Servo field scheme for high sampling rate and reduced overhead embedded servo systems in disk drives

摘要

In an embedded servo system for a disk drive, prerecorded servo information in each track of the disk includes a multiplicity of different length servo fields. Each track includes at least two types of servo fields where the first type and the second type have different lengths. The length of a servo field refers to the number of prerecorded bytes in the servo field. The multiplicity of different length servo fields includes a first type having a full track address sub-field and a second type having a modulo track address sub-field in place of the full track address sub-field. One embodiment includes the first and second types of servo fields and a third type of servo field. The third type of servo field includes only track following information and no track address information. The servo fields of differing lengths are interleaved in each track of the disk. The servo fields are chosen to provide a high seek sampling rate in comparison to the required performance and a reduction in the servo overhead. Increased track following sampling is provided to make the read/write head less likely to move off track in response to external forces on the disk drive. Disk drives with different types of servo fields interleaved are particularly well-suited for small portable computers.