GaN-Based Digital Class-E Doherty Power Amplifier for 5G FR1 Frequency Band

This paper presents for the first time a GaN-based digital class-E Doherty power amplifier module (PA) for the 5G FR1 frequency band. Two identical class-E PA MMICs with digital pulse-width modulated (PWM) input driving are combined in a two-way Doherty configuration for high efficiency over an extended output back-off (OBO) range up to 9dB. A wideband Doherty combiner design strategy is adapted to the class-E capabilities of the PAs to achieve high-efficiency for low power levels leading to an extended back-off range. At 7.5dB OBO, the measured final-stage drain efficiency (ηdrain) peaks at 68% for 3.4 GHz PWM single-tone input signal. Over a 3.2-3.6GHz frequency range the prototype achieves a minimum of 52% ηdrain at 9dB OBO. The maximum saturated output power is 32.8dBm. At 3.3GHz, the PA module achieves 60% and 59% ηdrain for a 20MHz and 100MHz 9dB PAPR digital OFDM input signal, respectively.