Enhanced decision feedback equalization

The author describes a detection technique, enhanced decision feedback equalization (EDFE), which is well matched to the magnetic recording channel. EDFE involves a combination of both decision feedback equalization (DFE) and look-ahead detection. The implementation of EDFE is similar to that of DFE. The sampled transition response factors into (1+D/4)/(1-D/2), suggesting that the required response can be formed by some pulse slimming and slight phase adjustment, 1+D/4, followed by a single-pole RC characteristic at some 11% of the clock rate which will produce the exponential tail, 1/(1-D/2). Evaluation of the asymptotic SNR (signal-to-noise ratio) shows that EDFE is better than or comparable to several other detectors on a Lorenzian channel. The look-ahead feature which distinguishes EDFE from conventional DFE is responsible for a performance improvement approaching 1 dB. At very high density and at very low density, the performance of EDFE is less attractive. The performance of EDFE at PW50=2.5T is comparable to that of EPRML (extended class IV partial response maximum-likelihood detection), and EDFE is much easier to implement