Magnetic disk apparatus and optimum offset measuring method
AssigneeFujitsu Limited
InventorKeiji Shimatani
Life of this patent
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Abstract
A magnetic disk apparatus has a measuring pattern writing unit and an optimum offset measuring unit. The measuring pattern writing unit writes random patterns to adjacent tracks on both sides of a measuring track and, thereafter, writes a preamble pattern in which PR4 equalizing characteristics are normally obtained even if simple low pass filter characteristics have initially been set. The optimum offset measuring unit obtains a mean square error per sample obtained by dividing the sum Σ(y−W)2 of the squares of differences between sampling values y which were PR4 equalized and a predetermined ideal sampling value W in which there is no noise by the number of samples (N) while changing an offset amount, and determines an offset in which the mean square error is the minimum as an optimum offset.
Claims20
A magnetic disk apparatus which has combination heads formed by arranging read heads and write heads at an edge of an actuator in a track direction and in which information is recorded or reproduced while the head is positioned to a target track so as to enter an on-track state on the basis of a position signal of a medium demodulated from a reproduction signal of said read head, further upon reproduction, the reproduction signal from said read head is equalized to a Partial Response waveform, and after that, it is maximum likelihood detected, thereby demodulating information, comprising:
- a measurement pattern writing unit for writing random patterns to adjacent tracks locating on both sides of a measuring track whose offset is measured or writing a preamble pattern to said measuring track;
- and
- an optimum offset measuring unit for obtaining the sum of the squares of errors between sampling values of the Partial Response waveform obtained by equalizing the reproduction signal of said preamble pattern and a predetermined ideal sampling value in the case where there is no noise while changing an offset amount of said combination head, calculating a mean per sample by dividing the sum of said square errors by the number of samples, and determining an offset amount in which said mean becomes the minimum for a change in said offset amount as an optimum offset.
An offset measuring method of a magnetic disk apparatus which has combination heads formed by arranging read heads and write heads at an edge of an actuator and in which information is recorded or reproduced while the head is positioned to a target track so as to enter an on-track state on the basis of a position signal of a medium demodulated from a reproduction signal of said read head, further upon reproduction, the reproduction signal from said read head is equalized to a Partial Response waveform, and after that, it is maximum likelihood detected, thereby demodulating information, comprising:
- a measurement pattern writing step of writing random patterns to adjacent tracks locating on both sides of a measuring track whose offset is measured or writing a preamble pattern to said measuring track;
- and
- an optimum offset measuring step of obtaining the sum of the squares of errors between sampling values of the Partial Response waveform obtained by equalizing the reproduction signal of said preamble pattern and a predetermined ideal sampling value in the case where there is no noise while changing an offset amount of said combination head, calculating a mean per sample by dividing the sum of said square errors by the number of samples, and determining an offset amount in which said mean becomes the minimum for a change in said offset amount as an optimum offset.
Dependencies are inferred from the claim text.