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Disk File Phase-Encoded Sector Servo Pattern With Data and Reference Fields in Each Sector

IP.com Disclosure Number: IPCOM000038515D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31
Document File: 3 page(s) / 66K

Publishing Venue

IBM

Related People

Jones, DM: AUTHOR

Abstract

In certain magnetic recording disk files, servo information for maintaining the read/write head over the data tracks and moving it between the tracks is located on the data disk in sectors interspersed among the data and equally angularly spaced around the data disk. One method of providing data track position information in the servo sectors is to write a constant frequency pattern with phase shifts of the frequency pattern between the tracks, as described in U.S. Patents 4,549,232 and 4,511,938. Head position information is thus encoded in the phase of the servo pattern and is used to generate a head position error signal (PES).

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Disk File Phase-Encoded Sector Servo Pattern With Data and Reference Fields in Each Sector

In certain magnetic recording disk files, servo information for maintaining the read/write head over the data tracks and moving it between the tracks is located on the data disk in sectors interspersed among the data and equally angularly spaced around the data disk. One method of providing data track position information in the servo sectors is to write a constant frequency pattern with phase shifts of the frequency pattern between the tracks, as described in U.S. Patents 4,549,232 and 4,511,938. Head position information is thus encoded in the phase of the servo pattern and is used to generate a head position error signal (PES). An improved phase-encoded servo pattern for use with sector servo is achieved by providing in each sector a specific "servo data" field and a "servo reference" field which together provide disk file information, servo error correction and gain control of the PES. As shown in Fig. 1, a typical servo sector is shown interspersed between user data on a data track, and comprises a servo data field, a reference field, and the phase-encoded position field. The servo data field may contain various information which is application dependent, for example, head address or partial cylinder address. The reference field provides
(a) information to generate an automatic gain control

(Image Omitted)

for the amplitude of the subsequently read position information from the position field, and (b) phase information to generate an error correction for the phase of the subsequently read position information. The phase-encoded position information provides a quadrature pattern, as represented in Fig. 2. The position information in the position field is written in a phase-encoded format and provides both a normal (N) and a quadrature (Q) output when demodulated by appropriate demodulation circuitry. In the pattern depicted in Fig. 2, there are eight track types with each track shifted 45OE from adjacent tracks. The position infor...