Jonathan Darrel Coker

2-D Magnetic Recording: Progress and Evolution

Two-dimensional magnetic recording (TDMR) was proposed in 2008 as a means of pushing beyond 1 Tbit/in2 areal-density yet staying with relatively conventional magnetic components. A density of approximately 1 Tbit/in2 is considered to be the limit for conventional perpendicular magnetic recording. The original concept for TDMR has evolved greatly since it was originally proposed. This evolution has occurred as more information has become available about the characteristics of shingled tracks and 2-D read-back signals and as constraints have become apparent in the implementation of recording components and electronics. With todays technology, the projected gains are smaller than originally envisioned. As a very practical first step that introduces TDMR and provides modest gains without incurring undue complexity or cost, this paper focuses on the idea of a stacked two-element reader operating on shingled magnetic recording tracks and a two-input equalizer feeding a standard data detector. The dual-reader gains are assessed based on combining waveforms captured from a single reader at many off-track positions, track-pitches, and radii.

Precompensation value determination in a PRML channel

This paper describes a technique for determining precomp value in a disk drive with a PRML data channel. Unlike other known methods, this approach uses the PRML sample values to derive the needed precomp value and requires very little additional hardware. Therefore a disk drive can easily incorporate this technique for precomp adjustment.