Phased-Array Radar Design: Application of Radar Fundamentals Tom Jeffrey SciTech Publishing, Inc., 911 Paverstone Drive, Suite B Raleigh, NC 27615 919) 847-2434, fax (919) 847-2568 scitechpublishing.com. Copyright © 2009 by SciTech Publishing, Raleigh, NC All rights reserved. Published by SciTech Publishing, Raleigh, NC No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or other- wise, except as permitted under Sections 107 or 108 of the 1976 United Stated Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, 222 Rosewood Drive, Dan- vers, MA 01923, (978) 750-8400, fax (978) 646-8600, or on the web at copyright.com. 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ISBN: 9781891121692 Library of Congress Cataloging-in-Publication Data Jeffrey, Tom, 1954– Phased-array radar design : application of radar fundamentals / Tom Jeffrey. p. cm. ISBN 978-1-891121-69-2 (hbk. : alk. paper) 1. Phased array antennas--Design and construction. 2. Radar. I. Title. TK6590.A6J44 2009 621.3848'3--dc22 2008042350 Abbreviations AAW Anti-Air Warfare INS Inertial Navigation System ABT Air-Breathing Target JPDA Joint Probability Data AESA Active Electronically-Steered Association Array SLB Sidelobe Blanker AMTI Adaptive Moving Target SLC Sidelobe Canceller Indicator SM-2 Standard Missile-2 ANASIM Analog Simulation SMI Sample Matrix Inverse AR Auto-Regressive SNR Signal-to-Noise Ratio ASCS Antenna Servo Control System SP Signal Processor ATC Air Traffic Control STAP Space-Time Adaptive A/D Analog-to-Digital Converter Processing BMD Ballistic Missile Defense STP Short-Term Planner BSC Beam Steering Controller STS Short-Term Scheduler BSG Beam Steering Generator 2-D Two-Dimensional CDI Classification, Discrimination, 3-D Three-Dimensional Identification KF Kalman Filter CFAR Constant False Alarm Rate LFM Linear Frequency Modulation CI Coherent Integration LFOV Limited Field-of-View DA Data Association LR Likelihood Ratio DBF Digital Beam Forming LRT Likelihood Ratio Test D-S Dempster-Shafer LTP Long-Term Planner DIGSIM Digital Simulation LTS Long-Term Scheduler EKF Extended Kalman Filter MFR Multifunction Radar EM Electromagnetic MHT Multiple Hypothesis Tracker EO Electro-Optics MHz Megahertz ESA Electronically-Steered Array MMSE Minimum Mean Square Error FFOV Full Field-of-View MSLC Multiple Sidelobe Canceller FFT Fast Fourier Transform MSPAR Mechanically Steered Phased FOR Field-of-Regard Array Radar FOV Field-of-View MTD Moving Target Detector GHz Gigahertz MTI Moving Target Indicator GLR Generalized Likelihood Ratio NB Narrowband GLRT Generalized Likelihood Ratio NCI Non-Coherent Integration Test NCTR Non-Cooperative Target GPS Global Positioning System Recognition IBDA Innovations-Based Detection NN Nearest Neighbor Algorithm PAR Phased Array Radar ID Identification PD Probability of Detection IF Intermediate Frequency PDA Probabilistic Data Association IMM Interacting Multiple-Model PFA Probability of False Alarm xxi xxii Phased-Array Radar Design PRF Pulse Repetition Frequency SIR Signal-to-Interference Ratio PRI Pulse Repetition Rate TBM Tactical Ballistic Missile RAP Radar Activity Priority THAAD Theater High-Altitude Area RBF Receive Beam Former Defense RCS Radar Cross Section TI Track Initiation RF Radio Frequency TM Track Maintenance RLS Recursive Least Squares T/R Transmit/Receive RM Resource Manager TWS Track-While-Scan RMS Root Mean Square TWT Traveling Wave Tube RRE Radar Range Equation UAV Unmanned Aerial Vehicle RS Radar Scheduler U-D Upper-Diagonal SCR Signal-to-Clutter Ratio UHF Ultra-High Frequency SDP Signal Data Processor WB Wideband Preface This book is intended for systems, hardware, and software engineers who work in the radar field and desire a better understanding of the basics of modern ra- dar design. The book’s major objective is to review the fundamental theory and provide examples of its application to the design and analysis of phased-array radars. In general, key theoretical results are presented without derivation or proof except where necessary or useful to understand their application to spe- cific design problems. Ample references are provided throughout the book as sources of both radar theory and other useful information. INTENDED USES The book is designed to be used as a self-contained and stand-alone textbook and reference. However, it is assumed that the reader has a basic understanding and familiarity with most undergraduate engineering topics, including calculus, physics, linear systems theory, and probability, along with selected graduate- level subjects such as random processes, digital signal processing, statistical communications, and detection and estimation theory. Ideally, the reader would have the equivalent of a master’s degree in electrical engineering, which would include many of these topics. There are two basic ways to use the book. The first approach is to work se- quentially through the chapters. This is appropriate for those who are new to ra- dar or less familiar with applying the theory and desire a systematic treatment, or are using the text as a learner’s guide for Raytheon’s Advanced Topics in Ra- dar course and follow-on courses. The second approach is to selectively read only those chapters or sections needed to provide specific information. This would be the case for more experienced radar engineers that are interested in re- freshing or filling gaps in their existing knowledge. A central approach used in the book is learning the material via application of the theory to real-world cases studies and example problems. There are several examples interspersed among the chapters for this purpose. These include sev- xv xvi Phased-Array Radar Design eral aspects of the design of phased-array radars as well as touching on the de- sign of tracking filters and target classification algorithms for air and missile defense missions. In addition, some key mission-related factors associated with the design of air and missile defense radars, as well as missile early warning and surveillance radars, are presented to provide the reader with top-level design guidance for these applications. This book, when used in conjunction with relevant design courses, study and homework, on-the-job training, diverse radar-related work assignments, and mentoring will enable the reader to become proficient in radar design and analy- sis. It is also hoped that the importance of careful problem formulation and the trading off of candidate solutions is conveyed. It is expected that these skills and the associated processes will be immediately applicable to design and anal- ysis problems encountered both in academic settings and on the job. BOOK ORGANIZATION The book is organized as follows. The first six chapters cover the fundamental radar functions, including detection, waveforms and signal processing, search and acquisition, and target tracking and classification. These topics form the core radar systems theoretic treatment, beginning with a derivation of the gen- eral form of the radar range equation and tailored forms for the various radar functions, including volume and horizon search, tracking, as well as for operat- ing in clutter, and jamming environments. Chapter 7 introduces several data processing functions that are common to most phased-array radars. The key aspects of resource management and radar scheduling are introduced. Other functions treated are radar hardware control, radar echo processing, surveillance, tracking, and target classification. As these are algorithmic in nature and predominantly implemented in real-time soft- ware, they are often ignored or only discussed briefly in many radar design textbooks. Chapter 8 introduces the important capability of interference suppression from sources such as unintentional and intentional radio frequency (RF) emis- sions. Sidelobe blankers are described, followed by discussions of single and multiple-sidelobe cancellers, open loop nulling, and adaptive processing. The chapter concludes with a description of algorithms such as frequency agility and hopping, and transmit and receive sector blanking, typically software-con- trolled, which are commonly used interference mitigation techniques. Chapter 9 introduces phased-array radar architectures. The material is drawn from practical experience rather than theory, as in many of the previous chap- ters. Five major array-based radar architectures are discussed. These cover full field-of-view (FFOV) and limited field-of-view (LFOV) radars, fixed beam former and digital beam former (DBF) radars, and mechanically steered phased- Preface xvii array radars. Next, the requirements and architectures of narrow and wideband radar architectures are contrasted with one another. Finally, architectures tai- lored for search, track, fire control, and illumination functions are described. Chapter 10 addresses a key engineering design tool: the trade study and its application to the design of phased-array radars. After an overview, radar oper- ating frequency selection is examined as a function of mission and desired radar capabilities. Next, the equally important subject of waveform selection is cov- ered for common radar functions (i.e., search, track, and target classification and identification [ID]) in the clear, clutter, jamming, and chaff environments. Next, trades-offs addressing radar coverage and the receiver operating characteristics (ROCs) associated with certain target detection rules are discussed, followed by trades for search, track, and target classification design. Performance-driven hardware and software requirements are addressed in Chapter 11. The specification of hardware requirements, such as noise figure, phase noise, instantaneous dynamic range, and channel-to-channel alignment are related to specific system-level requirements. Similarly, the data processing requirements associated with tracking, target classification, and signal process- ing are related to their driving system-level requirements. The next three chapters address some top-level radar design requirements for the air and ballistic missile defense missions, as well as those for missile early warning systems. The key design drivers for each application are related to the top-level capabilities necessary to perform the particular mission. Like the prior two chapters, this material is also based on my experience in radar system de- sign for these specific types of missions. Chapter 15 examines the task of predict- ing performance for phased-array radars that execute search, track, target classification, interference suppression, and clutter cancellation functions. The last section of each chapter provides a list of relevant radar references. These include radar texts, handbooks, and pertinent papers from technical jour- nals. There are also practice problems at the end of some of the early chapters, in addition to the worked examples interspersed within many of the more analyti- cal chapters that serve to illustrate some key concepts. ACKNOWLEDGEMENTS This book is based on a number of in-house radar courses I taught at Raytheon over the last twenty-five years. Most the these courses were developed to fill a perceived need by working systems, hardware, and software engineers for basic and more advanced understanding of radar fundamentals necessary to perform their design tasks more effectively. The book is intended as an application-oriented guide to the design of modern radar systems, primarily ground and ship-based phased-array radars, for which Raytheon is widely acknowledged as a world-class leader. The material is based xviii Phased-Array Radar Design on both my work and teaching experiences at Raytheon and the General Electric (GE) Company. Over the last many years, I have had the good fortune to work as a radar system engineer on a number of phased-array radars developments, including the BMEWS and PAVE PAWS UHF early warning radars, the family of X-Band ballistic missile defense (BMD) radars that include the THAAD, SBX and High Power Discrimination radars, and the dual S- and X-band radars for the Cobra Judy Replacement shipboard data collection system. Much of the practical experience gained, and the radar design and analysis processes devel- oped, during these assignments are reflected in the book’s content. A number of the radar reference texts cited as references have been used as source material, as well as unpublished notes and teaching materials developed while working at GE and Raytheon. I would like to thank the many talented ra- dar system engineers at both companies who have helped me over the years and whose material in many cases I have reinterpreted and presented here. First, I would like to thank my instructors from the GE Advanced Course in Engineer- ing, who stressed problem-solving skills and the application of basic principles to developing engineering solutions. In addition, I would like to thank Eli Brookner, Fred Daum, Dan Harty, John Krasnakevich, Harry Mieras, Dan Ry- pysc, and John Toomey of the Raytheon Company for their help and many in- structive conversations on radar-related topics and applications during my years with the company. I am also grateful to Dr. Pramod Varshney of Syracuse University for teaching me detection and estimation theory nearly thirty years ago, and to Dr. Yaakov Bar-Shalom of the University of Connecticut, my alma mater, for providing me with a very useful theoretical foundation to develop and apply tracking and data association algorithms over the last twenty-plus years. Finally, I would also like to thank Dan Dechant, who has been a strong supporter of mine as well as a long-term advocate and sponsor, along with Charlene Corey, of systems engineering training at Raytheon. I would also like to give special thanks to Joe Yu, Dan Bleck, Mike Hart, Tom McDonagh, and Bob Millett, also of the Raytheon Company, without whose thorough review, helpful recommendations, and suggestions this book would not have been published. Last, I want to thank Mel Belcher, of Northrop Grum- man Corporation and formerly of Georgia Tech Research Institute, who made many useful suggestions during the early writing process that made this a better book. Finally, I gratefully acknowledge the good people at SciTech Publishing: Dud- ley Kay, SciTech’s president and my sponsoring editor; Susan Manning, who oversaw all production aspects; Robert Lawless, Susan’s production assistant; and cover artist Kathy Palmisano for their encouragement, support, suggestions, and patience as the book went through the important phases of review, layout, proofing, and tying up of the many loose ends. Some unforeseen circumstances Preface xix slowed completion of the final version of the book, but through it all we arrived at what I believe is the full realization of my goal, and that is the ultimate tribute to a close working relationship between an author and his publisher. Any errors and omissions are mine, however, and I would be grateful to read- ers for corrections and suggestions to improve future printings and editions. Tom Jeffrey Sudbury, MA [email protected] October 2008 Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv Abbreviations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .xxi Chapter 1 Radar Fundamentals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.2 Search and Track Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.3 Target Detection, Resolution, and Clutter Concepts . . . . . . . . . . . . . . . . . . . . .2 1.3.1 Target Detection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2 1.3.2 Radar Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 1.3.3 Clutter Backscatter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 1.4 Surveillance Radars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6 1.4.1 Volume Search . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 1.5 Radar Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 1.6 Radar Range Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 1.6.1 Jamming Effects on Signal-to-Noise Ratio. . . . . . . . . . . . . . . . . . . . . . . . .11 1.6.2 Other Forms of the Radar Range Equation . . . . . . . . . . . . . . . . . . . . . . . .13 1.6.2.1 Radar Range Equation for Volume Search. . . . . . . . . . . . . . . . . . . . .13 1.6.2.2 Radar Range Equation for Horizon Fence Search. . . . . . . . . . . . . . .15 1.6.2.3 Radar Range Equation for Tracking . . . . . . . . . . . . . . . . . . . . . . . . . .16 1.6.2.4 Radar Range Equation Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 1.7 Detection in Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17 1.7.1 Target Models. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 1.7.2 Detection and False Alarm Probabilities . . . . . . . . . . . . . . . . . . . . . . . . . .20 1.7.3 Detection in Thermal Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 1.7.4 Constant False Alarm Rate (CFAR) Processors. . . . . . . . . . . . . . . . . . . . .22 1.7.5 Detection in Clutter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23 1.8 Resolution and Measurement Accuracy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 1.9 Tracking Radars and the Monopulse Technique . . . . . . . . . . . . . . . . . . . . . . .28 1.10 Track-While-Scan Radars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28 1.11 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 1.12 Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 Chapter 2 Target Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33 2.2 Target Radio Frequency (RF) Scattering Models . . . . . . . . . . . . . . . . . . . . . . .34 2.3 Target Detection in Noise. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36 vii