Digital Transmitter and Envelope Tracking Power Amplifier using GaN Switching Mode Power Amplifiers

This work introduces a digital outphasing transmitter architecture, which is based on a hybrid architecture taking the advantage of Bandpass delta-sigma modulation, RF-Pulse width modulation, and outphasing. Digital outphasing PA based on GaN switching amplifier improves the average power efficiency of non-contiguous multi-band transmitters.
This paper also apply GaN switching amplifier to the supply modulator of the envelope tracking power amplifiers (ET-PA), and we have developed a high efficiency and multiband ET-PA using GaN for both RF-PA and the supply modulator. By testing this ET-PA using a Real-Time DPD (RT-DPD) system, we demonstrated that ACLR was improved to below -45dBc, even under a 80MHz LTE signal with 6.5 dB PAPR, while maintaining its high efficiency for multi-band operation. This, to the best of the authors' knowledge, is the widest modulation bandwidth yet reported for an efficient and multi-band ET-PA.