Decision feedback equalizer with pattern dependent dynamic threshold

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 canceller is used to cancel the trailing nonlinear intersymbol interference (ISI), and a pattern dependent dynamic threshold is employed to handle the precursor nonlinear ISI. We compare the detection performance of this new detector, which we call DFE with dynamic threshold (DFE-DT), to that of the DFE and the DFE with a trailing nonlinear canceller only (DFE-NC) on several experimental channels. The results show that the DFE-DT yields significant performance improvement over the DFE and the DFE-NC as measured by the detection signal-to-noise ratio (SNR).