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Coding Technique for Magnetic Recording

IP.com Disclosure Number: IPCOM000096410D
Original Publication Date: 1963-May-01
Included in the Prior Art Database: 2005-Mar-07
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Maley, GA: AUTHOR [+2]

Abstract

Binary data can be encoded for magnetic recording by combining techniques used in non-return-to-zero (NRZ) and phase encoding, retaining the benefits of both.

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Coding Technique for Magnetic Recording

Binary data can be encoded for magnetic recording by combining techniques used in non-return-to-zero (NRZ) and phase encoding, retaining the benefits of both.

Phase encoding, the upper wave form, has at least one flux polarity shift for each binary bit period. This technique results in several advantages, including the capability of self-clocking for each channel, better signal to noise ratio, and the ability to detect signal dropout during reproduction. However, some flux shifts, such as at periods 1, 3, 7 and 11, are not significant in that only the direction of flux shift at periods 2, 4, 6, etc., are significant.

By converting the data to be recorded into a pattern of flux shifts, where the absence of a flux shift in two adjacent periods is not allowed, a NRZ pattern results where each flux shift is significant. The above-mentioned benefits of phase encoding are retained in that at least one flux shift occurs within a predetermined period.

In the table, the eight permutations of three binary data bits can be represented by five flux shifts following the restriction that the absence of a flux shift in two adjacent periods is not allowed. With phase encoding, represented by the upper wave form, two sets of three binary data bits would require twelve periods to record. By converting each of the sets of three data bits to patterns of five flux shifts in a code converter. the same six data bits can be recorded in the space o...