A 16.5 to 23.1 GHz High Efficiency Broadband GaN Doherty Power Amplifier utilizing Relative Input Phase Compensation Circuit

This paper reports the design and measurement of a high efficiency broadband Gallium Nitride (GaN) Doherty power amplifier (DPA) monolithic microwave integrated circuit (MMIC) fabricated on a 0.15 μm gate-length GaN-on-SiC process. To achieve high efficiency broadband operation, a relative input phase compensation circuit is proposed to correct the frequency-dependent relative phase difference between the Tee-network output combiner and the input phase circuit. Load modulation is realized at the transistor intrinsic node through the Tee-network output combiner, which incorporates the transistor’s equivalent output capacitance. The fabricated GaN DPA MMIC delivers a saturated output power of 33.7 to 35.7 dBm with peak power added efficiency (PAE) of 31.8 to 42.2%, and PAE at 6 dB back-off of 25.0 to 35.1% over frequency of 16.5 to 23.1 GHz. To the best of the authors' knowledge, the achieved 33% fractional bandwidth is the widest reported for a GaN DPA in the K-band.