Efficiency and linearity enhancement of a two‐stage X‐band PA through simultaneous gate and drain supply modulation

Abstract

This study addresses an analogue method for mitigating the non-linearities introduced by discrete supply modulation of a high-efficiency power amplifier (PA). A 10 W two-stage X-band gallium–nitride monolithic microwave integrated circuit ( PA with a peak power-added efficiency of 55%, is tested with drain supply modulation from 10 to 20 V with an increase in efficiency and substantial degradation in linearity. In this work, the authors characterise the two-stage PA dynamically to develop shaping functions for both gate bias voltages. They 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 consistent improvement in noise power ratio over a static supply, for a 20 MHz noise-like signal. Results with a 20 MHz long-term evolution signal show comparable improvement in efficiency while maintaining adjacent channel power ratio near the level of the PA with a static supply.