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.
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