Servo track writing measurement of gapped initial clock track to

Details Servo track writing measurement of gapped initial clock track to Servo track writing measurement of gapped initial clock track to

1995-11-21

1998-08-18

Psitos, Aristotelis M.

Dynamic magnetic information storage or retrieval

Automatic control of a recorder mechanism

Controlling the head

360 7708, G11B 2014, G11B 5012

Patent

active

057965412

ABSTRACT:
An apparatus for servo track writing on a magnetic medium comprises a clock head (12) and a regular head (14). The regular head (14) writes an initial approximation of the clock track so as to leave a small gap between the last written pulse of the clock track and the first pulse of the clock track. Then this gap is measured by gap measurement system (33) and the frequency of clock track is updated using a direct digital synthesis system (35) so as to fill a full clock track during the next writing. The initial clock track is read by regular head (14) and its output signal is supplied to a phase locked loop. The output of the phase locked loop drives a direct digital synthesis system (35), which generates a modified frequency on its output. A signal of this frequency, in turn, is supplied to the clock head (12), which writes a new improved clock track on the disk. The resulting clock track closure is determined by instability of disk rotational speed at the gap interval and can be made less than 1 ns after five disk revolutions.

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HP 5372A Frequency And Time Interval Analyzer Operating Manual, pp. 1-1 to 1-55 (Hewlett Packard Co., Palo Alto, CA 1989).

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