Antenna system comprising an antenna and a passive device for angular deflection of a main radiation lobe of the antenna

Abstract

Antenna system comprising an antenna and a passive device for angular deflection of a main radiation lobe of the antenna. This antenna system (1) comprises an antenna (10) and a passive device for angular deflection of a main radiation lobe of the antenna, characterized in that the device is constituted by a lens (20), said lens having a constant thickness and having a progressive relative permittivity between an internal edge of the lens located on the side of the geometric center (C) of the antenna and an external edge of the lens located on the side of a periphery of the antenna, the profile of the relative permittivity as a function of the distance from the geometric center of the antenna being adapted so that the lens deflects the main radiation lobe of the antenna by a predefined deflection angle over at least a portion of an operating frequency band of the antenna. Figure for abstract: Figure 2

Description

Title of the invention: Antenna system comprising an antenna and a passive device for angular deflection of a main radiation lobe of the antenna.

[0001] The invention relates to the field of antenna systems capable of operating in transmission or reception, and more particularly to that of antenna systems equipped with a passive device for angular deviation of the main radiation lobe of at least one of the antennas of the antenna system.

[0002] It is sometimes necessary to associate with an antenna a device for angular deflection of its main lobe, to achieve electromagnetic decoupling between this antenna and a neighboring antenna of the antenna system, to achieve electromagnetic decoupling between this antenna and the supporting structure, or even to meet a need for local attenuation of the electric field in order to improve the electromagnetic compatibility between this antenna and a neighboring antenna (for example by masking a radiation domain which is not operationally useful).

[0003] Document FR073083 discloses an antenna system comprising an antenna and a passive device for angular deflection of the main radiation lobe of a spiral antenna.

[0004] According to this state of the art, the deflection device is a lens arranged above the radiating element of the antenna so as to cover an angular sector of the antenna. This lens is made of a partially absorbent dielectric material. It has a thickness which varies as a function of the distance from the geometric center of the radiating element, in order to obtain a substantially constant deflection angle over the operating frequency band of the antenna.

[0005] However, the frequency range over which the main lobe deflection angle is actually constant remains quite limited. Typically, this range extends between a minimum frequency FMIN and a maximum frequency FMAX such that the ratio FMAX to FMIN is approximately two, or one octave maximum.

[0006] This remains insufficient when the antenna is a wide frequency band antenna such as a spiral antenna and when the aim is to obtain constant behavior over the entire operating frequency band of this antenna and not just over a limited frequency range.

[0007] Furthermore, even if the deflection angle is relatively constant over this frequency range, a degradation of the purity of the polarization is observable.

[0008] But above all, the fact that the thickness of the lens varies and is, in certain places, relatively significant (in particular in the vicinity of the external edge of the lens which corresponds to the low frequencies of the operating frequency band) does not facilitate the integration of such a passive device into an antenna system, particularly if the latter includes a protective radome. Taking into account the operating frequencies considered (for example between 3 GHz and 6 GHz in document FR073083), the distance between the radiating element of the antenna and the lower face of the radome is typically 2 mm maximum.

[0009] The invention therefore aims to propose an improved passive device for angular deflection of the main lobe of a wide frequency band antenna.

[0010] For this purpose, the invention relates to an antenna system comprising an antenna and a passive device for angular deflection of a main radiation lobe of the antenna, characterized in that the device is constituted by a lens, said lens having a constant thickness and having a progressive relative permittivity between an internal edge of the lens located on the side of the geometric center of the antenna and an external edge of the lens located on the side of a periphery of the antenna, the profile of the relative permittivity as a function of the distance from the geometric center of the antenna being adapted so that the lens deflects the main radiation lobe of the antenna by a predefined deflection angle over at least a portion of an operating frequency band of the antenna.

[0011] According to particular embodiments, the antenna system comprises one or more of the following characteristics, taken in isolation or in all technically possible combinations: - the antenna being a wide frequency band antenna, said at least one portion of the frequency band extends between a minimum frequency and a maximum frequency, such that the ratio of the maximum frequency to the minimum frequency is greater than six, preferably still greater than nine. - said at least one portion of the frequency band extends between a minimum operating frequency of the antenna and a maximum operating frequency of the antenna. - the deflection angle is constant over said at least one portion of the operating frequency band of the antenna. - The antenna system also includes a radome, the radome protecting the antenna and the lens from external aggression. - the lens is fixed by a film of glue or by screwing, to the antenna or to a radome. - the antenna comprises a ground plane, a printed circuit carrying a radiating element and arranged above the ground plane, and a cavity between the ground plane and the printed circuit, the lens being arranged parallel to the radiating element, above the radiating element or below the element radiating, inside the cavity. - the antenna is a horn antenna, a spiral antenna, a logarithmic antenna, a log-periodic antenna, a meandering antenna or a Vivaldi antenna. - the lens also has a progressive relative permittivity according to a thickness of said lens and / or according to a polar angle of said lens evaluated in relation to an axis of symmetry of said lens. - the lens is inscribed in an angular sector. - the lens results from the assembly of a plurality of elementary sections, each elementary section being characterized by a constant relative permittivity value. - the lens is manufactured using an additive technique, a structure of the lens comprising a plurality of patterns. - a first dielectric material is used to make the patterns and a second dielectric material is used to fill recesses in the patterns, the second dielectric material being low loss or lossy. - a size of the patterns is adjusted so that the lens locally presents the desired relative permittivity.

[0012] The invention also relates to a passive device for angular deflection of the main lobe of an antenna adapted to be integrated into the preceding antenna system.

[0013] The invention and its advantages will be better understood on reading the detailed description which follows of two particular embodiments, given solely as illustrative and non-limiting examples, this description being made with reference to the appended drawings in which: - [Fig.l] [Fig.l] is a schematic representation, in section, of a first embodiment of an antenna system according to the invention comprising a single wide frequency band antenna of the sinuous type, and a lens; - [Fig.2] [Fig.2] is a perspective representation of the antenna system of [Fig.l]; - [Fig.3] [Fig.3] is a graph representing the theoretical evolution of the per relative mittivity of the lens of the antenna system of [Fig.l] as a function of the operating frequency of the antenna; - [Fig.4] [Fig.4] illustrates a possible structure for the lens of the an system ternary of [Fig.l], by association of elementary sections each having different relative permittivities; - [Fig.5] [Fig.5] represents different graphs illustrating, for different operating frequencies of the antenna of [Fig.l], the evolution of the gain for, on the one hand, an antenna system which is not equipped with the lens according to the invention and, on the other hand, an antenna system which is equipped with the lens according to the invention; and, - [Fig.6] [Fig.6] is a schematic representation, in perspective, of a second embodiment of an antenna system according to the invention comprising several wide frequency band antennas of the horn type, each antenna being equipped with a lens.

[0014] Figures 1 and 2 represent an antenna system 1 according to a preferred embodiment of the invention.

[0015] The antenna system 1 comprises a single wide frequency band antenna 10. The antenna 10 is for example a sinuous antenna (as shown in [Fig.2]).

[0016] Alternatively, another type of broadband planar antenna may be used, such as an Archimedean spiral, logarithmic, or log-periodic antenna. Alternatively, a narrowerband planar antenna may be used, such as a patch antenna.

[0017] The antenna 10 comprises a ground plane 12, a printed circuit 16, and a cavity 14, arranged between the ground plane 12 and the printed circuit 16.

[0018] The cavity 14 can advantageously be filled with a suitable substrate, in particular for the mechanical strength of the antenna 10.

[0019] The upper surface of the circuit 16 carries a radiating element. The metal strands constituting the radiating element are printed on an upper surface of the printed circuit 16.

[0020] The antenna 10 preferably forms a cylinder of radius Ro and axis Z. Alternatively, the antenna can also be square in shape, for example for a case of application to a square spiral antenna.

[0021] A reference trihedron is attached to the antenna system 1, such that its origin coincides with a geometric center C of the radiating element, the XY axes lie in the radiation plane defined by the upper surface of the printed circuit 16 and the Z axis is normal to this radiation plane (oriented towards the radiation half-space of the antenna).

[0022] The antenna system 1 comprises a lens 20 as a passive device for angular deflection of the main lobe of the antenna 10.

[0023] In the embodiment of Figure 1, the lens 20 is glued to the upper surface of the printed circuit 16. The glue film 30 constitutes a layer of constant thickness h2 and constant relative permittivity e2, greater than unity.

[0024] Alternatively, the lens 20 is positioned in direct contact with the radiating element, for example by screwing onto the printed circuit 16.

[0025] Advantageously, the antenna system 1 comprises a radome 40, intended to protect the antenna 10 and the lens 20 from external attacks. In [Fig.2], the radome has not been shown so as not to mask the lens 20. Preferably, the radome 40 has a thinned portion 42 so as to receive the upper part of the lens 20 and thus reduce the total thickness of the antenna system 1.

[0026] The lens 20 is designed and arranged relative to the antenna 10 so as to tilt, in the YZ plane of FIG. 1, the direction D of the main radiation lobe of the antenna 10 by an inclination angle Bq (evaluated relative to the Z axis).

[0027] Geometrically, the lens 20 forms an angular sector.

[0028] The lens 20 is positioned above the radiating element, in the near-field radiation zone of the radiating element. Alternatively, the lens is positioned below the radiating element, in the cavity 14.

[0029] The lens 20 is positioned so that its apex (constituting its internal edge) substantially coincides with the geometric center C of the radiating element and its external edge coincides with the periphery of the antenna 10.

[0030] The lens 20 is symmetrical with respect to its bisector.

[0031] It is positioned so that its bisector coincides with the Y axis.

[0032] The half-opening angle of the angular sector formed by the lens 20 is noted Yi.

[0033] The lens 20 has a constant thickness h]. The thickness lq of the lens 20 is low compared to the wavelength Xo associated with the minimum frequency FMIN (i.e. the maximum wavelength) of the operating frequency band of the antenna 10.

[0034] In order for the lens 20 to make it possible to obtain, at constant thickness, an angular deviation which varies little depending on the operating frequency of the antenna 10 (both in the near-field zone and in far-field radiation), the material constituting the lens has progressive dielectric properties as a function of the frequency.

[0035] The relative permittivity follows an evolution profile between an internal edge of the lens located on the side of the geometric center (C) of the antenna and an external edge of the lens located on the side of a periphery of the antenna.

[0036] Figure 3 represents three curves, respectively C1, C2 and C3, for three values ​​of the opening angles 2y of the lens 20, respectively 7.5°, 15° and 30°. Each curve gives the profile of the relative permittivity ei as a function of the frequency F in order to obtain, over the entire frequency band, an angular deviation of an inclination angle Bq equal to 10°.

[0037] For a wide frequency band antenna, sinuous or spiral (Archimedean, logarithmic, etc.), there is a direct relationship between the operating frequency and the distance r from the Z axis of the antenna. Indeed, for this type of antenna, the portion of the radiating element which radiates mainly at one frequency is a ring whose radius depends on the inverse of the frequency. Thus, in Figure 3, each curve gives also the value of the relative permittivity Ei as a function of the distance r.

[0038] Due to this relationship, the dielectric material constituting the lens 20 has a relative permittivity profile such that the value of this permittivity decreases progressively from the periphery of the antenna (corresponding to the low operating frequencies), towards the center C of the antenna (corresponding to the high operating frequencies).

[0039] The lens 20 is thus manufactured so as to present a dielectric gradient according to the distance r from the center C of the antenna.

[0040] In the cylindrical geometry of this first embodiment, polar coordinates are adapted. A point P is described by three coordinates: the distance r to the Z axis (or radius), between 0 and Rj; the thickness h relative to the lower surface of the lens, between 0 and hj; and a polar angle Y evaluated relative to the Y axis, between - / 2 and + Y] / 2.

[0041] Alternatively or in combination, the lens has a dielectric gradient along the Z direction, i.e. along the thickness h of the lens. This may prove advantageous in particular to avoid too large a jump in relative permittivity in the vicinity of the interfaces, the adhesive film and the printed circuit on the one hand and the radome on the other hand. Modifying the permittivity according to the thickness thus makes it possible to offer a degree of freedom to create a permittivity adaptation at the interfaces.

[0042] In another variant or in combination, the lens has a dielectric gradient along the polar angle Y. This can prove advantageous in particular to have a relative permittivity close to unity in the vicinity of the lateral edges of the lens and to ensure a certain continuity of this quantity.

[0043] In the following, a procedure is briefly presented for determining the profile of the relative permittivity as a function of the distance from the center of the antenna. This involves pre-sizing the lens taking into account theoretical analytical modeling, then electromagnetically simulating the behavior of the entire antenna system to finally refine the sizing.

[0044] It is possible to analytically formulate the angular deviation of the lobe as a function of several parameters. Such an analytical formulation makes it possible to write a relation of the following general form:

[0045] 8i)= f(F> yp h|- (Eq. 1)

[0046] According to equation 1, the angular deviation &o is a function f of the operating frequency F, of the angle a considered in the plane perpendicular to the deviation plane (for example, bearing angle, if the deviation is along the elevation plane), of the opening Yj of the angular sector formed by the lens, of the thickness L of the lens, of the thickness h2 of the glue layer, and the effective relative permittivity Eref.

[0047] The effective relative permittivity (complex or real) can be expressed via the equation:

[0048] P _ MdMj, (Eq. 2) ^reff Ej+e2

[0049] From equations 1 and 2, it is possible to obtain the following equation 3:

[0050] £i = y^ hh (Eq. 3)

[0051] where the quantity of interest is expressed as a function f' of the relevant parameters, in particular of the frequency F.

[0052] For the case of a wide frequency band antenna, a near field radiation ring of radius r can be expressed according to equation 4:

[0053] r = ^(Eq. 4)

[0054] where A is a constant and c is the speed of light.

[0055] Equation 4 reinjected into equation 3 makes it possible to obtain equation 5:

[0056] £[ - f"^ hb |)? (Eq 5)

[0057] where the quantity of interest £i is expressed as a function f” of the relevant parameters, in particular of the distance r to the Z axis of the antenna.

[0058] Those skilled in the art know possible forms for the analytical function f (and therefore the functions f' and f") determined from physical models and particular approximations.

[0059] Having an analytical expression makes it possible to evaluate the impact of the lens on the angular deviation of the main lobe, to estimate the theoretical deviation achievable for the relative permittivity of a given dielectric material, and to determine the relative permittivity profile necessary for a stable angular deviation as a function of frequency.

[0060] Other procedures could be implemented to pre-size the lens, such as for example the effective medium theory, presented for example in the work of Joseph W. Haus, “Fundamentals and Applications of Nanophotonics”, Woodhead Publishing, 2016, in particular its chapter 7, “Effective medium theories” by MA Vincenti and D. de Ceglia.

[0061] Following this theoretical pre-dimensioning of the electromagnetic structure of the lens, and since the analytical equations do not take into account the interaction between the lens and the antenna (nor between the lens and the possible radome), it is appropriate, in a second step, to simulate the operation of the antenna system in its entirety.

[0062] This simulation then makes it possible to electromagnetically optimize the various components of the antenna system, in particular the lens, with the aim of rigorously obtaining the desired angular deviation over the entire operating frequency band. antenna operation.

[0063] The dielectric material used to make the lens 20 preferably has a non-dispersive permittivity as a function of frequency (i.e. the real part and the imaginary part of the relative permittivity are invariant with respect to frequency).

[0064] More preferably, the material used has a non-complex relative permittivity.

[0065] The lens is for example made of a dielectric thermoplastic (PLA, ABS, PEEK, PEKK, etc.).

[0066] Advantageously, a material compatible with additive manufacturing, for example by 3D printing, is used. For example, the lens is produced by fused deposition modeling (FDM) or by selective laser sintering (SLS).

[0067] In this case, the progressiveness of the relative permittivity is obtained by varying the filling rate of the material at each point P of the lens 20. Knowing that the filling is achieved by the repetition of a plurality of patterns, the increase in the filling rate can consist of reducing the size of these patterns.

[0068] An advantageous way of manufacturing the lens then consists of providing a lens which results from the assembly of different sections, each section having a constant relative permittivity cl, but adjusted so that together the different sections make it possible to find the relative permittivity profile planned during dimensioning.

[0069] As is for example shown in [Fig.4], the lens 20 results from the assembly of five annular sections subdividing the angular sector formed by the assembled lens: a central section 21, three intermediate sections 22, 23 and 24 and a peripheral section 25.

[0070] The inner radius of section 21 is noted the inner radius of section 22 (which is equal to the outer radius of section 21) is noted R2, the inner radius of section 23 (which is equal to the outer radius of section 22) is noted R3, the inner radius of section 24 (which is equal to the outer radius of section 23) is noted R4, and the inner radius of section 25 (which is equal to the outer radius of section 24) is noted R5 (knowing that the outer radius of section 25 corresponds to the radius Ro of the antenna system).

[0071] The number of sections constituting the lens 20 can be multiplied according to the precision sought in the variation of the relative permittivity so as to best approximate the initially calculated profile.

[0072] Preferably, to vary the relative permittivity from one section to another, the filling rate is modified from one section to another. For example in [Fig.4], the rate filling ranges from 20% for the central section 21 to 80% for the peripheral section 25.

[0073] In the embodiment of [Fig.4], the modification of the filling is carried out by reducing the size of the patterns. In the embodiment of [Fig.4], these are hollow patterns, in this case triangles. Alternatively, other patterns are possible (gyroid, cross, grid, hexagon, zigzag, etc.).

[0074] The side wall of a section is advantageously reinforced so as to ensure mechanical strength (rigidity and resistance to humidity).

[0075] Alternatively or in combination, the material used for each section of the lens may be different from one section to another. For example, sections 21 and 22 may be made of ABS plastic, while sections 3, 4 and 5 may be made of PEEK plastic.

[0076] In another variant, the recesses inside the patterns, instead of being left empty (and having a relative permittivity equal to unity), are filled with a second dielectric material different from the first material used to make the patterns. This then involves implementing a manufacturing process by bi-material 3D printing.

[0077] This second material is preferably a low-loss dielectric material. Alternatively, a dielectric material (ABS, PEEK, PEKK, etc.) is used for the patterns and it is carbon-enriched (ABS ESD, PEEK ESD, PEKK ESD, etc.) for filling the patterns.

[0078] If it is desired to produce a lens having an orthoradial gradient of the relative permittivity (i.e. a progression of f'i according to the polar angle V), an annular section can be subdivided into several subsections, each subsection having a filling rate adapted to obtain the desired gradient.

[0079] In the same way, if one wishes to produce a lens having an axial gradient of the relative permittivity (i.e. a progression of according to the thickness h), a section can result from the superposition of several subsections, each subsection having a filling rate adapted to the value of the desired relative permittivity.

[0080] [Fig.5] represents two graphs showing the effectiveness of a lens according to the invention.

[0081] To obtain these results, an antenna system like that of figure 1 was manufactured so that the lens has an opening angle 2yj of 30° and a thickness hi equal to 2 mm, and that the glue film has a thickness h{ equal to 0.5 mm.

[0082] The graph on the left is obtained for a first frequency Fl of the antenna frequency band. For example Fl is worth twice FMIN. The graph on the right is obtained for a first frequency F2 of the antenna frequency band. For example F2 is six times FMIN.

[0083] Each graph illustrates, for a given frequency of the operating frequency band of the antenna of figure 1, the evolution of the gain (expressed in dBi) as a function of the angle 0 evaluated in the ZY plane relative to the Z axis (expressed in Deg).

[0084] On each graph, the behavior of an antenna system which is not equipped with the lens according to the invention is represented by the curve L1, the behavior of an antenna system equipped with the lens according to the invention is represented by the curve L2 for a deviation of 10° and L3 for a deviation of 20°.

[0085] These graphs show an angular deviation which is stable over a wide frequency range, such that the ratio between the maximum frequency FMAX and the minimum frequency FMIN is equal to approximately 9.

[0086] By stable, it is meant that the deflection angle remains constant over the entire frequency range considered with an accuracy of less than 15%, preferably even less than 10%. It should be emphasized that the equations mentioned above make it possible to define a dielectric gradient leading to a theoretical deflection angle which is strictly constant over the entire frequency range. It is indeed the practical implementation which introduces an inaccuracy (approximation of the dielectric gradient by a plurality of sectors of constant permittivity, coupling effect between the lens and the antenna or the radome).

[0087] Furthermore, it is shown that the polarization purity is preserved over this entire frequency band.

[0088] The principle of the lens according to the invention can in fact be applied to other wide frequency band antennas, such as horn antennas or Vivaldi antennas, that is to say even when the active zone of near field radiation at frequency F is not directly a function of the distance from the axis of the antenna. But structuring the lens in such a way as to have a progressive relative permittivity from one edge of the lens to the other makes it possible to tilt the direction of the main lobe.

[0089] [Fig.6] thus represents a second embodiment of an antenna system according to the invention.

[0090] The antenna system 101 comprises four horn antennas, 110_l, 110_2, 110_3 and 110_4, identical to each other.

[0091] The radiating end of each horn antenna is pyramidal in shape. Its radiating mouth is rectangular, but could alternatively adopt other shapes, in particular circular.

[0092] An XYZ reference frame is attached to the antenna system 101, so that its origin coincides for example with the center C of the radiating mouth of the second antenna 110_2.

[0093] The different horn antennas are arranged edge to edge, to form a row along the X axis, so that their mouths lie in the common XY plane.

[0094] Each horn antenna is provided with a lens. A lens 120_l, 120_2, 120_3 or 120_4 masks a portion of the mouth of the antenna 110_l, 110_2, 110_3 or 110_4 which it equips.

[0095] A lens, for example the lens 120_2, forms an angular sector which covers a lower fraction of the mouth of the antenna 110_2. This angular sector extends from the geometric center C of the radiating mouth of the antenna, to a lower edge 118_2 of the radiating mouth of the antenna.

[0096] A lens has the function of deflecting the axis D of the lobe of the antenna with which it is fitted by an angle Oq relative to the direction normal to the plane of the mouth, i.e. the axis Z. In the embodiment of [Fig.6], the angular deviation of the main lobe in the presence of the lens is similar for the different antennas of the system 101.

[0097] The lens 120_2 has a constant thickness and exhibits a gradient in its relative permittivity.

[0098] In the embodiment of [Fig.6], the gradient is oriented along the Y axis. In this figure, relative iso-permittivity lines have been shown in dotted lines. They are arranged parallel to the lower edge 118_2.

[0099] For example, for X-band operation, the lens has a thickness of one millimeter. It is, for example, made of ESD ABS.

[0100] For dimensioning, it is appropriate, for example, to define the characteristics of the lens allowing a deviation of a predefined deviation angle 0q for an intermediate frequency of the operating frequency band of the antenna.

[0101] Then, for a frequency close to the maximum frequency FMAX, to modify the relative permittivity of a part of the lens, for example close to the geometric center C of the radiating plane of the antenna. Similarly, for a frequency close to the minimum frequency FMIN, to modify the relative permittivity of the other part of the lens, for example close to the peripheral edge of the radiating plane of the antenna.

[0102] A horn antenna is not necessarily wide frequency band and may have a typical operating frequency band such that FMAX / FMIN is close to two.

[0103] Numerous variant embodiments are possible.

[0104] The lens material may be a lossy (complex permittivity) or lossless (real permittivity) dielectric material.

[0105] The dielectric material used to make the lens may have a relative permittivity that is dispersive as a function of frequency (i.e., the real part and / or the imaginary part depend on the frequency). In this case, it may not be necessary to vary the filling rate or the charge of the base material to find an evolution of the relative permittivity similar to that represented in [Fig.3].

[0106] Alternatively, lossy and lossless dielectric materials are combined.

[0107] It is also possible to locally add a magnetodielectric material, the magnetic part of the material allowing an improvement in compactness depending on the thickness.

[0108] More generally, different parameters of the lens can be used as degrees of freedom to adapt the response of the antenna system to the stability needs of the angular deviation of the main lobe: variation of the filling rate of the material, use of a material of relative permittivity varying as a function of the frequency, local addition of dielectric losses, etc.

[0109] The lens does not necessarily cover the entire radiating element in the radial direction, i.e. between the center of the radiating element and its periphery. It may in fact be split into several rings spaced apart from each other. This makes it possible to generate an angular deviation of the main lobe for one or more portions of the frequency band associated with the antenna used.

[0110] Several lenses could be associated with the same antenna, in particular a lens placed above and a lens placed below the radiating element, these two lenses preferably being directly above each other. This provides an additional degree of freedom to adjust the deflection angle so that it is substantially constant over the entire operating range.

[0111] In the case of using a protective radome, the lens can be positioned under the radome. Instead of being fixed to the radiating element, the lens can then be fixed on the underside of the radome. For example, by means of a film of glue. Alternatively, the lens is part of the radome. That is to say, during the manufacture of the radome, a portion of the latter is shaped so as to play the role of a lens. The 3D printing techniques considered previously make it possible to produce such a radome.

[0112] The lens according to the invention is compatible with existing antenna manufacturing technologies. The addition of a lens does not require any modification of the antenna, either in its design or in its structure. Consequently, the lens constitutes a simple addition or insert to these antenna systems in order to deflect their main lobe.

[0113] The proposed solution has a relatively low cost, since it is compatible with additive manufacturing technology. This offers high reproducibility from one lens to another.

[0114] But above all the lens according to the invention has a particularly low thickness (at most a few millimeters) compatible with integration constraints, in particular the distance between the radiating plane and the protective radome.

[0115] The proposed solution is purely passive.

Claims

Claims

1. Antenna system (1) comprising an antenna (10) and a passive device for angular deflection of a main radiation lobe of the antenna, a reference trihedron being attached to the antenna system (1), the XY axes lying in a radiation plane of the antenna and the Z axis being normal to the radiation plane, an origin of the trihedron coinciding with a geometric center (C) of the radiating plane of the antenna, characterized in that the device is constituted by a lens (20), said lens having a constant thickness (hl) and having a progressive relative permittivity between an internal edge of the lens located on the side of the geometric center (C) of the antenna and an external edge of the lens located on the side of a periphery of the antenna,the profile of the relative permittivity as a function of the distance from the geometric center of the antenna being adapted so that the lens deflects the main radiation lobe of the antenna by a predefined deflection angle over at least a portion of an operating frequency band of the antenna.,

2. An antenna system according to claim 1, wherein, the antenna being a wide frequency band antenna, said at least one portion of the frequency band extends between a minimum frequency and a maximum frequency, such that the ratio of the maximum frequency to the minimum frequency is greater than six, more preferably greater than nine.

3. An antenna system according to any preceding claim, wherein said at least a portion of the frequency band extends between a minimum operating frequency of the antenna and a maximum operating frequency of the antenna.

4. An antenna system according to any preceding claim, wherein the deflection angle is constant over said at least one portion of the operating frequency band of the antenna.

5. An antenna system according to any preceding claim, further comprising a radome, the radome protecting the antenna and the lens from external aggression.

6. An antenna system according to any preceding claim, wherein the lens is fixed by a film of glue or by screwing, to the antenna or to a radome.

7. An antenna system according to any preceding claim, wherein the antenna comprises a ground plane, a printed circuit carrying a radiating element and disposed above the ground plane, and a cavity between the ground plane and the printed circuit, the lens being disposed parallel to the radiating element, above the radiating element or below the radiating element, inside the cavity.

8. An antenna system according to any preceding claim, wherein the antenna is a spiral antenna, a logarithmic antenna, a log-periodic antenna, a meandering antenna or a Vivaldi antenna.

9. An antenna system according to any one of claims 1 to 6, wherein the antenna is a horn antenna.

10. Antenna system according to any one of the preceding claims, in which the lens further has a progressive relative permittivity according to a thickness of said lens and / or according to a polar angle of said lens evaluated with respect to an axis of symmetry of said lens.

11. An antenna system according to any preceding claim, wherein the lens is inscribed in an angular sector.

12. Antenna system according to any one of the preceding claims, in which the lens results from the assembly of a plurality of elementary sections, each elementary section being characterized by a constant relative permittivity value.

13. An antenna system according to any preceding claim, wherein the lens is manufactured using an additive technique, a structure of the lens comprising a plurality of patterns.

14. The antenna system of claim 13, wherein a first dielectric material is used to form the patterns and a second dielectric material is used to fill recesses in the patterns, the second dielectric material being low loss or lossy.

15. An antenna system according to claim 13 or claim 14, wherein a size of the patterns is adjusted so that the lens locally has the desired relative permittivity.

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