Browse Prior Art Database

Magnetically Derived Servo Information

IP.com Disclosure Number: IPCOM000098285D
Original Publication Date: 1960-Jul-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Bacon, GC: AUTHOR [+2]

Abstract

The system locates a recording head at a desired track center. Concentric rings of alternating vertical magnetization are recorded on a disk. A flux sensitive head senses the position radially along the rings.

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Magnetically Derived Servo Information

The system locates a recording head at a desired track center. Concentric rings of alternating vertical magnetization are recorded on a disk. A flux sensitive head senses the position radially along the rings.

Coil A is driven by an A.C. source of frequency omega. If the current is of the proper amplitude, the magnetic flux in the head varies at a rate of 2 omega, thus inducing a voltage of the same frequency in Coil B. To eliminate the basic frequency omega, also present, a band pass filter permits only the 2 omega frequency to be applied to a phase detector and demodulator. When the poles of the head are positioned so that they couple to bands of the same magnetic polarity, the 2 omega frequency output due to track coupling is at a minimum. Displacement of the head in either direction produces an output of the 2 omega frequency, the phase of which depends upon the direction of displacement. This signal, after passing through the phase detector and demodulator, is used to control a servo motor to position the head exactly on the desired track.

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