Time domain poly-harmonic distortion models of RF transistors and its extraction using a hybrid passive/active measurement setup

Abstract

This paper presents a novel behavioral model of RF transistors under periodic stimulus that is mathematically equivalent to frequency domain Poly-Harmonic Distortion (PHD) models but is defined instead in the time domain. Given a fixed fundamental frequency for a periodic stimulus, a time domain PHD (TD-PHD) model that describes this periodic behavior consists of two nonlinear functions, each describing the large-signal response at one of the two ports of the RF transistor. In this model, the response at each port at any given time is a nonlinear time-invariant function of the stimulus at both ports throughout its entire RF period. Using a two-port hybrid passive/active multi-harmonic load-pull measurement setup, a 10W GaN packaged transistor biased in class AB is measured with a Nonlinear Vector Network Analyzer (NVNA). The predictive performance of the extracted model is validated against a power amplifier design that uses this RF transistor.