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Data Detector with Reliability Enhancement Feature

IP.com Disclosure Number: IPCOM000082212D
Original Publication Date: 1974-Oct-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 43K

Publishing Venue

IBM

Related People

Beaulieu, TJ: AUTHOR [+4]

Abstract

A data detector consists of an exclusive 0R gate 10, which receives a hard-limited equalizer output (NRZI Signal) A and that signal delayed by a prescribed amount Tau , waveform B. Typically, Tau is one-half bit cell time. The leading edges of the resulting output pulses C correspond to the transitions or "1's" in the original input signal. The duration of these pulses always equals to the time delay Tau.

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Data Detector with Reliability Enhancement Feature

A data detector consists of an exclusive 0R gate 10, which receives a hard- limited equalizer output (NRZI Signal) A and that signal delayed by a prescribed amount Tau , waveform B. Typically, Tau is one-half bit cell time. The leading edges of the resulting output pulses C correspond to the transitions or "1's" in the original input signal. The duration of these pulses always equals to the time delay Tau.

In contrast to this, the pulses caused by "droop" in a long string of "0's" or random noise are characterized by pulse widths, which are almost always significantly less than one-half bit cell time or the time delay Tau.

An enhancement circuit consists of a logic (or analog) network that eliminates the pulses, whose width is some Triangle amount (4 ns in this example) less than the delay time Tau of the data detector.

Fig. 1a illustrates a basic detector which provides RZ pulses C, whose leading edges correspond to transitions in the hard-limited equalizer output. Output C is shown, which includes noise pulses that are level-shifted and fed into a variable-frequency oscillator (VFO). The noise-derived pulses (shaded areas of waveform C) would produce errors, since the VFO could not distinguish these pulses from data.

The enhancement circuit, shown in Fig. 1b provides a means of eliminating pulses whose width is too narrow. For purposes of example, each gate delay is assumed to be 2 ns.

The output of the basic detector, waveform C, is sent to the enhancement circuit, shown in Fig. 1b. With the assumed gate delay of 2 ns each, this network will not provide output pulses (waveform H of Fig. 3) unless...