Mutual Coupling Effect on Classical Three-way Doherty Amplifier for 5G Applications

Abstract

A three-way Doherty power amplifier targeting sub 6-GHz. Three 6W GaN transistors are used to design an 18W peak power with an 8.5 dB back-off efficiency. The amplifier achieved an efficiency of 55%, 63% and 80% at 8.5, 6, and 0 dB respectively from the peak power. The designed amplifier target 3.4-3.8 GHz band with a gain of 13 dB over the band. In addition, the amplifier was examined for different VSWRs taking into account the effect of impedance changing of antenna due to beamforming. There was an average of 3.35 dBm variation in the output power and 20% efficiency variation for different VSWRs at both the back-off and peaking regions. The structure of three-way Doherty amplifier or sequence of turning the peaking amplifiers on affects the amplifier performance for different VSWRs.