Gain and phase constrained adaptive equalizing filter in a sampled amplitude read channel for magnetic recording

摘要

A sampled amplitude read channel for magnetic disk recording which asynchronously samples (24) the analog read signal, adaptively equalizes (B103) the resulting discrete time sample values according to a target partial response, extracts synchronous sample values through interpolated timing recovery (B100), and detects digital data from the synchronous sample values using a Viterbi sequence detector (34) is disclosed. To minimize interference from the timing and gain control loops, the phase and magnitude response of the adaptive equalizer filter (B103) are constrained at a predetermined frequency using an optimal orthogonal projection operation as a modification to a least mean square (LMS) adaptation algorithm.