DISK DRIVE HAVING HEAD POSITIONING SERVO WITH IMPROVED SERVO READ SIGNAL PROCESSING USING MEDIAN SERVO BURST PEAK MAGNITUDES

A disk drive for use with an embedded head positioning servo system is disclosed. The disk drive includes a disk on the surface of which spaced-apart servo bursts are prerecorded in servo sectors. Successive servo bursts are read by a read/write head which produces oscillating signals having variable magnitude peaks. A timing circuit provides a timing signal, synchronized with the occurrence of the servo sectors, which defines, in time, a servo signal window, during which time a servo burst is being read by the read/write head. A detector circuit measures the magnitudes of each of the peak signals of a servo burst occurring in the servo timing window. The median peak value for a burst is stored, a next burst is detected and measured and the median peak value for that burst is stored. By comparing the median peak magnitudes of successive servo bursts, a servo error signal for use in correcting any error in head position relative to a desired track centerline is produced. The servo error signal is applied to an electrically controlled actuator which moves the read/write head.