Enhanced prediction of pHEMT nonlinear distortion using a novel charge conservative model

Abstract

We prove a large-signal charge conservative nonlinear pHEMT model that smoothly fits measured gate capacitance curves and produces accurate nonlinear simulation results for IMD and ACPR. Capacitances are derived from a single gate charge function, which negates the need for problematic transcapacitance elements. The charge model is fully continuous and provides very good fits over the entire DC bias range. Experimental verification of the model is undertaken by performing one-tone and two-tone power sweeps of the device and by measuring the spectral regrowth of a pHEMT class AB power amplifier excited by a W-CDMA input signal.