Tunable outphasing for power amplifier efficiency improvement under load mismatch

Load mismatch in RF high power amplifier leads to efficiency reduction or amplifier failure. Instead of impedance tuning, in this paper an outphasing architecture with a tunable non-isolated combiner is used to reduce sensitivity to load variations. Experimental results with two GaN class AB amplifiers at 2.14GHz show it is possible to maintain the efficiency above 50% over a wide range of impedances, while maintaining the output power within a few dB around 20W.