Outphasing Class-E/ F2 Power Amplifier using a Quadrature Hybrid as Non-Isolating Combiner

Abstract

This paper presents a GaN HEMT outphasing power amplifier (PA), based on a class-E/ F2 topology with reduced sensitivity to variable resistive load operation, designed to provide output power control over an extended range with high efficiency. A 90-degree hybrid coupler is used as non-isolating combiner, incorporating an appropriate reactive termination on its fourth port. Besides its many intrinsic advantages, the mutual load modulation trajectories may be rotated by simply adjusting a capacitor value or alternatively the length of an open-circuited transmission line. Once implemented at UHF band, the outphasing PA provides a drain efficiency higher than 70% up to an output power 10 dB below its peak value (42.2 dBm).