A 6.4-7.2 GHz Gain-Enhanced GaN MMIC Doherty Power Amplifier Based on Adaptive Power Divider for 6G Applications

This paper presents a GaN MMIC Doherty power amplifier (DPA) for 6G applications. To enhance gain and power-added efficiency (PAE), an adaptive power divider is employed, avoiding the inherent 3-dB gain reduction from traditional Wilkinson dividers. The fabricated DPA, with a compact size of 1.5 mm × 1.5 mm, operates across 6.4-7.2 GHz. It achieves a saturated output power of 40.49-41.53 dBm, a saturated PAE of 40.24-51.5%, a gain of 10.8-12.6 dB at back-off, and a 6-dB back-off PAE of 37.5-45.6%. With a 100-MHz single-carrier 256QAM signal having a 7.4-dB PAPR the measured adjacent channel power ratio (ACPR) is -32.95/-36.85 dBc without digital predistortion (DPD) and -50.44/-50.29 dBc with DPD. For an extended bandwidth of 300 MHz, the ACPR is -30.49/-32.65 dBc without DPD and -45.48/-45.02 dBc with DPD. The corresponding error vector magnitudes (EVM) without DPD are -31.4 dB and -30.11 dB for the 100-MHz and 300-MHz bandwidths, respectively.