Incremental behavioral modeling of envelope-dependent nonlinear distortion in dynamic supply power amplifiers

Abstract

This paper presents behavioral modeling of an envelope tracking (ET) power amplifier (PA) excited by an slewrate limited envelope. In order to relax the slew-rate requirements of current efficient envelope amplifiers (EA), we can drive the ET PA with a slower version of the signal’s envelope. However, the resulting amplified signal suffers from nonlinear distortion due to the time-variant gain effects that arise when using the slower version of the signal’s envelope. In this paper this time-variant effects are presented and characterized. A new envelope-dependent (ED) behavioral model is presented and compared with a simpler static AM-AM and AM-PM modeling. Experimental results showing the performance of the proposed ED model were obtained with an ET PA based on a GaN transistor.