Stable whitening matched filters based on Nehari's approximation

Abstract

Trellis based equalisers provide a good tradeoff between complexity and performance in the equalisation of time dispersive communication channels. In order to induce the best performance from such equaliser structures, it is desirable that the overall communication channel be minimum-phase. The Whitening Matched Filter required to minimise the phase-delay of a mixed-phase channel is known to be completely unstable. This paper looks at the use of Nehari's Approximation as a method of finding the closest stable approximation in the uniform frequency (L∞) sense. It is concluded that such a direct approximation does not result in significant phase-delay improvements and the inclusion of smoothing time delays may improve performance. © 2005 IEEE.