Improved antenna system and associated decoupling device

Abstract

Improved Antenna System and Associated Decoupling Device This antenna system comprises at least one elementary antenna, a metal plane provided around the elementary antenna, and a decoupling device (150) disposed on the metal plane. The decoupling device is of the type three-dimensional electromagnetic absorption structure consisting of a plurality of cells arranged in a lattice. Each cell (152) comprises, stacked in a direction normal to the metal plane, a base (154) surmounted by a raised wall. The antenna system is characterized in that the raised wall (156) is shaped to form a hollow pattern for trapping electromagnetic waves. Figure for the abbreviation: Figure 3

Description

Title of the invention: Improved antenna system and associated decoupling device

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

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

[0003] In transmission or reception, an antenna assembly is electromagnetically coupled with its environment, such as for example 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:

[0005] - a conducted coupling, which is quantifiable via the S parameters or parameters of re partition, at the access level (connectors, for example);

[0006] - a near-field / far-field radiated coupling.

[0007] 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 metal plane, for example), etc.

[0008] These couplings generate undesirable effects such as:

[0009] - a rise in the standing wave rate phenomenon - active 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 -RF chains (generation of instabilities, ripples, etc.), particularly in transmission;

[0010] - an alteration in the quality of the complex radiation pattern in the 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 level of radiated gain in reverse polarization; this rise can be localized in frequency or not and degrading the purity of polarization;

[0011] - a desensitization effect of the reception chain of an antenna operating in reception by a nearby antenna operating simultaneously in transmission.

[0012] It is known to provide a decoupling device between or around an antenna assembly.

[0013] According to a first approach, the metallic plane has corrugations in order to trap electromagnetic waves on the surface of the latter.

[0014] Usually, the geometry of the corrugations is based on that of the quarter-wave resonators: the depth of the corrugations is about 2 / 4; the width (W) of the corrugations and the gap (g) between two successive corrugations verify the constraint: W + g < À / 2

[0015] where 2 is the wavelength corresponding to the desired operating frequency of the elementary antenna.

[0016] This solution is therefore effective for decoupling antenna assemblies at a given frequency or in the immediate vicinity thereof. However, it has the following drawbacks:

[0017] - it operates on a reduced frequency band around the frequency of resonance (relative bandwidth of the 15% to 20% class) and outside this bandwidth, coupling-related defects remain present;

[0018] - the thickness of the metal 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;

[0019] - for high operating frequencies, the antenna response is sensitive to the precision of mechanical machining of corrugations;

[0020] - for reasons of mechanical strength (pressure, for example), it is also possible that the corrugations must be filled with dielectric foam (or 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.

[0021] According to a second approach, an electromagnetic absorber - EM - is added to the metallic plane.

[0022] This may be a volume material, for example, based on a magnetic material-resin composite or porous dielectric foam loaded with carbon. This solution may 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:

[0023] - for industrial applications, these materials are commercial products. It there is then no degree of freedom (internal constituents of the absorbent, charge rate, etc.) to adjust the properties of the EM absorbent as needed;

[0024] - it is necessary that the material has sufficient thickness for a strong ef decoupling efficiency. The required absorber thickness must, classically, be greater than or equal to a quarter wavelength in the EM absorber, at the minimum operating frequency. This results in a very thick EM absorber, which opposes the constraints of integration on the carrier, where compactness of thickness is sought;

[0025] - the electromagnetic characteristics (relative permittivity and permeability complex, in particular) of these EM absorbents are usually not fully controlled by their production process and pronounced inhomogeneities frequently exist between batches of EM absorbents, or even within the same batch of EM absorbents. This is antagonistic to reproducible system performances;

[0026] - the EM absorber must be protected from the external environment, by a radome compatible. However, a radome participates in the coupling that we are trying to attenuate. It also degrades the desired thickness compactness;

[0027] - the low pressure resistance (especially for flexible materials) and the mass high due to a high volume density (for example, typically greater than or equal to 200 kg / m3 for carbon-impregnated dielectric foams) are penalizing.

[0028] 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.

[0029] It is obtained by periodization of unit cells. A cell consists of a pyramidal stack of metal / dielectric layers. An EM absorber can be used 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).

[0030] Such a structure is particularly difficult to produce since it is necessary to control a double metal-dielectric impression. The manufacturing dispersions impact the RF performance of the absorber all the more as the working frequency is high.

[0031] 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.

[0032] Such a structure is easier to produce than the previous one, but the frequency range over which the absorptivity is high is reduced.

[0033] The aim of this 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.

[0034] For this purpose, the invention relates to an antenna system comprising at least one elementary antenna, a metal plane provided around the elementary antenna, and a decoupling device arranged on the metal plane, the decoupling device being of the three-dimensional electromagnetic absorption structure type consisting of a plurality of cells arranged in a network, each cell comprising, stacked in a direction normal to the metal plane, a base surmounted by a raised wall, the antenna system being characterized in that the raised wall is shaped so as to form a hollow pattern for trapping electromagnetic waves.

[0035] According to particular embodiments, the antenna comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations:

[0036] - the hollow pattern is made up of several nested frames.

[0037] - the hollow pattern has an outer frame and an inner frame, the outer frame having a shape selected from: 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.

[0038] - one side of the base is about 0.5X0; one thickness of the base is about 0.01X0; according to the plane of the base, a characteristic extension of the raised wall is about 0.425Xo; a thickness of the raised wall is about 0.1Xo; a width of the raised wall is between about 0.0425Xo (for the outer frame) and about 0.0275Xo (for the inner frame), where Xo is the wavelength in vacuum for the minimum frequency from which the absorptivity of the electromagnetic absorber is greater than or equal to 0.9.

[0039] - the material of the base and / or the raised wall is a thermoplastic with adjuvant, preferably a static dissipative thermoplastic.

[0040] - the raised wall of a cell has a lug capable of cooperating with a lug of the raised wall of a neighboring cell, in order to block, at least partially, a channel formed between the raised walls of the cell and the neighboring cell.

[0041] - the cells are identical to each other.

[0042] - the decoupling device is arranged between two elementary antennas for a attenuation of a coupling between said two elementary antennas or around an elementary antenna for an attenuation of a coupling between said ele- mental and the metal plan.

[0043] - the metal plane is provided with a recess for receiving the device of coupling.

[0044] - the system comprises at least one protective radome.

[0045] - the decoupling device is integrated into the radome.

[0046] - a hollowed-out portion of the pattern of a cell of the decoupling device is filled of a complementary material, preferably compatible with the material used for the base and the raised wall of said cell.

[0047] - the elementary antenna is a horn antenna, a Vivaldi antenna, or an antenna wide-bandwidth planar antenna, such as a spiral, meandering, or log-periodic antenna.

[0048] The invention also relates to a decoupling device suitable for integration into the preceding antenna system.

[0049] The invention and its advantages will be better understood on reading the detailed description which follows of a particular embodiment, given solely by way of non-limiting example, this description being made with reference to the appended drawings in which:

[0050] [Fig-1] [Fig. 1] represents in top view and in axial section a first mode of production of an antenna according to the invention;

[0051] [Fig.2] [Fig.2] is a perspective representation of the decoupling device of the antenna of [Fig.l];

[0052] [Fig.3] [Fig.3] represents different possible embodiments of a cell of the decoupling device according to the invention;

[0053] [Fig.4] [Fig.4] represents, in top view and in axial section, a second mode of production of an antenna according to the invention; and,

[0054] [Fig.5] [Fig.5] represents the gains as a function of the bearing of an antenna according to the state of the art and an antenna according to the invention, for two different frequencies of the frequency range.

[0055] The subject of the invention relates to an electromagnetic - EM decoupling device 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, the conducted and / or radiated couplings.

[0056] According to the invention, the decoupling device is composed of an electromagnetic absorber structured three-dimensionally so as to form a hollow pattern adapted to the absorption of EM waves whatever their angle of incidence.

[0057] [Fig.l] represents a first embodiment of an antenna system according to the invention.

[0058] 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.).

[0059] The horn of each elementary antenna is made in the thickness of the metal plane 105 forming the ground plane of the antenna 100.

[0060] In the embodiment shown, the elementary antennas are arranged in three rows. They respectively bear the references 111, 112, 113 and 114 for the first row, 123, 124 and 125 for the second row, and 131, 132, 133, 134 and 135 for the third row.

[0061] 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.

[0062] The antenna system 100 comprises a decoupling device 150, 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).

[0063] 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.

[0064] The decoupling device is preferably arranged so as to be positioned substantially flush with the plane of the openings of the horns.

[0065] The decoupling device 150 consists of a three-dimensionally structured electromagnetic absorber (“3D EM absorber” in the following), which will be described in detail with reference to [Fig.2].

[0066] Advantageously, for protection against external attacks, the antenna system 100 comprises one or more radome(s).

[0067] In [Fig.l], this 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 150.

[0068] Alternatively, only a portion 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.

[0069] Advantageously, as shown in [Fig.l], the front face of the metal plane 105 is provided with a recess 107 adapted to the decoupling device 150, the depth of the recess being substantially equal to the height of the decoupling device.

[0070] 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.

[0071] [Fig.2] more specifically represents the decoupling device 150 of the antenna system of [Fig.l].

[0072] The decoupling device 150 consists of a plurality of cells 152 forming a network.

[0073] For example, a cell is parallelepiped in shape, preferably rectangular. The cells are spatially reproduced so as to constitute a matrix network of rows and lines of cells.

[0074] Each cell comprises a base 154 and, on this base, a raised wall 156 shaped according to a hollow pattern.

[0075] 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.

[0076] Electromagnetically, a base is advantageously made of an EM absorbing material, to reinforce the overall effect of the absorption device.

[0077] The patterns formed by the raised wall of the different cells are preferably identical.

[0078] In the embodiment of [Fig.2], the raised wall 156 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.

[0079] The thicknesses of the outer and inner frames may be similar or different.

[0080] In this document, numerical values ​​are given in order to better understand the invention. However, these values ​​ultimately depend on the intrinsic electromagnetic properties of the material actually used to make the electromagnetic absorber.

[0081] The characteristic dimensions of a cell are for example the following: the length Lo of one side of the square base is approximately 0.5X0, with Xo 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 e0 of the base is approximately 0.01X0 (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 cell with a full pattern); the length Li of the raised wall is slightly smaller than that of the base (L1 ~ 0.425Xo); the thickness ei of the raised wall is approximately 0.1Xo (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 li of the wall of the square outer frame is about 0.0425Xo; and the width 12 of the wall of the square inner frame is about 0.0275Xo.

[0082] The base and the raised wall of a cell make it possible to absorb EM waves. In particular, the nesting of several frames (two or more) makes it possible to improve absorption, 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 with respect to the normal direction n) (there is in fact a degradation of the absorptivity with the incidence).

[0083] 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.

[0084] Furthermore, it has been found by various tests that this shape makes it possible to broaden the frequency band over which there is effective absorption.

[0085] The materials used for the 3D EM absorber may be thermoplastics with adjuvant, preferably with suitably selected electrical properties, in particular static dissipative thermoplastics - ESD (electrostatic dissipative thermoplastics), such as for example "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 so as not to become conductive. In the present invention, it is this high resistivity and therefore the corresponding dielectric losses which is used. These thermoplastics are often in the form of wires for 3D printing.

[0086] Alternatively, dielectric or magneto-dielectric materials could be used.

[0087] To structure the 3D EM absorber, it is also possible to combine different materials, such as for example an interlocking pattern in ESD thermoplastic and a base with a magneto-dielectric material.

[0088] The decoupling device can be manufactured directly by 3D printing, in particular 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.

[0089] 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.

[0090] For environmental resistance constraints (pressure, humidity, etc.), the parts The hollowed-out sections 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".

[0091] The complementary material being 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.

[0092] The sizing of the cells (in particular 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 convergence criterion, an absorptivity A preferably greater than or equal to 0.9 in the desired working frequency band (A = 1-IS1 112, with IS11I the simulated reflectivity at a given reference plane), which corresponds to a reflectivity less than or equal to -10 dB.

[0093] In the embodiment of [Fig.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 to optimize the dimensions of the 3D EM absorber to obtain the desired absorptivity.

[0094] [Fig.3] represents different possible shapes of the pattern of the cells of the 3D EM absorber of the absorption device according to the invention.

[0095] In 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.

[0096] In 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 Figures 1 and 2.

[0097] In 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 whose sides are parallel to the edges of the base.

[0098] In Figure 3D, the cell 352 comprises a base 354 and a raised wall 356. The latter is composed of a square outer frame 237, the sides of which make an angle of 45° relative to the edges of the base, and an inner frame 238 also square, received inside the outer frame, and the sides of which make an angle of 45° relative to the edges of the base.

[0099] In 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.

[0100] In 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.

[0101] In Figure 3G, the cell 652 comprises a base 654 and a raised wall 656. The latter is composed of an outer frame 357 in the shape of a hexagon, and an inner frame 658 also in the shape of a hexagon, received inside the outer frame and oriented like the outer frame.

[0102] In Figure 3H, the cell 752 comprises a base 754 and a raised wall 756. The latter is composed of an outer frame 757 and an inner frame 758. The outer frame is provided with lugs 755 projecting radially towards the neighboring cells. For example, the outer frame is square in shape. Each of its vertices is provided with a lug 755, which extends towards the corresponding corner of the base 754. A lug comes into contact with one or more lugs carried by the cells adjacent to the cell in question.

[0103] The lugs of the different cells make it possible to close one end of a channel (such as for example channel 159 of [Fig.2]) extending between the side of the outer frame of a cell and the opposite side of the outer frame of an adjacent cell.

[0104] This makes it possible to trap electromagnetic waves which would otherwise risk propagating along a string of such channels according to the ranks and / or lines of the network formed by the cells of the decoupling device.

[0105] Alternatively, a gap is provided between a lug and the neighboring lug(s).

[0106] It should be noted that other types of cell can be considered, for example, based of honeycombs and that the lengths and widths of the nested patterns can be different. For example, rectangular patterns can be considered.

[0107] [Fig.4] represents a second embodiment of the antenna system according to the invention.

[0108] In this second embodiment, the antenna system 200 comprises an antenna elementary antenna 211, which is for example a wide frequency band planar antenna. In this second embodiment, it is a sinuous antenna with dual polarization, forming a disk of radius R and thickness E, arranged on the metallic plane 205 of the antenna 200.

[0109] The metal plane 205 is here a plate of small thickness compared to that of the radiating element.

[0110] The antenna system 200 comprises a decoupling device 250. 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.

[0111] It is for example fixed to the metal plane 205 by means of screws 272 passing through through holes 271.

[0112] The decoupling device 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.

[0113] The decoupling device 250 is composed of a three-dimensionally structured electromagnetic absorber with a hollow pattern. A cell 52 of the decoupling device 250 is identical to that of the embodiment A of [Fig. 3], except for a scale factor, this scale factor being a function of the working frequency range intended for the operation of the antenna system 200. Alternatively, the decoupling device is structured according to any one of the alternatives shown in [Fig. 3].

[0114] Advantageously, for protection against external attacks, the antenna system 200 comprises one or more radome(s) (not shown in [Fig.4]).

[0115] [Fig.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.

[0116] On each of these graphs, curve C1 corresponds to the antenna device of [Fig.l] or to that of [Fig.4] but without the decoupling device according to the invention and curve C2 corresponds to the antenna device of [Fig.l] or to that of [Fig.4] with the decoupling device according to the invention.

[0117] For example, the first graph corresponds to a frequency Fl close to the frequency FMIN and the second graph corresponds to a frequency F2 close to the frequency FMAX.

[0118] 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.

[0119] Those skilled in the art will note an improvement in the gain with the implementation of the invention, as well as a stabilization of the latter as a function of the bearing angle (elimination of the gain ripple effect).

[0120] Furthermore, these tests have made it possible to prove the effectiveness of the solution over a wide range of frequencies. 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.

[0121] 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

Claims

1. Antenna system (100) comprising at least one elementary antenna (125), a metal plane (105) provided around the elementary antenna, and a decoupling device (150) arranged on the metal plane, the decoupling device being of the three-dimensional electromagnetic absorption structure type consisting of a plurality of cells arranged in a network, each cell (152) comprises, stacked in a direction normal to the metal plane, a base (154) surmounted by a raised wall, the antenna system being characterized in that the raised wall is shaped so as to form a hollow pattern for trapping electromagnetic waves.

2. An antenna system according to claim 1, wherein the hollow pattern consists of a plurality of nested frames (157, 158).

3. The antenna system of claim 2, wherein the recessed pattern comprises an outer frame (157) and an inner frame (158), the outer frame having a shape selected from: 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.

4. An antenna system according to any preceding claim, wherein: a side of the base is about 0.5Xo; a thickness of the base is about 0.01X0; a characteristic extension of the raised wall is about 0.425Xo; a thickness of the raised wall is about 0.1Xo; a width of the raised wall is between about 0.0425Xo and about 0.0275Xo, where Xo is the wavelength in vacuum for the minimum frequency of the working frequency band of the antenna system, minimum frequency from which the absorptivity of the electromagnetic absorber is greater than or equal to 0 Q

5. An antenna system according to any preceding claim, wherein the material of the base and / or raised wall is a thermoplastic with additive, preferably a static dissipative thermoplastic.

6. An antenna system according to any one of the preceding claims, wherein the raised wall (756) of a cell (752) comprises a lug (755) capable of cooperating with a lug of the raised wall of a neighboring cell, in order to close, at least partially, a channel (159) formed between the raised walls of the cell and the cell neighbor.

7. An antenna system according to any preceding claim, wherein the cells are identical to each other.

8. Antenna system according to any one of the preceding claims, in which the decoupling device (150) is arranged between two elementary antennas (125, 135) for attenuation of a coupling between said two elementary antennas or around an elementary antenna (211) for attenuation of a coupling between said elementary antenna and the metal plane (205).

9. Antenna system according to any one of the preceding claims, in which the metal plane (150) is provided with a recess (107) for receiving the decoupling device (150).

10. An antenna system according to any preceding claim, comprising at least one radome (140).

11. An antenna system according to claim 10, wherein the decoupling device is integrated into the radome.

12. An antenna system according to any preceding claim, wherein a recessed portion of the pattern of a cell of the decoupling device is filled with a complementary material, preferably compatible with the material used for the base and the raised wall of said cell.

13. An antenna system according to any preceding claim, 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.

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