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Track Following Servo Indicator

IP.com Disclosure Number: IPCOM000081929D
Original Publication Date: 1974-Sep-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Fiorino, BC: AUTHOR

Abstract

In helical scan recorders, a servo track brackets the data recording area commonly referred to as helical scan tracks. In one preferred form, the rotating head of such a recorder scans a servo signal characterized in a frequency domain. A burst of servo data signals is characterized by a leading and trailing band of a first frequency signal, separated by a center frequency indicator having one or more long wavelengths equal to about one-half of the first frequency.

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Track Following Servo Indicator

In helical scan recorders, a servo track brackets the data recording area commonly referred to as helical scan tracks. In one preferred form, the rotating head of such a recorder scans a servo signal characterized in a frequency domain. A burst of servo data signals is characterized by a leading and trailing band of a first frequency signal, separated by a center frequency indicator having one or more long wavelengths equal to about one-half of the first frequency.

A suitable transducer scans the servo track and supplies the readback signal through a narrow-band filter. Frequency summer limiter and burst detector indicate that servo signals are being read. The same signal is supplied through a wide-band filter limited and wavelength detected for finding the center indicator, and AND circuit A is jointly responsive to the servo envelope indication and to the wavelength detection to supply a center signal.

Track offset, i.e., the relationship of the scan path of the rotating head and the actual track center of the recorded track, not shown, is indicated by the elapsed time of the leading first frequency signal, or a similar elapsed time between the center indicator and the trailing first frequency signal. Suitable timing generators, not shown, can meter the time indicated as the offset indicator in the alternative cycles in the leading first frequency signal portion to provide account of the elapse time, indicating the skew relations...