Understanding Sources of Errors in Bit-Patterned Media to Improve Read Channel Performance

The limitations of current lithographic techniques result in a variation of the geometry of the fabricated islands in bit-patterned media. These variations give rise to jitter in the replay waveform that has a detrimental effect on the recovery of stored data. By analyzing experimental bit-patterned media, we show that the presence of lithography jitter can be quantified in terms of variations in the size and position of the islands, which can be seen to be Gaussian-like in nature. In addition, the amount of jitter increases as the periodicity and size of the islands reduces, confirming that lithography jitter will be a significant source of noise in any future storage system incorporating bit-patterned media. By using a comprehensive read channel model we demonstrate that a novel trellis structure offers improved read channel performance in the presence of island position variations.