Optimal Array-Reader and Track Misregistration Mitigation Method in a Three-Reader/Four-Track Reading Bit-Patterned Magnetic Recording System

Abstract

Track misregistration (TMR) is one of several problems in ultrahigh areal density bit-patterned magnetic recording (BPMR) systems, in which the distances between bit-islands are very narrow in both cross-track and down-track directions. Unfortunately, distance reduction leads to intersymbol interference and intertrack interference (ITI) effects, which cause system performance degradation. To deal with these effects, we develop the optimal position of an array-reader based on a three-reader/four-track reading BPMR system that is combined with a simple two-dimensional rate-3/4 modulation code and ITI subtraction technique, which delivers the best avoidance of the ITI effect from sidetracks. We model TMR estimation and mitigation methods using readback signals that are obtained from the optimal array-readers to improve bit error rate (BER) performance. The variance-ratio of these readback signals is used to estimating the TMR levels, whereas a pair of the target's and equalizer's coefficients, accordingly designed to the estimated TMR levels, is adopted for mitigating the TMR effect. Simulation results show that our methods provide a high TMR estimation accuracy and gain a superior BER performance compared with the recording system without these techniques under the same user density.