Study of peak and backoff efficiency of different power amplifier classes in outphasing systems

In this paper, we present an outphasing power amplifier system. The system performance is studied and analysed. The peak power efficiency and backoff power efficiency are compared for three classes of operation, class-D, class-E and class-F. Class-D power amplifier shows superior efficiency at both maximum power (95 %) and at backoff power. At 10 dB backoff power from peak power, efficiency is simulated to be 60 %. A proposed phase modulation improves efficiency at backoff power by 7-8 %. A CMOS class-D version is proposed to test the system implementation feasibility in CMOS technology and its performance is reported. The maximum efficiency is found to be around 70 % and the 5 dB backoff power efficiency is about 35 %.