A sixth-order 200 MHz IF bandpass sigma-

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Herve Caracciolo was born in

Vigevano, Italy, in 1983. He

received the Master Degree

(Summa cum Laude) in Elec-

tronic Engineering from the

same University with a thesis on

a Sigma-Delta modulator. From

2007 to 2010 he worked at the

Integrated Microsystem Labo-

ratory (IMS) of University of

Pavia, Italy, as a Ph.D. student.

His research activity was

focused on analog amplifier and

data converters design. On Jan-

uary 2011 he received the

MicroElectronics Ph.D. title from the University of Pavia. He is co-

recipient the IEEE/IEEJ Analog VLSI Workshop (AVLSIWS) 2007

best paper award. Now he works at Fondazione CNAO (Pavia, Italy)

as an electronic engineer in beam diagnostic group for oncological

hadrontherapy accelerator machine.

Edoardo Bonizzoni was born in

Pavia, Italy, in 1977. He

received the Laurea degree

(summa cum laude) in Elec-

tronic Engineering from the

University of Pavia, Pavia, Italy,

in 2002. From the same Uni-

versity, he received in 2006 the

Ph.D. degree in Electronic,

Computer, and Electrical Engi-

neering. In 2002 he joined the

Integrated Micro Systems Lab-

oratory of the University of

Pavia as a Ph.D. candidate.

During his Ph.D., he worked on

development, design and testing of non-volatile memoires with par-

ticular regard to phase-change memories. From 2006 his research

interests are mainly focused on the design and testing of DC-DC and

A/D converters. In this period, he worked on single-inductor multiple-

output DC-DC buck regulator solutions and on both Nyquist-rate and

oversampled A/D converters. Recently, his research activity includes

the design of high precision amplifiers. He has authored or co-

authored more than 45 papers in international journals or conferences

(with published proceedings) and one book chapter. Dr. Bonizzoni is

co-recipient of the IEEE ESSCIRC 2007 best paper award, of the

418 Analog Integr Circ Sig Process (2012) 71:411–419

123

IEEJ Analog VLSI Workshop 2007 and of the IEEJ Analog VLSI

Workshop 2010 best paper award. Presently, he is an Associate Editor

of the IEEE Transactions on Circuit and Systems II.

Piero Malcovati was born in

Milano, Italy in 1968. He

received the ‘‘Laurea’’ degree

(Summa cum Laude) in Elec-

tronic Engineering from Uni-

versity of Pavia, Italy in 1991.

In 1992 he joined the Physical

Electronics Laboratory (PEL) at

the Federal Institute of Tech-

nology in Zurich (ETH Zurich),

Switzerland, as a Ph. D. candi-

date. He received the Ph. D.

degree in Electrical Engineering

from ETH Zurich in 1996. From

1996 to 2001 he has been

Assistant Professor at the Department of Electrical Engineering of the

University of Pavia. From 2002 Piero Malcovati is Associate Pro-

fessor of Electrical Measurements in the same institution. His

research activities are focused on microsensor interface circuits and

high performance data converters. He authored and co-authored more

than 40 papers in International Journals, more than 150 presentations

at International Conferences (with published proceedings), seven

book chapters, and five industrial patents. He is co-recipient of the

ESSCIRC 2007 best paper award. He was guest editor for the Journal

of Analog Integrated Circuits and Signal Processing for the special

issue on IEEE ICECS 1999, as well as Associate Editor for the IEEE

Transactions on Circuits and Systems II from 2008 to 2010. He served

as Special Session Chairman for the IEEE ICECS 2001 Conference,

as Secretary of the Technical Program Committee for the ESSCIRC

2002 Conference, as Technical Program Chairman of the IEEE

PRIME 2006 Conference, and as Technical Program Co-Chairman

for the IEEE ICECS 2009 Conference. He was and still is member of

the Scientific Committees for several International Conferences,

including ESSCIRC, SENSORS, ICECS, DATE and PRIME. He is

regional editor for Europe of the Journal of Circuits, Systems, and

Computers. He is an IEEE senior member.

Franco Maloberti received the

Laurea degree in physics

(summa cum laude) from the

University of Parma, Parma,

Italy, in 1968, and the Doctorate

Honoris Causa in electronics

from the Instituto Nacional de

Astrofisica, Optica y Electronica

(Inaoe), Puebla, Mexico, in

1996. He was the TI/J.Kilby

Chair Professor at the A&M

University, Texas and the

Distinguished Microelectronic

Chair Professor at the Univer-

sity of Texas at Dallas. He was a

Visiting Professor at The Swiss Federal Institute of Technology

(ETH-PEL), Zurich, Switzerland and at the EPFL, Lausanne, Swit-

zerland. Presently he is Microelectronics Professor and Head of the

Micro Integrated Systems Group, University of Pavia, Italy and

Honorary Professor, University of Macau, China SAR. His profes-

sional expertise is in the design, analysis, and characterization of

integrated circuits and analog digital applications, mainly in the areas

of switched-capacitor circuits, data converters, interfaces for tele-

communication and sensor systems, and CAD for analog and mixed

A/D design. He has written more then 400 published papers on

journals or conference proceedings, four books, and holds 30 patents.

Dr. Maloberti was the recipient of the XII Pedriali Prize for his

technical and scientific contributions to national industrial production,

in 1992. He was co-recipient of the 1996 Fleming Premium, IEE, the

best Paper award, ESSCIRC-2007, and the best paper award, IEEJ

Analog Workshop-2007. He received the 1999 IEEE CAS Society

Meritorious Service Award, the 2000 IEEE CAS Society Golden

Jubilee Medal, and the IEEE Millenium Medal. Dr. Maloberti was

Vice-President, Region 8, of the IEEE Circuit and Systems Society

(1995-1997), Associate Editor of IEEE-Transaction on Circuit and

System-II 1998 and 2006-07, President of the IEEE Sensor Council

(2002-2003), member of the BoG of the IEEE-CAS Society (2003-

2005) and Vice-President, Publications, of the IEEE CAS Society

(2007-2008). He is Distinguished Lecturer of the Solid State Circuit

Society and Fellow of IEEE.

Analog Integr Circ Sig Process (2012) 71:411–419 419

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