cluding Carver Mead and Richard Lyon. The main strengths of this book lie in the development of the HDL together with the discussion on applications. The.
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Book Reviews Electrical machines IEE Conference Publication No.254 1985, 308pp. £33 Sales of electrical machines can be used as a leading economic indicator, because a significant fraction of any new industrial investment is in motors, large and small. An upturn in motor sales precedes by a few months a rise in industrial output. Manufacture of electrical machines is a very competitive business and the depressed economy of recent years has enhanced this competition. Manufacturers have therefore exploited new materials and advanced design techniques to cut costs and get a competitive edge. Many of these developments were reported at the IEE three-day conference in September 1985, 'Electrical machines — design and applications'. This was the second such conference sponsored by the IEE but even in the short time since the last in 1982 many novel developments have taken place. Convertor operation of machines is much in evidence and effort has been devoted to improving efficiency and controllability. The use of CAD for machine design is now widely used, as are finiteelement methods for calculating flux paths, losses, thermal fields and stresses. Many papers were devoted to techniques for protecting the asset, with condition monitoring applied either to individual components or to whole machines as a global system. The conference proceedings are a worthwhile addition to the library of the machine designer and applications engineer alike. W. FAIRNEY
Designing digital filters C. Williams Prentice-Hall 1985, 349pp. £39-55
filters'. Chapter four shows how windowing techniques can be used to turn the potentially infinite designs produced in chapter three into practical filters with a minimum of degradation of their frequency response. Four windows are covered: uniform, von Hann, Hamming and Kaiser. The z-transform, normally the starting point for the study of digital filters, finally makes an appearance in chapter five, which covers the analysis of recursive digital filters. Chapter six uses the techniques developed in chapter five for the design of recursive filters. It begins with an introduction to analogue filters, providing just enough background to help the reader understand analogue filters when they are used as a basis for designing digital filters. The rest of the chapter develops two techniques for designing recursive filters: the impulse invariant techniques and the bilinear transform. The final section, chapters seven and eight, presents a useful introduction to digital signal processing. Polynomial curve filtering is covered in chapter seven and the discrete Fourier transform and the fast Fourier transform in chapter eight. Although some readers may find the author's conversational style occasionally irritating, this is, in general, a highly readable treatment of what can be a very forboding subject. The author claims that it has worked well as a textbook at Stanford where, in addition to undergraduate electrical engineers, it has been well received by graduate students in computer science, the physical sciences and economics. It is unfortunate that the UK price of £39-55 in hardback seems certain to discourage its more widespread use. R. DETTMER
Linear motion electromagnetic systems There is no shortage of excellent books I. Boldea and S.A. Nasar on digital filters, a fact acknowledged in John Wiley the preface to this book, where the 1985, 482pp. £43-50 author admits that he came close to
choosing: 'Yet another digital filtering book' as the title. Developed from an undergraduate electrical engineering course at Stanford University, this is an introductory treatment written in a deliberately informal style. No prior knowledge of filtering is assumed, and the author studiously avoids the conventional approach to developing digital filter theory from analogue filters. The book is organised in four major sections. The first section, chapter one, provides an introduction to filtering in general and establishes the importance of the impulse response as a means of representing a digital filter's input-output relationship. Chapters two to four develop design techniques for nonrecursive filters. The frequency response is developed in chapter two, and Fourier design techniques for nonrecursive filters are introduced in chapter three. It is unfortunate that, despite the generally high standard of proof-reading, chapter three is headed: 'Design of recursive
Linear electric motors have fascinated academic teachers and students for a generation. The possibility of levitation and propulsion of electric vehicles brilliantly championed by Laithwaite for many years has been examined in universities and research institutions throughout the industrial world, so that there is now a vast literature ranging from electromagnetic theory through numerical calculation to practical matters of construction and manufacture. In this book the authors, who are well known for their contributions, have collected a large amount of useful information on many kinds of linear devices including pumps as well as all sorts of motors. The authors' chief concern is with the analysis of the electromagnetic action in these devices and they use this analysis in the development of design criteria. The treatment is at an advanced level and there is a good deal of the jargon of the subject including a vast array of slightly irritating abbreviations.
The work is arranged in terms of the types of machines. This has the disadvantage of losing the unity of the electromagnetic processes, but it makes the book useful as a work of reference for readers, already familiar with the general principles, who seek for information in particular applications. Such readers will be glad to have the book on their shelves. P. HAMMOND
VLSI signal processing: a bit-serial approach P. Denyer and D. Renshaw Addison- Wesley 1985, 312pp. £19-95 In Industry Year, it is gratifying to read a book produced from the research in a British university. That is particularly true in this case as the area of integrated circuit design and its applications has been dominated for so long by the United States. As a description of the work undertaken at Edinburgh, this book is excellent. The first part of it (chapters one to seven) describes the background conventions, and justifies the use of a bitserial approach. There is also an introduction to First the silicon compiler which is used in most of the applications in part two. Associated with the compiler is a hardware description language (HDL) that enables tne writing of a program representing the desired bit-serial processing algorithm. This description can then be used as input to a simulator. The book describes the syntax and semantics of the HDL and gives examples of its use. The remainder of the book describes the implementation of specific signal processors, e.g. FET, nonrecursive. recursive and adaptive digital filters, general-purpose bit-serial digital signal processors and a sound synthesiser, AII these chapters and chapter seven of part one are written by other authors, including Carver Mead and Richard Lyon. The main strengths of this book lie in the development of the HDL together with the discussion on applications. The information will be of use to anyone contemplating the hardware design of a digital signal processor as a specialpurpose VLSI chip or using off-the-shelf MSI and LSI. The book is not an introductory text and electronics engineers wishing to make use of the ideas embodied in the text should already have a working knowledge of digital signal processing and VLSI design. The main weaknesses concern the exclusive use of NMOS and the fact that the floorplan used by the First silicon compiler does not lead to efficient use of available silicon area. I also did not feel the index was comprehensive for a book of this size. In summary, the authors have produced an interesting and informative book covering important issues of hardware implementation of signal processors which will be of use to designers as well as researchers in VLSI applications. S. LAWSON
