UHF Class-E power amplifier design for wide range variable resistance operation

Abstract

This paper presents a simple switch model for a GaN HEMT device, extracted to estimate the output power and efficiency load-pull contours when the transistor is used in a UHF class-E power amplifier (PA). The impact of model parameters on the theoretical achievable efficiency versus output power backoff (PBO) profile is considered, to then be used in a load-insensitive class-E design methodology. A simple lumped element terminating network, derived from [1], was selected to approximate the desired zero voltage switching (ZVS) operation along a wide range of resistive loads. A 700 MHz outphasing transmitter, amenable to be transformed into a resonant dc/dc power converter, has been implemented for validation. Drain efficiency peaks of 82.2% and 78% have been measured for each application case, with values above 70% and 60% at 10 dB of backoff and 30% of nominal dc output power, respectively.