FR3049775A1 - ANTENNA V / UHF WITH OMNIDIRECTIONAL RADIATION AND SCANNING A BROADBAND FREQUENCY - Google Patents

Abstract

The invention relates to an antenna (1) for transmission / reception at one or more given operating frequencies comprising: - a ground plane (3), - a first layer (10), placed above the ground plane, comprising a source band (11) having a dimension (H) less than or equal to λ / 2, where λ is an operating wavelength, - a second layer (20), fixed on the first layer (10), comprising a magnetic resonator configured to inductively couple with the source band (11), and - a third layer (30), attached to the second layer (20), comprising an electric resonator configured to capacitively couple with the source band ( 11).

Description

FIELD OF THE INVENTION The invention relates to the field of antennas, and more particularly to antennas capable of covering the frequency bands ranging from about 100 MHz to about 500 MHz.

BACKGROUND

Currently, there are antennas capable of scanning frequency subbands, typically 118 MHz to 177 MHz at 180 MHz, 225 to 400 MHz or 400 to 500 MHz. On the other hand, there is no antenna capable of scanning all these frequencies and which is also omnidirectional. However, such a broadband frequency antenna is nevertheless sought, particularly in the field of communications, surveillance, navigation, etc. on vehicles (carriers) such as ships, boats or aircraft.

SUMMARY OF THE INVENTION

An object of the invention is therefore to propose an antenna solution having an omnidirectional radiation, which is capable of scanning a very wide band of frequencies ranging from at least 130 MHz to 500 MHz, which is further reduced in size and which can be done in a simple way and at a low cost.

For this, the invention proposes a transmitting / receiving antenna configured to cover a frequency band between 100 MHz and 600 MHz, preferably between 130 MHz and 500 MHz, said antenna comprising: - a ground plane, - a first layer, fixed on the ground plane, configured to be excited by a power source, said first layer comprising a source band having a dimension less than or equal to λ / 2, where λ is an operating wavelength. a second layer, fixed on the first layer, comprising a magnetic resonator configured to perform an inductive coupling with the source band; a third layer, fixed on the second layer, comprising an electric resonator configured to perform a capacitive coupling with the band; source.

Some preferred but non-limiting characteristics of the antenna described above are the following, taken individually or in combination: the operating wavelength λ corresponds to a median frequency of the frequency band swept by said antenna, typically a wavelength λ of one meter, - the source band has a dimension substantially equal to 0.504 λ or 0.35 λ, - the source band comprises an enlarged base from which extends a tongue substantially less wide than the base, the having a base having a width of about 0.15 λ and a height of about 0.075 λ and the tongue having a width of about 0.075 λ and a height of between about 0.35 λ and 0.5 λ, - the second layer comprises a dielectric support on which is fixed the magnetic resonator, said magnetic resonator comprising a metal plate on which is connected the mass and two side arms extending from its free ends of the metal plate, on either side of the source strip, the dielectric support comprises a material having a compressive strength of the order of 0.4 to 1.5 MPa, a resistance to traction on the order of 1.0 to 3 MPa and a shear strength of the order of 0.4 to 1.5 MPa, for a permittivity zr of the order of 1, for example a Rohacell® 31HF type foam, - the lateral arms having a bent shape so that each arm comprises a first portion substantially parallel to the source band and a second portion substantially perpendicular to the first portion and extending from the first portion towards the source band, the metal plate of the second layer has a substantially rectangular shape and has a width of about 0.61 λ for a height of about 0.157 λ, the first part of each side arm has a substantially rectangular shape and has a width of about 0.035 λ for a height of about 0.095 λ, and the second portion of each side arm has a substantially rectangular shape and has a width of about 0.035 λ for a height of about 0.22 λ, the metal plate of the second layer has a substantially rectangular shape and has a width of approximately 0.6λ for a height of approximately 0.0844λ, each side arm has a substantially rectangular shape and has a width of approximately 0.03λ for a height of about 0.07A, and - the metal plate further comprising nine plates, extending from the plate between the two side arms and each having a width of about 0.055 λ for a height of about 0.0351 λ. in which the second layer further comprises two L-shaped strips whose free ends are separated by a predefined distance and are positioned so as to extend on either side of the first layer, the antenna further comprises two additional strips extending over the first layer and the second layer, each additional strip being connected to one of the L-shaped strips of the second layer by means of a metal strip connection, which extends between the plane containing the additional strips and the plane containing the second layer, the additional strips are L-shaped and extend substantially parallel to the L-shaped strips of the second layer. the third layer comprises a substantially rectangular peripheral edge defining a rectangular internal space through which a central portion extends, the peripheral edge comprises a lower edge and an upper edge, substantially parallel and having a width of approximately 0.25 λ and a height of approximately 0.025 λ, and two substantially parallel lateral edges having a width of approximately 0.051 λ and a height of approximately 0.272 λ, and the central part comprises a substantially rectangular insert having a width of approximately 0.144 λ and a height of approximately 0.042 λ and defining a slot, the insert being connected to the upper edge and the lower edge of the peripheral edge via two rods having a height of 0.090 λ and a width of 0.025 λ, - the peripheral border is formed by four F-shaped sub-elements arranged in such a way that e to form a rectangle, each sub-element comprising an upright and two sleepers substantially perpendicular to the upright, the upright has a width of 0.255 λ and a height of 0.01738 λ, a first of said sleepers has a width of 0.051 λ and a height of 0.1263 λ, a second of said crosspieces has a width of 0.018 λ and a height of 0.0978 λ and is spaced from the first cross-member by a distance of 0.0675 λ, the posts are separated in pairs by a distance of 0.015 λ and the first crosspieces are separated in pairs by a distance of 0.02 λ, the central portion of the third layer comprises two E-shaped assemblies positioned substantially symmetrically with respect to a plane perpendicular to said third layer, the two sets are separated by a distance of 0.02969 λ, - the central part has a width of approximately 0.191 λ and a height of approximately 0.1785 λ, at the height of the insert being divided into two subparts each having a height of about 0.0806 λ. the source band, the magnetic resonator and the electric resonator are made of a metallic material having a conductivity greater than 58 × 10 6 S / m, for example in at least one of the following materials: aluminum, iron, copper, the first layer is placed at a distance of at least 0.1 λ, preferably of the order of 0.2 λ, from the ground plane, for example by means of return rods, and / or antenna has a dimension substantially less than or equal to 600 mm and a thickness less than or equal to 200 mm.

According to a second aspect, the invention proposes a vehicle, in particular a boat or an airplane, comprising a communication mast, said vehicle being characterized in that it comprises at least one antenna as described above fixed on the communication mast. .

Optionally, the vehicle comprises at least three antennas, fixed on the communication mast.

BRIEF DESCRIPTION OF THE DRAWINGS Other features, objects and advantages of the present invention will appear better on reading the detailed description which follows, and with reference to the appended drawings given by way of non-limiting examples and in which:

FIG. 1 is a perspective view of a first embodiment of an antenna according to the invention, in which part of the layers is visible in transparency,

FIG. 2 is a schematic sectional view of the antenna of FIG. 1,

FIG. 3 is a perspective view of the antenna of FIG. 1, in which the ground plane and the dielectric supports have been omitted,

FIG. 4 is a view from below of FIG. 3,

Figure 5a shows radiation patterns in the xOz plane of the antenna of Figure 1, for frequencies ranging from 180 MHz to 360 MHz (at a 20 MHz interval between each chart), respectively,

FIGS. 5b to 5g show radiation patterns in the xOz plane of the antenna of FIG. 1, for frequencies of 180 MHz, 200 MHz, 220 MHz, 300 MHz, 320 MHz and 340 MHz, respectively,

Figure 6a shows radiation patterns in the xOy plane of the antenna of Figure 1, for frequencies ranging from 180 MHz to 320 MHz (at a 20 MHz interval between each chart), respectively.

FIGS. 6b to 6g show the radiation patterns in the xOy plane of the antenna of FIG. 1, for frequencies of 180 MHz, 200 MHz, 220 MHz, 300 MHz, 320 MHz and 340 MHz, respectively,

FIG. 7 is a perspective view of a second embodiment of an antenna according to the invention, on which the second layer is visible in transparency, the ground plane and the dielectric supports having been omitted,

FIG. 8 is a schematic sectional view of the antenna of FIG. 7, on which the ground plane has been illustrated above,

FIGS. 9a and 9b are a view from above and a perspective view, respectively, of the first layer of the antenna of FIG. 7, the second and third layers being represented in transparency,

FIG. 10 is a perspective view of the second layer of the antenna of FIG. 7, the first and third layers being represented in transparency,

FIG. 11a is a perspective view of the third layer of the antenna of FIG. 7, the first and the second layers being represented in transparency;

FIG. 11b is a perspective view of a first portion of the third layer of the antenna of FIG.

Figure 11c is a top view of a second portion of the third layer of the antenna of Figure 11a.

Fig. 12 shows radiation patterns in the xOz plane of the antenna of Fig. 7, for frequencies ranging from 160 MHz to 480 MHz (at a 20 MHz interval between each chart), respectively,

Fig. 13 shows radiation patterns in the xOy plane of the antenna of Fig. 7, for frequencies ranging from 160 MHz to 480 MHz (at a 20 MHz interval between each chart), respectively, and

FIGS. 14a to 14f show the three-dimensional radiation patterns of the antenna of FIG. 7, for frequencies of 180 MHz, 240 MHz, 320 MHz, 400 MHz, 460 MHz and 500 MHz, respectively.

DETAILED DESCRIPTION OF AN EMBODIMENT

In order to scan a wide frequency band, an antenna 1 according to the invention comprises: - a ground plane 3, - a first layer 10, placed above the ground plane 3, configured to be excited by a source of power supply (coaxial cable) 2, said first layer 10 comprising a source band 11 having a length substantially less than or equal to λ / 2, where λ is a bandwidth operating wavelength, - a second layer 20, fixed on the first layer 10, comprising a magnetic resonator configured to perform an inductive coupling with the source band 11, - a third layer 30, fixed on the second layer 20, comprising an electric resonator configured to perform a capacitive coupling with the source band .

The first layer 10 is connected to the radiofrequency signal via a coaxial cable 2, while the second layer 20 is connected to ground. If necessary, the braid of the coaxial cable 2 can be used to connect the second layer 20 to ground. Optionally, the coaxial cable 2 may be shielded.

The operating wavelength λ corresponds to the median frequency of the frequency band that it is desired to scan with the aid of the antenna 1. In the following, the operating wavelength λ is equal to order of a metric, which corresponds to a frequency in the order of 300 MHz.

The ground plane 3 is conventional and constitutes the reference armature of the capacitive element of the antenna 1. Here, the ground plane 3 has a substantially parallelepipedal shape, the sides of the parallelepiped having a length at least equal to 1.2 λ, preferably at least 2 λ (when space permits). For λ = 1m, the sides of the parallelepiped can measure at least one meter twenty long.

In one embodiment, the ground plane 3 may be covered with a layer of ferrites in order to suppress the horizontal polarization (parasites) and to extend the frequency band towards the low frequencies. The thickness of the ferrite layer may be between 3 mm and 10 mm. The thicker the ferrite layer, the more the frequency band will be extended to lower frequencies.

In what follows, it should be noted that all the numerical values are provided with an approximation of 10%.

The first layer 10

The first layer 10 is preferably placed at a distance at least equal to one-tenth of the operating wavelength λ of the ground plane 3, ie at least ten centimeters, preferably of the order of twenty centimeters. (for an operating wavelength λ of one meter).

The source strip 11 is made of metal and has a generally elongated shape. It is configured to allow the emission of electromagnetic waves.

The source band 11 has for this purpose a base 11 comprising an enlarged base 12 from which extends a tongue 13 substantially smaller than the base 12. A length of the source band 11 is also substantially less than or equal to λ / 2 (at 10% near). The power source 2 is connected to the enlarged base 11 of the source band 11.

In the following, the height of the different parts of the antenna is defined in the direction of extension of the source band 11, while their width is defined in the direction perpendicular to its direction of extension, in the plane of the antenna. layer 10, 20, 30 containing said portion.

In a first embodiment illustrated in FIGS. 1 to 4, the base 12 has a lower edge on which the power source 2 is connected and having a width L1 of approximately 0.15 λ (ie 150 mm, for the wavelength operating mode of one meter), a height H1 of about 0.075 λ (ie 75 mm for λ = 1m) and a vertex L2, opposite the lower edge, of about 0.075 λ. The sides of the base 11 are straight and substantially perpendicular to the lower edge of the base 12 60% to 90% of its height and then gradually converge towards the top.

The tongue 13 in turn is substantially rectangular in shape and has a substantially constant width L2 of about 0.075 λ and a height H2 of about 0.429 λ (ie 429 mm for λ = 1m).

The total height H (= H1 + H2) of the base 11 is therefore 0.504 λ. The base 11 and the tongue 13 are formed integrally and in one piece, for example by cutting a metal sheet or by depositing on a dielectric.

Here, the source band 11 has a length of 0.504 λ (ie 504 mm, for the operating wavelength λ of one meter).

In a second embodiment illustrated in FIGS. 7 and following, the base 12 has a substantially rectangular shape with a width L4 of the order of 0.15 λ and a height H4 of the order of 0.01 λ.

The tongue 13 is also of substantially rectangular shape and has a width L3 of about 0.1 λ (ie 100 mm, for the operating wavelength of one meter) for a height H3 of about 0.35 λ ( ie 350 mm for λ = 1 m).

The total height H (= H3) of the base 11 is 0.35 λ.

The base 12 and the tongue 13 can be formed separately then reported and fixed together, for example by cutting a metal sheet, or formed integrally and in one piece by depositing on a dielectric.

Whatever the embodiment, the source strip 11 may be made by cutting a sheet having a thickness of the order of 2 mm made in one of the following materials: aluminum, iron, copper, etc. or any metal having a conductivity greater than 58 x 10® S / m.

The second layer 20

The second layer 20 comprises the magnetic resonator and is configured to induce an inductive coupling with the source band 11. The magnetic resonator is fixed on a dielectric support 5 having a good mechanical strength (that is to say a good resistance to compression, tensile and shear) and which is substantially electromagnetically transparent.

The dielectric support 5 may for example comprise a material having a compressive strength of the order of 0.4 to 1.5 MPa, a tensile strength of the order of 1.0 to 3 MPa and a shear strength of the order of 0.4. at 1.5 MPa, for a Sr permittivity of the order of 1. For example, the support may comprise a Rohacell® 31 HP type foam, which has a Sr permittivity of 1.07.

The dielectric support 5 may have a thickness of 0.004 λ (ie 4.0 mm for λ = 1 m).

The magnetic resonator may in particular comprise a metal plate 21 on which the reference potential (of the ground plane 3) is connected via the metal braid of the coaxial cable 2 (radiofrequency coaxial power source) and two lateral arms 22 extending from the free ends of the plate 21, on either side of the source strip 11. The first layer and the second layer extend in separate substantially parallel planes.

In a first embodiment, the plate 21 has a substantially rectangular shape and has a width L7 of about 0.61 λ for a height H7 of about 0.157 λ (ie 610 mm × 157 mm, for λ = 1 m).

Here, the lateral arms 22 have a bent shape, so that each arm 22 comprises an upright 23, substantially parallel to the source strip 11, and a crossbar 24, substantially perpendicular to the upright 23 and extending from the upright 23 direction of the source band 11.

The upright 23 of each lateral arm 22 then has a substantially rectangular shape and has a width L8 of approximately 0.035 λ for a height H8 of 0.363 λ (ie 35 mm × 363 mm, for λ = 1 m). In other words, the width of the plate 21 between the two internal edges of the lateral arms 22 is of the order of (0.51 λ) 0.51 λ (ie 510 mm, for λ = 1 m).

The cross member 24 of each lateral arm 22 has a substantially rectangular shape with a width L9 of 0.255 λ and a height H9 of 0.035 λ (ie 255 mm × 35 mm, for λ = 1 m). The sleepers 24 are therefore separated by a distance D2 of approximately 0.1 λ (ie 100 mm, for λ = 1 m). In total, we have 2xL9 + D2 = 0.61 λ.

When the second layer 20 is placed on the first layer 10, the free end of the tongue 13 of the source strip 11 extends between the two free ends of the crosspieces 24 of the lateral arms 22 of the magnetic resonator.

In a second embodiment, the plate 21 has a substantially rectangular shape and has a width L10 of about 0.6 λ for a height H10 of about 0.0844 λ (ie 600 mm × 84.4 mm, for λ = 1 m).

Here, the lateral arms 22 comprise only an upright 23 of substantially rectangular shape having a width L11 of about 0.03 λ for a height H11 of about 0.070 λ (evening 30 mm × 70 mm, for λ = 1 m). In other words, the total height of the magnetic resonator is of the order of 0.1554 λ (ie 154.4 mm, for λ = 1 m).

The second layer 20 further comprises nine plates 24, extending from the plate 21 between the two lateral arms 22 and each having a width L12 of approximately 0.055 λ for a height H12 of approximately 0.0351 λ (ie 55 mm x 35.1 mm, for λ = 1 m). The plates 24 are spaced apart by a distance D3 of about 0.013 λ.

For example, the plates 24 may each be attached and fixed to the plate 21: for this purpose, it is possible to make plates 24 having a greater height, for example 0.09 λ, and to fix them on the plate 21 so that only a height H12 of 0.0351 λ exceeds said plate 21.

Optionally, as can be seen in particular in FIGS. 9a and 9b, the second layer 20 may also comprise two L-shaped strips 14 each comprising a first strip 15 having a width L5 of approximately 0.25 λ and a height H5 of approximately 0.02 λ (ie 250 mm × 20 mm, for λ = 1 m), and a second strip 16, extending perpendicularly from one end of the first strip 15 and having a width L6 of about 0.03 λ and a height H6 of approximately 0.403 λ (ie 30 mm and 403 mm, for λ = 1 m). The free ends of the first strips 15 are separated by a distance DI of the order of 0.1 λ, and are positioned relative to the base 11 of the first layer 10 so as to extend at the free end of the tongue 13. The excitation is formed by the tongue 13 and extended at its end by the base 12.

Optionally, the second layer 20 may further comprise two third strips 18 extending above the first layer 10 and the second layer 20. Each third strip 18 is connected to the second strip 16 facing the second layer 20 by means of a metal connecting strip 17, which then extends between the plane containing the third strips 18 and the plane containing the second layer 20.

The second strip 16, the connection strip 17 and the third strip 18 together form a U-shaped dipole.

Each third band 18 may have a width L25 of approximately 0.03 λ and a height H25 of approximately 0.403 λ (ie 30 mm × 403 mm, for λ = 1 m). The first layer 20 is at a distance of 0.04 λ from the second layer 20 and at a distance of 0.04 λ from the third connection strips.

For reasons of symmetry, the second layer 20 may further comprise two fourth strips (not shown in the figures) each extending from the free end of the third strips 18, substantially parallel to the first strips 15. The fourth strips then have dimensions similar to the first strips 15, a width L5 of about 0.25 λ and a height H5 of about 0.02 λ (ie 250 mm × 20 mm, for λ = 1 m). Two parallel and substantially identical L-shaped structures are thus obtained.

Whatever the embodiment, the different parts of the magnetic resonator 20 are made of metal and can be formed integrally and in one piece, for example by cutting a metal sheet or by depositing on a dielectric.

Typically, analogously to the source band 11, the magnetic resonator 20 can be made by cutting a sheet having a thickness of the order of 2 mm made in one of the following materials: aluminum, iron, copper, etc. . or any metal having a conductivity greater than 58 10® S / m.

The second layer 20 is therefore a first metamaterial.

The third layer 30

The third layer 30 comprises an electric resonator and is configured to perform a capacitive coupling with the source band 11. The electric resonator is fixed on a dielectric support 6 having good mechanical strength and which is substantially electromagnetically transparent.

The dielectric support 6 of the third layer 30 may, analogously to the dielectric support 5 of the second layer 20, comprise a material having a compressive strength of the order of 0.4 to 1.5 MPa, a tensile strength of order of 1.0 to 3 MPa and a shear strength of the order of 0.4 to 1.5 MPa, for a Sr permittivity of the order of 1. For example, the support may comprise a Rohacell® 31HF type foam.

In a first embodiment, the dielectric support 6 may have a thickness of 0.004 λ (ie 4.0 mm, for λ = 1 m).

Where appropriate, the dielectric support of the second and third layers 30 may be merged. The second and third layers 30 then extend in the same plane, the electric resonator of the third layer 30 being fixed on the dielectric support 5 of the second layer 20 (see for example Fig. 8).

The electric resonator comprises a peripheral rim 31 of substantially rectangular shape defining a rectangular through-going internal space within which a central portion 35 extends.

In a first embodiment, the peripheral edge 31 comprises a lower edge 32 and an upper edge 33, substantially parallel and having a width L13 of about 0.25 λ and a height H13 of about 0.025 λ (ie 250 mm × 25 mm). , for λ = 1 m), and two substantially parallel lateral edges 34 having a width L14 of about 51 mm and a height H14 of about 0.272 λ (ie 272 mm, for λ = 1 m). The lateral edges 34 of the peripheral edge 31 are therefore separated by a distance of 0.145 λ (ie 145 mm, for λ = 1 m).

The lower edge 32 and the upper edge 33 extend substantially parallel to the metal plate 21 of the magnetic resonator 20 while the lateral edges 34 extend along the uprights 23 of the lateral arms 22.

The distance D4 between the lower edge 32 of the electrical band and the metal plate 21 of the magnetic resonator is approximately 0.051 λ (ie 51 mm for λ = 1 m). The distance D5 between a lateral edge 34 of the electric resonator 30 and the adjacent lateral arm 23 of the magnetic resonator is approximately 0.145 λ (ie 145 mm for λ = 1 m).

The central portion 35 comprises an insert of substantially rectangular shape having a width L15 of approximately 0.144 λ and a height H15 of approximately 0.042 λ (ie 144 mm × 42 mm, for λ = 1 m) and defining an equally rectangular through slot configured to achieve a capacitive coupling with the source band 11. The height H16 of the through slot is about 0.022 λ (ie 22 mm for λ = 1 m). The insert 35 is connected to the upper edge 33 and the lower edge 32 of the peripheral edge 31 by means of two rods 36 having a height H17 of 0.09 λ and a width L17 of 0.025 λ (ie 90 mm × 25 mm for λ = 1 m) configured to produce, with the peripheral edge 31, an inductive coupling with the source strip 11.

The electric resonator 30 forms a 2LC circuit.

The different parts of the electric resonator 30 may be integrally formed in one piece, for example by cutting a metal sheet or by depositing on a dielectric.

It will be noted that, when the three layers 10, 20, 30 are superimposed, the strips of the central portion 35 of the electric resonator 30 are superimposed with the tongue 13 of the source strip 11 and extend substantially along said tongue 13, while the lateral edges 34 of the peripheral edge 31 of the electric resonator 30 extend on either side of the tongue 13.

In a second embodiment, the peripheral edge 31 is formed by four identical F-shaped sub-elements 37 arranged to form substantially a rectangle (see Fig. 1b).

Each sub-element 37 comprises an upright 38 and two crosspieces 39, 40 substantially perpendicular to the upright 38, a first of said crosspieces 39 extending from a free end of the upright 38 while the second crossbar 40 extends between the first cross member 39 and the other free end of the post 38.

The post 38 has a width L18 of 0.255 λ and a height H18 of 0.03 λ (ie 255 mm × 30 mm for λ = 1 m).

The first crosspiece 39 has a width L19 of 0.051 λ and a height H19 of 0.1263 λ (ie 51 mm x 126.3 mm, for λ = 1 m).

The second crosspiece 40 has a width L20 of 0.018 λ and a height H20 of 0.0978 λ (ie 18 mm × 97.8 mm, for λ = 1 m) and is spaced from the first cross member 39 by a distance D6 of 0.0675 λ (ie 67.5 mm, for λ = 1 m).

In order to form the peripheral border 31, the sub-elements 37 are placed symmetrically with respect to two perpendicular planes so that the first crosspieces 39 and the uprights 38 form corners of the peripheral border 31 and define the internal space therethrough . The second cross members 40 therefore extend in pairs.

The uprights 38 are separated in pairs by a distance D7 of 0.015 λ (15 mm for λ = 1 m), while the first crosspieces 39 are separated in pairs by a distance D8 of 0.02 λ (20 mm, for λ = 1 m). A first slot having a width D7 of 0.015 λ thus crosses the peripheral edge 31, between the free ends of the uprights 38, and a second slot having a height D8 of 0.02 λ passes through the peripheral edge 31 between the free ends of the first crosspieces 39.

In this second embodiment, the central portion 35 of the third layer 30 comprises two identical E-shaped assemblies 41 (see FIG.11c) positioned substantially symmetrically with respect to a plane perpendicular to the dielectric support 5. The two sets 41 and form an insert of substantially rectangular shape further comprising two central strips 42 extending opposite. The two sets 41 are separated by a distance D9 of 0.02969 λ (ie 29.69 mm, for λ = 1 m), which forms a third slot. This third slot is centered on the axis defined by the extension direction of the second slot of the peripheral edge 31 and is configured to perform a capacitive coupling with the source strip 11.

The rectangular part of the insert has a width L21 of about 0.1855 λ and a height H21 of about 0. 191 λ (ie 178.5 mm × 191 mm, for λ = 1 m), the height H21 of the insert being divided into two subparts each having a height H22 of about 0.0806 λ (ie 80.6 mm, for λ = 1 m) and being spaced apart by the third slot. The central strips 42 have a width L23 of 0.0126 λ (ie 12.6 mm, for λ = 1 m) for a height H23 of 0.0685 λ (ie 68.5 mm, for λ = 1 m). The central strips 42 are also spaced a distance D9 of 0.02969 λ, which corresponds to the third slot.

The central portion 35 of the electric resonator thus forms an ELC circuit.

Note that when the three layers 10, 20, 30 are superimposed, the central strips 42 of the central portion 35 of the electric resonator 30 are superimposed with the tongue 13 of the source strip 11 and extend substantially along said tongue 13, while the first and second crosspieces 39, 40 of the peripheral edge 31 of the electrical resonator 30 extend on either side of the tongue 13 of the first layer 10, where appropriate between the second 16 strips of the second layer 20 (and optionally the third arms 18).

Whatever the embodiment, the different parts of the electrical resonator 30 may be formed integrally and in one piece, for example by cutting a metal sheet or by depositing on a dielectric.

Typically, analogously to the source band 11, the electric resonator can be made by cutting a sheet having a thickness of the order of 2 mm made of one of the following materials: aluminum, iron, copper, etc. or any metal having a conductivity greater than 58x 10® S / m.

The third layer 30 thus constitutes a second metamaterial.

In practice, the magnetic resonator 20 and the electric resonator 30 are excited by the source band 11 and interact so as to widen the emission diagram of the antenna 1 so that the antenna 1 transmits continuously in the selected frequency band .

An antenna 1 comprising the three layers described above according to the first embodiment (which corresponds to FIGS. 1 to 6g) is then capable of covering a frequency band ranging from 160 MHz to 320 MHz (see FIGS. 5a to 5g). and 6a to 6g which are radiation diagrams in the bandwidth between 160 MHz and 320 MHz). It also has small dimensions (less than 600 mm wide and 200 mm thick).

In one embodiment, when the ground plane 3 of this antenna 1 comprises a layer of ferrites, the antenna can cover a frequency band ranging from 160 MHz to 320 MHz (for example with a layer of ferrites having a thickness of 3 mm), or even from 120 MHz to 320 MHz (with a layer of ferrites having a thickness of 5 mm).

Furthermore, an antenna 1 comprising the three layers described above according to the second embodiment (which corresponds to FIGS. 7 to 14f) is then capable of covering a frequency band ranging from 160 MHz to 500 MHz (see FIGS. 12 and 13 which are radiation diagrams in the bandwidth between 160 MHz and 480 MHz and the three-dimensional diagrams shown in Figures 14a to 14f). It also has small dimensions (less than 600 mm wide and less than 200 mm thick). This broadening of the bandwidth with respect to the first embodiment illustrated in particular in FIG. 1 is allowed in particular thanks to the configuration of the third layer 30, and in particular thanks to the central part of the third layer 30 which carries out the capacitive coupling. with the source tape 11.

In one embodiment, when the ground plane 3 of this antenna 1 comprises a layer of ferrites, the antenna can cover a frequency band ranging from 130 MHz to 500 MHz (for example with a layer of ferrites having a thickness of 3 mm), or even from 120 MHz to 500 MHz (with a layer of ferrites having a thickness of 5 mm).

Note that the two antenna embodiments 1 described above and illustrated in the figures are not limiting. In particular, the layers of the first and second embodiments may be interchanged. Typically, an example of antenna 1 according to the invention (not visible in the figures) may comprise a first layer 10 according to the second embodiment (as illustrated in Figs 9a and 9b), and a second and a second third layer 20, 30 according to the first embodiment (as illustrated in Fig. 3). Another embodiment (not visible in the figures) may also comprise first and third layers 10, 30 according to the second embodiment (as illustrated in Figs 9a, 9b, 11a and 11b) and a second layer According to the first embodiment (as illustrated in Fig. 3).

Moreover, other dimensions can be envisaged for the second layer of antenna 1 according to the second embodiment. For example, the following dimensions can be envisaged, replacing the dimensions indicated above (for λ = 1 m): - L10 = 0.6 λ and H10 = 0.1393 λ (ie 600 mm x 139.3 mm) - L11 = 0.03 λ and H11 = 0.0151 λ (ie 30 mm x 15.1 mm) - L12, H12 and D3 can remain unchanged - L5 = 0.25 λ and H5 = 0.03 λ (ie 250 mm x 30 mm) - L6 = 0.03 λ and H6 = 0.35 λ ( ie 30 mm x 350 mm) - DI can remain unchanged - L25 = 0.03 λ and H25 = 0.35 λ (ie 30 mm x 350 mm)

An antenna 1 according to the invention can be implemented in particular on a vehicle, such as a boat, an airplane, etc.

In the case of a boat, it further comprises a communication mast on which is fixed at least one antenna 1 according to the invention. Preferably, several antennas 1 are fixed on the mast. The antennas 1 may be identical and have the same layers 10, 20, 30 having the same dimensions, or different and comprise layers 10, 20, 30 different and / or different size.

Typically, the mast may generally have the shape of a truncated prism having three triangular plane faces inclined so a vertex is cut, or a trapezoid having four inclined plane faces joined by a rectangular upper face. An antenna 1 can then be fixed on each side of the mast in order to increase the transmission and reception capacity of the assembly thus formed, the faces of the mast acting as a ground plane 3 for each antenna 1.

The mast can also house standby radar equipment, optronic systems, etc.

Claims (25)

Antenna (1) transmitting / receiving configured to cover a frequency band between 100 MHz and 600 MHz, preferably between 130 MHz and 500 MHz, said antenna comprising: - a ground plane (3), - a first layer (10), fixed on the ground plane, configured to be excited by a power source, said first layer (10) comprising a source band (11) having a dimension (H) less than or equal to λ / 2 , where λ is an operating wavelength, - a second layer (20), fixed on the first layer (10), comprising a magnetic resonator configured to perform an inductive coupling with the source band (11), - a third layer (30), fixed on the second layer (20), comprising an electrical resonator configured to capacitively couple with the source band (11). 2. Antenna (1) according to claim 1, wherein the operating wavelength λ corresponds to a median frequency of the frequency band swept by said antenna (1), typically a wavelength λ of one meter . 3. Antenna (1) according to one of claims 1 or 2, wherein the source band (11) has a dimension (H) substantially equal to 0.504 λ or 0.35 λ. 4. Antenna (1) according to one of claims 1 to 3, wherein the source strip (11) comprises an enlarged base (12) from which extends a tongue (13) substantially smaller than the base (12). ), the base (12) having a width (L1) of about 0.15 λ and a height (H1) of about 0.075 λ and the tongue (13) having a width (L2) of about 0.075 λ and a height (H2) between about 0.35 λ and 0.5 λ. 5. Antenna (1) according to one of claims 1 to 4, wherein the second layer (20) comprises a dielectric support (5) on which is fixed the magnetic resonator, said magnetic resonator comprising a metal plate (21) on which is connected the mass and two side arms (22) extending from its free ends of the metal plate (21), on either side of the source strip (11). 6. Antenna (1) according to claim 5, wherein the dielectric support (5) comprises a material having compressive strength of the order of 0.4 to 1.5 MPa, a tensile strength of the order of 1.0 to 3 MPa and a shear strength of the order of 0.4 to 1.5 MPa, for a Sr permittivity of the order of 1, for example a Rohacell® 31HF type foam. 7. Antenna (1) according to one of claims 5 or 6, wherein the lateral arms (22) have a bent shape so that each arm (22) comprises a first portion (23) substantially parallel to the source strip ( 11) and a second portion (24) substantially perpendicular to the first portion (23) and extending from the first portion (23) toward the source band (11). 8. Antenna (1) according to claim 7, wherein: - the metal plate (21) of the second layer (20) has a substantially rectangular shape and has a width (L7) of about 0.61 λ for a height (H7 ) of approximately 0.157λ, the first part (23) of each lateral arm (22) has a substantially rectangular shape and has a width (L8) of approximately 0.035λ for a height (H8) of approximately 0.095λ, and - the second portion (24) of each lateral arm (22) has a substantially rectangular shape and has a width (L9) of about 0.035 λ for a height (H9) of about 0.22 λ. 9. Antenna (1) according to one of claims 1 to 6, wherein - the metal plate (21) of the second layer (20) has a substantially rectangular shape and has a width (L10) of about 0.6 λ for a height (H10) of approximately 0.0844 λ, - each lateral arm (23) has a substantially rectangular shape and has a width (L11) of approximately 0.03 λ for a height (H11) of approximately 0.07A, and the plate metal plate (21) further comprising nine plates (24), extending from the plate (21) between the two side arms (23) and each having a width (L12) of about 0.055 λ for a height (H 12) about 0.0351 λ. 10. Antenna (1) according to one of claims 1 to 6, wherein the second layer (20) further comprises two strips (14) L-shaped whose free ends are separated by a distance (DI) predefined and are positioned to extend on either side of the first layer (10). Antenna (1) according to claim 10, further comprising two additional strips (18) extending above the first layer (10) and the second layer (20), each additional strip (18) being connected at one of the L-shaped strips (14) of the second layer (20) by means of a metal connecting strip (17), which extends between the plane containing the additional strips (18) and the plane containing the second layer (20). Antenna (1) according to claim 11, wherein the additional strips (18) are L-shaped and extend substantially parallel to the L-shaped strips (14) of the second layer (20). 13. Antenna (1) according to one of claims 1 to 2, wherein the third layer (30) comprises a peripheral edge (31) of substantially rectangular shape defining a rectangular internal space through which extends a central portion (35). 14. Antenna (1) according to claim 13 wherein: the peripheral edge (31) comprises a lower edge (32) and an upper edge (33), substantially parallel and having a width (L13) of about 0.25 λ and a height (H13) of approximately 0.025 λ, and two substantially parallel lateral edges (34) having a width (L14) of approximately 0.051 λ and a height (H14) of approximately 0.272 λ, and - the central portion (35) ) comprises an insert of substantially rectangular shape having a width (L15) of about 0.144 λ and a height (H15) of about 0.042 λ and defining a slot, the insert being connected to the upper edge and the lower edge of the edge peripheral (31) via two rods (36) having a height (H17) of 0.090 λ and a width (L17) of 0.025 λ. Antenna (1) according to claim 13 wherein the peripheral border (31) is formed by four F-shaped sub-elements (37) arranged to form a rectangle, each sub-element (37) comprising a post (38) and two crosspieces (39, 40) substantially perpendicular to the upright (38). 16. Antenna (1) according to claim 15, wherein: - the upright (38) has a width (L18) of 0.255 λ and a height (H18) of 0.01738 λ. a first of said crosspieces (39) has a width (L19) of 0.051λ and a height (H19) of 0.1263λ, a second of said crosspieces (40) has a width (L20) of 0.018λ and a height (H20) of 0.0978 λ (ie 18 mm x 97.8 mm, for λ = 1 m) and is spaced from the first crossbar (39) by a distance (D6) of 0.0675 λ. 17. Antenna (1) according to one of claims 15 or 16, wherein the uprights (38) are separated in pairs by a distance (D7) of 0.015 λ and the first crosspieces (39) are separated in pairs a distance (D8) of 0.02 λ. 18. Antenna (1) according to one of claims 15 to 17, wherein the central portion (35) of the third layer (30) comprises two sets (41) E-shaped positioned substantially symmetrically with respect to a plane perpendicular to said third layer (30). 19. Antenna (1) according to claim 18, wherein the two sets (41) are separated by a distance (D9) of 0.02969 λ. 20. Antenna (1) according to one of claims 18 or 19, wherein the central portion (35) has a width (L21) of about 0.191 λ and a height (H21) of about 0.1785 λ, the height ( H21) of the insert being divided into two subparts each having a height (H22) of about 0.0806λ. 21. Antenna (1) according to one of claims 1 to 20, wherein the source strip (11), the magnetic resonator and the electric resonator are made of a metallic material having a conductivity greater than 58 x 10® S / m for example in at least one of the following materials: aluminum, iron, copper. 22. Antenna (1) according to one of claims 1 to 21, wherein the first layer (10) is placed at a distance at least equal to 0.1 λ, preferably of the order of 0.2 λ, of the ground plane (3), for example using return rods (4). 23. Antenna (1) according to one of claims 1 to 22, having a dimension substantially less than or equal to 600 mm and a thickness less than or equal to 200 mm. 24. Vehicle, in particular a boat or an airplane, comprising a communication mast, said vehicle being characterized in that it comprises at least one antenna (1) according to one of claims 1 to 23 fixed on the communication mast. 25. Vehicle according to claim 24, characterized in that it comprises at least three antennas (1), fixed on the communication mast.