Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/16—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole
  • H01Q9/26—Resonant antennas with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole with folded element or elements, the folded parts being spaced apart a small fraction of operating wavelength
  • H01Q9/27—Spiral antennas
• • 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
• • 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
  • H01Q11/00—Electrically-long antennas having dimensions more than twice the shortest operating wavelength and consisting of conductive active radiating elements
  • H01Q11/02—Non-resonant antennas, e.g. travelling-wave antenna
  • H01Q11/10—Logperiodic antennas
  • H01Q11/105—Logperiodic antennas using a dielectric support
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
  • H01Q15/0006—Devices acting selectively as reflecting surface, as diffracting or as refracting device, e.g. frequency filtering or angular spatial filtering devices
  • H01Q15/006—Selective devices having photonic band gap materials or materials of which the material properties are frequency dependent, e.g. perforated substrates, high-impedance surfaces
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
  • H01Q15/14—Reflecting surfaces; Equivalent structures
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q17/00—Devices for absorbing waves radiated from an antenna; Combinations of such devices with active antenna elements or systems

Definitions

• the present invention relates to a wire antenna capable of operating in at least one predetermined frequency band, comprising a plurality of superimposed layers.
• the invention finds applications particularly in the field of electromagnetic listening systems.
• the antennas which are used either individually or in a goniometric network, must operate in a very wide frequency band and in circular, linear or double linear polarization, corresponding respectively to the ranges of interest of the electromagnetic signals in frequency and polarization.
• These antennas must be as compact as possible and, in particular, thin, especially to facilitate integration onto carriers. They must also exhibit reproducible radiation performance (gain, radiation pattern quality, etc.) from one antenna to another, particularly for network applications or to allow for replacement during maintenance.
• the radiating element consists of a metal wire which is shaped to describe, in a so-called radiating surface, a spiral or log-periodic pattern.
• the metal wire is wound around itself to form a spiral when viewed from above.
• This spiral can be, for example, an Archimedean spiral, a logarithmic spiral, or another type.
• the metal wire is shaped to have several strands when viewed from above.
• Each strand is inscribed within an angular sector, extends radially, and has indentations. The length of each indentation and the spacing between two successive indentations of a strand follow a logarithmic progression.
• the metallic wire which is the radiating element is made by etching a thin metallic layer, for example a copper layer with a thickness between 2 and 20 ⁇ m (micrometers), deposited on a thin insulating (dielectric) support layer.
• a thin metallic layer for example a copper layer with a thickness between 2 and 20 ⁇ m (micrometers)
• dielectric thin insulating
• the radiating element is capable of emitting a wave that propagates forward of the radiating surface (away from the absorbing cavity) and a wave that propagates backward of the radiating surface (toward the absorbing cavity). The latter is absorbed by the absorbing cavity.
• Such an antenna is quite bulky due to the size of the absorbing cavity. It also has low efficiency, since half the power emitted by the radiating element is absorbed within the cavity. Finally, achieving consistent radio performance for such an antenna is difficult due to a lack of control over the electromagnetic characteristics of the absorbing material filling the cavity.
• the radiating elements are placed on a loaded bandgap electromagnetic structure, called LEBG (Loaded Electromagnetic Band Gap), on a lower ground plane.
• LEBG Long Electromagnetic Band Gap
• a surface composed of periodic metallic patterns connected by resistors is placed within the antenna cavity.
• the wave emitted backward by the radiating element is absorbed in a thin layer consisting of a metallic reflector plate topped with metal and the resistively loaded LEBG material.
• the radiating element is etched onto a high-impedance surface (HIS), resting on spaced periodic metallic patterns placed within the antenna cavity and connected to the ground plane by metallized links, also called vias.
• HIS high-impedance surface
• the effective bandwidth of such an antenna, in which the interference between the incident and reflected waves is constructive, corresponds approximately to one octave. Consequently, this type of antenna is limited to narrow operating bands and cannot simultaneously cover a multi-octave frequency band.
• a fourth prior art wire antenna described in the patent application FR3017493 It has been proposed to insert, between the broadband radiating element of frequencies and the spacer substrate layer, one or more layers with sets of periodic resistive patterns, either with a single set of resistive patterns or with several sets of nested resistive patterns.
• Such a layer comprises resistive patterns with resistance values that vary gradually from a central point of the antenna to an outer edge. These resistive patterns are positioned in the near field of the antenna's radiating element. The resulting antennas are compact and provide high gain over a wide frequency band, without significant waviness in the radiation patterns.
• these antennas exhibit surface waves (or creeping waves) that propagate along the lower ground plane of the antenna cavity and beyond onto the metal support on which the antenna is mounted. These surface waves, combined with structural edge effects, interact with the main electric field radiated by the antenna, resulting in a degradation of the radiation pattern quality. Specifically, wave effects, which become more pronounced at higher frequencies, appear in the main lobe of the radiation pattern. Consequently, the antenna gain is degraded, as is the half-power angle of the main radiation lobe.
• the invention aims to correct the aforementioned problems by proposing a compact wire antenna capable of operating in a wide frequency band, for which the effects of surface waves are controlled in order to eliminate the defects mentioned above.
• the invention proposes a wire antenna adapted to operate in at least one frequency band according to claim 1.
• the wire antenna according to the invention thanks to the presence of a resistive grid with empty patterns which allows to trap and/or attenuate surface waves, has an increased gain.
• the wire antenna according to the invention may have one or more of the characteristics detailed in claims 2 to 9.
• THE figures 1 to 3 schematically represent a wire antenna 2 according to a first embodiment of the invention, in cross-section, in perspective view and in exploded perspective view.
• the wire antenna 2 is a broadband frequency antenna, for example, capable of operating in a frequency range from 1 GHz (GigaHertz) to 20 GHz.
• the wire antenna 2 has the shape of a circular disk, center O, and is composed of several concentric layers stacked in thickness along an axis A.
• the axis A is a central axis orthogonal to the radiation plane of the antenna.
• antenna 2 has an outside diameter of 45mm.
• the antenna has another regular geometric shape, for example elliptical or rectangular, also exhibiting a central axis of similar symmetry.
• the support layer 6 is for example formed by a first dielectric substrate, for example of a glass fiber reinforced ceramic type, having a first thickness h1, for example between 0.128 mm and 1.524 mm, for example equal to 0.254 mm.
• the spacer substrate 8 is arranged above a reflector plane or ground plane 10.
• the reflecting plane 10 is preferably metallic, and is located at a distance h0 below the radiation surface S. Its function is to reflect any incident wave regardless of its frequency within a given frequency range.
• the spacer substrate 8 has the general external shape of a disk with axis A and a second thickness h2 that is substantially constant.
• This spacer substrate is a second dielectric substrate with a given relative permittivity.
• it is made of a dielectric material with low relative permittivity (e.g., unfilled foam), a Duroid-type dielectric material (registered trademark), or a possibly multilayer composite material.
• the second thickness h2 of the spacer substrate 8 is greater than the first thickness h1 of the support layer 6.
• the thickness of the spacer substrate 8 is between 4 mm and 8 mm, for example equal to 6 mm.
• the spacer substrate 8 is made of magneto-dielectric or pure magnetic material.
• the spacer substrate 8 is formed in a progressive or perforated dielectric material, hollowed out in its center, so as to achieve an increasing relative permittivity from the center to the outer edge.
• a resistive grid 12 comprising a resistive surface 14 of predetermined resistivity value and at least one set of repeating, non-contiguous recesses (or holes) 18 so as to form said grid.
• the recesses 18 are areas devoid of resistivity, hereinafter referred to as empty patterns.
• the recesses 18 are made by absence of resistive material deposition.
• the resistive grid 12 is, according to a first variant of the embodiment, arranged on a face 16 of the spacer substrate 8, or lower face, oriented towards the reflector plane 10.
• the resistive grid 12 is arranged on a face 20 of the reflecting plane 10, called the upper face and oriented towards the radiating element 4.
• the resistive grid is placed on a third dielectric, magnetic or magneto-dielectric substrate interposed between face 6 of the spacer 8 and face 20 of the reflector plane 10.
• the resistive grid 12 is arranged in a so-called cavity bottom area, between the spacer substrate 8 and the reflector plane 10.
• the resistive grid 12 is made from a resistive film, and the empty patterns 18 are, for example, created by hollowing out the resistive film.
• the resistive grid is made by depositing resistive ink according to a pattern, so as to form the desired empty patterns by the absence of resistive ink deposits.
• the resistive grid 12 is produced by conventional screen printing or any other equivalent process, for example 3D printing or aerosol printing.
• the resistive grid 12 has a third thickness h3, which can vary between a few micrometers and a few tens of micrometers depending on the desired resistance value and the intrinsic characteristics of the resistive ink used.
• the radiating element 4 comprises first and second metallic wires 22 and 24, which are respectively formed according to a spiral pattern or a sinuous log-periodic pattern, for example. More particularly, the pattern forms an Archimedean spiral in the first embodiment, as illustrated in the figures 1 to 3 .
• Each wire, 22, 24, is wound around the origin point O, which corresponds to the intersection of the axis A and the radiation surface S.
• the radiating element 4 is for example produced by an engraving operation, directly on the upper face 19 of the support layer 6.
• the radiating element is a single-polarized or double-polarized element of the sinuous DuHamel type.
• the radiating element is hybrid.
• a power supply device (not shown) for the radiating element 4 is positioned below the reflector plane 10, which is electrically connected to ground.
• the reflector plane 10 and the layers 12, 8, 6 positioned above it are pierced by a recessed passage 28, along axis A, for the passage of conductor(s) to electrically supply the radiating element 4.
• an active area of the radiating element 4 emits a first direct wave propagating forwards, i.e. opposite the spacer substrate 8, and a second wave propagating backwards, i.e. in the direction of the spacer substrate 8.
• the second wave passes through the spacer substrate 8 and the resistive grid 12, is reflected by the reflector plane 10, then passes again through the resistive grid 12 and the spacer substrate 8.
• the resistive grid 12 includes regular empty patterns 18 arranged in this embodiment on concentric rings of center O', and a central non-resistive zone 30, comprising the hollow passage 28.
• the resistive layer 12 includes a peripheral zone 32, annular in this first embodiment, which does not have empty patterns, in other words it is a solid resistive zone, for better absorption efficiency of surface waves in this zone.
• the peripheral zone is located near the outer edge of the antenna, for example between the outer edge of the antenna and the resistive grid.
• the 18 empty motifs are distributed over concentric rings, forming, within each ring, sets of empty motifs of the same size and geometric shape, regularly distributed across the ring. Furthermore, across all the rings, the empty motifs are radially aligned and correspond to the same angular width.
• the resistive grid 12 comprises empty square motifs 34, 36 as illustrated in the figure 4 .
• the resistive grid 12 comprises a resistive surface 15, and two sets of empty patterns, a first set 33 of first square-shaped patterns 34 and a second set 35 of second square-shaped patterns 36.
• the motifs are arranged according to an orthogonal grid, with regular spacing between two successive motifs.
• the resistive surface has a resistivity of 1000 ⁇ per square.
• the first set of 33 empty patterns forms a first external zone, close to the outer edge of grid 12, and the second set of 35 empty patterns forms a second internal zone of square shape.
• the circular zone 30 which in one embodiment corresponds to the recessed passage 28.
• the circular zone 30 has a diameter greater than the diameter of the central recessed passage 28.
• the circular zone 30 corresponds to a recessed (non-resistive) surface.
• the first square patterns 34 have a larger surface area than the second square patterns 36.
• the first patterns 34 are squares of 6.4 mm on each side, and are positioned in an active area for the antenna going, approximately, from 2 GHz to 4 GHz
• the second patterns 36 are squares of 3.2 mm on each side and are positioned in an active area for the antenna going, approximately, from 4 GHz to 18 GHz.
• the empty patterns are periodized and of dimensions (sides of the squares) smaller than the wavelength associated with the center frequency of the considered sub-band radiated by the antenna.
• the radio performance of the antenna is improved over a frequency range from 2 GHz to 18 GHz.
• the main lobe of the antenna pattern is formed over the entire frequency band considered. Pattern ripples are not present in vertical polarization and are negligible in horizontal polarization.
• the resistive grid 12 has annular empty motifs 42 interspersed between resistive rings 44. This is a concentric ring topology, the annular empty motifs 42 being in regular alternation with the resistive rings 44.
• This embodiment is particularly suitable for a spiral radiating element.
• the heights h1 and h2 of the constituent materials of the antenna are chosen to have constructive interference between the spiral-type radiating element and the reflecting plane (lower ground plane of the antenna) in the frequency band of interest.
• the shape, size, and spatial repetition pattern or topology of the empty motifs are variable and defined, for each embodiment, using software. 3D electromagnetic simulation or electromagnetic simulator. Indeed, an analytical preliminary dimensioning of resistive patterns is particularly complex.
• a resistivity value for the resistive grid, a geometric shape for each empty pattern and a pattern repetition topology are chosen, and the pattern size and pattern spacing are calculated using 3D electromagnetic simulation software.
• Such simulation software is known, for example software that solves Maxwell's equations in integral form, using the finite integral method.
• the size and topology of the empty patterns are selected to improve the stability of the radiation pattern and promote the absence of undulation, which translates into effective trapping of surface waves.
• these choices are made by implementing several simulations and comparing the results to select the size, shape, and spacing of the empty patterns best suited for a given application.
• the antenna 2' further comprises a second resistive layer 48, between the support 6 and the spacer substrate 8, comprising an array 50 of resistive motifs 52, each resistive motif 52 having a given resistive surface area.
• Each resistive motif is produced, for example, by depositing a resistive ink, and the spaces between resistive motifs are empty.
• the first resistive grid 12 comprises two partial resistive sub-grids 54, 56, each formed of a resistive surface having recesses which form empty patterns 62, 64 and 66.
• the assembly 50 of the second resistive layer 48 is placed above a separation zone 60 between the first resistive subgrid 54 and the second resistive subgrid 56, this separation zone 60 being an empty zone, devoid of resistive layer, above the reflector plane 10.
• each resistive subgrid 54, 56 comprises at least one set of empty motifs placed opposite a area devoid of resistive patterns 52 of the resistive layer 48, therefore an "empty" area, without resistance.
• the set 50 of resistive patterns of the resistive layer 48 forms a spatially nested zone between the first subgrid 54 and the second subgrid 56. There is no spatial overlap, in top view, between the zone formed by the set 50 and the first subgrid 54 and the second subgrid 56.
• the first subgrid 54 contains empty square motifs 62 aligned in a square ring.
• the first subgrid 54 includes a zone 30 centered on axis A, without resistance, as in the first embodiment.
• the resistive motifs 52 of the resistive layer 48 are square in shape and of the same dimensions as the empty motifs 62 of the first sub-grid 54.
• the second subgrid 56 has a peripheral resistive area 32 without recess, and two sets of empty square patterns 64 and 66 of different sizes.
• each resistive subgrid has a resistivity of 1000 ⁇ per square.
• the two resistive subgrids 54 and 56 cover the frequency bands from 2 GHz to 4 GHz and from 10 GHz to 18 GHz, respectively.
• the set 50 of resistive patterns 52 placed between the spacer substrate 8 and the support 6 covers the frequency band from 4 GHz to 10 GHz.
• the antenna defined according to this second embodiment called a hybrid cavity antenna, promotes an absence of waviness in radiation patterns over the entire frequency band considered.
• Variations of this embodiment are conceivable, for example by adding a resistance gradient or a multilayer structuring of the resistive grid 12.
• resistive grid with a progressive and decreasing resistance variation between a high resistance value at the periphery and a lower value at its center.
• FIG. 9 schematically illustrates, in cross-section, a multi-layered structure of a resistive grid according to a third embodiment of a wire antenna according to the invention.
• the 2" antenna of the figure 9 includes a radiating element 4 placed on a planar support 6, itself arranged on a first spacer substrate 8.
• first spacer substrate 8 and the reflector plane 10 are stacked a first resistive grid 12A, a second spacer substrate 8' and a second resistive grid 12B.
• the first resistive grid 12A comprises a set of 68 empty motifs, for example a central ring, placed opposite a resistance-free area 70 (empty zone) of the second resistive grid 12B.
• the second resistive grid 12B comprises a set of 72 empty motifs, arranged for example in a peripheral ring, opposite a resistance-free area (empty zone) of the first grid 12A.
• the antenna includes a resistive grid between the reflector plane 10 and the spacer substrate 8 or 8', but the resistive grid does not have a solid peripheral resistive area.
• the resistive grid(s) are produced by conventional screen printing process or any other equivalent process, for example 3D printing or aerosol printing.
• the resistive grid or grids are deposited either directly on the reflector plane 10, or on the lower face 16 of the spacer substrate 8, or on a dielectric, magnetic or magneto-dielectric substrate placed on the reflector plane 10.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Optics & Photonics (AREA)
• Aerials With Secondary Devices (AREA)
• Details Of Aerials (AREA)

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• 2018
  • 2018-05-04 FR FR1800429A patent/FR3080959B1/fr active Active
• 2019
  • 2019-05-03 IL IL278362A patent/IL278362B2/he unknown
  • 2019-05-03 EP EP19720680.8A patent/EP3788674B1/fr active Active
  • 2019-05-03 WO PCT/EP2019/061399 patent/WO2019211446A1/fr not_active Ceased
  • 2019-05-03 US US17/050,970 patent/US11495887B2/en active Active

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