EP2429036A1 - Increased capacity multi-beam telecommunication antenna on board of a satellite and an associated telecommunication system - Google Patents

Abstract

The antenna has a single radioelectric reflector (62) to reflect a portion of electromagnetic energy emitted by a source block and/or to intercept a portion of electromagnetic energy emitted from a geographical area. The source block is dimensioned and arranged such that each of radioelectric sources of the block generates and/or receives a different single beam, and first angular separation (thetaS1) is equal to second angular separation (thetaS2), where spill-over associated with each source is comprised between 3 and 7.5 decibel. Independent claims are also included for the following: (1) a telecommunication payload comprising a repeater (2) a telecommunication system comprising satellite access stations emitting and/or receiving radioelectric signals.

Description

The present invention relates to a telecommunication antenna intended to be on board a telecommunication satellite, a payload of a telecommunication satellite comprising the antenna, and a telecommunication system using the payload and therefore the antenna of telecommunication.

In general, and so far in the case of space telecommunications using geostationary satellites for the transmission of multimedia services in Ka-band, it is sought to extend the coverage provided by the on-board telecommunication antenna or antennas and to increase the transmission capacity while ensuring a performance in C / I (useful signal ratio on interfering signals) high.

To obtain the expected system-level performance, it is necessary to have telecommunication antennas which provide sufficient spatial isolation between beams or their footprints, henceforth referred to as elementary zones or spots, so as to allow fixed or programmed reuses. dynamic of all or part of the frequency resources allocated to the system (reuse of frequencies).

Given the large number of spots to be made, a large number of directional antennas is to be implemented on the same satellite platform and it is also necessary to have structures with large focal length to achieve high insulation performance between beams associated with severe pointing stability.

Today, Ka-band multimedia missions use multi-reflector antenna solutions. Indeed the use of multiple reflectors allows to use sources large enough to illuminate the reflectors optimally and thus form fine beams with a high maximum directivity (high antenna output).

Thus, the most recent satellite in Europe using this type of antenna is the satellite called Ka-sat of the operator Eutelsat. It provides European coverage using about 80 beams of 0.45 ° angular aperture generated by four reflectors 2.6 meters in diameter. Each of these reflectors operates on a go-down transmission path and an uplink receive path. This communication system is intended to provide a total capacity of approximately 70 Gbps, the minimum C / I coverage ratio being in the order of 14 dB.

It should be noted that the satellite Ka-sat could have used a single reflector of 2.6 meters in diameter. In this case it would have been necessary to make sources smaller illumination, which would have degraded the performance of the antenna including the increase in energy losses overflow (called spill-over), typically 4 to 6 dB. The remaining C / I performance of about 12 dB loss of antenna efficiency would have resulted in a degradation of Isotropic Emitted Radiated Power (EIRP), which would have resulted in a loss of capacity of the transmission system. noticeable and unwanted telecommunications.

Today, several missions are distinguished, ranging from coverage of a large region, for example Europe, to coverage of one or a limited number of European countries.

Coverage studies for one to three countries are currently the subject of much research and development. For example, the provision of a high-capacity multimedia telecommunications satellite with a coverage area of the size of France is envisaged.

In these systems under study and development, the increase in capacity is always sought by the use of a wider allocated bandwidth when the regulation allows it or by the reuse of the spectrum in zones reduced to using very fine brushes.

Bridging this gap in terms of capacity then requires the use of finer beams.

However, the carrying capacities of the current platforms and launchers do not make it possible to envisage solutions with multiple reflectors of diameter greater than 3 meters or 3.5 meters.

Thus the use of four reflectors of 3.2 meters in diameter currently corresponds to a limit configuration of carriage on a satellite to enter a cap of a launcher.

For this configuration of antennas with four reflectors and optimizing the most important determining parameters of the system, we obtain a capacity of about 65 Gbits / s with 36 beams on France.

In this limit configuration, the sources are optimized for the four reflectors and the overflow losses are around 2 dB for a minimum C / I of the order of 9 dB.

In addition, as the number of beams increases, the C / I observed becomes very low and, despite the reuse of frequencies, the capacity decreases.

The technical problem is to increase the transmission capacity of the satellite under satellite operating conditions identical to those presented for the limit configuration in terms of the power consumed by the multimedia payload of the satellite. satellite, frequency band allocated to the downlink, characteristics of the terminals and carriage constraints on a satellite intended to fit into a launcher cap.

• au moins un réflecteur radioélectrique, et
• un bloc source associé, formé d'une pluralité de sources radioélectriques élémentaires disposées dans un plan,
• la pluralité des sources radioélectriques élémentaires étant configurée pour illuminer le réflecteur par un rayonnement électromagnétique dans une bande de fréquences et/ou pour être illuminé par un rayonnement électromagnétique dans une bande de fréquences réfléchi par le réflecteur selon un ensemble multifaisceaux primaire de faisceaux adjacents primaires répartis en au moins un ensemble connexe de faisceaux primaires adjacents, deux faisceaux primaires quelconques adjacents étant séparés par une première séparation angulaire θ_S1,,
• le réflecteur étant configuré pour réfléchir une partie de l'énergie électromagnétique émise par le bloc source et/ou pour intercepter une partie de l'énergie électromagnétique émise depuis la zone géographique, selon un ensemble multifaisceaux secondaire de faisceaux réfléchis adjacents secondaires répartis en au moins un ensemble connexe de faisceaux secondaires adjacents, deux faisceaux secondaires quelconques adjacents étant séparés par une deuxième séparation angulaire θ_S2,
• caractérisée en ce que
• le réflecteur est unique, et
• le bloc source est dimensionné et agencé de sorte que chaque source est apte à générer et/ou recevoir un faisceau unique différent et que la première séparation angulaire θ_S1 est sensiblement égale à la deuxième séparation angulaire θ_S2, et
• les pertes d'énergie par débordement associées à chaque source sont comprises entre 3 et 10 dB, de préférence comprises entre 3 et 7,5 dB.

To this end, the subject of the invention is a multibeam telecommunication antenna intended to equip a high-speed telecommunication payload for transmitting and / or receiving a geographical area from a geostationary orbit, able to be mounted mechanically on a satellite. or two satellite platforms and to be electromagnetically coupled to a repeater, comprising:

• at least one radio reflector, and
• an associated source block formed of a plurality of elementary radioelectric sources arranged in a plane,
• the plurality of elementary radioelectric sources being configured to illuminate the reflector with electromagnetic radiation in a frequency band and / or to be illuminated by electromagnetic radiation in a frequency band reflected by the reflector according to a primary multibeam set of distributed primary adjacent beams in at least one connected set of adjacent primary beams, any two adjacent primary beams being separated by a first angular separation θ _S1 ,,
• the reflector being configured to reflect a portion of the electromagnetic energy emitted by the source block and / or to intercept a portion of the electromagnetic energy emitted from the geographical area, according to a secondary multibeam ensemble of adjacent secondary reflected beams distributed in at least a connected set of adjacent secondary beams, any two adjacent secondary beams being separated by a second angular separation θ _S2 ,
• characterized in that
• the reflector is unique, and
• the source block is dimensioned and arranged so that each source is able to generate and / or receive a different single beam and that the first angular separation θ _S1 is substantially equal to the second angular separation θ _S2 , and
• the overflow energy losses associated with each source are between 3 and 10 dB, preferably between 3 and 7.5 dB.

• le réflecteur est un réflecteur non conformé, et
• le plan dans lequel sont disposées les sources radioélectriques est un plan focal du réflecteur ;
  • le réflecteur est une portion de paraboloïde centrée sur son centre de symétrie de paraboloïde C_P,
• le plan focal du réflecteur dans lequel sont disposées les sources radioélectriques est orthogonal à l'axe passant par le centre de symétrie C_P du paraboloïde et le point focal F1 du paraboloïde,
• une source quelconque du bloc source a une taille d'ouverture notée T_source, qui vérifie la relation
• T_source ≤ F ^∗ tan(θ _s2 ^∗ (1 + ε))
• dans laquelle
• F désigne la distance focale égale à la distance entre le centre C_P de symétrie de la portion de paraboloïde et le point focal F1 du paraboloïde,
• Θs2 désigne la séparation angulaire de deux faisceaux adjacents secondaires, et
• ε est un coefficient numérique compris entre 0 et +0,35 ;
  • le réflecteur est une portion d'un paraboloïde décalée par rapport au bloc source de façon à éviter le masquage des faisceaux secondaires par le bloc source, et
• une source quelconque du bloc source a une taille d'ouverture notée T_source, qui vérifie la relation
• T_source ≤ Feq ^∗ tan(θ _s2 ^∗ (1 + ε))
• dans laquelle
• F_eq désigne une distance focale équivalente égale à la distance entre un centre C_D de découpe de la portion de paraboloïde et le point focal F1 du paraboloïde,
• Θs2 désigne la séparation angulaire de deux faisceaux adjacents secondaires, et
• ε est un coefficient numérique compris entre 0 et +0,35 ;
  • le réflecteur est une portion d'un paraboloïde, et
• le bloc source comprend au moins un ensemble de sources radioélectriques adjacentes formées de cornets à ouverture circulaire, chaque cornet de l'ensemble ayant un diamètre D_source incluant l'épaisseur métallique de la paroi du cornet, et
• le diamètre D_source de l'ouverture vérifie la relation :
  • D_source = Feq ^∗ tan(θ_s2 ^∗ (1+ε)) lorsque le réflecteur est une portion d'un paraboloïde décalée par rapport au bloc source, et la relation
  • D_source = F ^∗ tan(θ _s2 ^∗ (1+ε)) lorsque le réflecteur est une portion de paraboloïde centrée sur son centre de symétrie de paraboloïde C_P,
• dans lesquelles
• F désigne la distance focale égale à la distance entre le centre C_P de symétrie de la portion de paraboloïde et le point focal F1 du paraboloïde,
• F_eq désigne une distance focale équivalente égale à la distance entre un centre C_D de découpe de la portion de paraboloïde et le point focal F1 du paraboloïde,
• Θs2 désigne la séparation angulaire de deux faisceaux adjacents secondaires, et ε est un coefficient numérique compris entre 0 et +0,35 ;
  • le bloc source et le réflecteur sont configurés pour fonctionner dans une bande de fréquence comprise dans l'ensemble des bandes C, Ku, Ka ;
  • la disposition des sources radioélectriques dans le plan est celle d'une configuration correspondant à une distribution optimisée pour un nombre de couleurs égal à 3, 4, ou 7 ;
  • la valeur minimale sur la couverture géographique du rapport C/I entre, d'une part l'énergie émise et/ou reçue par le réflecteur dans un faisceau secondaire quelconque, et d'autre part la somme des énergies émises et/ou reçues dans le même faisceau secondaire et émises et/ou reçues par le réflecteur depuis les autres faisceaux de même couleur que le faisceau secondaire, est inférieur à 15 dB, de préférence à 12 dB.

According to particular embodiments, the telecommunication antenna comprises one or more of the following characteristics:

• the reflector is an unconformed reflector, and
• the plane in which the radioelectric sources are arranged is a focal plane of the reflector;
  • the reflector is a paraboloid portion centered on its paraboloid center of symmetry C _P ,
• the focal plane of the reflector in which the radioelectric sources are arranged is orthogonal to the axis passing through the center of symmetry C _P of the paraboloid and the focal point F1 of the paraboloid,
• any source of the source block has an opening size denoted T _source , which verifies the relation
• T _source ≤ F ^* tan ( θ _{s 2} ^* (1 + ε ))
• in which
• F denotes the focal length equal to the distance between the center of symmetry C _P of the paraboloid portion and the focal point F1 of the paraboloid,
• Θs2 denotes the angular separation of two adjacent adjacent beams, and
• ε is a numerical coefficient between 0 and +0.35;
  • the reflector is a portion of a paraboloid offset from the source block so as to avoid the masking of the secondary beams by the source block, and
• any source of the source block has an opening size denoted T _source , which verifies the relation
• T _source ≤ Feq ^* tan ( θ _{s 2} ^* (1 + ε ))
• in which
• F _eq denotes an equivalent focal length equal to the distance between a cutting center C _D of the paraboloid portion and the focal point F1 of the paraboloid,
• Θs2 denotes the angular separation of two adjacent adjacent beams, and
• ε is a numerical coefficient between 0 and +0.35;
  • the reflector is a portion of a dish, and
• the source block comprises at least one set of adjacent radioelectric sources formed of circular opening horns, each horn of the assembly having a _source diameter D including the metal thickness of the wall of the horn, and
• the diameter D _source of the opening satisfies the relation:
  • D _source = Feq ^* tan ( θ _s2 ^* (1+ ε )) when the reflector is a portion of a paraboloid offset from the source block, and the relation
  • D _source = F ^* tan ( θ _{s 2} ^* (1+ ε )) when the reflector is a paraboloid portion centered on its paraboloid center of symmetry C _P ,
• in which
• F denotes the focal length equal to the distance between the center of symmetry C _P of the paraboloid portion and the focal point F1 of the paraboloid,
• F _eq denotes an equivalent focal length equal to the distance between a cutting center C _D of the paraboloid portion and the focal point F1 of the paraboloid,
• Θs2 denotes the angular separation of two adjacent adjacent beams, and ε is a numerical coefficient between 0 and +0.35;
  • the source block and the reflector are configured to operate in a frequency band included in the set of C, Ku, Ka bands;
  • the arrangement of the radio sources in the plane is that of a configuration corresponding to an optimized distribution for a number of colors equal to 3, 4, or 7;
  • the minimum value over the geographical coverage of the C / I ratio between, on the one hand, the energy emitted and / or received by the reflector in any secondary beam, and, on the other hand, the sum of the energies emitted and / or received in the same secondary beam and emitted and / or received by the reflector from the other beams of the same color as the secondary beam, is less than 15 dB, preferably 12 dB.

The subject of the invention is also a telecommunication payload intended to transmit and / or receive data at a high bit rate, comprising a transmitting and / or receiving antenna as defined above and a repeater, characterized in that
the repeater comprises a set of transmission channels in transmission and / or in reception,
each transmission channel comprising
an output and / or radio input terminal connected to a single radio source and different from the source block, and
configured to provide radio signals in a sub-band of frequency B (i) out of a predetermined number Nb of frequency sub-bands forming an allocated frequency band, and in that
each sub-band B (i) being associated with a color, the transmission channels are capable of distributing the frequency sub-bands in transmission and / or reception to all the elementary radioelectric sources so that the ground diagram formed by the colors associated with the different secondary beams generated by the antenna is a diagram with Nb optimized frequency reuse colors, that is to say a diagram for which the angular distance between two beams using the same color is the most large on all possible diagrams.

• un satellite de télécommunication équipé d'une charge utile telle que définie ci-dessus,
• un ensemble de terminaux de télécommunication pouvant transmettre et/ou recevoir des signaux radioélectriques vers/depuis le satellite,
• une ou plusieurs stations d'accès satellitaire aptes à émettre et/ou recevoir des signaux radioélectriques aux/des terminaux au travers du satellite suivant une liaison montante aller et/ou retour , et
• chaque terminal est apte à déterminer le rapport C/I+N observé par son antenne respective et/ou par l'antenne satellite entre, d'une part l'énergie C reçue associée au signal radioélectrique utile du terminal et contenue dans le faisceau secondaire de couverture du terminal, et d'autre part, la somme I des énergies reçues dans le même faisceau secondaire mais émises depuis les autres faisceaux secondaires de même couleur que la source associée au faisceau secondaire de couverture du terminal et de l'énergie N du bruit thermique reçu,
• et comprend un dispositif d'adaptation de débit reçu ou transmis en fonction des conditions de C/I+N observées, le débit étant variable par la modification du nombre d'états d'une modulation et/ou le taux de codage et/ou le débit symbole.

The invention also relates to a satellite telecommunication system comprising:

• a telecommunication satellite equipped with a payload as defined above,
• a set of telecommunication terminals capable of transmitting and / or receiving radio signals to / from the satellite,
• one or more satellite access stations able to transmit and / or receive radio signals to / from the terminals through the satellite in a forward and / or return uplink, and
• each terminal is able to determine the ratio C / I + N observed by its respective antenna and / or by the satellite antenna between, on the one hand, the received energy C associated with the useful radio signal of the terminal and contained in the secondary beam of the terminal, and on the other hand, the sum I of the energies received in the same secondary beam but emitted from the other secondary beams of the same color as the source associated with the secondary beam of coverage of the terminal and the energy N of the terminal. received thermal noise,
• and comprises a rate matching device received or transmitted according to the conditions of C / I + N observed, the bit rate being variable by the modification of the number of states of a modulation and / or the coding rate and / or the symbol flow.

• la Figure 1 est une vue générale de l'architecture d'un système de télécommunication à satellite géostationnaire selon l'invention;
• la Figure 2 est une vue géométrique du satellite et de la couverture de service permettant de visualiser l'angle d'élévation du satellite vu d'un point quelconque de la couverture ;
• la Figure 3 est une vue partielle de la couverture de l'antenne de télécommunication du satellite des Figures 1 et 2 avec la répartition des fréquences associées aux faisceaux suivant une configuration à quatre couleurs ;
• la Figure 4 est un schéma du système de télécommunication permettant de visualiser le lien entre la répartition des sous-bandes sur les sources de l'antenne et la distribution des sous-bandes sur les faisceaux de la voie descendante allant du satellite aux terminaux;
• la Figure 5 est une vue du bloc source de l'antenne de la Figure 4 configuré suivant une répartition à quatre couleurs;
• la Figure 6 est une vue d'une coupe de l'antenne de la Figure 4 suivant l'axe VI-VI ;
• la Figure 7 est une variante à trois couleurs du bloc source de la Figure 5 ;
• la Figure 8 est une vue partielle du répéteur du satellite et de son couplage électrique au bloc source de l'antenne ;
• la Figure 9 est une vue partielle de la couverture de service obtenue avec le satellite de la Figure 2 équipé de l'antenne de télécommunication des Figures 4 et 5, et du bloc source à quatre couleurs de la Figure 5 ;

Suivant la Figure 1, un système 2 de télécommunication, ici de services multimédia, à satellite comprend un ensemble 4 de terminaux multimédia 6, 8, 10, un satellite 12 en orbite géostationnaire autour de la Terre 14, une infrastructure terrestre multimédia 16 et plusieurs stations 18, 19, 20, 21 d'accès au satellite (dénommées classiquement « gateway » en anglais), connectées chacune à l'infrastructure terrestre 16 par une liaison de communication différente, non représentée, en des bornes de connexion respectives 22, 23, 24, 25.The invention will be better understood on reading the description of a single embodiment which will follow given solely by way of example and with reference to the drawings in which:

• the Figure 1 is a general view of the architecture of a geostationary satellite telecommunications system according to the invention;
• the Figure 2 is a geometric view of the satellite and the service coverage for viewing the elevation angle of the satellite as viewed from any point in the coverage;
• the Figure 3 is a partial view of the coverage of the telecommunication antenna of the satellite of Figures 1 and 2 with the distribution of the frequencies associated with the beams in a four-color configuration;
• the Figure 4 is a schematic of the telecommunication system for visualizing the link between the distribution of the subbands on the antenna sources and the distribution of the subbands on the downlink beams from the satellite to the terminals;
• the Figure 5 is a view of the source block of the antenna of the Figure 4 configured in a four-color pattern;
• the Figure 6 is a view of a section of the antenna of the Figure 4 along the axis VI-VI;
• the Figure 7 is a three-color variant of the source block of the Figure 5 ;
• the Figure 8 is a partial view of the satellite repeater and its electrical coupling to the source block of the antenna;
• the Figure 9 is a partial view of the service coverage obtained with the satellite of the Figure 2 equipped with the telecommunications antenna of the Figures 4 and 5 , and the four-color source block of the Figure 5 ;

Following the Figure 1 , a telecommunication system 2, here of multimedia services, to satellite comprises a set 4 of multimedia terminals 6, 8, 10, a satellite 12 in geostationary orbit around the Earth 14, a multimedia terrestrial infrastructure 16 and several stations 18, 19 , 20, 21 of access to the satellite (conventionally called "gateway" in English), each connected to the terrestrial infrastructure 16 by a different communication link, not shown, to respective connection terminals 22, 23, 24, 25 .

The multimedia system 2 is supposed to serve a geographical coverage area 26 of small extent, between 500 000 km ² and 1 500 000 km ² .

Typically this corresponds for the northern hemisphere to one, two or three countries the size of France each.

Here as an example, the coverage area 26 of the telecommunications service is France, and it lies between the meridians located at 5 ° west and 6 ° east, between latitudes 43 ° north and 51 ° north.

The geostationary satellite 12 in geostationary orbit around the Earth 14 is placed on a first arc of the geostationary orbit near or contained in a second geostationary arc flying over the meridians of the extremity surrounding France. Here on the Figure 1 the geostationary satellite 12 is located on a median meridian crossing the center of France.

With respect to the coverage area 26, the satellite 12 is located in a southern geographical direction 30 represented by the end arrow towards the rear of the plane of the Figure 1 . A north direction 32, opposite the south direction 30, is represented by a circumferential arrow on the surface of the Earth 14.

From the coverage area 26, the satellite 12 is viewed at an elevation angle designated El and shown in FIG. figure 2 as being a mean angle between the tangent in a longitudinal direction 34 at any point 36 of the cover 26 and the vector ray 38 connecting the point 36 of the cover 26 and the satellite 12.

Following the Figure 1 the satellite 12 comprises a stabilized geostationary platform 40, two solar panels 42, 44 and a multimedia telecommunication payload 46.

The payload 46 is able to ensure the retransmission of multimedia services from the access stations 18, 19, 20, 21 to the multimedia terminals 6, 8, 10.

The payload 46 is able to receive multimedia signals transmitted on an upstream channel 48 in a first band Ka by the access stations 18, 19, 20, 21.

The payload 46 is capable of transmitting the multimedia signals received to the terminals 6, 8, 10 in a downlink channel 50 operating in a second band Ka, distinct from the first band Ka.

The payload 46 is here transparent by limiting itself to the amplification and frequency translation of the multimedia signals.

The payload 46 comprises a multimedia reception satellite antenna 52, a multimedia broadcast satellite antenna 54, and a multimedia mission repeater 56 connected between the multimedia reception satellite antenna 52 and the multimedia broadcast satellite antenna 54 by electrical connections 58 and 60.

The multimedia repeater 56 comprises a power supply 61 of the payload 46 capable of conditioning the electrical energy supplied by the solar panels 42, 44 for the electrical elements constituting the payload 46.

The multimedia broadcast satellite antenna 54 is a multibeam reflector antenna.

It comprises a single reflector 62 having a focal plane 63 remote by a focal length F and a source block 64 comprising a plurality of elementary sources 66 of predetermined number Ns.

The single reflector 62 is able to intercept part of the electromagnetic energy emitted by the source block 64 and to reflect the electromagnetic energy towards the coverage area 26 in descending multibeams.

The reflector 62 is unique and has an apparent diameter D of 5 meters so as to form beams of angular size between 0.10 ° and 0.22 °.

Indeed, it is well known that the opening angle of a beam generated by a radiating aperture having an apparent diameter is proportional to the wavelength of the radiation and inversely proportional to the apparent diameter. Here the radiating opening is the reflector 62.

The elementary radioelectric sources 66 are arranged in the focal plane 63 and are able to illuminate the single reflector 62 by electromagnetic radiation in a Ka or Ku frequency band.

The source block 64 is of the single-source per beam (SFB) type, each source being able to generate a different single beam and the diameter of each elementary source being equal to the image diameter in the focal plane of the beam. associated beam.

In a general manner and in all that follows, a beam of electromagnetic energy is called "primary" when it is established between an elementary source 66 of the source block 64 and the reflector 62, and the beam is called "secondary" when it is established between the reflector 62 and an elementary zone of the cover 26, regardless of the direction of propagation of the energy in the beam, that is to say of the transmission or reception mode of the antenna 46.

The arrangement of the reflector 62 with respect to the platform 40, the orbital position and the stabilized attitude of the platform 40, the configuration of the antenna are chosen so that the antenna 54 generates secondary secondary beams covering by their footprint the Geographic coverage area 26 corresponding to France.

The plurality 64 of the elementary radioelectric sources 66 forming the source block is configured to illuminate the reflector 62 by electromagnetic radiation according to a primary multibeam ensemble of primary adjacent beams, not shown in FIG. Figure 1 , divided into at least one connected set of adjacent primary beams, any two adjacent primary beams being separated by a first angular separation.

The reflector 62 is configured to intercept a portion of the electromagnetic energy emitted by the source block 64 and to reflect it according to a secondary multibeam set of secondary secondary reflected beams 68 distributed in at least one connected set of adjacent secondary beams, two secondary beams. any adjacent ones being separated by a second angular separation.

The source block 64 is sized and arranged so that the first angular separation is substantially equal to the second angular separation. The relative variation between the first angular separation and the second angular separation is less than 25%.

dans laquelle θ _s2 désigne la deuxième séparation angulaire, θ _s1, désigne la première séparation angulaire, et BDF est un coefficient dénommé facteur de déviation de faisceau (en anglais Beam Deviation Factor) inférieur à 1 et dépend du rapport F/D et l'apodisation de la source élémentaire.Strictly speaking, the first angular separation and the second angular separation are connected by the relation: $${\theta }_{s2}={\theta }_{s1}\mathrm{.}BDF,$$

in which θ _{s 2} denotes the second angular separation, θ _{s 1} , denotes the first angular separation, and BDF is a coefficient referred to as the deflection factor of beam (in English Beam Deviation Factor) less than 1 and depends on the F / D ratio and the apodization of the elementary source.

In practice, the coefficient BDF is between 0.7 and 1.

Here, only one secondary beam 68 descending, is shown in dashed line.

The overflow energy losses associated with each source 66 are between 3 and 10 dB, preferably between 3 and 7.5 dB.

Each source 66 is distinguished using an integer index k, with k varying between 1 and Ns, and denoted S (k). Each source S (k) is capable of receiving a distinct set of multimedia signals in a transmission sub-band B (i) taken from a set of distinct Nb subbands and without a cover band, the set of sub-bands. bands (B (i)) constituting a partition of the transmission band of the going way down, that is to say a partition of the second band.

Each source S (k) is able to illuminate the reflector so as to reroute the signals in the downlink way 50 over a different associated elementary area S (k) of the coverage area 26.

Here on the Figure 1 , there are shown only 16 elementary zones forming a partial connected paving of the coverage area 26 and designated by the references 210, 212, 214, 216, 218, 220, 222, 224, 226, 228, 230, 232, 234, 236 , 238, 240.

The optimal use of the frequency spectrum allocated on the downlink channel 68 in terms of capacity is obtained by the reuse of frequencies through the multibeam antenna 54.

The multibeam antenna 54, with a single reflector 62 and with a source block of the "mono-source beam" type or SFB, as described above, allows the reuse of frequencies.

The reuse of the same frequency band on several elementary zones of the coverage area 26 requires the consideration of the insulation performance of the antenna 54 multibeam.

Indeed, the insulation between adjacent beams being difficult to obtain, we can not reuse the same frequency band for them. The frequency band allocated for the multimedia service or second band is partitioned and a reuse of 1 / Nb is defined, in which Nb denotes a number of different colors, by associating a color with a subset of elementary zones (also called English "spot"), disjointed and distant from each other so as to have sufficient insulation. To each different color is assigned an integer index i, with i varying from 1 to Nb, and a subset of elementary zones A (i) or beams F (i). Reuse allows to spatially separate two beams using the same carrier frequency or subband.

A distribution or distribution of the Nb colors on the elementary zones or the descending beams, "optimal" in terms of frequency of re-use and minimum C / I, is chosen among the possible distributions of Nb colors on all the beams and consequently on all of their footprints, ie the basic zones of coverage.

The "optimal" distribution of the Nb colors is optimal in terms of the frequency of reuse when the frequency of reuse of each color is substantially the same, that is to say equal to 1 / Nb, the edge effects being negligible when the number elementary areas is high.

An "optimal" distribution of Nb colors is optimal in terms of C / I when the C / I on the cover 26 is maximal over all the possible distributions of Nb colors on all the beams.

The use of the multibeam antenna 54 with a single large reflector 62 having a diameter greater than 4 meters using the single-beam source concept (English SFB for Single Feed per Beam) is advantageous.

Indeed, the multibeam antenna 54 allows for a fixed frequency reuse factor and an optimal scheme of reuse to increase the capacity of the system.

The proposed telecommunication antenna is certainly suboptimal from an antenna subsystem point of view if it is considered in isolation. Indeed the spacing between the spots of the cover requires the use of sources of small diameters. They are thus not very directive and induce large losses in terms of spill-over, between 5 and 6 dB.

This solution makes it possible to envisage a number of beams on the cover much more important because thinner than in the already known solutions.

dans laquelle B (totale) désigne la bande totale disponible exprimée en Hz, B(allouée) désigne la bande de fréquence allouée suivant les dispositions règlementaires pour la deuxième bande, ρ désigne le facteur de réutilisation de fréquence, η désigne l'efficacité spectrale exprimé en bits/s/Hz.At first glance the capacity of a multibeam system satisfies the following relation: $$\mathrm{VS}\mathrm{=}\mathrm{B}\left(\mathrm{t}\mathrm{o}\mathrm{t}\mathrm{at}\mathrm{l}\mathrm{e}\right)\mathrm{*}\mathrm{\eta }\mathrm{=}\mathrm{B}\left(\mathrm{at}\mathrm{l}\mathrm{l}\mathrm{o}\mathrm{u}\mathrm{ed}\mathrm{e}\right)\mathrm{*}\mathrm{\rho }\mathrm{*}\mathrm{\eta }$$

where B (total) is the total available band expressed in Hz, B (allocated) is the frequency band allocated according to the regulatory provisions for the second band, ρ is the frequency reuse factor, η is the expressed spectral efficiency in bits / s / Hz.

The spectral efficiency η is a function of the frequency density of EIRP (transmitted Isotropic Radiated Power) expressed in W / MHz, of the C / I, of the merit factor of the terminal and therefore of the C / N ratio, where N denotes the noise of observed thermal origin, and the waveform envisaged.

The total available band increases with the number of beams on the cover.

The spectral efficiency decreases with the number of beams because of a lower C / I on all the beams and thus with the degradation of C / N + I.

Here, the multibeam antenna 54 allows a gain in capacity in terms of increasing the number of beams despite spill over losses.

The two multimedia terminals 6, 8 are located in the elementary zone 210.

The third terminal 10 is located in the elementary zone 234, here assumed by way of example assigned the same color, that is to say operating in the same frequency sub-band of the second band.

Thus, the C / I observed by the third terminal 10 comprises a component generated by the signals of the terminals 6 and 8, and received due to the lack of insulation of the beam 68 covering the elementary zone 210 with the beam covering the elementary zone 234 .

Each terminal has a G / T factor equal to 16.4 dB / ° K, an antenna gain equal to 40 dB, which corresponds to an antenna diameter of about 65 cm.

Each terminal 6, 8, 10 respectively comprises a flow matching device 250, 252, 254 as a function of the C / I conditions observed.

Each rate adaptation device is capable of implementing a rate adaptation mode typically the "ACM" mode of the DVB-S2 described in the corresponding standard of the ETSI (European Telecommunication Standard Institute).

A modulation can be chosen according to the C / I + N observed among the Quadrature Phase Shift Keing (QPSK) modulation, the 8-Phase Shift Keing (8-PSK) modulation, the 16-APSK modulation. 16-Amplitude & Phase Shift Keing) and 32-APSK (32-Amplitude & Phase Shift Keing) modulation. The coding may vary between the 1/4 and 9/10 rates offered by the LDPC code used in the DVB-S2 standard.

In this example, the adaptive coding rate associated with the QPSK modulation can vary between 3/4 and 8/9.

In this example, the adaptive coding rate associated with the 8-PSK modulation can vary between 3/5 and 3/4.

Due to the low C / I values that can be observed with the multibeam antenna 54, i.e., values up to a minimum C / I of +9 dB, the rate matching devices 250, 252, 254 allow to use modulation / coding combinations with a spectral efficiency to maximize the capacity of the system.

In contrast to what is known, the multimedia telecommunication system of the invention operates with low spectral efficiency values.

Increasing the redundancy on the error correction code, ie the coding rate from 8/9 to 3/4 or from 3/4 to 3/5, or reducing the number of states modulation, that is to say from 8 to 4 states of different phases, leads to a decrease in the flow rate for the same frequency band but makes it possible to operate for a much lower signal-to-noise ratio requiring less power or allowing operate with a low C / I of up to +9 dB.

According to the invention, it is more advantageous up to a certain limit to increase the frequency band allocated to the terminals (in particular by multiplying the number of elementary zones) even if it degrades the spectral efficiency. The capacity of the system then obtained is 42% better than the capacity of the typical case in which the minimum C / I on the overall coverage 26 is equal to 15 dB.

It should be noted that the capacity increases significantly for a minimum C / I of less than 13 dB when it is possible to increase the number of beams.

In fact, the Adaptive Coding and Modulation (ACM) mode defined in the DVB-S2 standard requires increases in useful signal power C and / or decreases in the received noise component N + I to go from one configuration to another. modulation and coding to another when the operating point of the system corresponds to a zone of low C / N + I values. In other words, small variations in C / N + I can bring a greater gain in spectral efficiency when the system operates in a zone of low C / N + I values. Thus, it is possible to generate particularly fine beams as proposed with the antenna of the invention.

Following the Figure 3 , the number Nb of sub-bands is equal to 4 and the distribution of the four colors associated with the four frequency sub-bands B (i) is an "optimal" distribution or distribution of four colors in terms of frequency of reuse and C / I minimal.

The distribution of the "four colors" as represented is the "optimal" distribution among the possible distributions of four colors on all beams and therefore all of their footprints on the ground, ie the elementary areas of coverage.

The "optimal" distribution of four colors is optimal in terms of frequency of reuse when the frequency of reuse of each color is substantially the same, that is to say equal to a quarter, edge effects being negligible when the number elementary areas is large enough.

A four-color distribution is said to be "optimal" in terms of C / I when the minimum C / I value over the entire coverage observed for this distribution is a maximum value over all possible four-color distributions. This corresponds to a maximum angular distance between any two beams having the same color, that is to say using the same sub-band.

The spots or footprints of the beams are grouped into elementary clusters of four adjacent spots of different colors following the same geometric pattern or spatial arrangement of the four colors.

Here on the figure 3 only four adjacent clusters 302, 304, 306, 308 repeating the color pattern four times are shown.

The first cluster 302 comprises the four elementary coverage areas 210, 212, 214, 216 operating respectively on the forward downlink 50 in the sub-bands B (4), B (3), B (3), B (1) to which are assigned the colors designated respectively by the letters D, C, B, A.

The second cluster 304 comprises the four elementary coverage areas 218, 220, 222, 224 operating respectively on the forward downlink 50 in the sub-bands B (4), B (3), B (2), B (1) to which are assigned the colors designated respectively by the letters D, C, B, A.

The third cluster 306 comprises the four elementary coverage areas 226, 228, 230, 232 operating respectively on the forward downlink 50 in the sub-bands B (4), B (3), B (2) B (1) to which are assigned the colors designated respectively by the letters D, C, B, A.

The fourth cluster 308 comprises the four elementary coverage areas 234, 236, 238, 240 operating respectively on the forward downlink 50 in the sub-bands B (4), B (3), B (2) B (1) to which are assigned the colors designated respectively by the letters D, C, B, A.

Each elementary coverage area is the footprint of a different image beam, generated only by a single elemental source different from the source-set.

Thus, efficient reuse of frequencies is achieved in which the minimum C / I obtained over the entire coverage is as large as possible over all the laws of affection of the four possible colors.

In the case of a single reflector of diameter equal to 5 meters, the size of the sources is such that all the beams are generated by all the sources located in the same focal plane and that the overflow energy losses are minimal for the set of sources. This corresponds to placing the source centers so as to generate the central rays of each beam of the cover and to choose the rays of the largest possible sources until they come in contact.

Since there is less space to place the sources with a single reflector than with several reflectors, the source sizes corresponding to the single reflector have been reduced compared to the source sizes corresponding to several reflectors, and the corresponding overflow energy losses have increased.

Following the Figures 4 and 5 , the multibeam antenna 54 is shown in greater detail so as to highlight the correspondence between the network 64 of sources 66 and the distribution of the beams on the service coverage 26 according to the elementary zones and the four-color coloring described in FIG. the Figure 3 .

Following the figure 5 the source block 64 or focal network comprises at least one connected set of elementary sources. The elementary sources 66 are here horn type antennas.

Here, only sixteen sources are represented, designated by references 502, 504, 506, 508, 510, 512, 514, 516, 518, 520, 522, 524, 626, 528, 530, 532, 534, 536, 538, 540.

The arrangement of the radio sources in the focal plane is that of a configuration corresponding to the optimized distribution of the subbands for the four colors designated by the letters A, B, C and D.

The sources 502, 504, 506, 508 are arranged side by side in a first row 542. The sources 510, 512, 514, 516 are arranged side by side along a second row 544. The sources 518, 520 522, 524 are arranged next to a third row 544. The sources 526, 528, 530, 532 are arranged side by side in a fourth row.

The four rows 542, 544, 546, 548 are arranged side by side so that the sources 502, 510, 518, 526 form a first column 552 of direction perpendicular to the common direction of the four rows 542, 544, 546, 548.

Similarly, the sources 504, 512, 520, 528 form a second column 554, the sources 506, 514, 522, 530 form a third column 556, the sources 508, 516, 524, 532 form a fourth column 558.

Color A is assigned to sources 502, 506, 518, 522. Color B is assigned to sources 504, 508, 520, 524. Color C is assigned to sources 510, 514, 526, 530. Color D is assigned at sources 512, 516, 528, 532.

The sources 502, 504, 510, 512 correspond respectively to the elementary zones 240, 238, 236, 234 of the fourth cluster 308.

The sources 506, 508, 514, 516 correspond to the elementary zones of the third cluster 306.

The sources 518, 520, 526, 528 correspond to the elementary zones of the second cluster 306.

The sources 506, 508, 514, 516 correspond to the elementary zones of the first cluster 306.

Following the Figures 4 and 6 , the reflector 62 is a reflector with rigid hull foldable or deployable mesh technology (referred to in English "Mesh technology"), adapted to be accommodated on a platform in a transport position in which the assembly formed by the platform and the reflector is contained in the cap of a launcher.

The single reflector 62 is able to be deployed from the carrying position on a platform to a deployment position represented on the Figures 4 and 6 .

Here, the reflector 62 is a portion of a paraboloid P offset from the source block 64 so as to avoid the masking by the source block 64 of the secondary beams, here the beams going down to the coverage area 26.

The paraboloid portion is for example an elliptically shaped cut of the paraboloid. The center of the dish and the focal point of the dish are designated respectively by C _P , and F1, while the cutting center is designated by C _D -Next Figure 6 , the clearance height of the source block 64 with respect to the reflector 62 is designated H. The apparent diameter of the reflector 62, denoted by D, is equal to the size of the projected surface obtained by orthogonal projection of the surface of the reflector in the plane containing C _P and having as normal the axis passing through C _P and the focal point F1.

When the shape of the cut is elliptical, the cutting point C _D is located at a height equal to H + D / 2 with respect to the axis passing through the center C _P and the focal point F1.

The focal length designated by the letter F is equal to the distance between the center of symmetry C _P of the paraboloid portion and the focal point F1 of the paraboloid.

The equivalent focal length, denoted by Feq, is equal to the distance between the cutting center C _D of the paraboloid portion P and the focal point F1 of the paraboloid P.

On the Figure 6 , sectional views are only shown the three elementary sources 502, 510 and 518 and correspondingly the associated elementary zones 240, 236, 224.

As mentioned for the Figure 1 , the angle of angular separation between two adjacent primary beams, shown in Figure 6 by θs1 for the first pair of the sources 501 and 510 and for the second pair of sources 510 and 518, is substantially equal to the angular separation angle between two adjacent secondary beams, shown in FIG. Figure 6 by θs2 for the first pair of corresponding elementary areas 240 and 236 and the second pair of corresponding elementary areas 236 and 224.

Subsequently, θs1 and θs2 will be designated identically by θs.

dans laquelle D_source désigne le diamètre d'ouverture du cornet circulaire formant une source élémentaire de l'ensemble connexe de sources élémentaires.As a first approximation, the reflector can be considered as governed by the laws of geometrical optics and then the size or size of the sources is governed by the following relation: $$D_{sour\mathrm{vs}e}\le Feq*\tan \left({\theta }_{s2}/BDF\right)$$

wherein D _source means the opening diameter of the circular horn forming an elementary source of the related set of elementary sources.

• D_source = Feq ^∗ tan(θ _s2 / BDF) car le diamètre D_source solution de cette équation correspond au cas où le spill-over de la source est le plus faible. Pour une taille de faisceau donnée, c'est la solution permettant de réduire les pertes de spill-over de l'antenne.

Preferably, the _source opening diameter D of the horn satisfies the relationship:

• D _source = Feq ^* tan ( θ _{s 2} / BDF ) because the diameter D _source solution of this equation corresponds to the case where spill-over of the source is the weakest. For a given beam size, this is the solution to reduce spill-over losses of the antenna.

As a variant, the reflector is a paraboloid portion centered on its paraboloidal center of symmetry C _P. The focal plane of the reflector in which the radioelectric sources 66 are arranged is orthogonal to the axis passing through the center of symmetry C _P of the paraboloid and the F1 focal point of the paraboloid. Any elementary source 66 of the source block 64 has an opening size denoted T _source , which verifies the relation $$T_{sour\mathrm{vs}e}\le F*\tan \left({\theta }_{s2}/BDF\right)\mathrm{.}$$

In a variant, the elementary sources are openings having a closed contour of any shape having a size denoted T _source , and corresponding to an equivalent diameter.

The focal length F separating the focal plane 63 and the cutting center 402 (C _D ) of the reflector 62, here is between 4 meters and 7 meters.

However, this results in a high level of energy lost by overflow (called "spill-over") because this effect is mainly related to the use of a single reflector. This results in a significant degradation of the performance of the antenna or its efficiency.

The term representative of the degradation of the efficiency of the antenna by "spill-over" called coefficient of "spill-over" reflects the degree of adequacy of the diagram of the source at the angle under which it sees the reflector and this term is equal to the ratio of the energy effectively intercepted to the total energy radiated by this source.

According to the invention, in the case of a reflector of 5 meters and a focal length equal to 7 meters, the reflector 62 captures only about a quarter of the energy from the sources 66 and the coefficient of spill over is equal to about 0.25, which gives spill losses of between 5 and 6 dB.

Advantageously and unexpectedly, such an antenna configuration makes it possible to increase the capacity of a multimedia system covering a geographical area the size of France.

In fact, such an antenna respects the constraints of carrying the satellite in the launcher and the limited power supply on board the satellite.

Conventionally, solutions using a Beam Forming Network BFN (Beam Forming Network) are known to generate a multibeam coverage using a large and unique reflector and to provide a quality spill over coefficient. . This BFN beamforming network allows to interleave the sources and to illuminate the reflector optimally.

Conventionally, two solutions allow optimal illumination of the reflector.

In a first solution, a "low level" BFN is arranged before the power amplification section of the payload. In this case the number of amplification devices is equal to or even a multiple of the number of sources of the focal network which is itself greater than the number of beams of the cover. Finally the sources have a diameter identical to the image diameter of the beams in the focal plane.

The use of such a "low level" BFN requires a large number of amplifiers greater than the number of beams to be formed on the cover. Therefore the limitations in terms of power consumption and heat dissipation on board current platforms will limit the number of beams on the cover. Thus, the limit of electric power available on board the satellite, results in a lowering of the output power of level higher than the gain obtained by the improvement of the spill over coefficient and the obligation to revise down the number of beams.

In a second solution, a "high level" BFN is arranged after the amplification section of the repeater channels each corresponding to a beam. In this case, the number of amplification devices is equal to the number of beams of the cover. Finally, elementary sources are twice as small as the image diameter of the beam in the focal plane. A disadvantage of this solution is the existence of a minimum diameter of the sources due to the limitation of the focal length of the reflector. With such a solution, the spill over coefficient is of value less than the spill over coefficient of the configuration of the invention namely a single elementary source per beam (SFB solution for Single Feeder per Beam), and this leads to revise the number of beams.

Thus, the known solutions using a single reflector for multibeam covers do not make it possible to benefit from the optimum capacity that can be achieved with reflector diameters greater than 4 meters, in view of the constraints on current launcher loading and on-site power consumption. current platforms.

Thus, accept to degrade the link budget in terms of degradation of the spill-over coefficient and C / I degradation, the spill-over coefficient being between 5 and 6 dB and the C / I being between +9 dB and +23 dB, leads to the solution of the invention namely a single reflector antenna and an SFB-type source assembly to increase the number of beams and the capacity while respecting the carriage constraints of the antenna on conventional launchers and consumption limitations on existing platforms.

Following the Figure 7 , as a variant of the Figure 5 a source block comprises a single connected set of adjacent radioelectric sources formed by horns.

Here, only nine sources are represented, designated by references 602, 604,606,608,610,612,614,616,618.

The arrangement of the radio sources in the focal plane is that of a configuration corresponding to the optimized distribution of the subbands for three colors designated by the letters A, B and C.

The sources 602, 604, 606, respectively the sources 608, 610, 612 and the sources 614, 616, 618 are arranged in a first row, respectively a second row and a third row.

The sources of two consecutive rows are generally shifted by a length equal to a radius of a source, so that for example the sources 602, 604, 610 form an equilateral triangle. This configuration using a mesh or ternary pattern of color distribution in the shape of an equilateral triangle corresponds to an optimal frequency reuse scheme for which the frequency of use of the three colors and the minimal C / I are the largest. the angular coverage generated by all the beams from the sources.

Following the Figure 8 the payload repeater 56 includes an input 602 of the uplink upstream receive antenna 52 through its source 603, a first frequency demultiplexer 604 of signals from two different satellite access stations connected. at the input 602 of the receiving antenna.

The repeater 56 also comprises, for each set of signals received and transmitted by the same access station, a second device for frequency demultiplexing 606 of the signals intended for different downstream beams, here four in number and corresponding to one and the same cluster of elementary zones on four different elementary power output channels.

Here, by way of simplification and by way of example, only one second frequency demultiplexing device 606 has been shown with its four elementary output power channels 608, 610, 612, 614.

Indeed, it is assumed here that the signals intended for the same downstream beam are emitted in the same uplink rising-frequency sub-band, and that the rising-frequency sub-bands associated with the descending beams of the same clusters of elementary zones are juxtaposed to form a frequency band associated with a cluster.

Each elementary output power transmission channel 608, 610, 612, 614 includes an own transposition device 616, 618, 620, 622 followed by an associated output power amplification means 624, 626, 628, 630, capable of delivering the output power to the source of the corresponding beam.

For example, the sources connected to the output terminals of the basic transmission power output channels are the sources of the figure 5 designated 502, 504, 510, 512.

The other elementary sources of the source assembly, like sources 502, 504, 510, 512, are connected to a single and different path of elementary power transmission output. Thus, the repeater is configured to supply each source of the antenna 54 on a single path of clean routing of the downstream traffic and intended for the corresponding elementary zone.

Each output power amplification means 624, 626, 628, 630 is here a Progressive Wave Tube Amplifier (ATOP) operating in Ka-band.

Each ATOP 624, 626, 628, 630 is able to amplify a sub-band or color among the four colors of the second band allocated, each sub-band having a bandwidth of 1450 MHz and able to deliver an output power of 170 W.

Each ATOP is used here on an operating point taken at 3 dB of recoil, the output losses between the output of the ATOP and the input of the source being equal to 2.6 dB.

In general, the transposition devices are configured to provide each elementary output power transmission channel with radio signals in a frequency sub-band B (i) from a predetermined number N of frequency sub-bands forming a band. allocated frequency. Each sub-band B (i) being associated with a color, the frequency transposition means are able to distribute the frequency sub-bands to the output transmission paths and to all the elementary radioelectric sources so that the diagram the ground formed by the colors associated with the different beams generated by the antenna is an optimized frequency reuse N-color diagram, that is to say a diagram for which the angular distance between two beams using the same color is the larger on all possible diagrams.

Following the Figure 9 , the global coverage is divided into 62 elementary zones for which is obtained the largest total capacity on the downward one way.

This maximum total capacity, equal to approximately 100 Gbits / s, is obtained for a tiling of the coverage area into 62 elementary zones, subject to using a frequency reuse factor equal to 4, an electric power available on board the satellite for the payload equal to 12 kW, a minimum permissible C / I equal to 9 dB.

This maximum capacity is reached when the terminals have a G / T factor equal to 16.4 dB / ° K, an antenna gain equal to 40 dB, and use both modulation and adaptive coding defined according to the standard DVB-S2 from ETSI (acronym for European Telecommunication Institute).

In a variant, the telecommunication antenna and the payload are configured to operate in the C band.

In a variant, the antenna functions in reception mode. In this case, the plurality of elementary radioelectric sources 66 is configured to be illuminated by the reflector 62 by electromagnetic radiation in a frequency band according to a primary multibeam ensemble of primary adjacent beams distributed in at least one connected set of adjacent primary beams. any two adjacent primary beams being separated by a first angular separation. The reflector 62 is configured to intercept a portion of the electromagnetic energy transmitted from the geographical zone 26, according to a secondary multibeam set of secondary adjacent reflected beams distributed in at least one connected set of adjacent secondary beams, two adjacent adjacent sub-beams being separated by a second angular separation. The first angular separation and the second angular separation are substantially equal.

Alternatively, the telecommunication antenna is configured to operate in transmission and reception with the same reflector.

In a variant, the reflector is a shaped reflector and the elementary sources forming the source block are arranged in a medium plane with deviations in distances around this average plane, which is a function of the conformation of the reflector.

In a variant, the telecommunication system comprises two satellites configured in a "flying formation". The reflector is mounted on a first satellite while the source block and the payload are mounted on a second satellite.

Claims (10)

A multibeam telecommunication antenna for providing a high-speed telecommunication payload (46) for transmitting and / or receiving a geographical area (26) from a geostationary orbit capable of being mounted mechanically on one or two platforms (40). ) of the satellite (12) and to be electromagnetically coupled to a repeater (56), comprising: at least one radio reflector (62) and an associated source block (64) formed of a plurality of elementary radioelectric sources (66) disposed in a plane (63), the plurality (64) of the elementary radioelectric sources (66) being configured to illuminate the reflector (62) with electromagnetic radiation in a frequency band and / or to be illuminated by electromagnetic radiation in a frequency band reflected by the reflector ( 62) according to a primary multibeam ensemble of adjacent primary beams distributed in at least one connected set of adjacent primary beams, any two adjacent primary beams being separated by a first angular separation θ _S1 ,, the reflector (62) being configured to reflect a portion of the electromagnetic energy emitted by the source block (64) and / or to intercept a portion of the electromagnetic energy emitted from the geographical area (26), according to a secondary multibeam ensemble secondary adjacent reflected beams distributed in at least one connected set of adjacent secondary beams (68), any two adjacent secondary beams being separated by a second angular separation θ _S2 , characterized in that the reflector (62) is unique, and the source block (64) is dimensioned and arranged so that each source is able to generate and / or receive a different single beam and the first angular separation θ _S1 is substantially equal to the second angular separation θ _S2 , and the overflow energy losses associated with each source (66) are between 3 and 10 dB, preferably between 3 and 7.5 dB. Multibeam telecommunication antenna according to Claim 1, characterized in that the reflector (62) is an unconformed reflector, and
the plane (63) in which the radioelectric sources (66) are arranged is a focal plane of the reflector. A multibeam telecommunication antenna according to claim 2, wherein
the reflector is a paraboloid portion centered on its paraboloid center of symmetry C _P ,
the focal plane (63) of the reflector (62) in which the radioelectric sources (66) are arranged is orthogonal to the axis passing through the center of symmetry C _P of the paraboloid and the focal point F1 of the paraboloid,
any source (66) of the source block (64) has an opening size denoted T _source, which verifies the relation
T _source ≤ F ^* tan ( θ _{s 2} ^* (1 + ε ))
in which
F denotes the focal length equal to the distance between the center of symmetry C _P of the paraboloid portion and the focal point F1 of the paraboloid,
Θ s2 denotes the angular separation of two adjacent adjacent beams, and ε is a numerical coefficient between 0 and +0.35. A multibeam telecommunication antenna according to claim 2, wherein
the reflector (62) is a portion of a paraboloid offset from the source block (64) so as to avoid the masking of the secondary beams by the source block (64), and
any source (66) of the source block (64) has an opening size denoted T _source , which verifies the relation
T _source ≤ Feq ^* tan ( θ _{s 2} ^* (1 + ε ))
in which
F _eq denotes an equivalent focal length equal to the distance between a cutting center C _D of the paraboloid portion and the focal point F1 of the paraboloid,
Θ s2 denotes the angular separation of two adjacent adjacent beams, and ε is a numerical coefficient between 0 and +0.35. Multibeam antenna according to one of Claims 2 to 4, in which
the reflector is a portion of a dish, and
the source block (64) comprises at least one set of adjacent radioelectric sources formed of circular opening horns, each horn of the assembly having a _source diameter D including the metal thickness of the wall of the horn, and
the diameter D _source of the opening satisfies the relation: D _source = Feq ^* tan ( θ _{s 2} ^* (1 + ε )) when the reflector (62) is a portion of a paraboloid offset from the source block (64), and the relation D _source = F ^* tan ( θ _{s 2} ^* (1 + ε )) when the reflector is a paraboloid portion centered on its paraboloid center of symmetry C _P , in which
F denotes the focal length equal to the distance between the center of symmetry C _P of the paraboloid portion and the focal point F1 of the paraboloid,
F _eq denotes an equivalent focal length equal to the distance between a cutting center C _D of the paraboloid portion and the focal point F1 of the paraboloid,
Θ s2 denotes the angular separation of two adjacent adjacent beams, and
ε is a numerical coefficient between 0 and +0.35. Antenna according to any one of claims 1 to 5, wherein the source block (64) and the reflector (62) are configured to operate in a frequency band included in the set of C, Ku, Ka bands. A multibeam telecommunication antenna according to any one of claims 1 to 6 wherein the arrangement of the radio sources (66) in the plane (63) is that of a configuration corresponding to an optimized distribution for a number of colors equal to 3, 4, or 7. A multibeam telecommunication antenna according to claim 6, wherein the minimum value on the geographic coverage (26) of the C / I ratio enters, on the one hand, the energy emitted and / or received by the reflector (62) in a secondary beam whatever, and on the other hand the sum of the energies emitted and / or received in the same secondary beam and emitted and / or received by the reflector from the other beams of the same color as the secondary beam, is less than 15 dB, preferably at 12 dB .. Telecommunication payload for transmitting and / or receiving high bitrate data, comprising a transmitting and / or receiving antenna (54) as defined in any one of claims 1 to 7 and a repeater (56), characterized in that
the repeater (56) comprises a set of transmit and / or receive transmission paths (608, 610, 612, 614),
each transmission path (608, 610, 612, 614) comprising
an output and / or radio input terminal (632, 634, 636, 638) connected to a single and different radio source (502, 504, 510, 512) of the source block (64), and
configured to provide radio signals in a sub-band of frequency B (i) out of a predetermined number Nb of frequency sub-bands forming an allocated frequency band, and in that
each sub-band B (i) being associated with a color, the transmission channels are capable of distributing the frequency sub-bands in transmission and / or reception to all the elementary radioelectric sources so that the ground diagram formed by the colors associated with the different secondary beams generated by the antenna (54) is a diagram with Nb optimized frequency reuse colors, that is to say a diagram for which the angular distance between two beams using the same color is the largest on all possible diagrams. Telecommunication system comprising
a telecommunication satellite (12) equipped with a payload defined in claim 9,
an assembly (4) of telecommunication terminals (6, 8, 10) capable of transmitting and / or receiving radio signals to / from the satellite (12),
one or more satellite access stations (18, 19, 20, 21) able to transmit and / or receive radio signals at / from the terminals through the satellite (12) in a forward link (48) and / or backward , characterized in that
each terminal (6, 8, 10) is able to determine the ratio C / I + N observed by its respective antenna and / or by the satellite antenna between, on the one hand, the received energy C associated with the useful radio signal of the terminal and contained in the secondary beam of coverage of the terminal, and secondly, the sum of the energies I received in the same secondary beam but emitted from the other secondary beams of the same color as the source associated with the secondary beam of the terminal cover and energy N of the thermal noise received,
and comprises a received or transmitted rate adaptation device (250, 252, 254) according to the conditions of C / I + N observed, the bit rate being variable by the modification of the number of states of a modulation and / or the coding rate and / or the symbol rate.

Images