The motivation for starting the work described in this book was the
interest that Hewlett-Packard's microwave circuit designers had in
simulation techniques that could tackle the problem of finding steady-
state solutions for nonlinear circuits, particularly circuits containing
distributed elements such as transmission lines. Examining the problem
of computing steady-state solutions in this context has led to a
collection of novel numerical algorithms which we have gathered, along
with some background material, into this book. Although we wished to
appeal to as broad an audience as possible, to treat the subject in
depth required maintaining a narrow focus. Our compromise was to assume
that the reader is familiar with basic numerical methods, such as might
be found in [dahlquist74] or [vlach83], but not assume any
specialized knowledge of methods for steady-state problems. Although we
focus on algorithms for computing steady-state solutions of analog and
microwave circuits, the methods herein are general in nature and may
find use in other disciplines. A number of new algorithms are presented,
the contributions primarily centering around new approaches to harmonic
balance and mixed frequency-time methods. These methods are described,
along with appropriate background material, in what we hope is a
reasonably satisfying blend of theory, practice, and results. The theory
is given so that the algorithms can be fully understood and their
correctness established.