No abstract

An allpass forward equalizer (APFE) for use with decision feedback equalization (DFE) is described. The APFE has poles, unlike the normally implemented FIR (finite impulse response) forward equalizer; equalizers with poles can provide superior performance or reduced hardware complexity when compared to all-zero equalizers, but can have local optima and are more dimcult to design. A theoretical basis fair the allpass is presented and a systematic design procedure is described. It is shown that there are no local optima in a sufficient region about the global optimum such that adaptation is feasible. A performance vs. complexity advantage is shown for the APFE relative to the FIR forward equalizer, and implementation as a continuous-time filter is proposed.

No abstract

A technique for the construction of trellis codes that double the squared free Euclidean distance on the dicode (1-D) channel is presented. This technique uses periodic pruning and permutation of the trellis to ensure that a small detector path memory length is sufficient. Some high rate codes constructed using this technique are given.

Perpendicular recording is an alternative to longitudinal recording that shows promise in mitigating the super-paramagnetic limit. This channel passes DC and thus presents challenges to the read channel design. Compounding the problem, the MR head signal is susceptible to thermal asperities which manifest as low-frequency disturbances. We compare the performance of a DC-coupled PRML channel architecture which uses a non-DC-free target with a first-order DC loop to remove low-frequency disturbances to that of an alternate architecture that uses a DC-free target. We show through analysis and simulation results that the former architecture degrades with increasing latency of the DC loop and performs worse than the DC-free target for large latencies. In addition, the detection performance with DC-free target can be improved by the use of a block code with single parity bit.