Baseband Analog Circuits for Software Defined Radio

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Contents
$ l7 k& P. W7 P2 ADedication v
+ i5 t/ N, N- @; Y- pPreface xi
Acknowledgments xv
- S0 Q: K, M# E- b& q9 M5 |1. 4G MOBILE TERMINALS 1
" g: n$ [1 o3 o  s1.1 A Wireless-Centric World 1
1.2 The Driving Forces Towards 4G Systems 3
1.3 Basic Architecture For a 4G Terminal 6
1.4 The Role of Analog Circuits 8
; f, `/ j$ |3 ?2 X3 N1.5 Energy-Scalable Radio Front End 9
1.6 Towards Cognitive Radios 11
2. SOFTWARE DEFINED RADIO FRONT ENDS 13
2.1 The Software Radio Architecture 13
2.2 Candidate Architectures for SDR Front Ends 16
2.2.1 Heterodyne and digital-IF receivers 17
3 D8 b" c1 c* u' l" Y2.2.2 Zero-IF receivers 19
2.2.3 Digital low-IF receivers 22
& e1 r& V9 G  s8 m2 L; [2.2.4 Bandpass sampling receivers 24
, w4 `, Q$ b& h$ c2.2.5 Direct RF sampling receivers 26
2.3 SDR Front End Implementation 27
2.3.1 LNA and input matching 29
2.3.2 Frequency synthesizer 30
2.3.3 Baseband signal processing 31
. D$ ]/ t' d' X9 q- J( _. X2.3.4 Measurements results 31
2.4 Digital Calibration of Analog Imperfections 33
0 ~7 q" W$ j. V$ F: }- l7 H* B9 c2.4.1 Quadrature imbalance 34
: i# D7 y; {. |( i# l# O3 N2.4.2 DC offset 36
viii Contents
; l) L' y: j$ a. t2.4.3 Impact of LPF spectral behavior 36
) i5 Y+ O; ?( p2.5 Conclusions 37
+ a1 \+ W; S& c, l9 Z" T6 s3. LINK BUDGET ANALYSIS IN THE SDR ANALOG
BASEBAND SECTION 39
3.1 Analog Baseband Signal Processing 39
+ |$ P1 d% p8 O' H2 B3.2 Baseband Trade-Offs for Analog to Digital Conversion 40
3.2.1 Number of poles for the LPF 41
7 `; q9 o5 h/ |! Y9 n6 ]- {3.2.2 ADC dynamic range 42
: E5 s% N; L3 L' W3.2.3 Baseband power consumption estimation 47
. O1 t5 h+ g" u9 r3.3 Multistandard Analog Baseband Specs 48
3.4 Multimode Low-Pass Filter 49
3.4.1 Filter selectivity 50
3.4.2 Filter noise and linearity 54
3.4.3 Filter flexibility planning 56
% o- m% u, B" I# L3.4.4 Cascade of biquadratic sections 59
3.5 Automatic Gain Control 62
) D1 @- v7 E5 ~9 J; z3 Z3.6 Conclusions 65
4. FLEXIBLE ANALOG BUILDING BLOCKS 67
4.1 Challenges in Analog Design for Flexibility 67
0 e" H2 j5 K" n) m( q$ }8 ]0 r: A2 O4.2 A Modular Design Approach 68
4.3 Flexible Operational Amplifiers 70
4.3.1 Variable current sources 70
4.3.2 Arrays of operational amplifiers 71
4.4 A Digital-Controlled Current Follower 75
4.5 Flexible Passive Components 75
4.6 Flexible Transconductors 77
6 T1 E5 v% w5 G5 p" @+ j1 o4.7 Flexible Biquadratic Sections 78
4.7.1 The Active-Gm-RC biquad 79
( Q( r; L$ o! N6 \4.8 Conclusions 91
5. IMPLEMENTATIONS OF FLEXIBLE FILTERS FOR SDR
& g: L% W9 k7 N( T7 Y7 ?1 Y4 zFRONT END 93
! D4 G7 O1 |' A3 O. {2 p; H5.1 State of the Art for Flexible CT Filters 93
5.2 A Reconfigurable UMTS/WLAN Active-Gm-RC LPF 94
5.2.1 Filter architecture 96
5.2.2 Automatic RC calibration scheme 97
/ O, m8 O% s& @. m5 |' U5.2.3 Measurements results 102
Contents ix
5.3 LPF and VGA for SDR Front End 105
5.3.1 LPF and VGA architectures 107
& H8 S# U8 J3 {) Y3 d; Z3 n5.3.2 Prototype measurements 111
* j/ V7 {! S& R5.4 Conclusions 118
# b. q. _1 d4 p8 q2 A1 ]Acronyms 119
( J  {  W* @9 }- e& Y& OList of Figures 123
# n) _! }9 `& EList of Tables 129
' O# ]0 r2 C7 IReferences 131
Index 139