Overview
At one time, linear systems and components
were designed using a patchwork of instru-
mentation and measurements. This approach
was quickly replaced by scattering parameters
(S-parameters), which uni? ed the multiple
instruments and measurements and enabled
just one instrument, the network analyzer, to
make measurements like gain, isolation and
match with a single connection. For more than
40 years, S-parameters have stood as one
of the most important of all the foundations
of microwave theory and techniques. They
are related to familiar measurements such as
S11
?input match, S22
?output match, S21
?gain/loss, and S12
?isolation, and can be easily
imported into electronic simulation tools. Today,
S-parameters are commonly used to analyze
and model the linear behavior of RF and
microwave components. Unfortunately, current
industry trends toward increasing energy
ef? ciency, higher output power and longer
battery life are forcing many linear devices to
operate in a nonlinear fashion. Measuring this
behavior requires a solution that is much more
deterministic in nature.