Book review: Adaptive Array Principles

polarisations, for the scattered field set up by the reflector at a general point in space. The power coupled from the scattered field into an appropriately polarised feed has been used to derive directive gain functions for both polarisations. A more general gain expression has also been derived where a feed of arbitrary polarisation is considered. Three applications of the presented analysis have been given that yield quantitative information on the accuracy of the directive gain equations derived. These applications should enable their suitability for analysing a wide range of reflector-antenna problems to be assessed. 5

Acknowledgments

The author would like to thank Mr. F.W. Robinson for supplying the data for Figs. 10 and 11. This work has been partly carried out with the support of the UK Procurement Executive Ministry of Defence. Permission for publication by Thorn EMI Electronics Ltd. is also gratefully acknowledged.

6

References

1 SILVER, S.: 'Microwave antenna theory and design' (McGraw-Hill, 1949), pp. 144-149 2 COLLIN, R.E., and ZUCKER, F.J.: 'Antenna theory - Pt. 1' (McGraw-Hill, 1969), pp. 61-79 3 RATNASIRI, P.A.J., KOUYOUMJIAN, R.G., and PATHAK, P.H.: The wide angle side lobes of reflector antennas'. Technical Report 2183-1, March 1970, Ohio State University, Ohio, USA 4 CLARRICOATS, P.J.B.: 'Some recent advances in microwave reflector antennas', Proc. IEE, 1979, 126 (1), pp. 9-25 5 KINZEL, J.A.: 'Large reflector antenna pattern computation using moment methods', IEEE Trans., 1974, AP-22, pp. 116-118 6 KILDAL, P., and S0RNGARD, E.: 'Circularly polarised feed for cylindrical parabolic reflector antennas', ibid., 1980, AP-28, pp. 210-215 7 McLACHLAN, N.W.: 'Bessel functions for engineers', (Oxford University Press, 1955) p. 18 8 KRAUS, J.D.: 'Antennas' (McGraw-Hill, 1950), Chap.3 9 RUSCH, W.V.T., and POTTER, P.D.: 'Analysis of reflector antennas' (Academic Press, 1970), pp. 61-65 10 JORDAN, E.C., and BALMAIN, K.G.: 'Electromagnetic waves and radiating systems' (Prentice-Hall, 1968), 2nd edn., pp. 470-479

Book Review Adaptive array principles

J. E Hudson Peter Peregrin us Limited, 1981, 253pp., £26.50 (UK), $77.00 (USA), £31.00 (Elsewhere) ISBN: 0-9060-48-55-9

An adaptive array is an antenna system whose polar diagram is adjusted automatically to improve signal reception in the presence of unwanted noise or interference. Optimisation is achieved by applying attenuation and/or phase adjustment to elements or groups of elements within the array. These weighting coefficients are derived using online adaptive algorithms which take the form of either closed-loop or openloop techniques. Recent advances in analogue and digital technology are now beginning to provide cost-effective realtime implementations in modern radar, sonar and communication systems. Although, the practical problems associated with the various applications and implementations are different, the basic underlying theory is much the same. The open literature is densely populated with publications on this subject, but there exist very few good introductory reference text books on the subject. This book is divided into seven chapters. Chapter 1 provides the beginner with a brief rudimentary introduction to the concepts of beam forming and null steering. Numerical examples are used successfully in a tutorial fashion to clarify and extend the ideas presented in the main text. Chapter 2 describes the method of analytic signal representation and

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contains a summary of relevant matrix-algebra techniques. Chapter 3 defines theoretical performance limits and develops the classical Wiener-Hopf solution. Chapters 4 and 5 describe both the underlying mathematics and system performance aspects of several adaption algorithms. The discussion is limited to narrow-band adaptive arrays and includes comprehensive descriptions of gradient methods (based on both correlation and perturbation techniques), sample matrix inversion, recursive matrix inversion and cascade network techniques. The methods of accelerated gradient convergence are mentioned only briefly in the text. Main lobe constraints and suboptimal array processing techniques are discussed in some detail in chapters 6 and 7, respectively. In this book the author has collated a mass of information scattered throughout the literature. The text provides a comprehensive survey of narrow-band gradient-based adaptivearray techniques and includes detailed discussions of some additional selected topics, less adequately covered in the literature. The mathematics is clear and relatively easy to follow. Numerical examples and diagrams are used extensively to both illustrate and extend the material of the main text. In summary, this book is well presented and highly recommended as a reference text for practising engineers and scientists with an active interest in the theory and techniques of adaptive signal processing. P.J.BALDWIN

IEE PROC, Vol. 129, Pt. H, No. 5, OCTOBER 1982