A head-positioning system using buried servos

Abstract

Current head-positioning servo methods require a spatial separation between the data and servo. This separation limits the accuracy with which a head-positioning servo system can follow a data track. The buried servo techniques described here allow servo information to be recorded in the same medium area as that used for data, a single head is used for both data and servo. These techniques provide high-bandwidth continuous head-position information with a potential for a high track-density servo system. The servo pattern consists of two single-frequency signals recorded deeply into the magnetic medium below the area used for data. The servo signals are detected by synchronous detection techniques and provide a continuous head-position error signal. The servo system uses this head-position error signal to follow a given data track and to seek new data tracks. Buried servo was implemented on a flexible disk drive. The track-following system had performance advantages when compared to a sector servo scheme implemented on a similar device.