An Envelope Tracking Supply Modulator Utilizing a GaN-Based Integrated Four-Phase Switching Converter and Average Power Tracking-Based Switch Sizing With 85.7% Efficiency for 5G NR Power Amplifier

This article proposes a supply modulator (SM) that uses high switching frequency gallium-nitride (GaN) devices to achieve a four-phase fast step-down converter for the fast-tracking ability of the envelope tracking (ET). The ET signal is reshaped to generate an average power tracking (APT)-based signal to control the size of GaN switches to further increase light-load efficiency due to reduced switching loss. Moreover, a high-bandwidth and low-loss linear amplifier (LA) is used to supply the power amplifier (PA) to sufficiently provide fast-tracking speed for 5th generation (5G) NR ET. At a power of 3.5 W for 5G mobile phones, the peak efficiency that is tested with NR -130 MHz in the ET mode is as high as 85.7% over a wide load range.