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Recording Readback Errors by Adjusting Equalization

IP.com Disclosure Number: IPCOM000088603D
Original Publication Date: 1977-Jul-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Luhrs, OR: AUTHOR [+2]

Abstract

Media defects, debris on record medium, and momentary lift-offs cause reduced amplitude of readback signal envelopes. Such reduced amplitude at the onset and trailing edge portion results in phase-shifted signals which can cause error. In a defect area, phase shift can prevent successful recovery of digital signals. By adjusting equalization during retries, the error-causing, phase-shifted signals can be recovered for assisting in error correction by providing more correct signals.

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Recording Readback Errors by Adjusting Equalization

Media defects, debris on record medium, and momentary lift-offs cause reduced amplitude of readback signal envelopes. Such reduced amplitude at the onset and trailing edge portion results in phase-shifted signals which can cause error. In a defect area, phase shift can prevent successful recovery of digital signals. By adjusting equalization during retries, the error-causing, phase-shifted signals can be recovered for assisting in error correction by providing more correct signals.

Apparatus with which the invention is practiced includes a transducer scanning a record member for supplying readback signals through an amplifier to an adaptive or feedback equalizer. The output signal of the equalizer drives a self-clocked detector, which supplies detected data signals to an error detector. The error detector supplies corrected signals to a utilization and control device. Additionally, the self-clocked detector supplies phase error indicating signals to a programmed phase error analyzer. The analyzer supplies phase error correcting signals to a digital control for the equalizer which, in turn, adjusts the equalizer in accordance with the instruction signals from the analyzer. In normal operation, the analyzer adjusts the feedback equalizer to provide idealized equalized signals to the self-clocked detector.

However, upon a persistent error which is not error correctable, the utilization and control device supplies c...