Dual Gate and Drain Supply Modulation of an X-Band PA

This paper addresses an analog method for mitigating the nonlinearities introduced by discrete supply modulation of a high-efficiency power amplifier. A 10-W two-stage X-band GaN MMIC PA, with a peak power-added efficiency (PAE) of 55%, is tested with drain supply modulation from 10 to 20 V. Drain supply modulation increases the efficiency, but substantially degrades the amplifier linearity. In this work, we demonstrate that gate modulation can improve back-off gain and linearity, specifically when gate biases of the two stages of a PA are independently modulated. Simultaneous gate and drain modulation results in 15 percentage point improvement in efficiency over a static supply, and a 10 dB improvement in noise power ratio (NPR) over drain supply modulation only, for a 10 MHz noise-like signal.