Radar Design Principles - Signal Processing and the Environment

686 Pages·1999·31.497 MB·English

by  Nathanson, F.E.

Radar Design
Principles
Signal Processing and the Environment
Fred E. Nathanson
Georgia Tech Research lnstitute
Rockville, Maryland
with
J. Patrick Reilly
The Johns Hopkins University
Applied Physics Laboratory
Laurel, Maryland
Marvin N. Cohen
Georgia Tech Research lnstitute
Georgia lnstitute of Technology
Atlanta, Georgia
Second Edition
s c ; 3
PUBLISHING, IRC.
~
MENDHAMN, EWJ ERSEY
This is a reprinting of the 1991 edition
originally published by McGraw-Hill, Inc.
0 1999 by Marvin N. Cohen, Allan J. Nathanson, Lila H. Nathanson,
Janice N. Smith, J. Patrick Reilly
0 1991, 1969 by McGmw-Hill, Inc.
All rights reserved. No part of this book may be reproduced
or used in any form whatsoever without written permission from
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Acknowledgments
The dramatic advances in radar systems and especially in radar signal
processing are the result of the efforts of many individuals in many
fields. To help me assimilate this information, I enlisted the aid of a
number of knowledgeable coworkers in the radar field.
The primary credit goes to J. Patrick Reilly of the Johns Hopkins
University, Applied Physics Laboratory, for both the original book and
this edition. He authored Chap. 9 and significant portions of Chap. 1,
2,3,5,6,a nd 7. Dr. Marvin Cohen of Georgia Tech Research Institute
(GTRI) contributed a new version of Chap. 12 and contributed to the
rewrite of Chap. 13.
I thank Dr. Mark Richards (GTRI) who contributed the new section
on pulse Doppler signal processor architecture; Me1 Belcher (GTRI) for
the CFAR section in Chap. 4; A. Corbeil, J. DiDomizio, and R. DiDomizio
of Technology Service Corporation, Trumbull, Connecticut for the new
material on track before detect in Chap. 4; and Allen Sinsky of Allied-
Signal for updating the ambiguity function material in Chap. 8.
I remain indebted to those at the Applied Physics Laboratory who
assisted with the first edition, and to my colleagues during 18 years
at Technology Service Corporation where much of the new material
evolved from various programs and short courses.
I wish to thank Drs. E. K. Reedy, J. L. Eaves, and Jim Wiltse of
Georgia Tech Research Institute for their encouragement and support
in preparing this edition.
I greatly appreciate the assistance of Janice Letow for typing,
assembling, and keeping the manuscript on track.
My final thanks to the patience and understanding of my wife, Lila,
who supported me while I underestimated the effort of a new edition.
Finally, thanks to my daughter and son-in-law, and to my son who
expected me to build him a radar 20 years ago. I still do not know if I
will ever get to build him one.
xiii
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ABOUT THE AUTHOR
A specialist in radar search techniques, radar systems,
radar signal processing, and electro-optical devices, Fred E.
Nathanson has supervised laboratory and prototype search
and radar development and served with numerous
evaluation and advisory groups. He is currently Principal
Research Engineer with Georgia Tech Research Institute
in Rockville, Maryland. Mr. Nathanson holds a B.E. in
Electrical Engineering from John Hopkins University, and
an M.S. from Columbia. A Fellow of the IEEE “for
contributions to radar systems” and a member of the Radar
Systems Panel, he has published many technical articles
and taught intensive short courses worldwide.
Preface
The first version of this book was written in the late 1960s. At that
time the relationships between the radar waveform, the carrier
frequency, the signal processing, and the environment were understood
well enough to project some highly capable systems. The digital age
was just beginning, but implementation was still cumbersome and
expensive. During the late 1970s and early 1980s a number of
sophisticated but highly successful radars were developed using the
knowledge of the environment to select the waveforms and taking
advantage of the rapid progress in digital technology.
As the 1980s evolved, radar was beginning to be called a mature
technology until the Exocet missile, “stealth targets, sophisticated
electronic countersurveillance measures (ECM), drug interdiction
requirements, etc., demanded a new look at radar design and
technology. This in turn requires further knowledge of the details of
target reflectivity, natural clutter and clutter artifacts, and a radar’s
susceptibility to electronic interference. The potential of remote sensing
and space-based radars also requires a better understanding of the
environment and signal processing.
Thus the emphasis of this book is on radar design to cope with the
“total environment” rather than any single performance goal. The total
enuzronrnent, as defined here, includes the unwanted reflections from
the sea, land areas, precipitation, and chaff, as well as thermal noise
and jamming. It also recognizes that mapping, weather sensing, terrain
avoidance, altimetry, etc., may be designed for a single-function radar
or as modes of a multifunction radar.
As in the first edition, the book is divided into three parts. The first
four chapters contain an introduction to radar; expanded material on
the fundamentals of antennas, transmitters, multipath and ducting
problems; and a review of the radar equations for the detection of
targets in the presence of noise and natural and man-made interference.
This is followed by descriptions of the statistics of target detection and
the techniques for obtaining automatic detection with considerable new
material on advanced constant false alarm techniques and track-
before-detect.
xi
xii Preface
Chapter 5 contains a mostly new and thorough survey and analysis
of the available material on the reflectivity of both natural and man-
made targets. It includes the spectral, polarization, and wavelength
properties since they all have been shown to have a substantial effect
on the choice of processing technique. Chapter 6 contains greatly
expanded material on propagation and the reflectivity from
precipitation and chaff. This includes statistics on their occurrence,
carrier-frequency selection, and frequency-agility effects, wind shear
phenomena, the bright band, anomalous echoes, etc. with statistical
descriptors to evaluate signal-processing techniques. Chapter 7 follows
in the same format to describe sea and land clutter with new models,
and statistical descriptions that must be included when analyzing high-
resolution radar detection of low-flying targets. Reflectivity is related
to carrier frequency, polarization, and ducting effects. Bistatic data are
included.
Chapters 8 through 13 contain descriptions of the various signal-
processing techniques that are widely used or proposed for future radar
systems. After a general discussion of processing concepts, specific
techniques are discussed for the detection of moving targets by use of
the Doppler effect (CW, MTI, pulse Doppler), FFTs, and fast convolvers
and the pulse compression techniques (phase-coding, frequency-coding,
and linear FM). In most of these signal-processing chapters there is a
discussion of the theory of operation, and diagrams of typical processors
with emphasis on the new digital implementations and the limitations
and losses. The equations for performance evaluation, along with
advantages and disadvantages of each technique, are generally
included.
Chapter 14 describes some newer or more specialized techniques
such as the moving target detector (MTD) and clutter maps; ground,
airborne, and space-based meteorological radars often using pulse-pair
processors; and surveillance radars on aerostats. The final section
contains a description on how to analyze or simulate coherent radars
including the limitations and related loss terms.
It is not suggested that there is an optimum radar or even a generally
optimum waveform, but that in the impending era of adaptive radar,
the radar will sense the environment and adapt to this information.
While not specifically written as a textbook, the earlier edition was
used for a number of graduate courses on radar and in many intensive
short courses. An attempt has been made to better organize the
material, while retaining the chapter structure for those familiar with
the first edition. Supplementary material and further derivations are
available in the 800 references.
Fred E. Nathanson
Contents
Preface xi
Acknowledgments xiii
Chapter 1. Radar and Its Composite Environment 1
F. E. Nathanson and J. P. Reilly
1.1 Radar Functions and Applications 1
1.2 Evolution of Radar Signal Processing 3
1.3 Radar and the Radar Equation 5
1.4 Functions of Various Types of Radar 9
1.5 Target-Detection Radars for Aircraft, Missiles, and Satellites 11
1.6 Radar Frequency Bands and Carrier Selection 17
1.7 Surface and Low-Altitude Target Detection 21
1.8 Criteria for Choice of Signal-Processing Techniques 24
1.9 Antenna and Array Considerations 26
1.10 Transmitters 31
1.11 Radar Grazing Angle for Refractive Conditions-?4 Earth
Approximation 33
1.12 Forward-Scatter Effects 41
Chapter 2. Review of Radar Range Performance Computations 49
F. E. Nathanson and J. P. Reilly
2.1 General Radar Range Equation 49
2.2 Radar Detection with Noise Jamming or Interference 60
2.3 Beacon and Repeater Equations 64
2.4 Bistatic Radar 65
2.5 Radar Detection Equations in Distributed Clutter (Volume Reflectors)
for Pulse Radars 67
2.6 Pulse-Radar Detection Equations for Area Clutter 71
V
vi Contents
Chapter 3. Statistical Relationships for Various
Detection Processes 77
F. E. Nathanson and J. P. Reilly
3.1 Introduction and Definitions 77
3.2 Target Detection by a Pulsed Radar 80
3.3 Additional Results of the Marcum and Swerling Analysis 83
3.4 Noncoherent Integration Losses 87
3.5 Postdetection Integration with Partially Correlated Noise 88
3.6 Independent Sampling of Clutter Echoes 95
3.7 Digital Integrators and Limits on Independent Sampling 98
3.8 Cumulative Detection of a Radar Target 99
3.9 Detection Range for an Approaching Target 101
3.10 Summary 104
Chapter 4. Automatic Detection by Nonlinear, Sequential,
and Adaptive Processes 107
F. E. Nathanson
4.1 Introduction 107
4.2 Dynamic Range Problems-STC and IAGC 109
4.3 Effects of Limiters on Target Detection 111
4.4 Effects of Interfering Signals in Systems with Limiters 113
4.5 Limiting in Pulse Compression and Pulse Doppler Systems 116
4.6 Summary of Limiter Effects 119
4.7 Sequential Detection and Track-Before-Detect Processing
(with A. Corbeil, J. DiDomizio, and R. DiDomizio) 120
4.8 Adaptive Threshold Techniques (M. Belcher) 129
4.9 Dynamic Range of Rayleigh Signals 142
4.10 Overall False Alarm Control 143
Chapter 5. Radar Targets 147
F. E. Nathanson and J. P. Reilly
5.1 General Scattering Properties-Simple Shapes 147
5.2 Polarization Scattering Matrix 153
5.3 Complex Targets-Backscatter and Distributions 165
5.4 Measured Aircraft and Missile RCS Distributions 171
5.5 Missile and Satellite Cross Sections 175
5.6 Marine Targets 178
5.7 Miscellaneous Airborne Reflections and Clear Air Echoes 184
5.8 Spectra of Radar Cross-Section Fluctuations 187
5.9 Frequency-Agility Effects on Target Detection and Tracking 198
5.10 Bistatic Radar Cross Section of Targets 208
Contents vii
Chapter 6. Atmospheric Effects, Weather, and Chaff 21 5
F. E. Nathanson and J. P. Reilly
6.1 Standard Atmospheric Attenuation 21 6
6.2 Precipitation Occurrence and Extent 21 8
6.3 Attenuation in Hydrometeors and Foliage 224
6.4 Backscatter Coefficient of Rain, Snow, and Clouds 231
6.5 Radar Precipitation Doppler Spectra 239
6.6 Frequency Correlation of Precipitation Echoes 248
6.7 Spatial Uniformity of Rain Backscatter 250
6.8 Tropospheric Refraction Effects 255
6.9 General Properties of Chaff 260
6.10 Spectra of Chaff Echoes 265
Chapter 7. Sea and Land Backscatter 269
F. E. Nathanson and J. P. Reilly
7.1 Backscatter from the Sea-Monostatic 269
7.2 Empirical Sea Backscatter Models for Low Grazing Angles 274
7.3 Sea Clutter near Vertical Incidence 281
7.4 Polarization and Wind-Direction Effects on Reflectivity 282
7.5 Spectrum of Sea Clutter Echoes 284
7.6 Spatial and Frequency Correlation of Sea Clutter 291
7.7 Short-Pulse Sea Clutter Echoes or Spikes 296
7.8 Sea Clutter under Ducting Conditions 301
7.9 Short-Range Clutter 308
7.10 Backscatter from Various Terrain Types 314
7.1 1 Composite Terrain at Low Grazing Angles 324
7.12 Composite Terrain at Mid-Angles 329
7.13 Composite Terrain-Spatial and Temporal Distributions 334
7.14 Bistatic Sea and Land Clutter 342
Chapter 8. Signal-Processing Concepts and
Waveform Design 351
F. E. Nathanson
8.1 Radar Requirements as We Approach the Year 2000 352
8.2 Matched Filters 355
8.3 The Radar Ambiguity Function 360
8.4 The Radar Environmental Diagram (with J. Patrick Reilly) 369
8.5 Optimum Waveforms for Detection in Clutter 374
8.6 Desirability of Range-Doppler Ambiguity 377
8.7 Classes of Waveforms 381
8.8 Digital Representation of Signals 383