Class-AB/F Doherty Power Amplifiers

The class-AB/F Doherty power amplifier (PA) adopts the concept of the class-AB/F PA to enhance efficiency while satisfying linearity. The third harmonic control circuits of the PA improve the efficiency without deteriorating the linearity, and the Doherty PA improves the linearity further by IM3 cancelation. The class-AB/F chips are fabricated by an InGaP/GaAs HBT process and combined on a PCB with a-quarter-wavelength transformer. The operation of the class-AB/F Doherty PA is demonstrated with a 54 Mbps/64 QAM OFDM signal having a 10.3 dB PAPR. The Doherty PA has EVM of 3% and the PAE of 31.5% at 24 dBm of average output power, 10.5 dB backed-off from P1dB of 34.5 dBm. The PA operates efficiently and linearly, suitable to the next generation of handset applications.