Reducing effect of frequency acquisition error in a position error signal responsive to split servo burst patterns
In a servo control loop, servo burst signals that are read from a plurality of servo burst patterns that include a split servo burst pattern contain frequency acquisition error. The frequency acquisition error is at least partially removed to generate a frequency acquisition error compensated position error signal (PES).
1. A circuit comprising:
a demodulation module that at least partially removes an effect of frequency acquisition error on a position error signal (PES) using servo readback signals read from a sequence of at least one part of a split first servo burst pattern, a second servo burst pattern, and another part of the split first servo burst pattern on a moving storage media to generate a frequency acquisition error compensated PES component.
2. The circuit of claim 1 , wherein the demodulation module generates a sinusoidal component vector for each of the parts of the split first servo burst pattern and for the second servo burst pattern.
3. The circuit of claim 1 , wherein the demodulation module combines the component vectors for each of parts of the split first servo burst pattern to generate a synthetic component vector that represents a combination of the parts of the split first servo burst pattern.
4. The circuit of claim 3 , wherein the demodulation module interpolates among phase angles of the parts of the split first servo burst pattern to generate the synthetic component vector.
5. The circuit of claim 4 , wherein the demodulation module averages the phase angles of the parts of the split first servo burst pattern to generate the synthetic component vector.
6. The circuit of claim 3 , wherein the demodulation module determines a rotation matrix with a phase angle that reduces a sum of squares of the first and second synthetic cosine components.
7. The circuit of claim 6 , wherein the demodulation module rotates the first and second synthetic pairs of sine and cosine components in response to the rotation matrix to generate phase rotated synthetic pairs of sine and cosine components, and generates the frequency acquisition error compensated PES component using the phase rotated synthetic pairs of sine and cosine components.
8. The circuit of claim 1 , wherein the demodulation module generates pairs of sine and cosine components for each of the parts of the split first servo burst pattern and for the second servo burst pattern, and determines frequency acquisition error in response to a phase relationship between the pairs of sine and cosine components.
9. The circuit of claim 8 , wherein the demodulation module interpolates among the pairs of sine and cosine components for each of the parts of the split first servo burst pattern to generate a synthetic pair of sine and cosine components.
10. The circuit of claim 9 , wherein the demodulation module averages the pairs of sine and cosine components for each of the parts of the split first servo burst pattern to generate the synthetic pair of sine and cosine components.
11. The circuit of claim 9 , wherein the demodulation module determines a rotation matrix with a phase angle that reduces a sum of squares of the first and second synthetic cosine components.
12. The circuit of claim 11 , wherein the demodulation module rotates the first and second synthetic pairs of sine and cosine components in response to the rotation matrix to generate phase rotated synthetic pairs of sine and cosine components, and generates the frequency acquisition error compensated PES component using the phase rotated sine and cosine components.
13. The circuit of claim 1 , wherein the demodulation module generates a sinusoidal component vector for each part of the split first and second servo burst patterns, interpolates among phase angles of the parts of the first servo burst pattern to generate a first synthetic component vector, interpolates among phase angles of the parts of the second servo burst pattern to generate a second synthetic component vector, determines a rotation matrix with a phase angle that reduces a sum of squares of the first and second synthetic cosine components, rotates the first and second synthetic pairs of sine and cosine components in response to the rotation matrix to generate phase rotated synthetic pairs of sine and cosine components, and generates the frequency acquisition error compensated PES component using the phase rotated first and second synthetic pairs of sine and cosine components.
14. The circuit of claim 13 , wherein the demodulation module generates pairs of sine and cosine components for each part of the split first and second servo burst patterns, interpolates among the pairs of sine and cosine components of the split first servo burst patterns to generate a first synthetic pair of sine and cosine components, interpolates among the pairs of sine and cosine components of the split second servo burst patterns to generate a second synthetic pair of sine and cosine components, determines a rotation matrix with a phase angle that reduces a sum of squares of the first and second synthetic cosine components, and rotates the first and second synthetic pairs of sine and cosine components in response to the rotation matrix to generate phase rotated synthetic pairs of sine and cosine components, and generates the frequency acquisition error compensated PES component using the phase rotated synthetic pairs of sine and cosine components.
15. The circuit of claim 1 , wherein the at least one part of a split first servo burst pattern and the another part of the split first servo burst pattern are spaced apart along one side of a track centerline with the second servo burst pattern on another side of the track centerline and positioned between the split first servo burst pattern parts.
16. A method comprising:
at least partially removing an effect of frequency acquisition error on a position error signal (PES) using a sequence of at least one part of a split first servo burst pattern, a second servo burst pattern, and another part of the split first servo burst pattern on a moving storage media to generate a frequency acquisition error compensated PES component.
17. The method of claim 16 , further comprising:
generating a sinusoidal component vector for each of the parts of the split first servo burst pattern and for the second servo burst pattern;
interpolating among phase angles of the parts of the split first servo burst pattern to generate a synthetic component vector; and
determining a phase angle that reduces a sum of squares of the synthetic component vector and the component vector for the second servo burst pattern.
18. The method of claim 17 , further comprising:
rotating the synthetic component vector and the component vector for the second servo burst pattern in response to the determined phase angle to generate phase rotated component vectors; and
generating the frequency acquisition error compensated PES component using the phase rotated component vectors.
19. The method of claim 16 , further comprising:
generating pairs of sine and cosine components for each of the parts of the split first servo burst pattern and for the second servo burst pattern;
interpolating among the pairs of sine and cosine components of the part of the split first servo burst pattern to generate a synthetic pair of sine and cosine components;
determining a phase angle that reduces a sum of squares of the synthetic cosine component and the cosine component for the second servo burst pattern; and
rotating the synthetic sine and cosine components and the sine and cosine components for the second servo burst pattern in response to the determined phase angle to generate phase rotated sine and cosine components; and
generating the frequency acquisition error compensated PES component using the phase rotated sine and cosine components.
20. A system comprising:
a demodulator that at least partially removes an effect of frequency acquisition error on a position error signal (PES) using a sequence of servo burst patterns along a track to generate a compensated PES component, the sequence of servo burst patterns including at least one part of a split first servo burst pattern, a second servo burst pattern, and another part of the split first servo burst pattern; and
a controller that controls movement of a read/write head relative to the track on a storage media in response to the frequency acquisition error compensated PES component.