High-linearity RF amplifier design [Book Review]

In most modern telecommunication and radar systems, the capability of operation in a very congested radio frequency environment is vital both for the best performance of the particular system itself, but also for the sake of other system’s survival. Thus, i t has become more important to configure system components, which, on one hand, are able to sustain considerable amounts of interfering signals, but, on the other hand, produce the smallest feasible amounts of spurious emissions. As if this were not complicated enough, we must further manage the required performance improvement jointly with top modulation characteristics, a reduction of battery drainage (in portable equipment) or heat production (high power units having excessive heat output in radar systems, etc.), and we must keep the overall costs of operation and manufacturing as small as possible. So, doesn’t this sound like a very typical systems engineering problem? The generation of highly pure signals for the radio frequency environment is surely a challenging task and will obviously benefit from top-level literature for the education of up and coming engineers and scientists and the upgrading those of us already in front of the CAD screen or at the laboratory table (where this reviewer once, in the 1970s, destroyed the only spectrum analyzer in-house while trying to get his marvelous power amplifier to work). Artech House has been lucky to find Dr. Peter Kenington, who received his Ph.D. in electronics in 1989 from the University of Bristol, to author such a sturdy book as High-Linearity RF Amplifier Design. A person having experience in transmitters, receivers, satellite subsystems, CCIR work and software radio seems to be one of the best candidates for this kind of task, and especially so, as Dr. Kenington is currently active in the management of various wireless system projects at Wireless Systems International, Ltd, UK. Already, the initial impression of this book inspires confidence in quality and devotion. More than half a thousand pages just on amplifier linearity should give the reader some overview on the topic, indeed. The contents are divided into eight main chapters, the first of which is an introduction and the second describes distortion processes in amplifiers following a solid, gradual approach. Chapter 3 is a basic but relatively in-depth discussion of power amplifier design at radio frequencies; while Chapters 4-6 introduce all of the main linearization techniques including: feedback; feedforward; and predistortion. In Chapter 7, we have complete linear transmitters with signal processing as a topic, and, finally, in the last chapter, enter the difficulties of efficiency boosting. No list of symbols or acronyms is available, but the number of index words is above 1400. References have been arranged after each main chapter and their total amount is near 250. In terms of reader-friendliness, as estimated by crude numbers, High-Linearity RF Amplifier Design is clearly above average with over 260 illustrations (all line drawings or measurement results as plots) and over 530 equations, of which not too many require advanced mathematical skills to follow apparently as 3D vector field operations are not necessary for this topical area! The general style of writing is very informative and seemingly tries to clarify all-important topics of various key details although, at times, the author may create an atmosphere of “infirmation attack” by pointing out vital elements very strongly and comprehensively. Both the mathematical treatment, associated explanations in the main text, and the selection of illustrations confirm the impression of an author having up-to-date and hands-on experience on which to build his presentation. Also, the compilation of the book looks very attractive. Despite the general outlines of amplifier design and distortion, problems should have been covered in typical courses of electronics or telecommunications engineering in universities or technical colleges; the reader will not suffer from a well-organized repetition here. As required by the topic, the book has to merge at least four layers of electrical and electronics engineering starting from the currentlvoltage characteristics of modem semiconductor devices; then going to the circuit topology of various amplifiers based on BJT or FET technology, through which we come to the complete transmitter arrangements where cooling and