WO2015136121A1

WO2015136121A1 - Multi-sector absorbing method and device

Info

Publication number: WO2015136121A1
Application number: PCT/EP2015/055460
Authority: WO
Inventors: Nicolas CAPET; Yenny PINTO BALLESTEROS; Anne-Claire LEPAGE; Julien Sarrazin; Xavier Begaud
Original assignee: Centre National D'etudes Spatiales; Institut Mines-Telecom
Priority date: 2014-03-14
Filing date: 2015-03-16
Publication date: 2015-09-17
Also published as: EP3117486A1; FR3018638A1; FR3018638B1

Abstract

The invention relates to a device (1) for absorbing electromagnetic waves, comprising a plurality of arrays (E_i) each comprising at least one cell (2) for absorbing electromagnetic waves, characterised in that: each array (Ei) has a minimum absorption coefficient valid for given parameters of the waves incident on said array (Ei), said parameters comprising one or more of the following parameters: - a pair of angular ranges ([θ_i-θ'_i],[φ_i-φ_i']) of the direction of arrival of the incident waves on the array (Ei), comprising a range ([θ_i-θ'_i]) of angles of incidence and a range of azimuthal angles ([φ_i-φ_i']), and - a polarisation of the incident waves, the parameters of the incident waves for which each array (Ei) ensures the minimum absorption coefficient being different from one array (Ei) to the other. The invention also relates to a method for designing and producing an absorbing device.

Description

Multi-sector absorption device and method

Field of the invention

The invention relates to an electromagnetic wave absorption device and to a method for designing and producing an electromagnetic wave absorption device.

Presentation of the prior art

In an environment comprising a source emitting electromagnetic waves, disturbances are created due to the reflections and multipaths of said electromagnetic waves.

This is for example the case of an antenna mounted on a supporting structure. The electromagnetic waves emitted by the antenna are reflected on the carrier structure and disturb the radiation pattern of the antenna.

In other cases, the electromagnetic waves emitted by the source must not reach certain areas for which they would be harmful (hospital, school, etc.).

In the prior art, it is known to use absorption devices, or absorbers, which are materials that absorb incident waves.

Different technologies of absorbents have been described in the prior art, such as the Salisbury screen, comprising a resistive layer (or more generally, a lossy material) placed above a metal surface at a distance d a quarter of a wavelength, or structures based on metamaterials. Structures based on metamaterials are periodic and consist of one or more repeating patterns.

However, the absorption devices of the prior art have drawbacks.

Due to the variety of the nature of the incident waves on these devices, the performances obtained for the absorption are not satisfactory for all the incident waves. These limited performances therefore do not make it possible to fight effectively against unwanted reflections or multipath waves. Presentation of the invention

In order to overcome the drawbacks of the prior art, the invention proposes an electromagnetic wave absorption device, comprising a plurality of assemblies each comprising at least one electromagnetic wave absorption cell, characterized in that each set has a minimum absorption coefficient valid for given parameters of the incident waves on said set, said parameters comprising one or more of the following parameters: a pair of angular arrival direction ranges of the incident waves on the set, comprising a range of angles of incidence and range of azimuth angles, (or a solid angle containing the arrival directions of the incident waves), the polarization (s) of the incident waves, the parameters of the incident waves for which each set provides the minimum absorption coefficient being different from one set to another.

The invention is advantageously completed by the following features, taken alone or in any of their technically possible combination:

said parameters furthermore comprise a frequency range of the incident waves;

the assemblies are arranged in concentric crowns; the sets are arranged in a polygonal plane

(hexagonal, square ...), or on faces of a three-dimensional form (pyramid);

the device comprises cells whose absorption plane is dimensioned so that a portion of the plane in a first direction is sized to absorb the incident waves having a first polarization, and that a portion of the plane in a second direction is sized to absorb the waves incidental with a second polarization different from the first.

The invention also relates to an assembly comprising a source emitting and / or receiving electromagnetic waves, and an absorption device being configured to absorb electromagnetic waves from the source and / or towards the source, each set of cells having a minimum absorption coefficient valid for one or more of said incident wave parameters transmitted by the source to said set.

The invention also relates to a method for designing and producing an absorption device, for a zone of an environment to which electromagnetic waves are directed, characterized in that it comprises the steps of:

identifying parameters of the incident waves on the zone, said parameters comprising one or more of:

a pair of angular arrival direction ranges of the incident waves on the assembly, comprising a range of angles of incidence and a range of angles of azimuth, and

a polarization of the incident waves,

- cutting the zone into a plurality of elementary zones, and for each elementary zone, producing an assembly comprising at least one electromagnetic wave absorption cell, said assembly having a minimum absorption coefficient valid for one or more of the wave parameters incidental on said elementary zone. The invention is advantageously completed by the following features, taken alone or in any of their technically possible combination:

the parameters of the incident waves furthermore comprise a frequency range of the incident waves; the method comprises the step of assembling the sets of absorption cells, so as to obtain an absorption device for the zone;

the method comprises the steps of simulating or measuring the electromagnetic wave radiation performance of the source with the device in the zone, comparing the performance with specifications, and, in case of non-compliance, redrawing the zone into elementary zones finer, then make sets for these finer elemental areas;

the process comprises:

for an environment comprising at least one source emitting and / or receiving electromagnetic waves, identifying zones of disturbance, or subjected to disturbances, due to the electromagnetic waves emitted by the source or arriving at the source,

o carrying out one or more absorption devices for said zones,

placing said absorption devices at said zones.

The invention has many advantages.

The invention proposes an absorption device for a zone subjected to electromagnetic disturbances, the performances of which are optimized for the different waves incident on this zone.

In particular, the invention makes it possible to obtain satisfactory absorption performance even though the incident waves have different parameters to each other, such as the angle of incidence, the azimuth angle, the polarization, or the frequency.

Finally, the invention offers a scalable and scalable absorption device depending on the environment. Presentation of figures

Other features and advantages of the invention will become apparent from the description which follows, which is purely illustrative and nonlimiting, and should be read with reference to the accompanying drawings in which:

- Figure 1 is a representation of an embodiment of an absorption device according to the invention;

- Figure 2 is a representation of a spherical landmark;

Figure 3 is a representation of an embodiment of an absorption cell;

Figure 4 is a representation of another embodiment of an absorption cell;

- Figure 5 is a representation of an embodiment wherein the absorption assemblies are arranged in concentric rings;

FIG. 6 shows the example of FIG. 4 and illustrates the concentric absorption sets adapted for different ranges of incidence angles;

Figure 7 is a variant of Figure 5 with an off-center source;

Figure 8 illustrates concentric absorption assemblies adapted for different angles of incidence and azimuth ranges;

Fig. 9 depicts steps of a method for designing and producing a system comprising an electromagnetic source, wherein the method of designing and producing an absorption device can register;

- Figure 10 describes steps of an embodiment of a method of designing and producing an absorption device;

- Figure 1 1 describes steps of an embodiment of a method of designing and producing an absorption device, comprising steps of performance simulation; Figures 12 to 15 are examples of application of the device and the method of absorption.

detailed description

Device

FIG. 1 schematically shows an embodiment of an electromagnetic wave absorption device 1.

This device 1 comprises a plurality of sets E, (in Figure Ei, E ₂ and E ₃ ) each comprising at least one cell 2 for absorbing electromagnetic waves.

Thus, each set Ei may comprise a single electromagnetic wave absorption cell 2, or a plurality of electromagnetic wave absorption cells 2.

As explained later, different technologies can be used for the cells 2, so that they can provide an absorption function of incident electromagnetic waves.

The cells 2 of a set Ei have a minimum absorption coefficient, valid for given parameters of the incident waves on said set Ei.

The absorption coefficient is usually expressed in dB. This absorption coefficient is defined according to the desired specifications, which depend on the context and the mission.

This absorption coefficient also depends on the technologies used for the cells. A typical value is between -15dB and -10dB.

Depending on the application, the value of the minimum absorption coefficient may be common to all sets, or be specific to each set.

The parameters of the incident waves, for which each set Ei provides the minimum absorption coefficient for the waves incidental on said set may include at least one of the following parameters:

at least one angular range ([θ, -θ'ί], [φί-φί ']) of direction of arrival of the incident waves on the assembly. This angular range can also be defined by a solid angle of arrival direction of the incident waves on the assembly. In one embodiment, a pair of angular ranges is taken into account, comprising both a range of angles of incidence [θ, -θ ',] and a range of azimuth angles [φί-φί'] ;

a polarization of the incident waves;

if necessary, the parameters may furthermore include a frequency range of the incident waves. Indeed, in some cases, the sets Ei of cells receive incident waves belonging to different frequency ranges. Therefore, each set Ei ensures in this case the minimum absorption coefficient for the range of frequencies specific to it, besides the parameters already mentioned above (angles of arrival direction, and / or polarization ...).

As can be seen for example in FIG. 7, the incident waves on the device 1 have a direction of arrival whose angular definition, in a given reference, is different according to the sets Ei of the device 1.

The angular range of arrival direction typically includes:

a range of angles of incidence [θ, -θ ',], the angle of incidence Θ being the angle between the normal to the surface of the assembly Ei of the absorbing device and the incident electromagnetic wave;

a range of azimuth angles [cpi-cpi '], the azimuth angle φ being defined by the choice of a spherical coordinate system consistent with the definition of the angle Θ previously defined (see FIG. .

Thus, in one embodiment, a pair of angular ranges ([θί-θ'ί], [φ, -φ,]]) of direction of arrival of the incident waves on the set Ei, comprising both the range of angles of incidence [θ, -θ ',] and the range of azimuth angle [φί-φ,'], is taken into account.

Taking into account both the range of angles of incidence and the range of azimuth angle is advantageous, especially when the angle of incidence is moving away from the normal to the incident set Ei, to increase the performance of the absorption.

Taking into account the pair of arrival direction angular ranges can in particular give rise to the formation of anisotropic absorption cells 2.

In the same way, the incident waves have, according to the emission sources, different polarizations.

Examples of polarization include:

the transverse electric polarization (TE) for which the electric field vector of the incident wave is tangent to the absorption surface of the set Ei, and the magnetic field is contained in the plane orthogonal to the electric field vector;

the transverse magnetic polarization (TM) for which the magnetic field vector of the incident wave is tangent to the absorption surface of the set Ei, and the electric field is contained in the plane orthogonal to the magnetic field vector.

In the device 1, the parameters of the incident waves for which each set E, ensures the minimum absorption coefficient are different from one set Ei to the other. This implies that at least one of the parameters, or all the parameters, is different from one set Ei to the other.

This makes it possible to obtain a discretization of the absorption space, each set of cells being adapted to the specific parameters of the waves incident on said set. For a given electromagnetic source, the device 1 makes it possible to optimize the absorption, by means of specific cell sets for each geographical zone.

The device 1 is therefore configured to absorb the electromagnetic waves emitted and / or received by the source 15, each set Ei of cells having a minimum absorption coefficient valid for the parameters of the incident waves to said set Ei.

For a given electromagnetic source, the device 1 is made with a plurality of sets adapted to the parameters of the incident waves on said set.

FIG. 3 shows a possible embodiment of an electromagnetic wave absorption cell 2.

The cell 2 comprises a ground plane 10, an incident wave absorption plane 12, and a spacer 11 disposed between the ground plane 10 and the incident wave absorption plane 12. Note that the plane 12 can adopt another polygonal or elliptical shape, or even a specific form adapted (Jerusalem cross, spirals, fractal patterns ...). The term "plan" is a generic designation in that the plan includes a thickness.

The spacer 1 1 is for example of the honeycomb type.

In a known manner, the absorption plane 12 may be a high resistive impedance surface (SHI-R). A high impedance surface is a resonant surface that has the property of reflecting the electric field without phase shift. It typically includes repetitive metal patterns. Different shapes of metal patterns can be used, such as spiral, cross, or other.

By introducing resistive materials on this surface, the losses generated are consistent. The energy dissipated in the resistive layer is not reflected and the SHI behaves like an absorbent.

A typical solution is to introduce dielectric losses (via a ferrite, graphite, or other substrate), and / or losses. ohmic in the SHI, for example via resistors 30, as illustrated in FIG. 3.

The resistors 30 are arranged along the longitudinal axis X and the transverse axis Y of the absorption plane 12 of each cell 2.

The resistances of the different cells 2 are electrically connected to each other.

A set Ei then comprises a periodic repetition of the same cells 2 connected to each other. However, the cells 2 are different from one set Ei to the other, in order to ensure the performance required for the parameters of the incident waves on said set.

Different characteristics of the cells 2 are adjusted to enable them to provide the absorption function for the parameters which are specific to their own set Ei (angle of incidence, and / or polarization, frequency ranges, etc.).

In particular, the values of the resistances, the geometry and thickness of the absorption plane 12, the geometric dimensions of the cell (height, length, width, etc.) are adjusted in order to obtain the desired absorption performance for the parameters of the set Ei.

The dimensions and characteristics of the cell can be obtained by simulations, in particular by iterations and / or optimization.

Alternatively, the high impedance surface 40 may be supplemented by a resistive film 31.

The resistive film 31 may be located near the high impedance surface or at a distance above it.

In FIG. 4, an assembly comprising a plurality of cells 2 is illustrated, a resistive film 31 being placed under the metal patterned absorption plane 12 of the cells 2. The spacer 1 1 here consists of an air knife . The film 42 between the resistive film 31 and the plane 12 is for example a PET film.

Other technological solutions are known for making the cells. For example, the introduction of ohmic losses in IHS can be done via the introduction of localized resistive elements. One possible realization is the use of low conductivity tracks in SHI, such as copper or graphite, or by the introduction of low conductivity resistive inks.

According to the technological solutions, different characteristics of the cell 2 are adjusted to obtain the absorption performance required for the wave parameters associated with the set Ei comprising said cell 2.

Figure 1 illustrates the cells 2 in an arrangement on parallel lines.

Other arrangements are possible.

Sets (Ei) can be arranged according to any tiling (hexagonal, square ...). Sets Ei can be arranged in a polygonal plane.

In addition, sets (Ei) do not necessarily have the same shapes and sizes.

In one embodiment, the sets (Ei) are not arranged in the same plane, but constitute the faces of a volume construction, such as for example a multifaceted volume construction. The sets may for example be arranged on a pyramid shape.

In one embodiment, the sets Ei are arranged in concentric rings.

Each ring has different absorption properties, adapted to the parameters of the incident waves on said ring.

According to another possible aspect, possibly in combination with the arrangement in crowns, the plane 12 of absorption of the cells 2 is dimensioned so that a portion of the plane 12 in a first direction is sized to absorb the incident waves having a first polarization and a portion of the plane 12 in a second direction is sized to absorb the incident waves having a second polarization different from the first. For example, the first polarization is the TM polarization and the second polarization is the TE polarization. An exemplary application is illustrated in Figures 5 and 6. Figure 7 is a slight modification of Figure 5 with an off-center source.

In these examples, an antenna 21 is present above a face 22 of an object. The reflective plane 23, modifying the radiation pattern of the antenna 21, is on the face 22. The object is for example a carrier, a structure or a reflector.

The electromagnetic waves emitted or received by the antenna 21 tend to reflect on the face 22, and disturb the radiation pattern of the antenna 21.

The device 1 is therefore disposed on all or part of the face 22 in order to absorb the disturbing incident waves emitted or received.

As can be seen in FIG. 7, the incident waves have an angle of incidence θ, / θ ', which differs according to the zone of impact on the face 22.

The device 1 comprises a plurality of cells E1 to E4. Each set Ei has a minimum absorption coefficient that is valid for a range of angles of different incidence.

In addition, the sets Ei are arranged in concentric rings.

Assuming that the radiation of the antenna 21 is spherical, the radial dimension in the associated cylindrical coordinate system (in FIG. 5, symbolized by the letter R) of the cells 2 absorbs the polarization TM of the incident waves, and the orthoradial dimension (or concentric, symbolized by the letter C in Figure 5) absorbs the TE polarization.

The minimum absorption level is less than -15dB for all Ei cells.

Finally, the frequency range of the absorbed waves is identical for all the sets, and corresponds for example to the range 2-2.3 GHz.

As illustrated in Figure 7:

the set E1 is adapted for a range of angles of incidence between θι = 15 ° and ΘΊ = 40 °; the set E2 is adapted for a range of angles of incidence between θ ₂ = 40 ° and θ ₂ = 60 °;

the set E3 is adapted for a range of angles of incidence between θ ₃ = 60 ° and θ ₃ = 64 °;

the assembly E4 is adapted for a range of angles of incidence between θ ₄ = 64 ° and θ ₄ = 66 °.

In Figure 8, an embodiment is illustrated wherein a source 36 emits electromagnetic waves to Ei sets of cells. The sets Ei of cells are adapted to absorb the waves for angles of incidence [θ, -θ ',] ranges, and azimuth angle ranges [cpi-cpi'], different from a cell. to the other. The corresponding spherical landmark 37 is also illustrated.

As illustrated in Figure 8:

the set E0 is adapted for a range of angles of incidence between Θ1 and Θ2 (for example between 0 ° and 15 °), and for a range of azimuth angles φ of between 0 ° and 360 ° ;

the assembly E1 is suitable for a range of angles of incidence between Θ2 and Θ3 (for example between 15 ° and 40 °), and for a range of azimuth angles φ of between 45 ° and 90 ° ;

the assembly E2 is adapted for a range of angles of incidence between Θ2 and Θ3, and for a range of azimuth angles φ of between 0 ° and 45 °;

the assembly E3 is suitable for a range of angles of incidence between Θ2 and Θ3, and for a range of azimuth angles φ of between 315 ° and 360 °;

the assembly E4 is suitable for a range of angles of incidence between Θ2 and Θ3, and for a range of azimuth angles φ of between 270 ° and 315 °;

the assembly E5 is adapted for a range of angles of incidence between Θ2 and Θ3, and for a range of azimuth angles φ of between 225 ° and 270 °; the assembly E6 is suitable for a range of angles of incidence between Θ2 and Θ3, and for a range of azimuth angles φ of between 180 ° and 225 °;

the assembly E7 is adapted for a range of angles of incidence between Θ2 and Θ3, and for a range of azimuth angles φ of between 135 ° and 180 °;

the assembly E8 is suitable for a range of angles of incidence between Θ2 and Θ3, and for a range of azimuth angles φ of between 90 ° and 135 °.

The assemblies E9 to E16 are suitable for a range of angles of incidence between Θ3 and Θ4 (for example between 40 ° and 60 °), and for a range of azimuth angles respectively equal to the range of angles. of azimuth of sets E1 to E8. Process

A method for designing and producing an absorption device 1 is described.

This method can notably be integrated in a more general context of design and sizing of electromagnetic sources, such as an antenna, for a given mission, illustrated in FIG. 9.

For a given requirement or a given mission, the antenna as well as the carrier or the structure of the antenna are selected (steps S1 / S2).

The antenna is then arranged on the carrier or the structure according to the layout constraints (step S3).

The radiation performance of the electromagnetic waves is analyzed (step S4).

If these performances are insufficient compared to the specifications, the disturbing zones (reflections, multipaths) are identified and analyzed, by simulation or experiment (step S5).

The absorption device 1 is made to absorb these disturbing waves (step S6), and is arranged (step S7) on the structure or the zone which undergoes the disturbances. If the performances are judged satisfactory, the process is finished (step S8).

In Figure 10, an embodiment of a method for designing and producing an absorption device 1 is detailed.

An area 16 of an environment receives disturbing electromagnetic waves.

According to a step M1, parameters of the incident waves on the zone 16 are identified. This identification is conducted by simulation, calculation or measurement.

These parameters include, as already mentioned, one or more of the following parameters:

at least one angular range ([θ, -θ ',], [φί-φί']) of direction of arrival of the incident waves,

a polarization of the incident waves.

In one embodiment, a pair of arrival direction angular ranges ([θί-θ'ί], [φ, -φί ']) of the incident waves on the set (Ei) is taken into account.

Where appropriate, the parameters of the incident waves further comprise a range (f ,, f) of frequencies of the incident waves.

In a step M2, the zone 16 is divided into a plurality of elementary zones.

For each elementary zone, a set E comprising at least one electromagnetic wave absorption cell 2 is produced

(Step M3), said set Ei having a minimum absorption coefficient valid for one or more of the parameters of the incident waves on said elementary zone.

The parameters in question can be those actually identified for each zone, or a different range of values taking into account the parameters identified (for example a wider range of values including the parameters actually measured or obtained by simulation). The minimum absorption coefficients may be different from one set to another, or the same.

The sets Ei are made using one of the previously described technologies (SHI with resistors, SHI with resistive film, etc.), or according to other known technologies. The technologies used may vary from one set to another.

Once the zone 16 is discretized, and the sets Ei obtained for each elementary zone, said assemblies Ei are assembled (step M4) so as to obtain an absorption device 1 for the whole of the zone 16. The assembly depends on the technology used for the cells 2. It may be an electrical and / or mechanical assembly as appropriate.

The device 1 can then be arranged on the zone 16.

The method may also comprise (see FIG. 1 1) the intermediate step M2i of defining, for each elementary zone:

- parameters of the incident waves (polarization, angles of incidence, frequency) taking into account the parameters measured, and

- the expected absorption coefficients.

The method further comprises the step of evaluating (step M2 ₂ ), for example by simulation or measurement, the radiation performance of the electromagnetic waves of a source emitting and / or receiving electromagnetic waves in the environment (by example of the waves returning to the source), when the device 1 as defined is disposed in the zone 16.

These performances are compared to specifications.

If the emission performance of the electromagnetic waves conform to the specifications, the sets Ei are made (step M3).

Otherwise (step M2 ₃ ), the zone 16 is redécoupée according to different elementary zones and sets Ei are made for these zones. For example, a finer division is used.

In addition, it is possible to redefine the expected parameters for the zones. The method of designing and producing the device 1 can be implemented in the following method:

for an environment comprising at least one source emitting and / or receiving electromagnetic waves, identifying zones 16 of disturbance, or subjected to disturbances, due to the electromagnetic waves originating or reaching the source 15,

performing one or more absorption devices 1 for said zones 16, according to the method as described, and

placing said absorption devices 1 at said zones 16.

Application examples

The device and method have many applications, some of which are illustrated in Figures 12-14.

In Figure 12, an antenna 35 is placed on a building. Zones 33 disturb the radiation of the antenna 35. In addition, areas 41 of a school or hospital are to be protected. An absorption device is thus placed on each of the zones 33, 41 in order to absorb the incident waves, taking into account the angle of incidence, the polarization, and, if appropriate, the frequency of the incident waves. .

In Figure 13, an antenna 43 is placed on a wing of an aircraft.

The absorption device is disposed on the fuselage and / or the empennage of the aircraft. Different angles of incidence θ, θ 'are illustrated, and are taken into account by the sets Ei of the device 1.

In Figure 14, the antenna 43 is this time placed on the fuselage of the aircraft. An absorption device 1 is disposed under the antenna, at its ground plane, and another absorption device is disposed on the wing of the aircraft. Different angles of incidence θ, θ 'are illustrated, and are taken into account by the device 1.

Another example is illustrated in FIG. 15. An antenna 44 is disposed between two walls 47 of a cavity. The walls 47 are covered internally and / or externally with the device 1. Advantageously, one walls or all of the walls is retractable (arrow 48), in order to release the antenna 44.

Other applications include:

- the reduction of the interaction between an antenna and its structure; - reduction of multipath in a given environment;

- the reduction of the electromagnetic signature, with the aim of improving stealth.

The invention has many applications in many technical fields requiring the absorption of disturbing electromagnetic waves.

Claims

1. An electromagnetic wave absorption device (1), comprising a plurality of sets (E,) each comprising at least one electromagnetic wave absorption cell (2), characterized in that:

each set (Ei) has a minimum absorption coefficient valid for given parameters of the incident waves on said set (Ei),

said parameters comprising one or more of the following parameters: a pair of arrival direction angular ranges ([θί-θ'ί], [φ, -φί ']) of the incident waves on the set (Ei), comprising a range of angles of incidence ([θ, -θ ',]) and a range of angles of azimuth ([cpi-cpi']), and

a polarization of the incident waves,

the parameters of the incident waves for which each set (E,) ensures the minimum absorption coefficient being different from one set (Ei) to the other.

2. Device (1) according to claim 1, wherein said parameters further comprise a range (f ,, f) of frequencies of the incident waves.

3. Device (1) according to one of claims 1 or 2, wherein the sets (Ei) are arranged in concentric rings.

4. Device (1) according to one of claims 1 or 2, wherein the sets (Ei) are arranged in a plane of polygonal shape, or on faces of a three-dimensional shape.

5. Device (1) according to claim 3, comprising cells (2) whose absorption plane (12) is dimensioned so that: a portion of the plane (12) in a first direction is sized to absorb the incident waves having a first polarization,

- A portion of the plane (12) in a second direction is sized to absorb the incident waves having a second polarization different from the first.

6. Set comprising:

a source (15) emitting and / or receiving electromagnetic waves, and

- a device (1) according to one of claims 1 to 5, being configured to absorb electromagnetic waves from the source and / or going to the source (15), each set (Ei) of cells (2) having a minimum absorption coefficient valid for one or more of said incident wave parameters transmitted by the source (15) to said set (Ei).

7. A method for designing and producing an absorption device (1) for a zone (16) of an environment to which electromagnetic waves are directed, characterized in that it comprises the steps of:

identifying (M1) parameters of the incident waves on the zone (16), said parameters comprising one or more of the following parameters:

a pair of angular ranges ([θ, -θ ',], [φί-φί']) of arrival direction of the incident waves, comprising a range of angles of incidence ([θ, -θ ',] ) and a range of azimuth angles

a polarization of the incident waves,

cutting (M2) the zone (16) into a plurality of elementary zones; for each elementary zone, producing (M3) a set (E) comprising at least one electromagnetic wave absorption cell (2), said set (Ei) having a minimum absorption coefficient valid for one or more of the parameters incident waves on said elementary zone.

The method of claim 7, wherein the parameters of the incident waves further comprise a range (f ,, f) of frequencies of the incident waves.

9. Method according to one of claims 7 or 8, comprising the step of assembling the sets (Ei) of absorption cells, so as to obtain an absorption device (1) for the zone (16).

The method according to one of claims 7 to 9, comprising the steps of:

- evaluating (M2 ₂ ) the radiation performance of the electromagnetic waves of an electromagnetic source (15), receiving and / or emitting electromagnetic waves when the device (1) is disposed in the zone (16), and comparing the performances with specifications,

- In case of non-compliance (M2 ₃ ), cut the area (16) in finer elementary areas, and make sets (Ei) for these finer elemental areas.

1 1. Process comprising:

for an environment comprising at least one source (15) emitting and / or receiving electromagnetic waves, identifying zones (16) of disturbance, or subjected to disturbances, due to the electromagnetic waves emitted and / or received by the source ( 15) performing one or more absorption devices (1) for said zones (16), according to one of claims 7 to 10, and placing said absorption devices (1) at said zones (16).