| 摘要 |
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 SIGMA(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.
|
