Abstract: The invention provides a block-encoded modulation scheme using multi-level partitioning techniques. This scheme is made transparent to phase ambiguities of ±&pgr;/2 and of &pgr;, by means of differential encoding and appropriate mapping, it is applicable to 16-QAM modulation, and it has theoretical encoding gain that is optimal for the rate of the code. The decoder associated with this scheme uses the Wagner algorithm which is much less complicated to implement than the Viterbi algorithm or than the Reed-Solomon algorithm.

Abstract: The invention relates to a system for detecting the presence of a carrier wave in a digital signal that is available at a given frequency. The system delivers at least two baseband samples of the digital signal at each symbol time. The system comprises a timing estimator responsive to the baseband samples to deliver an error signal (&egr;) corresponding to the phase error between the clock frequency that is to be recovered and a local clock frequency, and a detector that generates a detection signal indicating that a carrier wave has been detected whenever a level representative of the variance of the error signal (&egr;) reaches a threshold value. The invention is particularly applicable to receivers of signals transmitted in DTMA mode.

Abstract: 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.

Abstract: The invention relates to a method of changing the supervisor program installed in a receiver station (11) for receiving a radio beam (12) in a supervisory network, said method consisting in replacing instructions in a current supervisor program of said receiver station (11) with instructions of a new supervisor program on the basis of which said receiver station (11) is to operate, said radio beam (12) carrying at least one service path in addition to a main path. According to the invention, the method consists in conveying the instructions of the new supervisor program to said receiver station (11) via said service path. The invention also relates to a receiver station making it possible to implement such a method of changing the supervisor program.

Abstract: The invention relates to apparatus for synchronizing the phase of a digital signal constituted by two digital components to be corrected defining two samples of a received signal at each symbol time, said apparatus serving to feed a regenerator for regenerating the signal in baseband by sampling and threshold decision-taking, said apparatus including: a first phase-locked loop (31) driven by a first broadband phase-error integrator (37), said first loop (31) being fed with the input signal (30) of the apparatus, and supplying a first phase error estimate (36); and an auxiliary second phase-locked structure (32) driven by re-processing means (38) for re-processing said first phase error estimate (36) established by said first phase-locked loop (31), and outputting a phase synchronized signal fed to an output regenerator (34) for regenerating the signal in baseband; said auxiliary second phase-locked structure (32) being fed with said input signal (30) of the apparatus via delay means (35).

Abstract: The invention concerns a method of transmitting data reliably over N normal channels (3), where N.gtoreq.1, and over at least one back-up channel (4), between a transmit end station (1) and a receive end station (2), the data transmitted comprising both traffic data and supervisory data. According to the invention, the following successive steps are performed in said transmit end station (1): the traffic data and the supervisory data applied to each of the N pairs of inputs are multiplexed on a respective one of the N normal channels; then, the multiplexed data from a "backed-up" one of the N normal channels is switched to the back-up channel.

Abstract: The invention relates to a phase-locked loop delivering a recovered clock signal from a reference clock signal F.sub.ref in which some transitions are missing. The loop includes a first divide-by-M frequency divider receiving the clock F.sub.ref and delivering a signal of frequency F.sub.ref /M; a phase comparator providing a phase error signal from the signal of frequency F.sub.ref /M, and the output signal from a second divide-by-M frequency divider; a divide-by-K frequency divider providing a signal of frequency F.sub.k from a local oscillator signal of frequency F.sub.oL receiving the phase error signal as a control signal; an adder-counter of the division ratio p/q receiving the local oscillator signal of frequency F.sub.oL and delivering a signal of frequency F.sub.o equal to F.sub.oL *p/q; a mixer delivering a signal of frequency F.sub.n equal to F.sub.o -F.sub.k on the basis of signal of frequency F.sub.k and the signal of frequency F.sub.o ; and a divide-by-N frequency divider synchronized by F.sub.

Abstract: A method of modeling the AM--AM and AM-PM characteristics of an amplifier includes the step of transmitting a reference signal to the amplifier. The response of the amplifier to the reference signal is digitized to produce two sets of AM--AM and AM-PM reference samples, respectively. Two series of polynomials respectively representative of the AM--AM and the AM-PM characteristics are determined from the samples. The determination of each polynomial allows for the second derivative of the polynomial and for the distances between the samples and points on the curve defined by the polynomial.

Abstract: An equalizer-combiner for a diversity receiver using at least two receive channels computes equalization coefficients for each channel allowing for a first channel error signal representative of a comparison between the demodulated signal and a channel estimate of the transmitted source signal delivered by a channel estimator fed with the demodulated signal in the channel during an acquisition phase and a second channel error signal representative of a comparison between the demodulated signal and the global estimate of the transmitted source signal during a normal operation phase.

Abstract: A device for initializing a Viterbi decoder in a receiver for signals transmitted in the form of bursts, each burst comprising a synchronization word and message data that has undergone convolutional coding in a transmitter, the position of the message data relative to the synchronization word being known, includes a detector for detecting the synchronization word, a multiplexer for applying the received signals to the Viterbi decoder in the presence of the message data and for applying to the Viterbi decoder, immediately before and immediately after the message data, a code sequence generated locally, free of errors and having a length at least equal to the truncation length of the Viterbi decoder.

Abstract: A search method for acquisition of time synchronization between a spreading sequence of a receiver and a spreading sequence of a transmitter, the receiver receiving a spread signal and demodulating the signal using the spreading sequence of the receiver includes a test step consisting in measuring the energy of the demodulated signal by integrating the demodulated signal during a time interval Tobs.sub.i and comparing that energy with a threshold value to determine if the threshold value is exceeded, for a given hypothesis as to the time shift between the spreading sequences, and modifying the time shift hypothesis if the threshold value is not exceeded and incrementing the value of a counter. Steps a and b are repeated until the value of the counter reaches a predetermined value. When the predetermined value is reached, the time interval Tobs.sub.i is replaced with a time interval Tobs.sub.i+1, with Tobs.sub.i+1 =m.Tobs.sub.i and m>1, and the process resumes at step a replacing Tobs.sub.i with Tobs.sub.

Abstract: A pseudo-elliptical filter includes positively coupled resonant cavities, the signal input and the signal output of each cavity being at 90.degree. to each other. At least one retro-coupling of signal between two of said cavities is constituted by a waveguide. Applications include pseudo-elliptical filters operating in the millimeter band.

Abstract: A demodulator stage for direct demodulation of a phase quadrature modulated signal provides two baseband signals and comprises a matched 900.degree. coupler to which the modulated signal is fed and supplying two phase quadrature modulated signals. Two low-noise amplifiers with identical specifications each receive one of the phase quadrature modulated signals and supply an amplified signal. Two mixers each receive one of the amplified signals and a common local oscillator signal and supply the baseband signals. The 90.degree. coupler, the low-noise amplifiers and the two mixers can be integrated into the same MMIC. One application is to a receiver for frequency evasive phase quadrature modulated signals.

Abstract: 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.

Abstract: In a method of detecting reference symbols in a digital data stream constituted by successive frames, each frame contains R reference symbols and I information symbols, and the R reference symbols are uniformly spaced apart in the digital data stream. The received signal is sampled with a period T.sub.e =T.sub.s /N.sub.e, where N.sub.e is an integer not less than 2, and T.sub.s is the symbol time. A cross-correlation is calculated, with each calculated cross-correlation supplying a magnitude I.sub.n equal to: ##EQU1## where x.sub.n+dNe represents the sample received at instant n+dN.sub.e, S*.sub.d,k represents the complex conjugate of the reference symbol of index d, k .epsilon. {0, . . . , R-1} and represents frame index, r=R/q, where q is an integer not less than 1. The cross-correlations are summed over M frames so as to form energy levels J.sub.M,d equal to: ##EQU2## where m is the frame index, M is the number of sums performed, and d .epsilon. {0, . . . , N.sub.e (R+1)-1}.

Abstract: A tracking antenna for non-geostationary satellites is mounted on a three-axis positioner comprising an azimuth axis, an elevation axis mounted perpendicularly on the azimuth axis and a pseudo-azimuth axis mounted perpendicularly on the elevation axis and supporting the antenna. The positions of the axes are controlled by a pointing unit. The method of pointing the antenna carries out the following steps simultaneously when the position of the satellite is such that the elevation axis exceeds a predetermined elevation value: modifying the position of the azimuth axis at constant speed and modifying the position of the elevation axis and the pseudo-azimuth axis to track the satellite.

Abstract: Apparatus for correcting quadrature error in a quadrature modulator and/or in a demodulator for a signal having a plurality of phase states, or of amplitude and phase states. The correction apparatus comprises a processor (51) which, when the apparatus is used to correct quadrature error in a demodulator, transforms the levels P and Q of the digital signals output by the demodulation stage into corrected levels P' and Q' that satisfy any one of the following eight relationships: ##STR1## These corrected levels are then applied to decision element (72), optionally after their maximum levels have equalized. The apparatus combines correction accuracy with cheapness, and it enables any quadrature error to be corrected.

Abstract: A magnetic device couples a main conductor of a TEM line and a waveguide forming a .lambda.g/2 resonator and procuring the propagation of an electromagnetic wave. The main conductor is fixed to a wall of the waveguide and extended by a pin inside the waveguide. The device comprises a tuning screw penetrating into the waveguide near the free end of the pin and perpendicular to the pin and an iris around and centered on the pin. The iris is closed on the side on the wall and its interior volume forms a zone in which the wave of the associated magnetic field is evanescent. The median axis of the tuning screw is in the plane of the aperture of the iris.

Abstract: An estimator for estimating the amplitude/frequency characteristic of a source signal from which baseband components i and q which are applied to the inputs of said estimator are derived by demodulation using two signals having orthogonal phases. The estimator includes a combiner for generating complex components i+j.multidot.q and q+j.multidot.i from the components i and q and evaluates the relative amplitudes of the complex components in order to produce a coefficient representative of the amplitude/frequency characteristic of the source signal. The invention can be used to implement a frequency equalizer whose estimator operates in the baseband, the estimator possibly driving a transversal filter operating at the intermediate frequency or at the microwave frequency.

Abstract: In a method of interleaving and deinterleaving STM-1 and STM-N SDH frame pointers transmitted between a transmitter and a receiver, each frame comprising a section overhead area, a pointer area and a payload area including the data to be transmitted. At the transmitter, the bits of the pointer area and those of the payload area are interleaved according to an interleaving law retaining the position modulo 24 in the interleaved bits. The interleaving produces an interleaved frame transmitted to the receiver at which it is deinterleaved using a law that is the reciprocal of the interleaving law. This interleaves all the bits of pointers in the frame without changing the values of the B1 and B2 parity control bytes.