A Mixer-Like Nonlinear Analysis for GaN HEMT Supply-Modulated Power Amplifier at 3.8 GHz

A nonlinear analysis of a GaN HEMT supply-modulated power amplifier (SMPA) based on the time-varying power series approach is presented. For this purpose, the SMPA operation is described as a drain mixer, in which the envelope signal plays the role of the local oscillator. The proposed analysis predicts the internal cancellation of intermodulation products, determined by nonlinear contributions occurring in the SMPA and identifies the responsible terms. The approach is based on the extraction of the requested parameters from dynamic I/V characteristics. This analysis is validated experimentally by a GaN HEMT SMPA operating at 3.8 GHz developed for this purpose, reporting a decrease of third-order intermodulation products in excess of 30 dB.