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Phase Recovery Device for Data Transmission Receiver

IP.com Disclosure Number: IPCOM000091428D
Original Publication Date: 1968-Jan-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Related People

Desblache, A: AUTHOR [+2]

Abstract

In many devices for data transmission, the receiver is set on the received message or on a particular signal of this message. Very frequently, there is a problem of phase ambiguity. This device is used to solve such a problem, in particular with transmission modes in which data structure is such as if the message results from the super-position of two messages, these two messages being sent on two time orthogonal channels. Such is effected by modulation of a same carrier with a frequency shift of Pi/2 from one channel to the other.

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Phase Recovery Device for Data Transmission Receiver

In many devices for data transmission, the receiver is set on the received message or on a particular signal of this message. Very frequently, there is a problem of phase ambiguity. This device is used to solve such a problem, in particular with transmission modes in which data structure is such as if the message results from the super-position of two messages, these two messages being sent on two time orthogonal channels. Such is effected by modulation of a same carrier with a frequency shift of Pi/2 from one channel to the other.

If, for example, data A...E is sent as in waveform 2, this is as if there is sent on one channel the carrier P1, frequency F, modulated by data A, C, and E and on the other channel the carrier P2=P1 phase-shifted by Pi/2, modulated by B and D. One mathematical study shows that if a received global signal Y is modulated by carrier P1 there is obtained a signal Z = S1 x P1 + S2 x P2 where S1 = P1 modulated by A, C, and E and S2 = P2 modulated by B and D. In the receiver, P1 is recovered or formed. The signal Z is filtered through a low-pass filter LPF, the cutoff frequency Fc of which is such that F/2<Fc<F. There is obtained signal Z' the transitions of which occur always during the negative alternance of P1. The transitions occur on Z' when modification of values 0 to 1 or 1 to 0 occurs on A, C, and E.

If there is a phase shift of P1 of the clock, there results that, since P1 is obtai...