A Fast Transitioning Power Supply Modulator of Stepped Envelope Tracking for 5G/6G Millimeter-wave Applications in 65nm CMOS

This article presents a fast-transitioning power supply modulator (PSM) which is proposed to be used in envelope tracking(ET) systems for high bandwidth millimeter-wave RF power amplifiers (PA) operating on high peak to average power ratio (PAPR) signals. The proposed modulator uses a hybrid architecture which is designed to have a fast response time to stepped input signals. The main contributions of this work are in proposing stepped envelope tracking scheme for PAs in 6G applications, the design of PSMs for stepped signals, understanding the design considerations for the linear amplifier, and providing a design which has a balance between switching speed and steady-state ripple. While driving a 6Ω load, the modulator achieves an overall efficiency of 78.2% while providing an output power of more than 650 mW at an output voltage of 2V and a steady-state ripple of around 35mV. While transitioning between multiple power supply levels, the design achieves fast transition times, as low as 19.6 ns for a 0.3V transition, when driving the output load. The design is implemented in a commercial 65nm CMOS process with 2.5V IO devices, occupying an area of 265 µm × 125 µm. The proposed circuit is a candidate for stepped envelope tracking power amplifier systems for high bandwidth signals.