Abstract: A communication system includes a set of non-geostationary satellites setting up communication links between ground stations and terminals, the links from a station terminating at associated terminals in a limited geographical area including the station. A communication link between a particular station and the associated terminals is set up by a satellite of the set of satellites. The satellite is commanded to set up for this purpose a steerable transmit beam and a steerable receive beam pointing at the limited area including the particular station and supporting the communication link.

Abstract: A system for transmitting data inside a satellite comprises senders and receivers of digital signals containing the data interconnected by non-directional infra-red links.

Abstract: A repeater for use in a radiocommunication network for relaying data communications between first and second stations between which data communication via the radiocommunication network alone is impossible includes a first converter for converting a first radio signal received from the first station into the form of first receive messages and converting first transmit messages into the form of a first radio signal transmitted to a first station. A second converter converts a second radio signal received from said second station into the form of second receive messages and second transmit messages into the form of a second radio signal transmitted to the second station. An application controller manages the first receive messages and the first transmit messages and the second receive messages and the second transmit messages.

Abstract: A digital filter method comprising the following steps: input signal data x(n) is sampled at sampling frequency Fe and shared between and stored in Q memories of shift register of FIFO type associated with the Q branches of the filter. The filter coefficients g.sub.m (p) are stored in at least one other memory referred to as a "coefficient" memory. Interpolation by L followed by decimation by M makes it possible to reduce the working frequency of the filter to the output frequency Fs=(L/M)Fe with L/M<1. Data samples x(n) are multiplied by the coefficients g.sub.m (p) at the rate Fs. According to the invention, the data samples x(n) in each branch remain present for a plurality of multiplications .apprxeq.Fe/Q, and the coefficients are rotated in each branch by address permutation in the coefficient memory at each clock period. The invention proposes various devices implementing the method. Applications in radar and in telecommunications.

Abstract: A feed device for a radiating element operating in dual polarization, for use especially in the field of space transmission, comprises a first feed line penetrating into a first cavity located beneath said radiating element, and a second feed line disposed in a configuration orthogonal to the first line and penetrating into a second cavity located in line with the first, a conductive part forming a coupling slot between the two cavities.

Abstract: The invention relates to apparatus for detecting the presence or the absence of a signal carrier wave received by a receiver. The carrier wave is modulated by a digital signal at a symbol clock frequency. According to the invention, the apparatus includes:a non-linear circuit receiving the received signal or the received signal after it has been frequency transposed, the non-linear circuit supplying in particular a signal whose frequency corresponds to the symbol clock frequency;a narrow-band filter centered on the symbol clock frequency and supplying a filtered signal;detection means for detecting the filtered signal and for supplying a detection signal; andcomparator means for comparing the detection signal with a reference value, the output signal from the comparator means constituting a signal indicating the presence or the absence of the carrier wave.

Abstract: In a method of handing off traffic in a low orbit satellite communication system serving terminals, a terminal being connected to a terrestrial communication network by means of a connection station, handing off of the satellite-terminal and satellite-connection station links is possible only within a particular area. The decision to hand off the traffic is based on deterioration of the quality of service and of the radio environment for a group of terminals of said area. The system for implementing this method includes transmit/receive terminals and terrestrial connection stations.

Abstract: The invention relates to a communications and/or navigation system based on a constellation of non-geostationary satellites in orbit around the terrestrial globe. The constellation has satellites grouped in pairs, and has orbital planes that are also grouped in pairs. The pairs of orbital planes are mutually spaced apart by an angle that is different from the spacing between the orbital planes in a pair of orbital planes, and the satellites in a pair have orbital phase offsets different from the orbital phase offset between pairs of satellites in different pairs of orbital planes. This type of constellation makes it possible to ensure continuous coverage, via at least one satellite, of a geographical zone of interest, while taking into consideration the frequency-coordination constraint.

Abstract: Apparatus for providing high reception capacity to hand-held or mobile stations using moving satellites in low orbit. The system makes use of one or more geostationary satellites which provide broad band transmission to the users of hand-held or mobile stations. Only the data addressed to hand-held or mobile stations uses the path via the geostationary satellite(s), information coming from the hand-held or mobile stations passing via moving satellites in low orbit. The system enables mobile or hand-held stations to make use of multimedia applications.

Abstract: The invention provides a method of switching a call set up between a first station and a second station from a current propagation path to a following propagation path. The method includes the following steps:a value representative of signal-to-noise ratio is measured for each of said propagation paths, namely the current path and the following path; andthe first station switches the call from a current channel on the current propagation path to a following channel on a following propagation path as a function of values representative of signal-to-noise ratio measured respectively for said current propagation path and for said following propagation path. In the method:the following call channel is reserved for said call; and:in said second station, said call is switched from the current channel to said following channel in response to said call failing to be received in the current channel.

Abstract: A device having radiating elements includes a support structure defining a plurality of unit cells, at least one electronic circuit, connection for supplying at least one input signal to the electronic circuit and at least one radiating element connected to an output of the electronic circuit in order to radiate in response to reception of a signal produced at the output of the electronic circuit. The electronic circuit is encapsulated in a dielectric module to form a microwave electronic module comprising a plurality of unit structures stacked to form a block, each structure comprising a bottom dielectric layer on the top surface of which is disposed an integrated circuit. The radiating element is disposed directly on a first face of the module.

Abstract: A satellite payload having d transparent channels, a first plurality d of band-pass channel filters IMUX of bandwidth .delta. that filter received signals, frequency converters, a plurality k of channel amplifiers (k.gtoreq.d), power amplifiers and a second plurality p of channel filters OMUX that filter the signals amplified by the channel amplifiers and the power amplifiers, d amplifiers assigned to said d channels, the frequency converters including at least one mixer and at least one source of a conversion frequency signal, wherein the g band-pass channel filters IMUX filter the received signals before frequency conversion by the converters.

Abstract: The invention concerns, in particular, a system of observation of geostationary satellites (10.sub.1 -10.sub.n). In accordance with the invention, this system comprises at least one observation satellite (15) in an observation orbit (16, 17) near the geostationary orbit (11), this observation satellite (15) having an apparatus for observation of the geostationary satellites (10.sub.1 -10.sub.n) and an apparatus for transmission of the information obtained from the observation apparatus (20, 21, 22) to a receiver. The invention applies, in particular, to the discrimination of communication, meteorological, early warning and electromagnetic monitoring satellites.

Abstract: An altimetric type measurement method for use on a satellite transmits a pulse towards the surface of the sea and carries out frequency transformation on the return signal resulting from the reflection of this pulse at the surface of the sea. This produces a spectral signal of samples successively comprising:(a)--a first zone with a low amplitude level,(b)--a second zone with a sharply increasing slope ending at a peak, and(c)--a third zone of decreasing slope.Samples of the spectral signal are selected within a selection zone that corresponds to the first and second zones for a predetermined maximal level of the height of the waves at the surface of the sea and maximum likelihood processing is applied only to the selected samples.

Abstract: The invention provides a microwave module including a plurality of stacked elementary structures forming a unit, each elementary structure comprising a bottom dielectric layer on a top surface of which an integrated circuit (20, 21) is disposed, and a top dielectric layer covering the circuit (20, 21). The module is characterized by a connection line (20a, 30, 21a) between two respective circuits belonging to first and second elementary structures, the connection line being constituted by an input coplanar line (21a) disposed on the top surface of the bottom dielectric layer of the first structure, by an output coplanar line (20a) disposed on the top surface of the bottom dielectric layer of the second structure, and a by link coplanar line (30) connecting one end of the input coplanar line to one end of the output coplanar line.

Abstract: Method of protecting a planetary rover vehicle, that travels in a manner that is at least partially autonomous, against an exterior environment that has become hostile wherein the vehicle takes shelter and emerges from shelter against the exterior environment of its own accord, respectively in response to first and second events delimiting a period in which the exterior environment is hostile. The vehicle is therefore isolated from the exterior environment during this period.

Abstract: In a telecommunication network, the power of a first signal transmitted via a satellite by a first station to be received in the form of a second signal by a second station is regulated. At a given time, a value representative of a signal-to-noise ratio of the second signal is predicted for a later time, and, at an intermediate time, the power of the first signal is regulated in the first station as a function of the predicted value. The intermediate time precedes the later time by a time period substantially equal to the propagation time between the first and second stations.

Abstract: The invention provides a method of regulating the power of transmission between first and second stations in a multiple satellite visibility satellite telecommunication network. The method comprises the following cyclic steps: regulation, for each of said N channels, of an isolated transmit power level command signal such that when it commands the power at which the first station transmits the first isolated signal in each channel the quality level of the corresponding isolated second signal received by the second station is equal to a reference quality level, and regulation, for all of the N channels, of N combined transmit power level command signals such that when they command the levels at which the first station respectively transmits the N first combined signals on the N channels the quality level of the global signal received formed from the N combined second signals is equal to the reference quality level.

Abstract: A method of defocusing range ambiguities in a pulse radar, in particular of the SAR type, the method comprising the following steps:radar pulses are spread on transmission by using a plurality of "chirp" rules for varying the frequency of the transmitted wave as a function of time;during transmission of successive pulses, chirp rules are alternated between chirps that rise and chirps that fall in the frequency/time plane of the pulse;received echoes are compressed by matched filtering using a correlation operation between the received echo signal and the chirp rule that was applied at the time of transmission of the pulse that gave rise to said echo signal;said method being characterized in that said plurality of rules for varying the frequency of the transmitted wave as a function of time comprise a number M of said rules, with M being an integer greater than or equal to 3.

Abstract: An antenna is orientable, directional and capable of use as a transmit and/or receive antenna. It includes at least one reflector, at least one source of electromagnetic radiation including means for exciting the source with two orthogonal linear polarizations and a mechanical system for positioning and holding the source and the reflector. The orientation of the antenna is made up of depointing and rotation about a preferred direction of propagation of the radiation and the mechanical system enables such rotation while keeping the source fixed, so conserving the orientation of the orthogonal linear polarization. A preferred embodiment of the antenna includes a parabolic main reflector and a hyperbolic auxiliary reflector in a Cassegrain geometry, and the mechanical system enables rotation of both reflectors about the preferred direction of radiation and holds the source fixed to conserve the orthogonal linear polarization axes of the beam.