Telecommunications Radioelectriques Et Telephoniques T.r.t.

Jean-Louis Renaudat

Loic B Guidoux

A resynchronization arrangement for a data receiver having an auto-adaptive equalizer and a demodulator which utilizes a local carrier phaselocked on the received carrier by means of a control loop comprising an integrating circuit. Starting from a signal indicating a synchronization loss the arrangement generates three command pulses: a first pulse makes the adjustable coefficients of the equalizer and the signal in the memory of the integrating circuit equal to zero; a second pulse is used for making a reduced number of coefficients of the equalizer operative immediately after the first pulse and for reducing the time constant of the integrating circuit; a third pulse is used to make the synchronization loss indication signal equal to zero a given period of time after the end of the second pulse. Resynchronization is obtained without the necessity of a return connection to the transmitter.

Arrangement for the automatic resynchronization of a data transmission

Phase discriminator in a receiver of a system for data transmission by means of phase modulation of a carrier. The phase discriminator comprises a calculating unit arranged for receiving digital signals, whose associated signal samples occur at a rate equal to the data modulation rate, the digital signals being representative of the inphase and quadrature components of the received passband signals at each sampling instant and of the inphase and quadrature components of a reference carrier at a preceding sampling instant. This calculating unit calculates the signal samples of digital signals which are representative of the in-phase and quadrature components of a signal which is derived from the received passband signal by a phase shift over an angle which is equal and opposite to the phase of the reference carrier at the preceding sampling instant. The digital signals supplied by the calculating unit are applied to a decision circuit which at each sampling instant determines the phase variation of the transmitted carrier during one sampling period and reproduces the corresponding phase jump. In case the reference carrier is locally generated, the decision circuit also supplies an error signal for locking the phase of the local reference carrier on the received carrier.

Phase discriminator in a receiver for a data transmission system

A receiver of a system for data transmission by means of p-phase modulation comprises a digital phase discriminator with a calculating unit which calculates in a first interval of each sampling period the in-phase and quadrature components of a signal derived from a passband signal at sampling instant jT by a phase rotation over an angle equal and opposite to the phase of a reference carrier at instant (j-1)T. A simple derangement detector is obtained by means of a sign detector for a component supplied by the calculating unit during a second interval of each sampling period, the phase of the reference carrier then having been subjected to a phase rotation equal to the phase variation of the transmitted carrier, and by means of a calculated circuit which calculates the quantity .vertline.x.sub.3 .vertline.-kx.sub.3, where k&lt;tan (.pi./p) and x.sub.3, x.sub.3 are the in-phase and quadrature components supplied by the calculating unit during a third interval of each sampling period, the phase of the reference carrier then having been subjected to an additional phase rotation equal to +(.pi./p) or -(.pi./p) depending on the sign determined by the sign detector. Alarm pulses are supplied at a negative sign of the quantity calculated by the calculating circuit.

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Le'Plessis-Robinson, France

Jean-Louis Renaudat