Pre-distortion of non-linear devices by post-detection

Abstract

A method and an arrangement is disclosed for linearizing the output signal from an inherently non-linear device, e.g. an amplifier, producing intermodulation or non-linear products. A pre-distorter having a unity transfer function is located between a signal input and the input of the inherently non-linear device. Furthermore a second device forming a post-distorter is coupled to the output of the nonlinear device in a way to be able to handle the amplified output signal or a portion of the output signal. According to the present method the post-distorter is optimized to give as output the same signal spectrum content as what is input to the non-linear device, whereafter the achieved parameters of the post-distorter are transferred to the pre-distorter. In other words a copy of the optimized post-distorter is then used as a pre-distorter in front of the non-linear device to obtain an improved output signal in terms of signal quality from the inherently non-linear device. The post-distorter is then optimized once more and parameters are again transferred to the pre-distorter as a further as a further small correction. In operation this is then generally repeated in a suitable scheduled way to give an ongoing correction to the pre-distortion. The pre-distorter and post-distorter may both be either digital devices or analog devices.