An EPRML digital read/write channel IC

Abstract

Extended partial-response (EPR) signaling together with suitable encoding and maximum-likelihood (ML) detection may be employed in magnetic recording systems to achieve higher storage densities than peak detection or Class 4 partial-response maximum-likelihood (PRML) methods. Heretofore, the complexity of a complete EPRML implementation has been deemed too high, and efforts have been directed primarily at approximating EPRML performance with modified PRML hardware. This channel IC combines extended class 4 partial response (EPR4) equalization with ML sequence detection based on the Viterbi algorithm. The EPR4 signal is well-matched to the typical readback signal in the range of normalized user densities of current and future interest, simplifying the equalizer. Anti-aliasing filtering and equalization are combined in a continuous-time filter, eliminating a FIR filter.