Abstract: A phase noise correction circuit for a synchronous data transmission system using symbols and including a decision circuit (33) at its receiving end for supplying an estimate of the transmitted symbols on the basis of the received symbols, wherein said correction circuit comprises a phase shifter circuit (36) located at the receiving end ahead of the decision circuit (33) and provided with a third-order phase-controlling feedback circuit (37) comprising:a phase shift angle generator (62) having an incrementation input and providing the phase shifter circuit (36) with the value of a phase shift angle updated at the rate at which the symbols are received,a phase error detector (60) providing the value of the phase error between the received and the estimated symbols appearing at the terminals of the decision symbols, likewise at the rate at which the symbols are received; anda filter (61) interposed between the output of the phase error detector (60) and the incrementation input of the phase shift angle generat

Abstract: Data in the form of multi-value symbols is transmitted at a symbol rate 1/.DELTA.T. At the receiver a decision circuit supplies estimates of the transmitted symbols on the basis of the received symbols. The present invention concerns compensating phase noise after equalization if any of the received symbols and before application of the received symbols to the decision circuit (38, 39). The received symbols are in complex form with in-phase and quadrature components y.sub.k ' and y.sub.k " respectively. Phase noise is compensated by complex multiplication in a multiplier (36) of the received symbols by a complex coefficient.The invention is particularly applicable to quadrature modulation systems, but if only one channel is transmitted the quadrature channel can be simulated using the Hilbert transform of the one channel.

Abstract: Data in the form of multi-value symbols is transmitted at a symbol rate 1/.DELTA.T. At the receiver a decision circuit supplies estimates of the transmitted symbols on the basis of the received symbols. The present invention concerns compensating phase noise after equalization, if any, of the received symbols and before application of the received symbols to the decision circuit (38, 39). The received symbols are in complex form with in-phase and quadrature components y.sub.k ' and y.sub.k " respectively. Phase noise is compensated by complex multiplication in a multiplier (36) of the received symbols by a complex coefficient m.sub.km.sub.k+1 =[m.sub.k -.lambda.(v.sub.k -a.sub.k)y.sub.k *]exp[-iF.sub.k (.epsilon..sub.j)]where:.lambda. is a real coefficient;y.sub.k * is the complex conjugate of the symbol received at instant k.DELTA.T+t.sub.o (where t.sub.o is the instant taken as the origin of time measurements);v.sub.k is the symbol applied to the decision circuit at said instant;a.sub.

Abstract: Disclosed is a phase-locked loop which comprises a voltage controlled variable frequency oscillator (1), a phase comparator (2) having a cosine characteristic and receiving a reference oscillation as well as that supplied by the oscillator (1), and a low-pass filter (3) connected between the output of the phase comparator (2) and a frequency control input of the oscillator (1).The transfer function of the low-pass filter (3) is switchable between two characteristics depending on the instantaneous phase difference between the reference oscillation and that supplied by the oscillator. The first low-pass filter transfer function is adapted to the phase-locked operation of the loop, while the second transfer function is adapted for frequency capture.

Abstract: The invention relates to terminal equipment for a carrier current multiplex system with a half echo-suppressor and a channel modem. The attenuator which is inserted in the transmission chain is disposed after a first modulation stage, thereby taking advantage of the propagation time of the filters of the modem to reduce the apparent reaction of the attenuator.

Abstract: A device for suppressing a pilot wave in a spectrum of frequencies by subtraction of an auxiliary frequency adjusted in frequency, in phase, and in amplitude to adequate values, used in frequency multiplex telephone transmission systems, containing two pilot frequencies in cases where maintaining either one or several of these frequencies would lead to disturbances.