Fixed sample rate Bayesian detector in a variable speed magnetic channel

A new design of blind equalizer is proposed that can decode a magnetic binary channel whose bit-rate is unknown. It is shown that the velocity can be estimated from information already known from a fixed delay tree search (FDTS) decision feedback equalizer (DFE) structure. Converting this detector to a Bayesian scheme with an appreciation of non-linear distortion in the read head modestly improves the velocity stability. The acquisition time for the channel speed is linear and rapid: a 50% change in velocity can be accommodated in fewer than 150 magnetic flux transitions. Results with real signals from a high-density magnetic credit card are provided.