Data storage device defining track trajectory to reduce AC track squeeze
A data storage device is disclosed comprising a head actuated over a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments. First data is written to a first data segment of a first data track, and second data is written to a second data segment of a second data track. After writing the second data, a quality metric is measured for at least two off-track offsets of the first data segment. A track pitch is estimated between the first data segment and the second data segment based on the quality metrics, and a track trajectory is generated for the second data segment based on the estimated track pitch. Third data is written to the second data segment based on the track trajectory.
1. A data storage device comprising:
a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments;
a head actuated over the disk; and
control circuitry configured to:
write first data to a first data segment of a first data track;
write second data to a second data segment of a second data track;
after writing the second data, measure a quality metric for at least two off-track offsets of the first data segment;
estimate a track pitch between the first data segment and the second data segment based on the quality metrics;
generate a track trajectory for the second data segment based on the estimated track pitch; and
write third data to the second data segment based on the track trajectory.
2. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to generate the track trajectory by generating a repeatable runout (RRO) value for the second data segment based on the estimated track pitch.
3. The data storage device as recited in claim 1 , wherein the second data segment at least partially overlaps the first data segment of the first data track.
4. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to generate the track trajectory to achieve a target track pitch for the first data segment relative to the second data segment.
5. The data storage device as recited in claim 1 , wherein the quality metric comprises an error rate when reading the first data segment.
6. The data storage device as recited in claim 1 , wherein:
the first data consists of a first periodic pattern consisting of a first frequency of transitions;
the second data consists of a second periodic pattern consisting of a second frequency of transitions; and
the quality metric comprises a signal-to-noise (SNR) measurement.
7. The data storage device as recited in claim 1 , wherein the control circuitry is further configured to:
estimate a turning point in a cross-track profile of the quality metrics;
estimate a width of the cross-track profile based on the turning point; and
estimate the track pitch between the first data segment and the second data segment based on the estimated width of the cross-track profile.
8. The data storage device as recited in claim 7 , wherein the control circuitry is further configured to estimate the turning point by curve fitting the measured quality metrics to the cross-track profile.
9. A data storage device comprising:
a disk comprising servo data for defining a plurality of data tracks, wherein each data track comprises a plurality of data segments;
a head actuated over the disk; and
a means for writing first data to a first data segment of a first data track;
a means for writing second data to a second data segment of a second data track;
after writing the second data, a means for measuring a quality metric for at least two off-track offsets of the first data segment;
a means for estimating a track pitch between the first data segment and the second data segment based on the quality metrics;
a means for generating a track trajectory for the second data segment based on the estimated track pitch; and
a means for writing third data to the second data segment based on the track trajectory.