Impedance Sensing Integrated Directly into a Power Amplifier Output Matching Network

Abstract

This work presents a radio-frequency power amplifier (RF PA) with load impedance sensing integrated directly into the output matching network (OMN), for in-situ monitoring in applications such as electronically steered phased arrays. Using reflectometry techniques that have been previously applied to sampled transmission lines and other six-port reflectometers, power sampling is instead applied directly to the existing OMN of a class-AB harmonically-tuned PA. This enables load impedance variations to be directly measured without requiring additional elements in the RF path. The prototype sampled-OMN PA demonstrates nearly identical RF performance when characterized with and without impedance sensing. Initial results based on load pull measurements demonstrate the feasibility of this sensing approach.