Joint Equalization of Asynchronous Reads in Array-Reader-Based Interlaced Magnetic Recording

This paper proposes a joint read equalization scheme for interlaced magnetic recording (IMR) employing an array of readers, where multi-reader captured waveforms from asynchronously recorded tracks are jointly processed for single or multiple track data retrievals. In the array-reader-based IMR (ARIMR), the inter-track interference (ITI) collected from one reader is not necessarily synchronized to the other readers, especially in the case of a large cross-track separation (CTS) between the readers due to the linear density differentiation between the neighboring tracks. For the efficient mitigation of such asynchronous ITIs, an effective resampling-based joint equalization scheme is proposed in this paper, where multiple readbacks are digitally synchronized for designated target tracks, and joint processing of them suppresses the ITI in the equalized output. Furthermore, the proposed effective synchronization can be applied for joint multi-track retrievals when the CTS of the array reader is closed to the track pitch. For performance evaluations of the proposed joint read equalization scheme, numerical ARIMR channel simulations by the micro-pixelated magnetic channel model are conducted, and a bit error rate performance is evaluated under various configurations. In addition, waveforms captured from a dual-reader hard disk drive are evaluated with the proposed joint read equalization schemes for practical performance measurements of ARIMR. In both evaluations, unfavorable CTS conditions are investigated to account for the dominant skew effect in ARIMR, where the proposed joint equalization scheme enhances the off-track capability performance, especially with the customized configurations of interlaced recording. In overall, ARIMR with joint read equalization shows the potential of an areal density capability gain and a doubling of the data transfer rate over the conventional perpendicular magnetic recording and legacy IMR.