Characterizing Components Under Large Signal Excitation: Defining Sensible "Large Signal S-Parameters"?!

A measurement and black-box modeling technique is described enabling the characterization of nonlinear microwave components under periodic large-signal excitation. First, the mathematical model is theoretically described. The model is based on the assumption that the superposition principle holds for the effect of all spectral components, except the fundamental, of the incident travelling voltage waves. This assumption implies that, with fixed fundamental power and biasing conditions, the incident harmonics interact with the component as if it is a linear time-varying circuit. Since the superposition coefficients are a natural extension of the classical scattering parameters they are called "large signal s-parameters". These coefficients are a function of fundamental power and biasing conditions. An automated set-up is described enabling to accurately measure these coefficients. The set-up is based on a "vectorial nonlinear network-analyzer", which accurately measures the phase and amplitude of all spectral components of both incident and reflected travelling voltage waves. The experimental model extraction method is illustrated on a heterojunction bipolar and a field effect transistor, driven hardly nonlinear. The "vectorial nonlinear network-analyzer" is used in order to successfully verify the validity of the extracted model. The black-box model is finally integrated in a commercial harmonic balance simulator.