Performance of adaptive predistortion temperature in RF power amplifier linearization

Abstract

The input-output AM/AM and AM/PM characteristics of an RF power amplifier varies with junction temperature. A thermal model of a power amplifier (PA) is built by using thermal impedance curves of a power transistor. Based on this model, the dynamic performance of a PA is simulated under different input signal conditions, with and without predistortion. It is shown that variations in junction temperature due to input signal modulation have an insignificant effect on the performance of predistortion linearization, but variations due to longer term average power dissipation degrade the performance and must be tracked.