Patent ID: 7009792

Claim:
A disk drive for perpendicular magnetic recording, comprising: a head which reads out a data signal recorded in a disk medium; and a read channel which includes a signal processing unit having lower cut-off frequency characteristics and including a high-pass filter which carries out removal of low-frequency noise of the data signal outputted from the head and a decoding unit which decodes recording data from the data signal, wherein the read channel includes: an extracting unit which extracts a component of a shift in a base line of the data signal processed by the signal processing unit, and a compensating unit which removes the component of the shift in the base line from the data signal, and wherein the extracting unit has: a generator which generates an ideal data signal; a subtracting unit which outputs a difference data signal according to difference between the ideal data signal and a data signal processed by the signal processing unit; and an adjusting unit including a gain adjusting circuit and a high-frequency cut-off filter, which process the difference data signal, the adjusting unit generating a signal corresponding to the component of the shift in the base line.