Measurements of time-domain voltage/current waveforms at RF and microwave frequencies based on the use of a vector network analyzer for the characterization of nonlinear devices-application to high-efficiency power amplifiers and frequency-multipliers optimization

A new time-domain waveform measurement system based on the combination of an harmonic source and load-pull setup with a modified vector network analyzer (VNA) is presented. It allows the visualization, the measurement, and the optimization of high-frequency currents and voltages at both ports of nonlinear microwave devices. Measurements of GaAs field effect transistor (FET's) and GaInP/GaAs heterojunction bipolar transistor (HBT's) at L-band were performed to demonstrate the great capabilities of the system. On one hand, voltage and current waveforms at both ports of transistors, working as power amplifiers, were optimized for maximum power-added efficiency. On the other hand, time-domain waveforms of transistors operating as frequency multipliers were optimized for maximum conversion gain. Such results prove the capabilities offered by this new nonlinear time-domain measurement system to aid in designing optimized power amplifiers or frequency multipliers. They also provide valuable information for nonlinear transistor model validation.