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Analog Maximum Likelihood Detection for the Magnetic Recording Channel

IP.com Disclosure Number: IPCOM000062339D
Original Publication Date: 1986-Nov-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Eggenberger, J: AUTHOR [+2]

Abstract

This invention relates to an analog detector in which sample and hold circuits usually associated therewith are avoided by circulating a time-varying waveform in a tapped delay line and sampling over the waveform as a whole (i.e., in parallel). In a maximum likelihood detection of pseudo-ternary transition-encoded waveforms, it has been observed that a sample corresponds to a data ONE if and only if (1) the sample is confirmed as a ONE by a subsequent sample having an adequate amplitude difference, and (2) none of the intervening samples between the sample in question and the confirming sample represent a more likely ONE than the sample in question. To formalize this description, let the amplitude of the kth sample be S(k) and the nominal sample amplitude be A.

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Analog Maximum Likelihood Detection for the Magnetic Recording Channel

This invention relates to an analog detector in which sample and hold circuits usually associated therewith are avoided by circulating a time-varying waveform in a tapped delay line and sampling over the waveform as a whole (i.e., in parallel). In a maximum likelihood detection of pseudo-ternary transition- encoded waveforms, it has been observed that a sample corresponds to a data ONE if and only if (1) the sample is confirmed as a ONE by a subsequent sample having an adequate amplitude difference, and (2) none of the intervening samples between the sample in question and the confirming sample represent a more likely ONE than the sample in question. To formalize this description, let the amplitude of the kth sample be S(k) and the nominal sample amplitude be A. Thus, if a positive ONE is being sought, sample S(n) corresponds to a ONE if and only if:

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The maximum run length of ZEROs in the data limits the number of terms which must be considered. Similarly, if a negative ONE is being sought, the nth sample corresponds to a ONE if and only if:

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To implement the foregoing, let the signal be input to a k section terminated delay line in which the delay per section is equal to the sampling period. Let S(0) be the signal amplitude at the termination end of the line, S(1) the signal amplitude at the tap nearest the termination end of the line, S(2) the signal amplitude...