Patent ID: 6181505
Filing Date: 2001-01-30
Classification: G11B

Abstract:
A method for demodulating a read signal formed of a user data waveform and a servo waveform which are generated by a read head as the read head passes over a user data area and a servo area, respectively, on a medium in a storage device, the method comprising steps of:(a) converting the user data waveform to a series of digital user data values at a user data sample rate;(b) applying the series of digital user data values to a user data detector circuit;(c) converting the servo waveform to a series of digital servo values at a servo sample rate, which is independent from the user data sample rate, with a first analog-to-digital (A/D) converter having a sample clock input;(d) generating a servo clock signal as a function of the servo waveform with a first phase-locked loop;(e) generating a servo sample clock signal as a function of the servo clock signal and applying the servo sample clock signal to the sample clock input of the first A/D converter to operate the first A/D converter at the servo sample rate; and(f) demodulating the series of digital servo values synchronously with the servo waveform by:(i) generating a demodulating signal from the servo clock signal, wherein the demodulating signal is synchronized with a fundamental phase and frequency of the servo waveform;(ii) multiplying the series of digital servo values by the demodulating signal to produce a plurality of demodulated servo values; and(iii) accumulating the plurality of demodulated servo values to produce a position error value indicative of a position error of the read head relative to a location on the medium.