SATELLITE PLATFORM AND METHOD FOR RECONFIGURING THE ELECTROMAGNETIC BEAM OF SUCH A SATELLITE PLATFORM

Description

technical field :

[0001] The invention lies in the field of antennas arranged on satellites, for HF, VHF, UHF radiocommunications: the antennas usually used are dipole or monopole antennas, each dimension of the size of the satellite being smaller than the wavelength. Previous technique

[0002] A dipole antenna consists of two metal elements joined together. It is fed at its center and designed to transmit or receive electromagnetic energy. The elements are usually aligned along the same axis, which defines the linear polarization of the emitted or received wave. A dipole antenna is typically used when the length of each of its two elements corresponds to a quarter of a wavelength. The resulting resonant mode allows the antenna to be easily adapted to traditional transmission lines. The radiation associated with such a dipole antenna is well known to those skilled in the art: in reference to the figure 1 using the usual decomposition (see below) of the radiated electric field E at point M according to the components E θ and E φ, such that E = E θ . e θ + E φ . e φ ,The field radiated by such a dipole oriented along the OZ axis radiates exclusively along the component E θ. The intensity of the field produced is maximum in the plane orthogonal to the dipole.

[0003] The usual decomposition mentioned above uses the basis of spherical coordinates: when only θ varies, M describes a semicircle and the unit vector e θ is tangent to this semicircle; when only φ varies, M describes a semicircle and the unit vector e φ is tangent to this semicircle. Further details will be found on https: / / en.wikipedia.org / wiki / Spherical coordinate system .

[0004] It is also known to combine two orthogonal dipoles, resulting in operation in both orthogonal linear polarizations. The antenna then consists of four elements, distributed every 90°. The two pairs of elements (or dipoles) are excited at their centers with two electromagnetic signals, allowing them to radiate two independent signals in both orthogonal linear polarizations. The directions of maximum radiation corresponding to each dipole will, however, lie in orthogonal planes. The plane where the field radiated by a dipole is maximum corresponds to a field of zero intensity for the dipole arranged orthogonally to the first.

[0005] Such dipole antennas have already been installed on nanosatellites. However, particularly in the VHF or UHF bands, a nanosatellite or minisatellite has dimensions comparable to a fraction of a wavelength: it significantly interferes with a dipole antenna, which considerably affects its own radiation pattern. Therefore, the initial approaches adopted by the scientific community favored a symmetrical positioning of the dipole relative to the nanosatellite to avoid the excitation of parasitic resonances on the satellite body and to reduce its diffraction, or alternatively, a remote positioning of the satellite body. This, however, results in additional design constraints, on top of all the other specifications (radiation direction diversity, polarization diversity).

[0006] A monopole antenna is a simplification of the dipole antenna. It consists of a single metallic element and is usually positioned at the center of a ground plane that is large compared to the wavelength. The symmetrical positioning minimizes diffraction generated by this ground plane when its size is on the same order of magnitude as the wavelength. Under these conditions, such an antenna radiates primarily in the half-plane above the ground plane. Applied to a rectangular mini-satellite (such as 12U or 16U nanosatellites, where 1U = 10⁻¹⁰¹⁰ cm³), this approach requires specific mounting points at the center of the longer side of the nanosatellite, as shown. This makes it difficult to mount multiple antennas.

[0007] Furthermore, in the case of dipole or monopole antennas, the deployment of a solar panel connected to the satellite alters the symmetry condition, and can then further increase the diffraction of the satellite.

[0008] Existing solutions therefore favor antenna subsystems that are arranged on the satellite in such a way as to minimize satellite diffraction. It is then very difficult to arrange multiple antennas under such conditions.

[0009] These wire antennas shown above are conventionally used as passive antennas, therefore producing a fixed, non-reconfigurable radiation.

[0010] Furthermore, beamforming is applied in a known manner to identical radiating elements, whose individual radiation covers the entire specified angular sector. Beamforming then makes it possible to increase the antenna gain and to create a more directional beam, which can be steered in a more specific direction within this angular sector, using a beamformer that distributes the same phase-weighted signal to the different elements. This approach could not be applied to the prior art dipole or monopole applications described above because, due to the constraints of antenna installation to minimize diffraction, it is not possible to create multiple radiating elements with the same radiation pattern.

[0011] US 11,152,987 B1 describes a direction-of-arrival estimation solution based on a passive receiver system comprising a first crossed dipole antenna on a platform of a first satellite, a second crossed dipole antenna on the platform, a passive receiver, and beam steering logic for the first and second crossed dipole antennas. The beam steering logic directs a radiation beam from the passive receiver in a first direction, aligned with a direct signal path aligned with a second satellite, and directs the radiation beam from the passive receiver in a second direction, aligned with a reflected signal path.

[0012] US 10 347 974 B1 describes a deployable biconical radio frequency satellite antenna, on a satellite. Summary of the invention :

[0013] To this end, according to a first embodiment, the present invention describes a satellite platform comprising: a satellite delimited by a satellite envelope consisting of metallic walls of the satellite, said walls comprising a first wall intended to face the earth, a second wall facing the first wall and third walls extending from the first wall to the second wall; an array of N electromagnetic transmitting and / or electromagnetic receiving antennas, Each antenna comprises said satellite casing and a respective metallic element extending in the plane of the first or second wall; and each antenna comprises a respective electrical connector, electrically connected to the element (i) and to the satellite casing and adapted, for: in transmission, to deliver a first electrical signal, received by the connector, to the element and to the satellite casing for electromagnetic radiation, by the antenna element and by the satellite casing, according to said first electrical signal; and / or in reception, to collect a second electrical signal resulting from the transposition, by the antenna element and by the satellite casing, of electromagnetic radiation received by the antenna; wherein, if N = 2, the orthogonal projections of the two elements onto the first wall are orthogonal and if N > 2, the orthogonal projection of the nth element onto the first wall is obtained by a rotation of +2π / N, n=2 to N,of the orthogonal projection of the (n-1)th element onto the first wall, said satellite platform comprising a beamformer adapted to obtain a control signal indicating any target directivity within an angular coverage sector and / or a target polarization to be implemented by the antenna array, said beamformer comprising a controller adapted to calculate an attenuation and a phase shift selectively for each antenna as a function of said control signal, said beamformer being adapted to: in transmission, apply to each of the first electrical signals intended for the N antennas, said attenuation and phase shift calculated for the antenna to which said first signal is intended and deliver to the connector associated with the antenna said first signal thus adapted; and / or in reception, apply, to each of said second electrical signals received by the connectors of the N antennas,the said attenuation and phase shift calculated for the antenna from which the said first signal originates.

[0014] Faced with the impossibility of completely avoiding diffraction by the satellite of the radiation from radiating elements, a radically different approach was chosen, consisting of including the satellite in the electromagnetic operation of the antenna, in order to establish communication with a mobile terminal on Earth emitting a signal in the same HF, VHF or UHF frequency band as the antenna.

[0015] Furthermore, since it is no longer possible to produce radiating elements with the same radiation patterns, the second idea is to instead use radiating elements with complementary radiation patterns, allowing the entire specified angular area to be covered by addition, ideally for each of the principal polarization components.

[0016] In particular embodiments, said satellite platform shall include one and / or the other of the following features: the strands are fixed at the periphery of the first or second wall in the plane of which they extend, said strands also extending outwards from said wall; the N strands extend in the plane of the first wall; N ≥4; the strands are made using tape measure technology; a ground plane at the level of the second wall and parallel to said second wall.

[0017] According to a second embodiment, the present invention describes a method for implementing an electromagnetic beam from a satellite platform comprising: a satellite delimited by a satellite envelope consisting of metallic walls of the satellite, said walls comprising a first wall intended to face the earth, a second wall facing the first wall and third walls extending from the first wall to the second wall; an array of N electromagnetic transmitting and / or electromagnetic receiving antennas, said method being characterized in that it comprises the following steps, each antenna comprising said satellite envelope and a respective metallic strand extending in the plane of the first or second wall and each antenna comprising a respective electrical connector, electrically connected to the strand and the satellite envelope, according to which, if N = 2, the orthogonal projections of the two strands on the first wall are orthogonal and if N > 2, the orthogonal projection of the nth strand on the first wall is obtained by a rotation of +2π / N, n=2 to N, of the orthogonal projection of the (n-1)th strand on the first wall: in transmission: supply of a first electrical signal, received by the connector, to the strand and the satellite envelope for electromagnetic radiation, by the antenna strand and by the satellite envelope, as a function of said first electrical signal;and / or in reception: collection of a second electrical signal resulting from the transposition, by the antenna element and by the satellite envelope, of electromagnetic radiation received by the antenna; obtaining by a beamformer of said satellite platform a control signal indicating any target directivity within an angular sector of coverage and / or a target polarization to be implemented by the antenna array, calculation by a controller of said beamformer of an attenuation and a phase shift selectively for each antenna as a function of said control signal, in transmission, application by said beamformer to each of the first electrical signals intended for the N antennas, of said attenuation and phase shift calculated for the antenna to which said first signal is intended and delivery to the connector associated with the antenna of said first signal thus adapted;and / or in reception, application by said beamformer to each of said second electrical signals collected by the connectors of the N antennas, of said attenuation and phase shift calculated for the antenna from which said first signal originates. ;

[0018] In particular embodiments, said satellite platform shall include one and / or the other of the following features: the strands are fixed at the periphery of the first or second wall in the plane of which they extend, said strands also extending outwards from said wall; the N strands extend in the plane of the first wall; N ≥4. Brief description of the figures:

[0019] The invention will be better understood and other features, details and advantages will become clearer from the following description, given by way of non-limiting reason, and from the accompanying figures, given by way of example. [ Fig. 1 ] There figure 1is an illustration of the radiation from a dipole antenna, as known from the prior art; [ Fig. 2 ] there figure 2 is a representation of a satellite platform in one embodiment of the invention; [ Fig. 3 ] there figure 3 is a schematic representation of beam formation in one embodiment of the invention; [ Fig. 4 ] there figure 4 illustrates the connection between the strands and the satellite in one embodiment of the invention; [ Fig. 5 ] there figure 5 is a representation of the unit radiation patterns in E φ polarization for each of 6 antennas in one embodiment of the invention; [ Fig. 6 ] there figure 6 is a representation of the unit radiation patterns in E θ polarization for each of 6 antennas in one embodiment of the invention; [ Fig. 7 ] there figure 7is a representation of a radiation pattern in E φ polarization obtained by beam formation in an embodiment of the invention; [ Fig. 8 ] there figure 8 is a representation of a radiation pattern in E θ polarization obtained by beam formation in an embodiment of the invention.

[0020] Identical references may be used in different figures when they refer to identical or comparable elements. Detailed description:

[0021] A particular embodiment of the invention is now described with reference to the figures.

[0022] There figure 2schematically represents a satellite platform 10 in an embodiment of the invention, in an orbital trajectory at a distance d from the earth T 20, d between 500 and 1000 km. The satellite platform 10 comprises a satellite 13 delimited by its metallic satellite envelope 11, describing here substantially a parallelepiped (generally, of dimensions at least 12 or 16 U with Earth face: for example 20*20 cm 2< (D1xD2) and height 30 or 40 cm (D3) or Earth face larger, for example 30*30, or height greater for example between 50-60 cm). The satellite platform 10 further includes solar panels 16 deployed around the satellite envelope 11. The metallic envelope 11 includes a wall 12, disposed facing the earth 25, a wall 14 facing the wall 12, in the opposite direction to the earth 25 and four lateral walls 15 extending from one to the other of the walls 12, 14 and thus closing the envelope 11.We will refer to wall 12 hereafter as wall . land side and wall 14, wall anti-earth face.

[0023] We consider an orthonormal frame (O, x, y, z) attached to the earth-facing wall 12, where O, x and y are respectively a point and two axes in the plane of the wall 12.

[0024] The satellite platform 10 includes an antenna system 17 comprising N antennas A1, A2, ..., AN, with N greater than or equal to 2. The antenna system 17 operates in HF, VHF, or UHF frequency bands, with wavelengths between 0.5 and 5 meters. The dimensions of the satellite 13 are on the order of several tenths of a wavelength; the width D1, the length D2, and the height D3 are each less than the wavelength, for example, between 1 / 4 of a wavelength and one wavelength.

[0025] For example, in the particular case considered, the antenna system 17 is in the VHF band, operating at 150 MHz, corresponding to a wavelength of 2 meters, and is fixed to the casing 11 of the satellite 13, with dimensions D1 x D2 x D3 equal to 20 cm x 20 cm x 40 cm (the satellite 13 in other embodiments is a mini-satellite, whose dimensions are comparable to the wavelength). The length of each metal element is one-quarter of a wavelength. Such a length allows the establishment of a quarter-wave mode on the metal element, which facilitates antenna matching (it should be noted that it is also possible to have a length corresponding to half a wavelength; a higher mode would be established on the antenna, which would also allow its matching, with a different radiation pattern from each radiating element).

[0026] As described above, the invention modifies the operation of a conventional dipole antenna by replacing, in each antenna Ai, i = 1 to N, the second element of the dipole with the satellite 13. Thus, each antenna Ai comprises a metallic element (element no. i) and the metallic casing 11 of the satellite 13. Each antenna Ai is powered by an electrical connector adapted to inject a useful electrical signal into element i at one end thereof and also into the satellite casing 11. Electrical currents are established on the walls of the satellite. A global resonance can then be established on the metallic element-satellite assembly.

[0027] In one embodiment, each strand extends in the plane of the wall 12 earth face or in that of the wall 14 anti-earth face.

[0028] In one embodiment, the direction of the strands (defined by the vector from the end of the strand connected to the electrical connector to the other end) is spatially distributed so as to obtain complementary maximum radiation directions (also called complementary preferred radiation directions).

[0029] In one embodiment, if N>2: if all the strands are in the plane of the same wall 12 earth face or 14 anti-earth, the strand of the antenna An is angularly spaced from the strand of the antenna An-1 by +2π / N, for n = 1 to N; if the strands are distributed between these two planes, this rule is then respected for the orthogonal projections of the strands onto the plane of the wall 12 earth face.

[0030] In one embodiment, the power connectors for the strands are located on the periphery of the ground-facing wall 12 (or anti-ground-facing wall 14), with the strands extending mostly outside the wall. This allows vertical currents (along the Oz axis) to be established primarily on the side walls 15 of the satellite.

[0031] Thus, in the embodiment considered with reference to the figure 2 N = 6 and the 6 strands, referenced 1, 2, 3, 4, 5, 6 anchored to the periphery of wall 12, extend mostly outside wall 12, in the plane of wall 12 facing Earth, corresponding here to the short side of the satellite. Any two adjacent strands are spaced at +2π / N (here π / 3).

[0032] In one embodiment, if N=2, the strands, all positioned in the plane of the wall 12 earth face or all positioned in the plane of the wall 14 anti-earth face (or the orthogonal projections of the strands, if they are distributed between these two planes) are angularly spaced at 90°.

[0033] In one embodiment, N is the total number of antennas on the platform, each comprising said satellite envelope and a respective metallic strand extending in the plane of the first or second wall.

[0034] In one embodiment, these metallic strands are manufactured using tape measure technology. Tape measures are flexible ribbons with a circular arc cross-section, the radius of curvature of which is convex on one side and concave on the other. The strand can thus be in a coiled configuration, occupying a small volume, before the antenna is put into operation, and be deployed and rigid upon activation. The ribbons are able to transition from the coiled to the deployed state primarily due to their inherent elastic energy. Tape measures are therefore well-suited for manufacturing deployable wire antennas and for minimizing antenna mass.

[0035] On the figure 4A detail of the antenna power supply for An, n = 1 to 6, is shown. The injection of the electrical signal into each antenna Ai between the element and the satellite casing is achieved by means of a connector 60, here a coaxial cable, located between the electronic module adapted to provide this signal in transmission (and / or to process this signal in reception; in one embodiment, this is the beamforming device 50 mentioned later). Each antenna An, n = 1 to N, is thus associated with a connector 60, carrying the electrical signal specific to that antenna An. The central core 61 of a connector 60 is connected to the end of the satellite element n anchored to the satellite. The peripheral ring 62 of the connector 60 is in direct contact with the ground-facing wall 12 of the satellite.The mass of the coaxial cable 60 is transferred to the metal mandrel 25 in direct contact with the wall 12 of the satellite (the mandrel 25 is attached to the wall 12 by tabs 26) (in another embodiment, the mass of the coaxial cable could be transferred directly to the earth face, at the level of the excitation of the metal strands).

[0036] In the case considered, the end of the strands which is anchored to the wall 12 is at the level of a mandrel 25 around which they were wound before the operational commissioning of the antenna system 17 for example (the deployment of the tape meters along their respective axis is ensured for example autonomously by their spontaneous unwinding following a step of release of the tapes by the disappearance of fusible wires when a high intensity current is triggered).

[0037] If an antenna element i Ai were anchored to one of the faces 12, 14, but perpendicular to these faces, the currents that would be established on that face would cancel each other out and contribute little to the radiation. The currents on the lateral walls 15, on the other hand, would contribute to the radiation: the resulting radiation pattern for the antenna Ai would be very similar to that of a half-wave dipole as shown in figure 1 , with very low radiation in E φ (-45 dB in a simulated example).

[0038] On the contrary, arranging the strands in the plane of walls 12 or 14 and anchored at the periphery of these walls, as proposed according to the invention, allows the component E φ to reach values ​​similar to those of the component E θ. The direction for which the component E θ is maximum corresponds to the direction for which the component E φ is minimum, and vice versa: for a strand in the plane of wall 12 facing ground, in the xn Oz plane, xn defining the axis of the nth metallic strand (n = 1 to N), the radiation along the component E θ is maximum in the xnOz plane, and the radiation along the component E φ is minimum in this plane; conversely, in the ynOz plane, the radiation along the component E φ is maximum and the radiation is minimum for the component E θ (using the terms E θ and E φ in reference to the figure 1 and considering an orthonormal coordinate system (yn , z, xn ) instead of (X, Y, Z)).

[0039] Also, if we consider the upper half-space (i.e., the space between the satellite and the Earth, and more specifically the typical angular sector applicable to mini or nano-satellites in low Earth orbit: θ < 55°, φ ∈ [0, 2π]) (the angles θ, φ are expressed in a spherical frame associated with the orthonormal Oxyz frame of the Earth). figure 2 (where er is oriented along the propagation direction and defines these angles), each radiating element (defined by a horizontal strand i and the nanosatellite) contributes over preferred angular regions. The angular regions corresponding to two radiating elements with adjacent strands evolve by a rotation of 2π / N, if there are N radiating elements.

[0040] There Figure 5 (respectively Figure 6 ) highlights these angular sectors, representing, as a function of angles A, B, the radiation according to the component E φ (respectively E θ ) in the configuration considered in figure 2for each antenna A1, ..., A6, represented in grey levels from -20 dBi, in steps of two. The angles A, respectively B, each in the window [-60, +60] are seen from the satellite, with A = θ sin(φ), B = θ cos(φ).

[0041] The preferred angular sectors corresponding to the two components Eφ and Eθ are orthogonal. Radiating elements with metallic strands oriented in opposite directions (such as strands 1 and 4, or links 2 and 5, or links 3 and 6) contribute over the same angular sectors. This effect is particularly pronounced for the radiation in Eφ polarization, which is primarily produced by the metallic strand and currents on the Earth-facing wall 12 of the satellite. The radiation patterns in Eθ polarization, to which the satellite's lateral walls 15 contribute, are less symmetrical, probably due to stronger currents on the lateral faces 15 located on the side of the metallic strand.

[0042] In one embodiment, the satellite platform 10 includes an electronic beamforming device 50 schematically represented in figure 3 allowing the synthesis of more directional beams (along a selected direction, any direction within the angular field covered by the sum of the radiation patterns), in a selected polarization, and increasing the gain (compared to the simple juxtaposition of unit beams from N antennas), by combining, after application of amplitude and phase weighting, the electrical signals associated with each radiating element.

[0043] The beamforming device 50 comprises an electronic controller 40 and a beamforming electronic block 30, including N processing chains, each processing chain i, i=1 to N, having an attenuator 31_i and a phase shifter 32_i. The attenuator 31_i is adapted to apply an attenuation gain to the input signal of processing chain i, and the phase shifter 32_i is adapted to apply a phase shift to the input signal of processing chain i. The gain and phase shift values ​​for each chain i are controlled by the controller 40 according to the specified preferred direction and polarization for the radiation of the antenna system 17.

[0044] During transmission, an electrical signal S carrying the information to be transmitted by the antenna system 17 is divided into N signals, one of these signals being supplied as input to each processing chain. An attenuation, followed by a phase shift, the values ​​of which are determined by the controller 40 selectively for each processing chain i, according to the specified direction and polarization of radiation from the antenna system 17, are applied, and the resulting signal Si is delivered to the electrical connector supplying the antenna Ai.

[0045] In reception, similarly, the electrical signals delivered by the antenna connectors A1, ..., AN are each phase-shifted and then attenuated, with on each chain i, an attenuation and phase shift of values ​​determined by the controller selectively for each chain i, according to the specified direction and polarization specified for the radiation received by the antenna system 17.

[0046] It should be noted that beam formation can be done in analog or, after frequency transposition, in digital.

[0047] In one embodiment, the values ​​of the attenuation and phase shift coefficients for each chain i, as a function of the specified direction and polarization for the radiation of the antenna system 17, are determined, in a prior calibration phase, by a conjugate matching process, which maximizes the gain in a given direction, or by an MMSE (minimum mean squared error) processing process which maximizes the gain in a given direction, while minimizing interference in other directions.

[0048] In the configuration shown in figure 2where N=6, it was thus possible to create successively, as examples, 24 beams each corresponding to a distinct preferred radiation direction, regularly distributed over the coverage, pointing at a constant elevation θ = 55° from the satellite and contributing according to the polarization E φ (one of these 24 beams is represented in figure 7 (with the same gray levels as previously considered), as well as 24 other beams, each corresponding to a distinct preferred radiation direction, regularly distributed across the coverage, pointing at a constant elevation θ = 55° and contributing according to the polarization E θ (one of these 24 beams is shown in figure 8 It was measured that the gain is increased by an average of 4 dB compared to the diagrams of unitary Ai antennas. Here again, it appears that the maximum radiation in the Eφ component is obtained for a minimum Eθ component and vice versa.

[0049] The 'Conjugate Matching' process calculates the weighting applied to the different radiating elements to maximize the gain in a direction θ, φ, and for a given polarization. It calculates the attenuation and phase shift coefficients so that they are the conjugate coefficients of the illumination law of the different radiating elements, illuminated by a plane wave with the considered polarization, and incident in a direction θ, φ.

[0050] The diagrams of the individual radiating elements show their incidence responses. Consequently, the amplitude coefficients vary in the range of values ​​between 0 and -20dB, and the phase law in the range of values ​​between 0 and 360°.

[0051] The controller 40, in embodiments, is adapted to, in response to a received command, control the switching between two distinct beamforming configurations (for example following a change in the geographical location of a mobile terminal with which radio communication is to be established via the antenna system 17), resulting in the replacement of the beamforming coefficients with new values ​​in order to focus the antenna in another direction and / or with another polarization, while increasing the gain compared to the simple summation of the individual antenna diagrams Ai, i = 1 to N.The controller 40, in embodiments, is adapted to, in response to a received command, control the switching between a beamforming configuration and a basic configuration simply summing the individual diagrams (without beamforming), or even a minimal configuration by feeding, for example, only a few antennas.

[0052] The size of the satellite 13 determines the surface current distributions established on it. Longer lateral walls 15 (larger D3), for example, can support a higher-order mode for the vertical currents established along these lateral walls. A satellite with larger walls 12, 14 will increase the radiation along the Eφ component. The operating mode remains the same, however, with regard to the complementarity of the angular sectors associated with the Eθ and Eφ components. Commercial electromagnetic simulation tools now make it possible to predict this overall operation accurately by modeling the antenna system and its satellite environment.

[0053] In one embodiment, to minimize radiation in the lower half of space, the satellite platform 10 further includes a ground plane 22 orthogonal to the satellite's lateral walls 15 (for example, the ground plane 22 in the plane of the anti-Earth wall 14 or parallel to and located just below it). This large ground plane 22 can be a highly perforated grid, with opening sizes on the order of λ / 10; each side of this plane is at least 5λ. It could be deployed simultaneously with the solar arrays 16.

[0054] The deployment of such a ground plane 22 significantly increases the gain in the upper half of the space. It does not alter the operation of the antenna system 17, which remains reconfigurable in terms of pointing and polarization.

[0055] The present invention thus proposes, in a manner compatible with the constraints inherent to small satellite platforms, a deployable antenna, reconfigurable in pointing direction and polarization, enabling the generation of a beam with a gain superior to that of an omnidirectional antenna, typically 2-5 dBi, in any direction within a wide angular sector (typically ± 60°). The solution is therefore particularly well-suited to the constraints encountered in communications with ground-based terminals that may move across highly varied geographical areas and where controlling the polarization of the transmitted signal is difficult, especially given that it is also affected by atmospheric propagation conditions.

Claims

1. Satellite platform (10) comprising: - a satellite (13) delimited by a satellite casing (11) constituted of metal walls (12, 14, 15) of the satellite, said walls comprising a first wall (12) intended to face the Earth (25), a second wall (14) facing the first wall and third walls (15) extending from the first wall to the second wall; - a network of N electromagnetic emission and / or electromagnetic reception antennas (Ai, i=1 to 6), each antenna comprises said satellite casing (11) and a respective metal strand (i=1 to 6) extending in the plane of the first (12) or second (14) wall, and; each antenna (Ai, i=1 to 6) comprises a respective electrical connector (60), electrically connected to the strand (i) and to the satellite casing (11), and adapted, to: in emission, issue a first electrical signal, received by the connector (60), to the strand (i=1 to 6) and to the satellite casing (11) for electromagnetic radiation, by the strand of the antenna and by the satellite casing, according to said first electrical signal; and / or in reception, to collect a second electrical signal coming from the transposition, by the strand of the antenna (i=1 to 6) and by the satellite casing (11), of an electromagnetic radiation received by the antenna; in which, if N = 2, the orthogonal projections of the two strands on the first wall are orthogonal, and if N > 2, the orthogonal projection of the nth strand on the first wall (12) is obtained by a rotation of +2π / N, n = 2 to N, of the orthogonal projection of the (n-1)th strand on the first wall (12), said satellite platform (10) comprising a beamformer (50) adapted to obtain a control signal indicating any target directivity within a coverage angular sector and / or a target polarization to be implemented by the antenna network, said beamformer (50) comprising a controller (40) adapted to calculate an attenuation and a phase shift selectively for each antenna according to said control signal, said beamformer (50) being adapted to: in emission, apply to each of the first electrical signals intended for the N antennas, said attenuation and phase shift calculated for the antenna for which said first signal is intended and issue to the connector (60) associated with the antenna, said first signal thus adapted; and / or in reception, apply, to each of said second electrical signals collected by the connectors (60) of the N antennas, said attenuation and phase shift calculated for the antenna, from which said first signal originates.

2. Satellite platform (10) according to claim 1, wherein the strands (i=1 to 6) are fixed at the periphery of the first (12) or second (14) wall in the plane from which they extend, said strands (i=1 to 6) further extending to the outside of said wall.

3. Satellite platform (10) according to any one of the preceding claims, wherein the N strands extend in the plane of the first wall.

4. Satellite platform (10) according to any one of the preceding claims, wherein N ≥4.

5. Satellite platform (10) according to any one of the preceding claims, wherein the strands (i=1 to 6) are made in tape measure technology.

6. Satellite platform (10) according to any one of the preceding claims, comprising a ground plane (22) at the second wall (14) and parallel to said second wall.

7. Method for implementing an electromagnetic beam of a satellite platform (10) comprising: - a satellite (13) delimited by a satellite casing (11) constituted of metal walls (12, 14, 15) of the satellite, said walls comprising a first wall (12) intended to face the Earth (25), a second wall (14) facing the first wall and third walls (15) extending from the first wall to the second wall; - a network of N electromagnetic emission and / or electromagnetic reception antennas (Ai, i=1 to 6), said method being characterized in that it comprises the following steps, each antenna comprising said satellite casing (11) and a respective metal strand (i=1 to 6) extending in the plane of the first (12) or second (14) wall and each antenna (Ai, i=1 to 6) comprising a respective electrical connector (60), electrically connected to the strand (i) and to the satellite casing (11), whereby, if N = 2, the orthogonal projections of the two strands on the first wall are orthgonal and if N > 2, the orthogonal projection of the nth strand on the first wall (12) is obtained by a rotation of +2π / N, n=2 to N, of the orthogonal projection of the (n-1)th strand on the first wall (12): in emission: provision of a first electrical signal, received by the connector (60), to the strand (i=1 to 6) and to the satellite casing (11) for electromagnetic radiation, by the strand of the antenna and by the satellite casing, according to said first electrical signal; and / or in reception: collection of a second electrical signal coming from the transposition, by the strand of the antenna (i=1 to 6) and by the satellite casing (11), of an electromagnetic radiation received by the antenna; - obtaining by a beamformer (50) of said satellite platform (10) of a control signal indicating any target directivity within a coverage angular sector and / or a target polarisation to be implemented by the antenna network, - calculation by a controller (40) of said beamformer (50) of an attenuation and of a phase shift selectively for each antenna according to said control signal, in emission, application by said beamformer (50) to each of the first electrical signals intended for the N antennas, said attenuation and phase shift calculated for the antenna for which said first signal is intended and deliver to the connector (60) associated with the antenna of said first signal thus adapted; and / or in reception, application by said beamformer of networks (50) to each of said second electrical signals collected by the connectors (60) of the N antennas, said attenuation and phase shift calculated for the antenna, from which said first signal originates.

8. Method for implementing an electromagnetic beam of a satellite platform (10) according to claim 7, whereby the strands (i=1 to 6) are fixed at the periphery of the first (12) or second (14) wall in the plane from which they extend, said strands (i=1 to 6) further extending to the outside of said wall.

9. Method for implementing an electromagnetic beam of a satellite platform (10), according to any one of claims 7 or 8, whereby the N strands extend in the plane of the first wall.

10. Method for implementing an electromagnetic beam of a satellite platform (10), according to any one of claims 7 to 9, whereby N ≥4.