From post-distortion to pre-distortion for power amplifiers linearization

This letter presents a new method of digital adaptive pre-distortion for linearization of power amplifiers (PA). The method is derived from a post-distortion approach which identifies the PA inverse function. This approach leads to the minimization of a quadratic function of the polynomial coefficients in the case of a polynomial predistorter form and a least square criterion. We have compared our solution to a method previously proposed by Ghaderi (1996) that was also based on the transformation of a post-distortion into a pre-distortion system. We have tested our predistorter (along with a baseband adaptation of Ghaderi´s) on OFDM Hiperlan signals. Both methods significantly reduced the signal distortion and the spectral regrowth. Our less complex approach proved to be even better for small peak back off values.