EP3086409B1 - Structural antenna module including elementary radiating sources with individual orientation, radiating panel, radiating network and multibeam antenna comprising at least one such module - Google Patents

Description

The present invention relates to an antenna structural module integrating elementary radiating sources with individual orientation, a radiating panel comprising a structural module, a radiating array comprising several radiating panels and a multibeam antenna comprising at least one structural module. It applies to the space domain such as satellite telecommunications and more particularly to multibeam antennas comprising a network of several radiating sources placed in the focal plane of a reflector.

A radiating source consists of a radiating element, for example a horn, connected to a radio frequency (RF) chain. An example of an RF chain is described in the document EP2202839 . The RF chain comprises RF components making it possible to pass from a guided propagation mode of the electromagnetic waves to a radiated mode and performs for each beam, the transmission and reception functions in a particular frequency band, for example the Ka band . The transmission and reception functions can be performed in mono-polarization to cover the needs of the users or in bi-polarization to ensure links to terrestrial anchoring stations (in English: gateway).

In multibeam antenna architectures, several independent elementary radiating sources are assembled in a network placed in the focal plane of a reflector, as described for example in documents JP 2008131575 and JP S62 203401 . The assembly of the different radiating sources is complex because it often requires maintaining the radiating sources with a specific orientation making it possible to limit the phase aberrations linked to the defocusing of the horn relative to the center of the reflector and to maximize the performance of the antenna. for each beam. Each radiating source is assembled on a mechanical support by an interface specific to each horn. This individual assembly of each source requires individually managing the interface of each RF chain and the adjustment of the orientation of each horn, which does not allow the production of RF chains to be pooled because their RF axes are not parallel to each other. The individual management of each source therefore presents a significant cost.

To facilitate the individual orientation of each radiating source, as shown in the figure 1 , it is known to fix the radiating sources individually on a structural plate 13 in which are distributed distribution wave guides 14 intended to route RF signals between the radiating source and input / output ports of a RF signal processing. The distribution waveguides are connected to outputs of the RF chains 10 by flexible waveguides 15 allowing the individual orientation of each radiating source. The structural plate 13 then ensures the routing of the distribution waveguides 14 as well as the support and the orientation of the RF chains relative to the reflector of the multibeam antenna. However, this solution requires an assembly of the RF chains independently of each other, an individual orientation of each RF chain and the associated horn, and requires the use of numerous flexible waveguides of orientation inducing additional ohmic losses and a additional thermal power to be dissipated. In addition, this solution is only possible when the sources of the focal network are sufficiently spaced from one another to allow the routing of the distribution waveguides between the RF chains supported by the structural plate.

To our knowledge, there is to date no structural antenna module comprising a set of radiating sources whose RF chains are completely integrated in a common support, and authorizing the individual orientation of the radiating horns.

A first aim of the invention is to remedy the drawbacks of the networks of known radiating sources, and to produce an antenna structural module in which the RF axes of the RF chains of all the radiating sources are arranged in the same plane and in which the orientation of the radiant horns is ensured without modifying the orientation of the RF chain axes.

A second object of the invention is to produce an antenna structural module comprising several radiating sources integrated in a monobloc assembly.

For this, the invention, as defined in the only independent claim 1, relates to an antenna structural module integrating elementary radiating sources, each radiating source comprising a radiofrequency chain connected to a radiating horn. The RF chain comprises a main waveguide having a longitudinal axis disposed perpendicularly to an XY plane, an OMT orthomode transducer comprising two transverse branches orthogonal to each other, located parallel to the XY plane and coupled perpendicularly to the main waveguide by slots of coupling. The radiating horn is coupled to a terminal end of the main waveguide by means of a bent orientation ring intended to orient the radiating horn in a desired direction different from the longitudinal axis of the main waveguide, the elbow of the orientation ring being placed in a plane of symmetry of the RF chain, the plane of symmetry being orthogonal to the XY plane and containing the bisector of the angle formed by the two transverse branches.

Advantageously, the structural module can also comprise a support plate common to all the radiating sources, the RF chains being completely integrated in the support plate.

Advantageously, the orientation ring associated with each radiating horn can be housed in a dedicated opening arranged in a front face of the support plate. Alternatively, the terminal end of the main waveguide of each RF chain can be housed in a dedicated opening arranged in a front face of the support plate and the orientation ring associated with each radiating horn can be fixed on one side. front of the support plate, in line with the corresponding terminal end.

Advantageously, the orientation ring of each radiating source can be made up of three parts integral with each other, the three parts being made up of two rigid access waveguides having different longitudinal axes and intended to be respectively connected to a horn. radiating and to an RF chain, and a waveguide section adapter located between the two access waveguides, the adapter waveguide section forming the bend of the orientation ring.

Alternatively, the orientation ring may include a coupling iris.

The invention also relates to a radiant panel comprising a structural module.

Advantageously, the radiating sources can be machined in a matrix in a common support plate and can comprise respective supply and output wave guides, routed in the common support plate and respectively connected to input and exit grouped next to each other on the radiant panel.

The invention also relates to a radiating network comprising at least one radiating panel.

Advantageously, the radiating network can comprise several radiating panels, orientable independently of each other.

The invention also relates to a multibeam antenna comprising at least one radiating array.

• figure 1 : un schéma en coupe d'un exemple de réseau de sources rayonnantes, selon l'art antérieur ;
• figure 2 : un schéma en coupe transversale d'un exemple de module structural d'antenne intégrant des sources rayonnantes élémentaires à orientation individuelle, selon l'invention ;
• figure 3 : un schéma illustrant un exemple de plusieurs chaînes RF montées parallèlement entre elles sur deux étages, selon l'invention ;
• figure 4 : trois schémas illustrant respectivement, selon deux plans différents et selon une vue en transparence, un premier exemple de bague d'orientation coudée, selon l'invention ;
• figure 5 : un schéma illustrant, selon une vue en transparence, un deuxième exemple de bague d'orientation coudée, selon l'invention ;
• figure 6a : un schéma en coupe transversale illustrant la structure interne d'un premier exemple de chaîne RF planaire, selon l'invention ;
• figure 6b : un schéma en coupe transversale illustrant un exemple d'OMT dissymétrique, selon l'invention ;
• figures 7a et 7b : deux vues illustrant la structure interne de l'étage supérieur, respectivement de l'étage inférieur, de deux chaînes RF empilées, selon l'invention ;
• figure 8a : un schéma en vue de dessus, illustrant un exemple de réseau rayonnant sectorisé en plusieurs panneaux rayonnants indépendants, selon l'invention ;
• figure 8b : un schéma illustrant un exemple d'implantation des sources rayonnantes et des accès d'entrée et de sortie sur les panneaux rayonnants de la figure 8a, selon l'invention ;
• figure 8c : un schéma illustrant un exemple de découpe des plaques de support de chaque panneau rayonnant d'un réseau rayonnant sectorisé, selon l'invention ;
• figure 9 : un exemple d'antenne multifaisceaux, selon l'invention.

Other features and advantages of the invention will appear clearly in the following description given by way of purely illustrative and nonlimiting example, with reference to the appended schematic drawings which represent:

• figure 1 : a sectional diagram of an example of a network of radiating sources, according to the prior art;
• figure 2 : a diagram in cross section of an example of an antenna structural module integrating elementary radiating sources with individual orientation, according to the invention;
• figure 3 : a diagram illustrating an example of several RF chains mounted parallel to each other on two stages, according to the invention;
• figure 4 : three diagrams respectively illustrating, in two different planes and in a transparent view, a first example of a bent orientation ring, according to the invention;
• figure 5 : a diagram illustrating, in a transparent view, a second example of a bent orientation ring, according to the invention;
• figure 6a : a diagram in cross section illustrating the internal structure of a first example of a planar RF chain, according to the invention;
• figure 6b : a diagram in cross section illustrating an example of asymmetrical OMT, according to the invention;
• Figures 7a and 7b : two views illustrating the internal structure of the upper stage, respectively of the lower stage, of two stacked RF chains, according to the invention;
• figure 8a : a diagram in top view, illustrating an example of a radiating network segmented into several independent radiating panels, according to the invention;
• figure 8b : a diagram illustrating an example of installation of the radiating sources and the entry and exit accesses on the radiating panels of the figure 8a , according to the invention;
• figure 8c : a diagram illustrating an example of cutting the support plates of each radiating panel of a sectored radiating network, according to the invention;
• figure 9 : an example of a multibeam antenna according to the invention.

The figure 2 illustrates an example of an antenna structural module integrating elementary radiating sources with individual orientation, according to the invention, and the figure 3 illustrates an example of arrangement of several RF channels parallel to each other. Each radiating source comprises an RF radio frequency chain 10 comprising a main waveguide 31, visible on the figure 3 , and a radiating horn 16 coupled to the waveguide main 31. According to the invention, each radiating source further comprises a bent orientation ring 18 connected to a terminal end 5 of the main waveguide 31 of the corresponding RF chain 10 and coupled to the radiating horn 16, the ring d angled orientation being intended to orient the radiating horn in a desired direction, different from the direction of orientation of the main waveguide 31 of the RF chain. Each orientation ring 18 has an elbow having an opening angle, the value of which is defined individually as a function of the individual orientation desired for the associated radiating horn. The orientation of each horn is achieved by the dedicated orientation ring 18 by individually adjusting, for each horn, the opening angle of the elbow of the corresponding orientation ring. The RF chains can be respectively mounted in the cavities of a support plate 17 common to all the radiating sources or completely integrated in the support plate as shown in the figure 2 . Advantageously, the orientation ring associated with a horn can be fixed on a front face 19 of the support plate 17 or can be housed in a dedicated opening of the front face 19 of the support plate 17. In the case where the ring d orientation associated with a horn is fixed on the front face 19 of the support plate 17, the terminal end 5 of the main waveguide 31 of the corresponding RF chain is housed in a dedicated opening arranged in the front face of the plate support 17 so as to be able to ensure the continuity of the connection between the main waveguide 31 and the orientation ring 18. The angled orientation ring makes it possible to get rid of all the flexible cables and makes it possible to pool the assembly of all RF channels in a single common support. The RF chains can then be fitted under the common support or be machined in the common support parallel to each other as shown for example on the figure 3 in which the common support has been omitted and in which the RF chains 10a, 10b, 10c comprise two different stages 36, 37 for dual-frequency operation.

As shown in the example of the figure 4 , each bent orientation ring can be made up of three parts integral with each other, the three parts being made up of two access waveguides 21, 22, intended to be connected respectively to a radiating horn and to a RF chain, and an adaptation waveguide section 20 located between the two access waveguides 21, 22 and forming a coupling iris between the two access waveguides. The two access waveguides 21, 22 can for example be of circular or square section. The access waveguide 22 can be connected to the radiating horn and the access waveguide 21 can be connected to the main waveguide 31 of the RF chain, the two access waveguides having respective axes oriented in different directions. The two access waveguides 21, 22 and the adaptation waveguide section 20 form a bent assembly, the elbow having a vertex 27 situated on the adaptation waveguide section 20 and a opening angle Θ, the value of which is predefined individually for each horn so as to tilt the axis 23 of the access waveguide 22 connected to the horn relative to the axis 24 of the access waveguide 21 connected to the RF chain in the desired direction. This makes it possible to orient the radiating horn relative to the support plate 17 and therefore to orient the direction of radiation of the horn, this direction of radiation corresponding to the axis 23. The angle of inclination α of the axis 23 relative to the axis 24 is between zero and a few degrees, its value being defined according to the location of the horn on the support plate and therefore according to its location relative to the focal point of the radiating network of an antenna fitted with a reflector. The opening angle Θ of the elbow depends on the position Δ (x, y) of the radiating source in the network and on the equivalent focal length Fe of the antenna, according to the following relation: $$\mathrm{\Theta }=\arctan \left(\mathrm{\Delta }\left(\mathrm{x},\mathrm{y}\right)/\mathrm{Fe}\right)$$

Each angled orientation ring therefore makes it possible to orient a radiating horn relative to the support plate and therefore to correctly orient said radiating horn relative to a reflector of a multibeam antenna. The angled orientation ring can be produced by machining the waveguides 21, 22, 20 in the mass in the form of two complementary half-shells which are assembled by any known technique to reconstitute complete waveguides.

Alternatively, as shown in the figure 5 , the angled orientation ring can be made in a single part in a room monobloc for example using a 3D printer. In this case, the angled orientation ring is a piece of flexible strand, for example a cylinder or a flexible pipe, which makes it possible to reach greater angles of inclination of the horn.

The figure 6a illustrates a diagram in cross section of an example of planar RF chain operating in a single frequency band, according to the invention. The RF chain, produced in waveguide technology, comprises a main waveguide 31 having a longitudinal axis arranged perpendicular to the XY plane, an OMT orthomode transducer 30, radio frequency components of the coupler 33 and filter 32 type operating in bipolarization and input / output ports 34, 35 respectively dedicated to the two polarizations. The input / output ports can be linear or circular polarization. The OMT can be symmetrical and have four transverse branches or alternatively, be asymmetrical and have two transverse branches orthogonal to each other. On the example of the figure 6a , the OMT comprises an axial excitation input coupled to the main waveguide 31 and two transverse branches 41, 42, orthogonal to each other, located in the XY plane and coupled perpendicular to the main waveguide 31 by two slots coupling not shown. The two coupling slots are arranged in the wall of the main waveguide 31 and are angularly spaced by an angle 26 equal to 90 °. The transverse branches of the OMT are connected to the radiofrequency components 32, 33. The main waveguide 31 has an upper end intended to be connected to a radiating horn 16 via the bent ring 18. The RF components, of the coupler 33 and filter 32 type, are dedicated to processing the RF signals corresponding to the same frequency band. The OMT feeds the horn (in transmission), or is supplied by the horn (in reception), selectively either with a first electromagnetic mode having a first linear polarization, or with a second electromagnetic mode having a second linear polarization orthogonal to the first . The first and second polarizations are associated with two components of electrical fields Ex, Ey whose orientation is imposed by the orientation of the RF chains located in the XY plane and therefore by the position of the two coupling slots. the orientation of the Ex field is parallel to the waveguide of the transverse branch 42, the orientation of the field Ey is parallel to the waveguide of the transverse branch 41.

The Figures 7a and 7b illustrate two views of an example of two stacked planar RF chains allowing operation in two different frequency bands, according to the invention. For operation in several different frequency bands, for example two frequency bands respectively dedicated to transmission and reception, it is possible to stack several different RF chains, respectively dedicated to each frequency band, in planar layers different. In this case, the structure of the RF chain of each radiating source therefore comprises at least two different stages, respectively upper 36 and lower 37, stacked one above the other and respectively dedicated to the receiving frequency band. and the transmission frequency band of the radiofrequency signals. Each radiofrequency stage is arranged perpendicular to the longitudinal axis of the main waveguide 31 of the RF chain.

On the Figures 7a and 7b , the OMT 30 coupled to the main axial waveguide 31 common to all the transmission and reception signals is the same as on the figure 6a and has two transverse branches per stage, but this is not essential, an OMT with four transverse branches can also be used. The upper transverse branches 41, 42 connected to the radiofrequency components of the upper RF stage 36, can be dedicated to receiving RF signals and the two lower transverse branches 43, 44 connected to the radiofrequency components of the lower RF stage 37, can be dedicated to the transmission of RF signals. The axial main waveguide 31 is machined in the thickness of the two planar layers constituting the upper and lower stages, and is coupled on the one hand to the upper transverse branches 41, 42 of the OMT by first axial coupling slots and on the other hand to the lower transverse branches 43, 44 of the OMT by second axial coupling slots. The first axial coupling slots are located at the same first height in the wall of the axial waveguide and angularly spaced at an angle equal to 90 ° and respectively, the second axial coupling slots are located at the same second height in the wall of the axial waveguide and spaced angularly by an angle equal to 90 °. The first height corresponds to the upper stage of the RF chain and the second height corresponds to the lower stage of the RF chain. To reduce the size of the RF chain, the first axial slots can be aligned above the second axial slots, but this is not essential, they can also be offset angularly with respect to each other.

Advantageously, in the case where operation in several frequency bands is desired, it suffices to increase the number of stages of the RF chain, each stage being dedicated to one of the desired frequency bands.

Each RF chain can for example be manufactured in two complementary parts, called half-shells, by a known machining process, the two metal half-shells then being assembled together by any type of known connection, welding, glue, screws. The radiofrequency components are then formed by grooves machined in the two metal half-shells.

In the case of an application in the telecommunications field, the asymmetry of the angled orientation ring has no impact on the performance of the radiating sources because the main excitation input waveguide at which is connected the radiating horn is dimensioned to allow only one propagation mode to propagate corresponding to the fundamental mode. Consequently, all the other modes, and in particular the modes with odd symmetry generated by the asymmetry of the angled orientation ring can potentially be eliminated by traps placed at the input of the excitation assembly.

In order not to affect the radiation characteristics of the radiating source thus produced, the elbow of the orientation ring 18 must be placed in a plane of symmetry of the RF chain, with respect to the components Ex, Ey of main field generated in the main axial waveguide 31 by the OMT. Indeed, in the absence of respect for the plane of symmetry, the elbow will be seen as a different defect by the two transverse branches of the RF chain and by the two coupling slots spaced angularly by 90 °, which will have the consequence of deteriorate the purity of the polarization. The mounting of the orientation ring 18 relative to the RF chain must therefore be made taking into account the orientation of the two main orthogonal fields Ex, Ey generated in the axial main waveguide 31 of the RF chain. Compared to the two main orthogonal fields Ex, Ey, the plane of symmetry is the plane containing the bisector of the angle formed by the directions of orientation of the two main fields Ex and Ey. The elbow must therefore be positioned in this plane of symmetry so as to be seen with the same phase by the two coupling slots of the planar RF chain and so that the radio frequency discontinuity generated by the elbow causes the same impact on the two components of fundamental mode field. On the diagram of the figure 6a , the only possible plane of symmetry is the plane perpendicular to the XY plane containing the bisector 25 of the angle formed by the two directions of the orthogonal field components Ex and Ey, i.e. the angle separating the two coupling slots of the OMT, or of the angle 26 formed by the two transverse branches 41, 42. The apex 27 (visible on the figure 4 ) of the elbow of the orientation ring 18 is therefore placed in a plane orthogonal to the XY plane and containing the bisector 25 of the angle 26 separating the two orthogonal coupling slots, that is to say the angle 26 formed by the two transverse branches 41, 42. In the case of an OMT with four transverse branches, there are four coupling slots regularly spaced angularly. The bisector 25 then corresponds to that of the angle separating two consecutive orthogonal coupling slots, that is to say the bisector of the angle situated between two consecutive orthogonal transverse branches.

The RF chain described in connection with figures 6a , 7a, 7b , has the advantage of having an architecture, monolayer or multilayer, completely planar, all the radiofrequency components corresponding to the same frequency band being manufactured by machining in the form of two metal half-shells stacked and assembled together. The manufacture of all the radiofrequency components by machining provides a very high robustness of the RF chain with respect to the performance dispersions linked to the manufacture of the 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 therefore induce the same phase dispersion. In addition, milling, which is the only machining mode suitable for manufacturing half-shells, guarantees excellent surface finish and allows the deposition of a silver coating on the machined parts to allow reduction ohmic losses of about 30%.

In the case of operation in several different frequency bands, the multilayer structure of the RF chain forms a multi-band, bipolarization, very compact, very low cost assembly which is compatible with installation in a network of radiating sources. with reduced mesh and which can be integrated into a support plate common to several RF chains as shown in the figure 2 . The input / output ports 34, 35, 38, 39 of the RF chain can be oriented on the sides, as on the Figures 7a, 7b , or forward or backward, as required.

As shown in the examples of Figures 8a and 8b , this architecture also allows the manufacture of a radiating network segmented into several radiating panels 50a, 50b, 50c, 50d, 50e independent, each radiating panel consisting of a structural module integrating a subset of several radiating sources 54 comprising RF chains machined in a matrix in a support plate common 51 to all the sources 54 of the sub-assembly, and independent of the support plates of the sources of the other panels. The RF power and output waveguides of the different radiating sources integrated in each panel 50a are then routed in the common support plate up to the respective input and output ports 55 which can, for example, be grouped in a same place of the corresponding panel. For example, all the entry and exit ports 55 can be aligned one beside the other, on an edge of the panel. In this case, the manufacturing of the RF chains integrated in each panel can be shared, all the RF chains being produced by machining in the form of three half-shells stacked and assembled together. This reduces manufacturing costs and reduces losses.

The different radiating panels 50a, 50b, 50c, 50d, 50e, are then assembled together to form the radiating network. To facilitate the assembly of the different panels together, the shapes of the cutouts of the different support plates corresponding to each panel are complementary to each other so that they can fit into each other, as shown in the figure 8c . Each panel of the radiating network can then be oriented independently of the other panels. The orientation of the RF chains integrated into each panel is then ensured overall by the orientation of the corresponding panel, then refined individually for each radiating source of the panel via the dedicated orientation ring which ensures the individual orientation of each radiant horn corresponding to each radiating source. The radiating network then forms a faceted assembly, each facet consisting of a radiating panel.

An example of installation of a radiating network in a multibeam antenna is represented on the figure 9 . The radiating network comprises at least one structural module or at least one radiating panel, the radiating panel comprising a structural module integrating radiating sources. The radiating network 60 according to the invention is placed at the focus of a reflector 61 to develop several different beams 1, 2, 3. Each radiating source is oriented individually, by means of the dedicated orientation ring, according to its location in the radiating network relative to the reflector.

Although the invention has been described in connection with particular embodiments, it is obvious that it is in no way limited thereto and that it includes all the technical equivalents of the means described as well as their combinations if these fall within the scope of the invention.

Claims (11)

1. Antenna structural module incorporating elementary radiating feeds, themselves comprising bent waveguides, each radiating feed comprising a radiating horn (16) linked to a bent waveguide intended to orient the radiating horn (16) in a desired direction,
   characterized in that the bent waveguide is an orientation ring (18) and in that each radiating feed further comprises an RF radio frequency chain (10) comprising a main waveguide (31) having longitudinal axis arranged at right angles to a plane XY and an orthomodal transducer OMT (30) comprising two mutually orthogonal transverse branches (41, 42), situated parallel to the plane XY and coupled at right angles to the main waveguide (31) by coupling slots, the radiating horn (16) being coupled to a terminal end (5) of the main waveguide (31) via the bent orientation ring (18) intended to orient the horn radiating (16) in a desired direction different from the longitudinal axis of the main waveguide (31), the bend of the orientation ring (18) being placed in a plane of symmetry of the RF chain, the plane of symmetry being orthogonal to the plane XY and containing the bisecting line (25) of the angle (26) formed by the two transverse branches (41, 42).
2. Structural module according to Claim 1, characterized in that it further comprises a support plate (17) common to all the radiating feeds, the RF chains (10) being completely incorporated in the support plate (17).
3. Structural module according to Claim 2, characterized in that the orientation ring (18) associated with each radiating horn is housed in a dedicated aperture formed in a front face (19) of the support plate (17).
4. Structural module according to Claim 2, characterized in that the terminal end (5) of the main waveguide (31) of each RF chain is housed in a dedicated aperture formed in a front face of the support plate (17) and in that the orientation ring (18) associated with each radiating horn is fixed onto a front face (19) of the support plate (17), in the extension of the corresponding terminal end (5).
5. Structural module according to one of Claims 1 to 4, characterized in that that the orientation ring (18) of each radiating feed consists of three parts secured together, the three parts consisting of two rigid access waveguides (21, 22) having different longitudinal axes (24, 23) and intended to be respectively linked to a radiating horn and to an RF chain, and a wave guide matching section (20) located between the two access waveguides, the wave guide matching section (20) forming the bend of the orientation ring (18).
6. Structural module according to one of claims 1 to 4, characterized in that the orientation ring (18) has a coupling iris.
7. Radiating panel characterized in that it comprises a structural module according to one of the preceding claims.
8. Radiating panel according to Claim 7, dependent on Claim 2, characterized in that the radiating feeds (54) are machined in a matrix in the common support plate (17, 51) and further comprise respective feed and output waveguides, routed in the common support plate and respectively linked to input accesses (55) and output ports grouped alongside one another on the radiating panel.
9. Radiating array characterized in that it comprises at least one radiating panel according to claim 8.
10. Radiating array according to Claim 9, characterized in that it comprises several radiating panels (50a, 50b, 50c, 50d, 50e) which can be oriented independently of one another.
11. Multibeam antenna characterized in that it comprises at least one radiating array according to one of claims 9 or 10.

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