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Analog Servo Pattern for Rotating Head Tape Systems

IP.com Disclosure Number: IPCOM000081529D
Original Publication Date: 1974-Jun-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Wong, KY: AUTHOR

Abstract

A servo pattern consisting of recorded areas A1,B1,A2, B2 is used in a helical tape drive system to enable detection of skew angle error. As the tape 12 is being moved in the longitudinal direction in the rotating head mandrel, a pair of axially aligned magnetic heads carrying pulsating write currents, and turning on and off at appropriate time intervals, can write patterns such as A1, and B1.

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Analog Servo Pattern for Rotating Head Tape Systems

A servo pattern consisting of recorded areas A1,B1,A2, B2 is used in a helical tape drive system to enable detection of skew angle error. As the tape 12 is being moved in the longitudinal direction in the rotating head mandrel, a pair of axially aligned magnetic heads carrying pulsating write currents, and turning on and off at appropriate time intervals, can write patterns such as A1, and B1.

When the rotating head goes over the servo patterns A1, and B1, two envelopes of patterns are observed, and each envelope is rectified and integrated. The difference of the rectified outputs gives the off-track error, while the sum of the rectified outputs forms the AGC signal. Therefore, any change in tapetohead spacing does not affect the track error reading.

One feature is that the skew angle can be determined by use of servo patterns at both edges of the tape. The distance X1 is small compared to the track width W. By use of arrays of inclined heads, redundant readings may be obtained to protect against dropouts.

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