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Triple Layer Magnetic Recording Track Following Servo Concept with Alternating Single Frequency Servo Tracks

IP.com Disclosure Number: IPCOM000080208D
Original Publication Date: 1973-Nov-01
Included in the Prior Art Database: 2005-Feb-27
Document File: 3 page(s) / 65K

Publishing Venue

IBM

Related People

Comstock, RL: AUTHOR [+2]

Abstract

This system makes possible recording of servo tracks with a single frequency of servo signals from servo track to servo track. With reference to Fig. 1, the servo concept makes use of a triple-layer disk 10, in order to assure that the servo signals have no harmonic in the data bands and to prevent erasure of the servo tracks during information recording. The servo tracks are recorded in the bottom layer 11 of the triple-layer disk where the servo tracks associated with even numbered data tracks are recorded at a frequency fs, and the servo tracks associated with odd data tracks are magnetically saturated in a given orientation.

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Triple Layer Magnetic Recording Track Following Servo Concept with Alternating Single Frequency Servo Tracks

This system makes possible recording of servo tracks with a single frequency of servo signals from servo track to servo track. With reference to Fig. 1, the servo concept makes use of a triple-layer disk 10, in order to assure that the servo signals have no harmonic in the data bands and to prevent erasure of the servo tracks during information recording. The servo tracks are recorded in the bottom layer 11 of the triple-layer disk where the servo tracks associated with even numbered data tracks are recorded at a frequency fs, and the servo tracks associated with odd data tracks are magnetically saturated in a given orientation. The magnetic saturation of the odd servo tracks allows the frequency signals recorded in the even servo tracks to be nonphase dependent upon the frequency recorded in other servo tracks, for the generation of a proper error position signal.

Fig. 1 further shows two servo heads 7 and 8 ganged together with data head
9. Servo head 7 is associated with even servo tracks and servo head 8 is associated with odd servo tracks. Therefore, when it is required to have the data head located over an even data track, then the even servo head 7 will be used whereas if the data head is to be located over an odd data track, then the odd servo head 8 would be used. The servo heads 7 and 8 are center tap magnetoresistive heads or magnetic transducers containing two adjacent gaps, such that three terminals may be received from the head for use in signal processing. Fig. 1 shows as waveform A the signal generated in the left portion of the servo element 7, as servo element 7 would be moved left or right with respect to the servo tracks. Waveform B illustrates the waveform generated in the right portion of servo head 7 during that same movement.

With reference to Fig. 2, there is shown a circuit for generating the DC position error from the signals generated in the servo transducers. Summation circuit 1 adds together the signals generated in the left and right portions of servo head 7, to generate an output waveform shown as waveform D in Fig. 1. Waveform E of Fig. 1 shows the output waveform that would result from summation 1 if the odd...