Phase-Locked Loops--principles and practice

International Journal of Electrical Engineering Education, Jul 1998 by Shaw, Brian M

Phase-Locked Loops - principles and practice: P. V. BRENNAN (Macmillan, 1996, 204 pp., 22 hardback)

The slim volume is a concise guide to the theory and design of phase-locked loops. It is written from an engineering viewpoint, and it is liberally illustrated with block and circuit diagrams, waveform and phasor diagrams, some photographs, tables of results and graphical responses. The book is aimed at design engineers and the more advanced students of electronics and telecommunications. Laplace transforms are used throughout to analyse system performance as required.

There are nine chapters in all, as follows:

Chapter 1 (Introduction) describes the basic phase-locked loop (PLL) with its 'curious' blend of both analogue and digital techniques. A few basic applications are mentioned to whet the reader's appetite and to generate initial interest.

Chapter 2 ( Loop Components) then describes the four basic loopcomponents (viz. the phase detector, the loop filter, the voltage-controlled oscillator, and the frequency divider) in detail, along with their behaviour and characteristics.

Chapter 3 (Loop Basics) explains how a PLL may be designed using standard control-systems techniques. Some basic loop filters and their responses are considered, and then analysed mathematically. Some consideration is also given to the measurement of the performance of the four basic loop-components.

Chapter 4 (Modulation) considers the phase or frequency modulation of a carrier wave and the necessary demodulation required. Practical examples of an FM transmitter and an FM demodulator using PLL techniques are illustrated and considered at circuit-component level.

Chapter 5 (Noise Performance) considers the PLL as a tracking filter which will allow not only the required input signal to pass, but also phase noise components either side of the carrier. The way in which this input noise affects the output of the PLL forms the focus of this chapter, along with some practical results.

Chapter 6 (Acquisition) explains how the PLL attains its locked condition. This involves some non-linear mathematical analysis as opposed to the simpler linear-analysis of the previous chapters.

Chapter 7 (Higher-Order Loop-Filters) describes how additional loop filtering will improve the PLL performance by providing superior rejection to high-frequency signals from the phase detector. This involves third-order loop-characteristics as opposed to the second-order loopcharacteristics encountered thus far.

Chapter 8 (Digital Loop Techniques and Design Methods) considers the design of fractional-N frequency synthesisers. In earlier PLL designs, only the frequency divider was implemented using digital techniques, but it is now possible to implement the whole PLL digitally, although, as the author concedes, some parts of the PLL are more suited to digital design techniques than others.

Chapter 9 (Phase-Lock Applications) presents some of the more advanced applications of PLLs which were first presented in the introductory chapter. Because the author developed this book from a series of lectures given to university students since 1990, he has also included fourteen examples and worked solutions after the final chapter. I like this feature and consider it to be particularly appropriate for all readers. This section is followed up by a short list of references, seven useful appendices (covering loop stability, noise, modulation and intermodulation, image rejection in mixers, and Laplace transforms), and a useful glossary of terms.

This theoretical and practical book provides a worthy, compact, selfcontained addition to the literature available on phase-locked loops, and is to be recommended to all who wish to understand, design, and utilise these systems.

BRIAN M. SHAW Department of Electrical and Electronic Engineering, University of Hertfordshire