A Novel Reduced Order RLS Predistortion

Abstract

In this paper, a new structure of predistorter, which composed of a rational function and polynomial function, is presented for solving the nonlinear distortion of power amplifier. Amplitude predistorter is implemented by rational function and phase predistorter polynomial function. First, the rational function is transformed into polynomial function structure. Thus, the basic idea of the reduced order RLS based polynomial predistortion algorithm is used, system structure is same to original, only the algorithm of adaptation process is modified to approximate the target function with two simpler functions. A complex function is decomposed into two simpler functions so that we can compute the RLS algorithm with much less complexity. Using reduced order RLS algorithm, the proposed structure of predistorter show superior performance compared to the conventional RLS rational function predistortion with the same computational complexity or with the same number of coefficient.