Gate Pulsing as a Transient Ringing Reduction Method for Multi-Level Supply Modulators

Journal article, 2023

This letter demonstrates a gate pulsing technique to reduce the ringing in multi-level dynamic voltage supplies used for modulating the drain bias of GaN radio-frequency power amplifiers (RFPAs). Supply modulation can improve overall average efficiency when the RFPA is amplifying signals with varying envelopes. Multi-level discrete supply modulators (SMs) are used for high instantaneous bandwidth signals when continuous modulators become inefficient. These SMs provide several voltage levels to the RFPA using transistor switches. By pulsing the gate drive of switches on and off quickly before ultimately turning them on, the switches undergo an intermediate lossy state which reduces the ringing. The pulse settings can be individually adjusted for different voltage level transitions and loads. Gate pulsing is compared to conventional ringing reduction techniques such as varying the fixed series gate resistance, and dead-time optimization. Gate pulsing experimental results with a 4-level SM and 8 MHz 64-QAM signal show a significant improvement in ringing over dead-time optimization with only a 0.9% points drop in efficiency.