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Head Position Detection using a Standard Data Channel

IP.com Disclosure Number: IPCOM000085558D
Original Publication Date: 1976-Apr-01
Included in the Prior Art Database: 2005-Mar-02
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Schwarz, TA: AUTHOR

Abstract

The track following servo system described in the IBM Technical Disclosure Bulletin, Vol. 16, No. 7, December 1973, pages 2204 to 2208, has alternate servo tracks with transitions in quadrature relationship. The density of transitions is sufficiently high that a single sinusoidal signal is read back, whose phase indicates the magnitude and direction of displacement from the servo track boundaries. This phase difference is detected with the aid of a phase-locked oscillator which is synchronized on a portion of aligned transitions preceding the track following information.

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Head Position Detection using a Standard Data Channel

The track following servo system described in the IBM Technical Disclosure Bulletin, Vol. 16, No. 7, December 1973, pages 2204 to 2208, has alternate servo tracks with transitions in quadrature relationship. The density of transitions is sufficiently high that a single sinusoidal signal is read back, whose phase indicates the magnitude and direction of displacement from the servo track boundaries. This phase difference is detected with the aid of a phase-locked oscillator which is synchronized on a portion of aligned transitions preceding the track following information.

If such a servo pattern is employed in sectors of a data bearing surface, each of which includes radially aligned synchronizing transitions preceding the quadrature transitions, the standard data readback channel can be used to provide the position error signal (PES), thereby dispensing with the need for a separate servo channel. This is achieved by sampling and holding the voltage- controlled oscillator (VCO) error signal generated in the existing read channel phase-locked loop. During servo sectors, this signal represents the position error.

As shown in the drawing, signals from data/servo head 1 are amplified at 2, detected by detection circuits 3 and applied to a standard read channel phase- locked loop. The loop contains phase detector 4, filter and buffer amplifier 5 and VCO 6. The signal at point A represents the phase error of the inpu...