Radar RF Circuit Design Nickolas Kingsley J. R. Guerci 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 catalogue record for this book is available from the British Library. Cover design by John Gomes ISBN 13: 978-1-60807-970-4 © 2016 ARTECH HOUSE 685 Canton Street Norwood, MA 02062 All rights reserved. Printed and bound in the United States of America. No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage and retrieval system, without permission in writing from the publisher. All terms mentioned in this book that are known to be trademarks or service marks have been appropriately capitalized. Artech House cannot attest to the accuracy of this information. Use of a term in this book should not be regarded as affecting the validity of any trademark or service mark. 10 9 8 7 6 5 4 3 2 1 Contents Acknowledgments xv Part I Microwave Background 1 1 Crossing the Chasm from System to Component Level 3 1.1 Basic Radar Systems Overview 3 1.1.1 Radar Transmitters 4 1.1.2 Radar Receivers 5 1.1.3 Fundamental Equations 5 1.1.4 Requirements on Components 8 1.2 Introduction to Microwave Components 9 1.2.1 Fundamental Equations 9 1.2.2 Essential Components 11 1.3 Traveling Wave Tubes Versus Solid State 12 1.4 “How” Components are Connected Matters 12 Exercises 15 References 15 Selected Bibliography 15 vii viii Radar RF Circuit Design Contents ix 2 Introduction to Microwave Design 17 2.1 Scattering Matrix 18 2.2 Matching Networks 20 2.2.1 Quantifying Mismatch 20 2.2.2 Graphically-Based Circuits 23 2.2.3 Distributed Matching Networks 28 2.3 Methods of Propagation 29 2.3.1 Wave Modes 30 2.3.2 Coaxial Cables (Coax) 32 2.3.3 Microstrip 33 2.3.4 Stripline 41 2.3.5 Coplanar Waveguide (CPW) 46 2.3.6 Waveguide 48 2.3.7 Discontinuities 50 2.4 Material Selection 51 2.4.1 Semiconductors 52 2.4.2 Metals 52 2.4.3 Ceramics 53 2.4.4 Polymers 54 2.4.5 New and Emerging Technologies 54 Exercises 55 References 56 Selected Bibliography 56 3 Component Modeling 59 3.1 Passive Modeling 59 3.1.1 Capacitor 60 3.1.2 Inductor 61 3.1.3 Resistor 64 3.1.4 Resonators 64 3.2 Footprint Modeling 66 3.3 Transistor Modeling 67 3.3.1 Semiconductor Background 67 3.3.2 Basic Transistor Theory Review 68 3.3.3 Transistor Imperfections 73 viii Radar RF Circuit Design Contents ix 3.4 Custom Models 73 3.5 Measurement Techniques 75 Exercises 78 References 83 Selected Bibliography 83 Part II Component Design 85 4 Power Amplifier 87 4.1 Amplifier Basics 87 4.1.1 Class A 90 4.1.2 Class B 92 4.1.3 Class AB 94 4.1.4 Class C 95 4.1.5 Harmonically Matched Classes 96 4.1.6 Do Classes Really Matter? 98 4.2 Design Strategies and Practices 98 4.2.1 Stability 99 4.2.2 Power and Gain 101 4.2.3 Efficiency 104 4.2.4 Gain Flattening 105 4.2.5 VSWR 106 4.2.6 Conjugate Matching 108 4.2.7 DC Bias Filtering 109 4.2.8 Multistage Amplifiers 110 4.3 Broadband Amplifiers 112 4.3.1 Multisection Matching 113 4.3.2 Balanced Amplifier 114 4.3.3 Push-Pull Amplifier 115 4.3.4 Distributed Amplifiers 118 4.4 Balancing Linearity and Efficiency 118 4.4.1 Explanation of Linearity 118 4.4.2 Doherty 123 4.4.3 Other Linearization Techniques 124 4.5 Multiphysics Concerns 126 x Radar RF Circuit Design Contents xi 4.5.1 Thermal Considerations 126 4.5.2 Mechanical Considerations 134 4.6 Local Oscillators (LOs) 137 4.7 Tubes, Solid-State, and Where They Overlap 138 Exercises 139 References 140 Selected Bibliography 140 5 LNAs 141 5.1 Explanation of Noise 141 5.1.1 Thermal Noise 143 5.1.2 Shot Noise 145 5.1.3 Flicker Noise 146 5.1.4 Noise Terminology 147 5.2 Transistor Noise Modeling 148 5.3 Design Strategies and Practices 148 5.3.1 Understanding Noise Circles 150 5.3.2 LNA Design 152 5.3.3 Self-Bias Scheme 153 5.3.4 Gain Equalizers 154 5.3.5 Resistor Component Selection 156 5.4 High Dynamic Range 156 5.5 Cryogenic Operation 159 5.6 Limiter Elimination 160 Exercises 161 References 161 Selected Bibiligraphy 162 6 Passive Circuitry 163 6.1 Limiting Factors and Ways to Mitigate 163 6.1.1 Lumped Elements 164 6.1.2 Bode-Fano Limit 164 6.1.3 Discontinuities 167 x Radar RF Circuit Design Contents xi 6.2 Couplers 170 6.3 Isolators and Circulators 174 6.4 Switches 175 6.5 Phase Shifters 179 6.6 Attenuators 180 6.7 Filters/Diplexers 182 6.8 Splitters/Combiners 184 6.9 Baluns 189 6.10 Mixers 192 6.11 Antennas 194 6.12 Current Density Analysis 195 Exercises 196 References 197 Selected Bibliography 197 Part III Higher-Level Integration 199 7 Microwave Integrated Circuits 201 7.1 Component Integration 201 7.1.1 MMIC 202 7.1.2 Hybrid 203 7.1.3 Multichip Modules (MCMs) 204 7.1.4 Packaging Options 206 7.2 Packaging Model 208 7.3 Designing for U.S. Military Standards 208 7.3.1 Robustness 210 7.3.2 Operating Stability 212 7.3.3 Environmental Considerations 212 7.3.4 Electrical Considerations 214 7.3.5 Mechanical Considerations 215 xii Radar RF Circuit Design Contents xiii 7.4 Designing for Pulsed Radar 215 7.4.1 Radar Terminology 215 7.4.2 Component Design 217 7.5 Taking Advantage of Simulators 218 7.5.1 Passives 219 7.5.2 Actives 219 7.5.3 Full-Electromagnetic (EM) Simulation 220 7.5.4 Manufacturing Assessment 222 7.6 Manufacturing Practices 223 7.6.1 Manufacturing Essentials 224 7.6.2 Engineering Practices for High Yield 225 7.6.3 Designing for MMIC-Level Cost Reduction 227 7.6.4 Designing for Module-Level Cost Reduction 228 Exercises 229 References 230 8 Transmit/Receive Module Integration 231 8.1 Integration Techniques 231 8.1.1 Physical Transitions 232 8.1.2 Wire and Ribbon Bonding 234 8.1.3 Proper Grounding 234 8.1.4 Achieving Compact Size 236 8.1.5 Component Placement 237 8.2 Preventing Oscillation 238 8.2.1 Even-Mode Oscillation 238 8.2.2 Odd-Mode Oscillation 238 8.2.3 Spurious Oscillation 238 8.2.4 Ground Loops 239 8.3 Preventing Crosstalk and Leakage 239 8.3.1 Electric Coupling 241 8.3.2 Magnetic Coupling 242 8.3.3 Shielding 244 8.4 Thermal Considerations 246 8.5 Mechanical Considerations 247 8.6 Module Simulation and Monte Carlo Analysis 248 xii Radar RF Circuit Design Contents xiii 8.7 Incorporating Digital into an RF Module 251 8.7.1 Common Digital Uses 252 8.7.2 Current Digital Infrastructure 253 8.7.3 Digital Radiation 253 8.7.4 Avoiding Mixed-Signal Issues 255 Exercises 256 References 259 Selected Bibligraphy 259 9 On the Measurement Bench 261 9.1 Measurement Uncertainty 261 9.2 Test Fixture Design 263 9.2.1 De-Embedding Fixture Effects 264 9.2.2 Connectors, Adapters, and Cables 266 9.3 Tips for Making it All Work 269 9.3.1 Unstable Active Circuits 269 9.3.2 Incorrect Frequency Response 269 9.3.3 Radiation or Coupling 270 9.3.4 Low Gain or Output Power 271 9.3.5 High Loss 272 9.3.6 Catastrophic Damage at Initial Test 272 9.4 Transistor Stabilization 273 Exercises 275 References 275 Selected Bibliography 276 10 Final Thoughts 277 Appendix A 281 A.1 Frequency Bands 281 A.2 English-to-Metric Units Conversion 282 A.3 Temperature Conversion 283 A.4 Constants and Material Properties 283 xiv Radar RF Circuit Design A.5 Math Functions 287 About the Authors 289 Index 291