Envelope Signal Triggered Constant-On-Time Control of Wideband High-Efficiency Envelope Modulator

The article presents a wideband high-voltage envelope modulator design for 5G NR base-station envelope tracking power amplifiers (ETPAs). The proposed modulator architecture combines a high-efficiency switching amplifier with a parallel wideband linear amplifier, and a novel envelope-triggered constant-on-time controller is proposed to coordinate the operation of these components. The design enables the modulator to efficiently deliver the average power required by the PA while providing a wide range of dynamic voltages. Furthermore, the constant on-time controller triggered by the output envelope signal dynamically adjusts the switching frequency of the switching power amplifier, ensuring the output current adeptly to high-speed load changes. Measurement results demonstrate that the modulator achieves an efficiency of around 82.5% at 25 W power delivery using a 100 MHz modulation signal with a peak-to-average power ratio (PAPR) of 6.5 dB. The overall output normalized RMS error is within 2.3 % and the load transition time is less than 8.5 μsec. Experimental validation underscores that the modulator is highly appropriate for integration within ETPAs employed in 5G NR systems, encompassing time-division duplexing (TDD) techniques that necessitate rapid power changes in RF amplifiers.