Blind Equalisation with Recursive Filter Structures

Most blind equalisation algorithms are realised using adaptive transversal filters (FIR). This paper presents alternative recursive filter structures for equalisation of severely distorted channels. Such architectures are pursued by separating the equaliser into a cascade of a recursive prewhitening filter adapted with second-order statistics and a phase equaliser adapted with higher-order statistics. We address the problem of poles outside the unit circle in the z-plane, which is found in a recently proposed gradient descent implementation, and suggest an improved algorithm. Also a new approach, that uses a cascade of a block adaptive prewhitening filter and the block adaptive eigenvector approach (EVA), is presented.