Embedded servo track following system and method for writing servo tracks

Abstract

A servo track following system for positioning a moving read/write head relative to a magnetic storage disc. A plurality of servo tracks are recorded in sectors on the disc for identifying radial positions or informational tracks. The servo tracks have a nonuniform radial track density varying from more dense at the periphery of the disc to less dense at the interior, established with a method that allows the unique performance characteristics of the 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 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 a head to a limit stop and writing a reference track. Thereafter, the head is displaced an amount sufficient to reduce the amplitude of the reference track by a predetermined percentage which is related to the ultimate average track density. Thereafter, another reference track is written and the head is again stepped away from the second reference track an amount sufficient to again reduce the amplitude of the reference track by a predetermined percentage. 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 tracks are written by alternatively writing servo and reference in alternating servo and informational sectors. The reduction number is used to determine the pitch of all tracks.