Cselt-centro Studi E Laboratori Telecomunicazioni S.p.a.

Sip - Societa Italiana Per L-esercizio Delle Telecomunicazioni P.a.

S.i.p. Societa' Italiana Per L'esercizio Telefonico P.a.

Renato Ambrosio

Carlo M Bruno

Adler Tofanelli

Alfredo Fausone

Alberto Brosio

Giorgio Paschetta

The digital phase-locked loop circuit extracts the clock signal from a serial flow of coded data by operating so as to determine the phase of the received signal and comparing this phase with that of a locally-generated signal. The error signal obtained from the comparison is digitally filtered and used to correct the phase of local signal. The error with respect to the signal extracted from a prior data stream is stored and used to effect corrections even in the absence of the data flow at the input or in presence of long zero sequences.

Digital phase-locked loop circuits with storage of clock error signal

The echo canceller for bidirectional digital transmission systems cancels the echo queues of a desired number N of digital symbols, transmitted on the line in the last N signalling periods. It consists of a part which effects very simply the summation of the last N transmitted symbols, so as to ease the system implementation by an integrated circuit, and of a part which computes the estimated sample of the echo-channel pulse response. The results of the two parts are multiplied by one another and the estimated echo signal is obtained.

Echo canceller for bidirectional digital transmission

A bidirectional digital transmission system with echo-cancellation allows the measurement of the received data signal and the automatic adaptation of the attenuator and of the line equalizer. They are implemented by using circuits already present in a conventional system, in addition to auxiliary circuits.

Bidirectional digital transmission system with echo-cancellation

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San Raffaele Cimena, Italy

Renato Ambrosio