A Sub-6 GHz Ultra-Compact 69.8 % Drain Efficiency Harmonic Control Doherty Power Amplifier in GaN Technology

This paper presents a very compact sub-6 GHz GaN Doherty power amplifier (DPA) with harmonic control for 5G communications. Using harmonic tuning up to the 3rd harmonic, the main and auxiliary amplifiers feature both input and output termination for high efficiency at peak and output power back-off (OPBO). Harmonic impedance and intrinsic plane waveforms are analyzed for design optimization. At 5.8 GHz, the measured peak Pout and P1dB are 37.9 dBm and 32.8 dBm, with a drain efficiency reaching 69.8% at peak Pout and 47.4% at 6-dB OPBO. Digital predistortion (DPD) boosts average Pout from 28.9 to 31.9 dBm while achieving < 3.5% EVM for 256-QAM signals. The DPA occupies a chip area of only 3.2 mm² using 0.25-μm GaN HEMT technology.