Patent ID: 8654466
Filing Date: 2014-02-18
Classification: G11B

Abstract:
1. A method of calculating a Head Media Separation (HMS) from a preamble of at least one embedded servo sector in a disk drive, the disk drive including at least one disk, comprising: reading the preamble of the at least one embedded servo sector, the read preamble being amplified by a variable gain amplifier (VGA) set at a predetermined gain; transforming samples of the at least one read preamble into a first and a second frequency using a discrete time-to-frequency domain transform; calculating a ratio of a magnitude of the discrete time-to-frequency domain transform of the first frequency to a magnitude of the discrete time-to-frequency domain transform of the second frequency; determining the HMS from the calculated ratio; and enabling the predetermined gain to be updated only at a beginning of a window of width modulo-N, wherein N is a wavelength of a lower one of the first and second frequencies.