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EP3266064A1 - Omnidirectional wideband antenna structure - Google Patents

Omnidirectional wideband antenna structure

Info

Publication number
EP3266064A1
EP3266064A1 EP16709999.3A EP16709999A EP3266064A1 EP 3266064 A1 EP3266064 A1 EP 3266064A1 EP 16709999 A EP16709999 A EP 16709999A EP 3266064 A1 EP3266064 A1 EP 3266064A1
Authority
EP
European Patent Office
Prior art keywords
radiating
antenna structure
plane
metal
metal strip
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP16709999.3A
Other languages
German (de)
French (fr)
Other versions
EP3266064B1 (en
Inventor
Sébastien PALUD
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Telediffusion de France ets Public de Diffusion
Original Assignee
Telediffusion de France ets Public de Diffusion
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telediffusion de France ets Public de Diffusion filed Critical Telediffusion de France ets Public de Diffusion
Publication of EP3266064A1 publication Critical patent/EP3266064A1/en
Application granted granted Critical
Publication of EP3266064B1 publication Critical patent/EP3266064B1/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Classifications

    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/32—Adaptation for use in or on road or rail vehicles
    • H01Q1/325—Adaptation for use in or on road or rail vehicles characterised by the location of the antenna on the vehicle
    • H01Q1/3275—Adaptation for use in or on road or rail vehicles characterised by the location of the antenna on the vehicle mounted on a horizontal surface of the vehicle, e.g. on roof, hood, trunk
    • 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
    • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
    • H01Q9/0414—Substantially flat resonant element parallel to ground plane, e.g. patch antenna in a stacked or folded configuration
    • 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
    • H01Q9/0407—Substantially flat resonant element parallel to ground plane, e.g. patch antenna
    • H01Q9/0421—Substantially flat resonant element parallel to ground plane, e.g. patch antenna with a shorting wall or a shorting pin at one end of the element
    • 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
    • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
    • H01Q9/40—Element having extended radiating surface
    • 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
    • H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
    • H01Q9/42—Resonant antennas with feed to end of elongated active element, e.g. unipole with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Definitions

  • the invention relates to a broadband antennal structure.
  • the invention relates to a vertically polarized broadband antenna array with horizontal omnidirectional radiation, in particular for mobile application, for frequencies between the low frequency bands LF (for Low Frequency in English) and ultra high frequency UHF (for Ultra High Frequency in English).
  • Vertical-polarized broadband antennas are used in various telecommunication or broadcasting applications, particularly in the context of mobile applications, for example by being placed on vehicles.
  • the antennas currently used for these types of mobile applications are generally broadband monopole antennas (conical monopole, planar variable geometry) integrated under a radome, or damped bullets, right or inclined.
  • the antennas used are generally biconical antennas or whip antennas equipped with an adaptation cell for the frequencies between the low frequencies LF and the high frequencies HF (for High Frequency).
  • antennas have the main disadvantage of having a vertical footprint near or more than a quarter of the wavelength of the lowest frequency of operation of the antenna.
  • the solutions currently proposed to reduce this vertical space are inefficient and have a large reduction in gains for radiation in the horizontal plane, called azimuthal radiation.
  • the azimuthal radiation is generally not stable in frequency on the frequency band of the antennas.
  • the invention aims to overcome at least some of the disadvantages of known antennal structures.
  • the invention aims to provide, in at least one embodiment of the invention, a vertical polarization antenna structure of small vertical dimensions.
  • the invention also aims to provide, in at least one embodiment, an antenna structure whose performance is stable over a wide frequency band.
  • the invention also aims to provide, in at least one embodiment of the invention, an antenna structure with omnidirectional radiation in a horizontal plane.
  • the invention also aims to provide, in at least one embodiment, an antenna structure whose azimuth gain is substantially constant over the entire frequency band of operation.
  • the invention relates to an antenna structure with a wide frequency band, with a polarization in a preferred direction, called a vertical direction, adapted for transmitting and / or receiving signals of wavelength between a length of minimum wave and a maximum wavelength, said antennal structure comprising:
  • a first metal strip and a second metal strip arranged vertically, spaced from each other and substantially parallel to each other, the second metal strip being connected to the ground plane and substantially perpendicular to the ground plane, a radiant loop, comprising a plurality of radiating strips, a first end of the radiating loop being connected to the first metal strip and a second end of the radiant loop being connected to the second metal strip, at least one short-circuit element, electrically connecting the first metal strip and the second metal strip in their parts the further away from the ground plane.
  • the maximum wavelength corresponds to signals of minimum frequency in the frequency band
  • the minimum wavelength corresponds to signals of maximum frequency in the frequency band.
  • the part of the frequency band close to the minimum frequency is called the lower part of the band
  • the part of the frequency band close to the maximum frequency is called the upper part of the band.
  • the minimum and maximum frequencies correspond to the terminals of the frequency band in which the antenna structure is intended to be used without degradation of performance.
  • the antennal structure is adapted to operate outside this frequency band, but without guarantee of performance.
  • Metal strip and radiating strip are metal elements or a combination of metal elements extending mainly over two dimensions, a width and a length, and having a negligible thickness with respect to said width and length.
  • the metal strips and the radiating strips are distinguished from a wire which is characterized mainly by a single dimension, its length, and a three-dimensional element of which none of the dimensions is negligible compared to the other two.
  • the metal strips and the radiating strips have a width greater than one twelfth of the maximum wavelength.
  • An antenna structure according to the invention has a small footprint and allows a transmission or reception of a signal over a wide band of frequency and linear polarization.
  • the antenna structure also allows omnidirectional radiation in the horizontal plane, called azimuthal radiation, and substantially constant gain over the entire operating frequency band in this plane.
  • the radiation of the antennal structure is optimized in the horizontal plane.
  • the use of the antennal structure in a wide band of frequency of use is in particular allowed thanks to the width of the metal strips and the radiating strips.
  • the radiating loop comprises an upper portion substantially parallel to the horizontal plane, of greater length than the distance between the first band metal and the second metal strip, and whose two ends are connected to the first metal strip and the second metal strip by substantially vertical side portions and then substantially horizontal connecting portions.
  • the short-circuit element makes it possible to improve the adaptation of the antenna structure.
  • the omnidirectional radiation of the antennal structure is improved in the central part of the frequency band, called the band medium.
  • the portions of the metal strips farthest from the ground plane indicate on each metal strip the portion representing 50% of the surface of the metal strip, situated between the end of the metal strip to which the radiating loop is connected to the medium of the metal strip. the metal band.
  • the ground plane extending horizontally and the metal strips extending vertically, the polarization is vertical, the radiation is omnidirectional in the horizontal plane, and the azimuthal gain is substantially constant over the entire operating band.
  • a vertical polarization allows a better efficiency of the mobile antenna structure, for example if it is mounted on the roof of a moving vehicle, and more particularly at a height near the ground level.
  • the radiating loop is a folded radiating loop, in which the radiating strips form at least one u-shaped straight section fold formed of two radiating strips extending in the vertical direction connected at their ends to the closer to the ground plane by a radiating band, said base of the U, extending in a direction parallel to the horizontal plane.
  • the U-shaped fold or folds make it possible to reduce the length of the radiating strips parallel to the horizontal plane, in order to reduce the zenith radiation, that is to say the radiation that does not propagate in the plane. horizontal, in the upper part of the frequency band.
  • U-folds result in a distribution of radiating bands parallel to the horizontal plane in several parallel and non-coincidental planes.
  • the U-fold or folds improve the impedance matching of the antenna structure, and reduce the bulk of the antenna. antennal structure while maintaining the same total length of the metal strips and radiating strips of the radiating structure.
  • the base of the U of at least one U-fold is arranged between the first metal strip and the second metal strip, and the short-circuit element is formed at least in part by said base of the U.
  • an antenna structure according to the invention has a vertical space between the ground plane and the highest point of the radiating structure, less than one-tenth of the maximum wavelength.
  • the reduction of antennal congestion below one-tenth of the maximum wavelength makes it possible to avoid performance degradation in the upper part of the strip and allows radiation without loss of gain at the horizon.
  • the antenna structure is thus less bulky than conventional monopole quarter wave antennas, while having equal or greater performance in terms of gain and radiation in the horizontal plane.
  • the first metal strip is adapted to be connected to a positive terminal of a transmitter / receiver and the ground plane is adapted to be connected to a negative terminal of said transmitter / receiver.
  • Transmitter / receiver is either a single transmitter or a single receiver, or a device adapted to both transmit and receive signals.
  • the transceiver is adapted to be connected to the antenna structure via a coaxial cable whose inner conductor connects the positive terminal of the transceiver to the first metal strip and an outer conductor connects the negative terminal of the transceiver.
  • transmitter / receiver to the second metal strip and / or the ground plane.
  • the coaxial cable allows a better impedance matching of the antenna structure.
  • an antenna structure comprises a metal case disposed on the ground plane and defining a cavity adapted to contain the transmitter / receiver, said metal housing being electrically connected to the ground plane and the second metal strip.
  • the cavity formed by the metal case allows the transceiver to be embedded in the antenna structure, thereby reducing disturbances between the antenna structure and the transceiver, while maintaining a low connection length between the transmitter / receiver and the first metal strip and the ground plane.
  • the lengths of the first metal strip and the second metal strip may be reduced so that the space released is occupied, in part of its height, by the metal case: the height of the metal case is preferably less than one sixth of the total height of the antenna structure.
  • the metal casing is adapted to receive processing elements of the signal emitted or received by the antenna structure, for example amplification, filtering elements, etc.
  • the first metal strip is connected to the transmitter / receiver via a metal connection surface substantially parallel to the horizontal plane.
  • the metal bonding surface connects an end of the first metal strip to the transmitter / receiver to adjust the impedance match to the desired frequency band.
  • the metal connection surface has a trapezoidal shape, a large base of the trapezium being connected to the first metal strip and a small base of the trapezium being connected to the transmitter / receiver.
  • the connecting surface extends from the first metal strip and towards the second metal strip, or extends from the first metal strip and in the opposite direction to the second metal strip.
  • the length of the radiating structure between the positive terminal of the transceiver and the connection of the ground plane and the second metal strip is between half the maximum wavelength and the minimum wavelength.
  • the length of the radiating structure is understood to mean the sum of the length of the metal strips and the radiating strips forming said radiating structure.
  • this structural length allows an improvement in the adaptation and control of the azimuthal radiation over the entire frequency band.
  • the width of the radiating structure is between one eighth of the maximum wavelength and one third of the minimum wavelength.
  • the width of the radiating structure corresponding to the width of the radiating band composing the widest radiating structure, is sufficiently large to allow transmission / reception in a wide frequency band, and sufficiently weak so that the congestion of the antennal structure is limited.
  • the width of the radiating structure also influences the standing wave ratio, which is lower in the lower part of the frequency band as the width of the radiating structure is high.
  • the width of the radiating structure is less than one-eighth of the maximum wavelength.
  • Such a width is less advantageous than a width greater than one-eighth of the maximum wavelength, in particular in terms of adaptation of the antenna structure, but makes it possible to obtain an antenna of reduced size for practical or aesthetic reasons when the antenna structure is used in applications in which the adaptation of the antennal structure is not critical.
  • the width of the radiating strips is variable along the radiating loop.
  • the radiating strips have a variable width and therefore a variable surface in order to allow homogenization of the density surface of the current passing through the radiating strips.
  • This homogenization of the current surface density makes it possible to improve the radiation of the antenna structure and in particular to homogenize the gain of the antenna structure in the azimuthal plane.
  • the ground plane has a width and a length greater than the maximum wavelength.
  • the standing wave ratio of the antenna structure is improved.
  • the ground plane has a real length and width greater than the maximum wavelength
  • the ground plane is electrically connected to a metal surface having a length and a width greater than the maximum wavelength .
  • an antenna structure according to the invention comprises a radome surrounding the radiating structure.
  • the radome allows a protection of the radiating structure, for example against the weather, and allows to hide the antennal structure.
  • the radome is designed not to degrade the radiation of the antennal structure.
  • the invention also relates to a vehicle, characterized in that it is equipped with an antenna structure according to the invention, the ground plane of the antenna structure being fixed in electrical continuity to a surface extending in a substantially parallel plane in the horizontal plane.
  • a vehicle according to the invention is adapted to transmit and receive signals via the antennal structure, for telecommunications applications in particular.
  • the invention also relates to an antenna structure and a vehicle characterized in combination by all or some of the features mentioned above or hereafter.
  • FIG. 1 is a schematic perspective view of an antenna structure according to a first embodiment of the invention
  • FIG. 2 is a diagrammatic sectional view of an antenna structure according to the first embodiment of the invention
  • FIG. 3 is a schematic perspective view of an antenna structure according to a second embodiment of the invention.
  • FIG. 4 is a diagrammatic sectional view of an antenna structure according to the second embodiment of the invention.
  • FIG. 5 is a schematic perspective view of an antenna structure according to a third embodiment of the invention.
  • FIG. 6 is a diagrammatic sectional view of an antenna structure according to the third embodiment of the invention.
  • FIG. 7 is a schematic perspective view of an antenna structure according to a fourth embodiment of the invention.
  • FIG. 8 is a schematic perspective view of an antenna structure according to a fifth embodiment of the invention.
  • FIG. 9 is a schematic perspective view of an antenna structure according to a sixth embodiment of the invention.
  • FIG. 10 is a schematic perspective view of a vehicle equipped with an antenna structure according to one embodiment of the invention.
  • FIG. 11 is a curve representing the impedance matching of an antenna structure according to one embodiment of the invention as a function of frequency, in the frequency band 470-700 MHz,
  • FIG. 12 is an azimuthal radiation pattern of an antenna structure according to one embodiment of the invention for a frequency of 550 MHz
  • FIG. 13 is a curve representing the maximum azimuthal gains as a function of the frequency, in the frequency band 470-700 MHz, of an antenna structure according to one embodiment of the invention. 6. Detailed description of an embodiment of the invention
  • FIG. 1 shows schematically and in perspective an antenna structure according to a first embodiment of the invention.
  • FIG. 2 diagrammatically represents a section of the antenna structure according to this first embodiment, according to a section plane defined by the X-X and Z-Z axes as represented in FIG.
  • the antenna structure is adapted to transmit or receive signals in a wide frequency band between a minimum frequency associated with a maximum wavelength and a maximum frequency associated with a minimum wavelength. These minimum and maximum frequencies are the frequencies between which the antenna structure is intended to operate with optimum performance. Thus, the antenna structure can operate outside this frequency band, but the performance is not assured, since the design of the antenna structure is related to the desired frequency band.
  • the antenna structure can be configured for broadband application between a minimum frequency of 470 MHz and a maximum frequency of 700 MHz. These two values are therefore associated with a minimum wavelength of approximately 43 cm and a maximum wavelength of approximately 63 cm.
  • the antenna structure comprises a ground plane 1 to which is connected a radiating structure 12.
  • the plane 1 of mass defines a plane, called horizontal plane, comprising two axes XX and YY perpendicular to each other, and further defines an axis ZZ perpendicular to the horizontal plane.
  • the radiating structure 12 comprises two metal strips, a first metal strip 21 and a second metal strip 22, the ends farthest from the ground plane 1 are connected to a radiating loop 14.
  • the radiating loop 14 is composed of a plurality of radiating bands, here thirteen, referenced 231a, 233a, 234a, 235a, 236a, 237a, 231b, 233b, 234b, 235b, 236b, 237b and 232, making it possible to connect the ends of the two metal strips 21, 22.
  • the antenna structure is intended for the emission and / or reception of preferably vertical polarization signals, ie oriented along the ZZ axis, with azimuthal omnidirectional radiation, that is to say that the signals propagate substantially parallel to the horizontal plane.
  • the two metal strips 21, 22 are disposed substantially perpendicularly to the ground plane 1, and therefore arranged substantially vertically, and are parallel to one another.
  • the second metal strip 22 is connected to the ground plane 1 so as to be electrically continuous, for example by welding, screwing, riveting, and the first metal strip 21 is connected to a positive terminal of a transmitter / receiver 4, a negative terminal of the transmitter / receiver 4 being connected to the ground plane 1, the positive and negative terminals being preferably located in the plane defined by the axis XX and the ZZ axis.
  • the upper parts of the two metal strips 21, 22, that is to say the parts farthest from the ground plane 1, are connected by a short-circuit element 24.
  • the lower part of the first metal strip 21, that is to say the part closest to the ground plane 1, to which the positive terminal of the transmitter / receiver 4 is connected, is at a distance from the plane 1 of mass less than one hundredth of the minimum wavelength.
  • the distance separating the first metal band 21 from the second metal band 22 is less than one-tenth of the minimum wavelength.
  • the length of the second metal strip 22 is between one twelfth and one tenth of the minimum wavelength, in order to ensure optimum radiation over the entire frequency band.
  • the transmitter / receiver 4 may be for example only a transmitter, only a receiver or a device grouping the transmitter and receiver functions.
  • the plane 1 of mass is here represented of a size equivalent to the size of the structure 12 radiating along the axes XX and YY.
  • the ground plane 1 is electrically connected to a substantially horizontal surface of greater size, preferably of greater width and length than the maximum wavelength, for example the roof of a vehicle as shown with reference to FIG. Figure 10.
  • the radiating loop 14 comprises an upper portion, here composed of the radiating strips 231a, 231b, 232, 233a and 233b.
  • This upper portion is connected to substantially vertical lateral portions, respectively composed of radiating strips 235a and 235b, said lateral portions being connected to connecting portions respectively composed of radiating strips 234a, 236a, 237a and radiating strips 234b, 236b, 237b said connecting portions being connected to the two metal strips 21, 22, thereby closing the radiating loop 14.
  • the radiating strips 232, 233a, 233b, 234a, 234b, 237a, 237b are substantially horizontal.
  • the radiating strips 231a, 231b, 235a, 235b, 236a, 236b are substantially vertical. In this first embodiment, the radiating loop 14 is thus symmetrical on either side of the plane defined by the Y-Y and Z-Z axes.
  • the radiating strips each have a width defined along the axis YY and a length defined either along the axis XX for the radiating strips oriented substantially horizontally, or along the axis ZZ for the radiating strips oriented substantially vertically.
  • the width of the radiating loop 14 is defined by the width of the widest radiating band among those forming the radiating loop 14
  • the length of the radiating loop 14 is defined by the sum of the lengths of the radiating bands forming the 14 radiant loop.
  • the radiating strips all have the same width.
  • the length of the radiating structure 12 is the sum of the length of the radiating loop 14 and the lengths along the axis ZZ of the first metal strip 21 and the second metal strip 22, that is to say the length of the the radiating structure 12 between the positive terminal of the transceiver 4 and the connection of the ground plane 1 and the second metal strip 22.
  • the width of the radiating structure 12 is less than one-eighth of the maximum wavelength.
  • the adaptation of the antenna structure is thus less optimized, but makes it possible to reduce the size of the antenna structure when the use of the antennal structure is insensitive to the degradation of the adaptation.
  • the radiating loop 14 is a folded loop, comprising at least one U-shaped fold, here three folds 16a, 16b, 16c.
  • a fold is composed of three radiating strips, a radiating strip being connected at each of its two ends by a radiating strip perpendicular thereto, so as to form a U.
  • the folds make it possible in particular to reduce the size of the radiating strips parallel to the horizontal plane, thus limiting a zenith radiation of the antenna structure, that is to say a radiation substantially oriented in the direction of the ZZ axis.
  • a first fold 16a U is located on the upper portion of the radiating loop 14 and is formed of the radiating strips 231a and 231b each connected to one end of the radiating strip 232 and perpendicular thereto.
  • the ends of the radiating strips 231a and 231b not connected to the radiating band 232 are respectively connected to and perpendicular to the radiating strips 233a and 233b.
  • the radiating strips 233a and 233b would be directly connected to form a single long radiating band. The length of this long radiating band parallel to the horizontal plane would lead to excessive zenith radiation.
  • the radiating strips 233a and 233b are located on the same plane, and the radiating band 232 is located on a parallel plane and not coincident with the latter plane.
  • the lateral portions and the connecting portions form a second fold 16b U and a third fold 16c U.
  • the side portions comprise radiating strips 235a and 235b substantially vertical and perpendicular to the radiating strips 233a and 233b.
  • the connecting portions comprise radiating strips 234a and 234b substantially horizontal and perpendicular to the strips 21, 22 metal.
  • the connection portions each further comprise a U-shaped fold acting as a connection with the lateral portions. More specifically, the second U-fold 16b comprises the radiating strip 236a perpendicular to the radiating strip 234a, and the radiating strip 237a perpendicular to the radiating strip 236a and the radiating strip 235a, thus forming a U.
  • the radiating strips 234a and 237a are thus located on two planes parallel to the horizontal plane and not confused. Symmetrically, the radiating strips 236b, 237b and 235b form the third fold 16c in U.
  • the length of the radiating strips 236a and 236b are preferably between one quarter and one third of the length of, respectively, the radiating strip 235a and the radiating band 235b.
  • the second U fold 16b and the third u-shaped fold 16c in particular make it possible to reduce the size of the horizontal radiating strips in order to reduce the zenith radiation of the antenna structure.
  • the U-shaped folds, in particular the first U-fold 16a make it possible to improve the adaptation of the antenna structure and the azimuthal radiation, in particular for frequencies in the upper part of the frequency band.
  • the U-shaped folds also make it possible to reduce the overall size of the antenna structure, in particular along the XX axis (termed lengthwise space) and along the ZZ axis (known as vertical space), while maintaining a length. radiant loop 14 sufficient for the intended application.
  • the vertical bulk of the antenna structure is thus less than one-tenth of the maximum wavelength.
  • the antenna structure will therefore have a vertical footprint of less than 6.3 cm, in practice about 6 cm.
  • antennas of the prior art for the same frequency band have a vertical footprint of about a quarter of the maximum wavelength, in practice between 14 and 16 cm.
  • the two metal strips 21, 22 are connected by a short-circuit element 24. circuit.
  • the element 24 of short circuit is composed of a metal strip, as represented in FIG. 1, with a width between one hundredth of the maximum wavelength and the width of the radiating band 232, or of a plurality strips spread over the width of the antenna structure, symmetrically on either side of the plane defined by the axes XX and ZZ.
  • the short-circuit element 24 is electrically connected to the radiating strip 232, for example by welding. As shown in FIG.
  • the element 24 of short-circuit may consist solely of two small strips connecting firstly the first metal band 21 to the radiating band 232 and secondly the radiating band 232 to the second 22 metal strip, the radiating band 232 then playing in part the role of short circuit element.
  • dielectric spacers (not shown) of low relative permittivity (less than 4) and low tangent loss in the antenna structure, especially between the bands. 237a, 237b and the plane 1 of mass, between the radiating strip 232 and the plane 1 of mass, between the first metal strip 21 and the plane 1 of mass, between the radiating strips 237a and 233a, between the radiating strips 237b and 233b, between the radiating strips 234a and 233a and / or between the radiating strips 234b and 237b.
  • Figures 3 and 4 show respectively a schematic perspective view and a schematic sectional view of an antenna structure according to a second embodiment.
  • the antenna structure according to this second embodiment is distinguished from the first embodiment by the presence of a metal housing 6 disposed on the ground plane 1 and electrically connected thereto.
  • the metal housing 6 delimits a cavity adapted to contain the transmitter / receiver.
  • the metal housing 6 is disposed at the level of the first metal strip 21 and the second metal strip 22: the first metal strip 21 is connected to the positive terminal of the transmitter / receiver 4 via an orifice formed in the metal housing 6 allowing access to the cavity; the second metal strip 22 is connected directly to the metal housing 6, the latter being connected to the ground plane 1.
  • the length, along the axis XX, and the width, along the axis YY, of the metal housing 6 are less than the length and the width of the plane 1 of mass.
  • the height, along the axis ZZ, of the metal housing 6 is less than one-sixth of the vertical dimension of the antenna structure.
  • the height of the housing is limited so as not to significantly modify the radiation performance and the adaptation of the antenna structure.
  • the vertical bulk of the antenna structure in this second embodiment is the same as in the first embodiment, the height of the metal housing 6 being compensated for by a decrease in the length of the metal strips 21, 22.
  • the metal housing 6 furthermore makes it possible to contain signal processing elements, for example a filter 7 and an amplifier 8, as represented in FIG. 4.
  • the amplifier 8 may be a preamplifier.
  • Figures 5 and 6 show respectively a schematic perspective view and a schematic sectional view of an antenna structure according to a third embodiment.
  • the antenna structure according to this third embodiment is distinguished from the second embodiment in particular by a first and a second asymmetry of the antenna structure with respect to the plane defined by the Y-Y and Z-Z axes.
  • the first asymmetry appears at the level of the first metal strip 21: at its end closest to the ground plane 1, the first metal strip 21 is connected to a connecting surface 211 substantially parallel to the horizontal plane and facing the second metal strip 22.
  • This connection surface 211 is connected to the positive terminal of the transceiver 4, directly or via signal processing equipment such as the filter 7 and the amplifier 8.
  • the connection surface 211 has a substantially triangular or trapezoidal shape , a long side of which is connected to the first metal strip 21 and a vertex, if the shape is triangular, or a short side, if the shape is trapezoidal, is connected to the positive terminal of the transceiver 4, here at through the orifice of the metal case 6. This connection surface 211 makes it possible to improve the adaptation of the antennal structure in the frequency band.
  • the second dissymmetry is present on the radiating loop 14.
  • a first pan of the metal structure lying, with respect to the axes YY and ZZ, on the side of the first metal strip 21 has a surface density of current greater than a second part of the structure lying on the side of the second metal strip 22; .
  • This difference in surface current density gives rise to a gain difference in the azimuthal radiation of the antenna structure, the gain being lower on the second side of the structure.
  • the surface density is homogenized by reducing the width, and therefore the area, of the radiating and metallic strips lying in the second part of the metal structure, in particular here the radiating strips 233b, 235b, 237b, 236b, 234b and the second metal strip 22.
  • the width of the radiating strips is progressively reduced at the level of the radiating strip 233b, which comprises a trapezoidal portion 26 whose base is of the same width as the radiating bands of the first panel and whose width decreases until it reaches a reduced width.
  • the trapezoidal portion 26 is then followed by a rectangular portion 28 of reduced width and the second metal strip 22 and the radiating strips 235b, 237b, 236b and 234b are of the same reduced width.
  • the reduced width allows a reduction in the surface area of the radiating strips for the same current passing therethrough, thereby increasing the current surface density which is homogeneous with the current surface density of the elements of the first pan of the antenna structure, thereby improving the omnidirectionality of azimuthal radiation.
  • the antenna structure comprises a parallelepipedal radome surrounding the radiating structure 12, made of a material of low permittivity, for example fiberglass, polyamide or ABS polymer.
  • the radome is designed so that it does not disrupting the radiation performance of the antennal structure, protects it from possible damage, and allows a camouflage thereof.
  • the radome may also be cylindrical, hemispherical, or any other suitable form that does not degrade the performance of the antenna structure. For the sake of clarity, the radome is not shown in the perspective views of FIGS. 1, 3, 5 and 8. In other embodiments, the antenna structure may not include a radome.
  • FIG. 7 shows a schematic perspective view of an antenna structure according to a fourth embodiment of the invention.
  • the antenna structure according to this fourth embodiment differs from the third embodiment in particular by the connecting surface 211, which is fixed to the first metal strip 21 and which is here oriented in a direction opposite to the third embodiment, c that is to say in a direction opposite to the second metal strip 22.
  • the short circuit element is composed of two strips 24a, 24b.
  • the radiating strip 233b is composed of a single trapezoidal portion and does not include a rectangular portion as was the case in the third embodiment. Then, the rectangular strip 237b is trapezoidal in shape, its width increasing from the radiating strip 235b to the strip 236b.
  • the radome 3 is not parallelepipedic but has a shape close to the contours of the antenna structure, thus reducing its bulk. Similarly, the shape of the metal casing 6 and the ground plane 1 is adjusted to the shape of the radome 3.
  • the modifications made by the successively described embodiments each allow an improvement in the performance of the antenna structure, the performance being increasing between the first, second, third and fourth embodiments.
  • the possible frequency band of use of the antenna structure is the widest for the fourth mode of realization and decreases for the other modes.
  • the first embodiment is also the least complex to produce, and the manufacturing complexity increases with the following embodiments, until the fourth embodiment which is the most complex of embodiments presented, for superior performance. .
  • FIGS 8 and 9 schematically show antennal structures respectively according to fifth and sixth embodiments, in which radiating strips and metal strips are composed of a plurality of radiating strips. These radiating strips are metallic and are distributed so as to occupy the same length and the same width as the metal surfaces of the preceding embodiments.
  • the fifth embodiment is based on an antenna structure according to the first embodiment, in which the metal strips and the vertically oriented radiating strips are composed of a plurality of radiating strips, here three radiating strips 28. by radiating band and metal band. Horizontally oriented radiating strips take the form of a metal surface, as in the previous embodiments.
  • all the radiating strips and the metal strips are composed of radiating strips 28.
  • the ground plane 1 is composed of conductor wires arranged in a star pattern starting from the antenna structure.
  • the use of radiating strips is particularly useful for the use of an antenna structure adapted for low frequencies, i.e. for high wavelengths, the dimensions of the antennal structure making it difficult to use the antenna. use of large metal surfaces, for reasons of difficulty of manufacture, cost, resistance of the antennal structure to physical constraints, weather, etc.
  • the radiating strips have a width that can vary between a few thousandths and a few hundredths of the maximum wavelength.
  • the ground plane used depends on the nature of the soil on which the antennal structure, said ground plane, is disposed.
  • FIG. 10 shows a vehicle 32, here an automobile, equipped with an antenna structure according to one embodiment of the invention.
  • the plane 1 of mass of the antenna structure 10 is electrically connected to a metal roof 34 of the vehicle 32, thereby extending the effective surface of the ground plane 1.
  • FIG. 11 is a graph showing the impedance matching of an antenna structure according to the fourth embodiment of the invention, as a function of frequency, in the frequency band 470-700 MHz.
  • Impedance matching is represented by the Standing Wave Ratio (VSWR) of the antenna structure.
  • the stationary wave ratio of an antenna structure is perfect if it is equal to 1.
  • the antenna structure according to the invention aims to obtain preferably a standing wave ratio of between 1 and 1.5.
  • the curve of FIG. 11 shows that in the frequency band 470-700 MHz, the standing wave ratio is less than 1.5 and that it is 1.5 at the 470 MHz and 700 MHz terminals.
  • the impedance matching is thus good for all the frequencies of the frequency band, thus allowing use of the antennal structure for transmission and reception.
  • Fig. 12 is a far-field azimuth radiation pattern of an antenna structure according to one embodiment of the invention.
  • the radiation pattern is represented for a frequency of 550 MHz, that is to say included in the frequency band of 470-700 MHz.
  • Radiation is represented in the azimuthal plane, that is to say along the plane defined by the axes XX and YY, in a configuration where the antenna structure is placed on a circular metal plane 1.5 m in diameter and in an angular position with the angular values are in the range -180 °, 180 °].
  • the 0 ° and 180 ° angles correspond to angular positions on the XX axis, the 0 ° angle being located on the side of the second metal strip 22 and the 180 ° angle being located on the side of the first metal strip 21.
  • the 90 ° and - 90 ° angles correspond to angular positions on the YY axis.
  • the radiation is represented in dBi, which corresponds to the decibel gain of the antenna structure relative to an isotropic antenna.
  • the radiation varies gradually between about -2 dBi for an angle of 0 ° to a value slightly lower than 0 dBi for an angle of 180 °.
  • the variation is identical over the interval] -180 °, 0 °], with a radiation close to OdBi for an angle close to -180 °.
  • the radiation difference of the antennal structure between the 0 ° angle and the 180 ° angle is due to the change in surface density of the current on the first and second panes of the antennal structure, due to the presence the positive terminal of the transmitter at the first metal band 21.
  • Radiation for all frequencies between 470 MHz and 700 MHz have radiation curves, not shown for reasons of clarity, similar to the radiation curve for a frequency of 500 MHz, with slight variations of less than 1 dB.
  • Fig. 13 is a graph showing maximum azimuth gains versus frequency in the 470-700 MHz frequency band of an antenna structure according to one embodiment of the invention.
  • the measurement is the same as the curve of FIG. 12, the radiation being expressed in dBi.
  • the maximum gain is generally the gain measured on the axis XX of the antenna structure, on the side of the first metal strip, that is to say at the level of the 180 ° angular value in Figure 12.
  • the maximum azimuthal gain is stable, between -1 dBi and 0 dBi over the entire frequency band 470-700 MHz.
  • the invention is not limited to the embodiments described.
  • the embodiments presented describe an antenna structure with vertical polarization, but a different orientation of the antenna structure can allow its use for transmission and reception in a different linear polarization, for example oblique or horizontal.
  • the antenna structure has been described for use in a frequency band between 470 MHz and 700 MHz, an antenna structure according to the invention can be used in other frequency bands, the dimensions of which here being adapted accordingly.
  • the use of the antenna structure with dimensions adapted to other frequency bands makes it possible to obtain the same advantages as the embodiments described in these frequency bands.

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Abstract

The invention relates to a wide frequency band antenna structure (10), having polarisation in a favoured direction, termed vertical, suitable for transmission and/or reception of signals of wavelengths between a minimum wavelength and a maximum wavelength. The antenna structure comprises a ground plane (1), extending in a plane perpendicular to said vertical direction, termed the horizontal plane, and a radiating structure comprising a first metallic strip (21) and a second metallic strip (22), arranged vertically and substantially parallel to one another, the second metallic strip (22) being connected to the ground plane (1) and substantially perpendicular to the ground plane (1), and a radiating loop, comprising a plurality of radiating strips, a first end of the loop being connected to the first metallic strip (21) and a second end of the loop being connected to the second metallic strip (22).

Description

STRUCTURE ANTENNAIRE OMNIDIRECTIONNELLE LARGE BANDE  BROADBAND OMNIDIRECTIONAL ANTENNA STRUCTURE
1. Domaine technique de l'invention 1. Technical field of the invention
L'invention concerne une structure antennaire large bande. En particulier, l'invention concerne une structure antennaire large bande à polarisation verticale et à rayonnement omnidirectionnel horizontal, notamment pour application mobile, pour des fréquences comprises entre les bandes basses fréquences LF (pour Low Frequency en anglais) et ultra haute fréquences UHF (pour Ultra High Frequency en anglais).  The invention relates to a broadband antennal structure. In particular, the invention relates to a vertically polarized broadband antenna array with horizontal omnidirectional radiation, in particular for mobile application, for frequencies between the low frequency bands LF (for Low Frequency in English) and ultra high frequency UHF (for Ultra High Frequency in English).
2. Arrière-plan technologique 2. Technological background
Les antennes large bande à polarisation verticale sont utilisées dans diverses applications de télécommunication ou de radiodiffusion, notamment dans le cadre d'applications mobiles, en étant par exemple placées sur des véhicules.  Vertical-polarized broadband antennas are used in various telecommunication or broadcasting applications, particularly in the context of mobile applications, for example by being placed on vehicles.
Les antennes utilisées actuellement pour ces types d'applications mobiles sont généralement des antennes monopôles large bande (monopôle conique, planaire à géométrie variables) intégrées sous un radôme, ou bien des fouets amortis, droits ou inclinés. Pour les applications fixes, les antennes utilisées sont généralement des antennes biconiques ou des antennes fouets équipées d'une cellule d'adaptation pour les fréquences comprises entre les basses fréquences LF et les hautes fréquences HF (pour High Frequency en anglais).  The antennas currently used for these types of mobile applications are generally broadband monopole antennas (conical monopole, planar variable geometry) integrated under a radome, or damped bullets, right or inclined. For fixed applications, the antennas used are generally biconical antennas or whip antennas equipped with an adaptation cell for the frequencies between the low frequencies LF and the high frequencies HF (for High Frequency).
Ces antennes ont pour principal inconvénient de présenter un encombrement vertical proche ou supérieur au quart de la longueur d'onde de la fréquence la plus basse de fonctionnement de l'antenne. Les solutions actuellement proposées pour réduire cet encombrement vertical sont peu efficaces et présentent une forte réduction des gains pour un rayonnement dans le plan horizontal, dit rayonnement azimutal. De plus, le rayonnement azimutal est généralement peu stable en fréquence sur la bande de fréquence des antennes.  These antennas have the main disadvantage of having a vertical footprint near or more than a quarter of the wavelength of the lowest frequency of operation of the antenna. The solutions currently proposed to reduce this vertical space are inefficient and have a large reduction in gains for radiation in the horizontal plane, called azimuthal radiation. In addition, the azimuthal radiation is generally not stable in frequency on the frequency band of the antennas.
3. Objectifs de l'invention 3. Objectives of the invention
L'invention vise à pallier au moins certains des inconvénients des structures antennaires connues.  The invention aims to overcome at least some of the disadvantages of known antennal structures.
En particulier, l'invention vise à fournir, dans au moins un mode de réalisation de l'invention, une structure antennaire à polarisation verticale de faible encombrement vertical. In particular, the invention aims to provide, in at least one embodiment of the invention, a vertical polarization antenna structure of small vertical dimensions.
L'invention vise aussi à fournir, dans au moins un mode de réalisation, une structure antennaire dont les performances sont stables sur une large bande de fréquence.  The invention also aims to provide, in at least one embodiment, an antenna structure whose performance is stable over a wide frequency band.
L'invention vise aussi à fournir, dans au moins un mode de réalisation de l'invention, une structure antennaire à rayonnement omnidirectionnel dans un plan horizontal.  The invention also aims to provide, in at least one embodiment of the invention, an antenna structure with omnidirectional radiation in a horizontal plane.
L'invention vise aussi à fournir, dans au moins un mode de réalisation, une structure antennaire dont le gain azimutal est sensiblement constant sur toute la bande de fréquence de fonctionnement.  The invention also aims to provide, in at least one embodiment, an antenna structure whose azimuth gain is substantially constant over the entire frequency band of operation.
4. Exposé de l'invention 4. Presentation of the invention
Pour ce faire, l'invention concerne une structure antennaire à large bande de fréquence, à polarisation selon une direction privilégiée, dite direction verticale, adaptée pour une émission et/ou une réception de signaux de longueur d'onde comprise entre une longueur d'onde minimale et une longueur d'onde maximale, ladite structure antennaire comprenant :  To this end, the invention relates to an antenna structure with a wide frequency band, with a polarization in a preferred direction, called a vertical direction, adapted for transmitting and / or receiving signals of wavelength between a length of minimum wave and a maximum wavelength, said antennal structure comprising:
un plan de masse, s'étendant selon un plan perpendiculaire à ladite direction verticale, dit plan horizontal,  a ground plane, extending in a plane perpendicular to said vertical direction, said horizontal plane,
une structure rayonnante,  a radiant structure,
caractérisée en ce que ladite structure rayonnante comprend  characterized in that said radiating structure comprises
une première bande métallique et une deuxième bande métallique, disposées verticalement, espacées l'une de l'autre et sensiblement parallèles l'une à l'autre, la deuxième bande métallique étant reliée au plan de masse et sensiblement perpendiculaire au plan de masse, une boucle rayonnante, comprenant une pluralité de bandes rayonnantes, une première extrémité de la boucle rayonnante étant reliée à la première bande métallique et une deuxième extrémité de la boucle rayonnante étant reliée à la deuxième bande métallique, au moins un élément de court-circuit, reliant électriquement la première bande métallique et la deuxième bande métallique dans leurs parties les plus éloignées du plan de masse. a first metal strip and a second metal strip, arranged vertically, spaced from each other and substantially parallel to each other, the second metal strip being connected to the ground plane and substantially perpendicular to the ground plane, a radiant loop, comprising a plurality of radiating strips, a first end of the radiating loop being connected to the first metal strip and a second end of the radiant loop being connected to the second metal strip, at least one short-circuit element, electrically connecting the first metal strip and the second metal strip in their parts the further away from the ground plane.
La longueur d'onde maximale correspond à des signaux de fréquence minimale dans la bande de fréquence, et la longueur d'onde minimale correspond à des signaux de fréquence maximale dans la bande de fréquence. La partie de la bande de fréquence proche de la fréquence minimale est dite partie basse de la bande, et la partie de la bande de fréquence proche de la fréquence maximale est dite partie haute de la bande. Les fréquences minimales et maximales correspondent aux bornes de la bande de fréquence dans laquelle la structure antennaire est destinée à être utilisée sans dégradation des performances. La structure antennaire est adaptée pour fonctionner en dehors de cette bande de fréquence, mais sans garantie de performance. The maximum wavelength corresponds to signals of minimum frequency in the frequency band, and the minimum wavelength corresponds to signals of maximum frequency in the frequency band. The part of the frequency band close to the minimum frequency is called the lower part of the band, and the part of the frequency band close to the maximum frequency is called the upper part of the band. The minimum and maximum frequencies correspond to the terminals of the frequency band in which the antenna structure is intended to be used without degradation of performance. The antennal structure is adapted to operate outside this frequency band, but without guarantee of performance.
On entend par bande métallique et bande rayonnante des éléments métalliques ou une combinaison d'éléments métalliques s'étendant principalement sur deux dimensions, une largeur et une longueur, et ayant une épaisseur négligeable par rapport auxdites largeur et longueur. Notamment, les bandes métalliques et les bandes rayonnantes se distinguent d'un fil qui se caractérise principalement par une seule dimension, sa longueur, et d'un élément en trois dimensions dont aucune des dimensions n'est négligeable par rapport aux deux autres. En particulier, les bandes métalliques et les bandes rayonnantes ont une largeur supérieure à un douzième de la longueur d'onde maximale.  Metal strip and radiating strip are metal elements or a combination of metal elements extending mainly over two dimensions, a width and a length, and having a negligible thickness with respect to said width and length. In particular, the metal strips and the radiating strips are distinguished from a wire which is characterized mainly by a single dimension, its length, and a three-dimensional element of which none of the dimensions is negligible compared to the other two. In particular, the metal strips and the radiating strips have a width greater than one twelfth of the maximum wavelength.
Une structure antennaire selon l'invention a un encombrement faible et permet une émission ou une réception d'un signal sur une large bande de fréquence et de polarisation linéaire. La structure antennaire permet en outre un rayonnement omnidirectionnel dans le plan horizontal, dit rayonnement azimutal, et de gain sensiblement constant sur toute la bande de fréquence de fonctionnement dans ce plan. Le rayonnement de la structure antennaire est optimisé dans le plan horizontal. L'utilisation de la structure antennaire dans une large bande de fréquence d'utilisation est notamment permise grâce à la largeur des bandes métalliques et des bandes rayonnantes.  An antenna structure according to the invention has a small footprint and allows a transmission or reception of a signal over a wide band of frequency and linear polarization. The antenna structure also allows omnidirectional radiation in the horizontal plane, called azimuthal radiation, and substantially constant gain over the entire operating frequency band in this plane. The radiation of the antennal structure is optimized in the horizontal plane. The use of the antennal structure in a wide band of frequency of use is in particular allowed thanks to the width of the metal strips and the radiating strips.
La boucle rayonnante comprend une portion supérieure sensiblement parallèle au plan horizontal, de longueur supérieure à la distance entre la première bande métallique et la deuxième bande métallique, et dont les deux extrémités sont reliées à la première bande métallique et à la deuxième bande métallique par des portions latérales sensiblement verticales puis des portions de liaison sensiblement horizontales. The radiating loop comprises an upper portion substantially parallel to the horizontal plane, of greater length than the distance between the first band metal and the second metal strip, and whose two ends are connected to the first metal strip and the second metal strip by substantially vertical side portions and then substantially horizontal connecting portions.
L'élément de court-circuit permet d'améliorer l'adaptation de la structure antennaire. En outre, le rayonnement omnidirectionnel de la structure antennaire est amélioré dans la partie centrale de la bande de fréquence, dite milieu de bande.  The short-circuit element makes it possible to improve the adaptation of the antenna structure. In addition, the omnidirectional radiation of the antennal structure is improved in the central part of the frequency band, called the band medium.
Les parties des bandes métalliques les plus éloignées du plan de masse désignent sur chaque bande métallique la portion représentant 50% de la surface de la bande métallique, située entre l'extrémité de la bande métallique à laquelle est reliée la boucle rayonnante et le milieu de la bande métallique.  The portions of the metal strips farthest from the ground plane indicate on each metal strip the portion representing 50% of the surface of the metal strip, situated between the end of the metal strip to which the radiating loop is connected to the medium of the metal strip. the metal band.
Avantageusement, le plan de masse s'étendant horizontalement et les bandes métalliques s'étendant verticalement, la polarisation est verticale, le rayonnement est omnidirectionnel dans le plan horizontal, et le gain azimutal est sensiblement constant sur toute la bande de fonctionnement. Une polarisation verticale permet une meilleure efficacité de la structure antennaire en mobilité, par exemple si celle-ci est montée sur le toit d'un véhicule en mouvement, et plus particulièrement à une hauteur proche du niveau du sol.  Advantageously, the ground plane extending horizontally and the metal strips extending vertically, the polarization is vertical, the radiation is omnidirectional in the horizontal plane, and the azimuthal gain is substantially constant over the entire operating band. A vertical polarization allows a better efficiency of the mobile antenna structure, for example if it is mounted on the roof of a moving vehicle, and more particularly at a height near the ground level.
Avantageusement et selon l'invention, la boucle rayonnante est une boucle rayonnante repliée, dans laquelle les bandes rayonnantes forment au moins un repli de section droite en forme de U formé de deux bandes rayonnantes s'étendant selon la direction verticale reliées à leurs extrémités les plus proches du plan de masse par une bande rayonnante, dite base du U, s'étendant selon une direction parallèle au plan horizontal. Advantageously and according to the invention, the radiating loop is a folded radiating loop, in which the radiating strips form at least one u-shaped straight section fold formed of two radiating strips extending in the vertical direction connected at their ends to the closer to the ground plane by a radiating band, said base of the U, extending in a direction parallel to the horizontal plane.
Selon cet aspect de l'invention, le ou les replis en U permettent de réduire la longueur des bandes rayonnantes parallèles au plan horizontal, afin de réduire le rayonnement zénithal, c'est-à-dire le rayonnement ne se propageant pas dans le plan horizontal, dans la partie haute de la bande de fréquence. Les replis en U entraînent une répartition des bandes rayonnantes parallèles au plan horizontal sur plusieurs plans parallèles et non confondus. En outre, le ou les replis en U améliorent l'adaptation en impédance de la structure antennaire, et permettent de réduire l'encombrement de la structure antennaire tout en conservant une même longueur totale des bandes métalliques et des bandes rayonnantes de la structure rayonnante. According to this aspect of the invention, the U-shaped fold or folds make it possible to reduce the length of the radiating strips parallel to the horizontal plane, in order to reduce the zenith radiation, that is to say the radiation that does not propagate in the plane. horizontal, in the upper part of the frequency band. U-folds result in a distribution of radiating bands parallel to the horizontal plane in several parallel and non-coincidental planes. In addition, the U-fold or folds improve the impedance matching of the antenna structure, and reduce the bulk of the antenna. antennal structure while maintaining the same total length of the metal strips and radiating strips of the radiating structure.
Avantageusement, la base du U d'au moins un repli en U est agencée entre la première bande métallique et la deuxième bande métallique, et l'élément de court- circuit est formé au moins en partie par ladite base du U.  Advantageously, the base of the U of at least one U-fold is arranged between the first metal strip and the second metal strip, and the short-circuit element is formed at least in part by said base of the U.
Avantageusement, une structure antennaire selon l'invention présente un encombrement vertical, entre le plan de masse et le point le plus haut de la structure rayonnante, inférieur à un dixième de la longueur d'onde maximale. Advantageously, an antenna structure according to the invention has a vertical space between the ground plane and the highest point of the radiating structure, less than one-tenth of the maximum wavelength.
Selon cet aspect de l'invention, la réduction de l'encombrement antennaire en dessous du dixième de la longueur d'onde maximale permet d'éviter une dégradation des performances dans la partie haute de la bande et permet un rayonnement sans pertes de gain à l'horizon. De plus, la structure antennaire est ainsi moins encombrante que les antennes monopôle quart d'onde classiques, tout en présentant des performances égales ou supérieures en termes de gain et de rayonnement dans le plan horizontal.  According to this aspect of the invention, the reduction of antennal congestion below one-tenth of the maximum wavelength makes it possible to avoid performance degradation in the upper part of the strip and allows radiation without loss of gain at the horizon. In addition, the antenna structure is thus less bulky than conventional monopole quarter wave antennas, while having equal or greater performance in terms of gain and radiation in the horizontal plane.
Avantageusement et selon l'invention, la première bande métallique est adaptée pour être reliée à une borne positive d'un émetteur/récepteur et le plan de masse est adapté pour être relié à une borne négative dudit émetteur/récepteur. Advantageously and according to the invention, the first metal strip is adapted to be connected to a positive terminal of a transmitter / receiver and the ground plane is adapted to be connected to a negative terminal of said transmitter / receiver.
On entend par émetteur/récepteur soit un émetteur seul, soit un récepteur seul, soit un dispositif adapté pour à la fois émettre et recevoir des signaux.  Transmitter / receiver is either a single transmitter or a single receiver, or a device adapted to both transmit and receive signals.
Avantageusement, l'émetteur/récepteur est adapté pour être connecté à la structure antennaire via un câble coaxial dont un conducteur intérieur connecte la borne positive de l'émetteur/récepteur à la première bande métallique et dont un conducteur extérieur connecte la borne négative de l'émetteur/récepteur à la deuxième bande métallique et/ou au plan de masse.  Advantageously, the transceiver is adapted to be connected to the antenna structure via a coaxial cable whose inner conductor connects the positive terminal of the transceiver to the first metal strip and an outer conductor connects the negative terminal of the transceiver. transmitter / receiver to the second metal strip and / or the ground plane.
Selon cet aspect de l'invention, le câble coaxial permet une meilleure adaptation d'impédance de la structure antennaire.  According to this aspect of the invention, the coaxial cable allows a better impedance matching of the antenna structure.
Avantageusement, une structure antennaire selon l'invention comprend un boîtier métallique disposé sur le plan de masse et délimitant une cavité adaptée pour contenir l'émetteur/récepteur, ledit boîtier métallique étant relié électriquement au plan de masse et à la deuxième bande métallique. Advantageously, an antenna structure according to the invention comprises a metal case disposed on the ground plane and defining a cavity adapted to contain the transmitter / receiver, said metal housing being electrically connected to the ground plane and the second metal strip.
La cavité formée par le boîtier métallique permet d'embarquer l'émetteur/récepteur dans la structure antennaire, réduisant ainsi les perturbations entre la structure antennaire et l'émetteur/récepteur, tout en conservant une longueur de connexion faible entre l'émetteur/récepteur et la première bande métallique et le plan de masse. Pour ne pas augmenter l'encombrement vertical de la structure antennaire, les longueurs de la première bande métallique et de la deuxième bande métallique peuvent être réduites pour que l'espace libéré soit occupé, dans une partie de sa hauteur, par le boîtier métallique : la hauteur du boîtier métallique est de préférence inférieure à un sixième de la hauteur totale de la structure antennaire.  The cavity formed by the metal case allows the transceiver to be embedded in the antenna structure, thereby reducing disturbances between the antenna structure and the transceiver, while maintaining a low connection length between the transmitter / receiver and the first metal strip and the ground plane. In order not to increase the vertical bulk of the antenna structure, the lengths of the first metal strip and the second metal strip may be reduced so that the space released is occupied, in part of its height, by the metal case: the height of the metal case is preferably less than one sixth of the total height of the antenna structure.
Avantageusement, le boîtier métallique est adapté pour recevoir des éléments de traitement du signal émis ou reçu par la structure antennaire, par exemple des éléments d'amplification, de filtrage, etc.  Advantageously, the metal casing is adapted to receive processing elements of the signal emitted or received by the antenna structure, for example amplification, filtering elements, etc.
Avantageusement et selon l'invention, la première bande métallique est reliée à l'émetteur/récepteur via une surface de connexion métallique sensiblement parallèle au plan horizontal. Advantageously and according to the invention, the first metal strip is connected to the transmitter / receiver via a metal connection surface substantially parallel to the horizontal plane.
Selon cet aspect de l'invention, la surface de connexion métallique relie une extrémité de la première bande métallique à l'émetteur/récepteur afin d'ajuster l'adaptation d'impédance sur la bande de fréquence souhaitée. De préférence, la surface de connexion métallique a une forme de trapèze, une grande base du trapèze étant reliée à la première bande métallique et une petite base du trapèze étant reliée à l'émetteur/récepteur. Selon plusieurs variantes de l'invention, la surface de connexion s'étend depuis la première bande métallique et en direction de la seconde bande métallique, ou bien s'étend depuis la première bande métallique et dans la direction opposée à la seconde bande métallique. Avantageusement et selon l'invention, la longueur la structure rayonnante entre la borne positive de l'émetteur/récepteur et la liaison du plan de masse et de la deuxième bande métallique est comprise entre la moitié de la longueur d'onde maximale et la longueur d'onde minimale. According to this aspect of the invention, the metal bonding surface connects an end of the first metal strip to the transmitter / receiver to adjust the impedance match to the desired frequency band. Preferably, the metal connection surface has a trapezoidal shape, a large base of the trapezium being connected to the first metal strip and a small base of the trapezium being connected to the transmitter / receiver. According to several variants of the invention, the connecting surface extends from the first metal strip and towards the second metal strip, or extends from the first metal strip and in the opposite direction to the second metal strip. Advantageously and according to the invention, the length of the radiating structure between the positive terminal of the transceiver and the connection of the ground plane and the second metal strip is between half the maximum wavelength and the minimum wavelength.
On entend par longueur de la structure rayonnante la somme de la longueur des bandes métalliques et des bandes rayonnantes formant ladite structure rayonnante.  The length of the radiating structure is understood to mean the sum of the length of the metal strips and the radiating strips forming said radiating structure.
Selon cet aspect de l'invention, cette longueur de structure permet une amélioration de l'adaptation et une maîtrise du rayonnement azimutal sur toute la bande de fréquence.  According to this aspect of the invention, this structural length allows an improvement in the adaptation and control of the azimuthal radiation over the entire frequency band.
Avantageusement et selon l'invention, la largeur de la structure rayonnante est comprise entre un huitième de la longueur d'onde maximale et un tiers de la longueur d'onde minimale. Advantageously and according to the invention, the width of the radiating structure is between one eighth of the maximum wavelength and one third of the minimum wavelength.
Selon cet aspect de l'invention, la largeur de la structure rayonnante, correspondant à la largeur de la bande rayonnante composant la structure rayonnante la plus large, est suffisamment importante pour permettre l'émission/réception dans une large bande de fréquence, et suffisamment faible pour que l'encombrement de la structure antennaire soit limité. Outre la bande de fréquence, la largeur de la structure rayonnante influe aussi sur le rapport d'onde stationnaire, qui est d'autant plus faible dans la partie basse de la bande de fréquence que la largeur de la structure rayonnante est élevée.  According to this aspect of the invention, the width of the radiating structure, corresponding to the width of the radiating band composing the widest radiating structure, is sufficiently large to allow transmission / reception in a wide frequency band, and sufficiently weak so that the congestion of the antennal structure is limited. In addition to the frequency band, the width of the radiating structure also influences the standing wave ratio, which is lower in the lower part of the frequency band as the width of the radiating structure is high.
Selon une autre variante de l'invention, la largeur de la structure rayonnante est inférieure à un huitième de la longueur d'onde maximale. Une telle largeur est moins avantageuse qu'une largeur supérieure à un huitième de la longueur d'onde maximale, notamment en termes d'adaptation de la structure antennaire, mais permet d'obtenir une antenne de taille réduite pour des raisons pratiques ou esthétique lorsque la structure antennaire est utilisée dans des applications dans lesquelles l'adaptation de la structure antennaire est peu critique.  According to another variant of the invention, the width of the radiating structure is less than one-eighth of the maximum wavelength. Such a width is less advantageous than a width greater than one-eighth of the maximum wavelength, in particular in terms of adaptation of the antenna structure, but makes it possible to obtain an antenna of reduced size for practical or aesthetic reasons when the antenna structure is used in applications in which the adaptation of the antennal structure is not critical.
Avantageusement et selon l'invention, la largeur des bandes rayonnantes est variable le long de la boucle rayonnante. Advantageously and according to the invention, the width of the radiating strips is variable along the radiating loop.
Selon cet aspect de l'invention, les bandes rayonnantes ont une largeur variable et donc une surface variable afin de permettre une homogénéisation de la densité surfacique du courant traversant les bandes rayonnantes. Cette homogénéisation de la densité surfacique de courant permet d'améliorer le rayonnement de la structure antennaire et notamment d'homogénéiser le gain de la structure antennaire dans le plan azimutal. According to this aspect of the invention, the radiating strips have a variable width and therefore a variable surface in order to allow homogenization of the density surface of the current passing through the radiating strips. This homogenization of the current surface density makes it possible to improve the radiation of the antenna structure and in particular to homogenize the gain of the antenna structure in the azimuthal plane.
Avantageusement et selon l'invention, le plan de masse a une largeur et une longueur supérieure à la longueur d'onde maximale. Advantageously and according to the invention, the ground plane has a width and a length greater than the maximum wavelength.
Selon cet aspect de l'invention, le rapport d'onde stationnaire de la structure antennaire est amélioré. En pratique, soit le plan de masse a une longueur et une largeur réelles supérieures à la longueur d'onde maximale, soit le plan de masse est relié électriquement à une surface métallique ayant une longueur et une largeur supérieures à la longueur d'onde maximale.  According to this aspect of the invention, the standing wave ratio of the antenna structure is improved. In practice, either the ground plane has a real length and width greater than the maximum wavelength, or the ground plane is electrically connected to a metal surface having a length and a width greater than the maximum wavelength .
Avantageusement, une structure antennaire selon l'invention comprend un radôme entourant la structure rayonnante. Advantageously, an antenna structure according to the invention comprises a radome surrounding the radiating structure.
Selon cet aspect de l'invention, le radôme permet une protection de la structure rayonnante, par exemple contre les intempéries, et permet de cacher la structure antennaire. En outre, le radôme est conçu pour ne pas dégrader le rayonnement de la structure antennaire.  According to this aspect of the invention, the radome allows a protection of the radiating structure, for example against the weather, and allows to hide the antennal structure. In addition, the radome is designed not to degrade the radiation of the antennal structure.
L'invention concerne également un véhicule, caractérisé en ce qu'il est équipé d'une structure antennaire selon l'invention, le plan de masse de la structure antennaire étant fixé en continuité électrique à une surface s'étendant dans un plan sensiblement parallèle au plan horizontal. The invention also relates to a vehicle, characterized in that it is equipped with an antenna structure according to the invention, the ground plane of the antenna structure being fixed in electrical continuity to a surface extending in a substantially parallel plane in the horizontal plane.
Un véhicule selon l'invention est adapté pour émettre et recevoir des signaux par le biais de la structure antennaire, pour des applications en télécommunications notamment. Fixer le plan de masse sur une surface conductrice s'étendant dans un plan sensiblement parallèle au plan horizontal, par exemple le toit du véhicule, permet d'agrandir facilement la surface faisant office de plan de masse.  A vehicle according to the invention is adapted to transmit and receive signals via the antennal structure, for telecommunications applications in particular. Fixing the ground plane on a conductive surface extending in a plane substantially parallel to the horizontal plane, for example the roof of the vehicle, makes it possible to easily enlarge the surface acting as a ground plane.
L'invention concerne également une structure antennaire et un véhicule caractérisés en combinaison par tout ou partie des caractéristiques mentionnées ci- dessus ou ci-après. The invention also relates to an antenna structure and a vehicle characterized in combination by all or some of the features mentioned above or hereafter.
5. Liste des figures 5. 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 :  Other objects, features and advantages of the invention will become apparent on reading the following description given solely by way of non-limiting example and which refers to the appended figures in which:
la figure 1 est une vue schématique en perspective d'une structure antennaire selon un premier mode de réalisation de l'invention,  FIG. 1 is a schematic perspective view of an antenna structure according to a first embodiment of the invention,
la figure 2 est une vue schématique en coupe d'une structure antennaire selon le premier mode de réalisation de l'invention,  FIG. 2 is a diagrammatic sectional view of an antenna structure according to the first embodiment of the invention,
la figure 3 est une vue schématique en perspective d'une structure antennaire selon un deuxième mode de réalisation de l'invention,  FIG. 3 is a schematic perspective view of an antenna structure according to a second embodiment of the invention,
la figure 4 est une vue schématique en coupe d'une structure antennaire selon le deuxième mode de réalisation de l'invention,  FIG. 4 is a diagrammatic sectional view of an antenna structure according to the second embodiment of the invention,
la figure 5 est une vue schématique en perspective d'une structure antennaire selon un troisième mode de réalisation de l'invention,  FIG. 5 is a schematic perspective view of an antenna structure according to a third embodiment of the invention,
la figure 6 est une vue schématique en coupe d'une structure antennaire selon le troisième mode de réalisation de l'invention,  FIG. 6 is a diagrammatic sectional view of an antenna structure according to the third embodiment of the invention,
la figure 7 est une vue schématique en perspective d'une structure antennaire selon un quatrième mode de réalisation de l'invention,  FIG. 7 is a schematic perspective view of an antenna structure according to a fourth embodiment of the invention,
la figure 8 est une vue schématique en perspective d'une structure antennaire selon un cinquième mode de réalisation de l'invention,  FIG. 8 is a schematic perspective view of an antenna structure according to a fifth embodiment of the invention,
la figure 9 est une vue schématique en perspective d'une structure antennaire selon un sixième mode de réalisation de l'invention,  FIG. 9 is a schematic perspective view of an antenna structure according to a sixth embodiment of the invention,
la figure 10 est une vue schématique en perspective d'un véhicule équipé d'une structure antennaire selon un mode de réalisation de l'invention,  FIG. 10 is a schematic perspective view of a vehicle equipped with an antenna structure according to one embodiment of the invention,
la figure 11 est une courbe représentant l'adaptation d'impédance d'une structure antennaire selon un mode de réalisation de l'invention en fonction de la fréquence, dans la bande de fréquence 470-700 MHz,  FIG. 11 is a curve representing the impedance matching of an antenna structure according to one embodiment of the invention as a function of frequency, in the frequency band 470-700 MHz,
la figure 12 est un diagramme de rayonnement azimutal d'une structure antennaire selon un mode de réalisation de l'invention pour une fréquence de 550 MHz, FIG. 12 is an azimuthal radiation pattern of an antenna structure according to one embodiment of the invention for a frequency of 550 MHz,
la figure 13 est une courbe représentant les gains azimutaux maximum en fonction de la fréquence, dans la bande de fréquence 470-700 MHz, d'une structure antennaire selon un mode de réalisation de l'invention. 6. Description détaillée d'un mode de réalisation de l'invention  FIG. 13 is a curve representing the maximum azimuthal gains as a function of the frequency, in the frequency band 470-700 MHz, of an antenna structure according to one embodiment of the invention. 6. 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.  The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference relates to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments may also be combined to provide other embodiments.
La figure 1 représente schématiquement et en perspective une structure 10 antennaire selon un premier mode de réalisation de l'invention. La figure 2 représente schématiquement une coupe de la structure 10 antennaire selon ce premier mode de réalisation, selon un plan de coupe définit par les axes X-X et Z-Z tel que représenté sur la figure 1. Figure 1 shows schematically and in perspective an antenna structure according to a first embodiment of the invention. FIG. 2 diagrammatically represents a section of the antenna structure according to this first embodiment, according to a section plane defined by the X-X and Z-Z axes as represented in FIG.
La structure 10 antennaire est adaptée pour émettre ou recevoir des signaux dans une large bande de fréquence entre une fréquence minimale, associée à une longueur d'onde maximale, et une fréquence maximale, associée à une longueur d'onde minimale. Ces fréquences minimales et maximales sont les fréquences entre lesquelles la structure 10 antennaire est prévue pour fonctionner avec des performances optimales. Ainsi, la structure 10 antennaire peut fonctionner en dehors de cette bande de fréquence, sans que les performances soient toutefois assurées, le dimensionnement de la structure 10 antennaire étant lié à la bande de fréquence souhaitée.  The antenna structure is adapted to transmit or receive signals in a wide frequency band between a minimum frequency associated with a maximum wavelength and a maximum frequency associated with a minimum wavelength. These minimum and maximum frequencies are the frequencies between which the antenna structure is intended to operate with optimum performance. Thus, the antenna structure can operate outside this frequency band, but the performance is not assured, since the design of the antenna structure is related to the desired frequency band.
Par exemple, la structure 10 antennaire peut être configurée pour une application large bande entre une fréquence minimale de 470 MHz et une fréquence maximale de 700 MHz. Ces deux valeurs sont donc associées à une longueur d'onde minimale d'environ 43 cm et une longueur d'onde maximale d'environ 63 cm.  For example, the antenna structure can be configured for broadband application between a minimum frequency of 470 MHz and a maximum frequency of 700 MHz. These two values are therefore associated with a minimum wavelength of approximately 43 cm and a maximum wavelength of approximately 63 cm.
La structure 10 antennaire comprend un plan 1 de masse sur lequel est reliée une structure 12 rayonnante. Le plan 1 de masse définit un plan, dit plan horizontal, comprenant deux axes X-X et Y-Y perpendiculaires entre eux, et définit en outre un axe Z-Z perpendiculaire au plan horizontal. La structure 12 rayonnante comprend deux bandes métalliques, une première bande 21 métallique et une deuxième bande 22 métallique, dont les extrémités les plus éloignées du plan 1 de masse sont reliées à une boucle 14 rayonnante. La boucle 14 rayonnante est composée d'une pluralité de bandes rayonnantes, ici treize, référencées 231a, 233a, 234a, 235a, 236a, 237a, 231b, 233b, 234b, 235b, 236b, 237b et 232, permettant de relier les extrémités des deux bandes 21, 22 métalliques. La structure 10 antennaire est destinée à l'émission et/ou la réception de signaux de polarisation préférentiellement verticale, c'est-à-dire orientée selon l'axe Z-Z, avec un rayonnement omnidirectionnel azimutal, c'est-à-dire que les signaux se propagent sensiblement parallèlement au plan horizontal. The antenna structure comprises a ground plane 1 to which is connected a radiating structure 12. The plane 1 of mass defines a plane, called horizontal plane, comprising two axes XX and YY perpendicular to each other, and further defines an axis ZZ perpendicular to the horizontal plane. The radiating structure 12 comprises two metal strips, a first metal strip 21 and a second metal strip 22, the ends farthest from the ground plane 1 are connected to a radiating loop 14. The radiating loop 14 is composed of a plurality of radiating bands, here thirteen, referenced 231a, 233a, 234a, 235a, 236a, 237a, 231b, 233b, 234b, 235b, 236b, 237b and 232, making it possible to connect the ends of the two metal strips 21, 22. The antenna structure is intended for the emission and / or reception of preferably vertical polarization signals, ie oriented along the ZZ axis, with azimuthal omnidirectional radiation, that is to say that the signals propagate substantially parallel to the horizontal plane.
Les deux bandes 21, 22 métalliques sont disposées sensiblement perpendiculairement au plan 1 de masse, donc disposés sensiblement verticalement, et sont parallèles l'une à l'autre. La deuxième bande 22 métallique est reliée au plan 1 de masse de façon à être en continuité électrique, par exemple par soudage, vissage, rivetage, et la première bande 21 métallique est reliée à une borne positive d'un émetteur/récepteur 4, une borne négative de l'émetteur/récepteur 4 étant reliée au plan 1 de masse, les bornes positive et négative étant de préférence situées dans le plan défini par l'axe X-X et l'axe Z-Z. Les parties supérieures des deux bandes 21, 22 métalliques, c'est-à-dire les parties les plus éloignées du plan 1 de masse, sont reliées par un élément 24 de court-circuit. La partie inférieure de la première bande 21 métallique, c'est-à-dire la partie la plus proche du plan 1 de masse, à laquelle est reliée la borne positive de l'émetteur/récepteur 4, est à une distance du plan 1 de masse inférieure à un centième de la longueur d'onde minimale. La distance séparant la première bande 21 métallique de la deuxième bande 22 métallique est inférieure à un dixième de la longueur d'onde minimale. La longueur de la deuxième bande 22 métallique est comprise entre un douzième et un dixième de la longueur d'onde minimale, afin d'assurer un rayonnement optimal sur toute la bande de fréquence.  The two metal strips 21, 22 are disposed substantially perpendicularly to the ground plane 1, and therefore arranged substantially vertically, and are parallel to one another. The second metal strip 22 is connected to the ground plane 1 so as to be electrically continuous, for example by welding, screwing, riveting, and the first metal strip 21 is connected to a positive terminal of a transmitter / receiver 4, a negative terminal of the transmitter / receiver 4 being connected to the ground plane 1, the positive and negative terminals being preferably located in the plane defined by the axis XX and the ZZ axis. The upper parts of the two metal strips 21, 22, that is to say the parts farthest from the ground plane 1, are connected by a short-circuit element 24. The lower part of the first metal strip 21, that is to say the part closest to the ground plane 1, to which the positive terminal of the transmitter / receiver 4 is connected, is at a distance from the plane 1 of mass less than one hundredth of the minimum wavelength. The distance separating the first metal band 21 from the second metal band 22 is less than one-tenth of the minimum wavelength. The length of the second metal strip 22 is between one twelfth and one tenth of the minimum wavelength, in order to ensure optimum radiation over the entire frequency band.
Selon les modes de réalisation, l'émetteur/récepteur 4 peut être par exemple uniquement un émetteur, uniquement un récepteur ou un dispositif groupant les fonctions d'émetteur et de récepteur. Le plan 1 de masse est ici représenté d'une taille équivalente à l'encombrement de la structure 12 rayonnante selon les axes X-X et Y-Y. De préférence, le plan 1 de masse est relié électriquement à une surface sensiblement horizontale de taille plus importante, de préférence de largeur et de longueur supérieure à la longueur d'onde maximale, par exemple le toit d'un véhicule comme représenté en référence à la figure 10. According to the embodiments, the transmitter / receiver 4 may be for example only a transmitter, only a receiver or a device grouping the transmitter and receiver functions. The plane 1 of mass is here represented of a size equivalent to the size of the structure 12 radiating along the axes XX and YY. Preferably, the ground plane 1 is electrically connected to a substantially horizontal surface of greater size, preferably of greater width and length than the maximum wavelength, for example the roof of a vehicle as shown with reference to FIG. Figure 10.
La boucle 14 rayonnante comprend une portion supérieure, ici composée des bandes rayonnantes 231a, 231b, 232, 233a et 233b. Cette portion supérieure est reliée à des portions latérales sensiblement verticales, composé respectivement des bandes rayonnantes 235a et 235b, lesdites portions latérales étant reliées à des portions de liaison respectivement composées des bandes rayonnantes 234a, 236a, 237a et des bandes rayonnantes 234b, 236b, 237b, lesdites portions de liaison étant reliées aux deux bandes 21, 22 métalliques, fermant ainsi la boucle 14 rayonnante. Les bandes rayonnantes 232, 233a, 233b, 234a, 234b, 237a, 237b sont sensiblement horizontales. Les bandes rayonnantes 231a, 231b, 235a, 235b, 236a, 236b sont sensiblement verticales. Dans ce premier mode de réalisation, la boucle 14 rayonnante est ainsi symétrique de part et d'autre du plan défini par les axes Y-Y et Z-Z.  The radiating loop 14 comprises an upper portion, here composed of the radiating strips 231a, 231b, 232, 233a and 233b. This upper portion is connected to substantially vertical lateral portions, respectively composed of radiating strips 235a and 235b, said lateral portions being connected to connecting portions respectively composed of radiating strips 234a, 236a, 237a and radiating strips 234b, 236b, 237b said connecting portions being connected to the two metal strips 21, 22, thereby closing the radiating loop 14. The radiating strips 232, 233a, 233b, 234a, 234b, 237a, 237b are substantially horizontal. The radiating strips 231a, 231b, 235a, 235b, 236a, 236b are substantially vertical. In this first embodiment, the radiating loop 14 is thus symmetrical on either side of the plane defined by the Y-Y and Z-Z axes.
Les bandes rayonnantes ont chacune une largeur définie selon l'axe Y-Y et une longueur définie soit selon l'axe X-X pour les bandes rayonnantes orientées sensiblement horizontalement, soit selon l'axe Z-Z pour les bandes rayonnantes orientées sensiblement verticalement. Par extension, la largeur de la boucle 14 rayonnante est définie par la largeur de la bande rayonnante la plus large parmi celles formant la boucle 14 rayonnante, et la longueur de la boucle 14 rayonnante est définie par la somme des longueurs des bandes rayonnantes formant la boucle 14 rayonnante. Dans ce premier mode de réalisation, les bandes rayonnantes ont toutes la même largeur. La longueur de la structure 12 rayonnante est la somme de la longueur de la boucle 14 rayonnante et des longueurs selon l'axe Z-Z de la première 21 bande métallique et de la deuxième bande 22 métallique, c'est-à-dire la longueur de la structure 12 rayonnante entre la borne positive de l'émetteur/récepteur 4 et la liaison du plan 1 de masse et de la deuxième bande 22 métallique. En l'occurrence, dans ce mode de réalisation, la longueur de la structure 12 rayonnante est comprise entre la moitié de la longueur d'onde maximale, soit 63/2=31,5 cm environ, et la longueur d'onde minimale soit 43 cm environ. La largeur de la structure 12 rayonnante est comprise entre un huitième de la longueur d'onde maximale, soit 63/8=7,9 cm environ, et un tiers de la longueur d'onde minimale, soit 43/3=14,3 cm environ. Selon un autre mode de réalisation de l'invention, la largeur de la structure 12 rayonnante est inférieure à un huitième de la longueur d'onde maximale. L'adaptation de la structure 10 antennaire est ainsi moins optimisée, mais permet de réduire l'encombrement de la structure 10 antennaire lorsque l'utilisation de la structure 10 antennaire est peu sensible à la dégradation de l'adaptation. The radiating strips each have a width defined along the axis YY and a length defined either along the axis XX for the radiating strips oriented substantially horizontally, or along the axis ZZ for the radiating strips oriented substantially vertically. By extension, the width of the radiating loop 14 is defined by the width of the widest radiating band among those forming the radiating loop 14, and the length of the radiating loop 14 is defined by the sum of the lengths of the radiating bands forming the 14 radiant loop. In this first embodiment, the radiating strips all have the same width. The length of the radiating structure 12 is the sum of the length of the radiating loop 14 and the lengths along the axis ZZ of the first metal strip 21 and the second metal strip 22, that is to say the length of the the radiating structure 12 between the positive terminal of the transceiver 4 and the connection of the ground plane 1 and the second metal strip 22. In this case, in this embodiment, the length of the radiating structure 12 is between half of the maximum wavelength, ie 63/2 = about 31.5 cm, and the minimum wavelength is about 43 cm. The width of the radiating structure 12 is between one eighth of the maximum wavelength, ie 63/8 = 7.9 cm approximately, and one third of the minimum wavelength, ie 43/3 = 14.3 about cm. According to another embodiment of the invention, the width of the radiating structure 12 is less than one-eighth of the maximum wavelength. The adaptation of the antenna structure is thus less optimized, but makes it possible to reduce the size of the antenna structure when the use of the antennal structure is insensitive to the degradation of the adaptation.
La boucle 14 rayonnante est une boucle repliée, comprenant au moins un repli en forme de U, ici trois replis 16a, 16b, 16c. Un repli est composé de trois bandes rayonnantes, une bande rayonnante étant reliée à chacune de ses deux extrémités par une bande rayonnante perpendiculaire à celle-ci, de façon à former un U. Les replis permettent notamment de réduire la taille des bandes rayonnantes parallèles au plan horizontal, limitant ainsi un rayonnement zénithal de la structure 10 antennaire, c'est-à- dire un rayonnement sensiblement orienté dans la direction de l'axe Z-Z.  The radiating loop 14 is a folded loop, comprising at least one U-shaped fold, here three folds 16a, 16b, 16c. A fold is composed of three radiating strips, a radiating strip being connected at each of its two ends by a radiating strip perpendicular thereto, so as to form a U. The folds make it possible in particular to reduce the size of the radiating strips parallel to the horizontal plane, thus limiting a zenith radiation of the antenna structure, that is to say a radiation substantially oriented in the direction of the ZZ axis.
Par exemple, un premier repli 16a en U est situé sur la portion supérieure de la boucle 14 rayonnante et est formé des bandes rayonnantes 231a et 231b chacune reliée à une extrémité de la bande rayonnante 232 et perpendiculaire à celle-ci. Les extrémités des bandes rayonnantes 231a et 231b non-reliées à la bande rayonnante 232 sont reliées respectivement aux bandes rayonnantes 233a et 233b et perpendiculaires à celles-ci. Sans ce premier repli en U, les bandes rayonnantes 233a et 233b seraient directement reliée pour former une unique longue bande rayonnante. La longueur de cette longue bande rayonnante parallèle au plan horizontal entraînerait un rayonnement zénithal trop important. Avec ce premier repli en U, les bandes rayonnantes 233a et 233b sont situées sur un même plan, et la bande rayonnante 232 est située sur un plan parallèle et non confondu avec ce dernier plan.  For example, a first fold 16a U is located on the upper portion of the radiating loop 14 and is formed of the radiating strips 231a and 231b each connected to one end of the radiating strip 232 and perpendicular thereto. The ends of the radiating strips 231a and 231b not connected to the radiating band 232 are respectively connected to and perpendicular to the radiating strips 233a and 233b. Without this first U-fold, the radiating strips 233a and 233b would be directly connected to form a single long radiating band. The length of this long radiating band parallel to the horizontal plane would lead to excessive zenith radiation. With this first U-fold, the radiating strips 233a and 233b are located on the same plane, and the radiating band 232 is located on a parallel plane and not coincident with the latter plane.
De la même façon, les portions latérales et les portions de liaison forment un deuxième repli 16b en U et un troisième repli 16c en U. Les portions latérales comprennent des bandes rayonnantes 235a et 235b sensiblement verticales et perpendiculaires aux bandes rayonnantes 233a et 233b. Les portions de liaison comprennent des bandes rayonnantes 234a et 234b sensiblement horizontales et perpendiculaires aux bandes 21, 22 métalliques. Les portions de liaison comprennent en outre chacun un repli en U faisant office de liaison avec les portions latérales. Plus précisément, le deuxième repli 16b en U comprend la bande rayonnante 236a perpendiculaires à la bande rayonnante 234a, et la bande rayonnante 237a perpendiculaire à la bande rayonnante 236a et à la bande rayonnante 235a, formant ainsi un U. Les bandes rayonnantes 234a et 237a sont ainsi situées sur deux plans parallèles au plan horizontal et non confondus. De façon symétrique, les bandes rayonnantes 236b, 237b et 235b forment le troisième repli 16c en U. La longueur des bandes rayonnantes 236a et 236b sont de préférence comprises entre un quart et un tiers de la longueur de, respectivement, la bande rayonnante 235a et la bande rayonnante 235b. In the same way, the lateral portions and the connecting portions form a second fold 16b U and a third fold 16c U. The side portions comprise radiating strips 235a and 235b substantially vertical and perpendicular to the radiating strips 233a and 233b. The connecting portions comprise radiating strips 234a and 234b substantially horizontal and perpendicular to the strips 21, 22 metal. The connection portions each further comprise a U-shaped fold acting as a connection with the lateral portions. More specifically, the second U-fold 16b comprises the radiating strip 236a perpendicular to the radiating strip 234a, and the radiating strip 237a perpendicular to the radiating strip 236a and the radiating strip 235a, thus forming a U. The radiating strips 234a and 237a are thus located on two planes parallel to the horizontal plane and not confused. Symmetrically, the radiating strips 236b, 237b and 235b form the third fold 16c in U. The length of the radiating strips 236a and 236b are preferably between one quarter and one third of the length of, respectively, the radiating strip 235a and the radiating band 235b.
Comme pour le premier repli 16a en U, le deuxième repli 16b en U et le troisième repli 16c en U permettent notamment de réduire la taille des bandes rayonnantes horizontales pour réduire le rayonnement zénithal de la structure 10 antennaire. En outre, les replis en U, notamment le premier repli 16a en U, permettent d'améliorer l'adaptation de la structure 10 antennaire et le rayonnement azimutal, en particulier pour des fréquences dans la partie haute de la bande de fréquence.  As for the first U-shaped fold 16a, the second U fold 16b and the third u-shaped fold 16c in particular make it possible to reduce the size of the horizontal radiating strips in order to reduce the zenith radiation of the antenna structure. In addition, the U-shaped folds, in particular the first U-fold 16a, make it possible to improve the adaptation of the antenna structure and the azimuthal radiation, in particular for frequencies in the upper part of the frequency band.
Les replis en U permettent aussi de réduire l'encombrement de l'ensemble de la structure 10 antennaire, notamment selon l'axe X-X (dit encombrement en longueur) et selon l'axe Z-Z (dit encombrement vertical), tout en conservant une longueur de boucle 14 rayonnante suffisante pour l'application visée. Notamment, l'encombrement vertical de la structure 10 antennaire est ainsi inférieur à un dixième de la longueur d'onde maximale. Pour une fréquence minimale de 470 MHz, associée à une longueur d'onde maximale de 63 cm, la structure 10 antennaire aura donc un encombrement vertical inférieur à 6,3 cm, en pratique environ 6cm. Par comparaison, les antennes de l'art antérieur pour la même bande de fréquence ont un encombrement vertical d'environ un quart de la longueur d'onde maximale, soit en pratique entre 14 et 16 cm.  The U-shaped folds also make it possible to reduce the overall size of the antenna structure, in particular along the XX axis (termed lengthwise space) and along the ZZ axis (known as vertical space), while maintaining a length. radiant loop 14 sufficient for the intended application. In particular, the vertical bulk of the antenna structure is thus less than one-tenth of the maximum wavelength. For a minimum frequency of 470 MHz, associated with a maximum wavelength of 63 cm, the antenna structure will therefore have a vertical footprint of less than 6.3 cm, in practice about 6 cm. By comparison, antennas of the prior art for the same frequency band have a vertical footprint of about a quarter of the maximum wavelength, in practice between 14 and 16 cm.
Pour permettre d'améliorer l'adaptation de la structure 10 antennaire et le rayonnement azimutal pour des fréquences dans la partie centrale de la bande de fréquence, les deux bandes 21, 22 métalliques sont reliées par un élément 24 de court- circuit. L'élément 24 de court-circuit est composé d'une bandelette métallique, comme représenté sur la figure 1, de largeur comprise entre un centième de la longueur d'onde maximale et la largeur de la bande rayonnante 232, ou d'une pluralité de bandelettes réparties sur la largeur de la structure 10 antennaire, symétriquement de part et d'autre du plan défini par les axes X-X et Z-Z. Dans ce mode de réalisation, l'élément 24 de court-circuit est électriquement relié à la bande rayonnante 232, par exemple par soudage. Comme représenté sur la figure 2, l'élément 24 de court-circuit peut être composé uniquement de deux petites bandelettes reliant d'une part la première bande 21 métallique à la bande rayonnante 232 et d'autre part la bande rayonnante 232 à la deuxième bande 22 métallique, la bande rayonnante 232 jouant alors en partie le rôle d'élément de court-circuit. In order to improve the adaptation of the antenna structure and the azimuth radiation for frequencies in the central part of the frequency band, the two metal strips 21, 22 are connected by a short-circuit element 24. circuit. The element 24 of short circuit is composed of a metal strip, as represented in FIG. 1, with a width between one hundredth of the maximum wavelength and the width of the radiating band 232, or of a plurality strips spread over the width of the antenna structure, symmetrically on either side of the plane defined by the axes XX and ZZ. In this embodiment, the short-circuit element 24 is electrically connected to the radiating strip 232, for example by welding. As shown in FIG. 2, the element 24 of short-circuit may consist solely of two small strips connecting firstly the first metal band 21 to the radiating band 232 and secondly the radiating band 232 to the second 22 metal strip, the radiating band 232 then playing in part the role of short circuit element.
Afin d'améliorer la rigidité de la structure 10 antennaire, il est possible d'ajouter des entretoises diélectriques (non représentées) de faible permittivité relative (inférieure à 4) et de faible tangente de perte dans la structure 10 antennaire, notamment entre les bandes rayonnantes 237a, 237b et le plan 1 de masse, entre la bande rayonnante 232 et le plan 1 de masse, entre la première bande 21 métallique et le plan 1 de masse, entre les bandes rayonnantes 237a et 233a, entre les bandes rayonnantes 237b et 233b, entre les bandes rayonnantes 234a et 233a et/ou entre les bandes rayonnantes 234b et 237b.  In order to improve the rigidity of the antenna structure, it is possible to add dielectric spacers (not shown) of low relative permittivity (less than 4) and low tangent loss in the antenna structure, especially between the bands. 237a, 237b and the plane 1 of mass, between the radiating strip 232 and the plane 1 of mass, between the first metal strip 21 and the plane 1 of mass, between the radiating strips 237a and 233a, between the radiating strips 237b and 233b, between the radiating strips 234a and 233a and / or between the radiating strips 234b and 237b.
Les figures 3 et 4 représentent respectivement une vue schématique en perspective et une vue schématique en coupe d'une structure 10 antennaire selon un deuxième mode de réalisation. La structure 10 antennaire selon ce deuxième mode de réalisation se distingue du premier mode de réalisation par la présence d'un boitier 6 métallique, disposé sur le plan 1 de masse et relié électriquement à celui-ci. Le boitier 6 métallique délimite une cavité adaptée pour contenir l'émetteur/récepteur. Le boitier 6 métallique est disposé au niveau de la première bande 21 métallique et de la deuxième bande 22 métallique : la première bande 21 métallique est reliée à la borne positive de l'émetteur/récepteur 4 via un orifice formé dans le boitier 6 métallique permettant l'accès à la cavité ; la deuxième bande 22 métallique est reliée directement au boitier 6 métallique, celui-ci étant relié au plan 1 de masse. La longueur, selon l'axe X-X, et la largeur, selon l'axe Y-Y, du boitier 6 métallique, sont inférieures à la longueur et à la largeur du plan 1 de masse. La hauteur, selon l'axe Z-Z, du boitier 6 métallique est inférieure à un sixième de l'encombrement vertical de la structure 10 antennaire. La hauteur du boitier est limitée pour ne pas modifier significativement les performances en rayonnement et en adaptation de la structure 10 antennaire. L'encombrement vertical de la structure 10 antennaire dans ce deuxième mode de réalisation est le même que dans le premier mode de réalisation, la hauteur du boitier 6 métallique étant compensée par une diminution de la longueur des bandes 21, 22 métalliques. Figures 3 and 4 show respectively a schematic perspective view and a schematic sectional view of an antenna structure according to a second embodiment. The antenna structure according to this second embodiment is distinguished from the first embodiment by the presence of a metal housing 6 disposed on the ground plane 1 and electrically connected thereto. The metal housing 6 delimits a cavity adapted to contain the transmitter / receiver. The metal housing 6 is disposed at the level of the first metal strip 21 and the second metal strip 22: the first metal strip 21 is connected to the positive terminal of the transmitter / receiver 4 via an orifice formed in the metal housing 6 allowing access to the cavity; the second metal strip 22 is connected directly to the metal housing 6, the latter being connected to the ground plane 1. The length, along the axis XX, and the width, along the axis YY, of the metal housing 6 are less than the length and the width of the plane 1 of mass. The height, along the axis ZZ, of the metal housing 6 is less than one-sixth of the vertical dimension of the antenna structure. The height of the housing is limited so as not to significantly modify the radiation performance and the adaptation of the antenna structure. The vertical bulk of the antenna structure in this second embodiment is the same as in the first embodiment, the height of the metal housing 6 being compensated for by a decrease in the length of the metal strips 21, 22.
Le boitier 6 métallique permet en outre de contenir des éléments de traitement du signal, par exemple un filtre 7 et un amplificateur 8, comme représenté figure 4. Pour une utilisation de la structure antennaire en réception, l'amplificateur 8 peut être un préamplificateur. Les figures 5 et 6 représentent respectivement une vue schématique en perspective et une vue schématique en coupe d'une structure 10 antennaire selon un troisième mode de réalisation. La structure 10 antennaire selon ce troisième mode de réalisation se distingue du deuxième mode de réalisation notamment par une première et une deuxième dissymétrie de la structure 10 antennaire par rapport au plan défini par les axes Y-Y et Z-Z.  The metal housing 6 furthermore makes it possible to contain signal processing elements, for example a filter 7 and an amplifier 8, as represented in FIG. 4. For use of the antennal structure in reception, the amplifier 8 may be a preamplifier. Figures 5 and 6 show respectively a schematic perspective view and a schematic sectional view of an antenna structure according to a third embodiment. The antenna structure according to this third embodiment is distinguished from the second embodiment in particular by a first and a second asymmetry of the antenna structure with respect to the plane defined by the Y-Y and Z-Z axes.
La première dissymétrie apparaît au niveau de la première bande 21 métallique : au niveau de son extrémité la plus proche du plan 1 de masse, la première bande 21 métallique est reliée à une surface 211 de connexion sensiblement parallèle au plan horizontal et orientée vers la deuxième bande 22 métallique. Cette surface 211 de connexion est connectée à la borne positive de l'émetteur/récepteur 4, directement ou via des équipements de traitement du signal comme le filtre 7 et l'amplificateur 8. La surface 211 de connexion présente une forme sensiblement triangulaire ou trapézoïdale, dont un grand côté est reliée à la première bande 21 métallique et un sommet, si la forme est triangulaire, ou un petit côté, si la forme est trapézoïdale, est connecté à la borne positive de l'émetteur/récepteur 4, ici à travers l'orifice du boitier 6 métallique. Cette surface 211 de connexion permet d'améliorer l'adaptation de la structure 10 antennaire dans la bande de fréquence. The first asymmetry appears at the level of the first metal strip 21: at its end closest to the ground plane 1, the first metal strip 21 is connected to a connecting surface 211 substantially parallel to the horizontal plane and facing the second metal strip 22. This connection surface 211 is connected to the positive terminal of the transceiver 4, directly or via signal processing equipment such as the filter 7 and the amplifier 8. The connection surface 211 has a substantially triangular or trapezoidal shape , a long side of which is connected to the first metal strip 21 and a vertex, if the shape is triangular, or a short side, if the shape is trapezoidal, is connected to the positive terminal of the transceiver 4, here at through the orifice of the metal case 6. This connection surface 211 makes it possible to improve the adaptation of the antennal structure in the frequency band.
La deuxième dissymétrie est présente sur la boucle 14 rayonnante. Dans les premier et deuxième modes de réalisation de l'invention, du fait de la connexion de la borne positive de l'émetteur/récepteur 4 à la première bande 21 métallique et de la connexion de la deuxième bande 22 métallique à la masse, un premier pan de la structure métallique se situant, par rapport aux axes Y-Y et Z-Z, du côté de la première bande 21 métallique, a une densité surfacique de courant supérieure à un deuxième pan de la structure se situant du côté de la deuxième bande 22 métallique. Cette différence de densité surfacique de courant engendre une différence de gain dans le rayonnement azimutal de la structure 10 antennaire, le gain étant inférieur du côté du deuxième pan de la structure. Ainsi, dans ce troisième mode de réalisation, la densité surfacique est homogénéisée par la diminution de la largeur, et donc de la surface, des bandes rayonnantes et métalliques se situant dans le deuxième pan de la structure métallique, notamment ici les bandes rayonnantes 233b, 235b, 237b, 236b, 234b et la deuxième bande 22 métallique. La largeur des bandes rayonnantes est réduite progressivement au niveau de la bande rayonnante 233b, qui comprend une portion 26 trapézoïdale dont la base est de la même largeur que les bandes rayonnantes du premier pan et dont la largeur décroit jusqu'à atteindre une largeur réduite. La portion 26 trapézoïdale est ensuite suivie d'une portion 28 rectangulaire de largeur réduite et la deuxième bande 22 métallique et les bandes rayonnantes 235b, 237b, 236b et 234b sont de même largeur réduite. La largeur réduite permet une diminution de la surface des bandes rayonnantes pour le même courant les traversant, augmentant ainsi la densité surfacique de courant qui est homogène avec la densité surfacique de courant des éléments du premier pan de la structure 10 antennaire, améliorant ainsi l'omnidirectionnalité du rayonnement azimutal.  The second dissymmetry is present on the radiating loop 14. In the first and second embodiments of the invention, because of the connection of the positive terminal of the transmitter / receiver 4 to the first metal strip 21 and the connection of the second metal strip 22 to ground, a first pan of the metal structure lying, with respect to the axes YY and ZZ, on the side of the first metal strip 21, has a surface density of current greater than a second part of the structure lying on the side of the second metal strip 22; . This difference in surface current density gives rise to a gain difference in the azimuthal radiation of the antenna structure, the gain being lower on the second side of the structure. Thus, in this third embodiment, the surface density is homogenized by reducing the width, and therefore the area, of the radiating and metallic strips lying in the second part of the metal structure, in particular here the radiating strips 233b, 235b, 237b, 236b, 234b and the second metal strip 22. The width of the radiating strips is progressively reduced at the level of the radiating strip 233b, which comprises a trapezoidal portion 26 whose base is of the same width as the radiating bands of the first panel and whose width decreases until it reaches a reduced width. The trapezoidal portion 26 is then followed by a rectangular portion 28 of reduced width and the second metal strip 22 and the radiating strips 235b, 237b, 236b and 234b are of the same reduced width. The reduced width allows a reduction in the surface area of the radiating strips for the same current passing therethrough, thereby increasing the current surface density which is homogeneous with the current surface density of the elements of the first pan of the antenna structure, thereby improving the omnidirectionality of azimuthal radiation.
Les figures 2, 4 et 6 représentent schématiquement en coupe le premier, le deuxième et le troisième mode de réalisation. Dans ces trois modes de réalisation, la structure 10 antennaire comprend un radôme parallélépipédique entourant la structure 12 rayonnante, fabriqué dans un matériau de faible permittivité, par exemple en fibre de verre, polyamide ou en polymère ABS. Le radôme est conçu de sorte à ne pas perturber les performances en rayonnement de la structure 10 antennaire, permet de protéger celle-ci d'éventuelles dégradations, et permet un camouflage de celle-ci. Le radôme peut aussi être de forme cylindrique, hémisphérique, ou toute autre forme adaptée qui ne dégrade pas les performances de la structure 10 antennaire. Pour des raisons de clarté, le radôme n'est pas représenté sur les vues en perspective des figures 1, 3, 5 et 8. Dans d'autres modes de réalisation, la structure 10 antennaire peut ne pas comprendre de radôme. Figures 2, 4 and 6 show schematically in section the first, the second and the third embodiment. In these three embodiments, the antenna structure comprises a parallelepipedal radome surrounding the radiating structure 12, made of a material of low permittivity, for example fiberglass, polyamide or ABS polymer. The radome is designed so that it does not disrupting the radiation performance of the antennal structure, protects it from possible damage, and allows a camouflage thereof. The radome may also be cylindrical, hemispherical, or any other suitable form that does not degrade the performance of the antenna structure. For the sake of clarity, the radome is not shown in the perspective views of FIGS. 1, 3, 5 and 8. In other embodiments, the antenna structure may not include a radome.
La figure 7 représente une vue schématique en perspective d'une structure 10 antennaire selon un quatrième mode de réalisation de l'invention. La structure 10 antennaire selon ce quatrième mode de réalisation se distingue du troisième mode de réalisation notamment par la surface 211 de connexion, qui est fixée à la première bande 21 métallique et qui est ici orientée dans une direction opposée au troisième mode de réalisation, c'est-à-dire dans une direction opposée à la deuxième bande 22 métallique. En outre, l'élément de court-circuit est composé de deux bandelettes 24a, 24b. Figure 7 shows a schematic perspective view of an antenna structure according to a fourth embodiment of the invention. The antenna structure according to this fourth embodiment differs from the third embodiment in particular by the connecting surface 211, which is fixed to the first metal strip 21 and which is here oriented in a direction opposite to the third embodiment, c that is to say in a direction opposite to the second metal strip 22. In addition, the short circuit element is composed of two strips 24a, 24b.
De plus, le deuxième pan de la structure 10 antennaire est légèrement modifié. La bande rayonnante 233b est composée d'une unique portion trapézoïdale et ne comprend pas de portion rectangulaire comme c'était le cas sur le troisième mode de réalisation. Ensuite, la bande rectangulaire 237b est de forme trapézoïdale, sa largeur augmentant depuis la bande rayonnante 235b vers la bande 236b.  In addition, the second pan of the antenna structure is slightly modified. The radiating strip 233b is composed of a single trapezoidal portion and does not include a rectangular portion as was the case in the third embodiment. Then, the rectangular strip 237b is trapezoidal in shape, its width increasing from the radiating strip 235b to the strip 236b.
Du fait de la forme de ce deuxième pan, le radôme 3 n'est pas parallélépipédique mais présente une forme proche des contours de la structure 10 antennaire, permettant ainsi de réduire son encombrement. De même, la forme du boîtier 6 métallique et du plan 1 de masse est ajusté à la forme du radôme 3.  Because of the shape of this second panel, the radome 3 is not parallelepipedic but has a shape close to the contours of the antenna structure, thus reducing its bulk. Similarly, the shape of the metal casing 6 and the ground plane 1 is adjusted to the shape of the radome 3.
Les modifications apportées par les modes de réalisation successivement décrits permettent chacune une amélioration des performances de la structure 10 antennaire, la performance étant croissante entre le premier, le deuxième, le troisième et le quatrième mode de réalisation. Notamment, la bande de fréquence possible d'utilisation de la structure 10 antennaire est la plus large pour le quatrième mode de réalisation et décroit pour les autres modes. Toutefois, le premier mode de réalisation est aussi le moins complexe à produire, et la complexité de fabrication augmente avec les modes de réalisation suivants, jusqu'au quatrième mode de réalisation qui est le plus complexe des modes de réalisation présentés, pour des performances supérieures. The modifications made by the successively described embodiments each allow an improvement in the performance of the antenna structure, the performance being increasing between the first, second, third and fourth embodiments. In particular, the possible frequency band of use of the antenna structure is the widest for the fourth mode of realization and decreases for the other modes. However, the first embodiment is also the least complex to produce, and the manufacturing complexity increases with the following embodiments, until the fourth embodiment which is the most complex of embodiments presented, for superior performance. .
Les bandes rayonnantes des modes de réalisation décrits précédemment sont composées de surfaces métalliques. Les figures 8 et 9 représentent schématiquement des structures antennaires selon respectivement un cinquième et un sixième mode de réalisation, dans lesquels des bandes rayonnantes et des bandes métalliques sont composées d'une pluralité de bandelettes rayonnantes. Ces bandelettes rayonnantes sont métalliques et sont réparties de façon à occuper la même longueur et la même largeur que les surfaces métalliques des modes de réalisation précédents. The radiating bands of the previously described embodiments are composed of metal surfaces. Figures 8 and 9 schematically show antennal structures respectively according to fifth and sixth embodiments, in which radiating strips and metal strips are composed of a plurality of radiating strips. These radiating strips are metallic and are distributed so as to occupy the same length and the same width as the metal surfaces of the preceding embodiments.
Le cinquième mode de réalisation, représenté figure 8, se base sur une structure 10 antennaire selon le premier mode de réalisation, dans laquelle les bandes métalliques et les bandes rayonnantes orientées verticalement sont composées d'une pluralité de bandelettes rayonnantes, ici trois bandelettes 28 rayonnantes par bande rayonnante et bande métallique. Les bandes rayonnantes orientées horizontalement prennent la forme d'une surface métallique, comme dans les modes de réalisation précédents.  The fifth embodiment, shown in FIG. 8, is based on an antenna structure according to the first embodiment, in which the metal strips and the vertically oriented radiating strips are composed of a plurality of radiating strips, here three radiating strips 28. by radiating band and metal band. Horizontally oriented radiating strips take the form of a metal surface, as in the previous embodiments.
Dans le sixième mode de réalisation, représenté figure 9, toutes les bandes rayonnantes et les bandes métalliques sont composées de bandelettes 28 rayonnantes. En outre, le plan 1 de masse est composé de fils 30 conducteurs disposés en étoile en partant de la structure 10 antennaire.  In the sixth embodiment, shown in FIG. 9, all the radiating strips and the metal strips are composed of radiating strips 28. In addition, the ground plane 1 is composed of conductor wires arranged in a star pattern starting from the antenna structure.
L'utilisation de bandelettes rayonnantes est particulièrement utile pour l'utilisation d'une structure 10 antennaire adapté pour des fréquences faibles, c'est-à- dire pour des longueurs d'ondes élevées, les dimensions de la structure 10 antennaire rendant complexe l'utilisation de surfaces métalliques de grandes dimensions, pour des raisons de difficulté de fabrication, de coût, de résistance de la structure 10 antennaire aux contraintes physiques, aux intempéries, etc. Les bandelettes rayonnantes ont une largeur pouvant varier entre quelques millièmes à quelques centièmes de la longueur d'onde maximale. De même, dans le cas où la structure 10 antennaire est de grandes dimensions, le plan de masse utilisé dépend de la nature du sol sur lequel est disposée la structure 10 antennaire, dit plan de sol. Lorsque le plan de sol est composé d'un milieu de faible conductivité électrique (sable, terre, roche, etc.), un plan de masse est ajouté, par exemple grâce aux fils conducteurs en étoile comme représenté sur la figure 9. Le nombre de fils conducteurs en étoile utilisés varie en fonction de la conductivité électrique du milieu et peut atteindre 120 fils pour un milieu de très faible conductivité électrique. Lorsque le plan de sol est composé d'un milieu fortement conducteur (mer, marais salant, etc.), le plan de sol forme le plan de masse de la structure 10 antennaire. La figure 10 représente un véhicule 32, ici une automobile, équipé d'une structure 10 antennaire selon un mode de réalisation de l'invention. Le plan 1 de masse de la structure 10 antennaire est relié électriquement à un toit 34 métallique du véhicule 32, permettant ainsi d'étendre la surface effective du plan 1 de masse. La figure 11 est une courbe représentant l'adaptation d'impédance d'une structure 10 antennaire selon le quatrième mode de réalisation de l'invention, en fonction de la fréquence, dans la bande de fréquence 470-700 MHz. L'adaptation d'impédance est représentée par le rapport d'onde stationnaire (ROS ou VSWR pour Voltage Standing Wave Ratio en anglais) de la structure 10 antennaire. Le rapport d'onde stationnaire d'une structure antennaire est parfait si celui-ci est égal à 1. La structure 10 antennaire selon l'invention vise à obtenir de préférence un rapport d'onde stationnaire compris entre 1 et 1,5. La courbe de la figure 11 montre que dans la bande de fréquence 470-700 MHz, le rapport d'onde stationnaire est inférieur à 1,5 et qu'il est égal à 1,5 aux bornes 470 MHz et 700 MHz. L'adaptation d'impédance est ainsi bonne pour toutes les fréquences de la bande de fréquence, permettant ainsi une utilisation de la structure antennaire pour l'émission et la réception. The use of radiating strips is particularly useful for the use of an antenna structure adapted for low frequencies, i.e. for high wavelengths, the dimensions of the antennal structure making it difficult to use the antenna. use of large metal surfaces, for reasons of difficulty of manufacture, cost, resistance of the antennal structure to physical constraints, weather, etc. The radiating strips have a width that can vary between a few thousandths and a few hundredths of the maximum wavelength. Similarly, in the case where the antennal structure is large dimensions, the ground plane used depends on the nature of the soil on which the antennal structure, said ground plane, is disposed. When the ground plane is composed of a medium of low electrical conductivity (sand, earth, rock, etc.), a ground plane is added, for example by means of the star conductors as shown in FIG. The star conductor wires used vary according to the electrical conductivity of the medium and can reach 120 wires for a medium of very low electrical conductivity. When the ground plane is composed of a highly conductive medium (sea, salt marsh, etc.), the ground plane forms the ground plane of the antenna structure. FIG. 10 shows a vehicle 32, here an automobile, equipped with an antenna structure according to one embodiment of the invention. The plane 1 of mass of the antenna structure 10 is electrically connected to a metal roof 34 of the vehicle 32, thereby extending the effective surface of the ground plane 1. Fig. 11 is a graph showing the impedance matching of an antenna structure according to the fourth embodiment of the invention, as a function of frequency, in the frequency band 470-700 MHz. Impedance matching is represented by the Standing Wave Ratio (VSWR) of the antenna structure. The stationary wave ratio of an antenna structure is perfect if it is equal to 1. The antenna structure according to the invention aims to obtain preferably a standing wave ratio of between 1 and 1.5. The curve of FIG. 11 shows that in the frequency band 470-700 MHz, the standing wave ratio is less than 1.5 and that it is 1.5 at the 470 MHz and 700 MHz terminals. The impedance matching is thus good for all the frequencies of the frequency band, thus allowing use of the antennal structure for transmission and reception.
La figure 12 est un diagramme de rayonnement azimutal en champ lointain d'une structure 10 antennaire selon un mode de réalisation de l'invention. Le diagramme de rayonnement est représenté pour une fréquence de 550 MHz, c'est-à- dire comprise dans la bande de fréquence de 470-700 MHz. Le rayonnement est représenté dans le plan azimutal, c'est-à-dire selon le plan défini par les axes X-X et Y-Y, dans une configuration où la structure 10 antennaire est placée sur un plan métallique circulaire de 1.5 m de diamètre et dans une position angulaire dont les valeurs angulaires sont comprises dans l'intervalle ]-180°, 180°]. Les angles 0° et 180° correspondent à des positions angulaires sur l'axe X-X, l'angle 0° étant situé du côté de la deuxième bande 22 métallique et l'angle 180° étant situé du côté de la première bande 21 métallique. Les angles 90° et - 90° correspondent à des positions angulaires sur l'axe Y-Y. Fig. 12 is a far-field azimuth radiation pattern of an antenna structure according to one embodiment of the invention. The radiation pattern is represented for a frequency of 550 MHz, that is to say included in the frequency band of 470-700 MHz. Radiation is represented in the azimuthal plane, that is to say along the plane defined by the axes XX and YY, in a configuration where the antenna structure is placed on a circular metal plane 1.5 m in diameter and in an angular position with the angular values are in the range -180 °, 180 °]. The 0 ° and 180 ° angles correspond to angular positions on the XX axis, the 0 ° angle being located on the side of the second metal strip 22 and the 180 ° angle being located on the side of the first metal strip 21. The 90 ° and - 90 ° angles correspond to angular positions on the YY axis.
Le rayonnement est représenté en dBi, ce qui correspond au gain en décibel de la structure 10 antennaire par rapport à une antenne isotrope. Sur la courbe, le rayonnement varie progressivement entre environ -2 dBi pour un angle de 0° à une valeur légèrement inférieure à 0 dBi pour un angle de 180°. La variation est identique sur l'intervalle ]-180°, 0°], avec un rayonnement proche de OdBi pour un angle proche de -180°. La différence de rayonnement de la structure 10 antennaire entre l'angle 0° et l'angle 180° est due à la variation de densité surfacique de courant sur le premier pan et le deuxième pan de la structure 10 antennaire, du fait de la présence de la borne positive de l'émetteur au niveau de la première bande 21 métallique.  The radiation is represented in dBi, which corresponds to the decibel gain of the antenna structure relative to an isotropic antenna. On the curve, the radiation varies gradually between about -2 dBi for an angle of 0 ° to a value slightly lower than 0 dBi for an angle of 180 °. The variation is identical over the interval] -180 °, 0 °], with a radiation close to OdBi for an angle close to -180 °. The radiation difference of the antennal structure between the 0 ° angle and the 180 ° angle is due to the change in surface density of the current on the first and second panes of the antennal structure, due to the presence the positive terminal of the transmitter at the first metal band 21.
Le rayonnement pour toutes les fréquences comprises entre 470 MHz et 700 MHz présentent des courbes de rayonnement, non représentées pour des raisons de clarté, similaires à la courbe de rayonnement pour une fréquence de 500 MHz, avec de légères variations, inférieures à 1 dB.  Radiation for all frequencies between 470 MHz and 700 MHz have radiation curves, not shown for reasons of clarity, similar to the radiation curve for a frequency of 500 MHz, with slight variations of less than 1 dB.
La figure 13 est une courbe représentant les gains azimutaux maximum en fonction de la fréquence, dans la bande de fréquence 470-700 MHz, d'une structure 10 antennaire selon un mode de réalisation de l'invention. La mesure est la même que la courbe de la figure 12, le rayonnement étant exprimé en dBi. Comme visible sur le diagramme de rayonnement de la figure 12, le gain maximum est généralement le gain mesuré sur l'axe X-X de la structure 10 antennaire, du côté de la première bande métallique, c'est-à-dire au niveau de la valeur angulaire 180° sur la figure 12. Comme visible sur la figure 13, le gain azimutal maximum est stable, compris entre -1 dBi et 0 dBi sur l'ensemble de la bande de fréquence 470-700 MHz. L'invention ne se limite pas aux seuls modes de réalisation décrits. En particulier, les modes de réalisations présentés décrivent une structure antennaire à polarisation verticale, mais une orientation différente de la structure antennaire peut permettre son utilisation pour l'émission et la réception dans une polarisation linéaire différente, par exemple oblique ou horizontale. De plus, bien que la structure antennaire ait été décrite pour une utilisation dans une bande de fréquence comprise entre 470 MHz et 700 MHz, une structure antennaire selon l'invention peut être utilisée dans d'autres bandes de fréquences, les dimensions de celle-ci étant alors adaptées en conséquence. L'utilisation de la structure antennaire aux dimensions adaptées à d'autres bandes de fréquence permet d'obtenir les mêmes avantages que les modes de réalisation décrits dans ces bandes de fréquences. Fig. 13 is a graph showing maximum azimuth gains versus frequency in the 470-700 MHz frequency band of an antenna structure according to one embodiment of the invention. The measurement is the same as the curve of FIG. 12, the radiation being expressed in dBi. As can be seen in the radiation diagram of FIG. 12, the maximum gain is generally the gain measured on the axis XX of the antenna structure, on the side of the first metal strip, that is to say at the level of the 180 ° angular value in Figure 12. As shown in Figure 13, the maximum azimuthal gain is stable, between -1 dBi and 0 dBi over the entire frequency band 470-700 MHz. The invention is not limited to the embodiments described. In particular, the embodiments presented describe an antenna structure with vertical polarization, but a different orientation of the antenna structure can allow its use for transmission and reception in a different linear polarization, for example oblique or horizontal. In addition, although the antenna structure has been described for use in a frequency band between 470 MHz and 700 MHz, an antenna structure according to the invention can be used in other frequency bands, the dimensions of which here being adapted accordingly. The use of the antenna structure with dimensions adapted to other frequency bands makes it possible to obtain the same advantages as the embodiments described in these frequency bands.

Claims

REVENDICATIONS
1. Structure antennaire à large bande de fréquence, à polarisation selon une direction privilégiée, dite direction verticale, adaptée pour une émission et/ou une réception de signaux de longueur d'onde comprise entre une longueur d'onde minimale et une longueur d'onde maximale, ladite structure antennaire comprenant : 1. Antenna structure with a wide frequency band, with a polarization in a preferred direction, called a vertical direction, adapted for transmitting and / or receiving signals of wavelength between a minimum wavelength and a wavelength. maximum wave, said antenna structure comprising:
un plan (1) de masse, s'étendant selon un plan perpendiculaire à ladite direction verticale, dit plan horizontal,  a plane (1) of mass, extending in a plane perpendicular to said vertical direction, said horizontal plane,
une structure (12) rayonnante,  a radiating structure (12),
caractérisée en ce que ladite structure (12) rayonnante comprend  characterized in that said radiating structure (12) comprises
une première bande (21) métallique et une deuxième bande (22) métallique, disposées verticalement, espacées l'une de l'autre sensiblement parallèles l'une à l'autre, la deuxième bande (22) métallique étant reliée au plan (1) de masse et sensiblement perpendiculaire au plan (1) de masse,  a first metal strip (21) and a second strip (22) arranged vertically, spaced from each other substantially parallel to each other, the second strip (22) being connected to the plane (1) ) of mass and substantially perpendicular to the plane (1) of mass,
une boucle (14) rayonnante, comprenant une pluralité de bandes rayonnantes, une première extrémité de la boucle (14) rayonnante étant reliée à la première bande (21) métallique et une deuxième extrémité de la boucle (14) rayonnante étant reliée à la deuxième bande (22) métallique,  a radiating loop (14) comprising a plurality of radiating strips, a first end of the radiating loop (14) being connected to the first metal strip (21) and a second end of the radiating loop (14) being connected to the second metal strip (22),
au moins un élément (24) de court-circuit, reliant électriquement la première bande (21) métallique et la deuxième bande (22) métallique dans leurs parties les plus éloignées du plan (1) de masse.  at least one short-circuit element (24), electrically connecting the first metal strip (21) and the second metal strip (22) in their parts furthest away from the ground plane (1).
2. Structure antennaire selon la revendication 1, caractérisée en ce que la boucle (14) rayonnante est une boucle rayonnante repliée, dans laquelle les bandes rayonnantes forment au moins un repli (16a, 16b, 16c) de section droite en forme de U formé de deux bandes rayonnantes s'étendant selon la direction verticale reliées à leurs extrémités les plus proches du plan de masse par une bande rayonnante, dite base du U, s'étendant selon une direction parallèle au plan horizontal. 2. Antenna structure according to claim 1, characterized in that the loop (14) radiating is a folded radiating loop, wherein the radiating strips form at least one fold (16a, 16b, 16c) U-shaped cross section formed two radiating bands extending in the vertical direction connected at their ends closest to the ground plane by a radiating band, said base of the U, extending in a direction parallel to the horizontal plane.
3. Structure antennaire selon la revendication 2, caractérisée en ce que la base du U d'au moins un repli en U est agencée entre la première bande métallique et la deuxième bande métallique, et en ce que l'élément de court-circuit est formé au moins en partie par ladite base du U. 3. Antenna structure according to claim 2, characterized in that the base of the U of at least one U-shaped fold is arranged between the first metal strip and the second metal strip, and in that the short-circuit element is formed at least in part by said base of the U.
4. Structure antennaire selon l'une des revendications 1 à 3, caractérisée en ce qu'elle présente un encombrement vertical, entre le plan (1) de masse et le point le plus haut de la structure (12) rayonnante, inférieur à un dixième de la longueur d'onde maximale. 4. Antenna structure according to one of claims 1 to 3, characterized in that it has a vertical space between the plane (1) of mass and the highest point of the structure (12) radiating, less than one tenth of the maximum wavelength.
5. Structure antennaire selon l'une des revendications 1 à 4, caractérisée en ce que la première bande (21) métallique est adaptée pour être reliée à une borne positive d'un émetteur/récepteur (4) et le plan (1) de masse est adapté pour être relié à une borne négative dudit émetteur/récepteur (4). Antenna structure according to one of claims 1 to 4, characterized in that the first metal strip (21) is adapted to be connected to a positive terminal of a transmitter / receiver (4) and the plane (1) of mass is adapted to be connected to a negative terminal of said transmitter / receiver (4).
6. Structure antennaire selon la revendication 5, caractérisée en ce que la longueur de la structure (12) rayonnante entre la borne positive de l'émetteur/récepteur (4) et la liaison du plan (1) de masse et de la deuxième bande (22) métallique est comprise entre la moitié de la longueur d'onde maximale et la longueur d'onde minimale. Antenna structure according to claim 5, characterized in that the length of the radiating structure (12) between the positive terminal of the transmitter / receiver (4) and the connection of the ground plane (1) and the second band (22) metal is between half the maximum wavelength and the minimum wavelength.
7. Structure antennaire selon l'une des revendications 5 ou 6, caractérisée en ce qu'elle comprend un boîtier (6) métallique disposé sur le plan (1) de masse et délimitant une cavité adaptée pour contenir l'émetteur/récepteur (4), ledit boîtier (6) métallique étant relié électriquement au plan (1) de masse et à la deuxième (22) bande métallique. 7. Antenna structure according to one of claims 5 or 6, characterized in that it comprises a housing (6) disposed on the metal plane (1) of mass and defining a cavity adapted to contain the transmitter / receiver (4). ), said housing (6) being electrically connected to the ground plane (1) and the second (22) metal strip.
8. Structure antennaire selon l'une des revendications 5 à 7, caractérisée en ce que la première bande (21) métallique est reliée à l'émetteur/récepteur (4) via une surface (211) de connexion métallique sensiblement parallèle au plan horizontal. 8. Antenna structure according to one of claims 5 to 7, characterized in that the first strip (21) is connected to the metal transmitter / receiver (4) via a surface (211) of metal connection substantially parallel to the horizontal plane .
9. Structure antennaire selon l'une des revendications 1 à 8, caractérisée en ce que la largeur de la structure (12) rayonnante est comprise entre un huitième de la longueur d'onde maximale et un tiers de la longueur d'onde minimale. 9. Antenna structure according to one of claims 1 to 8, characterized in that the width of the structure (12) radiating is between one-eighth of the length maximum wave and one-third of the minimum wavelength.
10. Structure antennaire selon l'une des revendications 1 à 9, caractérisée en ce que la largeur des bandes rayonnantes est variable le long de la boucle (14) rayonnante. 10. Antenna structure according to one of claims 1 to 9, characterized in that the width of the radiating bands is variable along the loop (14) radiating.
11. Structure antennaire selon l'une des revendications 1 à 10, caractérisée en ce que le plan (1) de masse a une largeur et une longueur supérieure à la longueur d'onde maximale. 11. Antenna structure according to one of claims 1 to 10, characterized in that the plane (1) of mass has a width and a length greater than the maximum wavelength.
12. Structure antennaire selon l'une des revendications 1 à 11, caractérisée en ce qu'elle comprend un radôme (3) entourant la structure (12) rayonnante. 12. Antenna structure according to one of claims 1 to 11, characterized in that it comprises a radome (3) surrounding the structure (12) radiating.
13. Véhicule, caractérisé en ce qu'il est équipé d'une structure (10) antennaire selon l'une des revendications 1 à 12, le plan (1) de masse de la structure (10) antennaire étant fixé à une surface (34) s'étendant dans un plan sensiblement parallèle au plan horizontal. Vehicle, characterized in that it is equipped with an antenna structure (10) according to one of claims 1 to 12, the plane (1) of mass of the antenna structure (10) being fixed to a surface ( 34) extending in a plane substantially parallel to the horizontal plane.
EP16709999.3A 2015-03-05 2016-02-22 Omnidirectional wideband antenna structure Active EP3266064B1 (en)

Applications Claiming Priority (2)

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FR1551878A FR3033449B1 (en) 2015-03-05 2015-03-05 BROADBAND OMNIDIRECTIONAL ANTENNA STRUCTURE
PCT/FR2016/050403 WO2016139403A1 (en) 2015-03-05 2016-02-22 Omnidirectional wideband antenna structure

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US20240006773A1 (en) * 2022-07-01 2024-01-04 Kabushiki Kaisha Tokai Rika Denki Seisakusho Metal plate antenna and antenna device

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JP2870940B2 (en) * 1990-03-01 1999-03-17 株式会社豊田中央研究所 In-vehicle antenna
US5926150A (en) * 1997-08-13 1999-07-20 Tactical Systems Research, Inc. Compact broadband antenna for field generation applications
US6486844B2 (en) * 2000-08-22 2002-11-26 Skycross, Inc. High gain, frequency tunable variable impedance transmission line loaded antenna having shaped top plates
JP2007180757A (en) * 2005-12-27 2007-07-12 Yokowo Co Ltd Antenna for a plurality of frequency bands
JP2007288649A (en) * 2006-04-19 2007-11-01 Yokowo Co Ltd Multiband antenna
JP5853883B2 (en) * 2012-06-28 2016-02-09 株式会社デンソー Antenna device
DE102012217113B4 (en) * 2012-09-24 2019-12-24 Continental Automotive Gmbh Antenna structure of a circularly polarized antenna for a vehicle

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