Abstract: In accordance with the invention, the digital samples associated with each of the array elements arranged along a plurality of parallel lines are shifted by a distinct predetermined number of positions along each of said lines, and the digital samples of each line are added separately. Thereafter, each sum thus obtained is multiplied by a distinct phase coefficient. The signals thus obtained for each beam are all in phase. The lines of array elements that are electronically scanned can be oriented along any direction, and advantageously along one or a plurality of diagonals of the array and the electronic scanning of the array elements can be made separately along odd alternate diagonals and along even alternate diagonals.

Abstract: The invention concerns a method and a system for transmitting radio signals between a fixed terrestrial station and mobile user terminals via a network of satellites in inclined circular orbits having a radius less than that of geostationary orbits. The beams generated are divided into pencil beams each associated with a continuous sub-band of frequencies in increasing frequency or decreasing frequency order. The instantaneous transmission frequency is offset progressively during the call towards the frequency subband of the adjacent pencil beam, at a rate proportional to the orbital rotation speed, to enable switching between pencil beams or between satellites. Applications include transmission via satellites in non-geostationary orbit.

Abstract: A procedure for control of a scanning antenna including:a central modulation-management unit (OBS) incorporating an external angular scanning and packet-synchronization bus (BRC),at least N modulation-control devices (MOD.sub.1, . . . MOD.sub.N),at least one beam-forming device (BFN),at least one network comprising M antenna elements (A.sub.1, . . . A.sub.M), the central management unit (OBS) incorporating N first terminals connected respectively to N second terminals of the beam-forming device (BFM) through the N modulation-control devices (MOD.sub.1, . . . MOD.sub.N), and the beam-forming device (BFN) incorporating, on the one hand, M third terminals connected respectively to the M antenna elements respectively (A.sub.1, . . . A.sub.N), and, on the other, a scanning and synchronization terminal connected to the external bus (BRC).

Abstract: A satellite receiver is provided which downconverts an incoming band of signals received at a carrier frequency to a signal spectrum centered about an intermediate frequency (IF). The IF signal spectrum is filtered to provide a group of signals therefrom. The group comprises a subset of all the signals in the incoming band of signals. The group of signals from the IF signal spectrum is sampled at a high frequency which is greater than the highest frequency present in the group but lower than the intermediate frequency, in order to provide the group of signals at baseband directly from the IF signal spectrum.

Abstract: A device in which the frequency band (W) of a multiple carrier signal (MCS) is divided into a number K of sub-bands. The data contained in each sub-band are sampled at a predetermined rate (Sr) to generate a spaced sequence of samples. The data samples from all the sub-bands are time multiplexed to produce a composite signal comprising the K successive spaced sequences of samples. In this way, the composite signal transmits the data at a high apparent rate suitable for demodulation by a conventional multiple carrier demodulator designed for this high data transfer rate. This device is used in satellite communication systems.

Abstract: The system allows the implementation of packet-switched synchronous speech communications in the network without requiring any centralized device synchronizing all the network stations. To obtain that, the active periods of each station are subdivided into frames each having a duration equal to the time elapsing between the generation to two subsequent speech packets relating to the same communication; once a station has accessed the line for the speech communications, these communications are allotted time slots which are maintained for the whole communication duration. The slots not allotted to speech communications are allotted to data transmission. The access to the line for a speech communication is obtained by the same contention techniques used also for data transmission.