Advances in Bistatic Radar

522 Pages·2007·8.751 MB·English

by  Willis, Nicholas J., Griffiths, Hugh D.(eds.)

Advances in
Bistatic Radar
Edited by
Nicholas J. Willis
and
Hugh D. Griffi ths
SciTech Publishing, Inc
Raleigh, NC
www.scitechpub.com
©2007 SciTech Publishing, Inc.
All rights reserved. No part of this book may be reproduced or used in any form whatsoever
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Library of Congress Cataloging-in-Publication Data.
Advances in bistatic radar / edited by Nicholas J. Willis, Hugh D. Griffi ths.
p. cm.
Includes bibliographical references.
ISBN-13: 978-1-891121-48-7 (hbk. : alk. paper)
ISBN-10: 1-891121-48-0 (hbk. : alk. paper)
1. Bistatic radar. I. Willis, Nicholas J., 1934- II. Griffi ths, H. (Hugh), 1956-
TK6592.B57A38 2007
621.3848--dc22
2007013159
Preface
When embarking on a project to edit or write a book, one has to be persuaded of the justifi cation
for such an enterprise. Of course, it is ultimately satisfying and enjoyable to see the fi nished
product; however, it inevitably takes more time and effort than originally foreseen. In the course
of the work, one’s knowledge of the subject advances, too.
But it is also necessary to be convinced that there is a need for such a book. In this case, interest
in bistatic radar over the past decade has been signifi cant. We have observed that interest has
varied cyclically, with a period of 15–20 years. The very fi rst radars were bistatic, until pulsed
waveforms and T/R switches were invented. Interest was revived in the 1950s with semi-active
homing missiles and the SPASUR system, and then died away. The second resurgence occurred
in the 1970s with planetary exploration and continued with air surveillance systems and the
fi rst experiments in passive bistatic radar using broadcast transmitters of opportunity. The third
resurgence started in the mid-1990s and continues, with persuasive reasons.
The consequences of Moore’s law mean that digital processing power, which is essential to
realize practical systems, especially multistatic systems, increases inexorably. The advent of GPS
solves many stressing problems of bistatic timing and synchronization. Consequently, bistatic
systems may be able to address new military surveillance requirements such as the detection and
tracking of low-signature targets by passive bistatic radars and of ground targets from unmanned
air vehicles. And, of equal signifi cance, bistatic radar continues to be used for civil applications such
as planetary surface exploration, ionospheric turbulence measurements, and three-dimensional
vector wind fi eld measurements.
The principal reason for this book, then, is to report recent work in this third resurgence. A
second reason is that a signifi cant number of publications on systems developed in past decades
have recently been declassifi ed, and can now be reported in the open literature.
The book is divided into two sections: the fi rst part documents both new and resurrected
information about the development, testing, and fi elding of bistatic and multistatic radar systems
for military, scientifi c, and commercial use; the second part updates and publishes the previously
limited bistatic clutter database and its analysis, and reports the development of (i) image focusing
and motion compensation methods for bistatic SAR and (ii) adaptive cancellation methods for
bistatic MTI.
This book evolved from the bistatic SAR material contained herein that was fi rst proposed to
SciTech Publishing by Brian Rigling as a stand-alone monograph. Subsequent SciTech-requested
reviews by Nicholas Willis (author of Bistatic Radar) and Hugh Griffi ths (editor of the IET’s Special
Issue on Bistatic Radar) led to the conclusion that bistatic SAR was one of many signifi cant bistatic
and multistatic radar developments occurring in the third resurgence, which should logically be
assembled in a full report to the radar community. Dr. Rigling graciously deferred in having his
monograph subsumed by the larger effort. Thus began the search, solicitation, and confi rmation
of a remarkable group of experts on the subject. With both surprise and satisfaction, we can say
that the sustained efforts of authors, contributors, editors, and the publisher brought forth this
book in less than two years’ time.
The writing and editing of this book has been constrained by the fact that the two coeditors
are separated by eight time zones, so the work has necessarily been done via the Internet and
e-mail, which we can report worked splendidly. We are indebted to our families—particularly
our wives, Carlaine and Morag—for their forbearance, when we may have appeared to be too
Preface xiii
engrossed in our work to give them the time and attention that they deserve. We thank all authors
and contributors for producing their material, often to tight deadlines, and for accepting our
edits with good grace. We thank the numerous people who have helped us by providing material,
assisting with experimental work, and constructively reviewing early drafts of the manuscript.
It is always invidious to mention individuals since we are bound to offend by omission, but we
are grateful particularly to Anthony Andrews, Chris Baker, Alan Bernard, Paul Howland, Daniel
O’Hagan, Marc Thomas, and M. C. Jackson, who truly codifi ed bistatic radar analysis. Finally we
gratefully acknowledge the encouragement and support of SciTech’s CEO, Dudley Kay, and Chief
Editor, Susan Manning, in enabling and executing this project.
Hugh Griffi ths
London, England
Nicholas Willis
Carmel, California
February 2007
PUBLISHER’S NOTE:
Additional fi les, errata, and commentary—including full color versions of many of the fi gures in the text—can be found at
the companion website www.scitechpub.com/willisgriffi ths.htm.
Contents
Foreword xi
Preface xii
Chapter 1 Introduction 3
1.1 Defi nitions 3
1.2 Applications 3
1.3 Purpose, Scope, and a Little History 4
1.4 Summary 5
References 8
Part I Bistatic/Multistatic Radar Systems
Chapter 2 History Update 10
2.1 Beginnings 10
2.2 First Resurgence 22
2.3 Second Resurgence 23
2.4 Third Resurgence 27
References 30
Chapter 3 Fluttar DEW-Line Gap-Filler 35
3.1 Background 35
3.2 Early Thoughts About a Dew Line Bistatic Gap-Filler Radar 36
3.3 Fluttar System Considerations 39
3.4 Unexpected Trouble 43
3.5 Monostatic Pulse Radar for Fence Coverage 45
3.6 Looking Back 45
References 46
Chapter 4 Missile Attack Warning 47
4.1 Introduction 47
4.2 HF–VHF/UHF Radar Relationships 47
4.3 440-L Forward-Scatter OTH Bistatic Radar 52
4.4 Sugar Tree OTH Passive Bistatic Radar 54
References 54
Chapter 5 Planetary Exploration 56
5.1 Introduction 56
5.2 Principles of Operation 61
5.3 Polarization Measurements 66
5.4 Coherent Backscatter Opposition Effect and the Search for Lunar
Water Ice 69
5.5 Transient Surface Echoes at Occultation 70
viii Contents
5.6 Uplink Bistatic Radar 72
5.7 Recapitulation and Future Experiments 73
References 75
Chapter 6 Air Surveillance 78
6.1 Introduction 78
6.2 PBR Review 80
6.3 Military Utility 91
6.4 Waveforms and Interference 105
6.5 Range Performance 124
6.6 Target Location 140
6.7 Electronic Countermeasures 172
Appendix 6-A: A Review of UHF/VHF Monostatic and Bistatic Radar Cross-
Section Data 180
Appendix 6-B: List of Symbols 183
References 187
Chapter 7 Ionospheric Measurements 193
7.1 Introduction 193
7.2 Field-Aligned Irregularities 194
7.3 Detection of FAI with Passive Radar 199
7.4 System Engineering Issues 204
7.5 Future Plans 208
Acknowledgements 209
References 209
Chapter 8 Wind Measurements 212
8.1 Introduction 212
8.2 Existing Radar Methods for Retrieving Vector Winds 213
8.3 System Theory 214
8.4 System Characteristics and Design Trade-Offs 216
8.5 Test Results 222
References 228
Part II Bistatic Clutter and Signal Processing
Chapter 9 Clutter 230
9.1 Introduction and Summary 230
9.2 System Parameters and Properties 232
9.3 Clutter Cross-Section Per Unit Area 240
Acknowledgements 307
Appendix 9–A Aperture Diffraction Theory (Survey) 309
A.1 Summary 309
A.2 Overview 309
A.3 Analysis 310
Appendix 9–B Annotated List of Symbols 314
References 317
Contents ix
Chapter 10 Spotlight Synthetic Aperture Radar 320
10.1 Bistatic Phase History Data 323
10.2 Image Resolution 328
10.3 Frequency Sample Data Collection 335
10.4 Bistatic SAR Image Formation 352
10.5 Motion Measurement Errors 370
10.6 Autofocus 385
10.7 Three-Dimensional Surface Reconstruction 410
10.8 Properties of Bistatic SAR Images 419
References 426
Chapter 11 Adaptive Moving Target Indication 432
11.1 Overview 432
11.2 Bistatic Moving Target Indication 437
11.3 Bistatic Clutter Angle–Doppler Response 449
11.4 Adaptive Bistatic Clutter Cancellation Methods 455
11.5 Bistatic STAP Performance Characteristics 469
11.6 Summary 477
References 479
Contributors 482
Index 486
1
Introduction
Nicholas J. Willis
1.1 DEFINITIONS
A bistatic radar is a radar that uses two antennas at separate locations, one for transmission and
one for reception. Usually the transmitter and receiver accompany the antennas at these locations.
A variation of the bistatic radar is the multistatic radar, which uses multiple antennas at separate
locations, one antenna for transmission and multiple antennas at a different location, for reception,
or vice versa. Again, transmitters or receivers can accompany the antennas. Multistatic radar
can use multilateration for target state estimates (i.e., target position, velocity, and acceleration).
Multilateration combines simultaneous range and/or doppler data from multiple transmitter/
receiver pairs having overlapping spatial coverage to estimate the target state without using range-
dependent angle data.
Bistatic (and multistatic) radars can operate with their own dedicated transmitters, which
are specially designed for bistatic operation, or with transmitters of opportunity, which are
designed for other purposes but can be suitable for bistatic operation. When the transmitter
of opportunity is from a monostatic radar, the bistatic radar is often called a hitchhiker. When
the transmitter of opportunity is from—sources other than a radar, such as a broadcast station
or communications link, the bistatic radar can also be referred to as passive radar, passive
coherent location, parasitic radar, and piggyback radar. In this book it is called passive bistatic
radar (PBR), with piggyback radar used to refer to planetary exploration in recognition of
their independent development. Finally, transmitters of opportunity in military scenarios
can be designated as either cooperative or noncooperative, where cooperative denotes an allied
or friendly transmitter and noncooperative denotes a hostile or neutral transmitter. PBR
operations are more restricted when using the latter.
1.2 APPLICATIONS
In nearly all cases of bistatic and multistatic operation, antenna separation is selected to achieve
an operational, technical, or cost benefi t and is usually a signifi cant fraction of the target range.
One operational benefi t is to covertly exploit a noncooperative surveillance radar transmitter for
surveillance. A classic example is the German Klein-Heidelberg-Parasit hitchhiking off of the British
Chain Home radars in World War II to warn of Allied bombing raids from England. A second
operational benefi t is to have an air-to-ground attack aircraft hitchhike off a cooperative, standoff,
monostatic radar when penetrating the radar-illuminated target area in radio frequency silence.
3
4 Introduction
Other transmitters of opportunity illuminating the target area might also be exploited. Another
operational benefi t is to counter retrodirective jammers and radar cross-section cancellation
techniques that retransmit the incident radar signal back to the transmitter, which is now separate
from the receiver.
A technical benefi t is to improve target location accuracy with a multistatic radar operating
in a multilateration confi guration when geometric dilution of precision conditions are favorable.
Examples of two such applications are improving the accuracy of range instrumentation systems
and tracking ballistic missile launches. Another technical benefi t is to combine vector wind
fi eld measurements from a monostatic doppler weather radar and multiple bistatic receivers
hitchhiking off of the monostatic radar to provide an accurate estimate of the full vector wind
fi eld. Semiactive homing missile accuracy during endgame can also be improved by increasing
the bistatic angle, which reduces target glint.
Cost benefi ts include piggybacking on existing satellite data link transmitters for planetary
exploration and exploiting terrestrial broadcast transmitters for ionospheric measurements, as
does the Manastash Ridge Radar. Also, very high transmitter power can be provided at the lowest
cost by a continuous wave (CW) transmitter, which in turn requires spatial isolation from the
receiver, conveniently provided by bistatic operation. The space surveillance systems SPASUR
and Graves use this approach.
Finally, a combined operational, technical, and cost benefi t is to use a multistatic PBR to exploit
for example, a commercial FM broadcast station for military air surveillance. This confi guration
can (a) operate both covertly and in the resonance region of most air vehicles, including stealthy
air vehicles, where target radar cross section is enhanced; (b) generate accurate location estimates
(in two dimensions) via multilateration; and (c) eliminate the cost of the transmitter and associated
equipment. However, these benefi ts come with both technical and operational limitations, which
are detailed subsequently.
While these types of benefi ts are both credible and useful, they remain niche applications
when compared to the ubiquitous capabilities of monostatic radars, which remain the paramount
method for radio detection and ranging.
1.3 PURPOSE, SCOPE, AND HISTORY
The history of bistatic and multistatic radars is well documented [1–15]. However, a brief summary
will be provided here to establish the purpose and scope of this book. With a nod to Christian
Hülsmeyer’s early 1904 telemobilskop demonstrations, all radar observations and experiments in the
1920s and early 1930s were of the bistatic type. Many countries deployed CW bistatic radars in
a fence confi guration primarily for air-defense alerting and cueing prior to and during World
War II. With the advent of pulsed operation and the duplexer in the late 1930s, the monostatic
radar, with its single-site operational advantage, became the confi guration of choice and all bistatic
radar work ended after World War II.
Since then, bistatic and multistatic radars have had periodic resurgences when a specifi c bistatic
application was found attractive or when the concept was simply rediscovered. That observation
was made in 1991 [12], which documented two such resurgences. The fi rst started in the 1950s,
when (a) tactical semiactive homing missiles, (b) bistatic fences for air defense and ballistic missile
launch warning, and (c) multistatic radars for test range instrumentation and satellite tracking
were developed and deployed. Both the tactical missiles and satellite trackers remain operational.
The second resurgence began in the late 1960s when data link transmitters on satellites and
ground-based receivers were used for moon and planetary surface measurements in ten missions
over a span of 40 years (That work is ongoing, and now includes ground-based transmitters and
Summary 5
receivers on satellites.) A multistatic radar hitchhiker, called the Multistatic Measurement System,
was deployed on a ballistic missile test range to improve the measurement accuracy of reentry
vehicles. It was fi nally retired after signifi cant improvements were made to the monostatic radars.
In contrast, other bistatic radar concepts were developed and tested, but not deployed, to counter
the new, antiradiation missile and emitter locator threats. The bistatic fence was redeveloped and
tested to protect high-value ground targets, but not deployed. Willis [12] then concluded the
introduction to his history chapter with:
This chapter details bistatic radar history in an attempt to illuminate… special, potentially worthwhile
bistatic [and multistatic] applications as well as bistatic “dead ends,” and to ease the process of rediscovery
in the next resurgence cycle.
We are well into that next cycle, which establishes the purpose of this book: to report events in the
third resurgence. These events are divided into two parts:
Part 1: Bistatic/Multistatic Radar Systems, which documents both resurrected and new infor-
mation about the development, testing, and fi elding of bistatic and multistatic radar sys-
tems for military, scientifi c, and/or commercial use in approximate chronological order.
Part 2: Bistatic Clutter and Signal Processing, which updates and publishes the previously
restricted bistatic clutter database and its analysis, and reports (a) the development
of autofocus and image formation methods to improve bistatic synthetic aperture
radar (SAR) performance and (b) the development of adaptive cancellation methods
to improve bistatic moving target indication (MTI) performance.
1.4 SUMMARY
The following summarizes events occurring in the third resurgence, outlined in the table of
contents.
Part 1: Bistatic/Multistatic Radar Systems
Chapter 2: History Update As usually happens during continuing and even intermittent radar de-
velopments over many years, old information is released and new information from earlier events
surfaces.1 Such is the case for bistatic radars and that information is reported by Nicholas J. Willis
in this chapter as an update to Chapter 2. The update includes new information on some very old
bistatic radars, including Christian Hülsmeyer’s 1904 telemobilskop, the World War II Japanese
Type A fence, and the German Klein-Heidelberg-Parasit, along with some obscure British Chain
Home bistatic and multistatic radar modes.
Information on bistatic radars developed in the fi rst resurgence, including the AN/FPS-23
Fluttar and 440-L, has now been released and is the subject of Chapters 3 and 4. An example of
bistatic glint reduction for semiactive homing missiles surfaced along with new information on
bistatic radar developments in the United Kingdom and the United States during the second
resurgence. Finally, all available information is summarized on bistatic radar developments during
the third resurgence.
Chapter 3: Fluttar DEW-Line Gap-Filler Fluttar was an experimental bistatic radar developed by
MIT Lincoln Laboratory in the 1950s which led to the AN/FPS-23, the fi rst operational bistatic
radar deployed by the United States. It was used in the Distant Early Warning (DEW) Line as a
1 O ften the new information surfaces after publishing a book or giving a lecture, which triggers a memory from some
reader or listener. That person then approaches the author with the new data, which in turn restarts the documenta-
tion cycle. This happened many times to the editors, with many thanks for the offerings.