A 24-to-28-GHz Asymmetric GaN MMIC Doherty Power Amplifier With 32% PAE at 8-dB Back-Off Using Optimal Phase Dispersion Inverter

In this letter, a high-performance millimeter-wave (mm-wave) asymmetric gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) Doherty power amplifier (DPA) for 5G-new-radio (NR) n258 band application is presented. To ensure that each transistor can achieve a proper active load impedance across a wide bandwidth during load modulation, a method for designing the impedance inverter with the optimal phase dispersion characteristic is proposed. For verification, a 24-to-28-GHz asymmetric GaN MMIC DPA was designed using a 150-nm GaN-HEMT process. The fabricated DPA achieved a saturated power range of 36.8–38.1 dBm, with a saturated power-added efficiency (PAE) of 29.7%–36.8%. The PAEs at 8- and 9-dB power back-offs (PBOs) ranged from 18.6% to 32% and 18.8% to 29.7%, respectively. After applying digital predistortion, the DPA achieved a high average PAE of 29% with good linearity when excited by a 400-MHz modulated signal.