Measurements of time domain voltage/current waveforms at R.F. and microwave frequencies for the characterization of nonlinear devices

A novel time domain large signal characterization of microwave transistors is described. An harmonic load-pull system, based on the use of three separated active loops, allows synthesizing the load impedances of the device under test at the first three harmonic frequencies. The visualization and the accurate measurement of high frequency current/voltage at low, medium and large RF power levels, is performed by coupling these harmonic load-pull facilities with a "nonlinear network measurement system". GaAs FETs and GaInP/GaAs HBTs have been characterized and optimized under single tone and multitone large signal exitations. A comparison between measured and simulated current/voltage waveforms is also presented. Such results prove the great capabilities offered by this new time domain characterization approach to aid in designing optimized power amplifiers and in validating nonlinear model for CAD.