Decision feedback equalization for channels with error correcting capabilities

The sector error rate (SER) of the decision feedback equalizer (DFE) is analyzed for digital magnetic recording applications. In contrast to the detector bit error rate, the sector error rate is the probability of at least one bit error in a sector of N bits, after application of an error correcting code (ECC). Due to error propagation, the DFE produces long error bursts that exceed the typical correcting capabilities of hard disk drive ECC systems. We characterize this impairment in terms of the loss in recording density. We propose new optimization criteria that limit the energy of the DFE feedback filter, slightly increasing the probability of a burst error but greatly decreasing the probability of an uncorrectable burst. The constrained DFE regains 75% of the density lost to error propagation. Alternatively, the constraint provides up to 5 orders-of-magnitude in SER margin on a Lorentzian channel at a density of PW₅₀=3.0 T