Transmitting / receiving device with an extended steering domain

Abstract

The invention relates to a device for transmitting / receiving an electromagnetic wave, the device comprising: - a reconfigurable planar antenna (Ant) configured to transmit at least one electromagnetic beam (EB) at a plurality of angles, wherein the electromagnetic beam has a central wavelength; - a dome (DO) having a surface S, wherein the surface has, in at least one peripheral portion, a structuring in at least one type of pattern, wherein the patterns have at least one dimension smaller than the central wavelength, wherein the patterns are also non-resonant, and wherein the surface and the structuring are configured to apply a given phase law to a beam emitted by the antenna at a first angle (θA), such that the beam is deflected by a second angle (θB) dependent on the first angle and greater than the first angle.

Description

DESCRIPTION TITLE: Extended depointing range transmitting / receiving device FIELD OF THE INVENTION

[0001] The present invention relates to the field of antenna equipment with reconfigurable beam, i.e. equipment whose transmission / reception direction can be controlled, for mobile communications applications, between platforms (between aircraft for example) or towards a constellation of satellites. It relates more particularly to the field of planar antennas. STATE OF THE ART

[0002] Mobile communications applications require a focus on compactness, energy efficiency, and angular agility of antennas. The traditional approach based on moving parabolic or similar antennas on a cradle often does not meet compactness constraints due to the height required and involves the use of complex mechanics. Thus, planar antennas are currently deployed on avionics or terrestrial platforms.

[0003] Reconfigurable planar antennas transmit / receive one or more electromagnetic beams in one or more directions simultaneously, the direction(s) being chosen, i.e. controlled. Planar antennas comprise radiating elements distributed on a plane and are of two types. Mechanically scanned planar antennas rely on movement of the radiating elements in the plane of the antenna. Electronically scanned antennas have devices adapted to control the phase (and where appropriate the amplitude) of the wave radiated by each element, making it possible to control the angle of emission / reception of the wave.

[0004] Antenna directivity is defined as the ratio of the power density radiated in the direction of the main lobe to the power density that would be radiated by an isotropic antenna radiating the same total power.

[0005] Antenna gain is defined as the antenna's directivity multiplied by an efficiency factor. This factor reflects the impact of losses within of the antenna, and is calculated as the ratio of the radiated power to the power injected into the antenna feed port.

[0006] Gain and directivity are expressed in dBi (in reference to the isotropic antenna).

[0007] The dome bandwidth is defined as the frequency interval relative to a central frequency (in %) in which the following two conditions are satisfied:

[0008] the maximum misalignment angle of the antenna + dome device is greater than the misalignment angle of the antenna alone.

[0009] The gain of the antenna + dome device is not more than 3 dB lower than that of the antenna alone over the misalignment range from zenith to maximum angle, i.e. no more than 3 dB is lost with the addition of the dome.

[0010] Planar steerable beam antennas play a major role in multiple applications such as satellite communications, mobile terminals, radars, base stations for telecommunications, etc.

[0011] Their planar shape necessarily implies a gain loss greater than 3 dB when the misalignment angle, i.e. the angle of the beam emitted / received by the antenna, exceeds 60°. The gain degradation of a planar antenna when the misalignment angle increases is caused by two main factors:

[0012] Lower directivity resulting from a reduced effective radiating aperture. Typically the directivity follows a cos(0) power law inducing gain losses, relative to the maximum gain obtained at the zenith, at least 3.7 dB, 4.7 dB and 7.6 dB for misalignments of 65°, 70° and 80°, respectively.

[0013] A strong active impedance mismatch on the radiating elements, causing a degradation of the radiation pattern and the appearance of blind zones.

[0014] This problematic situation is particularly common for avionics applications, given the orbits used by communications satellites and the trajectories of aircraft around the globe. For reasons of aerodynamic constraints, costs and discretion, antennas on carrier are ideally thin and directly integrated into the fuselage, which limits the effective surface area of ​​the antenna at high misalignment angles. This results in a lower signal level which leads either to a reduction in the information rate or to a breakdown of the link. Maintaining this generally requires increasing the power emitted by the satellite or multiplying the number of antennas on the carrier.

[0015] There is therefore a need to extend the misalignment range (accessible angular transmission / reception range) and / or to compensate for part of the loss of gain at high misalignment angles (>60°) of planar antenna systems with steerable beam. It is necessary to achieve this function without excessively degrading performance at the zenith.

[0016] The addition of a planar deflector (of dimensions equivalent to those of the antenna), placed parallel to the antenna and above it, would increase the maximum depointing angle, but would not solve the problem of reducing the effective surface area, and therefore directivity. To do this, it is necessary to integrate this function on a non-planar shape. This involves adding a deflection function, preferably on the internal face of the radome (acting as mechanical protection) or on an additional component positioned between the antenna and the radome.

[0017] Some solutions have already been proposed, but given their properties they have not yet been implemented in current devices. We can cite four existing solutions which are based on the shaping of dielectric materials.

[0018] A first solution illustrated in Figure 1 consists of producing a dome 20 with a thickness gradient, as described in document WO2019067474. Two impedance matching layers 21 are deposited on the two faces of the dome. The dome 20 is arranged above the planar antenna AntO of width L. Although broadband and simple to produce, this solution has the disadvantage of being very bulky and heavy. For example, its implementation described in the document by Gandini et al “A Dielectric Dome Antenna With Reduced Profile and Wide Scanning Capability” IEEE Transactions on antennas and propagation, vol. 69, no. 2, pp. 747-759, Feb. 2021, leads to a width of dome ~ 3.5 x L, where L is the width of the planar antenna considered. This large dimension limits its use for the intended application. This is due to the need to have a large difference between the internal and external radii of curvature of the dome, as well as the use of dielectric materials with low permittivities (~2) facilitating impedance matching between the air and the dome, which imposes a large thickness on the ends (> 2 o ; o being the wavelength at the center frequency).

[0019] A second solution is to implement Bragg gratings. The rectification of large misalignment angles is then carried out very efficiently over the entire frequency band with a constant thickness of a few o, or relatively large. Dielectric materials with low permittivities (~2) are also used to ensure good impedance matching between the air and the dome. On the other hand, the transition to the Bragg regime at intermediate incidences between the zenith and the horizon (misalignment around 40°) leads to the coexistence of two beams (two orders of diffraction). This particularity of discontinuous deflection makes this solution more complex to implement.

[0020] A third solution is illustrated on and described in the publication by Young et al "Dielectric Huygens Metasurface Dome Antennas" IEEE Antennas and Wireless propagation letters, vol 21, n°11 (2022). Elie is based on the implementation of a Huygens metasurface 23, based on dielectric resonators 22. Indeed, for certain sets of dimensions these resonators have a superposition of electric and magnetic dipole resonances. This superposition makes it possible to obtain a unitary transmission in the direction of propagation of the wave. Thus, the patterns can play the role of secondary sources specific to the Huygens-Fresnel theorem. Each of these sets of dimensions also offers different phase values ​​in transmission. It is therefore possible to produce a phase profile in transmission (4) by dimensioning the resonators (shape, volume, material) in such a way that at the resonance frequency of the patterns the electromagnetic beam EB0 is perfectly deflected without reflection.

[0021] The structure described in this publication consists of cylinders made of a high permittivity material (9.7) embedded inside a plate of lower permittivity (2.5). Obtaining a transmission of 1 (zero reflection) leads, with this formalism seeking resonant operation at a given frequency (30 GHz), to the determination of a set of pairs (height / diameter) of the cylinders verifying this condition, a pair inducing a given phase, the accessible phase being between -45° and 135° approximately. The calculated cylinders typically have a diameter and a height of the same order of magnitude, with a height not exceeding 3 mm for a resonance frequency of 30 GHz.

[0022] The phase law ensuring the dome deflection function is thus obtained with a constant thin thickness and adapted dimensions (2a < 2L). The limitation of this approach lies in the resonant behavior of the patterns, which induces a phase law that is only obtained for an incident wave with a frequency very close to the resonant center frequency fO. The frequency bandwidth of such a dome is therefore too small; the work carried out shows that the beam deflection is maintained at approximately 1% of the center frequency fO for the intended application. In addition, the manufacturing of this type of component has not yet been demonstrated and remains complex.

[0023] A fourth approach is to produce a hemispherical full lens with an index gradient, as presented in document US4333082. This solution is based on the progressive refraction of the electromagnetic wave emitted by the antenna through different dielectric layers. This approach makes it possible to obtain very large angular coverage that can even go beyond 90° of misalignment. However, this approach requires a significant increase in the weight of the device.

[0024] An aim of the present invention is to remedy the aforementioned drawbacks by proposing a transmission / reception device comprising a planar antenna and a dome providing a deflection function, the dome being thin and therefore light, and having a wide operating frequency band. DESCRIPTION OF THE INVENTION

[0025] The present invention relates to a device for transmitting / receiving an electromagnetic wave comprising: - a reconfigurable planar antenna configured to emit at least one electromagnetic beam at a plurality of angles, the electromagnetic beam having a central wavelength, - a surface dome S, said surface having, on at least one peripheral part, a structuring according to at least one type of pattern, said patterns having at least one dimension less than said central wavelength, said patterns also being non-resonant, - said surface and said structuring being configured to apply a determined phase law to a beam emitted by the antenna at a first angle, so that said beam is deflected at a second angle depending on said first angle and greater than said first angle.

[0026] According to one embodiment, the structuring is chosen from pillars or grooves, the pillars or grooves being made from at least a first dielectric material arranged on an inner and / or outer face of a first substrate.

[0027] According to another embodiment, the structuring is formed of holes or porosities in a second substrate made of a second dielectric material.

[0028] Preferably the porosity is chosen from a honeycomb, a gyroid or a grid.

[0029] According to one embodiment, the device according to the invention further comprises at least one additional layer in contact with the first or second substrate.

[0030] According to one embodiment, a relative permittivity of a dielectric material carrying out the structuring is greater than or equal to 6.

[0031] According to one embodiment, the structuring is a combination of at least two types of patterns.

[0032] According to one embodiment, a shape of the patterns is further adapted so as to achieve impedance matching with the air.

[0033] According to one embodiment, a phase excursion of said phase law is strictly greater than 2, a permittivity of a dielectric material producing said structuring being chosen so as to produce said maximum phase without folding.

[0034] According to one embodiment, the electromagnetic beam has at least two different polarizations and the structuring is further adapted to take said polarizations into account.

[0035] According to one embodiment, the antenna comprises radiating elements having an electronically controlled phase, the phases being further adapted to said phase law so as to optimize a gain of the antenna.

[0036] According to one embodiment, the dimension of said patterns is less than or equal to a maximum operating wavelength divided by three.

[0037] The following description presents several exemplary embodiments of the device of the invention: these examples are not limiting of the scope of the invention. These exemplary embodiments present both the essential characteristics of the invention as well as additional characteristics linked to the embodiments considered.

[0038] The invention will be better understood and other characteristics, aims and advantages thereof will appear during the detailed description which follows and with reference to the appended drawings given as non-limiting examples and in which:

[0039] Figure 1 already cited illustrates a dome for a planar antenna with varying thickness according to the state of the art.

[0040] Figure 2 already cited illustrates a dome for a planar antenna based on a Huygens surface having dielectric resonators according to the state of the art.

[0041] Figure 3 illustrates the device for transmitting / receiving an electromagnetic wave according to the invention.

[0042] Figure 4 illustrates a pillar structure.

[0043] Figure 5 illustrates a groove structure.

[0044] Figure 6 illustrates a hole pattern in a substrate.

[0045] Figure 7 illustrates a porosity structure in a substrate.

[0046] Figure 7bis illustrates a structuring with encapsulation of the structured substrate between a solid lower layer and upper layer.

[0047] Figure 8 illustrates a surface shape of the elliptical dome.

[0048] Figure 9 illustrates a non-canonical dome surface shape.

[0049] Figure 10 illustrates a three-dimensional view of a spherical dome according to the invention, the central part of which (top of the dome) is devoid of patterns.

[0050] Figure 11 illustrates a simplified geometric approach to calculating the maximum directivity improvement expected from increasing the effective antenna area

[0051] Figure 12 depicts the relationship between the phase introduced at 29 GHz frequency and the pattern size for pillar and hole type cells.

[0052] Figure 13 illustrates an example of a phase law at the frequency of 29 GHz realized with pillars.

[0053] Figure 14 shows an example of normalized directivity of a dipole antenna array as a function of the misalignment angle at different frequency points, with and without the proposed dome. DETAILED DESCRIPTION OF THE INVENTION

[0054] The device for transmitting / receiving an electromagnetic wave 10 according to the invention is illustrated in Figure 3. It comprises a planar antenna Ant conventionally produced on a substrate Sub. The antenna Ant is reconfigurable, configured to transmit at least one electromagnetic beam EB at a plurality of angles. The antenna Ant can thus transmit one beam (single-beam antenna) or several beams simultaneously (multi-beam antenna). At a time t one or more emission (or reception) angles are chosen, the value of these angles being controllable. In the following, a beam EB is considered, but the invention also relates to a multi-beam transmission / reception device. The electromagnetic beam EB has a wavelength λ and a frequency f. The beam EB has frequencies f located in a operating frequency range between a minimum frequency and a maximum frequency. Typically the range is in the interval [ 0.9 fO ; 1.1 fO ] for a central frequency fO which can be of the order of GHz to a few tens of GHz, certain applications may however require wider frequency bands.

[0055] The planar antenna can be mechanically or electronically scanned.

[0056] The device 10 also comprises a dome DO equipped with a continuous deflection function. It comprises a surface S, the surface having, on at least one peripheral portion, a structuring according to at least one type of pattern. The structuring may be located on the internal face (antenna side) or the external face of the surface of the dome. The patterns are said to be sub-wavelength, that is to say they have at least one dimension smaller than the minimum operating wavelength of the device. The structuring is made of a dielectric material.

[0057] The surface S and the pattern structuring are configured to apply a determined phase law to a beam emitted by the antenna at a first angle 0A, so that the beam is deflected at a second angle 0 Bfunction of the first angle and greater than said first angle. This condition illustrates the deflection function of the whole (surface, patterns). The deflection condition is expressed here for transmission but by reciprocity the proposed solution also works in reception.

[0058] Thus the phase profile is obtained by structuring at the sub-wavelength scale of a dielectric material that does not introduce resonance in the operating band. The structuring of sub-wavelength patterns introduces a phase law that can be interpreted as resulting from the realization of an effective permittivity (or an effective index). A dome is thus produced in an artificial material with an effective permittivity gradient.

[0059] According to one embodiment, the dome coupled to the planar antenna according to the invention is surmounted by a protective radome. According to another embodiment, the dome is integrated into the protective radome.

[0060] Furthermore, according to one embodiment, the structuring is carried out in such a way as to facilitate impedance matching. The geometry of the pattern defines the transmitted phase but also affects the impedance matching.

[0061] The concept of artificial material and effective permittivity is for example described in the paper by Feng et al "Three-dimensional broadband and broad-angle transformation optics lens" Nature Communications November 2010. In particular, it is possible to obtain an artificial material and adjust its effective permittivity by playing on its structuring at a sub-wavelength scale.

[0062] According to this principle, the dimensions of the patterns to be positioned at each point of the dome are identified in order to implement the desired phase law as faithfully as possible. In particular, the phase law is carried out with the phase of the complex transmission coefficient of the patterns, each considered in an infinitely periodic plane environment. This transmission coefficient can be estimated analytically for simple cases or using numerical calculation tools for more complex cases. The structuring is done in such a way as to obtain in the band of interest patterns that are not very reflective with respect to the electromagnetic wave. When carrying out the phase law via the complex transmission coefficient, care is taken to favor progressive variations of geometries along the dome to verify as much as possible the hypothesis of local periodicity under which the transmission coefficients were extracted.Furthermore, it is also possible to take into consideration the angle of incidence of the electromagnetic wave on the dome for each pattern, and therefore to consider the adequate transmission coefficients.

[0063] The device according to the invention makes it possible to provide a significant improvement in gain (> 1 dB) for large misalignment angles, typically greater than 60° and / or to extend the misalignment range (see for example the numerical calculation below).

[0064] It also allows for a reasonable footprint. According to one embodiment, accessible with the dome according to the invention, the width D of the dome is less than or equal to 2 times the width L of the antenna. According to one embodiment realization the dome has a thickness between A and 3Â, where  is the wavelength at the maximum operating frequency.

[0065] The non-resonant nature of the structuring patterns allows the device according to the invention, unlike the device integrating a Huygens surface described above, to be broadband, that is to say to operate for a frequency band with a width greater than 20% of the central frequency fO.

[0066] According to a first embodiment also illustrated in figure 3 the patterns of the structuring are pillars P in a first dielectric material Mat1 deposited on a first substrate Subi. The substrate can be of the same material Mat1 as the pillars, or in another material MatS with a lower permittivity. An example of structuring in pillars is also illustrated in figure 4. According to one embodiment the pillars have a pointed shape which makes it possible to limit the reflection phenomena, even when the dielectric material has a high permittivity (typically around 7 to 10).

[0067] According to a second embodiment illustrated in Figure 5, the patterns of the structuring are grooves Gr in material Mat1 deposited on a first substrate Subi. The substrate can be of the same material Mat1 as the grooves, or in another material MatS with a lower permittivity. The grooves can have the advantage of easier manufacturing by mechanical machining.

[0068] The pillars or grooves are arranged on an inner and / or outer face of the first substrate Subi.

[0069] According to a third embodiment illustrated in FIG. the structuring is formed by holes H in a second substrate Sub2, the substrate Sub2 being made of a second dielectric material Mat2. The holes can be made by drilling a solid material and offer good mechanical strength.

[0070] According to a fourth embodiment illustrated in Figure 7, the structuring is formed by a porosity Por of a substrate Sub2. The porosity is, for example, a honeycomb, a gyroid or a grid. The porosity is easily achievable by additive manufacturing.

[0071] According to one embodiment, the device according to the invention further comprises at least one additional layer in contact with the first or second substrate, and possibly other additional stacked layers. The additional layer(s) may be solid or structured. These layers are, for example, index matching or external protection layers. According to one embodiment, an additional layer has a structuring according to a second type in patterns. The phase law is then determined by taking into account the two pattern layers. Figure 7bis illustrates the case of encapsulation of the structured substrate Sub2 between a solid Ladd / inf layer and a solid Ladd / sup layer.

[0072] These different patterns have the advantage of being achievable with additive manufacturing methods, and for some in a single dielectric material (holes, porosity, Subi substrate of the same material as the pillars or grooves).

[0073] The dome according to the invention can also be produced by machining or injection.

[0074] According to one embodiment, the structuring is a combination of at least two types of patterns, as illustrated in Figure 7, these patterns being able to be in the same material or in two different materials.

[0075] The phase law to be implemented, and therefore the structuring, depends on the shape of the dome. According to one embodiment, the surface S is hyperbolic in shape, as illustrated in Figure 3. According to another embodiment illustrated the surface S is elliptical in shape.

[0076] According to another embodiment illustrated in FIG. the surface is freely defined by a set of points, it is then called "non-canonical". This free form makes it possible to relax design constraints by having a large number of degrees of freedom in design and optimization.

[0077] Figure 10 illustrates a three-dimensional view of a spherical dome according to the invention made with pillars, without patterns on its central part (top of the dome).

[0078] According to one embodiment, the dome according to the invention has a symmetry of revolution. According to another embodiment, it has a structure of cylindrical symmetry (single-plane scanning).

[0079] The distribution of the patterns on the conformal surface is adjusted locally to obtain the desired behavior (phase law) and optimize performance. The absence of a pillar on the top of the dome limits the divergent effect when the antenna is pointing at the zenith and thus limits the loss of gain. Thus, the patterns are not necessarily present in the central (top) area of ​​the dome, as illustrated in Figures 3 and 8 to 10.

[0080] The height h of the dome, relative to the width L of the antenna, as well as its shape (shape of the surface S), determine the maximum increase in directivity that can be achieved for a given misalignment angle 0 B when the dome is designed for an antenna exit angle of 0 A relative to the vertical. Figure 11 illustrates geometrically the increase in directivity.

[0081] For the example in Figure 11, we consider a structure that is invariant in the dimension normal to the depointing plane. We therefore reason in terms of projected lengths. This structure consists of a planar antenna of lateral dimension L, comprising a plurality of radiating elements RE, and a pyramidal dome DO positioned above.

[0082] The design point is defined as the pair (planar antenna output angle, dome output angle) for which the phase law is initially determined.

[0083] Trigonometric analysis shows that the maximum improvement of M at the design point is expressed as follows

[0085] Or :

[0086] 0 A angle at the output of the planar antenna and 0 B dome exit angle

[0087] a is the inclination of the dome relative to the planar antenna:

[0089] h being the distance between the top of the dome and the antenna,

[0090] D dome width.

[0091] This improvement is graphically visible by the ratio of the two lengths illustrated in Figure 11. L” corresponds to the projected length of the antenna+dome assembly for the beam deflected in the 0 direction B , and L.COSOB at this same magnitude for the antenna alone assuming that it orients its beam in this same direction 0 B .

[0092] Here, the assumption is made that the height h is sufficient for only one face of the dome to be illuminated, i.e.:

[0094] So, for a dome designed to deflect a beam oriented at 0 A = 55° at the antenna output towards an angle of 0 B = 80° with a dome of width D = 1.3*L (L being the antenna width) and height h = 0.35*D, a directivity improvement of 3.7 dB is expected at 80°, from which the deflection efficiency must be subtracted, strongly depending on the choice of implementation (typically 1 to 2 dB).

[0095] The deviation of the beam emitted by the antenna in the direction given by 0 Bat the output of the dome is obtained by implementing a phase gradient on the dome. This deviation follows in the ideal case the generalized Snell law, explained for example in the document by Steyskal et al "On the gain-versus-scan tradeoffs and the phase gradient synthesis for a cylindrical dome antenna" IEEE Trans. Antennas Propag., Vol AP-27, n°6 (1979). This stipulates that a beam incident on the dome with an angle relative to its normal 0 A ' is deflected in the exit direction given by the angle 0 B thanks to a phase gradient in transmission <p(x) où x paramètre la direction tangentielle au dôme :

[0097] k0 being the free space wave number at the design frequency.

[0098] We have 0 B = 0 B — a and 0 A = 0 A - has

[0099] The idea behind the invention is to structure a dielectric material at a sub-wavelength scale in order to obtain the desired phase variation at the frequency of interest.

[0100] To calculate the phase law to be implemented, an initial phase law adapted to a chosen design point is first calculated. Then, local modifications can be added to adjust the behavior at other angles of incidence. For a given case, an optimization procedure aimed at obtaining certain far-field radiation characteristics is generally necessary. For example, it may involve increasing the maximum radiation angle of the antenna, while minimizing the impact on the zenith performance. One may also seek to obtain a constant gain regardless of the viewing angle. Objectives in terms of polarization quality and spurious lobe levels can also be integrated. Generally, this optimization has as adjustment parameters both the phase distribution and the dome shape (surface S), subject to compliance with the space constraints of the application.

[0101] The occurrence of unwanted diffraction phenomena is avoided when the structuring allows for a large excursion of achievable phases, which makes it possible to avoid folding at more or less periodic intervals. Indeed, these foldings introduce discontinuities which disturb and degrade the operation of the device. For example, for pillar-type patterns, a phase folding corresponds to a sudden change in diameter between two adjacent patterns, typically from the widest pillar to the thinnest pillar.

[0102] Let cpmax be the phase excursion, i.e. the difference between the maximum phase and minimum phase of the phase law. Typically we have cp m ax > 2K, and we seek to achieve the phase law without aliasing. A phase law without aliasing means a phase varying continuously and monotonically between a minimum value and a maximum value.

[0103] This is all the easier when the thickness of the dome or the permittivity of the material used are large. For reasons of space, we do not want to have a dome that is too thick. Thus, preferably, the relative permittivity of the dielectric material producing (forming) the structuring, for example the relative permittivity of the first dielectric material Mat1 or the second material Mat2, is greater than or equal to 6.

[0104] For example, in the case where the structuring consists of juxtaposing elementary cells characterized by an adjustable filling of dielectric material, we define the effective permittivity associated with each of these cells £ r-e ff, which takes a maximum value £^1“^ for the strongest filling. Thus, for a given dome thickness t, the phase excursion cp m ax achievable is given by the formula:

[0106] Thus, for a total height of the cell limited too (including the adaptation part), a phase excursion of 360° is obtained from a relative permittivity of the order of 6, when the cell filling rate is 100%. To obtain a phase excursion of 720°, a relative permittivity close to 14 is necessary.

[0107] The use of materials with high permittivities may, however, require the addition of impedance matching layers on either side of the dome to limit reflections, typically quarter-wave plate-type dielectric layers. These layers can be solid or structured (effective permittivity) types.

[0108] According to one embodiment, the shape of the patterns is adapted so as to achieve impedance matching with the air. This is, for example, a pointed shape for the pillars, as illustrated in Figures 3 and 4, or a conical shape for the holes. This avoids an additional layer of impedance matching.

[0109] The cell dimensions and manufacturing constraints define the maximum dimensions of the pattern integrated into the cell.

[0110] According to one embodiment, the excursion in phase cp m ax of the phase law is strictly greater than 2K, and the permittivity of the dielectric material carrying out the structuring is chosen so as to achieve this maximum phase without folding.

[0111] Several types of structuring allowing the adjustment of the dielectric material rate can be implemented, as described previously: pillars, holes, porosities, etc.

[0112] For example, it is possible to vary the size of a pattern. Figure 12 shows the relationship between the phase introduced at the frequency of 29 GHz and the size of the pattern for "pillar" and "hole" type cells. To facilitate representation, the size of the pattern is in both cases an increasing function of the quantity of dielectric. For the pillar this size is its diameter. A variation in height, or a combination of the two, can also be considered. For the hole, this is the difference between the cell width and its diameter. The cells have a fixed total height of 14.5 mm and a period of 2.6 mm.

[0113] The 12 mm high pillar is made of Mat1 material with a permittivity of 7.5 and rests on a 3 mm thick MatS support material with a permittivity of 2.3. A pyramid is added on top of the pillar to match the impedance of the air to that of the pillar material. The hole is drilled in a material with a permittivity of 7.5.

[0114] Curves 121, 122 illustrate the pattern size, respectively the diameter for the pillars, and the difference between cell size and hole diameter for the holes, necessary to obtain a given phase value, referenced to the phase induced by the smaller pattern. It can be seen that a phase excursion of the order of 600° is achievable with these two types of patterns and a permittivity value of the first material of 7.5.

[0115] To achieve the phase law, it is thus possible to play on one or more shape parameters of the pattern (or porosity). It is also possible to play on the density / distribution of the patterns, possibly in combination with one or more shape parameters of the pattern. Examples include the height, diameter and shape of a pillar, the width, depth and shape of a groove, the shape and depth of a hole or porosity, etc.

[0116] Figure 13 illustrates an example of a phase law carried out with pillars as described previously, as a function of the curvilinear abscissa Xc on a dome such as than that of Figure 8. The origin of the abscissa is the top of the dome and the value of + / - 200 mm corresponds to the end of the dome in contact with the antenna plane. The area of ​​curve 11 for which the phase is zero corresponds to the upper part of the dome which does not include pillars. The phase varies between 0° and 580°, monotonically and in steps, these steps being due to the discrete structuring of the pillars.

[0117] According to one embodiment, the antenna is configured to operate for at least two different polarizations of the electromagnetic beam, typically two orthogonal linear polarizations or two right / left circular polarizations. To guarantee such operation, the behavior of the dome should be identical for two orthogonal linear polarizations (phase law and amplitude of the transmission coefficient).

[0118] In some cases it is possible that the dome does not meet this condition. In order to compensate for this effect according to one embodiment the parameters of the structuring (type(s) of pattern, pattern parameters, distribution, etc.) are also adapted to ensure identical treatment for all operating polarizations of the electromagnetic beam emitted by the antenna. In other words the structuring is configured to take into account the multiple polarizations of the electromagnetic beam emitted by the antenna.

[0119] The inventors have also established that the best results are obtained when the dimension of the patterns (and therefore of the cell) is less than  / 3, where  is the wavelength of the electromagnetic wave in free space at the maximum operating frequency.

[0120] Figure 14 shows as an example the normalized directivity Dirn of a parallel dipole antenna array as a function of the misalignment angle Dep at different frequency points 18, 24 and 28 GHz, with and without a dome.

[0121] The source antenna is a linear array of 60 dipoles separated by 0.47Â, Â being the wavelength corresponding to the highest operating frequency, here 28 GHz, giving a total width L of approximately 28Â. The amplitude of the dipoles is modulated according to a Hamming apodization. This antenna illuminates a dome with a single radius of curvature, in the H plane of the network, with footprint D = 1.13*L, or 31.4Â, and height h = 0.3L, or 8.3Â (internal height of the dome).

[0122] The pillars are the same as those described in the example in Figure 12.

[0123] Curves S18, S24, and S28 correspond to the case without a dome for frequencies 18, 24, and 28 GHz respectively.

[0124] Curves D18, D24 and D28 correspond to the case with dome respectively for frequencies 18, 24 and 28 GHz.

[0125] It can be seen that the presence of the dome allows the antenna misalignment range, limited to 77°, to be extended up to 86°. In addition, the antenna directivity is increased (compared to the case without a dome) from a misalignment angle of approximately 70°. The reduction in directivity at the zenith is around 1 dB, which is acceptable. Insertion losses for this type of pattern are estimated at around 0.5 dB.

[0126] With the maintenance of the increase in the maximum depointing angle for all frequency points from 18 to 28 GHz, the graph demonstrates the broadband behavior of the dome, here greater than 40%.

[0127] Thus in this example we see that the device according to the invention:

[0128] allows to extend the misalignment domain beyond 70° and / or increase the antenna gain at high misalignment angles.

[0129] is compact with a width < 2 x the antenna diameter and a thickness of around 1.6Â.

[0130] is broadband (>20% of relative frequency band),

[0131] can be produced on a compliant surface thanks to its “all dielectric” nature and the use of additive manufacturing techniques,

[0132] does not present angular selectivity and therefore preserves the continuity of the antenna misalignment,

[0133] features a locally adjustable phase profile at a subwavelength scale to limit gain degradation around the zenith.

[0134] According to one embodiment, the antenna is electronically scanned. It comprises radiating elements having an electrically controlled phase. It is possible to integrate the effect of the dome for each viewing angle into the phase control law of these radiating elements, and thus increase the gain of the antenna+dome assembly over the entire viewing angular range. For example, it is possible to partially compensate for the degradation observed at the zenith.

Claims

CLAIMS 1. Device for transmitting / receiving an electromagnetic wave comprising: -a reconfigurable planar antenna (Ant) configured to emit at least one electromagnetic beam (EB) at a plurality of angles, the electromagnetic beam having a central wavelength (ÀO), -a dome (DO) of surface S, said surface having, on at least one peripheral part, a structuring according to at least one type of pattern, said patterns having at least one dimension smaller than said central wavelength, said patterns being furthermore non-resonant, said surface and said structuring being configured to apply a determined phase law to a beam emitted by the antenna at a first angle (0 A ), so that said beam is deflected at a second angle (0 B ) function of said first angle and greater than said first angle.

2. Device according to the preceding claim in which said structuring is chosen from pillars (P) or grooves (Gr), said pillars or said grooves being made of at least one first dielectric material (Mat1) arranged on an inner and / or outer face of a first substrate (Subi).

3. Device according to claim 1 in which said structuring is formed of holes (H) or porosities in a second substrate (Sub2) made of a second dielectric material (Mat2).

4. Device according to the preceding claim in which the porosity is chosen from a honeycomb, a gyroid or a grid.

5. Device according to one of claims 2 to 4 further comprising at least one additional layer in contact with the first or second substrate.

6. Device according to one of the preceding claims in which a relative permittivity of a dielectric material carrying out the structuring is greater than or equal to 6.

7. Device according to one of the preceding claims in which said structuring is a combination of at least two types of patterns.

8. Device according to one of the preceding claims in which a shape of the patterns is further adapted so as to achieve impedance matching with air.

9. Device according to one of the preceding claims in which a phase excursion (cp m ax) of said phase law is strictly greater than 2K, a permittivity of a dielectric material carrying out said structuring being chosen so as to carry out said maximum phase without folding.

10. Device according to one of the preceding claims in which the electromagnetic beam has at least two different polarizations and in which the structuring is further adapted to take said polarizations into account. 1 1. Device according to one of the preceding claims in which the antenna comprises radiating elements having an electronically controlled phase, said phases being further adapted to said phase law so as to optimize a gain of the antenna.

12. Device according to one of the preceding claims in which said dimension of said patterns is less than or equal to a maximum operating wavelength divided by three.

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