EP3086405A1 - Antenna architecture with multiple sources per beam and comprising a modular focal network - Google Patents

Abstract

The MFPB antenna has a plurality of four-port RF sources and a BFN, the number of sources per beam being four, and a single structuring interface plate (30) covering all accesses of the RF sources, and having a plurality of through waveguides (31). The traversing waveguides (31) are arranged in a matrix with several lines and several columns. the RF sources are grouped into sub-assemblies (20, 21, 22) respectively integrated in different independent source blocks (15) mounted next to one another on the front face of the interface plate (30), the accesses RF sources of each source block being connected to the traversing waveguides. The BFN consists of several independent linear partial BFNs, called BFN arrays (BFN1, BFN2, BFN3), mounted side by side on the rear face of the interface plate (30), the different power combiner accesses (23a , 23b) integrated in each BFN strip being connected to the traversing waveguides.

Description

The present invention relates to a multi-source antenna architecture per beam and having a modular focal array. It applies to the field of space applications such as satellite telecommunications and more particularly to MFPB antenna systems (in English: Multiple Feeds Per Beam) embedded on a satellite in order to ensure a mission with multichannel coverage.

In an MFPB antenna with multiple radio RF sources per beam, each beam is formed by combining the accesses of several radio frequency sources of a focal network, each radiofrequency source consisting of a radiating element connected to a radiofrequency transmission and transmission channel. reception usually with two accesses. For this, the RF sources of the focal network are grouped into a plurality of elementary cells having the same number of RF sources and forming a mesh. Depending on the location of the radio frequency sources in the focal network and the number of radiofrequency sources in each mesh, the mesh may have different geometric shapes, for example square or hexagonal. The accesses of the radiofrequency sources of each mesh can then be combined with each other to form a beam. To obtain a good coverage of the beams, it is known to reuse one or more radio frequency sources to form adjacent beams. The reuse of the radio frequency sources is generally carried out according to two dimensions of the space, which conventionally requires the use of a complex BFN beam formation network (Beam Forming Network). power arranged axially, which intersect with each other, and it is then impossible to physically separate the combination circuits dedicated to the formation of different beams. This difficulty is increased by the use of couplers common to several radio frequency sources, which allow the reuse of radio frequency sources and the independence of the beams between them. These antennas can not be built and assembled in modular form and the number of beams that can be formed is limited.

The document FR 2 939 971 describes a particularly compact radiofrequency source, comprising a four-port RF chain, two transmission ports operating respectively in two polarizations P1, P2 orthogonal to each other and two receiving ports respectively operating in the two polarizations P1 and P2. The transmission ports and the reception ports operate respectively in two different frequency bands F1 and F2. This radiofrequency source comprising four independent accesses makes it possible to form two independent beams on transmission and on reception.

The document FR 2,993,716 describes a transmission and reception MFPB antenna architecture comprising a focal network equipped with four-port compact radio frequency sources, in which each beam is developed by a group of four radio frequency sources of the network, combining four same polarization and the same frequency of each of the four radiofrequency sources. This antenna operates on transmission and reception, and two adjacent beams operating in orthogonal polarizations are developed by two groups of different RF sources, each consisting of four radio-frequency sources that can share one or two radio-frequency sources, depending on the arrangement of four RF sources in the mesh. This architecture makes it possible to reuse radiofrequency sources only in one dimension of the space and requires the use of a second identical antenna to obtain a good overlap of the beams in the two dimensions of the space. This antenna architecture is therefore particularly simple since two adjacent beams are made by different access combinations, which allows the use of independent BFNs, each BFN having combination circuits dedicated to the formation of a single beam. However, this document gives no information on a possibility of building the focal network of the antenna in a modular form, nor on the possibility of an assembly of sources and BFN without overlap between the components of different BFN.

The object of the invention is to remedy the problems of known MFPB antennas and to realize a new MFPB antenna architecture whose dimension can be adjusted as required, without limitation, having a completely modular focal network for developing a very a large number of beams, each elementary module being functional and independent of the other modules, the different elementary modules being able to be assembled in a simple manner, on a single joint plane, without any overlap between the components of the different modules, and therefore without any hyperstatic constraint .

For this purpose, the invention relates to a multi-source beam antenna comprising a focal array equipped with a plurality of RF radio frequency sources and a BFN beam forming network, each RF source having a radiating horn connected to an RF chain. transmission and reception, two transmission ports respectively operating in two different polarizations orthogonal to each other and two receiving ports respectively operating in said two different polarizations, the number of RF sources per beam being equal to four. The focal grating and the beamforming network are modular, the RF sources being grouped into subsets respectively integrated into different independent source blocks each having at least four RF sources and the BFN beam forming network. with several independent linear partial BFNs called BFN arrays. The antenna further comprises a single structuring interface plate having a front face on which are mounted the different source blocks, arranged next to each other, and a rear face on which the BFN strips are mounted side by side , the structuring plate comprising a plurality of traversing waveguides opening on the two front and rear faces to which are respectively connected the different accesses of the RF sources of each source block and secondly, corresponding accesses of the Linear partial BFNs, the corresponding accesses of the RF sources and the partial BFNs being connected to one another via the traversing waveguides of the interface plate.

Advantageously, each block of sources may consist of a stack of several planar layers, each planar layer consisting of two complementary metal half-shells assembled together, the two half-shells of each planar layer integrating radio frequency components of the RF channels. of all the RF sources of the source block, each RF chain being connected to a corresponding radiating horn.

Advantageously, the traversing waveguides of the interface plate may respectively be arranged in a matrix with several rows and several columns and the transmission and reception ports of the RF channels may all have the same orientation.

Advantageously, the adjacent RF sources in the focal network have transmission ports and reception ports respectively connected four by four by the power combiners integrated in the BFN bars, two groups of four consecutive sources in the focal network sharing two sources in a single focal network direction and the BFN arrays extend parallel to said focal network direction corresponding to the source sharing.

Advantageously, the interface plate may comprise, at the periphery of the focal network, available through waveguides connected to transmission and reception ports of RF sources but not connected to accesses of a BFN strip, the available through waveguides having a carbon-containing absorbent material.

• figure 1 : un schéma, en coupe transversale, d'un exemple de réseau focal modulaire, selon l'invention ;
• figures 2a et 2b: deux schémas en perspective et en vue de dessous, illustrant, respectivement, un exemple de sources RF à quatre accès, et un exemple de disposition des quatre accès, selon l'invention ;
• figure 3a : un schéma, en perspective, d'un exemple de bloc de sources, selon l'invention ;
• figures 3b et 3c : deux schémas, en vue de dessous, de deux exemples d'arrangement des accès du bloc de sources de la figure 3a, selon l'invention ;
• figure 4 : un schéma illustrant un arrangement des trous traversants débouchant sur les faces avant et arrière d'une plaque d'interface structurante, selon l'invention ;
• figure 5a : un schéma, en vue partielle de dessous, illustrant un exemple de position des barrettes de BFN partiels et les différents groupes d'accès combinés sur une plaque d'interface structurante, selon l'invention ;
• figure 5b: une vue de détail de deux groupes de sources adjacents partageant deux sources RF avec la combinaison des accès pour la formation de deux faisceaux d'émission et de deux faisceaux de réception, selon l'invention ;
• figure 6 : un schéma en perspective, d'un exemple d'aménagement des barrettes de BFN partiels, sur la plaque d'interface structurante, selon l'invention.

Other features and advantages of the invention will become clear in the following description given by way of purely illustrative and non-limiting example, with reference to the attached schematic drawings which represent:

• figure 1 : a diagram, in cross section, of an example of a modular focal array, according to the invention;
• Figures 2a and 2b two diagrams in perspective and in view from below, illustrating, respectively, an example of RF sources with four accesses, and an example of arrangement of the four accesses, according to the invention;
• figure 3a : a diagram, in perspective, of an example of source block, according to the invention;
• Figures 3b and 3c : two diagrams, seen from below, of two examples of arrangement of the accesses of the source block of the figure 3a according to the invention;
• figure 4 : a diagram illustrating an arrangement of the through holes opening on the front and rear faces of a structuring interface plate, according to the invention;
• figure 5a : a diagram, in partial view from below, illustrating an example of position of the partial BFN bars and the different access groups combined on a structuring interface plate, according to the invention;
• figure 5b : a detail view of two groups of adjacent sources sharing two RF sources with the combination of accesses for the formation of two transmit beams and two receive beams, according to the invention;
• figure 6 : a perspective diagram, of an example of arrangement of the partial BFN bars, on the structuring interface plate, according to the invention.

The invention relates to an antenna architecture operating on transmission and reception. The formation of the beams is therefore carried out in the two transmission and reception frequency bands. However, to obtain a good coverage of the beams in the two directions of space, it is necessary to use two antennas dedicated to the two frequency bands, the two antennas having an identical architecture. The remainder of the description is limited to a single antenna operating in transmission and reception.

The figure 1 is a cross-sectional diagram, illustrating an example of a modular focal array, according to the invention. The focal network comprises a plurality of source blocks, a plurality of beamforming subareas, BFN1, BFN2, BFN3, called partial BFNs, and a structuring interface plate 30 covering all access to RF sources. Each source block has a subset of several RF radio sources, with fully integrated Tx transmit and receive Rx channels. All source blocks 15 comprise an identical number of N RF sources, where N is an integer greater than or equal to four, arranged in a matrix comprising at least two lines and at least two columns. By way of non-limiting example, the figure 3a illustrates a source block with eight RF sources arranged in four rows and two columns. According to the invention, as shown in Figures 2a and 2b each RF source comprises a radiating horn 10 connected to an RF chain 11 provided with four transmission or reception ports Tx1, Tx2, Rx1, Rx2, the RF chain being able, for example, to be similar to that described in the document FR 2,993,716 . Each RF chain has an OMT diplexant orthomode transducer and filters. The formation of the circular polarization is provided by couplers and / or by a polarizer for the Rx receive ports. Alternatively, the RF chain can be designed to operate in linear polarization. Advantageously, so that each source block is as compact as possible, the various RF chains can be manufactured in two complementary parts, called half-shells, by a known machining process, the two half-shells then being assembled together by any type of connection known, conventionally by screws, or alternatively, by welding, or by gluing.

Advantageously, all RF channels integrated in the same source block can be machined together, next to each other, in metal half-shells common to all RF sources of the source block. In this case, the assembly of a source block consists in assembling the half-shells two by two, then stacking the shells assembled in different planar layers 16, 17, and finally, stacking and assembling additional planar layers 18 containing the couplers and the axial polarizers. The manufacture of all radio frequency components by machining metal parts common to all RF sources, provides a very high robustness of each RF chain vis-à-vis performance dispersions related to the manufacture of components. Indeed, all the components corresponding to the same frequency band being located in the same physical layer, all the electrical paths dedicated to the two polarizations of each RF chain are symmetrical and thus induce the same phase dispersion.

Each block of sources then has the advantage of having a planar multilayer architecture comprising a first stage consisting of radiating elements, for example turbinators, a second stage comprising the RF chains connected to the different horns, and three stages integrating couplers and couplers. axial polarizers.

As depicted on the two illustrated schemes, in bottom views, on the Figures 3b and 3c the four transmission accesses Tx1, Tx2 and reception Rx1, Rx2 of each RF source are arranged side by side on the rear face of the source block 15. The accesses corresponding to different RF sources are oriented parallel to each other and are arranged according to a matrix, in the same arrangement of rows and columns as the radiating horns of the corresponding RF sources, for example four rows and two columns in the case of Figures 3a, 3b and 3c . The only difference between the two arrangements represented on the Figures 3b and 3c relates to the direction of access that can be made in a direction X corresponding to the direction of the lines, or in a direction Y corresponding to the direction of the columns, the X and Y directions can be orthogonal in the case of a mesh square as depicted on the Figures 3b and 3c , or be oriented at 30 ° or 60 ° in the case of a hexagonal mesh as shown in figures 5a and 5b . In the arrangement shown on the figure 3b in each line, for all RF sources, the accesses corresponding to the same frequency and to the same polarization are arranged in the same order and are therefore aligned with each other. In the arrangement shown on the figure 3c in each column, for all RF sources, the accesses corresponding to the same frequency and to the same polarization are arranged in the same order and are therefore aligned with each other. Of course, the denominations "line" and "column" are arbitrary and can be inverted without the invention being modified.

The different accesses of the integrated RF sources in each source block 15 are intended to be connected to traversing waveguides 31 corresponding, open at their two opposite ends, arranged in the structuring interface plate 30 common to all the source blocks 15 of the focal network of the antenna. The structuring interface plate 30 has dimensions that correspond to the dimensions of said focal network and therefore covers the entire surface of the focal network. The structuring interface plate 30 comprises at least as many passing waveguides 31 as there is access to RF sources to be connected, the traversing waveguides opening on two opposite faces, respectively front and rear, of the structuring interface plate. The arrangement of the traversing waveguides is identical to the access block layout of the source blocks as shown in FIG. figure 4 . Thus, all the source blocks 15 are mounted side-by-side on a front face of the structuring interface plate, without any overlap between them, and all the accesses of the RF sources integrated in the source blocks are connected to waveguides. respective through-wavelengths integrated in the structuring interface plate.

As shown on figures 5a and 5b each beam is elaborated by a group 20, 21, 22 of four RF sources of the focal network, the four RF sources being arranged in a two-line and two-column matrix, by combining, via the passing waveguides 31 of the interface plate 30, the access of the same polarization and the same frequency of each of the four RF sources. In each group of four RF sources, only one of the transmission ports, for example Tx1, and only one of the reception ports, for example Rx1, of each RF source are combined with the corresponding accesses of the other three RF sources of the group by dedicated power combiners 23a, 23b. Thus, with each group of four RF sources are developed a transmission beam and a receiving beam. Since each RF source has two transmit ports and two receive ports, there remains one available Tx2 transmit port and one Rx2 receive port that can be used to form another transmit beam and another receive beam with RF sources from another adjacent group.

Two adjacent beams operating in orthogonal polarizations are developed by two groups of adjacent RF sources, each consisting of four RF sources. The combined accesses in the two adjacent groups 20, 21 have the same frequency but polarizations different. For this, in transmission and reception, the second available access is combined with corresponding accesses of a group of four adjacent RF sources. According to a direction of the focal network, for example in the X direction, the two adjacent groups 20, 21 have two sources in common and therefore share two RF sources among the four. In the other direction, for example the Y direction, no RF source is shared between the adjacent source groups 20, 22. The reuse of two RF sources among the four is therefore performed in a single direction of the focal network.

Since there is a sharing of sources only in one direction of the focal network, the formation of the different beams can be achieved by using linear partial BFNs, independent and without any overlap between them, each partial BFN, BFN1, BFN2, BFN3, being dedicated the formation of a beam line. The partial BFNs extend in the direction of the focal network corresponding to the direction where there is a sharing of sources between the adjacent groups, that is to say in the X direction in our example. Each partial BFN can then be manufactured in a modular form, called a BFN strip, each BFN strip including all the power combiners 23a, 23b needed to combine the RF source accesses, four by four, for the formation of a line of beams. The BFN strip extends parallel to the access lines to be combined, has a width corresponding to the width of two access columns of the focal network and has a length corresponding to the length of a line of the focal network. The focal array comprises a partial BFN per line of beams to be formed. Each strip of BFN comprises a front face provided with two input access lines arranged in a matrix identical to that of two lines of crossing waveguides 31 of the interface plate 30 structuring and comprises a rear face provided with two beam output ports, respectively transmission and reception, group of four RF sources. Thus, as shown in the diagram of the figure 6 , all the partial BFN bars, BFN1, BFN2, BFN3, are mounted side by side on a rear face of the structuring interface plate 30, without any overlap between them, and all the input ports of the partial BFNs are connected to respective through waveguides integrated in the structuring interface plate. Like every waveguide through is connected to an access of an RF source belonging to a source block 15 mounted on the front face of the structuring interface plate 30, the input ports of each partial BFN are connected to respective accesses of the RF sources integrated in the source blocks via the traversing waveguides of the structuring interface plate. At the periphery of the focal network, there may be some available waveguides 19 which are connected to accesses of the RF sources but which are not used for the formation of the beams and thus not connected to the accesses of a partial BFN . In this case, to absorb the RF energy radiated by the accesses of the RF sources, unused, an absorbent material is inserted locally in the available through waveguides of the structuring interface plate to which are connected the unused access. Advantageously, the absorbent material contains carbon, such as, for example, silicon carbide.

This antenna architecture makes it possible to reuse radiofrequency sources in only one dimension of the space and requires the use of a second identical antenna to obtain a good overlap of the beams in the two dimensions of the space. This antenna architecture is therefore particularly simple since two adjacent beams are made by different access combinations, without using couplers, which allows the use of independent power combiners dedicated to the formation of a single beam.

The structuring interface plate provides support, assembly and interconnections between all source blocks and all partial BFNs on a single joint plane and allows a total decoupling between the different RF sources integrated in the elementary source blocks mounted on its front face and the various partial BFN mounted on its rear face. Unlike conventional antenna architectures, the number of integrated RF channels in each source block is not fixed and can be adapted as desired depending on the shape of the cover to be made. Moreover, it is possible to incorporate twisted through waveguides (in English: twisted) in the structuring interface plate. The structuring interface plate makes it possible to connect RF channels and BFN having waveguides of different sections as well as waveguides with different orientations, which simplifies the design of BFN. The orientation of the accesses of the RF chains being identical for all the RF sources, it makes it possible to facilitate the routing of the power combiners within the BFNs in a plane parallel to the focal network, without overlap between the BFN and to reduce the congestion of each RF source and mesh size of the focal network.

Although the invention has been described in connection with particular embodiments, it is obvious that it is not limited thereto and that it includes all the technical equivalents of the means described and their combinations if they are within the scope of the invention.

Claims (5)

A plurality of beam source antennas having a focal array provided with a plurality of RF radio frequency sources and a BFN beam forming network, each RF source having a radiating horn (10) connected to an RF chain (11) of transmission and reception, two transmission ports (Tx1, Tx2) respectively operating in two different polarizations orthogonal to each other and two reception ports (Rx1, Rx2) respectively operating in said two different polarizations, the number of RF sources per beam being equal to four, characterized in that the focal grating and the beam forming network are modular, the RF sources being grouped into subsets respectively integrated in different independently independent blocks of sources (15), each comprising at least four RF sources and the BFN beam forming network having a plurality of independent linear partial BFNs (BFN1, BFN2, B FN3), called BFN strips, and in that it further comprises a single structuring interface plate (30) having a front face on which are mounted the different source blocks (15) arranged next to each other. others, and a rear face on which the bars of BFN are mounted side by side, the structuring plate having a plurality of traversing waveguides (31) opening on the two front and rear faces which are respectively connected on the one hand the different accesses of the RF sources of each source block and secondly, corresponding accesses of the linear partial BFNs, the corresponding accesses of the RF sources and the partial BFNs being connected to one another via the traversing waveguides (31). ) of the interface plate (30). Antenna according to claim 1, characterized in that each source block (15) consists of a stack of several planar layers (16, 17, 18), each planar layer consisting of two complementary metal half-shells assembled together. , the two half-shells of each planar layer integrating radiofrequency components of RF channels (11) of all RF sources of the source block, each RF chain being connected to a corresponding radiating horn (10). Antenna according to Claim 2, characterized in that the traversing waveguides (31) of the interface plate (30) are respectively arranged in a multi-line matrix and in a plurality of columns and in that the transmission and RF channel reception (11) all have the same orientation. Antenna according to one of the preceding claims, characterized in that the adjacent RF sources in the focal network have transmission ports and reception ports respectively connected four by four by power combiners (23a, 23b) integrated in the BFN arrays (BFN1, BFN2, BFN3), two groups (20, 21) of four consecutive sources in the focal network sharing two sources in common in only one direction of the focal network and in that the BFN arrays extend in parallel to said direction of the focal network corresponding to the sharing of sources. Antenna according to claim 4, characterized in that the interface plate (30) comprises, on the periphery of the focal grating, available through waveguides (19), connected to RF source transmission and reception ports. but not connected to accesses of a BFN strip, said available through waveguides (19) having a carbon-containing absorbent material.

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