Disk drive selecting TPI profile by estimating head geometry

A disk drive comprising:

• a disk;
• a head actuated radially over the disk;
• and
• control circuitry operable to:
• position the head over a first radial location;
• select a first data tracks per inch (TPI_1) for data tracks recorded near the first radial location;
• position the head over a second radial location;
• select a second data tracks per inch (TPI_2) for data tracks recorded near the second radial location;
• position the head over a third radial location;
• select a third data tracks per inch (TPI_3) for data tracks recorded near the third radial location;
• estimate a geometry of the head in response to TPI_1, TPI_2, and TPI_3;
• and
• select at least one of TPI_1, TPI_2 and TPI_3 by:
• writing data to a plurality of victim data tracks, wherein each victim data track is separated by at least one aggressor data track;
• reading the victim data tracks and measure a first bit error rate of the victim data tracks;
• writing data to the aggressor data tracks;
• and
• reading the victim data tracks and measure a second bit error rate of the victim data tracks.

A method of estimating a geometry of a head in a disk drive, the disk drive comprising a disk, and the head actuated over the disk, the method comprising:

• positioning the head over a first radial location;
• selecting a first data tracks per inch (TPI_1) for data tracks recorded near the first radial location;
• positioning the head over a second radial location;
• selecting a second data tracks per inch (TPI_2) for data tracks recorded near the second radial location;
• positioning the head over a third radial location;
• selecting a third data tracks per inch (TPI_3) for data tracks recorded near the third radial location;
• and
• estimating the geometry of the head in response to TPI_1, TPI_2 and TPI_3,
• wherein:
• the first radial location is near a middle diameter of the disk;
• the second and third radial locations are near one of an inner diameter of the disk and an outer diameter of the disk;
• the head comprises a write width WW0 estimated according to 1/(TPI_1·cos αs1), where αs1 is a head skew angle at the first radial location:
• the head further comprises a bevel angle α and a pole height H;
• the bevel angle α and the pole height H are estimated according to a two variable equation:
• TPI—2=[WW0·cos·(αs2)+H·sin(αs2−a)/cos(α)]−1
• TPI—3=[WW0·cos·(αs3)+H·sin(αs3−α)/cos(α)]−1
• where:
• αs2 is a head skew angle at the second radial location;
• αs3 is a head skew angle at the third radial location;
• and
• α and H are computed by solving the two variable equation in response to TPI_2 and TPI_3.

A method of estimating a geometry of a head in a disk drive, the disk drive comprising a disk, and the head actuated over the disk, the method comprising:

• positioning the head over a first radial location;
• selecting a first data tracks per inch (TPI_1) for data tracks recorded near the first radial location;
• positioning the head over a second radial location;
• selecting a second data tracks per inch (TPI_2) for data tracks recorded near the second radial location;
• positioning the head over a third radial location;
• selecting a third data tracks per inch (TPI_3) for data tracks recorded near the third radial location;
• and
• estimating the geometry of the head in response to TPI_1, TPI_2 and TPI_3,
• wherein:
• the first radial location is near a middle diameter of the disk;
• the second and third radial locations are near one of an inner diameter of the disk and an outer diameter of the disk;
• and
• selecting at least one of TPI_1, TPI_2 and TPI_3 comprises:
• writing data to a plurality of victim data tracks, wherein each victim data track is separated by at least one aggressor data track;
• reading the victim data tracks and measure a first bit error rate of the victim data tracks;
• writing data to the aggressor data tracks;
• and
• reading the victim data tracks and measure a second bit error rate of the victim data tracks.