EP3692598B1 - Antenna with partially saturated dispersive ferromagnetic substrate - Google Patents

Antenna with partially saturated dispersive ferromagnetic substrate Download PDF

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Publication number
EP3692598B1
EP3692598B1 EP18793251.2A EP18793251A EP3692598B1 EP 3692598 B1 EP3692598 B1 EP 3692598B1 EP 18793251 A EP18793251 A EP 18793251A EP 3692598 B1 EP3692598 B1 EP 3692598B1
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EP
European Patent Office
Prior art keywords
antenna
magnet
dispersive
ferrite
mhz
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EP18793251.2A
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German (de)
French (fr)
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EP3692598A1 (en
Inventor
Evgueni KAVERINE
Sébastien PALUD
Franck Colombel
Mohamed Himdi
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Universite de Rennes 1
Telediffusion de France ets Public de Diffusion
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Universite de Rennes 1
Telediffusion de France ets Public de Diffusion
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/44—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the electric or magnetic characteristics of reflecting, refracting, or diffracting devices associated with the radiating element
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/36—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith
    • H01Q1/38—Structural form of radiating elements, e.g. cone, spiral, umbrella; Particular materials used therewith formed by a conductive layer on an insulating support
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/005—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with variable reactance for tuning the antenna
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q7/00—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop
    • H01Q7/06—Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop with core of ferromagnetic material
    • H01Q7/08—Ferrite rod or like elongated core

Definitions

  • the invention relates to an antenna with a ferromagnetic substrate.
  • the invention relates to a ferromagnetic substrate antenna which is ultra-compact in the vertical plane compared to the wavelength, which can be used in reception or in transmission in the Telec (30-300 kHz), hectometric (0, 3-3 MHz), decametric (3-30 MHz) and metric (30-300 MHz).
  • the antenna is particularly suitable, for example, in medium- and high-power wideband or narrowband transmission systems conveying the information in the form of modulated or unmodulated signals and which propagate over the airwaves.
  • the antenna favors the propagation of the wave in a privileged direction (directional antenna).
  • the electrically small antennas have an impedance presenting a strong reactive component which does not allow their use in an efficient and direct manner in systems with normalized real impedance (typically 50 ⁇ ).
  • the impedance matching of this type of antenna is often difficult and generally allows tuning only over a narrow frequency band.
  • the narrow bandwidth of such an antenna is often unstable, which is particularly problematic on transmission, in particular for high-power applications.
  • the invention aims to overcome at least some of the drawbacks of known electrically small antennas.
  • the invention aims to provide, in at least one embodiment of the invention, an ultra-compact vertically polarized antenna in the vertical plane and broadband which can operate on transmission.
  • the invention also aims to provide, in at least one embodiment, an antenna providing good radiation efficiency while maintaining a wide passband by stabilizing the variation of the impedance.
  • the invention also aims to provide, in at least one embodiment of the invention, a directional antenna (or directional antenna).
  • the invention relates to an antenna as defined in the appended claims.
  • a dispersive ferrite has high dielectric losses and/or high magnetic losses.
  • the dispersive ferromagnetic substrate used in the context of the present invention consists in particular of spinel ferrite which is well suited to the manufacture of magnetic antennas with a wide bandwidth and of small size.
  • An antenna according to the invention therefore makes it possible, thanks to the use of a dispersive ferromagnetic substrate (dispersive ferrite) partially saturated (that is to say whose magnetic losses and relative magnetic permeability are reduced locally and gradually), to ensure good radiation efficiency while maintaining a wide passband by stabilizing the variation of the impedance. Indeed, the dispersive ferrite allows this stabilization of the impedance, but greatly reduces the radiation.
  • the dispersive ferrite may experience rapid heating and performance degradation near the Curie point during long-duration and high-power emissions.
  • the gradual and local modification of the characteristics of the ferrite makes it possible to compensate for this reduction in radiation in order to achieve a suitable gain, while preserving the stabilization of the impedance, and with reduced heating in emission mode.
  • the terms "vertical plane” and “horizontal plane” are understood by considering the antenna in its arrangement during its preferential operation in vertical polarization, the antenna being able of course to have a different orientation when it is not in operation and /or when the desired polarization is different (in particular horizontal).
  • a high relative magnetic permeability is typical of ferromagnetic materials, and is well above 1, in particular between 10 and 10000.
  • the high tangent of magnetic losses, corresponding to high magnetic losses, is often designated by the symbol tan ⁇ whose value is greater than 0.1.
  • the magnetic loss tangent corresponds to the ratio of the imaginary part to the real part of the relative magnetic permeability.
  • the high value of these magnetic characteristics depends on the frequency used. These values are provided at the working frequency of the antenna, that is to say at a frequency included in a frequency band on which the impedance matching of the antenna is carried out.
  • the antenna is suitable for receiving or transmitting at a frequency comprised in the Telec (30-300 kHz), hectometric (0.3-3 MHz), decametric (3 -30 MHz) or metric (30-300 MHz).
  • the maximum working frequency of the antenna is of the order of 300 MHz (ie corresponding to the upper limit of the band of metric frequencies 30-300 MHz).
  • the high relative magnetic permeability of the dispersive ferrite makes it possible to increase the miniaturization factor of the antenna.
  • the antenna shown in figure 1 has a maximum dimension less than 0.03 ⁇ at a working frequency equal to 30 MHz ( ⁇ designating the corresponding wavelength) or less than 0.01 ⁇ considering only the radiating metal parts of the antenna.
  • the maximum dimensions of the radiating part of the antenna of D1 would be limited to 0.22 ⁇ at this same working frequency.
  • Such a limitation comes from the fact that only the high permittivity of the YIG G-113 material contributes to the reduction in size of the antenna.
  • the magnetic permeability and the relative permittivity of the dispersive ferrite according to the specifics of the invention both contribute to increasing the miniaturization factor of the antenna and with the particularity that the contribution of the magnetic permeability is stronger than that of permittivity.
  • the gradual and local modification makes it possible to locally and gradually reduce these values, in particular down to a relative magnetic permeability lower than the permeability of the ferrite, typically between 1 and 100 and always greater than 1, and a tangent of lower magnetic losses.
  • the dispersive ferrite is thus non-homogeneous.
  • the antenna also has a directivity in the horizontal plane, without needing to be networked with other antennas or having recourse to one or more external parasitic elements.
  • the non-ferrous metal forming the plates is for example copper, brass, aluminum, etc.
  • the means for local modification of the magnetic characteristics of the dispersive ferrite are a magnet (permanent magnet or electromagnet), or at least one piece of material having a low relative magnetic permeability and a low loss tangent.
  • the magnet is arranged on a metal plate of the antenna, preferably on the radiating part.
  • the magnet When the magnet is an electromagnet, it is powered by a direct current generator, preferably variable, thus making it possible to modify the strength of the magnetic field generated by the electromagnet, thus modifying the performance of the antenna (parameters S, gain and shape of the radiation pattern).
  • the gain can for example be varied on command, or the impedance can be adjusted to achieve that desired in the system to which the antenna is connected, for example 50 ⁇ .
  • the piece or pieces of material inserted are included in the manufacture of the ferrite.
  • the arrangement of parts can be configured to achieve desired performance.
  • the dispersive ferrite has a size in the horizontal plane greater than the size of the metal plates.
  • the larger size of the ferrites than the metal plates improves the efficiency of the radiation. If the antenna is of the monopole type, this characteristic also makes it possible to increase the directivity.
  • the size of the ferrites can be greater in a single direction.
  • the antenna comprises at least one short-circuit connecting the ground plane and the radiating part, in contact with a contour of the dispersive ferrite.
  • an antenna without a short circuit is a monopole type antenna
  • an antenna having a short circuit is a semi-open type antenna
  • an antenna having a short circuit disposed opposite of the exciter at the contour of the dispersive ferrite forms a loop-type antenna.
  • the antenna comprises a succession of dispersive ferrite and magnet stacked alternately between the radiating part and the ground plane.
  • the antenna thus forms a stacked antenna.
  • Stacked antennas allow higher gains to be achieved. It is also possible to vary the degree of saturation of the dispersive ferrites according to the layers, thus allowing a modification of the adaptation, of the gain and of the radiation.
  • the radiating part comprises a metal plate between each ferrite and magnet.
  • the metal plates are interconnected.
  • the invention also relates to an antenna characterized in combination by all or some of the characteristics mentioned above or below.
  • the values of the magnetic induction of the magnets are expressed in gauss in this application, 1 gauss (of symbol G) equaling 10 -4 tesla (of symbol T).
  • ⁇ designates the wavelength at the main frequency (central frequency if emission on a frequency band) of emission or reception of the antenna.
  • the figure 1 schematically represents in exploded perspective an antenna according to a first embodiment of the invention.
  • the picture 3 schematically shows in side section an antenna according to the first embodiment of the invention.
  • the antenna comprises two non-ferrous metal plates (for example copper, brass, aluminium, etc.), a first plate forming a radiating part 4 H and a second plate forming a ground plane 4 B. Between the two metal plates is placed a dispersive ferromagnetic substrate, called dispersive ferrite 1.
  • the metal plates and the dispersive ferrite 1 are in a flat shape extending mainly along a horizontal plane, so as to present a minimum vertical bulk for an antenna with vertical polarization.
  • the radiating part 4 H totally or partially covers the dispersive ferrite 1, and can be composed of several parts having different shapes connected together.
  • the radiant 4 H part can also come in several forms complex, for example a meander as shown with reference to the figure 25 according to one embodiment of the invention.
  • the dispersive ferrite 1 has a greater horizontal bulk than the metal plates, in particular along a length (the plates are square while the dispersive ferrite 1 is rectangular), which allows an improvement in radiation (higher gain) .
  • the ferrite and the plates have the same size in the horizontal plane or different shapes.
  • the dispersive ferrite 1 comprises an orifice 8 allowing the passage of an exciter 6 connected to a connector 7.
  • the connector 7 is a coaxial type plug, its core is connected to the exciter 6 and its external conductor is connected to the massive.
  • the radiating part and the ground plane are not directly connected by a conductive element such as a short circuit, the antenna thus formed being a monopole antenna.
  • the antenna comprises means for local modification of the magnetic characteristics of the dispersive ferrite, here a magnet 5 arranged on one of the metal plates, preferably the radiating part as shown in this embodiment.
  • a magnet 5 arranged on one of the metal plates, preferably the radiating part as shown in this embodiment.
  • magnet 5 has a rectangular shape. It has a length of 47mm, a width of 22mm and a height of 12mm.
  • the substrate consists of a tile of ferrite material referenced 4S60.
  • the tile is square in shape. It is 100mm long, 100mm wide and 7mm thick.
  • the magnet 5 has a surface corresponding to approximately 10.34% of the total surface of the substrate. Such proportions ensure in particular a local and gradual modification of the magnetic characteristics of the dispersive ferrite by the magnet.
  • the distance between the radiating part and the ground plane, corresponding to the thickness of the ferrite, is generally between ⁇ /50,000 and ⁇ /500 depending on the frequency used.
  • the picture 2 schematically shows in exploded perspective an antenna according to a second embodiment of the invention.
  • the figure 5 represented schematically in side section an antenna according to the second embodiment of the invention.
  • the second embodiment is identical to the first embodiment of the invention, except for the presence of a short-circuit 2 connecting the radiating part to the ground plane, the short-circuit 2 being remote from the exciter 6 so to form an antenna of the semi-open type (or semi-open loop) thanks to the absence of short-circuit at the level of zone 3 opposite to short-circuit 2.
  • the figure 4 schematically shows in side section an antenna according to a third embodiment of the invention.
  • This embodiment is similar to the second embodiment in which the exciter 6 is no longer arranged in the center of the ferrite and crossing the latter, but on a contour of the ferrite so as to extend between the ground plane 4 B and the radiating part 4 H , at the level of the opening of the second embodiment.
  • the exciter 6, the radiating part 4 H , the short circuit 2 and the ground plane 4 B thus form a loop, the antenna thus being a loop type antenna.
  • the figure 6 is a magnetic field map showing the distribution of the radiofrequency magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention without a magnet
  • the figure 7 is a magnetic field map representing the distribution of the radio frequency magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention with magnet. Radio frequency magnetic fields are measured in dB ⁇ A/m.
  • the figure 8 is a magnetic field map representing the distribution of the static magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention with magnet.
  • the static magnetic field is expressed in gauss (G).
  • magnet 5 is a permanent magnet emitting a static field of 2000 G, or 0.2 Tesla (T).
  • the magnet 5 is advantageously arranged eccentric with respect to the exciter 6.
  • the magnet 5 adjoins one of the sides of the ferrite substrate 1.
  • the magnet 5 is preferably arranged in one of the four zones 51, 52, 53, 54, as illustrated in the figure 26 .
  • the magnet 5 is preferably arranged at the level of the zone which forms the opening (reference 3 figure 2 and 5 ). In this case, the magnet 5 is arranged in an off-centre zone 50, opposite the short-circuit 2 as illustrated in the figure 27 .
  • the magnet 5 covers about 10.34% of the surface of the substrate 1.
  • the magnet 5 can also cover the entire surface of the ferrite, in which case the radiation pattern is not modified but the antenna has better radiation efficiency.
  • the dispersive ferrite without local modification of the characteristics makes it possible to stabilize the variation of the impedance of the antenna and thus increase the bandwidth of the antenna, but causes a drop in the radiation efficiency.
  • the local modification of the characteristics makes it possible to retain this advantage of stabilization of the variation in impedance and of increase in passband while compensating for the drop in the radiation efficiency so as to obtain a high-performance antenna.
  • the figure 9 is a graph representing on a logarithmic scale the magnetic losses, represented by the tangent of magnetic losses in the dispersive ferrite of an antenna according to an embodiment of the invention, as a function of the frequency (in MHz on a logarithmic scale) , in the absence (0 G curve) or in the presence of magnets with different magnetic induction values (620 G, 1680 G and 2410G).
  • the figures 10a and 10b are graphs representing respectively the real part and the imaginary part of the relative magnetic permeability in the dispersive ferrite of an antenna according to an embodiment of the invention as a function of the frequency (in MHz on a logarithmic scale), in l absence (0 G curve) or in the presence of magnets with different magnetic induction values (620 G, 1680 G and 2410 G).
  • the experimental results presented on the diagrams of the figure 9 and 10 were obtained with a NiZn ferrite, commercially available under reference 4S60 and commonly used for its radio wave attenuation properties at frequencies above 1 GHz.
  • the real and imaginary parts of the relative magnetic permeability are commonly denoted by the symbols n' and ⁇ ", respectively.
  • the magnetic loss tangent (often denoted by the symbol tan ⁇ ) is the ratio of the imaginary part to the real part of the relative magnetic permeability.
  • the magnetic loss tangent and the real and imaginary parts of the relative magnetic permeability are measured in the dispersive ferrite at areas where the magnetic characteristics of the dispersive ferrite are changed.
  • the reduction in the relative magnetic permeability is particularly visible in the frequencies between 1 and 30 MHz, which is part of the frequency band targeted by the invention. Above 100 MHz, the relative magnetic permeability is low in all cases.
  • Dispersive spinel ferrites in particular NiZn, known to have high magnetic permeability, are generally used to form coatings intended to absorb electromagnetic waves, in particular the walls of anechoic chambers operating at frequencies up to 1000 MHz. In the context of the present invention, this type of ferrite is advantageously used.
  • FIGS. 11a , 11b and 11c schematically represent from above antennas according to different embodiments of the invention, comprising a permanent magnet.
  • the shape of the magnets can be modified, thus resulting in a different distribution of the generated magnetic field. This different distribution leads to a modification of the radiation pattern of the antenna which can therefore be adapted according to requirements.
  • the shapes shown as examples are rectangular ( picture 11a ), circular ( figure 11b ) or triangular ( figure 11c ).
  • the figure 12 schematically represents from above an antenna according to one embodiment of the invention, comprising an electromagnet 5.
  • the electromagnet can replace a permanent magnet in the various embodiments of the antenna.
  • the electromagnet is powered by a variable current generator 9, thus making it possible to modify the value of the magnetic field that it generates. It is thus possible to influence performance such as the S-parameters of the antenna, the gain and the shape of the radiation pattern.
  • the figure 13 is a graph representing the reflection coefficient S 11 of an antenna according to the first embodiment of the invention in the absence (0 G curve) or in the presence of magnets having different magnetic induction values (780 G, 850 G, 1430 G), for example of an electromagnet, depending on the frequency (in MHz).
  • the reflection coefficient S 11 makes it possible to determine the impedance adaptation of the antenna. Using the appropriate magnet or by adjustment with an electromagnet, it is thus possible to choose the value of the magnetic field so as to have the desired impedance adaptation, for example 50 ⁇ .
  • the figure 14 is a graph representing the reflection coefficient S 11 of an antenna according to the first embodiment of the invention in the absence (curve SA for "without magnet”) or in the presence (curve AA for "with magnet”) of a 2000 G permanent magnet, depending on the frequency (in MHz).
  • the antenna here is of the monopole type.
  • the figure 15 is a graph representing the reflection coefficient S 11 of an antenna according to the second embodiment of the invention in the absence (curve SA) or in the presence (curve AA) of a 2000 G permanent magnet, as a function the frequency (in MHz).
  • the antenna here is of the semi-open type.
  • the figure 16 is a radiation pattern of an antenna according to the first embodiment of the invention in the absence (curve SA) or in the presence (curve AA) of a 2000 G permanent magnet.
  • the antenna without magnet is a low gain omnidirectional antenna, while the monopole type antenna with a magnet according to the invention is directional and has a greater gain in all directions.
  • figure 17 is a radiation pattern of an antenna according to the second embodiment of the invention in the absence (curve SA) or in the presence (curve AA) of a 2000 G permanent magnet.
  • the magnetless antenna is a low gain directional antenna, while the semi-open antenna with a magnet according to the invention has a substantially similar pattern but has greater gain in all directions.
  • the radiation pattern of the antenna as shown in figures 16 and 17 can also be adjusted according to the relative position of the magnet 5 with respect to the substrate 1.
  • the figures 18a, 18b and 18c are schematic top views of the dispersive ferrite of antennas according to various embodiments of the invention, comprising an insert.
  • the inserted pieces 10 are pieces of material having a low relative magnetic permeability and low magnetic losses inserted into the dispersive ferrite and which cause a gradual and local reduction in the magnetic permeability and the magnetic losses of the dispersive ferrite.
  • Low relative magnetic permeability means relative magnetic permeability values less than 10.
  • Low magnetic losses means magnetic loss tangent values less than 0.1. As indicated above, these values are to be considered at the working frequency of the antenna, that is to say at a frequency included in a frequency band on which the impedance matching of the antenna is carried out .
  • the inserted part or parts 10 can take the place of the magnet (permanent or electromagnet) in all the embodiments of the antenna described previously. Like the magnet, they can take different forms such as those presented on the figures 18a, 18b and 18c .
  • the figures are similar to figures 11a, 11b and 11c but the parts 10 are here inserted into the dispersive ferrite 1 instead of being arranged above on a metal plate (like the magnet).
  • the hatched areas shown may be composed of a single part inserted in a block or of several inserted parts arranged side by side. Different inserts can have different permeabilities and/or loss tangents (always lower than dispersive Ferrite 1).
  • the shapes can act on the characteristics of the antenna, in particular its directivity.
  • the figure 19 schematically represents in perspective a so-called stacked antenna according to a fourth embodiment of the invention.
  • a stacked antenna according to the invention comprises several dispersive ferrites and several magnets stacked between the ground plane and at least one metal plate of the radiating part.
  • the radiating part 4H is formed of several metal plates connected in S or in zigzag, between which there is alternately a dispersive ferrite or a magnet, so that there is as much dispersive ferrites than magnets.
  • the antenna comprises two dispersive ferrites 11 and 12 and two permanent magnets 51 and 52.
  • the radiating 4 H part is connected to plane 4 B by a short circuit 2.
  • the exciter 6 passes through all the ferrites and magnets and touches only the upper plate of the radiating 4 H part.
  • the figure 20 schematically represents in perspective a so-called stacked antenna according to a fifth embodiment of the invention.
  • the antenna of this embodiment is identical to the fourth embodiment of realization, except that the exciter is offset in place of the short circuit and feeds the antenna between the ground plane 4 B and the plate of the 4 H part which is closest to the ground plane 4 b .
  • the figure 21 schematically represents in perspective a so-called stacked antenna according to a sixth embodiment of the invention.
  • the antenna of this embodiment is identical to the fourth embodiment, except that it does not include short circuit 2.
  • the figure 22 schematically represents in perspective a so-called stacked antenna according to a seventh embodiment of the invention.
  • the antenna comprises a single metal plate forming the radiating 4 H part, and between the radiating 4 H part and the ground plane 4 B there is a stack of dispersive ferrites and alternating magnets, here two dispersive ferrites 11 and 12 and two permanent magnets 51 and 52.
  • the figure 23 schematically represents in perspective a so-called stacked antenna according to an eighth embodiment of the invention.
  • the antenna comprises several metal plates 4 H1 , 4 H2 , 4 H3 and 4 H4 forming the radiating part. Each metal plate is connected to the exciter 6. Between the ground plane 4 B and the plate 4 H4 is a dispersive ferrite 1 2 , between the plate 4 H4 and the plate 4 H3 is a magnet 5 2 , between the plate 4 H3 and plate 4 H2 is a dispersive ferrite 11 and between plate 4 H2 and plate 4 H1 is a magnet 51 .
  • the figure 24 schematically shows in perspective a so-called stacked antenna according to a ninth embodiment of the invention.
  • the antenna of this embodiment is similar to the eighth embodiment, in that it contains a plurality of metal plates 4 H1 , 4 H2 , 4 H3 , 4 H4 , 4 H5 , 4 H6 , 4 H7 and 4 H8 of circular shape, forming the radiating part and connected to the exciter 6. Between the metal plates there are alternately a dispersive ferrite 1 1 , 1 2 , 1 3 or 1 4 of circular shape or a magnet 5 1 , 5 2 , 5 3 or 5 4 in circular shape.
  • the figure 25 schematically shows in perspective a so-called stacked antenna according to a ninth embodiment of the invention.
  • the antenna of this embodiment is similar to the first embodiment of embodiment in that it comprises a magnet arranged on the radiating part 4H of the antenna, the latter being separated from the ground plane 4B by the dispersive ferrite substrate 1.
  • the second plate forming the radiating part 4H is cut so as to form a rectangular flat spiral.
  • this spiral is centered on the exciter 6 of the antenna.
  • dispersive ferrites, magnets, inserts or metal plates can take different shapes.
  • the magnets may have different values from those shown in the graphs.
  • Stacked antennas can contain more layers.

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Description

1. Domaine technique de l'invention1. Technical field of the invention

L'invention concerne une antenne à substrat ferromagnétique. En particulier, l'invention concerne une antenne à substrat ferromagnétique ultracompacte dans le plan vertical comparée à la longueur d'onde, pouvant être utilisées en réception ou en émission dans les bandes de fréquences kilométriques (30-300 kHz), hectométriques (0,3-3 MHz), décamétriques (3-30 MHz) et métriques (30-300 MHz).The invention relates to an antenna with a ferromagnetic substrate. In particular, the invention relates to a ferromagnetic substrate antenna which is ultra-compact in the vertical plane compared to the wavelength, which can be used in reception or in transmission in the kilometric (30-300 kHz), hectometric (0, 3-3 MHz), decametric (3-30 MHz) and metric (30-300 MHz).

L'antenne est particulièrement adaptée par exemple dans les systèmes d'émission large bande ou bande étroite à moyenne et forte puissance véhiculant l'information sous forme de signaux modulés ou non et qui se propagent par voie hertzienne. Selon certains modes de réalisations, l'antenne favorise la propagation de l'onde dans une direction privilégiée (antenne directive).The antenna is particularly suitable, for example, in medium- and high-power wideband or narrowband transmission systems conveying the information in the form of modulated or unmodulated signals and which propagate over the airwaves. According to certain embodiments, the antenna favors the propagation of the wave in a privileged direction (directional antenna).

2. Arrière-plan technologique2. Technological background

Les antennes électriquement petites ont une impédance présentant une forte composante réactive qui ne permet par leur utilisation d'une manière efficace et directe dans des systèmes à impédance réelle normalisée (typiquement 50 Ω).The electrically small antennas have an impedance presenting a strong reactive component which does not allow their use in an efficient and direct manner in systems with normalized real impedance (typically 50 Ω).

L'adaptation d'impédance de ce type d'antenne est souvent difficile et permet généralement l'accord uniquement sur une bande de fréquences étroite. La bande passante étroite d'une telle antenne est souvent instable ce qui est particulièrement problématique à l'émission, en particulier pour les applications de forte puissance.The impedance matching of this type of antenna is often difficult and generally allows tuning only over a narrow frequency band. The narrow bandwidth of such an antenna is often unstable, which is particularly problematic on transmission, in particular for high-power applications.

Des solutions ont été cherchées pour stabiliser cette variation de l'impédance et ainsi augmenter la bande passante de l'antenne. Toutefois, ces solutions diminuent de manière importante l'efficacité de rayonnement de l'antenne, la rendant ainsi non utilisable dans les conditions souhaitées.Solutions have been sought to stabilize this variation in impedance and thus increase the bandwidth of the antenna. However, these solutions significantly reduce the radiation efficiency of the antenna, thus rendering it unusable under the desired conditions.

Dans l'article intitulé " Magnetic tuning of a microstrip antenna on a ferrite substrate" publié dans Electronic Letters, 9th June 1998, Vol. 24, No. 12, pp. 730-731 (référencé D1 ci-après), D.M. Pozar et V. Sanchez décrivent l'adaptation d'impédance d'une antenne micro-ruban à substrat en ferrite pour des applications à hautes fréquences, i.e. supérieures à 2,8 GHz. Pour cela, il est décrit l'application d'un champ magnétique audit substrat constitué en YIG G-113 de type ferrimagnétique et présentant de faibles pertes à hautes fréquences. Il a été constaté que l'utilisation de ce matériau limite le facteur de miniaturisation de l'antenne.In the article titled " Magnetic tuning of a microstrip antenna on a ferrite substrate" published in Electronic Letters, 9th June 1998, Vol. 24, No. 12, pp. 730-731 (referenced D1 below), DM Pozar and V. Sanchez describe the impedance matching of a ferrite substrate microstrip antenna for high frequency applications, ie above 2.8 GHz. For this, the application of a field is described magnetic to said substrate made of YIG G-113 of the ferrimagnetic type and having low losses at high frequencies. It has been found that the use of this material limits the miniaturization factor of the antenna.

Dans l'article intitulé " Magneto-dielectric properties of doped ferrite based nanosized ceramics over very high frequency range", publié dans Engineering Science and Technology, an International Journal 19 (2016) pp. 911-916, Ashish Saini et al. décrivent un matériau magnéto-diélectrique dont ils cherchent à réduire les pertes diélectriques et magnétiques pour miniaturiser des antennes radar opérant à environ 100 MHz.In the article titled " Magneto-dielectric properties of doped ferrite based nanosized ceramics over very high frequency range", published in Engineering Science and Technology, an International Journal 19 (2016) pp. 911-916, Ashish Saini et al. describe a magneto-dielectric material whose dielectric and magnetic losses they seek to reduce in order to miniaturize radar antennae operating at about 100 MHz.

3. Objectifs de l'invention3. Objects of the invention

L'invention vise à pallier au moins certains des inconvénients des antennes électriquement petites connues.The invention aims to overcome at least some of the drawbacks of known electrically small antennas.

En particulier, l'invention vise à fournir, dans au moins un mode de réalisation de l'invention, une antenne à polarisation verticale ultracompacte dans le plan vertical et large bande qui peut fonctionner à l'émission.In particular, the invention aims to provide, in at least one embodiment of the invention, an ultra-compact vertically polarized antenna in the vertical plane and broadband which can operate on transmission.

L'invention vise aussi à fournir, dans au moins un mode de réalisation, une antenne assurant une bonne efficacité de rayonnement tout en conservant une large bande passante par stabilisation de la variation de l'impédance.The invention also aims to provide, in at least one embodiment, an antenna providing good radiation efficiency while maintaining a wide passband by stabilizing the variation of the impedance.

L'invention vise aussi à fournir, dans au moins un mode de réalisation de l'invention, une antenne directionnelle (ou antenne directive).The invention also aims to provide, in at least one embodiment of the invention, a directional antenna (or directional antenna).

4. Exposé de l'invention4. Disclosure of Invention

Pour ce faire, l'invention concerne une antenne tel que défini dans les revendications annexées.To do this, the invention relates to an antenna as defined in the appended claims.

Par définition, un ferrite dispersif présente de fortes pertes diélectriques et/ou de fortes pertes magnétiques. Le substrat ferromagnétique dispersif utilisé dans le cadre de la présente invention est constitué en particulier de ferrite spinelle qui est bien adapté à la fabrication d'antennes magnétiques à large bande passante et de faible dimension. Une antenne selon l'invention permet donc, grâce à l'utilisation d'un substrat ferromagnétique dispersif (ferrite dispersif) partiellement saturé (c'est-à-dire dont les pertes magnétiques et la perméabilité magnétique relative sont réduites localement et graduellement), d'assurer une bonne efficacité de rayonnement tout en conservant une large bande passante par stabilisation de la variation de l'impédance. En effet, le ferrite dispersif permet cette stabilisation de l'impédance, mais réduit fortement le rayonnement. De plus, le ferrite dispersif peut connaître un échauffement rapide et une dégradation de performances au voisinage du point de Curie lors d'émissions longue durée et forte puissance. La modification graduelle et locale des caractéristiques de du ferrite permet de compenser cette réduction de rayonnement afin d'atteindre un gain convenable, tout en conservant la stabilisation de l'impédance, et avec un échauffement réduit en mode émission.By definition, a dispersive ferrite has high dielectric losses and/or high magnetic losses. The dispersive ferromagnetic substrate used in the context of the present invention consists in particular of spinel ferrite which is well suited to the manufacture of magnetic antennas with a wide bandwidth and of small size. An antenna according to the invention therefore makes it possible, thanks to the use of a dispersive ferromagnetic substrate (dispersive ferrite) partially saturated (that is to say whose magnetic losses and relative magnetic permeability are reduced locally and gradually), to ensure good radiation efficiency while maintaining a wide passband by stabilizing the variation of the impedance. Indeed, the dispersive ferrite allows this stabilization of the impedance, but greatly reduces the radiation. In addition, the dispersive ferrite may experience rapid heating and performance degradation near the Curie point during long-duration and high-power emissions. The gradual and local modification of the characteristics of the ferrite makes it possible to compensate for this reduction in radiation in order to achieve a suitable gain, while preserving the stabilization of the impedance, and with reduced heating in emission mode.

L'antenne ainsi réalisée est une antenne à polarisation verticale ultracompacte dans le plan vertical (hauteur de λ/1400 par exemple à λ=30 MHz) et large bande qui peut fonctionner à l'émission. Les termes « plan vertical » et « plan horizontal » s'entendent en considérant l'antenne dans sa disposition pendant son fonctionnement préférentiel en polarisation verticale, l'antenne pouvant bien entendu avoir une orientation différente lorsqu'elle n'est pas en fonctionnement et/ou lorsque la polarisation souhaitée est différente (notamment horizontale).The antenna thus produced is an ultra-compact vertically polarized antenna in the vertical plane (height of λ/1400 for example at λ=30 MHz) and broadband which can operate on transmission. The terms "vertical plane" and "horizontal plane" are understood by considering the antenna in its arrangement during its preferential operation in vertical polarization, the antenna being able of course to have a different orientation when it is not in operation and /or when the desired polarization is different (in particular horizontal).

Une haute perméabilité magnétique relative est typique des matériaux ferromagnétiques, et est largement supérieure à 1, en particulier comprise entre 10 et 10000. La haute tangente de pertes magnétiques, correspondant à de hautes pertes magnétiques, est souvent désignée par le symbole tan δ dont la valeur est supérieure à 0,1. La tangente de pertes magnétique correspond au rapport de la partie imaginaire sur la partie réelle de la perméabilité magnétique relative. La valeur haute de ces caractéristiques magnétiques dépend de la fréquence utilisée. Ces valeurs sont fournies à la fréquence de travail de l'antenne, c'est-à-dire à une fréquence comprise dans une bande de fréquences sur laquelle l'adaptation d'impédance de l'antenne est effectuée. Dans le cadre de la présente invention, on rappelle que l'antenne est adaptée à recevoir ou émettre à une fréquence comprise dans les bandes de fréquences kilométriques (30-300 kHz), hectométriques (0,3-3 MHz), décamétriques (3-30 MHz) ou métriques (30-300 MHz). Ainsi, la fréquence maximale de travail de l'antenne est de l'ordre de 300 MHz (i.e. correspondant à la borne supérieure de la bande de fréquences métriques 30 - 300 MHz).A high relative magnetic permeability is typical of ferromagnetic materials, and is well above 1, in particular between 10 and 10000. The high tangent of magnetic losses, corresponding to high magnetic losses, is often designated by the symbol tan δ whose value is greater than 0.1. The magnetic loss tangent corresponds to the ratio of the imaginary part to the real part of the relative magnetic permeability. The high value of these magnetic characteristics depends on the frequency used. These values are provided at the working frequency of the antenna, that is to say at a frequency included in a frequency band on which the impedance matching of the antenna is carried out. In the context of the present invention, it is recalled that the antenna is suitable for receiving or transmitting at a frequency comprised in the kilometric (30-300 kHz), hectometric (0.3-3 MHz), decametric (3 -30 MHz) or metric (30-300 MHz). Thus, the maximum working frequency of the antenna is of the order of 300 MHz (ie corresponding to the upper limit of the band of metric frequencies 30-300 MHz).

A ces fréquences, notamment à des fréquences situées en bas de bandes (i.e. 30 kHz, 0,3 MHz ou 30 MHz), la haute perméabilité magnétique relative du ferrite dispersif permet d'augmenter le facteur de miniaturisation de l'antenne. Par exemple, l'antenne illustrée à la figure 1 a une dimension maximale inférieure à 0,03 λ à une fréquence de travail égale à 30 MHz (λ désignant la longueur d'onde correspondante) ou inférieure à 0,01 λ en considérant uniquement les parties métalliques rayonnantes de l'antenne.At these frequencies, in particular at frequencies located at the bottom of the bands (ie 30 kHz, 0.3 MHz or 30 MHz), the high relative magnetic permeability of the dispersive ferrite makes it possible to increase the miniaturization factor of the antenna. For example, the antenna shown in figure 1 has a maximum dimension less than 0.03 λ at a working frequency equal to 30 MHz (λ designating the corresponding wavelength) or less than 0.01 λ considering only the radiating metal parts of the antenna.

Par comparaison, la dimensions maximale de la partie rayonnante de l'antenne de D1 serait limitée à 0,22 λ à cette même fréquence de travail. Une telle limitation provient du fait que seule la permittivité élevée du matériau YIG G-113 participe à la réduction de taille de l'antenne. Au contraire, la perméabilité magnétique et la permittivité relative du ferrite dispersif selon les spécificités de l'invention contribuent toutes deux à augmenter le facteur de miniaturisation de l'antenne et avec la particularité que la contribution de la perméabilité magnétique est plus forte que celle de la permittivité. La modification graduelle et locale permet de réduire localement et graduellement ces valeurs, notamment jusqu'à une perméabilité magnétique relative inférieure à la perméabilité du ferrite, typiquement comprise entre 1 et 100 et toujours supérieure à 1, et une tangente de pertes magnétiques plus faibles. Le ferrite dispersive est ainsi non homogène.By comparison, the maximum dimensions of the radiating part of the antenna of D1 would be limited to 0.22 λ at this same working frequency. Such a limitation comes from the fact that only the high permittivity of the YIG G-113 material contributes to the reduction in size of the antenna. On the contrary, the magnetic permeability and the relative permittivity of the dispersive ferrite according to the specifics of the invention both contribute to increasing the miniaturization factor of the antenna and with the particularity that the contribution of the magnetic permeability is stronger than that of permittivity. The gradual and local modification makes it possible to locally and gradually reduce these values, in particular down to a relative magnetic permeability lower than the permeability of the ferrite, typically between 1 and 100 and always greater than 1, and a tangent of lower magnetic losses. The dispersive ferrite is thus non-homogeneous.

L'antenne présente en outre une directivité dans le plan horizontal, sans nécessiter d'être mise en réseau avec d'autres antennes ni avoir recours à un ou des éléments parasites extérieurs.The antenna also has a directivity in the horizontal plane, without needing to be networked with other antennas or having recourse to one or more external parasitic elements.

Le métal non ferreux formant les plaques est par exemple du cuivre, du laiton, de l'aluminium, etc.The non-ferrous metal forming the plates is for example copper, brass, aluminum, etc.

Selon les modes de réalisation, les moyens de modification locale des caractéristiques magnétiques du ferrite dispersif sont un aimant (aimant permanent ou électroaimant), ou au moins une pièce de matériau ayant une faible perméabilité magnétique relative et une faible tangente de pertes.According to the embodiments, the means for local modification of the magnetic characteristics of the dispersive ferrite are a magnet (permanent magnet or electromagnet), or at least one piece of material having a low relative magnetic permeability and a low loss tangent.

L'aimant est disposé sur une plaque métallique de l'antenne, de préférence sur la partie rayonnante.The magnet is arranged on a metal plate of the antenna, preferably on the radiating part.

Lorsque l'aimant est un électroaimant, il est alimenté par un générateur de courant continu, de préférence variable, permettant ainsi de modifier la force du champ magnétique généré par l'électroaimant, modifiant ainsi les performances de l'antenne (paramètres S, gain et forme du diagramme de rayonnement). Le gain peut par exemple varier sur commande, ou l'impédance peut être réglée pour atteindre celle souhaitée dans le système auquel l'antenne est connectée, par exemple 50 Ω.When the magnet is an electromagnet, it is powered by a direct current generator, preferably variable, thus making it possible to modify the strength of the magnetic field generated by the electromagnet, thus modifying the performance of the antenna (parameters S, gain and shape of the radiation pattern). The gain can for example be varied on command, or the impedance can be adjusted to achieve that desired in the system to which the antenna is connected, for example 50 Ω.

La ou les pièces de matériau insérées sont incluses à la fabrication du ferrite. L'agencement des pièces peut être configuré pour atteindre des performances désirées.The piece or pieces of material inserted are included in the manufacture of the ferrite. The arrangement of parts can be configured to achieve desired performance.

Avantageusement et selon l'invention, le ferrite dispersive présente un encombrement dans le plan horizontal supérieur à l'encombrement des plaques en métal.Advantageously and according to the invention, the dispersive ferrite has a size in the horizontal plane greater than the size of the metal plates.

Selon cet aspect de l'invention, l'encombrement des ferrites supérieur aux plaques de métal permet l'amélioration de l'efficacité du rayonnement. Si l'antenne est de type monopôle, cette caractéristique permet aussi d'augmenter la directivité. L'encombrement des ferrites peut être supérieur dans une seule direction.According to this aspect of the invention, the larger size of the ferrites than the metal plates improves the efficiency of the radiation. If the antenna is of the monopole type, this characteristic also makes it possible to increase the directivity. The size of the ferrites can be greater in a single direction.

Avantageusement et selon l'invention, l'antenne comprend au moins un court-circuit reliant le plan de masse et la partie rayonnante, en contact avec un contour du ferrite dispersif.Advantageously and according to the invention, the antenna comprises at least one short-circuit connecting the ground plane and the radiating part, in contact with a contour of the dispersive ferrite.

Selon cet aspect de l'invention, une antenne sans court-circuit est une antenne de type monopôle, une antenne présentant un court-circuit est une antenne de type semi-ouvert, et une antenne présentant un court-circuit disposé à l'opposé de l'excitateur au niveau du contour du ferrite dispersif forme une antenne de type boucle.According to this aspect of the invention, an antenna without a short circuit is a monopole type antenna, an antenna having a short circuit is a semi-open type antenna, and an antenna having a short circuit disposed opposite of the exciter at the contour of the dispersive ferrite forms a loop-type antenna.

Avantageusement et selon l'invention, l'antenne comprend une succession de ferrite dispersif et d'aimant empilés alternativement entre la partie rayonnante et le plan de masse.Advantageously and according to the invention, the antenna comprises a succession of dispersive ferrite and magnet stacked alternately between the radiating part and the ground plane.

Selon cet aspect de l'invention, l'antenne forme ainsi une antenne empilée.According to this aspect of the invention, the antenna thus forms a stacked antenna.

Les antennes empilées permettent d'atteindre des gains plus élevés. Il est en outre possible de faire varier le degré de saturation des ferrites dispersifs selon les couches, permettant ainsi une modification de l'adaptation, du gain et du rayonnement.Stacked antennas allow higher gains to be achieved. It is also possible to vary the degree of saturation of the dispersive ferrites according to the layers, thus allowing a modification of the adaptation, of the gain and of the radiation.

Avantageusement et selon ce dernier aspect de l'invention, la partie rayonnante comprend une plaque en métal entre chaque ferrite et aimant.Advantageously and according to this last aspect of the invention, the radiating part comprises a metal plate between each ferrite and magnet.

Avantageusement et selon ce dernier aspect de l'invention, les plaques de métal sont reliées entre elles.Advantageously and according to this last aspect of the invention, the metal plates are interconnected.

L'invention concerne également une antenne caractérisée en combinaison par tout ou partie des caractéristiques mentionnées ci-dessus ou ci-après.The invention also relates to an antenna characterized in combination by all or some of the characteristics mentioned above or below.

5. Liste des figures5. List of Figures

D'autres buts, caractéristiques et avantages de l'invention apparaîtront à la lecture de la description suivante donnée à titre uniquement non limitatif et qui se réfère aux figures annexées dans lesquelles :

  • la figure 1 est une vue schématique en perspective éclatée d'une antenne selon un premier mode de réalisation de l'invention,
  • la figure 2 est une vue schématique en perspective éclatée d'une antenne selon un deuxième mode de réalisation de l'invention,
  • la figure 3 est une vue schématique en coupe latérale d'une antenne selon le premier mode de réalisation de l'invention,
  • la figure 4 est une vue schématique en coupe latérale d'une antenne selon un troisième mode de réalisation de l'invention,
  • la figure 5 est une vue schématique en coupe latérale d'une antenne selon le deuxième mode de réalisation de l'invention,
  • la figure 6 est une cartographie de champ magnétique représentant la distribution du champ magnétique radiofréquence dans le ferrite dispersif d'une antenne vue de dessus selon le premier mode de réalisation de l'invention sans aimant,
  • la figure 7 est une cartographie de champ magnétique représentant la distribution du champ magnétique radiofréquence dans le ferrite dispersif d'une antenne vue de dessus selon le premier mode de réalisation de l'invention avec aimant,
  • la figure 8 est une cartographie de champ magnétique représentant la distribution du champ magnétique statique dans le ferrite dispersif d'une antenne vue de dessus selon le premier mode de réalisation de l'invention avec aimant,
  • la figure 9 est un graphique représentant la tangente de pertes magnétiques dans le ferrite dispersif d'une antenne selon un mode de réalisation de l'invention en fonction de la fréquence, en l'absence ou en présence d'aimants ayant différentes valeurs d'induction magnétique,
  • les figures 10a et 10b sont des graphiques représentant respectivement la partie réelle et la partie imaginaire de la perméabilité magnétique relative dans le ferrite dispersif d'une antenne selon un mode de réalisation de l'invention en fonction de la fréquence, en l'absence ou en présence d'aimants ayant différentes valeurs d'induction magnétique,
  • les figures 11a, 11b et 11c sont des vues schématiques du dessus de le ferrite dispersif d'antennes selon différents modes de réalisation de l'invention, comprenant un aimant,
  • la figure 12 est une vue schématique du dessus d'une antenne selon un mode de réalisation de l'invention, comprenant un électro-aimant,
  • la figure 13 est un graphique représentant le coefficient de réflexion S11 d'une antenne selon le premier mode de réalisation de l'invention en l'absence ou en présence d'aimants ayant différentes valeurs d'induction magnétique,
  • la figure 14 est un graphique représentant le coefficient de réflexion S11 d'une antenne selon le premier mode de réalisation de l'invention en l'absence ou en présence d'un aimant permanent de 2000 gauss (G),
  • la figure 15 est un graphique représentant le coefficient de réflexion S11 d'une antenne selon le deuxième mode de réalisation de l'invention en l'absence ou en présence d'un aimant permanent de 2000 gauss (G),
  • la figure 16 est un diagramme de rayonnement d'une antenne selon le premier mode de réalisation de l'invention en l'absence ou en présence d'un aimant permanent de 2000 gauss (G),
  • la figure 17 est un diagramme de rayonnement d'une antenne selon le deuxième mode de réalisation de l'invention en l'absence ou en présence d'un aimant permanent de 2000 gauss (G),
  • les figures 18a, 18b et 18c sont des vues schématiques du dessus d'antennes selon différents modes de réalisation de l'invention, comprenant une pièce insérée,
  • la figure 19 est une vue schématique en perspective d'une antenne dite empilée selon un quatrième mode de réalisation de l'invention,
  • la figure 20 est une vue schématique en perspective d'une antenne dite empilée selon un cinquième mode de réalisation de l'invention,
  • la figure 21 est une vue schématique en perspective d'une antenne dite empilée selon un sixième mode de réalisation de l'invention,
  • la figure 22 est une vue schématique en perspective d'une antenne dite empilée selon un septième mode de réalisation de l'invention,
  • la figure 23 est une vue schématique en perspective d'une antenne dite empilée selon un huitième mode de réalisation de l'invention,
  • la figure 24 est une vue schématique en perspective d'une antenne dite empilée selon un neuvième mode de réalisation de l'invention,
  • la figure 25 est une vue schématique en perspective d'une antenne selon un dixième mode de réalisation de l'invention ;
  • la figure 26 illustre des exemples de positionnement de l'aimant sur la partie rayonnante de l'antenne dans le cas d'une antenne monopôle ;
  • la figure 27 illustre un exemple de positionnement de l'aimant sur la partie rayonnante de l'antenne dans le cas d'une antenne semi-ouverte (boucle).
Other aims, characteristics and advantages of the invention will appear on reading the following description given solely by way of non-limiting and which refers to the appended figures in which:
  • the figure 1 is a schematic exploded perspective view of an antenna according to a first embodiment of the invention,
  • the figure 2 is a schematic exploded perspective view of an antenna according to a second embodiment of the invention,
  • the picture 3 is a schematic side sectional view of an antenna according to the first embodiment of the invention,
  • the figure 4 is a schematic side sectional view of an antenna according to a third embodiment of the invention,
  • the figure 5 is a schematic side sectional view of an antenna according to the second embodiment of the invention,
  • the figure 6 is a magnetic field map representing the distribution of the radiofrequency magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention without a magnet,
  • the figure 7 is a magnetic field map representing the distribution of the radiofrequency magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention with magnet,
  • the figure 8 is a magnetic field map representing the distribution of the static magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention with magnet,
  • the figure 9 is a graph representing the tangent of magnetic losses in the dispersive ferrite of an antenna according to an embodiment of the invention as a function of frequency, in the absence or in the presence of magnets having different magnetic induction values,
  • them figures 10a and 10b are graphs representing respectively the real part and the imaginary part of the relative magnetic permeability in the dispersive ferrite of an antenna according to an embodiment of the invention as a function of the frequency, in the absence or in the presence of magnets having different values of magnetic induction,
  • them Figures 11a , 11b and 11c are schematic views from above of the dispersive ferrite of antennas according to different embodiments of the invention, comprising a magnet,
  • the figure 12 is a schematic top view of an antenna according to one embodiment of the invention, comprising an electromagnet,
  • the figure 13 is a graph representing the reflection coefficient S 11 of an antenna according to the first embodiment of the invention in the absence or in the presence of magnets having different magnetic induction values,
  • the figure 14 is a graph representing the reflection coefficient S 11 of an antenna according to the first embodiment of the invention in the absence or in the presence of a permanent magnet of 2000 gauss (G),
  • the figure 15 is a graph representing the reflection coefficient S 11 of an antenna according to the second embodiment of the invention in the absence or in the presence of a permanent magnet of 2000 gauss (G),
  • the figure 16 is a radiation diagram of an antenna according to the first embodiment of the invention in the absence or in the presence of a permanent magnet of 2000 gauss (G),
  • the figure 17 is a radiation diagram of an antenna according to the second embodiment of the invention in the absence or in the presence of a permanent magnet of 2000 gauss (G),
  • them figures 18a, 18b and 18c are schematic top views of antennas according to different embodiments of the invention, comprising an inserted part,
  • the figure 19 is a schematic perspective view of a so-called stacked antenna according to a fourth embodiment of the invention,
  • the figure 20 is a schematic perspective view of a so-called stacked antenna according to a fifth embodiment of the invention,
  • the figure 21 is a schematic perspective view of a so-called stacked antenna according to a sixth embodiment of the invention,
  • the figure 22 is a schematic perspective view of a so-called stacked antenna according to a seventh embodiment of the invention,
  • the figure 23 is a schematic perspective view of a so-called stacked antenna according to an eighth embodiment of the invention,
  • the figure 24 is a schematic perspective view of a so-called stacked antenna according to a ninth embodiment of the invention,
  • the figure 25 is a schematic perspective view of an antenna according to a tenth embodiment of the invention;
  • the figure 26 illustrates examples of positioning the magnet on the radiating part of the antenna in the case of a monopole antenna;
  • the figure 27 illustrates an example of positioning the magnet on the radiating part of the antenna in the case of a semi-open antenna (loop).

6. Description détaillée d'un mode de réalisation de l'invention6. Detailed description of an embodiment of the invention

Les réalisations suivantes sont des exemples. Bien que la description se réfère à un ou plusieurs modes de réalisation, ceci ne signifie pas nécessairement que chaque référence concerne le même mode de réalisation, ou que les caractéristiques s'appliquent seulement à un seul mode de réalisation. De simples caractéristiques de différents modes de réalisation peuvent également être combinées pour fournir d'autres réalisations. Sur les figures, les échelles et les proportions ne sont pas strictement respectées et ce, à des fins d'illustration et de clarté.The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference is to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined to provide other realizations. In the figures, scales and proportions are not strictly adhered to, for purposes of illustration and clarity.

Les valeurs de l'induction magnétique des aimants est exprimé en gauss dans cette demande, 1 gauss (de symbole G) valant 10-4 tesla (de symbole T).The values of the magnetic induction of the magnets are expressed in gauss in this application, 1 gauss (of symbol G) equaling 10 -4 tesla (of symbol T).

Les antennes représentées sont disposées selon leur mode de fonctionnement préférentiel avec une polarisation verticale. λ désigne la longueur d'onde à la fréquence principale (fréquence centrale si émission sur une bande de fréquence) d'émission ou de réception de l'antenne.The antennas shown are arranged according to their preferred mode of operation with vertical polarization. λ designates the wavelength at the main frequency (central frequency if emission on a frequency band) of emission or reception of the antenna.

La figure 1 représente schématiquement en perspective éclatée une antenne selon un premier mode de réalisation de l'invention. La figure 3 représente schématiquement en coupe latérale une antenne selon le premier mode de réalisation de l'invention.The figure 1 schematically represents in exploded perspective an antenna according to a first embodiment of the invention. The picture 3 schematically shows in side section an antenna according to the first embodiment of the invention.

L'antenne comprend deux plaques en métal non ferreux (par exemple cuivre, laiton, aluminium, etc.), une première plaque formant une partie 4H rayonnante et une deuxième plaque formant un plan 4B de masse. Entre les deux plaques en métal est disposé un substrat ferromagnétique dispersif, dit ferrite 1 dispersif. Les plaques en métal et le ferrite 1 dispersif se présentent sous une forme plate s'étendant principalement selon un plan horizontal, de sorte à présenter un encombrement vertical minimal pour une antenne à polarisation verticale.The antenna comprises two non-ferrous metal plates (for example copper, brass, aluminium, etc.), a first plate forming a radiating part 4 H and a second plate forming a ground plane 4 B. Between the two metal plates is placed a dispersive ferromagnetic substrate, called dispersive ferrite 1. The metal plates and the dispersive ferrite 1 are in a flat shape extending mainly along a horizontal plane, so as to present a minimum vertical bulk for an antenna with vertical polarization.

La partie 4H rayonnante recouvre totalement ou partiellement le ferrite 1 dispersif, et peut être composée de plusieurs pièces ayant des formes différentes reliées entre elles. La partie 4H rayonnante peut aussi se présenter sous plusieurs formes complexes, par exemple un méandre comme représenté en référence avec la figure 25 selon un mode de réalisation de l'invention.The radiating part 4 H totally or partially covers the dispersive ferrite 1, and can be composed of several parts having different shapes connected together. The radiant 4 H part can also come in several forms complex, for example a meander as shown with reference to the figure 25 according to one embodiment of the invention.

Dans ce mode de réalisation, le ferrite 1 dispersif présente un encombrement horizontal supérieur aux plaques en métal, notamment selon une longueur (les plaques sont carrées tandis que le ferrite 1 dispersif est rectangulaire), ce qui permet une amélioration du rayonnement (gain supérieur). Selon d'autres modes de réalisation, le ferrite et les plaques ont le même encombrement dans le plan horizontal ou des formes différentes.In this embodiment, the dispersive ferrite 1 has a greater horizontal bulk than the metal plates, in particular along a length (the plates are square while the dispersive ferrite 1 is rectangular), which allows an improvement in radiation (higher gain) . According to other embodiments, the ferrite and the plates have the same size in the horizontal plane or different shapes.

Le ferrite 1 dispersif comprend un orifice 8 permettant la traversée d'un excitateur 6 relié à un connecteur 7. Lorsque le connecteur 7 est une prise de type coaxiale, son âme est reliée à l'excitateur 6 et son conducteur extérieur est relié au plan de masse. La partie rayonnante et le plan de masse ne sont pas directement reliés par un élément conducteur tel qu'un court-circuit, l'antenne ainsi formée étant une antenne monopôle.The dispersive ferrite 1 comprises an orifice 8 allowing the passage of an exciter 6 connected to a connector 7. When the connector 7 is a coaxial type plug, its core is connected to the exciter 6 and its external conductor is connected to the massive. The radiating part and the ground plane are not directly connected by a conductive element such as a short circuit, the antenna thus formed being a monopole antenna.

L'antenne comprend des moyens de modification locale des caractéristiques magnétiques du ferrite dispersif, ici un aimant 5 disposé sur une des plaques en métal, de préférence la partie rayonnante comme représenté dans ce mode de réalisation. En disposant l'aimant 5 sur la partie rayonnante de l'antenne, il est possible d'atteindre un rendement d'antenne plus élevé avec un gain plus élevé dans une direction donnée.The antenna comprises means for local modification of the magnetic characteristics of the dispersive ferrite, here a magnet 5 arranged on one of the metal plates, preferably the radiating part as shown in this embodiment. By arranging the magnet 5 on the radiating part of the antenna, it is possible to achieve a higher antenna efficiency with a higher gain in a given direction.

Par exemple, l'aimant 5 a une forme rectangulaire. Il a une longueur de 47 mm, une largeur de 22 mm et une hauteur de 12 mm. Le substrat est constitué par une tuile de ferrite en matériau référencé 4S60. La tuile est de forme carrée. Elle a une longueur de 100 mm, une largeur de 100 mm et une épaisseur de 7 mm. Ainsi, l'aimant 5 a une surface correspondant à environ 10,34 % de la surface totale du substrat. De telles proportions assurent notamment une modification locale et graduelle des caractéristiques magnétiques du ferrite dispersif par l'aimant.For example, magnet 5 has a rectangular shape. It has a length of 47mm, a width of 22mm and a height of 12mm. The substrate consists of a tile of ferrite material referenced 4S60. The tile is square in shape. It is 100mm long, 100mm wide and 7mm thick. Thus, the magnet 5 has a surface corresponding to approximately 10.34% of the total surface of the substrate. Such proportions ensure in particular a local and gradual modification of the magnetic characteristics of the dispersive ferrite by the magnet.

La distance entre la partie rayonnante et le plan de masse, correspondant à l'épaisseur du ferrite, est généralement comprise entre λ/50 000 et À/500 selon la fréquence utilisée.The distance between the radiating part and the ground plane, corresponding to the thickness of the ferrite, is generally between λ/50,000 and λ/500 depending on the frequency used.

La figure 2 représente schématiquement en perspective éclatée une antenne selon un deuxième mode de réalisation de l'invention. La figure 5 représente schématiquement en coupe latérale une antenne selon le deuxième mode de réalisation de l'invention.The picture 2 schematically shows in exploded perspective an antenna according to a second embodiment of the invention. The figure 5 represented schematically in side section an antenna according to the second embodiment of the invention.

Le deuxième mode de réalisation est identique au premier mode de réalisation de l'invention, excepté la présence d'un court-circuit 2 reliant la partie rayonnante au plan de masse, le court-circuit 2 étant éloigné de l'excitateur 6 de sorte à former une antenne de type semi-ouverte (ou boucle semi-ouverte) grâce à l'absence de court-circuit au niveau de la zone 3 opposée au court-circuit 2.The second embodiment is identical to the first embodiment of the invention, except for the presence of a short-circuit 2 connecting the radiating part to the ground plane, the short-circuit 2 being remote from the exciter 6 so to form an antenna of the semi-open type (or semi-open loop) thanks to the absence of short-circuit at the level of zone 3 opposite to short-circuit 2.

La figure 4 représente schématiquement en coupe latérale une antenne selon un troisième mode de réalisation de l'invention.The figure 4 schematically shows in side section an antenna according to a third embodiment of the invention.

Ce mode de réalisation est similaire au deuxième mode de réalisation dans lequel l'excitateur 6 est disposé non plus au centre du ferrite et traversant celle-ci, mais sur un contour du ferrite de sorte à s'étendre entre le plan 4B de masse et la partie rayonnante 4H, au niveau de l'ouverture du deuxième mode de réalisation. L'excitateur 6, la partie rayonnante 4H, le court-circuit 2 et le plan 4B de masse forment ainsi une boucle, l'antenne étant ainsi une antenne de type boucle.This embodiment is similar to the second embodiment in which the exciter 6 is no longer arranged in the center of the ferrite and crossing the latter, but on a contour of the ferrite so as to extend between the ground plane 4 B and the radiating part 4 H , at the level of the opening of the second embodiment. The exciter 6, the radiating part 4 H , the short circuit 2 and the ground plane 4 B thus form a loop, the antenna thus being a loop type antenna.

La figure 6 est une cartographie de champ magnétique représentant la distribution du champ magnétique radiofréquence dans le ferrite dispersif d'une antenne vue de dessus selon le premier mode de réalisation de l'invention sans aimant, et la figure 7 est une cartographie de champ magnétique représentant la distribution du champ magnétique radiofréquence dans le ferrite dispersif d'une antenne vue de dessus selon le premier mode de réalisation de l'invention avec aimant. Les champs magnétiques radiofréquence sont mesurés en dBµA/m. La figure 8 est une cartographie de champ magnétique représentant la distribution du champ magnétique statique dans le ferrite dispersif d'une antenne vue de dessus selon le premier mode de réalisation de l'invention avec aimant. Le champ magnétique statique est exprimé en gauss (G). Par exemple, l'aimant 5 est un aimant permanent émettant un champ statique de 2000 G, soit 0.2 Tesla (T).The figure 6 is a magnetic field map showing the distribution of the radiofrequency magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention without a magnet, and the figure 7 is a magnetic field map representing the distribution of the radio frequency magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention with magnet. Radio frequency magnetic fields are measured in dBµA/m. The figure 8 is a magnetic field map representing the distribution of the static magnetic field in the dispersive ferrite of an antenna seen from above according to the first embodiment of the invention with magnet. The static magnetic field is expressed in gauss (G). For example, magnet 5 is a permanent magnet emitting a static field of 2000 G, or 0.2 Tesla (T).

On remarque sur la figure 7 l'introduction d'une dissymétrie en amplitude due à l'inhomogénéité du champ statique de commande généré par l'aimant (représenté sur la figure 8). Ce champ statique généré par l'aimant provoque une modification locale des caractéristiques du ferrite dispersif. En particulier, cette modification est une réduction locale et graduelle de la perméabilité magnétique relative et des pertes magnétiques du ferrite dispersif. D'un point de vue du fonctionnement de l'antenne, cela se traduit par une dissymétrie dans le diagramme de rayonnement ce qui conduit à une augmentation de la directivité de l'antenne, comme visible par exemple sur la figure 16. En complément, comme la perméabilité magnétique relative et les pertes du ferrite sont réduites (voir figure 9), le gain est augmenté d'une manière très favorable.We notice on the figure 7 the introduction of an amplitude asymmetry due to the inhomogeneity of the static control field generated by the magnet (represented on the figure 8 ). This static field generated by the magnet causes a local modification characteristics of dispersive ferrite. In particular, this modification is a local and gradual reduction of the relative magnetic permeability and of the magnetic losses of the dispersive ferrite. From an antenna operation point of view, this results in an asymmetry in the radiation pattern which leads to an increase in the directivity of the antenna, as visible for example on the figure 16 . In addition, as the relative magnetic permeability and ferrite losses are reduced (see figure 9 ), the gain is increased in a very favorable way.

Pour former cette dissymétrie, l'aimant 5 est avantageusement disposé excentré par rapport à l'excitateur 6. De préférence, l'aimant 5 jouxte un des côtés du substrat de ferrite 1.Par exemple, lorsque l'antenne est de type monopôle, l'aimant 5 est de préférence disposé dans l'une des quatre zones 51, 52, 53, 54, comme illustré sur la figure 26 . Lorsque l'antenne est de type semi-ouverte, l'aimant 5 est de préférence disposé au niveau de la zone qui forme l'ouverture (référence 3 figures 2 et 5). Dans ce cas, l'aimant 5 est disposé dans une zone excentrée 50, à l'opposé du court-circuit 2 comme illustré sur la figure 27 . To form this asymmetry, the magnet 5 is advantageously arranged eccentric with respect to the exciter 6. Preferably, the magnet 5 adjoins one of the sides of the ferrite substrate 1. For example, when the antenna is of the monopole type, the magnet 5 is preferably arranged in one of the four zones 51, 52, 53, 54, as illustrated in the figure 26 . When the antenna is of the semi-open type, the magnet 5 is preferably arranged at the level of the zone which forms the opening (reference 3 figure 2 and 5 ). In this case, the magnet 5 is arranged in an off-centre zone 50, opposite the short-circuit 2 as illustrated in the figure 27 .

Dans l'exemple décrit ci-dessus en référence à la figure 1, l'aimant 5 recouvre environ 10,34% de la surface du substrat 1. Toutefois, l'aimant 5 peut aussi recouvrir la totalité de la surface du ferrite, auquel cas le diagramme de rayonnement n'est pas modifié mais l'antenne a une meilleure efficacité de rayonnement.In the example described above with reference to the figure 1 , the magnet 5 covers about 10.34% of the surface of the substrate 1. However, the magnet 5 can also cover the entire surface of the ferrite, in which case the radiation pattern is not modified but the antenna has better radiation efficiency.

Le ferrite dispersif sans modification locale des caractéristiques permet de stabiliser la variation de l'impédance de l'antenne et ainsi augmenter la bande passante de l'antenne, mais entraine une baisse de l'efficacité de rayonnement. La modification locale des caractéristiques permet de conserver cet avantage de stabilisation de la variation d'impédance et d'augmentation de bande passante tout en compensant la baisse de l'efficacité de rayonnement de sorte à obtenir une antenne performante.The dispersive ferrite without local modification of the characteristics makes it possible to stabilize the variation of the impedance of the antenna and thus increase the bandwidth of the antenna, but causes a drop in the radiation efficiency. The local modification of the characteristics makes it possible to retain this advantage of stabilization of the variation in impedance and of increase in passband while compensating for the drop in the radiation efficiency so as to obtain a high-performance antenna.

La figure 9 est un graphique représentant sur une échelle logarithmique les pertes magnétiques, représentées par la tangente de pertes magnétiques dans le ferrite dispersif d'une antenne selon un mode de réalisation de l'invention, en fonction de la fréquence (en MHz sur une échelle logarithmique), en l'absence (courbe 0 G) ou en présence d'aimants ayant différentes valeurs d'induction magnétique (620 G, 1680 G et 2410 G). Les figures 10a et 10b sont des graphiques représentant respectivement la partie réelle et la partie imaginaire de la perméabilité magnétique relative dans le ferrite dispersif d'une antenne selon un mode de réalisation de l'invention en fonction de la fréquence (en MHz sur une échelle logarithmique), en l'absence (courbe 0 G) ou en présence d'aimants ayant différentes valeurs d'induction magnétique (620 G, 1680 G et 2410 G). Les résultats expérimentaux présentés sur les diagrammes des figures 9 et 10 ont été obtenus avec une ferrite NiZn, commercialement disponible sous référence la 4S60 et communément utilisée pour ses propriétés d'atténuation des ondes radio à des fréquences supérieures à 1 GHz.The figure 9 is a graph representing on a logarithmic scale the magnetic losses, represented by the tangent of magnetic losses in the dispersive ferrite of an antenna according to an embodiment of the invention, as a function of the frequency (in MHz on a logarithmic scale) , in the absence (0 G curve) or in the presence of magnets with different magnetic induction values (620 G, 1680 G and 2410G). The figures 10a and 10b are graphs representing respectively the real part and the imaginary part of the relative magnetic permeability in the dispersive ferrite of an antenna according to an embodiment of the invention as a function of the frequency (in MHz on a logarithmic scale), in l absence (0 G curve) or in the presence of magnets with different magnetic induction values (620 G, 1680 G and 2410 G). The experimental results presented on the diagrams of the figure 9 and 10 were obtained with a NiZn ferrite, commercially available under reference 4S60 and commonly used for its radio wave attenuation properties at frequencies above 1 GHz.

Des résultats similaires pourront être obtenus avec d'autres ferrites dispersifs, notamment des ferrites spinelles, présentant à la fois une forte perméabilité magnétique relative comprise entre 10 et 10000 et une haute tangente de perte magnétique supérieure à 0,1. On rappelle que la perméabilité magnétique relative et la tangente de perte magnétique dépendent non seulement du matériau mais également de la fréquence de travail de l'antenne considérée. Dans le cadre de la présente invention, la fréquence de travail reste inférieure à 300 MHz.Similar results can be obtained with other dispersive ferrites, in particular spinel ferrites, exhibiting both a high relative magnetic permeability of between 10 and 10,000 and a high magnetic loss tangent greater than 0.1. It is recalled that the relative magnetic permeability and the magnetic loss tangent depend not only on the material but also on the working frequency of the antenna considered. In the context of the present invention, the working frequency remains below 300 MHz.

Les parties réelles et imaginaires de la perméabilité magnétique relative sont communément désignées respectivement par les symboles n' et µ".The real and imaginary parts of the relative magnetic permeability are commonly denoted by the symbols n' and µ", respectively.

La tangente de pertes magnétiques (souvent désignée par le symbole tan δ) est le rapport de la partie imaginaire sur la partie réelle de la perméabilité magnétique relative.The magnetic loss tangent (often denoted by the symbol tan δ) is the ratio of the imaginary part to the real part of the relative magnetic permeability.

La tangente de pertes magnétiques et les parties réelles et imaginaires de la perméabilité magnétique relative sont mesurées dans le ferrite dispersif au niveau des zones où les caractéristiques magnétiques du ferrite dispersif sont modifiées.The magnetic loss tangent and the real and imaginary parts of the relative magnetic permeability are measured in the dispersive ferrite at areas where the magnetic characteristics of the dispersive ferrite are changed.

Comme visible sur les graphiques, en présence d'un aimant, les pertes magnétiques et la perméabilité magnétique relative diminuent, permettant d'obtenir les effets sur le gain et le rayonnement décrit précédemment. Cette réduction est d'autant plus importante que la valeur de l'induction magnétique de l'aimant est importante.As visible on the graphs, in the presence of a magnet, the magnetic losses and the relative magnetic permeability decrease, making it possible to obtain the effects on the gain and the radiation described previously. This reduction is all the more important as the value of the magnetic induction of the magnet is important.

Sur les graphiques des figures 10a et 10b , la réduction de la perméabilité magnétique relative est particulièrement visible dans les fréquences entre 1 et 30 MHz, qui fait partie de la bande de fréquence visée par l'invention. Au-delà de 100 MHz, la perméabilité magnétique relative est faible dans tous les cas.On the graphs of figures 10a and 10b , the reduction in the relative magnetic permeability is particularly visible in the frequencies between 1 and 30 MHz, which is part of the frequency band targeted by the invention. Above 100 MHz, the relative magnetic permeability is low in all cases.

Les ferrites spinelles dispersives, notamment NiZn, connues pour présenter une haute perméabilité magnétique sont généralement utilisées pour former des revêtements destinés à absorber les ondes électromagnétiques, en particulier les parois des chambres anéchoïdes opérant à des fréquences jusqu'à 1000 MHz. Dans le cadre de la présente invention, on utilise avantageusement ce type de ferrite.Dispersive spinel ferrites, in particular NiZn, known to have high magnetic permeability, are generally used to form coatings intended to absorb electromagnetic waves, in particular the walls of anechoic chambers operating at frequencies up to 1000 MHz. In the context of the present invention, this type of ferrite is advantageously used.

Les figures 11a, 11b et 11c représentent schématiquement du dessus des antennes selon différents modes de réalisation de l'invention, comprenant un aimant permanent. La forme des aimants peut être modifiée, entrainant ainsi une distribution différente du champ magnétique généré. Cette distribution différente entraine une modification du diagramme de rayonnement de l'antenne qui peut donc être adapté selon les besoins. Les formes représentées en exemple sont rectangulaires (figure 11a), circulaires (figure 11b) ou triangulaires (figure 11c).The Figures 11a , 11b and 11c schematically represent from above antennas according to different embodiments of the invention, comprising a permanent magnet. The shape of the magnets can be modified, thus resulting in a different distribution of the generated magnetic field. This different distribution leads to a modification of the radiation pattern of the antenna which can therefore be adapted according to requirements. The shapes shown as examples are rectangular ( picture 11a ), circular ( figure 11b ) or triangular ( figure 11c ).

La figure 12 représente schématiquement du dessus une antenne selon un mode de réalisation de l'invention, comprenant un électroaimant 5. L'électroaimant peut remplacer un aimant permanent dans les différents modes de réalisation de l'antenne. L'électroaimant est alimenté par un générateur 9 de courant variable, permettant ainsi de modifier la valeur du champ magnétique qu'il génère. Il est ainsi possible d'influer sur des performances telles que les paramètres S de l'antenne, le gain et la forme du diagramme de rayonnement.The figure 12 schematically represents from above an antenna according to one embodiment of the invention, comprising an electromagnet 5. The electromagnet can replace a permanent magnet in the various embodiments of the antenna. The electromagnet is powered by a variable current generator 9, thus making it possible to modify the value of the magnetic field that it generates. It is thus possible to influence performance such as the S-parameters of the antenna, the gain and the shape of the radiation pattern.

La figure 13 est un graphique représentant le coefficient de réflexion S11 d'une antenne selon le premier mode de réalisation de l'invention en l'absence (courbe 0 G) ou en présence d'aimants ayant différentes valeurs d'induction magnétique (780 G, 850 G, 1430 G), par exemple d'un électro-aimant, en fonction de la fréquence (en MHz). Le coefficient de réflexion S11 permet de déterminer l'adaptation d'impédance de l'antenne. À l'aide de l'aimant adapté ou par réglage avec un électro-aimant, il est ainsi possible de choisir la valeur du champ magnétique de sorte à avoir l'adaptation d'impédance souhaitée, par exemple 50 Ω.The figure 13 is a graph representing the reflection coefficient S 11 of an antenna according to the first embodiment of the invention in the absence (0 G curve) or in the presence of magnets having different magnetic induction values (780 G, 850 G, 1430 G), for example of an electromagnet, depending on the frequency (in MHz). The reflection coefficient S 11 makes it possible to determine the impedance adaptation of the antenna. Using the appropriate magnet or by adjustment with an electromagnet, it is thus possible to choose the value of the magnetic field so as to have the desired impedance adaptation, for example 50 Ω.

La figure 14 est un graphique représentant le coefficient de réflexion S11 d'une antenne selon le premier mode de réalisation de l'invention en l'absence (courbe SA pour « sans aimant ») ou en présence (courbe AA pour « avec aimant ») d'un aimant permanent de 2000 G, en fonction de la fréquence (en MHz). L'antenne est ici de type monopôle.The figure 14 is a graph representing the reflection coefficient S 11 of an antenna according to the first embodiment of the invention in the absence (curve SA for "without magnet") or in the presence (curve AA for "with magnet") of a 2000 G permanent magnet, depending on the frequency (in MHz). The antenna here is of the monopole type.

La figure 15 est un graphique représentant le coefficient de réflexion S11 d'une antenne selon le deuxième mode de réalisation de l'invention en l'absence (courbe SA) ou en présence (courbe AA) d'un aimant permanent de 2000 G, en fonction de la fréquence (en MHz). L'antenne est ici de type semi-ouverte.The figure 15 is a graph representing the reflection coefficient S 11 of an antenna according to the second embodiment of the invention in the absence (curve SA) or in the presence (curve AA) of a 2000 G permanent magnet, as a function the frequency (in MHz). The antenna here is of the semi-open type.

La figure 16 est un diagramme de rayonnement d'une antenne selon le premier mode de réalisation de l'invention en l'absence (courbe SA) ou en présence (courbe AA) d'un aimant permanent de 2000 G.The figure 16 is a radiation pattern of an antenna according to the first embodiment of the invention in the absence (curve SA) or in the presence (curve AA) of a 2000 G permanent magnet.

L'antenne sans aimant est une antenne omnidirectionnelle de faible gain, tandis que l'antenne de type monopôle avec un aimant selon l'invention est directionnelle et a un gain plus important dans toutes les directions.La figure 17 est un diagramme de rayonnement d'une antenne selon le deuxième mode de réalisation de l'invention en l'absence (courbe SA) ou en présence (courbe AA) d'un aimant permanent de 2000 G.The antenna without magnet is a low gain omnidirectional antenna, while the monopole type antenna with a magnet according to the invention is directional and has a greater gain in all directions. figure 17 is a radiation pattern of an antenna according to the second embodiment of the invention in the absence (curve SA) or in the presence (curve AA) of a 2000 G permanent magnet.

L'antenne sans aimant est une antenne directionnelle de faible gain, tandis que l'antenne semi-ouverte avec un aimant selon l'invention a un diagramme sensiblement similaire mais présente un gain plus important dans toutes les directions.The magnetless antenna is a low gain directional antenna, while the semi-open antenna with a magnet according to the invention has a substantially similar pattern but has greater gain in all directions.

De manière générale, le diagramme de rayonnement de l'antenne tel que représenté aux figure 16 et 17 peut être également ajusté en fonction de la position relative de l'aimant 5 par rapport au substrat 1.In general, the radiation pattern of the antenna as shown in figures 16 and 17 can also be adjusted according to the relative position of the magnet 5 with respect to the substrate 1.

Les figures 18a, 18b et 18c sont des vues schématiques du dessus du ferrite dispersif d'antennes selon différents modes de réalisation de l'invention, comprenant une pièce insérée.The figures 18a, 18b and 18c are schematic top views of the dispersive ferrite of antennas according to various embodiments of the invention, comprising an insert.

Les pièces 10 insérées sont des pièces de matériau ayant une faible perméabilité magnétique relative et de faibles pertes magnétiques insérées dans le ferrite dispersif et qui entrainent une réduction graduelle et locale de la perméabilité magnétique et des pertes magnétiques du ferrite dispersif.The inserted pieces 10 are pieces of material having a low relative magnetic permeability and low magnetic losses inserted into the dispersive ferrite and which cause a gradual and local reduction in the magnetic permeability and the magnetic losses of the dispersive ferrite.

Par faible perméabilité magnétique relative, on comprend des valeurs de perméabilité magnétique relative inférieure à 10. Par faibles pertes magnétiques, on comprend des valeurs de tangente de perte magnétique inférieures à 0,1. Comme indiqué ci-avant, ces valeurs sont à considérer à la fréquence de travail de l'antenne, c'est-à-dire à une fréquence comprise dans une bande de fréquences sur laquelle l'adaptation d'impédance de l'antenne est réalisée.Low relative magnetic permeability means relative magnetic permeability values less than 10. Low magnetic losses means magnetic loss tangent values less than 0.1. As indicated above, these values are to be considered at the working frequency of the antenna, that is to say at a frequency included in a frequency band on which the impedance matching of the antenna is carried out .

La ou les pièces 10 insérées peuvent prendre la place de l'aimant (permanent ou électroaimant) dans tous les modes de réalisation de l'antenne décrits précédemment. Comme l'aimant, elles peuvent prendre différentes formes comme par exemple celles présentées sur les figures 18a, 18b et 18c. Les figures sont similaires aux figures 11a, 11b et 11c mais les pièces 10 sont ici insérées dans le ferrite 1 dispersif au lieu d'être disposées au-dessus sur une plaque métallique (comme l'aimant). Les zones hachurées représentées peuvent être composées d'une seule pièce insérée en un bloc ou de plusieurs pièces insérées agencées côte à côte. Différentes pièces insérées peuvent avoir des perméabilités et/ou tangente de pertes différentes (toujours plus faibles que le ferrite 1 dispersif).The inserted part or parts 10 can take the place of the magnet (permanent or electromagnet) in all the embodiments of the antenna described previously. Like the magnet, they can take different forms such as those presented on the figures 18a, 18b and 18c . The figures are similar to figures 11a, 11b and 11c but the parts 10 are here inserted into the dispersive ferrite 1 instead of being arranged above on a metal plate (like the magnet). The hatched areas shown may be composed of a single part inserted in a block or of several inserted parts arranged side by side. Different inserts can have different permeabilities and/or loss tangents (always lower than dispersive Ferrite 1).

Comme pour l'aimant, les formes peuvent agir sur les caractéristiques de l'antenne, notamment sa directivité.As for the magnet, the shapes can act on the characteristics of the antenna, in particular its directivity.

La figure 19 représente schématiquement en perspective une antenne dite empilée selon un quatrième mode de réalisation de l'invention.The figure 19 schematically represents in perspective a so-called stacked antenna according to a fourth embodiment of the invention.

Une antenne empilée selon l'invention comprend plusieurs ferrites dispersifs et plusieurs aimants empilés entre le plan de masse et au moins une plaque en métal de la partie rayonnante.A stacked antenna according to the invention comprises several dispersive ferrites and several magnets stacked between the ground plane and at least one metal plate of the radiating part.

Dans ce quatrième mode de réalisation de l'invention, la partie rayonnante 4H est formée de plusieurs plaques en métal reliées en S ou en zigzag, entre lesquelles se situent alternativement un ferrite dispersif ou un aimant, de sorte qu'il y ait autant de ferrites dispersifs que d'aimants. Par exemple, ici, l'antenne comprend deux ferrites 11 et 12 dispersifs et deux aimants 51 et 52 permanents. La partie 4H rayonnante est reliée au plan 4B par un court-circuit 2. L'excitateur 6 traverse toutes les ferrites et aimants et ne touche que la plaque supérieure de la partie 4H rayonnante.In this fourth embodiment of the invention, the radiating part 4H is formed of several metal plates connected in S or in zigzag, between which there is alternately a dispersive ferrite or a magnet, so that there is as much dispersive ferrites than magnets. For example, here, the antenna comprises two dispersive ferrites 11 and 12 and two permanent magnets 51 and 52. The radiating 4 H part is connected to plane 4 B by a short circuit 2. The exciter 6 passes through all the ferrites and magnets and touches only the upper plate of the radiating 4 H part.

La figure 20 représente schématiquement en perspective une antenne dite empilée selon un cinquième mode de réalisation de l'invention.The figure 20 schematically represents in perspective a so-called stacked antenna according to a fifth embodiment of the invention.

L'antenne de ce mode de réalisation est identique au quatrième mode de réalisation, sauf que l'excitateur est déporté à la place du court-circuit et alimente l'antenne entre le plan 4B de masse et la plaque de la partie 4H qui est la plus proche du plan 4b de masse.The antenna of this embodiment is identical to the fourth embodiment of realization, except that the exciter is offset in place of the short circuit and feeds the antenna between the ground plane 4 B and the plate of the 4 H part which is closest to the ground plane 4 b .

La figure 21 représente schématiquement en perspective une antenne dite empilée selon un sixième mode de réalisation de l'invention.The figure 21 schematically represents in perspective a so-called stacked antenna according to a sixth embodiment of the invention.

L'antenne de ce mode de réalisation est identique au quatrième mode de réalisation, sauf qu'elle ne comprend pas de court-circuit 2.The antenna of this embodiment is identical to the fourth embodiment, except that it does not include short circuit 2.

La figure 22 représente schématiquement en perspective une antenne dite empilée selon un septième mode de réalisation de l'invention.The figure 22 schematically represents in perspective a so-called stacked antenna according to a seventh embodiment of the invention.

Dans ce mode de réalisation, l'antenne comprend une seule plaque de métal formant la partie 4H rayonnante, et entre la partie 4H rayonnante et le plan 4B de masse se trouve un empilement de ferrites dispersifs et d'aimants alternés, ici deux ferrites 11 et 12 dispersifs et deux aimants 51 et 52 permanents.In this embodiment, the antenna comprises a single metal plate forming the radiating 4 H part, and between the radiating 4 H part and the ground plane 4 B there is a stack of dispersive ferrites and alternating magnets, here two dispersive ferrites 11 and 12 and two permanent magnets 51 and 52.

La figure 23 représente schématiquement en perspective une antenne dite empilée selon un huitième mode de réalisation de l'invention.The figure 23 schematically represents in perspective a so-called stacked antenna according to an eighth embodiment of the invention.

Dans ce mode de réalisation, l'antenne comprend plusieurs plaques métalliques 4H1, 4H2, 4H3 et 4H4 formant la partie rayonnante. Chaque plaque métallique est reliée à l'excitateur 6. Entre le plan 4B de masse et la plaque 4H4 se trouve un ferrite 12 dispersif, entre la plaque 4H4 et la plaque 4H3 se trouve un aimant 52, entre la plaque 4H3 et la plaque 4H2 se trouve un ferrite 11 dispersif et entre la plaque 4H2 et la plaque 4H1 se trouve un aimant 51.In this embodiment, the antenna comprises several metal plates 4 H1 , 4 H2 , 4 H3 and 4 H4 forming the radiating part. Each metal plate is connected to the exciter 6. Between the ground plane 4 B and the plate 4 H4 is a dispersive ferrite 1 2 , between the plate 4 H4 and the plate 4 H3 is a magnet 5 2 , between the plate 4 H3 and plate 4 H2 is a dispersive ferrite 11 and between plate 4 H2 and plate 4 H1 is a magnet 51 .

La figure 24 représente schématiquement en perspective une antenne dite empilée selon un neuvième mode de réalisation de l'invention.The figure 24 schematically shows in perspective a so-called stacked antenna according to a ninth embodiment of the invention.

L'antenne de ce mode de réalisation est similaire au huitième mode de réalisation, en ce qu'il contient une pluralité de plaques métalliques 4H1, 4H2, 4H3, 4H4, 4H5, 4H6, 4H7 et 4H8 de forme circulaire, formant la partie rayonnante et reliées à l'excitateur 6. Entre les plaques métalliques se trouvent alternativement un ferrite 11, 12, 13 ou 14 dispersive de forme circulaire ou un aimant 51, 52, 53 ou 54 de forme circulaire.The antenna of this embodiment is similar to the eighth embodiment, in that it contains a plurality of metal plates 4 H1 , 4 H2 , 4 H3 , 4 H4 , 4 H5 , 4 H6 , 4 H7 and 4 H8 of circular shape, forming the radiating part and connected to the exciter 6. Between the metal plates there are alternately a dispersive ferrite 1 1 , 1 2 , 1 3 or 1 4 of circular shape or a magnet 5 1 , 5 2 , 5 3 or 5 4 in circular shape.

La figure 25 représente schématiquement en perspective une antenne dite empilée selon un neuvième mode de réalisation de l'invention.The figure 25 schematically shows in perspective a so-called stacked antenna according to a ninth embodiment of the invention.

L'antenne de ce mode de réalisation est similaire au premier mode de réalisation en ce qu'il comprend un aimant disposé sur la partie rayonnante 4H de l'antenne, celle-ci étant séparée du plan de masse 4B par le substrat de ferrite dispersif 1.The antenna of this embodiment is similar to the first embodiment of embodiment in that it comprises a magnet arranged on the radiating part 4H of the antenna, the latter being separated from the ground plane 4B by the dispersive ferrite substrate 1.

Selon une particularité de ce mode de réalisation, la deuxième plaque formant la partie rayonnante 4H est découpée de manière à former une spirale plate rectangulaire. Par exemple, cette spirale est centrée sur l'excitateur 6 de l'antenne.According to a feature of this embodiment, the second plate forming the radiating part 4H is cut so as to form a rectangular flat spiral. For example, this spiral is centered on the exciter 6 of the antenna.

L'invention ne se limite pas aux seuls modes de réalisation décrits. En particulier, les ferrites dispersifs, les aimants, les pièces insérées ou les plaques en métal peuvent prendre des formes différentes. Les aimants peuvent présenter des valeurs différentes de celles indiquées dans les graphiques. Les antennes empilées peuvent contenir davantage de couches.The invention is not limited to the embodiments described. In particular, dispersive ferrites, magnets, inserts or metal plates can take different shapes. The magnets may have different values from those shown in the graphs. Stacked antennas can contain more layers.

Claims (13)

  1. Antenna adapted to receive or emit at least one working frequency, comprising:
    - at least two non-ferrous metal plates extending mainly according to a horizontal plane, at least one first plate forming a radiating portion (4H; 4H1, 4H2, 4H3, 4H4 ; 4H1, 4H2, 4H3, 4H4, 4H5, 4H6, 4H7, 4H8) and a second plate forming a mass plane (4B),
    - at least one substrate (1; 11, 12; 11, 12, 13, 14) extending mainly according to a horizontal plane, arranged between the mass plane (4B) and the radiating portion (4H),
    - an excitor (6) of length at least equal to the thickness of the substrate, extending between the mass plane (4B) and the radiating portion (4H) and connected to the radiating portion (4H), and adapted to supply the antenna,
    said antenna being characterised in that:
    a) said at least one working frequency is comprised in a kilometric comprised between 30 kHz and 300 kHz, or a hectometric comprised between 0.3 MHz and 3 MHz, or a decametric comprised between 3 MHz and 30 MHz, or a metric comprised between 30 MHz and 300 MHz band of frequencies,
    b) the substrate is a dispersive ferromagnetic substrate, called dispersive ferrite (1), presenting at said at least one working frequency, as magnetic features, a high relative magnetic permeability comprised between 10 and 10,000 and a high magnetic loss tangent greater than 0.1,
    c) said antenna comprises local modification means (5) of the magnetic features of the dispersive ferrite (1), which are a magnet (5) arranged on one of the non-ferrous metal plates (4B; 4H), wherein said magnet (5) does not cover the whole surface of the dispersive ferrite, said magnet generating a magnetic field leading to a gradual and local reduction of the relative magnetic permeability and the magnetic losses of the dispersive ferrite.
  2. Antenna according to claim 1, characterised in that the magnet (5) is arranged on said at least one first plate forming a radiating portion (4H; 4H1, 4H2, 4H3, 4H4; 4H1, 4H2, 4H3, 4H4, 4H5, 4H6, 4H7, 4H8) of the antenna.
  3. Antenna according to claim 1, characterised in that the magnet (5; 51, 52; 51, 52, 53, 54) is a permanent magnet.
  4. Antenna according to claim 1, characterised in that the magnet (5; 51, 52; 51, 52, 53, 54) is an electromagnet, supplied by a variable direct current electric generator (9).
  5. Antenna according to one of claims 1 to 3, characterised in that it comprises a succession of dispersive ferrite (11, 12; 11, 12, 13, 14) and of magnets (51, 52; 51, 52, 53, 54) stacked alternatively between the radiating portion (4H; 4H1, 4H2, 4H3, 4H4; 4H1, 4H2, 4H3, 4H4, 4H5, 4H6, 4H7, 4H8) and the mass plane (4B).
  6. Antenna according to claim 5, characterised in that the radiating portion comprises a metal plate (4H2, 4H3, 4H4; 4H2, 4H3, 4H4, 4H5, 4H6, 4H7, 4H8) between each ferrite (11, 12; 11, 12, 13, 14) and magnet (51, 52).
  7. Antenna according to claim 6, characterised in that the metal plates are connected between them.
  8. Antenna according to one of claims 1 to 6, characterised in that the dispersive ferrite (1) presents a size in the horizontal plane greater than the size of the metal plates.
  9. Antenna according to one of claims 1 to 7, characterised in that it comprises at least one short-circuit (2) connecting the mass plane (4B) and the radiating portion (4H), in contact with an edge of the dispersive ferrite (1).
  10. Antenna adapted to receive or emit at least one working frequency, comprising:
    - at least two non-ferrous metal plates extending mainly according to a horizontal plane, at least one first plate forming a radiating portion (4H) and a second plate forming a mass plane (4B),
    - at least one substrate (1) extending mainly according to a horizontal plane, arranged between the mass plane (4B) and the radiating portion (4H),
    - an excitor (6) of length at least equal to the thickness of the substrate, extending between the mass plane (4B) and the radiating portion (4H) and connected to the radiating portion (4H), and adapted to supply the antenna,
    said antenna being characterised in that:
    d) said at least one working frequency is comprised in a kilometric comprised between 30 kHz and 300 kHz, or a hectometric comprised between 0.3 MHz and 3 MHz, or a decametric comprised between 3 MHz and 30 MHz, or a metric comprised between 30 MHz and 300 MHz band of frequencies,
    e) the substrate is a dispersive ferromagnetic substrate, called dispersive ferrite (1), presenting at said at least one working frequency, as magnetic features, a high relative magnetic permeability comprised between 10 and 10,000 and a high magnetic loss tangent greater than 0.1,
    f) said antenna comprises local modification means (5; 10) of the magnetic features of the dispersive ferrite (1), said local modification means (5; 10) being arranged off-centred with respect to the excitor (6), so that the relative magnetic permeability and the magnetic losses of the dispersive ferrite are gradually and locally reduced.
  11. Antenna according to claim 10, characterised in that the local modification means are a magnet (5).
  12. Antenna according to claim 11, characterised in that the magnet (5) is arranged on one the non-ferrous metal plates of the antenna, preferably the radiating portion (4H).
  13. Antenna according to claim 10, characterised in that said local modification means are at least one material part (10) having a low relative magnetic permeability and a low loss tangent, said part (10) being inserted in the dispersive ferrite (1).
EP18793251.2A 2017-10-04 2018-10-04 Antenna with partially saturated dispersive ferromagnetic substrate Active EP3692598B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR1759284A FR3071968B1 (en) 2017-10-04 2017-10-04 PARTIALLY SATURATED DISPERSIVE FERROMAGNETIC SUBSTRATE ANTENNA
PCT/FR2018/052456 WO2019069033A1 (en) 2017-10-04 2018-10-04 Antenna with partially saturated dispersive ferromagnetic substrate

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EP3692598A1 EP3692598A1 (en) 2020-08-12
EP3692598B1 true EP3692598B1 (en) 2022-07-20

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EP (1) EP3692598B1 (en)
CN (1) CN111183552B (en)
EA (1) EA202090664A1 (en)
ES (1) ES2926348T3 (en)
FR (1) FR3071968B1 (en)
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WO (1) WO2019069033A1 (en)

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CN111555026B (en) * 2020-05-25 2022-02-25 维沃移动通信有限公司 Electronic equipment

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CN111183552B (en) 2022-02-18
US20200235473A1 (en) 2020-07-23
EA202090664A1 (en) 2020-07-22
US11114761B2 (en) 2021-09-07
FR3071968B1 (en) 2020-11-27
WO2019069033A1 (en) 2019-04-11
IL273692B2 (en) 2023-07-01
CN111183552A (en) 2020-05-19
EP3692598A1 (en) 2020-08-12
IL273692B1 (en) 2023-03-01
FR3071968A1 (en) 2019-04-05
ES2926348T3 (en) 2022-10-25

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