Self-heating and memory effects in RF power amplifiers explained through electro-thermal

Self-heating has already been proven to be one of the key sources to memory effects in RF power amplifiers (PAs). However, mechanisms behind the generation of memory effects, as caused by self-heating have not been well documented. On basis of transistor physical properties this paper proposes a simple electro-thermal model and shows how self-heating can generate different types of memory effects, such as bandwidth dependent intermodulation components and hysteresis loops. In addition, it is shown that self-heating can result in generation of new spectral components even in an otherwise linear PA. A time domain modeling framework is implemented to investigate memory effects generated by self-heating and simulation results are shown to agree with theoretical analysis.

I. Introduction

Memory effects observed in typical RF PAs normally originate from 3 sources: self-heating [1], electron trapping [2] and baseband effects [1], [3]. Usually, these sources affect the performance of PAs simultaneously, which makes an understanding of the impact of each source difficult. Consequently, PAs with memory effects are normally analyzed and modeled behaviorally on the basis of measured data. For instance, Volterra series [4] represents a typical behavioral modeling approach. However, a behavioral modeling approach does not offer any physical explanation and understanding of the mechanism behind the memory effects.