A robust detector based on combination of PR1 and EEPR4 for perpendicular magnetic recording

In perpendicular magnetic recording (PMR), we require a PR1 detector that can withstand the DC level shift caused by thermal asperity and other factors. In general, the DC level shift can be reduced by introducing a decision feedback equalizer (DFE) before the PR1 detector. A difficulty arises when the fluctuation of the magnetization transition area causes the so-called media noise such as jitter or the shift of edge positions of data series. Jitter-like noise essentially exhibits pattern-dependent properties because it depends on the edges of data series. Thus, we aim to develop a simple detector that can withstand jitter-like noise. The performance of the conventional PR1 detector is deteriorated significantly by a small DC level shift.