Envelope Tracking Power Amplifiers for Wireless Communications

360 Pages·2014·26.47 MB·English

by  Zhancang Wang

Envelope Tracking Power Amplifiers
for Wireless Communications
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Envelope Tracking Power Amplifiers
for Wireless Communications
Zhancang Wang
Library of Congress Cataloging-in-Publication Data
A catalog record for this book is available from the U.S. Library of Congress.
British Library Cataloguing in Publication Data
A catalog record for this book is available from the British Library.
ISBN-13: 978-1-60807-784-7
Cover design by Igor Valdman
© 2014 Artech House
All rights reserved. Printed and bound in the United States of America. No part
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accuracy of this information. Use of a term in this book should not be regarded
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10 9 8 7 6 5 4 3 2 1
Contents
Preface xi
Acknowledgments xv
CHAPTER 1
High-Efficiency Power Amplifier Architectures and Devices 1
1.1 Efficiency Definitions for RF PA 2
1.2 Characteristics of Modern Modulated Signals 3
1.2.1 Crest Factor 4
1.2.2 Probability Density Function 4
1.2.3 Second Generation Signal 5
1.2.4 Third Generation Signal 6
1.2.5 Fourth Generation Signal 7
1.3 Architectures for High-Efficiency PA 7
1.3.1 Switch Mode PA 9
1.3.2 Waveform-Engineered PA 22
1.3.3 Doherty 26
1.3.4 LINC and Outphasing 32
1.3.5 Envelope Elimination and Restoration 34
1.3.6 Envelope Tracking 35
1.4 Device Technologies for High-Efficiency PA 37
1.4.1 GaAs HBT 38
1.4.2 CMOS 39
1.4.3 Si-LDMOS 42
1.4.4 GaN HEMT 43
References 46
CHAPTER 2
Envelope Tracking Power Amplifier Basics 51
2.1 Introduction 51
2.1.1 Motivation for ET 51
2.1.2 ET Pyramid 53
2.2 Principle of ET 54
2.2.1 Signal Definition 55
v
vi Contents
2.2.2 ET Efficiency 56
2.2.3 Design Considerations 56
2.3 Instantaneous Efficiency of PA 57
2.3.1 Class-B Deduction 58
2.3.2 ET Deduction 61
2.3.3 Efficiency Degradation Factor 63
2.4 Statistical Average Efficiency of ET 65
2.4.1 Statistical Average Efficiency Definition 66
2.4.2 Efficiency and Gain Trajectory for ET 67
2.5 Bandwidth of ET 72
2.5.1 Bandwidth of Envelope 72
2.5.2 Video Bandwidth of ET 74
2.6 Linearity of ET 75
2.6.1 Two-Tone IMD 76
2.6.2 Modulated Signal Linearity 76
2.7 Power Capacity for ET Scenarios 81
2.7.1 ET for BTS 82
2.7.2 ET for Mobile 83
2.7.3 VSWR Immunity in ET 84
2.8 Frequency Agility 85
2.8.1 MMMB PA with ET 85
2.8.2 ET PA Integration 87
References 87
CHAPTER 3
Envelope Generation and Alignment 91
3.1 Envelope Generation 92
3.1.1 Analog Generation 92
3.1.2 Digital Generation 95
3.1.3 MIPI eTrak Interface 98
3.2 Envelope Detector Specifications 100
3.2.1 Dynamic Range 101
3.2.2 Modulation Bandwidth 101
3.2.3 Slew Rate 103
3.2.4 Conversion Gain 105
3.2.5 Gain Ripple 106
3.2.6 Temperature Variance 106
3.2.7 Transfer Function 107
3.2.8 Total Harmonic Distortion 109
3.2.9 Response Delay 110
3.3 Timing Alignment 111
3.3.1 Analog Alignment 112
3.4 Offset Adjustment 113
3.4.1 Principle of Operation 113
3.4.2 Adaptive Adjustment 114
References 115
Contents vii
CHAPTER 4
Supply Modulator for Envelope Tracking 117
4.1 Introduction 117
4.1.1 Supply Modulator Requirements 119
4.1.2 Mathematical Model for Efficiency 121
4.2 Linear Supply Modulator 123
4.2.1 Linear Voltage Regulator 124
4.2.2 Class-AB/B 125
4.2.3 Class-G/H 130
4.2.4 Power DAC 137
4.3 Discrete Supply Modulator 140
4.3.1 Isolated SMPS 141
4.3.2 Nonisolated SMPS 141
4.3.3 Summary of SMPS for ET 147
4.3.4 Multilevel Supply Modulator 149
4.3.5 Multiphase Supply Modulator 153
4.3.6 Output Filter for Discrete Modulator 156
4.4 Hybrid Supply Modulator 158
4.4.1 Serial Hybrid 158
4.4.2 Parallel Hybrid 161
4.4.3 AET Hybrid 169
4.4.4 CCG Hybrid 171
4.4.5 Power DAC Hybrid 174
4.4.6 Parallel Hybrid with Multiswitcher 175
4.4.7 Combined Hybrid 179
4.4.8 Nested and Multinested 181
References 185
CHAPTER 5
Power Amplifier for Envelope Tracking 191
5.1 RF PA Design Methodology 192
5.1.1 Measurement Method 192
5.1.2 Analytical Method 193
5.1.3 EDA and Modeling Method 193
5.2 Matching Network Design 195
5.2.1 Introduction 195
5.2.2 Matching Theory 196
5.2.3 Multisection and Taper Matching 201
5.2.4 Nonsynchronous Impedance Transformer 205
5.3 Bias Network Design 207
5.3.1 Classical Bias Network 207
5.3.2 ET Feeding Line Bias Network 209
5.4 Waveform-Engineered Matching 210
5.4.1 Engineered Waveforms 211
5.4.2 Harmonic Load-Pull 212
viii Contents
5.4.3 Physical Implementation 213
5.5 Class-P PA Design for ET 214
5.5.1 Waveform Engineered Class-P 215
5.5.2 Physical Implementation 217
5.5.3 Design for ET 222
5.6 Driver Design for ET Lineup 223
5.6.1 PAE Lineup 224
5.6.2 Lineup Implementation 225
References 226
CHAPTER 6
Digital Front End Design for Envelope Tracking 229
6.1 Digital Front End 229
6.2 Crest Factor Reduction 230
6.2.1 Threshold and Metrics 234
6.2.2 Peak-Windowing CFR 235
6.2.3 Noise-Shaping CFR 237
6.2.4 Peak-Cancellation CFR 239
6.2.5 Constrained Clipping CFR 240
6.3 Envelope Shaping Function 243
6.3.1 Introduction 243
6.3.2 De-Trough for Efficiency 244
6.3.3 De-Trough for Linearity 248
6.3.4 Sweet-Spot Tracking 250
6.3.5 Advanced Envelope Shaping 251
6.3.6 Bandwidth Reduction Shaping 252
6.3.7 Slew Rate Reduction Shaping 254
6.4 Timing Alignment 257
6.4.1 Timing Mismatch 258
6.4.2 Timing Alignment 258
6.5 Digital Predistortion 261
6.5.1 Introduction 262
6.5.2 DPD Forward Path 264
6.5.3 Complex LUT DPD 264
6.5.4 Memory Polynomial DPD 267
6.5.5 Combined DPD 268
6.5.6 DPD Feedback Path 270
6.5.7 Indirect Learning DPD 271
6.5.8 Direct Learning DPD 273
6.6 Image and Carrier Suppression 273
6.6.1 Quadrature Modulation Errors 274
6.6.2 Quadrature Modulation Correction 274
6.6.3 Adaptive QMC 277
References 278
Contents ix
CHAPTER 7
Experimental Methodologies and Measurements for Envelope Tracking 283
7.1 Motivation and Introduction 283
7.1.1 ET Test Considerations 284
7.1.2 Modulated Signal Measurement 284
7.1.3 Measurement Process 286
7.2 Envelope Measurement 292
7.2.1 Sinusoidal Signal Measurement 293
7.2.2 Multitone Signal Measurement 294
7.2.3 True Envelope Measurement 295
7.3 Supply Modulator Measurements 297
7.3.1 Measurement Setup 297
7.3.2 Error Measurements 300
7.3.3 Design Considerations for Measurement 302
7.4 RF PA Measurements 303
7.4.1 Nonlinear Vector Network Analysis 305
7.4.2 Swept Load-Pull 306
7.4.3 Measurement for Memory Effects 309
7.4.4 Measurements for ET Trajectory 310
7.5 ET PA Measurements 316
7.5.1 Test Bed Synchronization 316
7.5.2 CW Versus Complex Stimulus Measurements 317
7.5.3 Complex Measurements Setup 319
7.5.4 Complex Characterization Techniques 322
7.5.5 Power Measurements 323
7.5.6 Efficiency Measurements 324
References 327
About the Author 331
Index 333