Systematic evaluation of PHEMT large signal characteristics using time domain measurements

Abstract

The complete Pseudomorphic High Electron Mobility Transistor (PHEMT) gate and drain RF I-V contours are systematically and accurately characterised for use in table based or table-equation based nonlinear CAD (Computer Aided Design) models. Waveform measurements are achieved using a fully vector error corrected, time domain nonlinear vector network analyser system, based on the HP-MTA (Microwave Transition Analyser). The technique is established around a simple mathematically proven harmonic compression concept. A fixed harmonic condition is set-up and maintained throughout the drain scan duration, such that the observed dynamic loadline saturates to the given condition symmetrically about the DC quiescent point. Measurement analysis yields numerical and also first order observational information about the Imax/sub RF/ and Imin/sub RF/ boundaries yielding directly effects such as soft breakdown, knee voltage, thermal roll off, and RF to DC related issues. Ensuing work indicates the extraction of totally dynamic RF I-V and RF Q-V contours, directly from large signal measurements.