A 24-to-30-GHz GaN MMIC Doherty Power Amplifier Using Reduced Peaking Intrinsic Output Impedance for Bandwidth Extension

This letter presents a millimeter-wave gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) Doherty power amplifier (DPA) for 5G-NR applications. The bandwidth of the DPA is extended by reducing the intrinsic output impedance of the power-stage peaking transistor at the back-off by selecting a proper gate bias voltage. To verify the concept, a 24–30-GHz GaN MMIC DPA was designed using a 120-nm GaN-on-SiC HEMT process. The fabricated DPA can achieve a saturated power range of 31.6–32.7 dBm, with a corresponding power-added efficiency (PAE) of 20%–27.6%. The PAE at 6-dB PBO ranges from 18.2% to 22.4% in the 24–30-GHz frequency band. When excited by a 100-MHz 5G-NR signal, the DPA can achieve 1.1% EVM and -45.8 dBc ACLR after using digital predistortion.