Multi-frequency servo bursts in magnetic disc memory system

A system for positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first servo burst disposed on the track, characterized by a first frequency, and (ii) a second servo burst disposed on the track, characterized by a second frequency, said magnetic disc medium comprising:

• a multi-frequency filter for receiving a composite readback signal from the read/write head and for separating the composite readback signal into a first readback signal corresponding to the first servo burst and a second readback signal corresponding to the second servo burst;
• an envelope detector for providing a first amplitude signal corresponding to an amplitude of the first readback signal, and for providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• a comparator for comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• a servo control system for receiving the error signal and generating a drive signal therefrom;
• and,
• a positioner assembly, coupled to the read/write head, for adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A system for positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first set of servo bursts adjacently disposed on the tracks along a first axis perpendicular to the centerlines, wherein each of the first set of servo bursts is disposed on an individual track, from the inside track edge to the outside track edge, and a frequency characteristic associated with each of the servo bursts alternates between a first frequency and a second frequency for consecutive servo bursts, and (ii) a second set of servo bursts adjacently disposed on the tracks along a second axis perpendicular to the centerlines and parallel to the first axis, wherein each of the second set of servo bursts is disposed on two adjacent tracks, from the centerline of one track to the centerline of a next adjacent track, and a frequency characteristic associated with each of the second set of servo bursts alternates between the first frequency and the second frequency for consecutive servo bursts, said magnetic disc medium comprising:

• a multi-frequency filter for receiving a composite readback signal from the read/write head and for separating the composite readback signal into a first readback signal corresponding to servo bursts characterized by the first frequency and a second readback signal corresponding to servo bursts characterized by the second frequency;
• an envelope detector for providing a first amplitude signal corresponding to an amplitude of the first readback signal, and for providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• a comparator for comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• a servo control system for receiving the error signal and generating a drive signal therefrom;
• and,
• a positioner assembly, coupled to the read/write head, for adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A system for positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first set of servo bursts adjacently disposed on the tracks along a first axis perpendicular to the centerlines, wherein each of the first set of servo bursts is disposed on an individual track, from the inside track edge to the outside track edge, and a frequency characteristic associated with each of the servo bursts alternates between a first frequency and a second frequency for consecutive servo bursts, and (ii) a second set of servo bursts adjacently disposed on the tracks along a second axis perpendicular to the centerlines and parallel to the first axis, wherein each of the second set of servo bursts is disposed on two adjacent tracks, from the centerline of one track to the centerline of a next adjacent track, and a frequency characteristic associated with each of the second set of servo bursts alternates between the first frequency and the second frequency for consecutive servo bursts, comprising:

• filtering means for receiving a composite readback signal from the read/write head and for separating the composite readback signal into a first readback signal corresponding to servo bursts characterized by the first frequency and a second readback signal corresponding to servo bursts characterized by the second frequency;
• detection means for providing a first amplitude signal corresponding to an amplitude of the first readback signal, and for providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• comparison means for comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• control means for receiving the error signal and generating a drive signal therefrom;
• and,
• positioning means, coupled to the read/write head, for adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A system for positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first set of servo bursts adjacently disposed on the tracks along a first axis perpendicular to the centerlines, wherein each of the first set of servo bursts is disposed on an individual track, from the inside track edge to the outside track edge, and a frequency characteristic associated with each of the servo bursts alternates between a first frequency and a second frequency for consecutive servo bursts, and (ii) a second set of servo bursts adjacently disposed on the tracks along a second axis perpendicular to the centerlines and parallel to the first axis, wherein each of the second set of servo bursts is disposed on two adjacent tracks, from the centerline of one track to the centerline of a next adjacent track, and a frequency characteristic associated with each of the second set of servo bursts alternates between the first frequency and the second frequency for consecutive servo bursts, comprising:

• an upconverter for receiving the readback signal, and for shifting the frequency spectrum associated with the readback signal to a higher frequency range so as to provide an up-shifted readback signal;
• a downconverter for receiving the up-shifted readback signal, for shifting a frequency spectrum associated with the up-shifted readback signal to a lower frequency range so as to provide a down-shifted readback signal;
• a multi-frequency filter for receiving the down-shifted readback signal from the downconverter and for separating the composite readback signal into a first readback signal corresponding to servo bursts characterized by the first frequency and a second readback signal corresponding to servo bursts characterized by the second frequency;
• an envelope detector for providing a first amplitude signal corresponding to an amplitude of the first readback signal, and for providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• a comparator for comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• a servo control system for receiving the error signal and generating a drive signal therefrom;
• and,
• a positioner assembly, coupled to the read/write head, for adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A method of positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first set of servo bursts adjacently disposed on the tracks along a first axis perpendicular to the centerlines, wherein each of the first set of servo bursts is disposed on an individual track, from the inside track edge to the outside track edge, and a frequency characteristic associated with each of the servo bursts alternates between a first frequency and a second frequency for consecutive servo bursts, and (ii) a second set of servo bursts adjacently disposed on the tracks along a second axis perpendicular to the centerlines and parallel to the first axis, wherein each of the second set of servo bursts is disposed on two adjacent tracks, from the centerline of one track to the centerline of a next adjacent track, and a frequency characteristic associated with each of the second set of servo bursts alternates between the first frequency and the second frequency for consecutive servo bursts, comprising:

• receiving a composite readback signal from the read/write head and separating the composite readback signal into a first readback signal corresponding to servo bursts characterized by the first frequency and a second readback signal corresponding to servo bursts characterized by the second frequency;
• providing a first amplitude signal corresponding to an amplitude of the first readback signal, and providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• receiving the error signal and generating a drive signal therefrom;
• and,
• adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A system for positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first servo burst disposed on the track, characterized by a first frequency, such that the first servo burst begins near a centerline associated with the track and extends in a first direction perpendicular to the centerline towards a first track edge, and (ii) a second servo burst disposed on the track, characterized by a second frequency, such that the second servo burst begins near the centerline and extends in a second direction perpendicular to the centerline towards a second track edge, comprising:

• filter means for receiving a composite readback signal from the read/write head and for separating the composite readback signal into a first readback signal corresponding to the first servo burst and a second readback signal corresponding to the second servo burst;
• detection means for providing a first amplitude signal corresponding to an amplitude of the first readback signal, and for providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• comparison means for comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• control means for receiving the error signal and generating a drive signal;
• and,
• positioning means, coupled to the read/write head, for adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A system for positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first servo burst disposed on the track, characterized by a first frequency, such that the first servo burst begins near a centerline associated with the track and extends in a first direction perpendicular to the centerline towards a first track edge, and (ii) a second servo burst disposed on the track, characterized by a second frequency, such that the second servo burst begins near the centerline and extends in a second direction perpendicular to the centerline towards a second track edge, comprising:

• an upconverter for receiving the readback signal, and for shifting the frequency spectrum associated with the readback signal to a higher frequency range so as to provide an up-shifted readback signal;
• a downconverter for receiving the up-shifted readback signal, for shifting a frequency spectrum associated with the up-shifted readback signal to a lower frequency range so as to provide a down-shifted readback signal;
• a multi-frequency filter for receiving the down-shifted readback signal from the downconverter and for separating the composite readback signal into a first readback signal corresponding to the first servo burst and a second readback signal corresponding to the second servo burst;
• an envelope detector for providing a first amplitude signal corresponding to an amplitude of the first readback signal, and for providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• a comparator for comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• a servo control system for receiving the error signal and generating a drive signal;
• and,
• a positioner assembly, coupled to the read/write head, for adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A method of positioning a read/write head with respect to a track on a magnetic disc medium, wherein the disc medium includes a servo burst pattern having (i) a first servo burst disposed on the track, characterized by a first frequency, such that the first servo burst begins near a centerline associated with the track and extends in a first direction perpendicular to the centerline towards a first track edge, and (ii) a second servo burst disposed on the track, characterized by a second frequency, such that the second servo burst begins near the centerline and extends in a second direction perpendicular to the centerline towards a second track edge, comprising:

• receiving a composite readback signal from the read/write head and separating the composite readback signal into a first readback signal corresponding to the first servo burst and a second readback signal corresponding to the second servo burst;
• providing a first amplitude signal corresponding to an amplitude of the first readback signal, and providing a second amplitude signal corresponding to an amplitude of the second readback signal;
• comparing the first amplitude signal to the second amplitude signal, and for providing an error signal corresponding to a difference between the first amplitude signal and the second amplitude signal;
• receiving the error signal and generating a drive signal therefrom;
• and,
• adjusting the position of the read/write head with respect to the track, as a function of the drive signal.

A method of arranging a servo burst pattern for use in positioning a read/write head with respect to a track on a magnetic disc medium by comparing the respective amplitudes of the readback signals of a plurality of servo bursts, comprising:

• disposing on a track having a centerline a first servo burst, characterized by a first frequency, such that the first servo burst extends along an axis in a first direction transverse to the centerline;
• disposing on the track a second servo burst, characterized by a second frequency different from said first frequency, such that the second servo burst extends along said axis in a second direction transverse to the centerline;
• and
• disposing on the track or on an adjacent track a third servo burst, characterized by a third frequency different from said first frequency and said second frequency, such that the third servo burst extends in a direction transverse to the centerline.