Fast-Switchable 3.6 GHz GaN Doherty Power Amplifier for Energy-Efficient Non-Continuous Transmission of 256-QAM Signals

Doherty power amplifiers (DPAs) allow efficient amplification of continuous signals with high peak-to-average power ratio (PAPR). However, when transmission is not continuous, it is beneficial to turn-off the PA to uphold the high dc-to-RF efficiency. This paper presents a 41 dBm DPA with a power-added-efficiency (PAE) around 50 % over 6 dB back-off and fast operating point switching (OPS) between sleep and active state. To study the impact of OPS on signal quality, the error vector magnitude (EVM) is studied for a 256 quadrature amplitude modulation (QAM) signal under OPS conditions. At a peak envelope power of 40 dBm, the average EVM remains below 3.5 % even when turning off the PA between transmission bursts. When in sleep state, energy consumption is reduced from 1.5 W to 1 mW, enabling highly-efficient operation regardless of network load.