Decision feedback equalizer with pattern dependent threshold for magnetic recording channels

A new detector based on a practical nonlinear model for digital magnetic recording channels is described. The nonlinear model is easy to construct from simple measurements of the isolated transition response and dipulse responses. The new detector has a structure similar to that of the decision feedback equalizer (DFE) except that an add-on nonlinear canceler is used to cancel the trailing nonlinear intersymbol interference (ISI) and a pattern dependent threshold is employed to handle the precursor nonlinear ISI. We compare the detection performance of this new detector with that of the DFE on several experimental channels. The results show that the new detector yields significant performance improvement over its counterpart as measured by the detection signal to noise ratio (SNR).