EP3417507A1

EP3417507A1 - Electromagnetically reflective plate with a metamaterial structure and miniature antenna device including such a plate

Info

Publication number: EP3417507A1
Application number: EP17708866.3A
Authority: EP
Inventors: Nebil KRISTOU; Jean-François PINTOS
Original assignee: Commissariat a lEnergie Atomique CEA; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2016-02-17
Filing date: 2017-02-16
Publication date: 2018-12-26
Anticipated expiration: 2037-02-16
Also published as: US10826188B2; EP3417507B1; FR3047845A1; US20190044244A1; WO2017140987A1; FR3047846A1; FR3047846B1

Abstract

This electromagnetically reflective plate (10) for a miniature antenna device includes: etched conductive elements (20, 22, 24, 26) on a first dielectric substrate layer (30); an apertured ground plane (32) placed between the first substrate layer (30) and a second dielectric substrate layer (38); a set of metal through-vias (42) formed in the thickness of the two substrate layers (30, 38), each having an upper end making contact with one of the conductive elements (20, 22, 24, 26), a lower end reaching a lower face (44) of the second substrate layer (38), and passing through the ground plane (32) without electrical contact in one of its apertures (40). Each conductive element (20, 22, 24, 26) makes contact with a plurality of vias (42) and each via of each conductive element is connectable to another via of a neighbouring conductive element using a corresponding electrical connection (46) making contact with the lower end of this via. At least some of the electrical connections (46) comprise one or more meanders.

Description

The present invention relates to an electromagnetic reflection plate with a metamaterial structure for a miniature antenna device. It also relates to a miniature antenna device comprising such an electromagnetic reflection plate and an antenna disposed at a short distance from this plate.

It fits in a general way in applications for telecommunications systems or communicating objects in which radio frequency devices, including antennas and electronic circuits, are present and must be as compact as possible. In particular, the use of antennas in communication systems for aeronautics, surveillance or satellite navigation is unavoidable. However, in this type of device, space is reduced and creates a need for miniaturization of the antennas. An antenna is generally placed in front of a reflective plane to have a unidirectional radiation and allow the integration of an electronic circuit in the vicinity behind the reflective plane without sensitive interference. The radiation is thus directed in a direction of interest, allowing on the one hand to improve the gain of the antenna and on the other hand to reduce the sensitivity of the antenna in a half-space.

According to a first possible embodiment of the reflector plane, the latter is of a type approaching the perfect electrical conductor model with reflection of the electromagnetic field in phase opposition. The antenna must then be arranged at a distance from the reflective plane as close as possible to one quarter of its mean operating wavelength to compensate for phase opposition in reflection and to obtain a constructive interference between an incident wave originating directly from the antenna and a wave reflected by the reflective plane. At the metric and HF wavelengths, this technology has the disadvantage of being bulky. For example, for an average operating frequency f ₀ = 00 MHz of the antenna, it should be placed 75 cm from the reflector plane and for f ₀ = 1 GHz this still represents a distance of 7.5 cm.

According to a second possible embodiment of the reflector plane, the latter is of the magnetic magnetic conductive type approaching the perfect magnetic conductor model with reflection of the electromagnetic field without phase shift. The antenna can then be arranged very close to the reflector plane, in particular well below one quarter of its average operating wavelength, or even below one-tenth of this wavelength. This considerably reduces the size of the antenna device and allows its advantageous integration into the design of miniature antennas. A reflective plane according to this technology can be achieved using an electromagnetic reflection plate with a metamaterial structure which is the subject of the present invention. A method was also proposed in 1999 in Sievenpiper's thesis entitled "High-impedance electromagnetic surfaces", PhD of the University of California, Los Angeles (USA), to characterize artificial magnetic conductors by a method called of the phase diagram. This method consists in illuminating the surface to be characterized using a plane wave and at a normal incidence. The phase difference between the incident wave and the reflected wave is then compared. The interferences are considered as constructive when the phase difference is between -ττ / 2 and + ττ / 2, which thus defines the bandwidth of use of the artificial magnetic conductor.

According to this second artificial magnetic conductor technology, the present invention therefore relates more specifically to an electromagnetic reflection plate with a metamaterial structure for a miniature antenna device, comprising:

a plurality of conductive elements separated from each other and etched on an upper face of a dielectric substrate layer,

a ground plane disposed on the lower face of this layer of dielectric substrate, and

a set of through metal vias formed in the thickness of the substrate, each having an upper end in contact with one of the conductive elements.

However, the miniaturization of such an electromagnetic reflection plate is limited by the minimum number of conductive elements necessary to obtain a metamaterial structure, often organized into a matrix of at least four rows and four columns. Indeed, each of these resonant conductive elements is generally of dimensions close to one quarter of the average operating wavelength of the antenna. As a result, a metamaterial structure very rapidly imposes a large reflecting surface facing the antenna to ensure its operation in the frequency band of interest of the antenna. Various solutions have been made to improve the miniaturization of metamaterial structures, in particular by playing on the geometry of conductive elements (interdigitated capacitors, spiral inductors, etc.), on a multiplication of layers coupled in capacitors or by the use of discrete electronic components. liabilities or assets. But all these solutions have disadvantages of costs, significant reduction of the bandwidth of the antenna or bulk in thickness.

In a use of the metamaterial structures different from that envisaged in the present invention, that of electromagnetic band gap inter-antenna filter components known as EBG (Electromagnetic Band-Gap), innovative approaches have been proposed.

For example, in the patent application US 2014/0354502 A1, it is proposed a ground plane pierced with holes through which pass the metal vias, the latter not being in contact with the ground plane but connected to each other two by two using dedicated electrical connections located on the other side of the ground plane relative to the conductive elements.

For example also, in the US patent application 2009/0236141 A1, it is proposed in Figure 8 a metamaterial structure for EBG filtering comprising:

a plurality of conductive elements separated from each other and etched on an upper face of a first layer of dielectric substrate,

a ground plane disposed between a lower face of the first dielectric substrate layer and an upper face of a second dielectric substrate layer, with holes formed in this ground plane,

a set of through metal vias formed in the thickness of the first and second substrate layers, each having an upper end in contact with one of the conductive elements, a lower end reaching a lower face of the second dielectric substrate layer, and crossing the ground plane without electrical contact through one of its holes,

in which :

each conducting element is in contact with several metal vias, and

each metal wire of each conductive element can be connected to another metallic wire of a neighboring conductive element, with the aid of a corresponding electrical connection in contact with the lower end of this via metal.

But in these last two documents, the reflective properties of the structure obtained are not observed, only the decoupling between neighboring antennas and parasitic signal filtering being studied. In addition, such a structure does not appear to be sufficient to obtain additional miniaturization in the case of an application of electromagnetic reflection.

It may thus be desired to design an electromagnetic reflection plate with a metamaterial structure for a miniature antenna device that allows additional miniaturization while avoiding at least some of the aforementioned problems and constraints.

It is therefore proposed an electromagnetic reflection plate with a metamaterial structure for a miniature antenna comprising:

in which :

each conducting element is in contact with several metal vias, and

each metal via of each conductive element can be connected to another metal via a neighboring conductive element, by means of a corresponding electrical connection in contact with the lower end of this metal via,

and wherein, in addition, at least a portion of the electrical connections have at least one meander.

Thanks to the invention, it is possible to increase the phase difference between interconnected metal vias without increasing the size of the conductive elements of the metamaterial structure by cleverly exploiting, with the aid of one or more meanders on at least a portion of the electrical connections between vias, the surface located under the ground plane. Surprisingly, it has been observed that while multiplying the number of metal vias per conductive element does not in itself reduce the overall size of an electromagnetic reflection plate, the fact of doing so in combination with a phase shift increase using one or more meander connections (s) allows such a size reduction.

Optionally, each electrical connection connection of a metal via to another is etched on the underside of the second layer of dielectric substrate. Thus, the layout of the meanders is optimal.

Also optionally, each of said electrical connections has several meanders.

Optionally also:

the conducting elements are distributed in a matrix on the upper face of the first layer of dielectric substrate, and

each conducting element is in contact with four metal vias, each of these four metal vias being connectable to another metallic via of an adjacent conductive element in line or in a column in the matrix.

This option is advantageous in the case where it is desired to obtain axial symmetry along two orthogonal axes.

Optionally also, the metal vias of each conductive element and their respective electrical connections are distributed in a central symmetry around a central axis of symmetry of this conductive element.

Optionally also, at least a portion of the meander electrical connections etched on the underside of the second dielectric substrate layer is further provided with adjustable phase shifters.

Also optionally, each electrical meander connection engraved on the underside of the second dielectric substrate layer progressively widens from its end in contact with the corresponding metallic via to one of the edges of the conductive element under which it is engraved.

Also optionally, each of the conductive elements has one of the shapes of the assembly consisting of a square shape, a shape rectangular, of a spiral shape, a fork shape, a form of crutches cross and a dual form of cross crutches called UC-EBG form.

Also optionally, the conductive elements are periodically distributed on the upper face of the first dielectric substrate layer.

It is also proposed a miniature antenna device comprising:

an electromagnetic reflection plate according to the invention, and

an antenna having an average operating wavelength and disposed at a distance from the reflection plate less than one-tenth of this average operating wavelength.

The invention will be better understood with the aid of the description which follows, given solely by way of example and with reference to the appended drawings in which:

FIG. 1 shows in transparent perspective the general structure of an electromagnetic reflection plate portion with a metamaterial structure for a miniature antenna device, according to one embodiment of the invention;

FIG. 2A represents, according to the same transparent perspective, an elementary cell of the plate portion of FIG. 1,

FIGS. 2B, 2C and 2D are respectively front, top and bottom views of the elementary cell of FIG. 2A,

FIGS. 3A and 3B illustrate, in top and bottom views, an exemplary embodiment of a miniature antenna device comprising an electromagnetic reflection plate with a metamaterial structure, according to one embodiment of the invention,

FIG. 4 is a diagram illustrating a relation between the operating frequency of an antenna device such as that of FIGS. 3A, 3B and certain configuration parameters specific to the invention, and

FIG. 5 is a comparative diagram of reflection coefficient phases as a function of operating frequencies for a device according to the invention and a device of the state of the art.

The electromagnetic reflection plate portion 10 with a metamaterial structure shown schematically in transparent perspective in FIG. 1 can be considered as composed of several elementary cells repeating in two principal directions x and y. In the example of this figure, by For the sake of simplicity, only four elementary cells 12, 14, 16 and 18 are illustrated, one of which, for example the cell 12, is shown alone in FIG. 2A.

According to an overall description in layers in a direction z perpendicular to the x and y directions of the plate portion 10, several conductive elements 20, 22, 24, 26 separated from each other are etched on an upper face 28 of a first layer 30 of dielectric substrate. These conductive elements are for example rectangular or square but could be of any shape already studied in the state of the art. In particular, they could be in the form of a spiral, a fork, a cross on crutches or a dual cross with so-called UC-EBG crutches. In particular also, they could have inter-digitized capacitances or spiral inductors, known to allow a certain miniaturization of the reflector plate as specified above. They are also for example distributed in matrix by periodic repetition of their shape along the x and y directions on the upper face 28 of the first layer 30 of dielectric substrate. As a variant, the conductive elements could be of different shapes for a non-uniform distribution on the upper face 28, for example of increasing surfaces when moving away from a center, or any other topology that is relevant to those skilled in the art. depending on the application context.

The plate portion 10 further comprises a ground plane 32 disposed between a lower face 34 of the first dielectric substrate layer 30 and an upper face 36 of a second dielectric substrate layer 38, with holes 40 formed in this plane. of mass 32.

Furthermore, through metal vias 42 are formed in the thickness of the first and second substrate layers 30, 38, each having an upper end in contact with one of the conductive elements 20, 22, 24, 26, and one end. lower reaching a lower face 44 of the second layer 38 of dielectric substrate. Each of these vias 42 passes through the ground plane 32 without electrical contact through one of the holes 40.

More specifically, in the non-limiting example of FIG. 1, each conductive element 20, 22, 24 or 26 is in electrical contact with four vias 42. In addition, according to the invention, each via 42 of each conductive element 20 , 22, 24 or 26 is connectable to another via a neighboring conductive element, by means of a corresponding electrical connection 46 etched on the lower face 44 of the second layer 38 of dielectric substrate and in contact with the lower end of this via 42. In accordance with the invention also, so as to increase the phase shift between any two vias interconnected by their lower ends, at least a portion of the electrical connections 46 etched on the lower face 44 of the second layer 38 of dielectric substrate has one or more meanders to optimize the occupation of this lower face 44. the non-limiting example of Figure 1, each of these electrical connections 46 is meandering.

The elementary cell 12, shown only in transparent perspective in FIG. 2A and in front views, top and bottom in FIGS. 2B, 2C and 2D, is formed of the conductive element 20 and the entire thickness of the substrate situated in below in the z direction. It is for example square with sides of length P. The conductive element 20 is also square with sides of length W slightly smaller than P so that two conductive elements of two adjacent elementary cells do not touch each other.

Four vias 42 are in contact with the conductive element 20 at their upper ends. They are specifically referenced 42 (12) _a , 42 (12) _b , 42 (12) _c and 42 (12) _d in FIGS. 2A to 2D. They are off-center with respect to the center of symmetry of the conductive element 20 but remain on its axis of symmetries. More specifically, the two vias 42 (12) _a and 42 (12) _d are on the axis of symmetry x direction of the conductive element 20 but off-center with respect to its center of symmetry. More precisely also, the two vias 42 (12) _b and 42 (12) _c are on the axis of direction symmetry y of the conductive element 20 but off-center with respect to its center of symmetry. We note the common distance between each via and the corresponding edge closest to the elementary cell 12.

Four meander electrical connections 46 are etched on the lower face 44 of the second layer 38 of dielectric substrate in the elementary cell 12. They are specifically referenced 46 (12) _a , 46 (12) _b , 46 (12) _c and 46 (12) _d in FIGS. 2A-2D and correspond respectively to the vias 42 (12) _a , 42 (12) _b , 42 (12) _c and 42 (12) _d being in respective contacts with their lower ends. The meandering electrical connection 46 (12) _has four meanders clearly visible in FIG. 2D and gradually widens from its end in contact with the corresponding metallic via 42 (12) _a to one of the edges of the elementary cell 12 It thus has a length much greater than the distance between the via 42 (12) _a of this edge and allows its electrical connection with another via a conductive element (not shown in Figure 1) adjacent in the negative direction. from the direction x. The meandering electrical connection 46 (12) _b has four meanders clearly visible in Figure 2D and gradually widens from its end in contact with the corresponding metal via 42 (12) _b to another edge of the elementary cell 12. It thus has a length much greater than the distance that separates the via 42 (12) _b from this edge and allows its electrical connection with another via a conductive element (not shown in Figure 1) adjacent in the negative direction of the y direction. The meandering electrical connection 46 (12) _c has four clearly visible meanders in FIG. 2D and gradually widens from its end in contact with the corresponding metallic via 42 (12) _c to another of the edges of the elementary cell 12. It thus has a length much greater than the distance separating the via 42 (12) _c from this edge and allows its electrical connection with another via the adjacent conductive element in the positive direction of the direction y, that is, ie the via 42 (14) _b of the elementary cell 14. Finally, the meandering electrical connection 46 (12) _d comprises four meanders clearly visible in FIG. 2D and progressively widens from its end in contact with the via corresponding metal 42 (12) _d to another of the edges of the elementary cell 12. It thus has a length much greater than the distance between the via 42 (12) _d of this edge and allows its electrical connection with another vi a of the adjacent conductive element in the positive direction of the x direction, i.e. the via 42 (16) _a of the elementary cell 16.

It will be noted that the four vias 42 (12) _a , 42 (12) _b , 42 (12) _c and 42 (12) _d of the conductive element 20 and their respective meandering electrical connections 46 (12) _a , 46 ( 12) _b , 46 (12) _c and 46 (12) _d are distributed in a central symmetry around the center of symmetry of this conductive element 20. In addition, the surface of the lower face 44 of the second layer 38 of dielectric substrate is largely occupied by the respective meandering electrical connections 46 (12) _a , 46 (12) _b , 46 (12) _c and 46 (12) _d between the vias 42 (12) _a , 42 (12) _b , 42 ( 12) _c , 42 (12) _d and the four edges of the elementary cell 12.

Such a metamaterial structure described with reference to FIGS. 1, 2A, 2B, 2C and 2D is advantageously usable for the design of a miniature antenna device such as that represented in views from above and below in FIGS. 3A and 3B.

This device comprises a reflector plate 50 with a metamaterial structure composed of 25 elementary cells such as that illustrated in FIG. 2A distributed in a matrix of 5 rows and 5 columns. It further comprises a dipole antenna 52, visible in plan view in FIG. 3A, arranged at a distance from the plate 50. More precisely, if this dipole antenna 52 has an average operating wavelength λ noted, it can be disposed at a distance from the reflector plate 50 less than one tenth of the average operating wavelength, or even at a distance close to λ / 20, since the reflecting plate 50 can behave as an artificial magnetic conductor when it is sized to reflect waves with a zero phase shift at the average operating frequency of the antenna.

FIG. 3B illustrates a view from below of the vias interconnection network using the meander connections described above. It is shown that for a dipole antenna 52 having a length of 149 mm and a width of 3.5 mm disposed at a distance λ / 20 from the reflecting plate 50, an antenna device of total dimensions 0.63.λ x 0.63 is obtained. .λ x 0.071 .λ, where 0.071 .λ is the thickness, i.e. a low profile antenna device since its total thickness is less than λ / 10.

In an alternative embodiment, at least a portion of the meander connections engraved on the lower face 44 may be provided with adjustable phase shifters well known to those skilled in the art, for example diodes, for the interconnection of the conductive elements between them. This makes it possible to adjust the phase shifts according to the application to be optimized by simply varying the behavior of the active or passive elements employed while preserving the metamaterial structure 10 or 50 and without having to modify the length of the meander connections.

According to the invention and as illustrated in FIG. 4, a miniaturization of the elementary cells can be obtained by optimally adjusting the position of the four vias of each elementary cell and the phase shift Δφ between interconnected vias, this phase shift Δφ being regulated by the length of meander connections. Let k be the parameter equal to P / d. This parameter k is necessarily strictly greater than 2 to be able to have four eccentric vias. At the limit, the presence of a single via centered gives k = 2. The three curves of Figure 4 are: the solid curve for k = 2, the long dashed curve for k = 3 and the curve in short broken lines for k = 4. It is noted by the experiment that the vias are thus centered far from the edges of the elementary cell 12, k decreasing towards 2, plus the operating frequency with zero phase reflection, denoted F , decreases. But the operating frequency is inversely proportional to the antenna size. So at given operating frequency and antenna size, a reconciliation of the vias towards the center induces a miniaturization of the elementary cells. It is also noted by experimentation that, in this configuration of multi-pass elementary cells, the greater the phase shifts Δφ and hence the lengths of meander connections, the more the operating frequency with zero phase reflection decreases, which also induces a miniaturization of elementary cells. But we also note that the more the vias are close to the center, the less the effect of phase shifts Δφ on the operating frequency is important. At the limit, for k = 2, there is no effect of the increase of the phase shifts Δφ on the operating frequency as shown by the horizontal line in solid line of the diagram of FIG. 4. There is therefore a compromise to be found between the distance d of the vias with respect to the edges of each elementary cell and the implementable Δφ phase shifts that are directly related to the possible size of the meander connections on the lower face 44 of the second layer 38 of dielectric substrate. This search for the optimal compromise depends on the intended application and is within the reach of those skilled in the art.

The results of FIG. 4 were obtained by varying the parameters k and Δφ using simulations established on the basis of the miniature antenna device of FIGS. 3A and 3B with the following parameters:

- P = 53 mm,

- W = 51 mm,

thickness of the first layer of dielectric substrate = 5 mm,

thickness of the second layer 38 of dielectric substrate = 1, 6 mm,

relative permittivity of the dielectric substrate = 4.4,

- dielectric losses = 0.02.

FIG. 5 is a comparative diagram of reflection phase phases as a function of operating frequencies for a miniature antenna device according to the invention (in solid lines) and a miniature antenna device of the prior art of FIG. same dimensions (in short broken lines). The device of the state of the art chosen has a reflective plate of the mushroom type, that is to say with square conducting elements connected to a solid ground plane using a single via each (without second layer of substrate).

More precisely, for this comparison the following parameters have been imposed:

- P = 42 mm,

- W = 40 mm, thickness of the first layer of dielectric substrate = 5 mm,

thickness of the second layer 38 of dielectric substrate = 1, 6 mm (for the device according to the invention only),

relative permittivity of the dielectric substrate = 4.4,

- dielectric losses = 0.02,

- radius of the vias = 0.5 mm,

- k = 4 (for the device according to the invention only),

- Δφ = 186 ° (for the device according to the invention only).

The curves of Figure 5 were obtained by 3D electromagnetic simulation. While the dashed curve obtained with the miniature antenna device of the state of the art has a zero phase shift around 1.35 GHz, the solid line obtained with the miniature antenna device according to the invention. not only has a zero phase shift slightly below 1.35 GHz but also a 940 MHz inflection point. However, experience shows that the presence of this point of inflection makes it possible to use the reflecting plate of the miniature antenna device according to the invention as an artificial magnetic conductor at 940 MHz instead of 1.35 GHz. To use a mushroom type reflector plate device as an artificial magnetic conductor at 940 MHz, P = 64 mm would be required to have a zero phase shift around 940 MHz.

A gain in miniaturization of about 35% per dimension is thus demonstrated, which makes a gain of more than 57% in surface area. Or comparisons on other properties such as antenna matching and radiation efficiency at a chosen operating frequency, or directivity, show that miniature antenna devices according to the invention and with a mushroom reflector plate present performance quite comparable in terms of improvement over reflective plane devices of the type approaching the perfect electrical conductor model. The gain in miniaturization is therefore all the more appreciable.

It clearly appears that an electromagnetic reflection plate with a metamaterial structure such as that described above makes it possible to miniaturize an antenna device that includes it without, however, presenting any cost disadvantages or a substantial reduction in the bandwidth of the antenna. or substantial bulk in thickness. Only the available surface under the ground plane is exploited to obtain the advantageous technical effects resulting from meandering connections. Note also that the invention is not limited to the embodiments described above.

In particular, although a dipole antenna miniature antenna device has been detailed above, the invention is applicable to an antenna device whose antenna is ZOR (Zeroth-Order Resonator). ), wire-plate, broadband, circular polarization or other, arranged parallel or perpendicular to the reflective plane.

Alternatively also, each conductive element of the metamaterial may be in electrical contact with a number of vias different from four: for example two, six, etc. The vias are not necessarily all identical.

In a variant also, the invention also applies to a reflective plate with a metamaterial structure, the conductive elements of which are distributed over several layers that are shifted or not.

Alternatively also, the electrical connections between vias may not all be identical. In particular, it is possible to vary the values of k and Δφ from one elementary cell to another.

Alternatively also, the electrical connections between vias can be etched on several layers, not only on the underside of the second layer of dielectric substrate.

Alternatively also, each conductive element of the metamaterial may be in electrical contact with vias and / or corresponding electrical connections which are not distributed in a central and / or axial symmetry with respect to the center and / or to one or more axes of symmetry of the conductive element.

It will be apparent more generally to those skilled in the art that various modifications may be made to the embodiments described above, in light of the teaching just disclosed. In the following claims, the terms used are not to be construed as limiting the claims to the embodiments set forth in this specification, but should be interpreted to include all the equivalents that the claims are intended to cover because of their formulation and whose prediction is within the reach of those skilled in the art by applying his general knowledge to the implementation of the teaching that has just been disclosed to him.

Claims

1. An electromagnetic reflection plate (10; 50) having a metamaterial structure for a miniature antenna device comprising:

a plurality of conductive elements (20, 22, 24, 26) separated from each other and etched on an upper face (28) of a first dielectric substrate layer (30),

a ground plane (32) disposed between a bottom face (34) of the first dielectric substrate layer (30) and a top face (36) of a second dielectric substrate layer (38) with holes (40) arranged in this ground plane (32),

a set of through metal vias (42) formed in the thickness of the first (30) and second (38) substrate layers, each having an upper end in contact with one of the conductive elements (20, 22, 24, 26 ), a lower end reaching a lower face (44) of the second layer (38) of dielectric substrate, and passing through the ground plane (32) without electrical contact through one of its holes (40),

in which :

each conductive element (20, 22, 24, 26) is in contact with a plurality of metal vias (42; 42 (12) _a , 42 (12) _b , 42 (12) _c , 42 (12) _d ), and - each via metal (42; 42 (12) _a , 42 (12) _b , 42 (12) _c , 42 (12) _d ) of each conductive element is connectable to another metal via a neighboring conductive element, to by means of a corresponding electrical connection (46; 46 (12) _a , 46 (12) _b , 46 (12) _c , 46 (12) _d ) in contact with the lower end of this metallic via,

characterized in that at least a portion of said electrical connections (46; 46 (12) _a> 46 (12) _b> 46 (12) _c , 46 (12) _d ) have at least one meander.

An electromagnetic reflection plate (10; 50) according to claim 1, wherein each electrical connection (46; 46 (12) _a , 46 (12) _b , 46 (12) _c , 46 (12) _d ) from one metallic via to another is etched on the underside (44) of the second dielectric substrate layer (38).

3. Plate electromagnetic reflection (10; 50) according to claim 1 or 2, wherein each of said electrical connections (46; 46 (12) _a, 46 (12) _b, 46 (12) _c 46 ₍₁₂₎ ) has several meanders.

An electromagnetic reflection plate (10; 50) according to any one of claims 1 to 3, wherein:

the conductive elements (20, 22, 24, 26) are arrayed on the upper face (28) of the first dielectric substrate layer (30), and

each conductive member (20, 22, 24, 26) is in contact with four metal vias (42; 42 (12) _a , 42 (12) _b , 42 (12) _c , 42 (12) _d ), each of which four metal vias being connectable to another metal via a conductive element adjacent in line or in a column in the matrix.

5. Plate electromagnetic reflection (10; 50) according to any one of claims 1 to 4, wherein the metal vias (42; 42 (12) _a, 42 (12) _b, 42 (12) _c 42 ( 12) _d ) of each conductive element (20, 22, 24, 26) and their respective electrical connections (46; 46 (12) _a , 46 (12) _b , 46 (12) _c , 46 (12) _d ) are distributed in a central symmetry around a central axis of symmetry of this conductive element.

An electromagnetic reflection plate (10; 50) according to any one of claims 1 to 5, wherein at least a portion of the meandering electrical connections (46; 46 (12) _a , 46 (12) _b , 46 ( 12) _c , 46 (12) _d ) etched on the lower face (44) of the second layer (38) of dielectric substrate is further provided with adjustable phase shifters.

7. Plate electromagnetic reflection (10; 50) according to any one of claims 1 to 6, wherein each electrical connection meander (46; 46 (12) _a, 46 (12) _b, 46 (12) _c, 46 (12) _d ) engraved on the underside (44) of the second dielectric substrate layer (38) progressively widens from its end in contact with the corresponding metallic via (42; 42 (12) _a , 42 (12; ) _b , 42 (12) _c , 42 (12) _d ) to one of the edges of the conductive member (20, 22, 24, 26) under which it is etched.

An electromagnetic reflection plate (10; 50) according to any one of claims 1 to 7, wherein each of the conductive elements (20, 22,

24, 26) has one of the shapes of the set consisting of a square shape, a rectangular shape, a spiral shape, a fork shape, a cross shape with crutches and a dual form of crutches with crutches called UC-EBG form.

An electromagnetic reflection plate (10; 50) according to any one of claims 1 to 8, wherein the conductive elements (20, 22, 24, 26) are periodically distributed on the upper face (28) of the first dielectric substrate layer (30).

A miniature antenna device comprising:

an electromagnetic reflection plate (50) according to any one of claims 1 to 9, and

an antenna (52) having an average operating wavelength and disposed at a distance from the reflection plate (50) less than one-tenth of this average operating wavelength.