Patent ID: 6975469

Claim:
A disk drive having a perpendicular magnetic recording system and a head that performs read and write operations in accordance with the perpendicular magnetic recording system, said disk drive comprising: a disk medium including a magnetized area corresponding to data recorded with the perpendicular magnetic recording system and the head and a servo area in which servo data encoded with DC free code is recorded, servo data being used to control a position of the head; a decoding unit configured to decode the servo data; a read channel configured to conduct signal processing of a read signal read with said head from said servo area of said disk medium; wherein said read channel extracts the read signal whose level changes depending upon the magnetization transfer position of said magnetized area and has a predetermined low cut-off frequency fc characteristic for eliminating low frequency component of the read signal, and wherein the low cut-off frequency fc is predetermined by the relationship: T min≦(−ln N )/2π fc, where Tmin is a minimum magnetization reverse interval time of said DC free coded servo data and N is a constant based on a read error rate of servo data.