Patent ID: 6590729
Filing Date: 2003-07-08
Classification: B82Y,G11B

Abstract:
A magnetic disk drive comprising:a magnetic recording medium having a servo pattern; a magnetic head that writes information on and reads the information from the magnetic recording medium; and a servo signal decoder circuit that decodes a positional signal of the magnetic head from a reproduced signal of the servo pattern, wherein the reproduced signal of the servo pattern is sinusoidal, wherein said servo signal decoder circuit comprises: an A/D converter which converts the reproduced signal from analog to digital, means for sampling a signal from said A/D converter, at a sampling frequency which is determined based on the waveform of the signal to be sampled, and means for calculating a Fourier coefficient of the sampled signal, wherein said servo signal decoder circuit decodes the amplitude and phase of the positional signal based on the Fourier coefficient of the sampled signal, wherein said servo pattern includes a plurality of patterns arranged on both sides of a center line of each of plural tracks, wherein patterns on one side of the center line are shifted in a track direction from patterns on the other side of the center line, wherein each of the plurality of patterns includes a plurality of phase patterns arranged in a track-width direction, wherein the number of types of the phase patterns is N (where N is a positive number of at least 2, and wherein patterns on one side of the center line have the same frequency and patterns on the other side of the center line have the same frequency which has a phase different from a phase of the frequency of the patterns on the one side of the center line.