An extended dual decision-feedback equalizer for high-density perpendicular magnetic recording channels

Partial-response maximum-likelihood (PRML) systems are powerful and indispensable for high-density perpendicular magnetic recording channels. However, high-order partial-response (PR) targets must be considered because of severe intersymbol interference (ISI). On the other hand, decision feedback equalization (DFE) has very low complexity. DFE can be used with high code rate modulation codes, thanks to the fact that DFE does not use a minimum run constraint as a multilevel DFE (MDFE). At high recording densities, dual detection schemes such as dual DFE (DDFE) significantly improve performance and reduce error propagation. So, we compare DDFE detectors with PR(1221)ML and PR(12321)ML on 16/17 maximum transition run (MTR) (3,11)-coded perpendicular magnetic recording channels and propose an extended DDFE that represents a dual version of the DDFE. Simulation results show that the DDFE has a bit-error-rate (BER) performance comparable to that for PR(12321)ML. Our extended DDFE in turn shows a performance gain over DDFE and PR(12321)ML at the normalized recording densities 3 and 4.