<title>Tracking ability of L-level MLP-based equalizers in nonlinear microwave radio channels in the presence of multipath fading</title>

Abstract

The performance of microwave digital radio systems is severely degraded by multipath fading and also by the nonlinear power amplifier at the transmiUer, the combined effects of these result in a time varying non-linear channel. In this paper, the multilayer perceptron (MLP) based equalizer is investigated for use on such channels. It is found to ouperform the conventional approach, that is, the use of a transversal equalizer at the receiver operating with a signal predistorter placed before the non-linear power amplifier at the transmitter. An L-level non-linear function is used as a node activation for the MLP. Two update schemes are investigated, one being a complex version of the back propagation algorithm, the other a complex version ofthe delta-bar-delta algorithm.