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Bipolar Repeaters

IP.com Disclosure Number: IPCOM000090645D
Original Publication Date: 1969-Jun-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Croisier, A: AUTHOR

Abstract

Repeaters are used in transmission networks to compensate for line attenuation and distortion. When using PCM transmission type, positive as well as negative pulses are transmitted. Therefore, repeaters must use a detection threshold at position and negative levels. A level one half of the signal peak is often used. For the purpose of setting the detection threshold, the signal is full-wave rectified and a peak detector is used. This peak detector is required to hold the threshold level at a relatively constant voltage level even when long sequences of zeros are transmitted. In order to minimize noise influence, the peak detector can be replaced by a sample and hold.

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Bipolar Repeaters

Repeaters are used in transmission networks to compensate for line attenuation and distortion. When using PCM transmission type, positive as well as negative pulses are transmitted. Therefore, repeaters must use a detection threshold at position and negative levels. A level one half of the signal peak is often used. For the purpose of setting the detection threshold, the signal is full- wave rectified and a peak detector is used. This peak detector is required to hold the threshold level at a relatively constant voltage level even when long sequences of zeros are transmitted. In order to minimize noise influence, the peak detector can be replaced by a sample and hold.

In the event of superposition of noise to the signal, peak detection if far from ideal. If a noise pulse is added to the signal pulse, the peak detector loads to the sum of both, thus upsetting the threshold and lowering the noise rejection efficiency of the repeater. This phenomenon can cause a 3.5 dB loss in the practical signal-to-noise ratio.

A solution to this problem is to replace the peak detector, or combine it, with a sample and hold circuit. The advantage of this circuit is that a threshold displacement, due to noise, is not transferred from one bit to the next. Both positive and negative noise amplitudes are taken into account and, on the average, cancel each other.

The sample and hold circuit is gated at the pulse train peak times only. This circuit has therefore to be...