Radar Cross Section

489 Pages·2004·19.93 MB·English

by  Knott, Eugene F., Shaeffer, John F., Tuley, Michael T.

Radar Cross Section
Second Edition
Eugene F. Knott
John F. Shaeffer
Michael T. Tuley
SCITECH
PUBLISHING, INC.
Raleigh, NC
www.scitechpub.com
© 2004 by SciTech Publishing, Inc.
Raleigh, NC 27613
This is a corrected reprinting of the 1993 edition originally published by Artech House: Boston.
All rights reserved. No part of this book may be reproduced or used in any form whatsoever without
written permission from the publisher.
Printed in the United States of America
10 9 8 7 6 5 4 3 21
ISBN: 1-891121-25-1
SciTech books may be purchased at quantity discounts for educational, business, or sales
promotional use. For information contact the publisher:
SciTech Publishing, Inc.
Raleigh, NC 27613
[phone]
www.scitechpub.com
Library of Congress Cataloging-in-Publication Data
Knott, Eugene F.
Radar cross section / Eugene Knott, John Shaeffer, Michael Tuley—2nd ed.
ISBN 1-891121-25-1
1. Radar. I. Shaeffer, John F. II. Tuley, Michael T.
TK6580.K56 2004 92-37802
621.3848—dc20 CIP
Preface to the Second Edition
We noted in our preface to the first edition of this book that advances in both
prediction and measurement technology had moved steadily forward over the years,
and would continue to do so. The accuracy of the latter forecast, and the fact that
the book continues to be an essential part of Georgia Tech's short course on radar
cross section reduction, impelled us to undertake a revision. The revision reflects
what we learned about readers' needs and interests in the presentation of the short
course.
Readers familiar with the first edition will discover that material of marginal
interest has been purged to make room for more useful information and that a
significant amount of new material has been added, some of which is published
here for the first time. The result is that the second edition is some 20% fatter
than the first.
Some of the revisionary work amounted to a mere shifting of information
from one place in the book to another, with no net change in content. The im-
provement of existing illustrations throughout the book and the exploitation of
modern printing technology similarly brought about little net change in content,
but the reader will see that the book is now much easier to read. Nevertheless,
new illustrations and a great deal of new information have been added.
In response to reader demand, we shifted the discussion of basic relationships
from other chapters to Chapter 1. Although the information in Chapters 2 and 3
is essentially the same as that in the first edition, we have given the material
somewhat different emphasis. We present in Chapter 4 new (and more) examples
of field distributions and RCS predictions as obtained by means of the method of
moments. We include in Chapter 5 an analysis of traveling wave lobes that shows
how the errors in two separate approximations tend to cancel each other for a
nearly perfect result. Chapter 6 has been completely rewritten, including a novel
chart comparing the creeping wave echoes of metal spheres, cylinders, and circular
disks.
Chapter 7 now includes some of the practical considerations (dos and don'ts)
of planform shaping to reduce target echoes. By deleting marginally useful material
on absorbers, we were able to compress the former Chapters 8 and 9 into a single
Chapter 8 and at the same time provide significantly more material on nonspecular
absorbers. The revised Chapter 9 is essentially the former Chapter 10, with a bit
more analysis of transmission line measurements of absorber samples. Chapter 10
is completely new, treating the problem of reducing the echoes from antennas, for
which the frequency-selective surface is but one approach.
We have expanded Chapter 11 to include a section on the calibration of RCS
measurements. In the revised Chapter 12 we explain why the antennas of an
outdoor ground-plane test range may almost always be aimed along a local hori-
zontal, and not upward toward the test object. Chapter 13 now contains a discussion
of the compact range, an indoor RCS test facility that emulates a free-space (plane
wave) test environment in very short distance. Chapter 14 has been expanded to
include examples of radar imagery derived from coherent measurements of test
objects.
Eugene F. Knott
John F. Shaeffer
Michael T. Tuley
September 1992
Preface to the First Edition
The term radar cross section, and its acronym RCS, is familiar to most scientists
and engineers involved in radar systems, but to others it may seem to be an obscure
characteristic of a body or target scanned by a radar beam. They have somehow
learned or heard that this strange area is not necessarily the geometrical cross
section of the body; if not, then what is it? The name radar itself may even evoke
memories of difficult electromagnetic courses taken in college and therefore, for
some, the concept of radar cross section is mysterious and elusive.
In order to acquaint scientists and engineers who may be competent in their
own disciplines with a seemingly new and unfamiliar technology, Georgia Tech
introduced a short course on radar cross section reduction in January 1983. The
course focused not only on what radar cross section is, but how to reduce it as
well. Accompanying the formal lectures was a set of course notes numbering over
700 pages. This book is an outgrowth of those notes.
As the reader will perceive, the book is not intended as an exhaustive survey
or treatise. Such would defeat our purpose of exposing the novice to what can
quickly become a very complicated subject. For those who wish to pursue the
subject in more detail, several books are available that delve into the intricacies
of prediction and measurement techniques. In addition, many of these books are
classics, giving far more information than is included here. The reader will find
many of these books and papers listed in the references at the end of each chapter.
In addressing our purpose of presenting the flavor of RCS, if not its intricacies,
we have organized the book into five groups of chapters. Chapters 1 and 2 contain
background information; Chapters 3 through 5 introduce the concept of scattering
and present useful RCS prediction techniques; Chapter 6 displays examples of RCS
behavior for simple and complex bodies; Chapters 7 through 9 address radar cross
section reduction methods; Chapters 10 through 13 discuss techniques for mea-
suring absorber properties and the scattering characteristics of test targets; and
Chapter 14 examines practical ways to identify scattering mechanisms on complex
targets.
The reader should appreciate that technological advances have been steady
in this field, and will continue to be so, and that even during publication of this
book measurement and prediction techniques are being improved and modified.
Moreover, in the interest of national security, some aspects of radar cross section
measurement, prediction, and reduction cannot be presented here. Therefore, the
book is not as detailed nor as complete as the authors would have preferred.
Nevertheless, we think that it fills a need in the engineering community. We hope
the reader agrees.
Eugene F. Knott
John F. Shaeffer
Michael T. Tuley
June 1985
Radar Cross Section
Second Edition
Eugene F. Knott
John F. Shaeffer
Michael T. Tuley
SCITECH
PUBLISHING, INC.
Raleigh, NC
www.scitechpub.com
© 2004 by SciTech Publishing, Inc.
Raleigh, NC 27613
This is a corrected reprinting of the 1993 edition originally published by Artech House: Boston.
All rights reserved. No part of this book may be reproduced or used in any form whatsoever without
written permission from the publisher.
Printed in the United States of America
10 9 8 7 6 5 4 3 21
ISBN: 1-891121-25-1
SciTech books may be purchased at quantity discounts for educational, business, or sales
promotional use. For information contact the publisher:
SciTech Publishing, Inc.
Raleigh, NC 27613
[phone]
www.scitechpub.com
Library of Congress Cataloging-in-Publication Data
Knott, Eugene F.
Radar cross section / Eugene Knott, John Shaeffer, Michael Tuley—2nd ed.
ISBN 1-891121-25-1
1. Radar. I. Shaeffer, John F. II. Tuley, Michael T.
TK6580.K56 2004 92-37802
621.3848—dc20 CIP
Preface to the Second Edition
We noted in our preface to the first edition of this book that advances in both
prediction and measurement technology had moved steadily forward over the years,
and would continue to do so. The accuracy of the latter forecast, and the fact that
the book continues to be an essential part of Georgia Tech's short course on radar
cross section reduction, impelled us to undertake a revision. The revision reflects
what we learned about readers' needs and interests in the presentation of the short
course.
Readers familiar with the first edition will discover that material of marginal
interest has been purged to make room for more useful information and that a
significant amount of new material has been added, some of which is published
here for the first time. The result is that the second edition is some 20% fatter
than the first.
Some of the revisionary work amounted to a mere shifting of information
from one place in the book to another, with no net change in content. The im-
provement of existing illustrations throughout the book and the exploitation of
modern printing technology similarly brought about little net change in content,
but the reader will see that the book is now much easier to read. Nevertheless,
new illustrations and a great deal of new information have been added.
In response to reader demand, we shifted the discussion of basic relationships
from other chapters to Chapter 1. Although the information in Chapters 2 and 3
is essentially the same as that in the first edition, we have given the material
somewhat different emphasis. We present in Chapter 4 new (and more) examples
of field distributions and RCS predictions as obtained by means of the method of
moments. We include in Chapter 5 an analysis of traveling wave lobes that shows
how the errors in two separate approximations tend to cancel each other for a
nearly perfect result. Chapter 6 has been completely rewritten, including a novel
chart comparing the creeping wave echoes of metal spheres, cylinders, and circular
disks.
Chapter 7 now includes some of the practical considerations (dos and don'ts)
of planform shaping to reduce target echoes. By deleting marginally useful material
on absorbers, we were able to compress the former Chapters 8 and 9 into a single
Chapter 8 and at the same time provide significantly more material on nonspecular
absorbers. The revised Chapter 9 is essentially the former Chapter 10, with a bit
more analysis of transmission line measurements of absorber samples. Chapter 10
is completely new, treating the problem of reducing the echoes from antennas, for
which the frequency-selective surface is but one approach.
We have expanded Chapter 11 to include a section on the calibration of RCS
measurements. In the revised Chapter 12 we explain why the antennas of an
outdoor ground-plane test range may almost always be aimed along a local hori-
zontal, and not upward toward the test object. Chapter 13 now contains a discussion
of the compact range, an indoor RCS test facility that emulates a free-space (plane
wave) test environment in very short distance. Chapter 14 has been expanded to
include examples of radar imagery derived from coherent measurements of test
objects.
Eugene F. Knott
John F. Shaeffer
Michael T. Tuley
September 1992