A new digital predistorter linearizer for wide band signals

Abstract

This paper presents a new method of digital adaptive predistortion for linearization of high-power amplifiers (HPAs) that mitigates linearization performance deterioration due to bandwidth limitation of feedback path. With increases of signal bandwidth, the effects of limited bandwidth of the predistorter feedback path cannot be ignored. In the proposed algorithm, adaptation is derived from direct learning for the lookup table (LUT) gains. According to the proposed approach, when the LUT contents are adapted according to an LMS algorithm, several other LUT entries adjacent to the currently processed entry are also updated. However, the level of adaption for adjacent entries is less than for the currently processed entry. This level is defined by the preselected window weight function. The proposed algorithm makes it possible to design a low-complexity, memoryless adaptive predistortion system with narrowband feedback path to compensate for the nonlinearity of an HPA.