Satellite platform having improved characteristics in respect of electromagnetic decoupling between radiating elements and corresponding construction process

Abstract

The invention relates to a satellite platform comprising a plurality of radiating elements (111, 112) designed to receive and / or transmit electromagnetic radiation and including at least one transmitter radiating element (112). Such a platform comprises at least one block (165) of material that absorbs electromagnetic radiation in a frequency band of interest in order to decrease electromagnetic coupling between the radiating elements. The block of material is implemented in at least one region of interest in the satellite platform to decrease electromagnetic coupling, the region of interest intersecting at least one predominant path (120) of coupling between at least two of the radiating elements.

Description

Scope of the invention

[0001] The field of invention is that of satellite platforms.

[0002] The invention relates more particularly to a satellite platform exhibiting improved electromagnetic decoupling characteristics between radiating elements of the platform.

[0003] The invention thus has applications, in particular, but not exclusively, for all satellite platforms for which electromagnetic couplings between radiating elements are an important issue, such as small satellite platforms. Prior art and its drawbacks

[0004] In the space sector, there has been a surge in communication and observation satellites, particularly satellite constellations comprising numerous small satellites. Examples include, but are not limited to, the Starlink, Kineis, OneWeb, and CO3D constellations. This growth is accompanied by a proliferation of radio communication links and operating frequencies used by the platform's payload. Consequently, there is an increasing need for antennas, especially on smaller platforms. Document EP2863473, filed on behalf of Airbus Defence and Space GmbH and entitled "Space Antenna System," describes an RF decoupling joint between two panels, each with a radiating surface.

[0005] The present invention aims to further improve the decoupling between receiving and emitting elements of electromagnetic radiation present on a satellite platform.

[0006] The article by SU Hwu and YC Loh, "Space station GPS multipath analysis and validation," 1999 IEEE 49th Vehicular Technology Conference, Houston, TX, USA, 1999, pp. 757-761 vol.1, deals with an electromagnetic modeling tool based on the geometric theory of diffraction for the simulation of the electromagnetic environment of a GPS receiver, for example implemented in a satellite.

[0007] The article by G. Gonçalves Machado, R. Cahill, V. Fusco, and G. Conway, "Resistively Loaded FSS Clad Thermal Blankets for Enhanced RF Space Communications," 2019 International Conference on Electromagnetics in Advanced Applications (ICEAA), Granada, Spain, 2019, pp. 48-52, discusses improving the RF performance of radio frequency communication systems, such as those on satellites, through the use of frequency-selective surfaces (FSS). US patent document US6097327A1 describes an RF absorber that can be used in a satellite launch vehicle.

[0008] Patent document US6217978B1 deals in general terms with a fire-resistant honeycomb RF absorber material. Description of the invention

[0009] The invention relates to a method for constructing a satellite platform according to claim 1.

[0010] In some embodiments, the electromagnetic absorbing material block consists exclusively of the alveolar material impregnated with the charged electromagnetic absorbing resin.

[0011] In some embodiments, the electromagnetic absorbing resin is obtained by injecting carbon black particles into a phenolic resin or into an acrylic paint.

[0012] In some embodiments, the step of obtaining the electromagnetic absorbing material block includes a step of determining, as a function of the target permittivity, at least one parameter belonging to the group comprising: a mesh size of the alveolar material; a particle loading rate of the resin; a concentration rate of carbon black particles; a quantity of loaded resin impregnated onto the alveolar material; and a sizing of the absorbent material block.

[0013] In some embodiments, the cellular material is chosen with a mesh size between 3 and 12 millimeters to receive a surface layer of electromagnetic absorbing resin by impregnation in a quantity between 5 kilograms and 150 kilograms per cubic meter, so that the block of absorbing material retains a hollow structure.

[0014] In some embodiments, the step of obtaining the block of electromagnetic absorbing material includes a step of measuring the permittivity of the electromagnetic absorbing material, followed if the target permittivity is not reached, by a further impregnation step.

[0015] In some embodiments, the area of ​​interest determination step includes determining the size of the absorbing material block and the area of ​​interest extending over an outer face of the satellite platform. The absorbing material block, occupying the area of ​​interest, has characteristic dimensions smaller than the largest dimension of the platform in order to achieve localized electromagnetic absorption.

[0016] Advantageously, the invention improves the decoupling between receiving and emitting elements of intentional or unintentional electromagnetic radiation, such as antennas in communication systems or elements of Hall effect motors, through the use of a material exhibiting electromagnetic absorption characteristics in a corresponding frequency band. More specifically, such a material is implemented in a region of interest to achieve the desired reduction.

[0017] Another advantage of the invention is that it allows for the interruption of a path between two radiating elements where, in particular, creeping waves propagate along a face of the satellite. This can be achieved in direct line of sight to interrupt a direct coupling path or in indirect line of sight to interrupt an indirect coupling path through reflection, diffraction, double diffraction, or scattering. Advantageously, the cellular material, for example, an aramid-based material such as Nomex® honeycomb, can have a mesh size particularly well-suited to aeronautical and space applications. Furthermore, such a material can easily be filled with electromagnetic absorbing resin. List of figures

[0018] Other objects, features and advantages of the invention will become more apparent upon reading the following description, given by way of simple illustration and not limitation, in relation to the figures, among which: [ Fig. 1a ] represents a satellite platform according to an example of an embodiment of the invention; [ Fig.1b1 ] represents a partial, detailed view of the platform's hosting structure Fig. 1a according to a first example of an embodiment of the invention; [ Fig.1b2 ] represents a detailed view of the platform's hosting structure Fig. 1a in addition to the Fig.1b1 ; Fig.1c1 ] represents a partial, detailed view of the platform's hosting structure Fig. 1a according to a second embodiment of the invention; [ Fig.1c2 ] represents a detailed view of the platform's hosting structure Fig. 1a in addition to the Fig.1c1 ; Fig. 2a ] represents a top view of an electromagnetic absorbing material comprising a cellular material impregnated with an electromagnetically absorbing charged resin according to an embodiment of the invention; [ Fig. 2b] represents a side view of a cell of the material of the Fig. 2a ; And [ Fig.3 ] illustrates the steps of a process for constructing a satellite platform according to an example of an embodiment of the invention. Detailed description of embodiments of the invention

[0019] Radio frequency electromagnetic coupling increases due to the proximity between different antenna access points on small platforms, with this trend worsening particularly at low frequencies.

[0020] Furthermore, there is also a growing trend towards electric propulsion through the use of Hall effect motors for such satellite platforms. These motors are a major source of broadband electromagnetic noise for onboard receivers, particularly at low frequencies (typically in the VHF to S-band range).

[0021] The use of such electric motors, combined with increasingly close proximity of radio frequency transmitters and receivers, leads to new electromagnetic compatibility issues for these satellite platforms. These issues are further exacerbated on smaller satellite platforms, as mentioned above.

[0022] The general principle of the invention is based in particular on the implementation of an electromagnetic absorbing material comprising a cellular material impregnated with a charged electromagnetic absorbing resin in a frequency band of interest for reducing electromagnetic coupling between radiating elements of the type receiver and / or emitter of electromagnetic radiation on a satellite platform. More specifically, the material is implemented in at least one area of ​​interest of the satellite platform for reducing electromagnetic coupling. Such an area of ​​interest intersects one or more predominant coupling paths between several radiating elements. Thus, the electromagnetic coupling is reduced to an acceptable level.

[0023] The term "frequency band of interest" here refers to the frequency band in which a reduction of electromagnetic coupling between the radiating elements under consideration is beneficial for improving the operating performance of the radio frequency transmitters and / or receivers associated with all or part of the radiating elements in question. Furthermore, an electromagnetic absorbing material is defined as any material that attenuates electromagnetic waves propagating along the coupling path considered within a given frequency band, in this case, the frequency band of interest. Such attenuation is achieved, for example, within the absorbing material itself by dissipating electromagnetic energy as thermal energy.

[0024] We now present, in relation to the Fig. 1a, Fig. 1b1 And Fig.1b2 a satellite platform 100 according to a first example of implementation of the invention.

[0025] More specifically, the satellite platform 100 includes a hosting structure 110 designed to accommodate the main functional sub-assemblies of the satellite (e.g. the flight control or propulsion system), as well as deployable solar panels 120.

[0026] In some embodiments, other satellite platform structures are considered, for example with other energy sources than solar panels.

[0027] Back to Fig.1b1 and Fig.1b2The housing structure 110 further includes a receiving antenna 111 (for example, a GPS (Global Positioning System) receiving antenna) and an electromagnetic radiation emitting element, here the output 112 of a Hall effect electric motor. During its operation, the electric motor produces broadband electromagnetic noise having a non-zero component at the receiving frequency of the antenna 111, for example, in a frequency band encompassing the GPS receiving frequencies, i.e., 1575.42 MHz and 1227.60 MHz.

[0028] More specifically, electromagnetic coupling between output 112 and antenna 111 would occur predominantly via coupling path 120. Such a predominant coupling path 120 corresponds, in practice, to a path where the intensity of the electromagnetic field exceeds a predetermined threshold. This threshold is defined, for example, as a threshold beyond which the risk of electromagnetic interference to antenna 111 from output 112 becomes significant, i.e., a significant impact on the reception performance of the receiving system processing the signals received via antenna 111.

[0029] In such an example, the frequency band of interest corresponds to the operating frequency band of the GPS receiver, i.e., a band encompassing the frequencies 1575.42 MHz and 1227.60 MHz. The electromagnetic absorbing material exhibits a specific attenuation within this frequency band to guarantee a predetermined level of GPS system performance, for example, in terms of reception parameter quality such as SNR (Signal-to-Noise Ratio) or BER (Bit Error Rate). The same approach can be followed for any receiving system processing a wave received by a radiating element subjected to electromagnetic interference induced by a transmitting radiating element of the satellite platform. The block of electromagnetic absorbing material induces, for example, an attenuation of at least 5 dB, for instance, in the L and S bands.

[0030] In the case illustrated on the Fig.1b1 and Fig.1b2The predominant path 120 is of the indirect type, which corresponds to an indirect interaction between the output 112 and the antenna 111. The output 112 and the antenna 111 are located here on distinct faces of the host structure 110.

[0031] In some embodiments, such a predominant path is of the direct type and corresponds to a direct view between a radiating element of the type emitting electromagnetic radiation and a radiating element of the type receiving electromagnetic radiation.

[0032] In general, a satellite platform according to the invention comprises a plurality of radiating elements of the type that receive and / or emit electromagnetic radiation, including at least one emitter. More specifically, such electromagnetic radiation may be intentional or unintentional. The radiating elements in question are, for example, antennas for communication systems as well as Hall effect motors as described above.

[0033] Back to Fig.1b1 and Fig.1b2To reduce electromagnetic coupling between output 112 and antenna 111, a block 155 of electromagnetic absorbing material is implemented in a zone of interest on the satellite platform 100. This zone of interest is positioned over an area 150 on the surface of the platform so as to intersect the predominant coupling path 120 between output 112 and antenna 111. More specifically, the zone of interest covers at least part of an outer face of the satellite platform 100. The parallelepiped-shaped block 155 of absorbing material has characteristic dimensions smaller than the largest dimension of the supporting structure 110 in order to achieve localized electromagnetic absorption.

[0034] Indeed, coupling paths correspond to parasitic radiation phenomena inducing waves that propagate particularly along the external conductive surfaces of the satellite platform 100. A coupling path, for example of the creeping type, can thus appear between two radiating elements, even if located on different faces of the satellite platform 100. The external partition of the satellite platform 100 generally tends to guide this parasitic wave.

[0035] This allows us, for example, to cut a path where creeping waves propagate along a face of the satellite, in direct view (i.e. direct coupling path) or in indirect view (i.e. indirect coupling path by reflection, double diffraction or scattering).

[0036] In some embodiments, the block of absorbent material takes other forms, for example in a ring or a diamond shape.

[0037] For example, the Fig.1c1 And Fig.1c2 These figures illustrate a second embodiment of the host structure 110 in which the coupling path 130 is direct and corresponds to a direct line of sight between the receiving antenna 111 and an antenna 113 of a communication system including a transmitting section. Furthermore, the electromagnetic absorbing material block 165 is implemented in an area of ​​interest within a 160 area of ​​the satellite platform 100 to reduce electromagnetic coupling between the receiving antenna 111 and the antenna 113 of the communication system. In this example, the electromagnetic absorbing material block 165 has an elliptical profile.

[0038] In certain embodiments where the satellite platform 100 comprises various radiating elements of the electromagnetic radiation receiver and / or transmitter type, several coupling paths between different radiating elements may exist. Thus, different blocks of absorbing materials, with the same or different geometries and dimensions, may be implemented in different areas of interest on the satellite platform. These material blocks may exhibit identical or distinct radio frequency absorption characteristics, for example, with absorptions optimized for different frequency bands.

[0039] Back to Fig.1b1 and Fig.1b2, the material is electromagnetic absorbing in a frequency band of interest for reducing electromagnetic coupling between the radiating elements 112 and 111, for example a frequency band including the frequencies 1575.42 MHz and 1227.60 MHz as discussed above.

[0040] According to the example of implementation of the Fig. 2a and Fig. 2b ,The absorbing block 155, 165 is formed from a material 200 comprising a honeycomb material 210, also known as a "honeycomb" material, impregnated with an electromagnetically absorbing resin. Specifically, the honeycomb material 210 has a mesh size 220 of a few millimeters, e.g., from 3 to 12 millimeters, to accommodate one or more surface layers of the resin. For example, the amount of resin impregnated ranges from a few kilograms, e.g., 5 kilograms, to 150 kilograms per cubic meter. Thus, the absorbing block retains a hollow structure. Furthermore, such a resin charge provides good electromagnetic absorption performance without the material 200 becoming conductive.

[0041] For example, the 210 cellular material has a mesh size of 4.6 mm, 6.4 mm, or 9.6 mm, particularly suited to aerospace applications. The cell height is, for example, 5 cm. Such a 210 cellular material is, for example, aramid-based, such as Nomex®.

[0042] In some embodiments, the electromagnetic absorbing material block consists exclusively of the alveolar material 210 impregnated with the electromagnetic absorbing charged resin.

[0043] In some embodiments, the filled resin comprises a phenolic resin, or an acrylic paint, filled with carbon black particles. For example, the filling rate is preferably between 5 and 20% by mass, and even more preferably between 6 and 12% by mass, in order to obtain good electromagnetic absorption performance.

[0044] In some embodiments, the cell walls 230 of the cellular material 210 are arranged perpendicular to an outer face of the satellite platform 100. This advantageously leads to improved decoupling performance. Such an improvement, by moving from cells oriented along an outer face to cells oriented perpendicular to the outer face, is, for example, on the order of 5 dB in the L and S bands, and more than 10 dB in the X band and beyond.

[0045] Satellite platform 100, for example, is obtained by implementing the construction process now described in relation to the Fig.3 .

[0046] Considering more specifically, by way of non-limiting example, the example of the implementation of the 100 satellite platform of Fig.1b1 and Fig.1b2 , during a stage E300, The predominant coupling path 120 between output 112 and antenna 111 is determined.

[0047] For example, an electromagnetic coupling calculation between output 112 and antenna 111 is performed in the absence of absorbing material. Such a calculation is carried out, for example, by numerical simulation using a 3D model of the satellite platform 100, or at least of the host structure 110. Each electromagnetic coupling is thus determined by calculation and compared with a predetermined threshold in order to decide whether this path 120 is a predominant path or not, as described above in relation to the Fig. 1a , there Fig.1b1 and the Fig.1b2 .

[0048] The comparison allows us to decide whether to implement absorption treatment, in order to reduce the coupling between output 112 and antenna 111. In other words, when the electromagnetic coupling between output 112 and antenna 111 is greater than the predetermined threshold, it is decided to implement the treatment in question.

[0049] In other embodiments, the predominant coupling path 120 between the output 112 and the antenna 111 is determined in another way, for example empirically, or based on measurements obtained on previous implementations, such as in the case of mass-produced satellite platforms.

[0050] Back to the Fig.3 , during a step E310, at least one area of ​​interest is determined so that the area of ​​interest intersects at least one predominant path 120 determined during the implementation of step E300. For example, the area of ​​interest is positioned on an area 150 intersecting a creeping path where creeping waves propagate along a face of the satellite, in direct or indirect view, the area of ​​interest extending over an outer face of the satellite platform.

[0051] For example, step E310 includes determining the size of a block 155 of absorbing material to be implemented in the area of ​​interest. Such a block 155 of absorbing material, parallelepiped in shape, has characteristic dimensions smaller than the largest dimension of the host structure 110 in order to achieve local electromagnetic absorption.

[0052] In some embodiments, the absorbing material block takes other shapes, for example, a ring. Electromagnetic absorbing material blocks with an oval or rhombic profile can also be considered. An example of an oval surface 160 where creeping waves propagate is shown, for example, in the Fig.1c1 .

[0053] Back to the Fig.3 , during a stage E320,block 155, 165 is manufactured from electromagnetic absorbing material in a frequency band of interest for reducing electromagnetic coupling between radiating elements 112 and 111.

[0054] Thus, during a step E320a, A target permittivity for the 155, 165 block of electromagnetic absorbing material is determined based on the desired predetermined absorption treatment. In other words, the target permittivity is determined, for example by electromagnetic simulation, so as to obtain the desired absorption properties for the absorbing material.

[0055] In some embodiments, step E320a is not implemented and the target permittivity is already known, for example empirically or on the basis of previous implementations.

[0056] As described above in relation to the Fig. 2a and Fig. 2bThe block 155, 165 of material 200 implemented on the satellite platform 100 comprises (or is made exclusively of) a cellular material 210 impregnated with an electromagnetically absorbing charged resin. For example, the charged resin comprises a phenolic resin, or an acrylic paint, charged with carbon black particles.

[0057] Thus, during a step E320b of sizing, to the Fig.3 One or more parameters of the electromagnetic absorbing material 200 are obtained, for example, as a function of the target permittivity, for example, by electromagnetic simulation or empirically based on previous implementations. This parameter or these parameters belong, for example, to the group comprising: a mesh size 220 of the cellular material 210; a particle loading rate of the resin; a concentration rate of carbon black particles; a quantity of charged resin impregnated on the cellular material; and a dimensioning of the absorbent material block including, for example, its thickness and extent in a plane parallel to the implementation face.

[0058] For example, the cellular material is chosen with a mesh size of a few millimeters, e.g. 3 to 12 millimeters, to receive a surface layer of electromagnetic absorbing resin by impregnation in a quantity between a few kilograms, e.g. 5 kilograms, and 150 kilograms per cubic meter, so that the block of absorbing material retains a hollow structure.

[0059] During a step E320cIn the manufacture of the resin, the electromagnetic absorbing resin is obtained by injecting carbon black particles into a phenolic resin or into an acrylic paint, according to the parameter(s) obtained during the implementation of the E320b dimensioning step.

[0060] During a Next step: E320d The cellular material 210 is impregnated with the electromagnetically absorbing charged resin obtained in the previous step E320c. Such impregnation is carried out, for example, by dipping or spray painting.

[0061] In some embodiments, the E320c resin manufacturing step is not implemented, the filled resin being obtained, for example, from a supplier.

[0062] Back to the Fig.3 , in a subsequent step E320e,The permittivity of the impregnated cellular material 210 is measured, for example. Such a measurement is typically performed after the cellular material 210 impregnated with the resin has dried. For example, such a measurement employs two waveguides between which a sample of the material is placed. The permittivity of the material is thus estimated by comparing the wave incident on the sample with the wave received after passing through the sample.

[0063] The measurement thus obtained is compared to the target permittivity. For example, if the target permittivity is not reached, a further impregnation step E320d is implemented. Therefore, the measurement taken during step E320e is an intermediate measurement or, where applicable, a final measurement.

[0064] After the manufacture of block 155, 165 of absorbent material, during a step E330,The absorbent block 155, 165 is implemented in the area of ​​interest over a defined area 150, 160 of one face of the platform. For example, the block of material is fixed to the outer wall of the satellite platform 100 by gluing, brackets, or a mechanical support structure.

[0065] The electromagnetic absorption block is a component identified as a radio frequency absorber attached to an external surface of the satellite. Therefore, the electromagnetic absorption block does not serve a supporting function. The electromagnetic absorption block is not a structural element, such as a partition delimiting the interior of the satellite or a supporting structural element.

[0066] In some embodiments, the walls 230 of the cellular material 210 are arranged perpendicular to an external face of the satellite platform 100. This advantageously leads to better decoupling performance.

[0067] In some embodiments, steps E320a (determining the target permittivity), E320b (sizing the block), and / or E320e (measuring) are not necessarily carried out, particularly when the composition of the absorbent material to be obtained is already known. In such cases, it only remains to manufacture the material by carrying out steps E320c (making the resin) and E320d (impregnating).

[0068] Thus, in general, the implementation of the process of the Fig.3 allows the construction of a satellite platform according to any of the embodiments described above in relation to the Fig.1a, Fig.1b1, Fig.1b2 , Fig.1c1, Fig.1c2 , Fig. 2a and Fig. 2b .

[0069] In particular, in the aforementioned embodiments where the satellite platform comprises various radiating elements of the electromagnetic radiation receiver and / or emitter type, and where several coupling paths exist between different radiating elements, the various stages of the construction process described above (according to any one of the aforementioned embodiments) can be implemented multiple times for different couplings existing between two radiating elements of the satellite platform. In this way, several blocks of absorbing materials can be implemented in different areas of interest on the platform.

Claims

1. A process for constructing a satellite platform (100) comprising a plurality of radiating elements (111, 112, 113) of the electromagnetic radiation receiver or transmitter type, including at least one transmitter radiating element (112, 113), wherein the process comprises: - a step (E300) of determining at least one predominant coupling path (120, 130) between at least two of said radiating elements; - a step (E310) of determining at least one region of interest on said satellite platform to decrease electromagnetic coupling between the radiating elements so that said region of interest intersects said predominant path; - a step (E320) of obtaining at least one block (155, 165) of a material electromagnetically absorbing in a frequency band of interest to decrease electromagnetic coupling between the radiating elements comprising at least one step (E320d) of impregnating a cellular material with an electromagnetic absorbing filled resin; and - a step (E330) of implementing said block of absorbing material in said region of interest, the step of determining said predominant path comprising calculating an electromagnetic coupling in the absence of absorbing material and comparing the electromagnetic coupling with a predetermined threshold to decide to implement a predetermined absorption treatment, and the step of obtaining said block of electromagnetic absorbing material comprising a step (E320a) of determining a target permittivity for said block of electromagnetic absorbing material according to the predetermined absorption treatment.

2. The process according to claim 1, wherein said block (155, 165) of electromagnetic absorbing material consists exclusively of the cellular material (210) impregnated with the electromagnetic absorbing filled resin.

3. The process according to any one of claims 1 or 2, wherein the electromagnetic absorbing resin is obtained by injecting (E320c) carbon black particles into a phenolic resin or an acrylic paint.

4. The process according to any one of claims 1 to 3, wherein the step of obtaining said block of electromagnetic absorbing material comprises a step (E320b) of determining, according to the target permittivity, at least one parameter from the group comprising: - a mesh size of said cellular material; - a particle charge rate of said resin; - a concentration rate of carbon black particles; - an amount of impregnated filled resin on said cellular material; and - a sizing of said block of absorbing material.

5. The process according to any one of claims 1 to 4, wherein the cellular material is selected with a mesh size comprised between 3 and 12 millimeters to receive a surface layer of an electromagnetic absorbing resin by impregnation according to an amount comprised between 5 kilograms and 150 kilograms per cubic meter, so that the block of absorbing material keeps a hollow structure.

6. The process according to claim 4 or 5 when dependent on claim 4, wherein the step of obtaining said block of electromagnetic absorbing material comprises a step (E320e) of measuring the permittivity of said electromagnetic absorbing material followed, if the target permittivity is not reached, with a new impregnation step.

7. The process according to any one of claims 1 to 6, wherein the step of determining the region of interest comprises determining the size of said block of absorbing material and of said region of interest extending over an external face of the satellite platform, said block of absorbing material, occupying the region of interest, having characteristic dimensions smaller than the largest dimension of the platform so as to achieve a local electromagnetic absorption.

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