阵列传感器信号处理Sensor Array Signal Processing 英文版.pdf

SENSORARRAY SIGNALPROCESSINGPrabhakar S.NaiduSENSORARRAY SIGNALPROCESSINGBoca Raton London New York Washington,D.C.CRC Press This book contains information obtained from authentic and highly regarded sources.Reprinted materialis quoted with permission,and sources are indicated.A wide variety of references are listed.Reasonableefforts have been made to publish reliable data and information,but the author and the publisher cannotassume responsibility for the validity of all materials or for the consequences of their use.Neither this book nor any part may be reproduced or transmitted in any form or by any means,electronicor mechanical,including photocopying,microfilming,and recording,or by any information storage orretrieval system,without prior permission in writing from the publisher.The consent of CRC Press LLC does not extend to copying for general distribution,for promotion,forcreating new works,or for resale.Specific permission must be obtained in writing from CRC Press LLCfor such copying.Direct all inquiries to CRC Press LLC,2000 N.W.Corporate Blvd.,Boca Raton,Florida 33431.Trademark Notice:Product or corporate names may be trademarks or registered trademarks,and areused only for identification and explanation,without intent to infringe.2001 by CRC Press LLCNo claim to original U.S.Government worksInternational Standard Book Number 0-8493-1195-0Library of Congress Card Number 00-030409Printed in the United States of America 1 2 3 4 5 6 7 8 9 0Printed on acid-free paper Library of Congress Cataloging-in-Publication Data Naidu,Prabhakar S.Sensor array signal processing/Prabhakar S.Naidu.p.cm.Includes bibliographical references and index.ISBN 0-8493-1195-0(alk.paper)1.Singal processingDigital techniques.2.Multisensor data fusion.I.Title.TK5102.9.N35 2000621.3822dc2100-030409 CIP 1195/Disclaimer Page 1 Monday,June 5,2000 3:20 PMPrologueAn array of sensors is often used in many diverse fields of science andengineering,particularly where the goal is to study propagating wavefields.Some examples are astronomy(radio astronomy),medical diagnosis,radar,communication,sonar,nonrestrictive testing,seismology,and seismicexploration(see 1 for different applications of the array signal processing).The main goal of array signal processing is to deduce the followinginformation through an analysis of wavefields:(a)Source localization as in radar,sonar,astronomy,and seismology,etc.(b)Source waveform estimation as in communication,etc.(c)Source characterization as in seismology(d)Imaging of the scattering medium as in medical diagnosis,seismicexploration,etc.The tools of array signal processing remain the same,cutting across theboundaries of different disciplines.For example,the basic tool ofbeamformation is used in many areas mentioned above.The present book aimsat unraveling the underlying basic principles of array signal processing withouta reference to any particular application.However,an attempt is made toinclude as many tools as possible from different disciplines in an order whichreflects the underlying principle.In the real world,different types of wavefields are used in differentapplications,for example,acoustic waves in sonar,mechanical waves inseismic exploration,electromagnetic waves in radar and radio astronomy.Fortunately,all wavefields can be characterized under identical mathematicalframework.This common mathematical framework is briefly summarized inchapter 1.Here we have described the basic equations underlying differentwavefields and the structure of array signals and the background noise when thenoise sources follow some simple geometrical distribution.The topics coveredare wavefield in open space,bounded space including multipath propagation andlayered medium.Also covered is the weak scattering phenomenon which is thebasis for tomographic imaging.In chapter 2 we study different types of sensorconfigurations.The emphasis is however on commonly used uniform lineararray(ULA),uniform circular array(UCA).Many practical sensor arraysystems can be studied in terms of the basic ULA and UCA systems(cylindrical array in radar and sonar,cross array in astronomy and seismology).Like sensors,the sources can also be configured in the form of an array.The 2001 by CRC Press LLCsource array is useful in synthesizing a desired wavefront and/or waveform.Inchapter 3 we examine the issues connected with the design of 2D digital filtersfor wavefield analysis.Since the propagating wavefields possess someinteresting spectral characteristics in frequency wavenumber domain,forexample,the spectrum of a propagating wavefront is always on a radial line,itis natural to take into account these features in the design of digital filters forseparation of interfering wavefields.Specifically,we cover in detail the designof a fan filter and quadrant filter.Also,the classical Wiener filter as anoptimum least squares filter is covered in this chapter.The theme in chapters 4 and 5 is localization of a source.In chapter 4we describe the classical methods based on the frequency wavenumber spectrumof the observed array output.We start with the Blackman Tukey type frequencywavenumber spectrum and then go on to modern nonlinear high resolutionspectrum analysis methods such as Capons maximum likelihood spectrumwhich is also known as minimum variance distortionless response(MVDR)beamformer and maximum entropy spectrum.Localization essentially involvesestimation of parameters pertaining to the source position,for example,azimuth and elevation angles,range,speed if the source is moving,etc.In thelast two decades a host of new methods of source localization have beeninvented.We elaborate these new approaches in chapter 5.These includesubspace based methods,use of man-made signals such as in communicationand finally multipath environment.Quite often localization must be done in thereal time and it may be necessary to track a moving source.Adaptive techniquesare best suited for such tasks.A brief discussion on adaptive approach isincluded.In chapter 6 we look into methods for source waveform separation andestimation.The direction of arrival(DOA)is assumed to be known or has beenestimated.We shall describe a Wiener filter which minimizes the mean squareerror in the estimation of the desired signal coming from a known direction anda Capon filter which,while minimizing the power,ensures that the desiredsignal is not distorted.We also talk about the estimation of direction of arrivalin a multipath environment encountered in wireless communication.The next two chapters are devoted to array processing for imagingpurposes.Firstly,in chapter 7 we look at different types of tomographicimaging systems:nondiffracting,diffracting and reflection tomography.Thereceived wavefield is inverted under the assumption of weak scattering to mapany one or more physical properties of the medium,for example,sound speedvariations in a medium.For objects of regular shape,scattering points play animportant role in geometrical diffraction theory.Estimation of these scatteringpoints for the determination of shape is also discussed.In chapter 8 we studythe method of wavefield extrapolation for imaging,extensively used in seismic 2001 by CRC Press LLCexploration.The raw seismic traces are stacked in order to produce an outputtrace from a hypothetical sensor kept close to the source(with zero-offset).Asuite of such stacked traces may be modeled as a wavefield recorded in animaginary experiment wherein small charges are placed on the reflector andexploded at the same time.The zero-offset wavefield is used for imaging ofreflectors.The imaging process may be looked upon as a downwardcontinuation of the wavefield or inverse source problem or propagationbackward in time,i.e.,depropagation to the reflector.All three view points arevery briefly described.The book is based on a course entitled“Digital Array Processing”offered to the graduate students who had already taken a course on digital signalprocessing(DSP)and a course on modern spectrum analysis(MSA).It hasbeen my conviction that a student should be exposed to all basic conceptscutting across the different disciplines without being burdened with thequestions of practical applications which are usually dealt with in specialtycourses.The most satisfying experience is that there is a common thread thatconnects seemingly different tools used in different disciplines.An example isbeamformation,a commonly used tool in radar/sonar,which has a closesimilarity with stacking used in seismic exploration.I have tried to bring outin this exposition the common thread that exists in the analysis of wavefieldsused in a wide variety of application areas.The proposed book has asignificantly different flavor,both in coverage and depth in comparison with theones on the market 1-5.The first book,edited by Haykin,is a collection ofchapters,each devoted to an application.It rapidly surveys the state of art inrespective application areas but does not go deep enough and describe the basicmathematical theory required for the understanding of array processing.Thesecond book by Ziomek is entirely devoted to array signal processing inunderwater acoustics.It covers in great depth the topic of beamformation bylinear and planar arrays but confines to linear methods.Modern array processingtools do not find a place in this book.The third book by Pillai 3 has a verynarrow scope as it deals with in great detail only the subspace based methods.The fourth book by Bouvet and Bienvenu(Eds)is again a collection of paperslargely devoted to modern subspace techniques.It is not suitable as a text.Finally,the present book has some similarities with a book by Johnson andDudgeon 3 but differs in one important respect,namely,it does not cover theapplication of arrays to imaging though a brief mention of tomography ismade.Also,the present book covers newer material which was not available atthe time of the publication of the book by Johnson and Dudgeon.During thelast two decades there has been intense research activity in the area of arraysignal processing.There have been at least two review papers summarizing the 2001 by CRC Press LLCnew results obtained during this period.The present book is not a researchmonograph but it is an advanced level text which focuses on the importantdevelopments which,the author believes,should be taught to give a broad“picture”of array signal processing.I have adopted the following plan of teaching.As the entire bookcannot be covered in one semester(about 35 hours)I preferred to cover it in twoparts in alternate semesters.In the first part,I covered chapter 1(exclude 1.6),chapter 2,chapters 4,5 and 6.In the second part,I covered chapter 1,chapter 2(exclude 2.3),chapter 3(exclude 3.5),chapters 7 and 8.Exercises are given atthe end of each chapter.(The solution guide may be obtained from thepublisher).1.S.Haykin(Ed),Array Signal Processing,Prentice Hall,Englewood Cliffs,NJ,1985.2.L.J.Ziomek,Underwater Acoustics,A Linear Systems Theory,AcademicPress,Orlando,1985.3.S.U.Pillai,Array Signal Processing,Springer-Verlag,New York,1989.4.M.Bouvet and G.Bienvenu,High Resolution Methods in UnderwaterAcoustics,Springer-Verlag,Berlin,1991.5.D.H.Johnson and D.E.Dudgeon,Array Signal Processing,Prentice Hall,Englewood Cliffs,NJ,1993.6.H.Krim and M.Viberg,Two decades of array signl processing,IEEE SignalProc.Mag.,July 1996,pp.67-94.7.T.Chen(Ed)Highlights of statistical signal and array processing,IEEESignal Proc.Mag.,pp.21-64,Sept.1998.Prabhakar S.NaiduFebruary,2000Prof,Dept of ECE,Indian Institute of Science,Bangalore 560012,India.2001 by CRC Press LLCSensor Array Signal ProcessingContentsChapter OneAn Overview of Wavefields 1.1 Types of wavefields and the governing equations 1.2 Wavefield in open space 1.3 Wavefield in bounded space 1.4 Stochastic wavefield 1.5 Multipath propagation 1.6 Propagation through random medium 1.7 Exercises Chapter TwoSensor Array Systems 2.1 Uniform linear array(ULA)2.2 Planar array 2.3 Broadband sensor array 2.4 Source and sensor arrays 2.5 Exercises Chapter ThreeFrequency Wavenumber Processing 3.1 Digital filters in the-k domain 3.2 Mapping of 1D into 2D filters 3.3 Multichannel Wiener filters 3.4 Wiener filters for ULA and UCA 3.5 Predictive noise cancellation 3.6 Exercises Chapter FourSource Localization:Frequency Wavenumber Spectrum 4.1 Frequency wavenumber spectrum 4.2 Beamformation 4.3 Capons-k spectrum 4.4 Maximum entropy-k spectrum4.5 Exercises 2001 by CRC Press LLCChapter FiveSource Localization:Subspace Methods5.1 Subspace methods(Narrowband)5.2 Subspace methods(Broadband)5.3 Coded signals5.4 Array calibration5.5 Source in bounded space5.6 ExercisesChapter SixSource Estimation6.1 Wiener filters6.2 Minimum variance(Capon method)6.3 Adaptive beamformation6.4 Beamformation with coded signals6.5 Multipath channel6.6 ExercisesChapter SevenTomographic Imaging7.1 Nondiffracting radiation7.2 Diffracting radiation7.3 Broadband illumination7.4 Reflection tomography7.5 Object shape estimation7.6 ExercisesChapter EightImaging by Wavefield Extrapolation8.1 Migration8.2 Exploding reflector model8.3 Extrapolation in-k plane8.4 Focused beam8.5 Estimation of wave speed8.6 Exercises 2001 by CRC Press LLCAcknowledgmentThe thought of formalizing the lecture notes into a text occurred to me when Iwas visiting the Rurh Universitaet,Bochum,Germany in 1996 as a HumboldtFellow.Much of the ground work was done during this period.I am grateful toAvH Foundation who supported my stay.Prof Dr.J.F Boehme was my host.Iam grateful to him for the hospitality extended to me.Many of my students,who credited the course on Array Signal Processing have contributed by way ofworking out the exercises cited in the text.I am particularly grateful to thefollowing:S.Jena,S.S.Arun,P.Sexena,P.D.Pradeep,G.Viswanath,K.Ganesh Kumar,Joby Joseph,V.Krishnagiri,N.B.Barkar.My graduatestudents,Ms.A.Vasuki and Ms.A Buvaneswari,have significantly contributedto chapter 7.Dr.K.V.S.Hari read the manuscript at an early stage and mademany constructive suggestions.I wish to thank the CRC Press Inc.,inparticular,Ms.Nora Konopka and Ms Maggie Mogck for their promptness andpatience.Finally I owe a deep gratitude to my family;my wife,Madhumati andsons Srikanth,Sridhar and Srinath for their forbearance.I must specially thankmy son,Srinath who carefully scrutinized parts of the manuscript.2001 by CRC Press LLCDedicationThis work is dedicated to the memory of the great visionary,J.R.D Tatawho shaped the Indian Institute of Science for many decades.2001 by CRC Press LLCChapter OneAn Overview of WavefieldsA sensor array is used to measure wavefields and extract information about thesources and the medium through which the wavefield propagates.It is thereforeimperative that some background in different types of wavefields and the basicequations governing the wavefield must be acquired for complete understandingof the principles of Array Signal Processing(ASP).In an idealisticenvironment of open space,homogen