G - Physics – 11 – B
Patent
G - Physics
11
B
352/21.21
G11B 5/55 (2006.01) G11B 5/012 (2006.01) G11B 5/58 (2006.01) G11B 5/596 (2006.01)
Patent
CA 1191255
EMBEDDED SERVO TRACK FOLLOWING SYSTEM AND METHOD FOR WRITING SERVO TRACKS Abstract of the Disclosure An embedded servo track following system is disclosed for positioning a read/write head relative to a magnetic storage disc to read and write data on the disc. The system includes positioning means energizable for moving the read/write head to preselected recording positions relative to the disc and drive means for creating relative movement between the disc and the read/write head thereby enabling the transfer of data between the storage medium and the head. A plurality of servo tracks are embedded or recorded in servo data sectors on the disc for identifying preselected radial positions or informa- tional data tracks on the disc. The servo data tracks are provided with a nonuniform radial track density. The track density of the servo tracks varies from more dense at the periphery of the disc to less dense at the interior of the disc. The radial track density of the servo data tracks is established with a method of writing embedded servo data that allows the unique performance characteristics of the moving read/write head to determine the actual spacing of the tracks. A clock track is written by writing a single pulse on a fixed clock track head, phase-lock looping to an intermediate clock track, which is written on a moving read/write head, and then phase-lock looping up to the final clock track which is written on the fixed clock track head. Radial track density is then determined by moving one of the read/write heads to a limit stop and writing a reference track. Thereafter, the moving read/write head is displaced an amount sufficient to reduce the amplitude of the reference - 1 - track by a predetermined percentage which is related to the ultimate average track density. Thereafter, another reference track is written and the moving read/write head is again stepped away from the second reference track an amount sufficient to again reduce the amplitude of the reference track to a predetermined level. This is continued until the disc is filled with reference tracks. If the average track density thus achieved is unsatisfactory, the reduction number is adjusted and the process is repeated. Once the correct reduction number is determined for a predetermined average track density, the servo data tracks are written by alternatively writing servo data and reference in alternating servo data and informational data sectors disposed on the disc. The reduction number previously determined is used to determine the pitch of the reference tracks written in the informational data sectors on the disc and thus, also deter- mine the pitch of the servo data tracks written in the servo data sectors on the disc. The method for writing servo data is applicable to many different types of servo data and may be used to write a dedicated surface as well as embedded servo data. - 2 -
413636
Chan Keat-Lye
Nelson David L.
Oliver Theodore A.
Nortel Networks Limited
Turpin F.
LandOfFree
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