Baseband Analog Circuits for Software Defined Radio

cnasic

Contents
# a0 u3 {1 `7 d2 u6 r) I: xDedication v
  ^& T, `1 v# W5 I9 Z/ Q( kPreface xi
Acknowledgments xv
1. 4G MOBILE TERMINALS 1
1.1 A Wireless-Centric World 1
1.2 The Driving Forces Towards 4G Systems 3
" w# ]1 \+ f: p* X* t1.3 Basic Architecture For a 4G Terminal 6
" B$ k: A7 C( U6 a- ^: g1.4 The Role of Analog Circuits 8
1.5 Energy-Scalable Radio Front End 9
. o. Z6 Z# v: r* L1 m+ h1.6 Towards Cognitive Radios 11
  o% H' u1 v2 T, m2. SOFTWARE DEFINED RADIO FRONT ENDS 13
2.1 The Software Radio Architecture 13
5 M) H- {/ |. U! c) G0 F: Q$ V$ K2.2 Candidate Architectures for SDR Front Ends 16
9 Y' x/ g' J$ [2.2.1 Heterodyne and digital-IF receivers 17
2.2.2 Zero-IF receivers 19
2.2.3 Digital low-IF receivers 22
2.2.4 Bandpass sampling receivers 24
1 v7 X9 W! Y$ s2.2.5 Direct RF sampling receivers 26
4 y! \  v  Z: o0 X/ @. A8 a9 o2.3 SDR Front End Implementation 27
2.3.1 LNA and input matching 29
* ]' ?. V! T2 e7 V7 s2.3.2 Frequency synthesizer 30
2.3.3 Baseband signal processing 31
+ ?6 \) o& b: K" n9 r2.3.4 Measurements results 31
0 T9 S# F( J6 C$ O1 Q2 T* F8 d2.4 Digital Calibration of Analog Imperfections 33
2.4.1 Quadrature imbalance 34
+ a8 g9 [" N9 F4 B% l2 j, n' H3 @2.4.2 DC offset 36
- k' a4 p" h0 p0 ~- L' _, tviii Contents
2.4.3 Impact of LPF spectral behavior 36
2.5 Conclusions 37
3. LINK BUDGET ANALYSIS IN THE SDR ANALOG
BASEBAND SECTION 39
3.1 Analog Baseband Signal Processing 39
% C* g( ^/ W# G3.2 Baseband Trade-Offs for Analog to Digital Conversion 40
3.2.1 Number of poles for the LPF 41
& ^' ], _; g% i# f; }3.2.2 ADC dynamic range 42
3.2.3 Baseband power consumption estimation 47
4 k+ I1 s7 G1 W0 s4 D3.3 Multistandard Analog Baseband Specs 48
3.4 Multimode Low-Pass Filter 49
: r# E1 h% o7 w) \, s3.4.1 Filter selectivity 50
3.4.2 Filter noise and linearity 54
" m3 s, @# e/ `3 w' y' P* T5 F3.4.3 Filter flexibility planning 56
3.4.4 Cascade of biquadratic sections 59
3.5 Automatic Gain Control 62
3.6 Conclusions 65
4. FLEXIBLE ANALOG BUILDING BLOCKS 67
) E, t0 A6 B3 X: e1 P2 a4.1 Challenges in Analog Design for Flexibility 67
4 X; ?3 \3 }; G9 _9 Y# u  s3 Y4.2 A Modular Design Approach 68
4.3 Flexible Operational Amplifiers 70
8 O0 V. ?# d  c* Z! v9 D4.3.1 Variable current sources 70
4.3.2 Arrays of operational amplifiers 71
' Y( Y3 Z+ l4 e8 z4 @4.4 A Digital-Controlled Current Follower 75
4.5 Flexible Passive Components 75
4.6 Flexible Transconductors 77
4.7 Flexible Biquadratic Sections 78
4.7.1 The Active-Gm-RC biquad 79
4.8 Conclusions 91
' U. h1 }8 h9 `; R5. IMPLEMENTATIONS OF FLEXIBLE FILTERS FOR SDR
FRONT END 93
5.1 State of the Art for Flexible CT Filters 93
5.2 A Reconfigurable UMTS/WLAN Active-Gm-RC LPF 94
! B( V7 G9 {# V; }4 h5 ]0 M5.2.1 Filter architecture 96
5.2.2 Automatic RC calibration scheme 97
7 z4 k! A8 I- a4 G( B" Z- p" U5 X5.2.3 Measurements results 102
Contents ix
& O' u8 L, G* K5.3 LPF and VGA for SDR Front End 105
0 j+ r2 J6 E0 E8 o5.3.1 LPF and VGA architectures 107
5.3.2 Prototype measurements 111
5.4 Conclusions 118
Acronyms 119
List of Figures 123
& `3 ^) v2 v$ e  qList of Tables 129
References 131
7 g, p: F+ p7 @+ n2 m. a* t' V2 DIndex 139