Method and apparatus for determining read-head deviation using orthogonal preambles

A method of operating a storage device having a storage medium, the method comprising:

• writing user data in a shingled manner to two adjacent tracks on the storage medium, including writing patterns on each track so that the pattern on a first one of the two adjacent tracks and the pattern on a second one of the two adjacent tracks are mutually exclusive;
• detecting, with a first read head in a first position during a pass, signals from the two adjacent tracks;
• detecting, with a second read head in a second position during the pass, signals from the two adjacent tracks;
• analyzing outputs of the first read head and the second read head to derive, from the signals from the two adjacent tracks detected by the first read head during the pass, and from the signals from the two adjacent tracks detected by the second read head during the pass, the user data that was written to the two adjacent tracks.

A storage device comprising:

• read circuitry including:
• a first read head and a second read head, the first read head having a first detector that outputs a first signal representing data detected, during a pass, from a first one of two adjacent tracks that are written in a shingled manner, and a second one of the two adjacent tracks, and a second detector that outputs a second signal representing data detected, during the pass, from the first one of the two adjacent tracks, and the second one of the two adjacent tracks, data on each track including a pattern outside servo wedges of the storage device, wherein the pattern on the first one of the two adjacent tracks, and the pattern on the second one of the two adjacent tracks, are mutually exclusive;
• respective Discrete Fourier Transform circuits to identify components in the signals, derived from the patterns in the user data outside the servo wedges of the storage device, corresponding to respective frequencies characteristic of the pattern on the first one of the two adjacent tracks, and the pattern on the second one of the two adjacent tracks;
• and
• computation circuitry to determine from the components, derived during the pass, the user data that were written to the first one of the two adjacent tracks, and the second one of the two adjacent tracks.