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Reviewer: Tim Pratt

This book is intended for people who work in the general area of signal processing and are unfamiliar with radar techniques. Computer scientists will find the book especially valuable, as it covers topics that extend beyond synthetic aperture radar (SAR) and emphasizes algorithms and signal processing methods that are used to generate visual images from digital data. The title of the book could more accurately have been Signal processing techniques for synthetic aperture radar. The brief discussion of radars is barely adequate to provide a general understanding of how radars work and is confined almost exclusively to pulse compression radar using linear frequency sweep (chirp). Throughout the book, the SEASAT synthetic aperture radar carried by an orbiting satellite is used as a model and example for the algorithms used in processing SAR data. The text is heavily weighted toward processing techniques (the approach is essentially derived from the mathematics of image generation), but it does provide a good description of how an SAR collects data. After providing a brief description of how a radar measures target range and signature, chapter 1 moves quickly to a mathematical description of the signal processing techniques needed to image SAR data. The reader is assumed to be familiar with such techniques as autocorrelation, cross-correlation, Fourier transform, DFT, and FFT. Chapter 2 describes the methods used to reduce data collected by an SAR to a pictorial image of the scene surveyed. This description adequately covers the constraints of finite aperture size, target motion, antenna characteristics, and target signature. Because the book uses satellite-borne SAR as its primary example, it does not cover the problems that arise in airborne SAR systems when the radar platform deviates from an ideal path: coherence of the transmitter is assumed throughout. This chapter contains the bulk of the material on SAR and provides a good summary of the techniques available for digital processing of SAR data. Chapter 3 examines the application of optical processing methods to the SAR problem. Recent advances in optical technology have made improved optical processors possible. The earliest SAR processors were optical, but as faster computers became available, attention moved to digital signal processing. The enormous volume of data generated by an SAR, as well as the extensive processing required to produce images, make optical processing attractive, especially for real-time applications. Chapter 4 presents some other image processing techniques similar to SAR and includes a discussion of tomography. The three appendices comprise a third of the book's length. Appendix A is a useful summary that covers the basic signal processing techniques used in the text. Appendices B and C consider matched filtering as a signal processing technique and examine its implementation by computer. Many radars use a frequency domain implementation in hardware, but this section completely ignores that possibility. This short book (only 170 pages) will disappoint the reader hoping to learn about radar. The book is primarily about processing data from synthetic radars; it is a good introduction to that subject and covers the fundamental physics of synthetic aperture radar. The book will appeal to those interested in signal processing and image processing in particular. For the person unfamiliar with the nature of radar, it does give a basis for understanding the physics of the SAR. The level of the treatment is appropriate for graduates in computer science or electrical engineering who have a background in signal processing, and the book would support a graduate-level class in imaging systems. A course on synthetic aperture radar would require additional material on radar systems. A few problems appear at the end of each chapter, and their solutions are given in an appendix. These problems are really exercises; extra material would be needed for classroom use. One disturbing feature of the book is that some of the diagrams appear to have been drawn by a computer with poor graphic resolution. Curves are represented by jagged lines, and waveforms appear noisier than they should. These imperfections detract from the appearance of the text; the distorted waveforms may even mislead the reader. The text contains a few typographical errors, but not so many as to be distracting. Overall, this book is a good introduction to its subject and should be useful to its intended readership.