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Introduction 5
accommodated by explanation of programs for the 1+Q' method and
paralleled-reactances technique. Transmission-line matching applications for
complex source and load are described by less well-known methods. Levy's
broadband-matching adaptation of Fano's original theory is reviewed, and
programs are provided. Standard lowpass prototype filter notation, lowpassto-bandpass
transformation, and Norton transformers are used in practical
examples. The last two topics in Chapter Six are new methods of broadband
matching. Carlin's method for matching measured impedances is developed
on the basis of several computing aids that include a Hilbert transform
application with quite general significance. Cottee's pseudobandpass (lowpass
transformer) matching method employs numerical integration of the
Chebyshev squared-frequency function. This is accomplished with the Romberg
integration program from Chapter Two.
Chapter Seven contributes uniquely to reader background. Amplifier designers
experienced in scattering parameters, the equipment for their measurement,
and the body of technique for their use are probably aware of the large
and growing number of computer programs available for the methods involved.
The better-known programs exist on timeshare computing services and
provide stability, gain, impedance, selectivity, optimization, and device data
base information for amplifiers and their matching networks. There are also
numerous smaller programs of reduced scope available for desktop and
hand-held computers. Furthermore, the trade journals and institutional literature
are full of design articles about scattering parameter applications. Chapter
Seven provides the perspective and computing tools that are not readily
available and yet are the basis for the popular methods. Generalized reflection
coefficients for power waves are defined and related to scattering parameters
for two- and three-port linear networks. A convenient means for ladder
network analysis with embedded circulators is noted. The bilinear function of
complex variable theory is introduced and arranged to represent a Smith chart
of all possible branch impedance values on a linear network response plane.
Convenient methods and computer programs are given for determining the
coefficients, the relationship of the Smith chart to two-port power, and
geometric models of important network behavior. Concise unification is
provided for earlier Linvill models, gain analysis, and impedance-mapping
methods for linear networks. This insight also applies to oscillator, filter, and
impedance-matching design. A new gain design method based on the older
Linvill model is described.
Chapter Eight introduces a new method for direct-coupled filter design
based on a loaded-Q parameter that is well known to early radio-manufacturing
engineers. The great strength of the method is the wide range of
element values that can be selected by the designer with guidance by its clear
principles. Direct-coupled-filter principles are widely utilized in design of
microwave filters based on the inverter principle. They have important applications
at all frequencies down to vlf. This topic is developed by a practical
relationship of resonators (tanks), inverters, and end-coupling methods, and