Alcatel Telspace

Mani Kimiavi

Alain Fargues

Juing Fang

A process of determining the Eb/No ratio of a digital transmission is applied to a signal having a plurality of phases made up of two data streams in phase quadrature providing in each symbol time a received sample whose position in the constellation is defined by its coordinates obtained by quantizing the data streams. This process determines the number of erroneous samples received during a given time period whose coordinates correspond to those of indicative samples, the coordinates of the indicative samples being different from those of optimal samples received under optimal transmission conditions. The process then calculates the ratio between the number of erroneous samples and the total number of samples received in this time period, the calculated ratio being inversely proportional to the Eb/No ratio.

Process and device for detecting loss of carrier recovery and of

A branch synchronization device for multidimensional trellis coded digital data receivers using convolutional encoders includes a Viterbi decoder receiving two streams of symbols and supplying coded sequences and a time shifter for time shifting the symbol streams fed to the Viterbi decoder. The time shifter is controlled by a branch synchronization decision device generating a time shift control signal. The branch synchronization decision device cooperates with a calculator circuit receiving the coded sequences and supplying to the synchronization decision device an output signal of a first type if the coded sequences correspond to sequences such as would be obtained directly from the convolutional encoder and supplying an output signal of a second type if the coded sequences do not correspond to sequences that could have been obtained from the convolutional encoder. This output signal is fed to the branch synchronization device.

Device for synchronizing branches of a Viterbi decoder included in a

A method of controlling a digital carrier recovery apparatus designed to be integrated in a demodulation stage of a receiver for receiving a digital signal. The demodulation stage includes a carrier recovery detection apparatus. The carrier recovery detection apparatus includes a loop filter including a summing circuit followed by a bistable circuit operating in time with the symbol time, and a switching device disposed between the summing circuit and the bistable circuit. The switching device is driven to alternately apply to the bistable circuit a control word, whose variation between two successive applications to the bistable circuit is less than the acquisition band of the carrier recovery apparatus, and the output signal of the summing circuit. By alternately applying the control word and the output signal, the acquisition band is displaced relative to the tracking range of the carrier recovery apparatus.

Digital apparatus for broadband carrier-recovery

A device for synchronizing the phase of each packet of a phase modulated digital signal comprises a correction module controlled by information supplied successively by two separate calculator circuits. The phase synchronization device can be integrated into the demodulator stage of a receiver for digital signals phase modulated with at least two phase states, this signal being transmitted by successive packets. The device comprises a corrector module for rotating the constellation of phase states of the received signal according to an indication representative of the angular offset of this constellation. For each received packet to be synchronized in phase, the angular offset indication controlling the corrector module is supplied initially, for a predetermined time, by a first calculator circuit implementing the Viterbi algorithm (first indication) and thereafter, after a switching time corresponding to the end of the predetermined time, by a second calculator circuit constituted by a phase-locked loop (second indication), the second calculator circuit being initialized with the first angular offset indication at the switching time. The device enables fast phase synchronization with good noise immunity.

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Paris, France

Mani Kimiavi