Electromagnetic system with angular deviation of the main dispersion lobe of an antenna.

Abstract

The invention relates to an antenna system comprising: a ground plane with a cavity covered with a dielectric, magnetic, or magnetodielectric substrate; an antenna disposed on the cavity; a peripheral absorbing ring disposed between the antenna and the walls of the cavity; and an absorbing half-lens, comprising a basic element covering substantially half of the cavity.

Description

Scope of the invention

[0001] The present invention relates to the field of antennas. More specifically, it relates to the control of the radiation pattern, and in particular the angular direction of the main radiation lobe of antennas. Previous state of the art

[0002] In an airborne and / or naval system, electromagnetic communication is the dominant mode due to its accuracy, ease of control, and wide range of capabilities. An antenna is an essential component of a wireless system. For communication purposes, an antenna is ideally a broadband antenna with circular polarization or dual linear polarization.

[0003] Due to space constraints on carriers, an antenna system must be as compact as possible. One possible solution is to place the antenna in a compact cavity. The cavity makes the radiation unidirectional and provides the antenna with electromagnetic shielding from surrounding electronic systems.

[0004] However, a compact cavity can impair the antenna's natural radiation pattern, leading to poor matching, incorrect polarization, ripples in the radiated gain, etc. One possible design involves mounting a spiral antenna on a cavity filled with an electromagnetic absorber. Such an antenna has a unidirectional radiation pattern, along the line of sight, i.e., along the antenna's radio axis.

[0005] When an antenna placed under a flying aircraft is pointed towards the ground, the main beam or radiation lobe of the antenna must be pointed slightly forward (for example) rather than directly towards the ground, that is, it must be pointed forward at an angle to the perpendicular of the ground.

[0006] Another objective of this angular deflection is to avoid interference between the aircraft's various antennas, including between a transmitting and a receiving antenna. Indeed, broadband antennas typically have fairly wide radiation lobes, which can lead to undesirable interactions between nearby antennas.

[0007] In a spiral antenna system loaded by an electromagnetic absorber placed within the antenna cavity (the antenna cavity being the area between the bottom of the radiating circuit substrate and the lower reflector plane (or ground plane)), the antenna is physically tilted to meet this requirement. However, this physical tilt may not be feasible in the aircraft design on which the antenna is to be mounted. Using an antenna array is another possible solution, but it is unsuitable in environments where space is a significant constraint.

[0008] Another solution involves applying an angular deflection to the beam. Electronic deflection consists of inducing a deviation of the main beam from the antenna's radio axis. In order to operate over a wide frequency band, such electronic deflection must be consistent across a broad frequency range, maintaining good impedance matching, polarization purity, and without degradation of the radiated gain in the desired direction, so that the antenna can be classified as a broadband antenna.

[0009] The problem of beam deflection from an antenna has been partially addressed by prior art.

[0010] US patent application number 6,947,010 discloses an antenna with an eccentric spiral structure. The design principle of this antenna is similar to that of an Archimedean spiral antenna, except that on one side the spaces between the elements are larger than those on the other. This device allows the antenna beam to be oriented, but has the disadvantage of being bulky and unable to ensure uniform deflection over a wide frequency band.

[0011] The paper by P. Deo, A. Mehta, D. Mirshekar-Syahkal, and H. Nakano, "An HIS-Based Spiral Antenna for Pattern Reconfigurable Applications," in IEEE Antennas and Wireless Propagation Letters, vol. 8, pp. 196-199, 2009, describes a single-element spiral antenna with four open-circuit switches mounted on a high-impedance structure to achieve a 360° sweep angle. The four switches are turned on and off to orient the beam in different directions. However, this system only works for a single-element antenna at a single frequency. Furthermore, the desired angular deflection is not always accurately achieved depending on the switch combinations and angles used. This solution also has the disadvantage of requiring active components to drive the switches.

[0012] The papers H. Nakano, T. Abe, and J. Yamauchi, "A Metaspiral Antenna for Azimuth Beam Steering," 2019 International Symposium on Antennas and Propagation (ISAP), Xi'an, China, 2019, pp. 1–3, and Tomoki Abe, Junji Yamauchi, and Hisamatsu Nakano, "Steering of the Circularly Polarized Beam from a Spiral Antenna," IEICE Communications Express, Article ID 2019SPL0014, [Advance publication] Released February 20, 2020, Online ISSN 2187-0136, also disclose solutions for the angular deflection of an antenna beam. In the first paper, a rectangular spiral antenna made of metamaterial is used, while in the second, a conventional cavity spiral antenna is used to demonstrate steering performance. However, these solutions are inherently narrowband. Certain combinations of input amplitudes and phases do indeed produce different angles of deviation at different frequencies.

[0013] Other solutions involving spiral antennas with broadband characteristics have been proposed, such as applications JP2012205144 A and US5162806.

[0014] However, none of the prior art systems are capable of applying beam deflection, nor of altering the main lobe of the radiation pattern of a wire broadband antenna over a wide frequency band.

[0015] Therefore, an antenna system is needed that can generate angular deflection of the antenna beam over a wide frequency band. It is also needed that the antenna system can generate beam deflection while minimizing its size. Summary of the invention

[0016] To this end, the invention relates to an antenna system comprising: a ground plane with a cavity covered with a dielectric, magnetic or magnetodielectric substrate, the cavity comprising an opening and walls; an antenna disposed on the dielectric, magnetic or magnetodielectric substrate; a peripheral absorbing ring disposed between the antenna and the walls; an absorbing half-lens having the shape of an angular sector (or angular segment), comprising a basic element covering a first part of the cavity opening, a second part of the cavity opening not being covered by said basic element.

[0017] Advantageously, the absorbing half-lens includes an annular element forming an extension of the peripheral absorbing crown on the second part of the aperture.

[0018] Advantageously, in which the first part of the cavity opening corresponds to half of the cavity opening

[0019] Advantageously, the absorbing half-lens comprises at least one circular sector element whose thickness varies according to the distance to the center of the half-lens.

[0020] Advantageously, the absorbing half-lens comprises a plurality of circular sector elements whose thickness is defined by an increasing function of an angular distance from the edges of the lens.

[0021] Advantageously, each circular sector element is defined by a thickness function that increases and then decreases as a function of a distance from the center of the half-lens.

[0022] Advantageously, at least one element among the peripheral absorbing ring and the half-lens is made of a partially absorbing dielectric material.

[0023] Advantageously, the dielectric material partially comprises carbon.

[0024] Advantageously, the antenna is a spiral antenna, a sinusoidal antenna, or a periodic antenna.

[0025] Advantageously, the antenna is defined by an Archimedean spiral.

[0026] Advantageously, the antenna is a broadband antenna, allowing a constant deflection angle to be obtained over the entire operating frequency band of the antenna.

[0027] Advantageously, the antenna system comprises: a first device including the ground plane, the antenna and the peripheral absorbing ring; a second device including the absorbing half-lens.

[0028] Other features, details and advantages of the invention will become apparent from the description provided with reference to the accompanying drawings given by way of example, which represent, respectively: [Fig.1a ] a first example of an antenna system in a set of embodiments of the invention; [ Fig.1b ], a second example of an antenna system in a set of embodiments of the invention; [ Fig.2 ], an example of a spiral antenna in a set of embodiments of the invention; [ Fig.3 ], an example of a so-called reference section of an antenna system in a set of embodiments of the invention; [ Fig.4 ], an example of a metallic cavity in a set of embodiments of the invention; [ Fig.5 ], an example of an absorbing peripheral ring in a set of embodiments of the invention; [ Fig.6 ], an example of a basic element of an absorbing half-lens in a set of embodiments of the invention; [ Fig.7 ], an example of an annular element in a set of embodiments of the invention. [ Fig.8 ], an example of a set of circular sector elements of an absorbing half-lens in a set of embodiments of the invention; [ Fig.9 ], an example of a profile view of a set of circular sector elements of an absorbing half-lens in a set of embodiments of the invention; [ Fig.10 ], an example of an overview of an antenna system comprising a set of circular sector elements of an absorbing half-lens in a set of embodiments of the invention. Fig.11a ], an example of radiation patterns of a state-of-the-art antenna at different frequencies, without deflection of the antenna beam; [ Fig.11b ], an example of radiation patterns of an antenna at different frequencies, with deflection of the antenna beam by an antenna system in a set of embodiments of the invention; [ Fig.12 ], two cross-sections of a 3D representation of the main lobe of the radiation pattern of an antenna deflected by an antenna system in a set of embodiments of the invention; [ Fig.13 ], an example of a deflection angle obtained by an antenna system as a function of frequency in a set of embodiments of the invention; [ Fig.14 ], an example of an angular deflection angle obtained by an antenna system as a function of frequency in a set of embodiments of the invention; [ Fig.15 ], an example of antenna gain obtained by an antenna system as a function of frequency in a set of embodiments of the invention; [ Fig.16 ], an example of the axial ratio obtained by an antenna system as a function of frequency in a set of embodiments of the invention; [ Fig.17 ], an example of -3dB lobe width obtained by an antenna system as a function of frequency in a set of embodiments of the invention; [ Fig.18 ], an example of impedance matching obtained by an antenna system as a function of frequency in a set of embodiments of the invention.

[0029] There figure 1a represents a first example of an antenna system in a set of embodiments of the invention.

[0030] The Sys1a antenna system comprises a ground plane with a cylindrical cavity Cav filled with a dielectric, magnetic, or magnetodielectric substrate. The cavity includes an aperture and walls. The Sys1a antenna system also includes an antenna Ant disposed on the dielectric, magnetic, or magnetodielectric substrate.

[0031] The invention will be described by way of example where the antenna is a planar antenna, but the invention is not restricted to these examples, and 3D antennas could be used.

[0032] In a set of embodiments of the invention, the substrate is a so-called low-loss dielectric substrate, for example a substrate whose dielectric loss angle tangent (tanδ) is less than 10⁻². This substrate may also be either magnetic or magnetodielectric.

[0033] The cavity can also be filled with electromagnetic absorber and / or a partial resistive film can be placed in it.

[0034] Ant antennas can be of various types, such as planar antennas. For example, a planar Ant antenna can be a spiral antenna, a sinuous antenna, or a planar periodic antenna. It can, for instance, be composed of different current rings corresponding to different frequencies, with the perimeter of a given ring equal to the wavelength of the corresponding frequency. The outer rings thus correspond to low frequencies, and the inner rings to high frequencies.

[0035] This type of spiral therefore allows the antenna to operate over a wide frequency band, within which the different rings contribute to the radiation for different frequencies depending on their diameter (for a wavelength λ, it is a ring-shaped area of ​​circumference λ that will contribute to the radiation).

[0036] The Ant antenna can be a transmitting or receiving antenna.

[0037] There figure 2 represents an example of a spiral antenna in a set of embodiments of the invention.

[0038] In a set of embodiments of the invention, the antenna has, for example, the shape of an Archimedean spiral defined by the equation r ( φ ) = e aφ< , Or r ( φ ) is the radius of the spiral at a location φ , And a is a constant.

[0039] There figure 2 represents an example of such a spiral antenna comprising two strands Strand1 and Strand2, said antenna being printed on the dielectric substrate Subs of thickness h1 and diameter d1.

[0040] The X, Y, and Z axes represent three axes of an orthogonal coordinate system, where Z is the antenna axis. The X and Y axes correspond to the antenna plane and can be defined, for example, by the geometry of the spiral's excitation points. By convention, these same three axes, X, Y, and Z, will be represented in several figures. To facilitate understanding, the "top" of the system will be considered to correspond to high values ​​on the z-axis, and the "bottom" to low values. Thus, an element will be considered "on" or "above" another if its position is higher on the z-axis, and conversely, "below" or "under" another if its position is lower on the z-axis.

[0041] There figure 3 represents an example of a so-called reference section of an antenna system in a set of embodiments of the invention.

[0042] The so-called reference section comprises a metallic cavity Cav, onto which the dielectric substrate Subs is placed, and in which the planar antenna Ant is printed. As mentioned above, the antenna can operate at different frequencies, and at a given frequency, a specific area of ​​the antenna will participate in the radiation. For example, in a spiral antenna, for a wavelength λ, a ring-shaped area of ​​circumference λ will contribute to the radiation.

[0043] The Sys1a antenna system also includes a peripheral absorbing ring, not visible on the figure 3 , positioned between the antenna and the walls of the cavity.

[0044] The peripheral absorbing ring helps to trap the end-strand effects, thus limiting the open-circuit effect. Indeed, these effects, by recombining locally with the rest of the radiating circuit towards the center of the antenna, can lead to mismatch and a loss of radiation efficiency depending on the frequency.

[0045] Returning to the figure 1a The Sys1a antenna system also includes an absorbing half-lens Lent1a having the shape of an angular sector and comprising a basic element covering substantially a first part of the cavity opening, a second part of the cavity opening not being covered by said basic element.

[0046] In some embodiments, the first part of the cavity opening corresponds to half of the cavity opening.

[0047] For example, the absorbing half-lens can cover: Between 45% and 55% of the cavity surface; And, more preferably, between 48% and 52% of the cavity surface; And, more preferably, between 49% and 51% of the cavity surface; And, more preferably, between 49.5% and 50.5% of the cavity surface; And, more preferably, between 49.9% and 50.1% of the cavity surface; And, more preferably, half of the cavity surface.

[0048] Thus, the electromagnetic waves emitted by the antenna will be affected, in the half of the cavity covered by the half-lens, by a phase shift, while they will not be modified in the half not covered by the half-lens.

[0049] This creates a phase and amplitude imbalance between the two halves of the cavity opening, thus generating a deviation from the antenna axis.

[0050] This therefore makes it possible to obtain a deflection of the antenna beam, while maintaining a compact and passive system.

[0051] The peripheral absorbing ring and the absorbing half-lens can be joined together, forming a single absorbing element, or be formed from two separate elements.

[0052] The peripheral absorbing ring and the absorbing half-lens can be made of a partially absorbing dielectric material.

[0053] For example, an absorbent material containing carbon can be used. This type of material has the advantage of possessing absorbent properties while also being compatible with 3D printing, making the antenna system more flexible to reproduce and modify.

[0054] More generally, the half-lens can be integral with the Cav cavity and the Ant antenna, in which case the Sys1a system is formed from a single device.

[0055] In a set of embodiments of the invention, the half-lens can instead be located in a device independent of that of the antenna.

[0056] For example, the half-lens can be positioned slightly above the antenna. This allows the half-lens to be integrated into existing antenna systems. For instance, the half-lens can be integrated into a radome that is added above a pre-existing antenna.

[0057] There figure 4 represents an example of a metallic cavity in a set of embodiments of the invention.

[0058] In a set of embodiments of the invention, the cavity Cav is cylindrical in shape, with a diameter d1 and a height h2. The metallic cavity has a bottom 410 and metallic walls 420.

[0059] However, this shape is given only as a non-limiting example, and other cavity shapes are possible. For example, the cavity could be square. The cavity's ground plane could be planar or not. In the latter case, the cavity's depth might be shallower towards its center. For example, the cavity could be conical.

[0060] There figure 5 represents an example of an absorbing peripheral ring in a set of embodiments of the invention.

[0061] In a set of embodiments of the invention, the peripheral absorbing ring Cour is in the form of a hollow cylinder.

[0062] In the example of the figure 5 The hollow cylinder has a height h2 and an outside diameter d1, respectively identical to the height and outside diameter of the metallic cavity Cav shown in figure 4 , and a thickness w1, corresponding to an inner diameter d1 - w1.

[0063] The peripheral absorbing ring shown in figure 5 can therefore be placed in the metallic cavity shown in figure 4 , and absorb electromagnetic waves between the antenna and the lateral 420 of the metallic cavity.

[0064] There figure 6 represents an example of a basic element of an absorbing half-lens in a set of embodiments of the invention.

[0065] The basic element Bas of the absorbing half-lens is presented here as a half-cylinder of thickness h4 and diameter d2 > d1. The basic element can therefore close half of the metallic cavity.

[0066] The basic element thus contributes to the deflection of the beam.

[0067] In certain embodiments, the basic element can serve as a support for other lens elements such as those shown in figure 8

[0068] In other embodiments of the invention, the base element is the only element of the half-lens that closes the metallic cavity. In these embodiments, the height of the base element can be defined according to the desired beam deflection. In particular, certain heights can favor beam deflection in certain frequency bands; the height h4 can therefore be defined according to a frequency band to be preferentially deflected.

[0069] The design of the basic element presented in figure 6 is provided as an example only, and other designs are possible. For example, the basic element could be formed from a half-cylinder of diameter d1 slightly recessed into the metal cavity, or the annular element shown in figure 7 , and a semi-cylinder of diameter d2 as shown in figure 6 In general, the design of the basic element can be guided by the following considerations: The base element must obturate half of the metallic cavity, or half of the hollow part of the peripheral annular crown; the base element may have a constant height, for the part obturating the metallic cavity, or half of the hollow part of the peripheral annular crown.

[0070] There figure 7 represents an example of an annular element in a set of embodiments of the invention.

[0071] In a set of embodiments of the invention, the absorbing half-lens is arranged on an annular element forming an extension of the peripheral absorbing ring out of the cavity to the base element. According to the embodiments of the invention, the absorbing half-lens and the annular element may be joined together to form a single element, or be two separate elements placed side by side.

[0072] In the example of the figure 7 The annular element Ann is a hollow cylinder with an outer diameter d1, a thickness w1, and a height h3. It is therefore a hollow half-cylinder with the same outer diameter and thickness as the hollow half-cylinder of the peripheral ring shown in figure 5 , which extends it out of the metal cavity, up to the base element, and thus forms a support for the base element.

[0073] This annular element therefore absorbs the reflections from the antenna, while fixing the other elements of the lens and maintaining a fixed distance between the antenna and the base element of the half-lens.

[0074] When the half-lens and the annular element are joined, this also allows the half-lens to be manufactured without requiring a mechanical interface between its lower face and the upper face of the radiating circuit. In other words, the monobloc assembly of the half-lens and the annular element (for example, by 3D printing) reduces the assembly interfaces along the axis perpendicular to the radiating circuit, while also allowing precise selection of the air gap between the upper face of the radiating circuit and the lower face of the half-lens: for example, there is no need for a foam-glue-glue film between the radiating circuit and the half-lens.

[0075] There figure 8 represents an example of a set of circular sector elements of an absorbing half-lens in a set of embodiments of the invention.

[0076] In a set of embodiments of the invention, the absorbing half-lens comprises at least one circular sector element whose thickness varies according to the distance to the center of the half-lens.

[0077] As mentioned above, an antenna, whether transmitting or receiving, can process frequencies that depend on its distance from the center of the antenna, and therefore from the center of the half-lens. For example, a spiral, wavy, or log-periodic antenna has an active area at a given wavelength shaped like a ring whose diameter corresponds to that wavelength. The lower rings correspond to low frequencies, and the inner rings to high frequencies. Simultaneously, the thickness of the lens allows the beam to be deflected to varying degrees depending on the frequencies of the electromagnetic waves.

[0078] Adjusting the thickness of the half-lens according to the distance from the center allows the beam deflection to be locally adapted to the frequency of the waves emitted at a given distance from the antenna center. This makes it possible to obtain a beam deflection that is coherent over a wide frequency band.

[0079] In a set of embodiments of the invention, the half-lens comprises a plurality of circular sector elements whose thickness is defined by an increasing function of an angular distance from the edges of the lens.

[0080] In the example of the figure 8 The half-lens comprises 9 circular sector elements, arranged symmetrically, with, from the edges of the half-lens: two circular sector elements 8e; two circular sector elements 8d; two circular sector elements 8c; two circular sector elements 8b; one circular sector element 8a.

[0081] Each circular sector element is defined by a thickness profile that depends on the distance to the center of the half-lens, and the thickness is defined by an increasing function of an angular distance from the edges of the lens (the angular distance being, for example, represented by the angle α starting from the right edge of the half-lens), that is to say, in the example of the figure 8 , at a given distance from the center, the thickness of element 8a will be greater than the thicknesses of elements 8b, which are themselves greater than the thicknesses of elements 8c, which are themselves greater than the thicknesses of elements 8d, which are themselves greater than the thicknesses of elements 8e.

[0082] Using a plurality of circular sector elements whose thickness is defined by an increasing function of the angular distance from the lens edges limits the frequency dependence of the angular deviation of the main radiation lobe. This also restricts discontinuities along the spiral strands, thus avoiding impedance mismatches.

[0083] There figure 9 represents an example of a profile view of a set of circular sector elements of an absorbing half-lens in a set of embodiments of the invention.

[0084] There figure 9 represents more precisely a profile view of the circular sector elements (or sectors) 8a, 8b, 8c, 8d and 8e shown in figure 8 For each of the profiles, the figure 9 represents the thickness of the profile as a function of the distance from the center of the half-lens, the distance being shown increasing from left to right.

[0085] As in figure 8 It can be noted that, at a given distance from the center, the thickness decreases for sectors 8a, 8b, 8c, 8d, and 8e. Indeed, all sectors follow a similar profile pattern, in which: The thicknesses for sector 8a are defined by a function parameterized by four thicknesses s1, s2, s3 and s4; and the thicknesses for sectors 8b are defined by the same function, parameterized with the thicknesses 0.8 * s1, 0.8 * s2, 0.8 * s3 and 0.8 * s4; the thicknesses for sectors 8c are defined by the same function, parameterized with the thicknesses 0.6 * s1, 0.6 * s2, 0.6 * s3 and 0.6 * s4; the thicknesses for sectors 8d are defined by the same function, parameterized with the thicknesses 0.4 * s1, 0.4 * s2, 0.4 * s3 and 0.4 * s4; The thicknesses for sectors 8d are defined by the same function, parameterized with the thicknesses 0.2 * s1, 0.2 * s2, 0.2 * s3 and 0.2 * s4.

[0086] In a set of embodiments of the invention, each circular sector element is defined by a thickness function that increases and then decreases as a function of a distance to the center of the half-lens.

[0087] This is, for example, the case of circular sector elements represented in figure 9 , for which the thickness initially increases from the center of the lens (on the left of the figure 9 ) up to a distance ds3, then decreases between the distance ds3 and a distance ds4 representing the radius of the circular sector elements.

[0088] The distance ds3 can, for example, correspond substantially to the antenna radius. This allows for a half-lens thickness that increases with the distance from the antenna center, and therefore with the wavelength of the waves used locally by the antenna. This results in a significant thickness for low frequencies and a smaller thickness for high frequencies. This allows for a homogeneous beam deflection over a wide frequency band.

[0089] There figure 10 represents an example of an overview of an antenna system comprising a set of circular sector elements of an absorbing half-lens in a set of embodiments of the invention.

[0090] There figure 10 This represents an overview of a Sys10 antenna system comprising several of the elements discussed above. The Sys10 antenna system includes, in particular: a metallic cavity Cav; an antenna Ant in the metallic cavity; a half-lens comprising: ∘ an annular element Ann; ∘ a plurality of circular sector elements Sect.

[0091] Some elements of the Sys10 antenna system are not visible on the figure 10 For example, the basic element of the half-lens is located either in the plurality of circular sector elements, and the peripheral absorbing ring is located inside the walls of the metallic cavity.

[0092] There figure 11a represents an example of radiation patterns of a state-of-the-art antenna at different frequencies, without deflection of the antenna beam.

[0093] There figure 11b represents an example of radiation patterns of an antenna at different frequencies, with deflection of the antenna beam by an antenna system in a set of embodiments of the invention.

[0094] In general, the figures 11a à 18 correspond to 3D electromagnetic simulations performed on a model of an antenna system according to the invention. They are given by way of illustrative and non-limiting example only of the results obtained by an antenna system according to the invention; different results may be obtained in other embodiments of the invention (for example, with another type of antenna, or other dimensions).

[0095] Each of the 6 diagrams shown on the figures 11a And 11bcorresponds to a given frequency, from left to right and top to bottom, 3.5 GHz, 4.5 GHz, 5.5 GHz, 6.5 GHz, 7.5 GHz, and 8.5 GHz.

[0096] For each of the frequencies figure 11a represents the diagram without deviation, and the figure 11b The diagram with deviation. The deviation is represented by the roll angle φ and the site angle θ.

[0097] There figure 11b shows that the system according to the invention does allow a deviation of the radiation pattern of the antenna, and that this deviation is quite homogeneous over a wide frequency band, in this example from 3.5 GHz to 8.5 GHz.

[0098] There figure 12 represents two cross-sections of a 3D representation of the main lobe of the radiation pattern of an antenna deflected by an antenna system in a set of embodiments of the invention.

[0099] The two sections correspond to sections along the planes defined by the X and Y axes, and the X and Z axes respectively.

[0100] This example shows that the system according to the invention makes it possible to deflect the antenna beam, both according to the roll angle φ and the site angle θ.

[0101] There figure 13 represents an example of a deflection angle obtained by an antenna system as a function of frequency in a set of embodiments of the invention.

[0102] There figure 13 as well as the figures 14 à 18 , concern the same example as the figures 11a à 12 We observe on the figure 13 that the deviation angle of the main lobe of the antenna's radiation pattern is between 11° and 22°. The invention therefore makes it possible to obtain a relatively constant deviation angle over a wide frequency band.

[0103] There figure 14 represents an example of an angular deflection angle obtained by an antenna system as a function of frequency in a set of embodiments of the invention.

[0104] The angular deviation angle is between 340° and 25°, and can therefore be limited over the entire frequency band.

[0105] There figure 15 represents an example of antenna gain obtained by an antenna system as a function of frequency in a set of embodiments of the invention.

[0106] The antenna gain is represented on the vertical axis, in dB, as a function of frequency, on the horizontal axis, in GHz.

[0107] We observe that the radiated gain is typically greater than 2 dB, which shows that the half-lens allows us to obtain the angular deviation shown. Figure 13 without significant degradation of the radiated gain level. It is also observed that there is no gain dip depending on the frequency: this shows that the addition of the half-lens does not create any additional destructive interference with the lower ground plane of the antenna cavity.

[0108] There figure 16 represents an example of axial ratio obtained by an antenna system as a function of frequency in a set of embodiments of the invention.

[0109] The axial ratio is represented on the vertical axis, in dB, as a function of frequency, on the horizontal axis, in GHz.

[0110] We observe that the axial ratio is well below -3dB, which represents good polarization purity over a wide frequency band, in this case all the frequencies tested between 3.5 and 8.5 GHz.

[0111] There figure 17 represents an example of -3dB lobe width obtained by an antenna system as a function of frequency in a set of embodiments of the invention.

[0112] The lobe width is represented on the vertical axis, in dB, as a function of frequency, on the horizontal axis, in GHz.

[0113] We observe that the lobe width at -3 dB, in the presence of the half-lens, remains consistent with that expected for this type of antenna: the half-lens therefore creates an angular deviation of the main radiation lobe but does not alter the angular opening domain at half power in the radiation planes studied, with a rather stable angular opening in frequency.

[0114] There figure 18 represents an example of impedance matching obtained by an antenna system as a function of frequency in a set of embodiments of the invention;

[0115] The matching is represented on the vertical axis, in dB, as a function of frequency, on the horizontal axis, in GHz.

[0116] It is observed that the addition of the absorbing dielectric half-lens does not induce any mismatch in the antenna.

[0117] The examples above demonstrate the invention's ability to generate a homogeneous beam deflection from an antenna over a wide frequency band, while minimizing the size of the antenna system and preserving antenna performance. However, they are given only as examples and do not in any way limit the scope of the invention, as defined in the claims below.

Claims

1. Antenna system (Sys1a, Sys1b, Sys10) comprising: - a ground plane with a cavity (Cav) covered with a dielectric, magneto-dielectric or magnetic substrate (Subs), the cavity comprising an opening and walls; - an antenna (Ant) disposed on the dielectric, magneto-dielectric or magnetic substrate; - an absorbing peripheral ring (Cour) disposed between the antenna and the walls; - an absorbing hemilens (Lent1a, Lent1b) having a shape of an angular sector, comprising a base element (Bas) covering a first part of the opening of the cavity and a first part of the antenna, a second part of the opening of the cavity and a second part of the antenna not being covered by said base element.

2. Antenna system according to claim 1, wherein the absorbing hemilens comprises an annular element (Ann) forming an extension of the absorbing peripheral ring over the second part of the opening.

3. Antenna system according to claim 1, wherein the first part of the opening of the cavity corresponds to half of the opening of the cavity.

4. System according to claim 1, wherein the absorbing hemilens comprises at least one circular sector element (Sect), the thickness of which varies according to the distance to the centre of the hemilens.

5. System according to claim 4, wherein the absorbing hemilens comprises a plurality of circular sector elements, the thickness of which is defined by an increasing function of an angular distance from the edges of the lens.

6. System according to any one of claims 4 or 5, wherein each circular sector element is defined by an increasing then decreasing thickness function, according to a distance to the centre of the hemilens.

7. Antenna system according to any one of the preceding claims, wherein at least one element from among the absorbing peripheral ring, and the hemilens is made of a partially absorbing dielectric material.

8. Antenna system according to claim 7, wherein the dielectric material partially comprises carbon.

9. Antenna system according to any one of the preceding claims, wherein the antenna is a spiral antenna, a sinusoid antenna or a periodic antenna.

10. Antenna system according to claim 9, wherein the antenna is defined by an Archimedes spiral.

11. Antenna system according to any one of the preceding claims, wherein the antenna is a broadband antenna, making it possible to obtain a constant angle of deviation over the entire operating frequency band of the antenna.

12. Antenna system according to any one of the preceding claims comprising: - a first device comprising the ground plane, the antenna and the absorbing peripheral ring; - a second device comprising the absorbing hemilens.

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