IMPROVED ANTENNA SYSTEM AND DECOUPLING DEVICE THEREFOR

Description

[0001] The present invention relates to antenna systems, and more particularly, to antenna systems equipped with an electromagnetic decoupling device - EM between an elementary antenna and its immediate environment.

[0002] An antenna system comprises one or more antenna assemblies, each antenna assemblie in turn comprising one or more elementary antennas.

[0003] In transmission or reception, an antenna assembly is electromagnetically coupled with its environment, such as with another antenna assembly of the antenna or with the metallic plane forming the ground plane of the antenna.

[0004] Two types of coupling can occur: a conducted coupling, which is quantifiable via the S parameters or distribution parameters, at the access level (connectors, for example); a radiated coupling in near field / far field.

[0005] These couplings can be amplified by the physical proximity between antenna assemblies, by their electromagnetic proximity (presence of a common radome, for example), by physical and / or electromagnetic discontinuities (edge ​​effects of the metallic plane, for example), etc.

[0006] These couplings generate undesirable effects such as: an increase in the active standing wave ratio phenomenon - TOS, which corresponds to the combination of the TOS of a given antenna assembly and the couplings of this antenna assembly with the other antenna assemblies of the antenna (the TOS being defined as the modulus of the reflection coefficient of the antenna assembly). This leads to a possible alteration of the characteristics of the radiofrequency chains - RF (generation of instabilities, ripples, etc.), particularly in transmission; an alteration of the quality of the complex radiation pattern in the far field.More specifically, pronounced wave effects are likely to appear at the level of the main lobe of the radiation pattern of the elementary antenna considered with possible impacts: a degradation of the positioning of the main radiation lobe; an alteration of the amplitude and phase of the radiated gain: stronger frequency dependence with possible destructive dips, as well as a strong angular variation of the gain patterns in a given observation plane; an alteration of the angular opening of the main lobe to -3 dB, in the main polarization of the antenna considered; a rise in the radiated gain level in reverse polarization; this rise can be localized in frequency or not and degrades the purity of polarization; a desensitization effect of the reception chain of an antenna operating in reception by a nearby antenna operating simultaneously in transmission.

[0007] It is known to provide a decoupling device between or around an antenna assembly.

[0008] According to a first approach, the metallic plane has corrugations in order to trap electromagnetic waves on its surface.

[0009] Usually, the geometry of the corrugations is based on that of quarter-wave resonators: the depth of the corrugations is approximately λ / 4 ; the width (W) of the corrugations and the gap (g) between two successive corrugations verify the constraint: W + g < λ / 2 Or λ is the wavelength corresponding to the desired operating frequency of the elementary antenna.

[0010] This solution is therefore effective for decoupling antenna assemblies at a given frequency or in the immediate vicinity of it. However, it has the following disadvantages: it operates on a reduced frequency band around the resonance frequency (relative bandwidth of the 15% to 20% class) and outside this bandwidth, the defects linked to the coupling remain present; the thickness of the metallic plane must be greater than the depth of the corrugations and the spacing between the antenna assemblies must be sufficient to be able to position a sufficient number of corrugations to be effective.However, this is sometimes difficult given the constraints of integration on the carrier; for high operating frequencies, the antenna response is sensitive to the precision of mechanical machining of the corrugations; for reasons of mechanical strength (pressure, for example), it may also be necessary to fill the corrugations with a dielectric foam (or with another material (magneto-dielectric), or with the material constituting the radome in the absence of dielectric foam (for example, when the radome is in direct contact with the ground plane). In this case, additional machining constraints appear, with the associated production costs.

[0011] According to a second approach, an electromagnetic absorber - EM - is added to the metallic plane.

[0012] This can be a volume material, for example, based on a magnetic material-resin composite or porous dielectric foam loaded with carbon. This solution can have the advantage of being highly effective in reducing coupling between antenna assemblies over a wide range of incidence. However, it has the following disadvantages: For industrial applications, these materials are commercial products. There is then no degree of freedom (internal constituents of the absorber, loading rate, etc.) to tune the properties of the EM absorber as needed; it is necessary for the material to have sufficient thickness for high decoupling efficiency. The required thickness of the absorber must, classically, be greater than or equal to a quarter of the wavelength in the EM absorber, at the minimum operating frequency.This results in a very thick EM absorber, which is opposed to the constraints of integration on the carrier, where a compact thickness is sought; the electromagnetic characteristics (complex relative permittivity and permeability, in particular) of these EM absorbers are not usually fully controlled by their production process and pronounced inhomogeneities frequently exist between batches of EM absorbers, or even within the same batch of EM absorbers. This is antagonistic to reproducible system performances; the EM absorber must be protected from the external environment, by a compatible radome. However, a radome participates in the coupling that we are trying to attenuate.It also degrades the desired thickness compactness; the low pressure resistance (particularly for flexible materials) and the high mass due to a high volume density (for example, typically greater than or equal to 200 kg / m3 for carbon-impregnated dielectric foams) are penalizing.

[0013] Instead of a bulk material, a 3D structured EM absorber can be used, such as the one presented in the article X. Lleshi, T.Q. Van Hoang, B. Loiseaux and D. Lippens, "Design and Full Characterization of a 3-D-Printed Hyperbolic Pyramidal Wideband Microwave Absorber," in IEEE Antennas and Wireless Propagation Letters, vol. 20, no. 1, pp. 28-32, Jan. 2021, doi: 10.1109 / LAWP.2020.3037718.

[0014] It is obtained by periodization of unit cells. A cell consists of a pyramidal stack of metal / dielectric layers. An EM absorber is usable in X and Ku bands, with an absorptivity at normal incidence greater than 0.95 over 8.2-17.2 GHz (the absorptivity degrades with incidence).

[0015] Such a structure is particularly difficult to achieve since it requires mastering a double metal-dielectric impression. Manufacturing dispersions have a greater impact on the RF performance of the absorber as the working frequency increases.

[0016] The article by Ren J et al., "3D-Printed Low-Cost Dielectric-Resonator-Based Ultra-Broadband Microwave Absorber Using Carbon-Loaded Acrylonitrile Butadiene Styrene Polymer", Materials (Basel), 2018 Jul 20, 11(7),1249, also describes a 3D structured EM absorber obtained by periodization of unit cells. Each cell consists of a base which is topped with a solid cylindrical pad.

[0017] Such a structure is easier to realize than the previous one, but the frequency range over which the absorptivity is high is reduced.

[0018] Furthermore, document CN 114 421 181 A describes a construction material suitable for absorbing ambient electromagnetic waves. This material is formed from a flat electromagnetic wave absorption plate and a plurality of electromagnetic wave absorption units forming a pattern. Each unit has at least one cavity, open from above and delimited laterally by a wall.

[0019] Also known is document US 2017 / 365931 A1 which discloses high impedance surfaces and document US 7,408,500 B2 which discloses a radar antenna for motor vehicles.

[0020] The aim of the present invention is to solve these problems by providing an alternative 3D structured EM absorber type decoupling device having increased efficiency over a wider frequency band.

[0021] For this purpose, the invention relates to an antenna system according to the appended claims.

[0022] The invention and its advantages will be better understood upon reading the following detailed description of a particular embodiment, given solely as a non-limiting example, this description being made with reference to the appended drawings in which: There figure 1 represents, in top view and in axial section, a first embodiment of an antenna; The figure 2 is a perspective representation of the antenna decoupling device of the figure 1 ; There figure 3 represents different alternatives of the shape of the cells of a decoupling device; The figure 4 represents, in top view and in axial section, a second embodiment of an antenna; The figure 5 represents the gains as a function of the bearing of an antenna according to the state of the art and of an antenna according to the second embodiment, for two different frequencies of the frequency range; and, The figure 6 is a perspective representation of the antenna decoupling device according to the invention.

[0023] The subject of the invention relates to an improved electromagnetic - EM decoupling device, arranged between one or more antenna assemblies of an antenna system, making it possible to overcome the defects mentioned above, by eliminating, or at least significantly reducing, conducted and / or radiated couplings.

[0024] The decoupling device is composed of an electromagnetic absorber structured three-dimensionally so as to form a hollow pattern suitable for the absorption of EM waves whatever their angle of incidence.

[0025] There figure 1 represents, in general, a first embodiment of an antenna system.

[0026] In this embodiment, the antenna system 100 comprises a plurality of elementary antennas. Each elementary antenna is a horn antenna. Alternatively, each elementary antenna is an antenna of another type such as for example a Vivaldi antenna or a wide frequency band planar antenna (spiral, sinuous, log-periodic, etc.).

[0027] The horn of each elementary antenna is made in the thickness of the metal plane 105 forming the ground plane of the antenna 100.

[0028] In the embodiment shown, the elementary antennas are arranged in three rows. They bear the references 111, 112, 113 and 114 respectively for the first row, 123, 124 and 125 for the second row, and 131, 132, 133, 134 and 135 for the third row.

[0029] The elementary antennas of the first and second rows form a first antenna assembly 101 and the elementary antennas of the third row form a second antenna assembly 102.

[0030] The antenna system 100 comprises a decoupling device 15, which is, in this embodiment, positioned, between the first and second antenna assemblies, on a front face of the metal plane 105, this front face being oriented towards the transmission / reception half-space of the antenna (i.e. in the normal direction n ).

[0031] The decoupling device has the function of attenuating the main coupling, which, in this first embodiment, is the coupling between the first and second antenna assemblies.

[0032] The decoupling device is preferably arranged so as to be positioned substantially flush with the plane of the openings of the horns.

[0033] The decoupling device 15 consists of a three-dimensionally structured electromagnetic absorber (“3D EM absorber” in the following).

[0034] Advantageously, for protection against external attacks, the antenna system 100 comprises one or more radome(s).

[0035] On the figure 1 , it is a radome 140 common to the different antenna elements, covering the entire front face of the metal plane 105, not only the different antenna assemblies 101 and 102, but also the decoupling device 15.

[0036] Alternatively, only part of the front face of the metal plane is protected by one or more radomes, for example a radome covering each antenna assembly. In this case, the decoupling device is exposed to the environment.

[0037] Advantageously, as shown in the figure 1 , the front face of the metal plane 105 is provided with a recess 107 adapted to the decoupling device 15, the depth of the recess being substantially equal to the height of the decoupling device.

[0038] Alternatively, the decoupling device is integrated into the common radome. It is then carried by a rear face of the radome intended to come opposite the front face of the metal plane.

[0039] There figure 2 represents a possible embodiment of the decoupling device of the antenna system of the figure 1 . This embodiment is not part of the invention.

[0040] The decoupling device 150 consists of a plurality of cells 152 forming a network.

[0041] For example, a cell is parallelepiped in shape, preferably rectangular. The cells are spatially reproduced to form a matrix network of rows and lines of cells.

[0042] Each cell has a base 154 and, on this base, a raised wall 156 shaped according to a hollow pattern.

[0043] Mechanically, a base 154 serves as a support for a raised wall 156, and the different bases allow the decoupling device to be mounted on the metal plane, for example by gluing, or by screwing, or otherwise.

[0044] Electromagnetically, a base is advantageously made of an EM absorbing material, to reinforce the overall effect of the absorption device.

[0045] The patterns formed by the raised walls of the different cells are preferably identical.

[0046] In the embodiment of the figure 2 , the raised wall 1156 comprises an outer frame 157, the sides of which are arranged parallel to the edges of the base 154, and an inner frame 158, which is rotated 45° relative to the outer frame 157 and nested inside the outer frame 157.

[0047] The thicknesses of the outer and inner frames can be similar or different.

[0048] In this document, numerical values ​​are given in order to better understand the invention. However, these values ​​depend in fine the intrinsic electromagnetic properties of the material actually used to make the electromagnetic absorber.

[0049] The characteristic dimensions of a cell are for example the following: the length L 0 of one side of the square base is approximately 0.5 λ 0 , with λ 0 wavelength in vacuum for the minimum frequency from which the absorptivity of the EM absorber is greater than or equal to 0.9; the thickness e 0 of the base is approximately 0.01λ 0 (this is a degree of freedom to increase the absorptivity, but too high a base thickness will, at some point, reduce the absorptivity since we will tend towards a full pattern cell); the length L 1 of the raised wall is slightly smaller than that of the base (L1 ≈ 0.425λ 0 ); the thickness e 1 of the raised wall is approximately 0.1λ 0 (knowing that we are trying to size the absorber so that it is flush with the upper surface of the radiating element when it is positioned around it); the width l 1 of the wall of the square outer frame is approximately 0.0425 λ 0 ; and the width l 2 of the wall of the square inner frame is about 0.0275 λ 0 .

[0050] The base and the raised wall of a cell allow EM waves to be absorbed. In particular, the nesting of several frames (two or more) allows absorption to be improved, in particular by trapping EM waves and this, to the first order, whatever the plane of incidence and the angle of incidence in this plane of incidence (evaluated in relation to the normal direction n ) (there is in fact a degradation of absorptivity with incidence).

[0051] This effect is mainly linked to the multiple absorptions of the EM wave (and its possible multiple reflections) interacting with the different walls, depending on its angle of incidence relative to the normal to the metallic plane.

[0052] Furthermore, it has been found through various tests that this shape allows to broaden the frequency band on which there is effective absorption.

[0053] The materials used for the 3D EM absorber may be thermoplastics with adjuvant, preferably with suitably selected electrical properties, in particular electrostatic dissipative thermoplastics - ESD, such as "ABS ESD", "PEEK ESD", "PEKK ESD", "PEI ESD", "PLA ESD", etc. These are ESDs with particular properties. These are thermoplastics sufficiently loaded with carbon to generate a high dielectric resistivity, but insufficiently loaded with carbon to not become conductive. In the present invention, it is this high resistivity and therefore the corresponding dielectric losses that is used. These thermoplastics are often in the form of wires for 3D printing.

[0054] Alternatively, dielectric or magneto-dielectric materials could be used.

[0055] To structure the 3D EM absorber, it is also possible to combine different materials, such as an interlocking pattern made of ESD thermoplastic and a base with a magneto-dielectric material.

[0056] The decoupling device can be manufactured directly by 3D printing, particularly by co-printing two materials when producing a decoupling device integrated into a radome. In the latter case, for example, a thermoplastic is used for the radome and an ESD thermoplastic for the 3D EM absorber.

[0057] The metal plane (or the radome) is machined so as to provide it with the recess 107 for receiving the decoupling device 150. For assembly, the 3D EM absorber is for example glued to the bottom of this recess. The fact of providing a recess in the metal plane makes it possible to further reduce the thickness of the antenna system, as well as its mass.

[0058] For environmental resistance constraints (pressure, humidity, etc.), the hollowed-out parts of the 3D EM absorber are advantageously filled with a complementary material. For example, it is possible to use an ESD thermoplastic for the EM absorption function and a compatible thermoplastic to secure environmental resistance. Examples of compatible thermoplastics include “ABS”, “PLA”, “PA”.

[0059] Since the complementary material is light, this addition has the advantage of not significantly increasing the mass of the decoupling device, while offering an additional degree of freedom to tune the absorptivity according to the working frequency, as well as to improve the trapping effect of EM waves within the 3D EM absorber.

[0060] The sizing of the cells (in particular the shape of the patterns, dimensions of the patterns in the three directions, thickness of the base and distance between cells) is advantageously optimized by 3D EM simulation with, as a convergence criterion, an absorptivity A preferably greater than or equal to 0.9 in the desired working frequency band (A = 1-|S11| 2< , with |S11| the simulated reflectivity at a given reference plane), which corresponds to a reflectivity less than or equal to -10 dB.

[0061] In the embodiment of the figure 2 (pattern consisting of two square frames at 45° to each other), it is possible to first pre-dimension the sides of the frames knowing the effective electromagnetic properties of the constituent material and then optimize the dimensions of the 3D EM absorber to obtain the desired absorptivity.

[0062] There figure 3 represents different alternative embodiments of the decoupling device of an antenna system. These different embodiments differ only in the shape of the pattern of the cells of the 3D EM absorber of the absorption device. These different embodiments are not part of the invention.

[0063] On the figure 3A , the cell 52 comprises a base 54 and a raised wall 56. The latter is composed of an outer frame 57 in the shape of a square, the sides of which are parallel to the edges of the base, and an inner frame 58 also in the shape of a square, received inside the outer frame, and the sides of which are parallel to the edges of the base.

[0064] On the figure 3B , the cell 152 comprises a base 154 and a raised wall 156. The latter is composed of a square outer frame 157, the sides of which are parallel to the edges of the base, and an inner frame 158 also square, received inside the outer frame, and the sides of which make an angle of 45° with respect to the edges of the base. The corners of the inner frame are merged with the outer frame. This is the embodiment of the figure 2 .

[0065] On the figure 3C , the cell 252 comprises a base 254 and a raised wall 256. The latter is composed of a square outer frame 257, the sides of which form an angle of 45° relative to the edges of the base, and an inner frame 258 also square, received inside the outer frame, and the sides of which are parallel to the edges of the base.

[0066] On the figure 3D , the cell 352 comprises a base 354 and a raised wall 356. The latter is composed of a square outer frame 357, the sides of which form an angle of 45° relative to the edges of the base, and an inner frame 258 also square, received inside the outer frame, and the sides of which form an angle of 45° relative to the edges of the base.

[0067] On the figure 3E , the cell 452 comprises a base 454 and a raised wall 456. The latter is composed of an outer frame 457 in a circular ring, and an inner frame 458 also in a circular ring, received inside the outer frame.

[0068] On the figure 3F , the cell 552 comprises a base 554 and a raised wall, which is composed of a single frame 557, in this case of polygonal shape, in particular hexagonal.

[0069] On the figure 3G , the cell 652 comprises a base 654 and a raised wall 656. The latter is composed of an outer frame 657 in hexagon, and an inner frame 658 also in hexagon, received inside the outer frame and oriented like the outer frame.

[0070] There figure 4 represents a second embodiment of an antenna system.

[0071] In this second embodiment, the antenna system 200 comprises an elementary antenna 211, which is for example a wide frequency band planar antenna. In this second embodiment, it is a dual-polarization sinuous antenna, forming a disk of radius R and thickness E, arranged on the metal plane 205 of the antenna 200.

[0072] The metal plane 205 is here a plate of small thickness compared to that of the radiating element.

[0073] The antenna system 200 comprises a decoupling device 25. It is positioned on the metal plane 205 so as to surround the elementary antenna 211. Advantageously, the front face of the decoupling device is flush with the antenna plane.

[0074] It is for example fixed to the metal plane 205 by means of screws 272 passing through through holes 271.

[0075] The decoupling device 25 has the function of attenuating the main coupling, which is, in this second embodiment, the coupling between the radiating element and the metal plane 205. Indeed, when the antenna assemblies are sufficiently physically separated from each other, the radiated coupling which can exist between them is reduced and the main coupling is that between a given antenna assembly and its close physical environment (metal plane and / or radome). Thus, as a variant, the antenna system could comprise a plurality of elementary antennas, but which would be sufficiently distant from each other so that the main coupling is that between an elementary antenna and the metal plane. It can be said that this second embodiment relates to one or more radiating element(s) isolated from each other.

[0076] The decoupling device 25 is composed of a three-dimensionally structured electromagnetic absorber with a hollow pattern. For example, the decoupling device 25 is structured according to embodiment A of the figure 3 , to within a scale factor, this scale factor being a function of the working frequency range provided for the operation of the antenna system 200. Alternatively, the decoupling device 25 is structured according to another embodiment, any one of the embodiments of the figure 3 or the method of realization of the figure 6 .

[0077] Advantageously, for protection against external attacks, the antenna system 200 comprises one or more radome(s) (not shown in the figure 4 ).

[0078] There figure 5 illustrates the RF response measured on a wide frequency band antenna assembly, by means of two graphs, each graph giving the gain (expressed in isotropic decibels - dBi) radiated according to the bearing angle (expressed in degrees - Deg), at zero elevation angle and in main polarization.

[0079] On each of these graphs, curve C1 corresponds to the antennal device of the figure 1 or that of the figure 4 but without decoupling device and curve C2 corresponds to the antenna device of the figure 1 or that of the figure 4 with decoupling device.

[0080] For example, the first graph corresponds to a frequency F1 close to the frequency FMIN and the second graph corresponds to a frequency F2 close to the frequency FMAX.

[0081] The frequencies FMIN and FMAX are the limits of the useful frequency band of the antenna on which a high absorptivity (for example greater than 0.9) is obtained.

[0082] Those skilled in the art will note an improvement in gain with the implementation of the invention, as well as a stabilization of the gain as a function of the bearing angle (elimination of the gain ripple effect).

[0083] Furthermore, these tests have made it possible to prove the effectiveness of the solution over a wide frequency range. Compared to the state of the art presented in the article by Ren J. et al., whose useful frequency band has an FMAX / FMIN ratio of 3, the solution proposed here allows an absorptivity of at least 0.9 over a very wide useful band, typically with an FMAX / FMIN ratio of 10.

[0084] There figure 6 represents an embodiment, in accordance with the invention, of a decoupling device, whether it is the device 15 of the antenna system of the figure 1 or device 25 of the antenna system of the figure 4 .

[0085] On the figure 6 , the decoupling device 750 consists of a plurality of cells 752 forming a network.

[0086] For example, a cell is parallelepiped in shape, preferably rectangular. The cells are spatially reproduced to form a matrix network of rows and lines of cells.

[0087] Each cell has a base 754 and, on this base, a raised wall 756 shaped according to a hollow pattern.

[0088] The patterns formed by the raised walls of the different cells are preferably identical.

[0089] In this embodiment, a raised wall 756 is composed of an outer frame 757 and an inner frame 758.

[0090] The outer frame 757 is provided, on its periphery, with at least one lug projecting radially towards the outside of the outer frame 757, that is to say towards the neighboring cells.

[0091] For example, the outer frame 757 is square in shape.

[0092] Each of the vertices of the outer frame 757 is provided with a corner lug 755. A corner lug comes into contact with one or more corner lugs carried by the outer frames of cells adjacent to the cell in question.

[0093] Alternatively or in combination, each of the sides of the outer frame 757 is provided with a central lug 755. A central lug comes into contact with a central lug carried by the outer frame of the adjacent cell opposite the cell in question so as to form a connection between these outer frames of neighboring cells.

[0094] Alternatively or in combination with the preceding variants, the inner frame 758 is also provided with at least one lug projecting radially outwards from the inner frame 758 towards the neighbouring frame, i.e. towards the outer frame 757 of the cell in question.

[0095] For example, on the figure 6 , the inner frame 758 is square in shape.

[0096] Each of the vertices of the inner frame 757 is provided with a corner lug 759. A corner lug comes into contact with the outer frame, for example the corner of the outer frame.

[0097] Alternatively or in combination, the inner frame could carry central lugs forming as many connections with the outer frame of the same cell.

[0098] The lugs of the different cells make it possible to close the channels between facing walls, such as for example channel 760 between two rows of cells, channel 761 between two lines of cells, or like channel 762 between the inner wall of the outer frame 757 and the outer wall of the inner frame 758 of the same cell.

[0099] This helps trap electromagnetic waves, especially creeping waves, which would otherwise risk propagating along such channels.

[0100] In fact, the level of trapping of creeping waves is improved by increasing the height of the frames above the base. The presence of lugs makes it possible to achieve the same level of trapping, but without increasing the height. In other words, for the same height of the raised wall, the presence of lugs makes it possible to significantly increase the trapping of creeping waves.

[0101] In this regard, an increase in the base thickness would lead to a degradation of the reflectivity. The proposed invention allows a compromise between the desired reflectivity (typically less than -10 dB) over a wide frequency band, while trapping creeping waves (between unit cells, at the absorber-metal plane interface).

[0102] Thus, the decoupling device according to the invention is particularly effective while remaining thin.

[0103] More generally, the level of electromagnetic wave trapping sought for a decoupling device results from a compromise between the sizing of the lugs (jointed versus non-jointed) and the height of the frames constituting the raised wall.

[0104] Alternatively, a gap is left between a lug and either the neighboring lug(s) or the neighboring frame. The corresponding channel is then not closed (case where the lugs are contiguous) but has a narrowing (case where the lugs are not contiguous).

[0105] Alternatively, a frame adopts a polygonal shape other than a simple square (e.g., a hexagon as in the embodiment of the figure 3G ), the frames are nested but with a different orientation (for example with a 45° rotation, as in the embodiment of the figure 3C ), and / or with different heights.

[0106] While the lugs are preferably made of the same material as the raised wall, alternatively the lugs are added and may therefore not be made of the same material as that forming the absorbent unit cells.

[0107] In yet another variant, a lug exhibits an absorption gradient. This is achieved, for example, by varying the volumetric loading rate of the material used or by multi-material printing.

[0108] Depending on the creeping wave hotspots (identifiable by calculating the Poynting vector or electromagnetic energy density at different points), this gradient can be associated with a variation in the thickness and width of the lug.

[0109] According to the invention, the decoupling device is composed of a three-dimensionally structured electromagnetic absorber which is effective over a wide range of frequencies, compact in thickness, of low mass, and with controlled dispersion, while being passive.

Claims

1. Antenna system (100) including at least one elementary antenna (125), a metal plane (105) provided around the elementary antenna, and a decoupling device (750) arranged on the metal plane, the decoupling device being of a three-dimensional electromagnetic absorption structure consisting of a plurality of cells arranged in an array, each cell (752) including, stacked along a direction normal to the metal plane, a base (754) and a raised wall(756) on top of the base, the antenna system being characterized in that the raised wall is shaped to form a recessed pattern for trapping electromagnetic waves, the recessed pattern consisting of a plurality of frames (757, 758) interlocked one inside the other, and in that at least one frame of each pattern is provided with at least one lug (755, 759), said at least one lug extending laterally away from the frame and cooperating with an adjacent frame of the same cell or of an adjacent cell, in order to close, at least partially, a channel between the frame and said adjacent frame.

2. Antenna system according to claim 1, wherein the recessed pattern includes an outer frame (757) and an inner frame (758), the outer frame having a shape selected from among: a square, a rectangle, a ring, or a polygon, and the inner frame having a shape selected from: a square, a rectangle, a ring, or a polygon.

3. Antenna system according to any one of the previous claims, wherein : a side of the base is about 0.5λ0; a thickness of the base is about 0.01λ0; an extension, characteristic of the raised wall is about 0.425λ0; a thickness of the raised wall is about 0.1λ0; a width of the raised wall is between about 0.0425λ0 and about 0.0275λ0, where λ0 is a wavelength in vacuum for a minimum frequency from which an absorptivity of the decoupling device is greater than or equal to 0.9.

4. Antenna system according to any one of the previous claims, wherein the material of the base and / or the raised wall is a thermoplastic with additive, preferably a statically dissipative thermoplastic.

5. Antenna system according to any one of the previous claims, wherein the cells are identical to each other.

6. Antenna system according to any one of the previous claims, wherein the decoupling device is arranged between two elementary antennas (125, 135) for attenuation of a coupling between said two elementary antennas or around one elementary antenna for attenuation of a coupling between said elementary antenna and the metal plane (205).

7. Antenna system according to any one of the previous claims, wherein the metal plane (150) is provided with a recess (107) for receiving the decoupling device (750).

8. Antenna system according to any one of the previous claims, including at least one radome (140).

9. Antenna system according to claim 8, wherein the decoupling device is integrated into the radome.

10. Antenna system according to any one of the previous claims, wherein a recessed portion of one cell of the decoupling device is filled with a material complementary to, and preferably compatible with, the material used for the base and the raised wall of said cell.

11. Antenna system according to any one of the previous claims, wherein the elementary antenna is a horn antenna, a Vivaldi antenna, or a wide frequency band planar antenna, such as a spiral, sinuous, or log-periodic antenna.