An algorithm for the stable operation of a digitally-implemented fractionally-spaced adaptive equalizer

A digitally-implemented fractionally-spaced equalizer will generally exhibit long-term instability when the conventional tap-adjustment algorithm is used. This occurs because, in contrast to the synchronous equalizer, a fractionally-spaced equalizer will generally have many sets of tap values which result in nearly equal values of mean-squared error. Some of these tap settings are large enough to cause register overflows and consequent performance deterioration. In this paper we report how a simple modification in the tap-adjustment algorithm provides a solution to the above problem.