Mitigating the Effects of Track Mis-Registration in Single-Reader/Two-Track Reading BPMR Systems

Abstract

Bit-recording technologies that can provide areal densities (ADs) [patterned magnetic recording (BPMR) is expected to be one of the new magnetic ADs] of 1 Tera-bit per square inch or higher. To achieve these ADs, the space between tracks must be reduced, bringing them closer and closer together, leading to significant inter-track interference (ITI). Track mis-registration (TMR) or head offset can further degrade overall system performance. To mitigate the effects of ITI and TMR, we propose using a single-reader/two-track reading (SRTR) scheme together with an over-sampling technique on a staggered BPMR system. We also propose a TMR estimation technique based on a readback signal. Here, the readback signal is separated into two sequences, one odd and one even. Then, the energy ratio is calculated using these data sequences. The obtained relationship between the energy ratio and head offset can be utilized to predict the actual head offset occurrence in the reading process. Finally, a pairing of a monic constraint target and an equalizer that accordingly matches each estimated head offset level is adopted to deal with the TMR effect. The SRTR system can provide better bit-error-rate (BER) performance. Moreover, when TMR effects appear in the reading process, our proposed SRTR system with a TMR mitigation technique can yield better BER performance, especially at high head offset levels.