A Depletion-Mode GaN-Based Envelope Tracking Supply Modulator Utilizing a Novel Coupled PWM Generator

This brief presents a depletion-mode GaN-based envelope tracking supply modulator (ETSM) that employs a novel Coupled Pulse Width Modulation (PWM) Generator. The Coupled PWM Generator consists of an integrated common-source amplifier and several passive components. With the proposed PWM generator, the d-mode GaN-based ETSM can be directly controlled by an input envelope signal instead of a pair of PWM signals, thereby eliminating the demand for an extra PWM process. The measured peak output power of the ETSM is 5.4 W, with a total efficiency of 89% at 100 MHz switching frequency. When tracking a Long Term Evolution (LTE) signal with a 20 MHz bandwidth and a 6.5 dB peak-to-average power ratio (PAPR), the ETSM achieves a total efficiency of 81%, with an average output power of 2.32 W and a Normalized Root Mean Square Error (NRMSE) of 3.9%.