Digital Predistortion of RF Power Amplifiers Considering the Group Delay Distortion

In this paper, a novel adaptive time alignment method for digital predistortion (DPD) is proposed to deal with the linearization of power amplifiers (PAs) when severer group delay distortion (GDD) exists in the feedback path. Group delay mismatch significantly influences the precision during the extraction of the DPD model's coefficients. Based on the mathematical analysis of group delay, the proposed method can weaken the effects of GDD. Experiments' results confirm that the DPD model with the proposed method has better performance than the DPD model only with the traditional time alignment method.

I. Introduction

The contradiction between linearity and efficiency of the power amplifier (PA), generally working near the saturation region, introduces nonlinear distortion to the radio frequency (RF) transmitters. Digital predistortion (DPD) is a widely used and effective technology for PA linearization. Many conventional DPD models considering both the memory effect and nonlinear effect have been proposed, e.g., the generalized memory polynomial (GMP) model [1] and cascaded model [2].