Embodiments of the invention eliminate noise from burst signals by use of
a reliable and simple method. In one embodiment, the read processor of
the HDD has a noise elimination circuit. The noise elimination circuit
retains multiple integral values of the waveform absolute values for each
period in the burst signals read out from the head, then removes a
maximum value and/or a minimum value from the multiple integral values,
and transmits the remainder as noise-eliminated signal data. The noise
elimination circuit is a circuit for eliminating noise from an N number
of periods of burst signal data, and this circuit integrates the absolute
values of the waveforms for each period in the N number of periods of
burst signal data, compares the integral values of each period with one
another, and outputs the remainder obtained by removing the maximum and
minimum integral values, to the servo data decoder of the following
stage.