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Technique for Detecting Group Coded Digital Information

IP.com Disclosure Number: IPCOM000051190D
Original Publication Date: 1982-Aug-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Graves, DC: AUTHOR

Abstract

An equalized channel system is described through which group-coded binary sequences are passed and recovered as analog waveforms with the equalized waveform information sampled on the peaks. In such systems, the amplitude and time of occurrence of individual peaks vary, due to bandwidth limitations of the channel, according to the input group coded sequence. To optimally detect analog waveform peaks, the decision threshold AND/OR sample time should be varied according to the input group-coded binary sequence, and the expected response of the channel to that sequence.

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Technique for Detecting Group Coded Digital Information

An equalized channel system is described through which group-coded binary sequences are passed and recovered as analog waveforms with the equalized waveform information sampled on the peaks. In such systems, the amplitude and time of occurrence of individual peaks vary, due to bandwidth limitations of the channel, according to the input group coded sequence. To optimally detect analog waveform peaks, the decision threshold AND/OR sample time should be varied according to the input group-coded binary sequence, and the expected response of the channel to that sequence.

Since the input sequence is not known at the time of detection, the threshold should be adjusted according to the following limitations: (a) Input coding rules, i.e., a limitation on runs of ones or

peaks and a limitation on runs of zeros, or no peaks.

(b) The expected channel response (bandwidth per phase).

(c) The binary sequence detected thus far.

A set of "adjustment" rules relating to a given recovered binary sequence and the optimum threshold to detect the next peak can be derived from the above limitations. A nominal threshold can be established by averaging the time and amplitude of many peaks. The "adjustment rules" are then used to determine a slight adjustment (DT in the figure) to this nominal threshold to compensate for data sequence related variations.

The sign and magnitude of the adjustment DT is dependent upon the sequence recovered thu...