Abstract: The invention provides a multibeam antenna comprising:an array 11 of N.sub.e elementary sources 31; energy-focusing optical means comprising a reflector 10 or a lens; the array being situated in the focal zone of said focusing means: and a feed and control circuit cooperating with the N.sub.e primary sources 31 to produce N.sub.b beams each generated from a subgroup of the primary sources, some of which are shared between overlapping beams; the feed and control circuit comprising phase shifter means and attenuator means, said means being organized in N.sub.e feed channels for said N.sub.e primary sources, each feed channel including specific means for acting on the phase and the amplitude of an excitation signal in each feed channel;wherein each required beam is generated by the multibeam antenna solely by acting on the phase and the amplitude of the excitation delivered to each elementary source forming a portion of said beam; andwherein the number of sources N.sub.i contributing to a beam i, 1.ltoreq.i.

Abstract: A linearization circuit for a non-linear amplifier optimizes the overall efficiency (>50%). To achieve high efficiency the amplifier is operated in class "E" or class "F" and near saturation, causing phase and amplitude non-linearity. Phase non-linearity is corrected conventionally by a phase error signal generated in a feedback loop. Amplitude non-linearity is corrected by operating on the power supply modulator of the non-linear amplifier in an open loop configuration, using the input signal power. Further, more refined correction of amplitude non-linearity can be effected by operating on an automatic gain control amplifier on the input side of the non-linear amplifier, the gain of the automatic gain control amplifier being controlled by an amplitude error signal generated in a feedback loop.

Abstract: A power distributor for microwave signals has n inputs and n outputs, n/2 coupler elements, four power distributor elements each having n/2 inputs and n/2 outputs. The inputs of the first and third distributor elements correspond to respective inputs of the distributor and the outputs of the second and fourth distributor elements correspond to respective outputs of the distributor. The outputs of the first distributor element are connected to respective first inputs of the couplers and the outputs of the third distributor element are connected to respective second inputs of the couplers. The inputs of the second distributor element are connected to respective first outputs of the couplers and the inputs of the fourth distributor element are connected to respective second outputs of the couplers.

Abstract: The present invention relates to a communications system between low-orbit satellites and terminals, in which the beams (12) of each service area (14) are illuminated according to a beam-hopping spatial scanning. For each satellite and for each terminal transmission and reception are separated in time and synchronized. Time-division duplex is used. Applicable especially to the field of space telecommunications.

Abstract: An electronically-scanned two-beam antenna designed for being installed on board a moving platform, and in particular a satellite. The antenna of the invention comprises a single, complex reflector whose reflectivity is responsive to the polarization with which it is illuminated, and associated with two arrays of orthogonally-polarized sources that illuminate the complex reflector using an offset configuration. The complex reflector is made up of two reflectors placed one in front of the other in the beam propagation direction. The first reflector is transparent to a first linear polarization and reflective to an orthogonal polarization, while the second reflector is reflective at least for the first polarization. The two resulting beams thus propagate in different directions, both parallel to the trajectory of the platform. Electronic scanning is provided in a plane perpendicular to the orbit plane.

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: A predistortion linearizer for microwave power amplifiers has a linear channel and a non-linear channel. Both channels are made up of the same units. Each channel includes a variable phase-shifter, a variable attenuator and an amplifier. Each channel can further include a fixed attenuator. The two channels are coupled at their ends by couplers each introducing a phase-shift of 90.degree. so that the total phase-shift is 180.degree.. Because the components of the two channels are the same, any variations with the frequency or the amplitude of the signal or with the operating temperature cancel out. The linearizer has applications in telecommunications and in particular in multicarrier systems.

Abstract: A pulse width modulation type power supply modulator capable of operating at high switching frequencies (>10 MHz) is achieved by eliminating resonant circuits which limit the maximal switching frequency. The modulator includes a power circuit including a power transistor, a first control circuit connected to the gate of the power transistor and a second control circuit connected to the output of the power circuit. In a preferred embodiment the active components are isolated from each other by areas of metalization on a printed circuit to minimize unwanted coupling and the electrical lengths are minimized.

Abstract: A high-throughput filtering method and corresponding apparatus in which each output sample sn is determined by weighting N input samples xi by multiplying the input samples by N coefficients, where the N coefficients are each decomposed into a set of coordinates, each coordinate corresponding to P bits of the coefficient. Essentially, input samples are multiplied by the coordinates of each of the coefficients in a pre-processing operation where the output signals corresponding to the resulting products for a coefficient are added in an adding block. A plurality of adding blocks are provided corresponding respectively to the coefficients such that each block includes the summation result of the products for a corresponding coefficient. The summation result from a previous adding block is added to the summation result of a current block, and the result of this addition is supplied to the next adding block. The output signal is obtained in this manner.

Abstract: The invention proposes a memory relay system for observation spacecraft, for example observation satellites or interplanetary probes. The object of the invention is to alleviate the absence or possible failure of onboard memory of these craft. The system of the invention provides a substitute solution which returns full functionality to an observation system capable of acquiring and transmitting observation data but not of storing it. In accordance with the invention, an artificial satellite or craft comprising at least one transponder and at least one writable memory is disposed near an observation satellite or a probe. The transponder is capable of receiving signals transmitted by the observation satellite or probe and then transmitting the signals to the Earth or to another destination. The memory of this artificial satellite or craft stores the information received until it is retrieved and retransmitted to the receiving station, a station on the ground, for example.

Abstract: A plane antenna suitable for space applications in particular comprises a passive resonator coupled to a feedline by a looped slot.

Abstract: An analytical digitizer for signal processing includes a sampler and an analog/digital converter. A first calculating device supplies a first component of the signal made up of a sequence of digital values. Each value is calculated by adding 2h+2 value supplied by the converter weighted with respective non-null integer coefficients a.sub.0, . . . , a.sub.h, a.sub.h, . . . , a.sub.0. A second calculating device supplies a second component of the signal, in phase quadrature to the first, and made up of a sequence of digital values y(t). Each of these values is calculated by adding 2h+2 values supplied by the converter weighted with respective non-null integer coefficients b.sub.0, . . . , b.sub.h-1, -b.sub.h-1, . . . , -b.sub.0. The number and the value of the coefficients are determined by a rigorous method according to the center frequency and the bandwidth of the spectrum of the signal to be processed and according to a fixed limit value for the signal/noise ratio.

Abstract: A miniaturized radio antenna element for use at VHF and UHF is designed to operate well short of resonance. It comprises a small flat cavity in the surface of which is formed at least one radiating slot very much smaller than a normal resonant slot. However, an impedance matching circuit is often required at the ports of this antenna.

Abstract: In a method of calibrating an active antenna the active elements of a transfer function matrix are measured using a near field probe for each radiating source of the antenna. The probe is placed in front of each source in succession and each source is excited in turn with the opposite phase and with all the other sources of the array excited normally. In the case of linear superposition of radiated fields, the measurements obtained by this method yield the elements of the transfer function matrix directly. This allows for phase and amplitude errors due to the components of the active antenna and for the effects of coupling between adjacent sources which modify the theoretical characteristics of the antenna. In the non-linear case the measurements are repeated and the matrix is obtained by iteration based on a comparison of the theoretical values used to control the antenna and the measured fields actually obtained.

Abstract: A network of switches for a multiple channel installation adapted to establish connections each between one of N input ports and one of T output ports includes: a plurality of cords each having a first end connected to a first nodal switch, a second end connected to a second nodal switch and, between said two ends, at least one cord switch; optionally, a plurality of branches which comprise a switch having one pole at most connected to an input port, two poles available for the connection of output ports and one pole connected to a pole of a nodal switch; and a plurality of nodal switches interconnected by cords, the input and output ports being connected to the available poles of the switches of the network.

Abstract: A multifrequency radiating device comprising at least one radiating element (11) of a first type and at least one radiating element (12) of a second type, the elements being associated on a common surface (10) in order to constitute an array antenna. The radiating elements of the first type (16) are elements of the microstrip type and the elements of the second type (19, 20) are elements of the wire type, the radiating elements of the first type (16) acting in a first frequency range and the radiating elements of the second type (19, 20) acting in a second frequency range. The invention is particularly applicable to microwave antennas.

Abstract: The invention relates to switchable band filter apparatus for switching signals on-board a satellite, enabling signals of different and unforeseeable bandwidths to be switched between multiple input ports and multiple output ports. The invention also provides various payload architectures using such apparatus. Finally, the invention provides methods of implementing such apparatus and architectures for performing transparent switching of signals on-board a satellite.

Abstract: A receiver for receiving frequency modulated signals and having a controlled acquisition band, the receiver including: a phase-locked loop (PLL) demodulator (40); a frequency translation circuit (30) including an intermediate frequency filter (36); a recentering loop (44) for recentering the signal received in the filter (36) when closed, and a decision circuit for closing the recentering circuit when a frequency to which the PLL is locked is sufficiently close to a desired frequency.

Abstract: A direct television broadcasting satellite facility (S1, S2, S3) having at least two coverage areas (T1, T2). At the beginning of the life of the facility, with present Standards, only two satellites (S1, S2) each having two beams (F1 & F2 and F'1 & F'2) are used, each satellite having 12 channel and redundancy amplifiers for five channels. When high-definition television is subsequently introduced progressively, the amplifiers will be coupled together in parallel and in pairs, and at least one additional satellite (S3), identical to the two initial satellites, will be launched when required.

Abstract: In a method of calculation by a GPS receiver of the position of a mobile in space and time relative to a predetermined frame of reference, the position is calculated from data supplied by at least four GPS satellites selected by the GPS receiver to form a calculation constellation. The method includes the step of estimating the error in the position calculation. This error is estimated by the GPS receiver for each calculated position. The estimated error therefore varies with the position of the mobile.