Simultaneous match antenna tuning for GaN RF power amplifiers

GaN RF power amplifiers can be especially sensitive to variations in load impedance and supply variation.  High voltage operating conditions lead to increased sensitivity to capacitive loading effects, and mismatch effects from the output load impedance can lead to large dynamic voltage and temperature swings inside the device, which in the worst case can lead to transistor reliability problems, and as a minimum, degrade output power, efficiency and linearity.

High voltage GaN switch based tuneable matching networks are a potential solution to this problem[1].  These networks can operate like tuneable filters to mitigate the mismatch between antenna and the system matching impedance.  These devices are typical in mobile applications, where the antenna is subject to large amounts of capacitive coupling (hand effect), resulting in a large VSWR presented to the analog circuit.  These circuits are not commonly used in higher power applications due to the linearity degradation from the switches.  GaN switches have the potential to mitigate some of these issues, due to their inherently high voltage operating range[2].  Furthermore the antenna tuner could be used to replace other backoff efficiency enhancement methods such as Doherty or high bandwidth envelope tracking, which can both introduce excess nonlinearity.

This project aims to design, tape out and measure, a tuneable output matching network for a GaN power amplifier, and simulate the effect on linearity under both external supply and load modulation.