Extended range offset transmission / reception device

Abstract

The invention relates to an electromagnetic wave transmission / reception device 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; - a dome (DO) of surface area S, said surface having, on at least a peripheral portion, a structure according to at least one type of pattern, said patterns having at least one dimension smaller than said central wavelength, said patterns being further non-resonant; said surface and said structure being configured to apply a determined phase law to a beam emitted by the antenna at a first angle (θA), such that said beam is deflected at a second angle (θB) that is a function of said first angle and greater than said first angle. Figure 3

Description

Title of the invention: Extended offset range transmission / reception device. SCOPE OF THE INVENTION

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

[0002] Mobile communication applications require prioritizing compactness, energy efficiency, and angular agility of antennas. The traditional approach, based on moving parabolic or similar antennas on a cradle, often fails to meet compactness requirements due to the necessary height and involves the use of complex mechanics. Therefore, planar antennas are currently being deployed on avionics and ground 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 the movement of the radiating elements within the plane of the antenna. Electronically scanned antennas have devices adapted to control the phase (and where applicable, the amplitude) of the wave radiated by each element, making it possible to control the transmission / reception angle of the wave.

[0004] The 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] The antenna gain is defined as the antenna directivity multiplied by an efficiency factor. This factor reflects the impact of losses within 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 (with reference to the isotropic antenna).

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

[0008] the maximum pointing angle of the antenna + dome device is greater than the pointing 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 pointing range from the zenith to the maximum angle, that is to say that 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 pointing angle, i.e., the angle of the beam emitted / received by the antenna, exceeds 60°. The gain degradation of a planar antenna as the pointing angle increases is caused by two main factors:

[0012] A lower directivity resulting from a reduced effective radiating aperture. Typically the directivity follows a power law of cos( 9 ) inducing gain losses, relative to the maximum gain obtained at the zenith, of at least 3.7 dB, 4.7 dB and 7.6 dB for pointing angles 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 spots.

[0014] This problematic situation is particularly common in avionics applications, given the orbits used by communications satellites and the trajectories of aircraft around the globe. For reasons of aerodynamic constraints, cost, and discretion, carrier-based antennas are ideally thin and directly integrated into the fuselage, which limits the effective antenna area at high pointing angles. This results in a lower signal level, leading either to a reduction in data rate or to a loss of connection. Maintaining the connection generally requires increasing the power emitted by the satellite or increasing the number of antennas on the carrier.

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

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

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

[0018] A first solution, illustrated in Figure 1, consists of fabricating a thickness-gradient dome 20, as described in document WO2019067474. Two impedance-matching layers 21 are deposited on the two faces of the dome. The dome 20 is positioned above the planar antenna AntO of width L. Although broadband and simple to fabricate, this solution has the disadvantage of being very bulky and heavy. For example, its implementation, as 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, results in a dome width of 3.5 x L, where L is the width of the planar antenna under consideration. This large dimension limits its use for the intended application.This is due to the need for 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 Δo; / 1" being the wavelength at the center frequency).

[0019] A second solution involves implementing Bragg gratings. The rectification of large pointing angles is then achieved very efficiently across the entire frequency band with a constant thickness of approximately 4 Ω, which is relatively large. Dielectric materials with low permittivities (2) are also used to ensure good impedance matching between the air and the dome. However, the transition to the Bragg regime at intermediate angles of incidence between the zenith and the horizon (pointing angle around 40°) leads to the coexistence of two beams (two orders of diffraction). This discontinuous deflection characteristic makes this solution more complex to implement.

[0020] A third solution is illustrated in [Fig. 2] and described in the publication by Young et al., "Dielectric Huygens Metasurface Dome Antennas," IEEE Antennas and Wireless Propagation Letters, vol. 21, no. 1 (2022). It is based on the implementation of a Huygens metasurface 23, based on dielectric resonators 22. Indeed, for certain dimension sets, these resonators exhibit a superposition of electric and magnetic dipole resonances. This superposition makes it possible to obtain unity transmission in the direction of wave propagation. Thus, the patterns can play the role of the secondary sources proper to the Huygens-Fresnel theorem. Each of these dimension sets also offers different phase values ​​in transmission. It is therefore possible to achieve a phase profile in transmission TTO) by dimensioning the resonators (shape, volume, material) in such a way that at the resonance frequency of the patterns the electromagnetic beam EBO is perfectly deflected without reflection.

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

[0022] The phase law ensuring the dome's deflection function is thus obtained with a thin, constant thickness and suitable 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 center resonance frequency fO. The frequency bandwidth of such a dome is therefore too small; the work carried out shows that the beam deflection is maintained over approximately 1% of the center frequency fO for the intended application. Furthermore, the fabrication of this type of component has not yet been demonstrated and remains complex.

[0023] A fourth approach consists of fabricating a solid hemispherical lens with a refractive index gradient, as described in US4333082. This solution relies on the progressive refraction of the electromagnetic wave emitted by the antenna through different dielectric layers. This approach makes it possible to obtain a very large angular coverage, even exceeding 90° of pointing. However, this approach requires a significant increase in the weight of the device.

[0024] One object 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 dome of surface area S, said surface having, on at least a peripheral part, a structure according to at least one type of pattern, said patterns having at least one dimension smaller 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 which is a function of 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 in at least one 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 in 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 the first dielectric material or of the second dielectric material 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 air.

[0033] According to one embodiment, a maximum phase of said phase law is strictly greater than 2ir, a permittivity of the first or second dielectric material being chosen so as to realize said maximum phase without folding.

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

[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 an antenna gain.

[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 embodiments of the device of the invention: these examples are not limiting to the scope of the invention. These embodiments present both the essential features of the invention and additional features related to the embodiments considered.

[0038] The invention will be better understood and other features, objectives and advantages thereof will become apparent from the following detailed description and with reference to the accompanying drawings given by way of non-limiting examples and in which:

[0039] The [Fig.1] already cited illustrates a dome for a planar antenna with varying thickness according to the prior art.

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

[0041] Fig. 3 illustrates the electromagnetic wave transmission / reception device according to the invention.

[0042] Fig. 4 illustrates a pillar structure.

[0043] Fig. 5 illustrates a grooved structure.

[0044] Fig. 6 illustrates a structure of holes in a substrate.

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

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

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

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

[0049] Fig. 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 improvement in directivity expected through increasing the effective area of ​​the antenna.

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

[0052] Figure 13 represents an example of normalized directivity of a dipole antenna array as a function of the pointing angle at different frequency points, with and without the proposed dome. DETAILED DESCRIPTION OF THE INVENTION

[0053] The electromagnetic wave transmission / reception device 10 according to the invention is illustrated [Fig. 3]. It comprises a planar antenna Ant conventionally fabricated on a substrate Sub. The Ant antenna is reconfigurable, configured to emit at least one electromagnetic beam EB at a plurality of angles. The Ant antenna can thus emit one beam (single-beam antenna) or several beams simultaneously (multi-beam antenna). At a given time t, one or more transmission (or reception) angles are chosen, the value of these angles being controllable. In the following, we consider a beam EB, but the invention also relates to a multi-beam transmission / reception device. The electromagnetic beam EB exhibits a The X wavelength and a frequency f are defined. The EB beam exhibits frequencies f within an operating frequency range between a minimum and a maximum frequency. Typically, this range is in the interval [0.9 f0; 1.1 f0] for a center frequency f0 that can be on the order of GHz to a few tens of GHz, although some applications may require wider frequency bands.

[0054] The planar antenna can be mechanically or electronically scanned.

[0055] The device 10 also includes a DO dome equipped with a continuous deflection function. It includes a surface S, the surface having, on at least a peripheral part, a structure according to at least one type of pattern. 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.

[0056] The surface S and the pattern structure are configured to apply a specific phase law to a beam emitted by the antenna at a first angle 0A, such that the beam is deflected at a second angle 0B, a function of the first angle and greater than said first angle. This condition illustrates the deflection function of the assembly (surface, patterns). The deflection condition is expressed here for transmission, but conversely, the proposed solution also works for reception.

[0057] Thus, the phase profile is obtained by structuring a dielectric material at the sub-wavelength scale without introducing 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 refractive index). A dome is thus created in an artificial material exhibiting a gradient of effective permittivity.

[0058] 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.

[0059] 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 impedance matching.

[0060] The concept of artificial material and effective permittivity is described for example in the document 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 to adjust its effective permittivity by playing on its structuring at a sub-wavelength scale.

[0061] According to this principle, the dimensions of the motifs to be positioned at each point of the dome are identified so as to implement the desired phase law as faithfully as possible. In particular, the phase law is implemented with the phase of the coefficient of The complex transmission of the patterns, each considered within an infinitely periodic planar environment, is calculated. This transmission coefficient can be estimated analytically for simple cases or using numerical calculation tools for more complex ones. The structuring is designed to obtain patterns with low reflectivity to the electromagnetic wave within the band of interest. When implementing the phase law using the complex transmission coefficient, care is taken to prioritize gradual variations in geometry along the dome to verify, as much as possible, the assumption of local periodicity under which the transmission coefficients were extracted. Furthermore, it is also possible to consider the angle of incidence of the electromagnetic field on the dome for each pattern, and thus to use appropriate transmission coefficients.

[0062] The device according to the invention makes it possible to provide a significant improvement in gain (> 1 dB) for large pointing angles, typically greater than 60° and / or to extend the pointing range (see for example the numerical calculation further on).

[0063] It also allows for a reasonable size. According to one embodiment, accessible with the dome according to the invention, the width D of the dome is less than or equal to twice the width L of the antenna. According to another embodiment, the dome has a thickness between 2 and 3X, where 2 is the wavelength at the maximum operating frequency.

[0064] The non-resonant nature of the patterns of the structuring 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 center frequency fO.

[0065] According to a first embodiment also illustrated [Fig. 3], the structuring motifs are pillars P made of a first material Matl deposited on a first substrate Subi. The substrate can be made of the same material Matl as the pillars, or of another material MatS with a lower permittivity. An example of pillar structuring is also illustrated [Fig. 4]. According to one embodiment, the pillars have a pointed shape, which helps to limit reflection phenomena, even when the dielectric material has a high permittivity (typically around 7 to 10).

[0066] According to a second embodiment illustrated [Fig. 5], the structuring patterns are grooves Gr made of Matl material deposited on a first substrate Subi. The substrate may be made of the same Matl material as the grooves, or of another MatS material with a lower permittivity. The grooves may have the advantage of being easier to manufacture by mechanical machining.

[0067] The pillars or grooves are arranged on an inner and / or outer face of the first Subi substrate.

[0068] According to a third embodiment illustrated [Fig. 6], the structure is formed by holes H in a second substrate Sub2, the substrate Sub2 being made of a second material Mat2. The holes can be made by drilling a solid material and offer good mechanical strength.

[0069] According to a fourth embodiment illustrated [Fig. 7], the structure 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 produced by additive manufacturing.

[0070] 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 optionally other stacked additional layers. The additional layer(s) may be solid or structured. These layers are, for example, refractive index adaptation or external protection layers. According to one embodiment, an additional layer has a second type of pattern structure. The phase law is then determined 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.

[0071] 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).

[0072] The dome according to the invention can also be produced by machining or injection.

[0073] According to one embodiment, the structuring is a combination of at least two types of patterns, as illustrated [Fig.7], these patterns can be in the same material or in two different materials.

[0074] 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, as illustrated in [Fig. 3]. According to another embodiment illustrated in [Fig. 8], the surface S is elliptical.

[0075] According to another embodiment illustrated [Fig. 9], the surface is freely defined by a set of points; it is then said to be "non-canonical". This freeform shape allows for a relaxation of design constraints by providing a large number of degrees of freedom in design and optimization.

[0076] Figure 10 illustrates a three-dimensional view of a spherical dome according to the invention made with pillars, devoid of motifs on its central part (top of the dome).

[0077] According to one embodiment, the dome according to the invention has rotational symmetry. According to another embodiment, it has a cylindrical symmetry structure (single-plane sweep).

[0078] The pattern distribution on the conformal surface is locally adjusted to obtain the desired behavior (phase law) and optimize performance. The absence of a pillar at the top of the dome limits the divergent effect when the antenna is pointed at the zenith, thus limiting gain loss. Therefore, the patterns are not necessarily present in the central (top) area of ​​the dome, as illustrated in Figures 3 and 8 to 10.

[0079] 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 pointing angle 9B when the dome is designed for an angle at the antenna exit 9A relative to the vertical. Figure 11 illustrates the increase in directivity geometrically.

[0080] For the example in Figure 11, we consider a structure invariant in the dimension normal to the pointing 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 it.

[0081] The design point is defined as the pair (angle at the exit of the planar antenna, angle at the exit of the dome) for which the phase law is initially determined.

[0082] Trigonometric analysis shows that the maximum improvement of M at the design point is expressed as follows: [°083] R f) 3 L'" 1 VB ) Lwsittg) co^f)^cos(0A-a)

[0084] Where:

[0085] 9a angle at the exit of the planar antenna and 9B angle at the exit of the dome

[0086] a is the inclination of the dome relative to the planar antenna:

[0088] h being the distance between the top of the dome and the antenna,

[0089] D width of the dome.

[0090] This improvement is graphically visible by the ratio of the two lengths illustrated in [Fig. 11]. L” ' corresponds to the projected length of the antenna + dome assembly for the beam deflected in the direction 0B, and L.cos0B to this same quantity for the antenna alone, assuming that it orients its beam in this same direction 0B.

[0091] Here, the assumption is made that the height h is sufficient for only one face of the dome to be illuminated, i.e.:

[0092] h 'i__■ n:> 2tanfL

[0093] Thus, for a dome designed to deflect a beam oriented at = 55° at the antenna exit to an angle of = 80° with a dome of width D = 1.3*L (L being the width of the antenna) and of height h = 0.35*D, a directivity improvement of 3.7 dB is expected at 80°, from which the deflection efficiency must be subtracted, which depends strongly on the choice of implementation (typically 1 to 2 dB).

[0094] The deflection of the beam emitted by the antenna in the direction given by 6b at the dome exit is obtained by implementing a phase gradient on the dome. This deflection follows, in the ideal case, the generalized Snell's law, explained for example in the document by Steyskal et al., "On the gain-versus-scan trade-offs and the phase gradient synthesis for a cylindrical dome antenna," IEEE Trans. Antennas Propag., Vol. AP-27, No. 6 (1979). This law states that a beam incident on the dome at an angle to its normal 6A is deflected in the exit direction given by the angle qb by means of a phase gradient in transmission, where x is the parameter for the direction tangential to the dome:

[0095] sin(8B')=sin(8A')+^

[0096] being the free-space wavenumber at the dimensioning frequency.

[0097] OnaeB = eB-aet6A=6A-a

[0098] The idea behind the invention is to structure a dielectric material on a sub-wavelength scale in order to obtain the desired phase variation at the frequency of interest.

[0099] 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, this may involve increasing the maximum radiation angle of the antenna while minimizing the impact on 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 may also be incorporated. Generally, this optimization uses both the phase distribution and the dome shape (surface S) as adjustment parameters, provided that the application's size constraints are respected.

[0100] The occurrence of unwanted diffraction phenomena is avoided when the structuring allows for a large achievable phase excursion, thus preventing folding at more or less periodic intervals. Indeed, this folding introduces discontinuities that disrupt and degrade the operation of the device. For example, for pillar-type patterns, a Phase folding corresponds to an abrupt change in diameter between two adjacent patterns, typically from the wider pillar to the thinner pillar.

[0101] Either <pmax la phase maximale de la loi de phase. Typiquement on a <pmax>2ir, and we seek to carry out all phases above 2ir without folding.

[0102] This is all the easier when the thickness of the dome or the permittivity of the material used is large. For space reasons, a dome that is too thick is not desirable. Thus, preferably, the permittivity of the first dielectric material Mat1 or of the second material Mat2 is greater than or equal to 6.

[0103] For example, in the case where the structuring consists of juxtaposing elementary cells characterized by an adjustable filling of dielectric material, the effective permittivity associated with each of these cells is defined as sr-eff, which takes a maximum value for the highest filling. Thus, for a given dome thickness z, the phase excursion <pmax atteignable est donnée par la formule : m l.l,jnax 'imix \V î /

[0104] Thus, for a total cell height limited to 4 (including the matching portion), a phase excursion of 360° is obtained from a relative permittivity of approximately 6, when the cell filling rate is 100%. To obtain a phase excursion of 720°, a relative permittivity close to 14 is required.

[0105] The use of materials with high permittivities may, however, necessitate the addition of impedance matching layers on either side of the dome to limit reflections, typically quarter-wave plate dielectric layers. These layers may be solid or structured (effective permittivity).

[0106] According to one embodiment, the shape of the motifs is adapted to achieve impedance matching with air. 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 impedance matching layer.

[0107] The dimensions of the cell and the manufacturing constraints define the maximum dimensions of the pattern integrated into the cell.

[0108] According to one embodiment the maximum phase <pmax de la loi de phase est strictement supérieure à 2ir, et la permittivité du premier matériau diélectrique Matl est choisie de manière à réaliser cette phase maximale sans repliement.

[0109] Several types of structuring allowing adjustment of the dielectric material content can be implemented, as described previously: pillars, holes, porosities...

[0110] For example, it is possible to vary the size of a motif. Figure 12 shows the relationship between the phase introduced at a frequency of 29 GHz and the motif size for pillar and hole-type cells. To facilitate representation, the motif size is in both cases an increasing function of the amount of dielectric. For The pillar size here refers to its diameter. A variation in height, or a combination of both, is also possible. The hole size is the difference between the cell's width and its diameter. The cells have a fixed total height of 14.5 mm and a period of 2.6 mm.

[0111] The pillar, 12 mm high, is made of a Matl material with a permittivity of 7.5 and rests on a MatS support material with a permittivity of 2.3 and a thickness of 3 mm. A pyramid is added to the top of the pillar to match the air impedance to that of the pillar material. The hole is drilled in a material with a permittivity of 7.5.

[0112] Curves 121 and 122 illustrate the pattern size, respectively the diameter for the pillars, and the difference between cell size and hole diameter for the holes, required to obtain a given phase value. It can be seen that a phase value <pmax de l’ordre de 600° est atteinte avec ces deux types de motifs et une valeur de permittivité du premier matériau de 7.5.

[0113] It is also possible to play on the density / distribution of the motifs for the realization of the phase law, possibly in combination with a variation of the diameter or of another parameter of the shape of the motif.

[0114] 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 must be identical for two orthogonal linear polarizations (phase law and amplitude of the transmission coefficient).

[0115] In some cases, the dome may not fulfill this condition. To compensate for this effect, according to one embodiment, the structuring parameters (pattern type(s), 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.

[0116] The inventors have also established that the best results were obtained when the dimension of the patterns (and therefore of the cell) is less than X / 3, where 2 is the wavelength of the electromagnetic wave in free space at the maximum operating frequency.

[0117] Figure 13 represents, by way of example, the normalized directivity Dim of a network of parallel dipole antennas as a function of the pointing angle Dep at different points of frequencies 18, 24 and 28 GHz, with and without dome.

[0118] The source antenna is a linear array of 60 dipoles separated by 0.472, where A is the wavelength corresponding to the highest operating frequency, here 28 GHz, giving a total width L of approximately 28-1. The amplitude of the dipoles is modulated by a Hamming apodization. This antenna illuminates a dome with a single radius of curvature, in the plane H of the array, with a footprint D = 1.13*L, or 31.42, and a height h = 0.3L, or 8.32 (internal height of the dome).

[0119] The pillars are the same as those described in the example in [Fig.12].

[0120] Curves S18, S24, and S28 correspond to the case without a dome for frequencies of 18, 24 and 28 GHz respectively.

[0121] Curves D18, D24 and D28 correspond to the case with dome for frequencies 18, 24 and 28 GHz respectively.

[0122] It can be seen that the presence of the dome extends the antenna's pointing angle, limited to 77°, to 86°. Furthermore, the antenna's directivity is increased (compared to the case without a dome) from a pointing 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 to be around 0.5 dB.

[0123] With the maintenance of the increase in the maximum pointing angle for all frequency points from 18 to 28 GHz, the graph demonstrates the broadband behavior of the dome, here greater than 40%.

[0124] Thus, in this example, we see that the device according to the invention:

[0125] allows extending the pointing range beyond 70° and / or increasing the antenna gain at high pointing angles.

[0126] is compact with a width < 2 x the antenna diameter and a thickness of approximately 1.62.

[0127] is broadband (>20% relative frequency bandwidth),

[0128] is feasible on a conforming surface thanks to its "all-dielectric" nature and the use of additive manufacturing techniques,

[0129] does not exhibit angular selectivity and therefore preserves the continuity of the antenna's pointing.

[0130] features a phase profile that can be adjusted locally on a sub-wavelength scale in order to limit gain degradations around the zenith.

[0131] According to one embodiment, the antenna is electronically scanned. It comprises radiating elements with electrically controlled phase. It is possible to integrate the effect of the dome into the phase control law of these radiating elements for each viewing angle, and thus increase the gain of the antenna-dome assembly over the entire angular range of the target. For example, it is possible to partially compensate for the degradation observed at the zenith.< / pmax>

Claims

Demands

1. Electromagnetic wave transmission / reception device 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 (XO), - a dome (DO) of surface area S, said surface having, on at least a peripheral portion, a structure according to at least one type of pattern, said patterns having at least one dimension smaller than said central wavelength, said patterns being further non-resonant, said surface and said structure being configured to apply a determined phase law to a beam emitted by the antenna at a first angle (^), such that said beam is deflected at a second angle (¾) that is a function of said first angle and greater than said first angle, - a maximum phase ( <pmax) de ladite loi de phase étant strictement supérieure à 2ir,-a permittivity of a dielectric material performing said structuring being chosen so as to achieve said maximum phase without folding.

2. Device according to the preceding claim wherein said structuring is selected from pillars (P) or grooves (Gr), said pillars or said grooves being made of at least a first dielectric material (Matl) 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) in a second dielectric material (Mat2).

4. Device according to the preceding claim wherein the porosity is selected from a honeycomb, a gyroid or a grid.

5. Device according to any 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 any one of claims 2 to 5 wherein a relative permittivity of the first dielectric material or of the second dielectric material is greater than or equal to 6.

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

8. Device according to any one of the preceding claims wherein a form of the patterns is further adapted to achieve impedance matching with air.

9. Device according to any one of the preceding claims wherein the electromagnetic beam has at least two different polarizations and wherein the structure is further adapted to take into account said polarizations.

10. Device according to any one of the preceding claims wherein the antenna comprises radiating elements having an electronically controlled phase, said phases being further adapted to said phase law so as to optimize an antenna gain.

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

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