International Journal of Electronics and Telecommunications

Abstract

In this paper, some of the existing classifications of the Saleh's and related models of the AM/AM and AM/PM conversions occurring in communication power amplifiers (PA) are reviewed. It is shown that these classifications are inconsistent and must be refined. Obviously, carrying out such a refinement properly needs a good knowledge and correct understanding of the mechanisms leading to the AM/AM and AM/PM conversions. This was achieved in this paper by performing a thorough analysis of the PA behavior using an analytical tool, the Volterra series. The main points of this analysis are presented here in great detail. Among others, it is shown that the influence of the PA memory on the AM/PM conversion is two-fold: direct and indirect. The former can be however fully neglected. On the other hand, the indirect influence caused by "the interaction of the carrier with the PA memory" cannot be neglected when the PA has not enough wideband frequency characteristics. The latter effect mentioned causes changes in the carrier phase that are received as the phase changes of the baseband modulating signal. Keywords-Saleh's and related models of AM/AM and AM/PM conversions and their classifications, power amplifiers, memory effects I. INTRODUCTIONOWER amplifiers (PAs) used in wireless communications, such as satellite communication systems [1], produce nonlinear distortions in their operating regimes, which are selected so as to be slightly nonlinear. These distortions manifest themselves in the occurrence of the so-called amplitude-to-amplitude (AM/AM) and amplitude-to-phase (AM/PM) conversions, among other distortion products. Our focus here is on the AM/AM and AM/PM distortions.One of the most popular models used to model the AM/AM and AM/PM distortions of PAs was published by Saleh in [2]. It is one of the representatives of a whole class of descriptions modeling the AM/AM and AM/PM conversions, which are listed and classified as "system-level models without memory effect" in a tutorial paper [3].