France Telecom

Compagnie Gervais Danone

Patrick Vandamme

Francis Lovell

Joel Labat

Dominique Leroux

Joelle Kervarec

Frédéric Bourdin

Alain Leclert

A coherent demodulating device is characterized by a demodulating circuit and a carrier recovering circuit produced entirely in digital form. Two quadrature demodulation carrier waves produced by a local oscillator are mixed with a demodulation carrier signal modulated by symbols to produce analog signals. The analog signals are digitized by sampling at symbol reception frequency into incoming digital signals. A digital phase shifter phase shifts the incoming signals by a demodulation phase derived by a phase loop digital processing circuit as from error signal pulses supplied by a comparing circuit receiving outgoing digital signals from the phase shifter. The compensation for the phase and frequency differences between the demodulation and modulation carrier waves is carried out a posteriori in digital form by phase shifting the incoming signals.

Coherent demodulating device with carrier wave recovering digital circuit

The invention concerns a device for recovering a carrier wave provided with a circuit for inhibiting dummy frequency hookings or acquisitions for phase-modulated digital signals in N states with a phase N=2P, device including a phase locking loop provided with demodulation, a voltage-controllable oscillator, a 90.degree. phase shifter, for the low-pass filtering of basic band signals X1(t) and Y1(t), a loop filter, for sampling the signals X1(t) and Y1(t) and having a sampling frequency Fe so that Fe&gt;(2p+1.vertline.n.vertline.)/T where T is the reciprocal value of the modulation speed and, associated with this loop, a circuit for drawing up the filtered signals Sign Sin (2P .PHI.k) and Sign Cos (2P .PHI.k) required for detection of the direction of variation of the phase error, a phase/frequency comparator, loss of synchronization and hooking detection and an adaptive filter.

Device for recovering a carrier wave provided with a circuit for

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Perros Guirec, France

Patrick Vandamme