28GHz Dual-Mode Power Amplifier for Enhanced Load Resiliency or Back-Off Efficiency Enhancement

This paper presents a dual-mode power amplifier (PA) with configurable gate biases for large-scale antenna array system front-ends. In VSWR resiliency mode, the PA maximizes resilience to high load variations caused by antenna cross-coupling, maintaining consistent power, linearity, and efficiency. In back-off (BO) efficiency mode, it improves BO efficiency for high-PAPR signals during minimal load variation. A 28 GHz prototype is implemented using the 22 nm FD-SOI CMOS process. Under a 50-ohm load, the VSWR resiliency mode achieves 16.5 dB gain, 13 dBm output power, and 18% peak PAE. The BO efficiency mode delivers 13 dB gain, 13 dBm output power, and 17.5% and 11% PAE at peak and 6 dB back-off, respectively. Against a varying load, VSWR resiliency mode shows 0.5 dB average power loss, while BO efficiency mode shows 1 dB loss. Modulated signal testing confirms the superior performance of VSWR resiliency mode under load variation.