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Preface
This book was started while the author was Professor and Head of Department at Etisalat
College which was set up with the technical expertise of the University of Bradford,
England. It was continued when the author returned to the Open University, England.
Many thanks are due to my colleagues Dr David Crecraft and Dr Mike Meade of the Open
University, Dr L. Auchterlonie of Newcastle University and Dr N. McEwan and Dr D.
Dernikas of Bradford University. I would also like to thank my students for their many
helpful comments.
High Frequency and Microwave Engineering has been written with a view to ease of
understanding and to provide knowledge for any engineer who is interested in high
frequency and microwave engineering. The book has been set at the third level standard of
an electrical engineering degree but it is eminently suitable for self-study. The book
comprises standard text which is emphasised with over 325 illustrations. A further 120
examples are given to emphasise clarity in understanding and application of important
topics.
A software computer-aided-design package, PUFF 2.1 produced by California Institute
of Technology (CalTech) U.S.A., is supplied free with the book. PUFF can be used to
provide scaled layouts and artwork for designs. PUFF can also be used to calculate the
scattering parameters of circuits. Up to four scattering parameters can be plotted simultaneously
and automatically on a Smith chart as well as in graphical form. In addition to the
PUFF software I have also included 42 software application examples. These examples
have been chosen to calculate and verify some of the examples given in the text, but many
are proven designs suitable for use in practical circuits. The confirmation of manual design
and CAD design is highly gratifying to the reader and it helps to promote greater confidence
in the use of other types of software. An article ‘Practical Circuit Design’ explaining
how PUFF can be used for producing layout and artwork for circuits is explained in
detail. There is also a detailed microwave amplifier design which uses PUFF to verify
circuit calculations, match line impedances, and produce the artwork for amplifier fabrication.
There is also a copy of CalTech’s manual on disk. This will prove useful for more
advanced work.
The book commences with an explanation of the many terms used in radio, wireless,
high frequency and microwave engineering. These are explained in Chapter 1. Chapter 2
provides a gentle introduction to the subject of transmission lines. It starts with a gradual
introduction of transmission lines by using an everyday example. Diagrams have been
used to illustrate some of the characteristics of transmission lines. Mathematics has been
kept to a minimum. The chapter ends with some applications of transmission lines especially
in their use as inductors, capacitors, transformers and couplers.
Chapter 3 provides an introduction to Smith charts and scattering parameters. Smith
charts are essential in understanding and reading manufacturers’ data because they also
provide a ‘picture’ of circuit behaviour. Use of the Smith chart is encouraged and many
examples are provided for the evaluation and manipulation of reflection coefficients,
impedance, admittance and matching circuits. For those who want it, Smith chart theory is
presented, but it is stressed that knowledge of the theory is not essential to its use.
The installation of PUFF software is introduced in Chapter 4. The chapter goes on to
deal with the printing and fabrication of artwork and the use and modification of templates.
Particular attention is paid to circuit configurations including couplers, transformers and
matching of circuits. Scattering parameters are re-introduced and used for solving scattering
problems. Many of the examples in this chapter are used to confirm the results of the
examples given in Chapters 2 and 3.
Amplifier circuitry components are dealt with in Chapter 5. Particular attention is paid
to the design of Butterworth and Tchebyscheff filters and their uses as low pass, bandpass,
high pass and bandstop filters. Impedance matching is discussed in detail and many methods
of matching are shown in examples.
Chapter 6 deals with the design of amplifiers including transistor biasing which is
vitally important for it ensures the constancy of transistor parameters with temperature.
Examples are given of amplifier circuits using unconditionally stable transistors and conditionally
stable amplifiers. The use of the indefinite matrix in transistor configurations is
shown by examples.
The design of microwave amplifiers is shown in Chapter 7. Design examples include
conjugately matched amplifiers, constant gain amplifiers, low noise amplifiers, broadband
amplifiers, feedback amplifiers and r.f. power amplifiers.
Oscillators and frequency synthesizers are discussed in Chapter 8. Conditions for oscillation
are discussed and the Barkhausen criteria for oscillation is detailed in the early part
of the chapter. Oscillator designs include the Wien bridge, phase shift, Hartley, Colpitts,
Clapp, crystal and the phase lock loop system. Frequency synthesizers are discussed with
reference to direct and indirect methods of frequency synthesis.
Chapter 9 is a discussion of topics which will prove useful in future studies. These
include signal flow diagrams and the use of software particularly the quasi-free types.
Comments are made regarding the usefulness of Hewlett Packard’s AppCAD and
Motorola’s impedance matching program, MIMP.
Finally, I wish you well in your progress towards the fascinating subject of high
frequency and microwave engineering.
Ed da Silva