Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q13/00—Waveguide horns or mouths; Slot antennas; Leaky-waveguide antennas; Equivalent structures causing radiation along the transmission path of a guided wave
  • H01Q13/02—Waveguide horns
  • H01Q13/04—Biconical horns
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/06—Arrays of individually energised antenna units similarly polarised and spaced apart
  • H01Q21/20—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a curvilinear path
  • H01Q21/205—Arrays of individually energised antenna units similarly polarised and spaced apart the units being spaced along or adjacent to a curvilinear path providing an omnidirectional coverage

Definitions

• the present invention relates to the field of electromagnetic sensors or probes.
• the present invention now aims to provide a new electromagnetic probe having properties superior to those of known prior probes.
• the object of the present invention is in particular to propose a compact and broadband probe.
• the objective of the present invention is to cover at least close to two octaves, and to offer a high sensitivity, ie from 30 to 40 dB of dynamic range with a detection threshold of the order of 0.5 V / m .
• the above-mentioned assembly further comprises:
• a sleeve centered on the ground plane and placed opposite the reflective cone, - a rod-shaped element, which at least partially crosses the reflective cone and constitutes an adaptation stub, extending the central core of the coaxial attack.
• the present invention also relates to a probe comprising in combination several assemblies of the aforementioned type, arranged along multiple axes which are not parallel to each other to form a multidirectional probe, for example an electromagnetic tri-axis, isotropic, broadband and compact probe. allowing to simultaneously record 3 orthogonal components of the electromagnetic field, at the same point, without privileged polarization.
• FIG. 1 represents, in a sectional view through a meridian, the general structure of an elementary antenna according to the present invention
• FIG. 2 represents the Smith chart of the broadband isotropic elementary antenna illustrated in FIG. 1,
• FIG. 3 represents the ROS of this same antenna
• FIG. 4 represents the radiation diagram of the broadband isotropic elementary antenna illustrated in FIG. 1, measured at a frequency of 1 GHz
• - Figure 5 shows, in a sectional view through a meridian, the general structure of an antenna according to a variant of the present invention, comprising a dielectric medium chosen between the reflective cone and the ground plane
• - Figure 6 represents the Smith chart of the broadband isotropic elementary antenna illustrated in FIG. 5
• FIG. 8 represents, in a similar sectional view passing through a meridian, the general structure of another variant of antenna in accordance with the present invention.
• FIG. 9 shows a partial schematic perspective view of a tri-axis probe according to the present invention comprising three elementary antennas.
• FIG. 1 A broadband isotropic elementary antenna 10 in accordance with the present invention can be seen in the appended FIG. 1 which essentially comprises:
• the antenna 10 has a symmetry of revolution about an axis O-O.
• the reflective cone 100 has a circular base surface 102, transverse to the axis O-O.
• This base surface 102 is essentially flat and perpendicular to the axis O-O.
• the base surface 102 may have, projecting from its center, a barrel 104, cylindrical for example with base 106, planar.
• the base surface 102 corresponds to the face of the cone 100 furthest from the sleeve 200 and from the ground plane 250. It has for example a diameter D 102 of 97 mm.
• the reflective cone 100 has a through cylindrical channel 110, of constant section. The diameter of the latter can be of the order of 9 mm.
• the face 120 of the reflector 100, facing the sleeve 200 and the ground plane 250 is generally conical, tapered in the direction of the ground plane 250. More precisely according to the representation of FIG. 1, this face 120 is delimited by a curved generator , with continuous curvature, with concavity directed outwards. The deflection of this generator is typically of the order of 4 mm.
• the profile of this surface 120 is adapted (progressive deformation towards the free space) to define an impedance at least substantially constant.
• the axial height H 100 of the cone 100 (between its top and the base face 102) is typically of the order of 31 mm. According to the embodiment illustrated in Figure 1, the sleeve
• ground plane 250 are made in one piece. However, as a variant, they could be formed from two separate parts, not necessarily joined together.
• the reflector 100, the sleeve 200 and the ground plane 250 are formed of electrically conductive material, very advantageously of metal, for example aluminum.
• the ground plane 250 is essentially formed by a plate transverse to the axis O-O, at the center of which the sleeve 200 projects in the direction of the reflector 100. According to FIG. 1, the ground plane 250 has a base surface
• the wall 252 (the furthest from the reflector 100) circular, planar and perpendicular to the axis O-O, provided in its center with a cylindrical wall 254 of small thickness and height, which forms an outer sheath at the signal socket.
• the surface 252 typically has a diameter of 120 mm.
• the wall 254 has for example a radial thickness of the order of 2 mm and an axial height of the order of 6 mm.
• This low wall 254 surrounds an axial bore passing through stage 260.
• This bore 260 has two sections juxtaposed axially: a first section of small section 262 which opens on the face 252 and a second section 266 of larger section which opens on the face of the sleeve 200 directed towards the reflective cone 100.
• the section 262 has for example a diameter of the order of 8 mm and a length of the order of 11 mm. The diameter of this section 262 is typically identical to that of the bore 110 formed in the reflective cone 100.
• the section 266 has for example a diameter of the order of 21 mm and a length of the order of 17 mm.
• the two sections 262, 266 are connected by a recess 264, in the form of a flat crown, perpendicular to the axis O-O, directed towards the cone 100.
• the face 270 of the ground plane 250 directed towards the reflective cone 100 can be the subject of various variants.
• FIG. 1 it comprises three main sectors: a radially external sector 272, a median sector 274 and a radially internal sector 278.
• Sector 272 is delimited by a surface in a flat crown perpendicular to the axis O-O.
• the radial width of this sector 272 is typically of the order of 11 mm.
• the radially internal sector 278 is delimited by a surface in a planar ring perpendicular to the axis OO.
• the radial width of this sector 278 is typically of the order of 4.5 mm.
• the median sector 274 gradually converges towards the reflective cone 100, in the direction of the axis OO, that is to say from the external sector 272 towards the internal sector 278. It has a radial extension of the order of 27 mm.
• the median sector 274 can be delimited by a straight generator. However, according to the representation in FIG.
• this median sector 274 is delimited by 2 adjacent sections 275, 276, each rectilinear, which in combination form a dihedral with an angular opening of the order of 170 °, with concavity directed towards the 'outside.
• the sleeve 200 projects from the radially internal sector 278, in the direction of the reflective cone 100.
• the sleeve 200 makes it possible to decouple the point of attack of the antenna and the ground plane 250, which helps the adaptation of the system.
• the sleeve 200 can be the subject of various variants. According to Figure 1, it is formed of two cylinders juxtaposed axially: a first cylinder 210 followed by a second cylinder 220 of smaller section.
• the first cylinder 210 typically has an external diameter of around 32 mm and an axial length of around 6 mm.
• the second cylinder 220 typically has an external diameter of around 23 mm and an axial length of around 5 mm.
• the two cylinders 210, 220 have an identical internal diameter which corresponds to the second section 266 of the bore 260.
• the plane transverse to the axis O-O defined by the top of the cylinder 220 coincides with the plane defined by the top of the reflective cone 100.
• the axial distance H1 separating the faces 102 and 252 is typically 54 mm.
• the stub 300 is formed by an electrically conductive rectilinear bar, preferably made of metal, which extends the central core 402 from the coaxial attack. It is engaged in the bores 110 of the reflector 100 and 260 of the ground plane 250 and sleeve 200.
• This element 300 thus behaves like a serial stub which makes it possible to adjust the value of the input impedance and provides an additional parameter allowing the band widening.
• the length of the stub 300 is equal to the distance separating the two opposite external faces of the device defined by the barrel 104 and the sheath 254.
• the stub 300 is connected, at the level of this sheath 254, to the central core 402 of a coaxial supply line 401 whose external shielding 404 is connected to the sheath 254.
• the stub 300 typically has a diameter of the order of 4 mm. This diameter must be less than that of bore 110 so that the stub 300 is centered in the bores 110 and 262, without touching the cone 100 or the ground plane 250.
• the coaxial supply line 401 is only schematically represented in FIG. 1. It is moreover connected to any suitable connector and / or operating system shown diagrammatically under the reference 410.
• the dielectric medium 400 located between the reflective cone 100 and the ground plane 250 as well as the sleeve 200 can be the subject of numerous variants. It can be air. However, as will be seen later, it is preferably a dielectric material having a permittivity greater than 1.
• the antenna structure in accordance with the present invention, previously described, makes it possible to optimize the adaptation loop so as to maintain an R.O.S. less than 4 on almost 200% of the band. This is remarkable for a structure whose maximum size (120 mm of ground plane 250) remains of the order of a third of wavelength, at 0.9 GHz.
• the elementary antenna 10 being a structure of revolution around the axis OO
• the radiation diagram will be of revolution around this axis and all the sections passing through the axis OO will have the appearance presented in FIG. 4: a diagram typical dipole, with a zero field on the OO axis and a maximum of radiation at 90 ° from this axis, that is to say in the direction of the ground plane.
• FIG. 5 There is shown in Figure 5 attached, in a similar sectional view passing through a meridian, an alternative embodiment according to a preferred embodiment of the invention, generally similar to Figure 1, but comprising a dielectric medium 400 of selected permittivity, interposed between the reflective cone 100 and the ground plane 250, to further reduce the size of this radiating element.
• the dielectric material 400 has a dielectric permittivity close to 4.
• the reflective cone 100 illustrated in FIG. 5 is generally similar to that of FIG. 1. However, it will be noted that it does not include a barrel 104. Its external diameter D102 is of the order of 72 mm.
• the ground plane is shown in Figure 5 attached, in a similar sectional view passing through a meridian, an alternative embodiment according to a preferred embodiment of the invention, generally similar to Figure 1, but comprising a dielectric medium 400 of selected permittivity, interposed between the reflective cone 100 and the ground plane 250, to further reduce the size of this radiating element.
• the dielectric material 400 has a dielectric permittivity
• 250 is formed of a generally planar plate, having an external diameter D252 of the order of 80 mm and an axial thickness of the order of 2 mm.
• the low wall 254 projecting from the face of the ground plane 250 opposite the reflective cone 100, and designed to be connected to the external sheath 404 of the coaxial drive 401 typically has an external diameter of the about 6.5 mm, an inside diameter of about
• the ground plane 250 illustrated in FIG. 5 is provided on its face directed towards the reflective cone 100, and in its center, with a flat base cylinder, 278, typically having an outside diameter of the order of 30 mm, an internal diameter of the order of 9.5 mm and an axial height of the order of 2.5 mm.
• the shaped sleeve 200 consists of 3 cylinders 210, 220 and 230 projecting from the face of the ground plane 250, directed towards the reflective cone 100.
• the outside diameter of these cylinders 210 , 220 and 230 decreases from one cylinder to another, closer to the reflective cone 100.
• the first cylinder 210 has an outside diameter of around 19 mm and an axial height of around 2 , 5 mm,
• the second cylinder 220 has an outside diameter of around 14 mm and an axial height of around 2.5 mm,
• the third cylinder 230 has an outside diameter of around 11 mm and an axial height of around 2.5 mm, and
• the internal diameters of the three cylinders 210, 220 and 230 are identical and equal to the internal diameter of the cylinder 278 formed on the plate of the ground plane 250, that is to say of the order of 9.5 mm.
• the dielectric material 400 can fill the entire space defined between the reflective cone 100 and the ground plane 250 associated with the shaped sleeve 200.
• an "off-hook" or annular groove 410 is provided in the lower part of the dielectric material 400, adjacent to the ground plane 250. This arrangement makes it possible to avoid excessive mismatching. between the dielectric material and the free space.
• this annular groove 410 has a rectangular section whose bottom 412 is parallel to the axis O-O.
• the annular groove which is preferably simply filled with air, opens radially to the outside of the dielectric material 400.
• the internal diameter of the groove 410 is of the order of 36 mm and its axial height of the order 19.5 mm.
• the adaptation stub 300 can be formed of several sections having different diameters. According to the embodiment of FIG. 5, the adaptation stub 300 is formed of two sections 310, 320.
• the first section 310 is placed in the bore 110 of the reflective cone 100. It typically has an axial length of the order of 189 mm and an external diameter of the order of 3 mm. It will be noted that the end face of this first section 310 of the stub 300 is set back with respect to the external face 102 of the reflective cone 100.
• the second section 320 of the stub 300 has a smaller external diameter. It is located in the central part of the dielectric material 400 and crosses the ground plane 250 as well as the wall 254 associated with it.
• the second section 320 has an axial length of the order of 25 mm and an external diameter of the order of 1.5 mm.
• this dielectric sleeve or sheath 500 has an internal diameter of on the order of 1.5 mm, an external diameter on the order of 4 mm and an axial length on the order of 25 mm.
• FIG. 8 An alternative embodiment has been illustrated in FIG. 8 which differs essentially from the embodiment previously described and represented in FIG. 5 by the removal of the wall 254 replaced by a recess 255 in the hollow formed on the face 252 of the ground plane 250 farthest from the reflective cone 100.
• the dielectric material 400 has a permittivity of the order of 4, an external diameter of the order of 80 mm, and an axial height above the groove 410 of the order of 19.6 mm, the groove 410 having an axial height of the order of 19.6 mm and a radial depth of the order of 22 mm,
• the ground plane 250 and the sleeve 200 comprise 4 cylinders 278, 210,
• the present invention also provides a probe comprising several elementary antennas of the aforementioned type, arranged along multiple axes that are not parallel to each other.
• the ground planes 250 rest on the external faces of a polyhedron of chosen geometry.
• the probe thus proposed is an isotropic, broadband and compact tri-axis electromagnetic probe comprising three elementary antennas 10 of the type previously described with reference to FIGS. 1 to 8, arranged along three axes orthogonal two by two.
• the ground planes 250 of these three elementary antennas are supported on the adjacent faces of a cube corner 600, the axes OO of each elementary antenna being orthogonal to the face of considered support of the cube and the respective reflecting cones 100 arranged on the outside of the ground planes 250.
• Such a tri-axis probe makes it possible to simultaneously detect three orthogonal components of an electromagnetic field and therefore makes it possible to reconstruct the field originating from any polarization.
• the inventors have demonstrated that when combining several elementary antennas 10 as illustrated in FIG. 9, the coupling between the different elements does not degrade performance. Furthermore, the diffraction by the edges of the cube 600 does not destroy the isotropy of the radiation patterns.
• the present invention can find many applications.
• the present invention notably makes it possible to simultaneously measure the fields in the GSM, DCS and UMTS bands, ie from 0.9 GHz to 2.7 GHz.
• a conical surface 120 profiled and defined by a concave generator As a variant, the generator defining the profiled surface 120 could be convex, even rectilinear, depending on the environment and the agreement sought.
• the invention is not limited to the geometry of the dielectric insert 400 previously described and illustrated.
• the element 300 constituting the adaptation stub can be associated with any type of appropriate termination, for example short circuit, open circuit, thicker or thinner line sections, adjustable terminal capacities (varactor), iris (offset) or adjustable adjustment screw, etc.
• a probe structure with three elementary orthogonal antennas based on a cube corner can be generalized to any type of polyhedron for designing multiband, multipolarization probes, etc.
• all the dimensional values mentioned in the present description should only be considered as purely indicative of nonlimiting exemplary embodiments of the present invention

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• 2001
  • 2001-01-12 FR FR0100390A patent/FR2819640B1/fr not_active Expired - Lifetime
• 2002
  • 2002-01-10 WO PCT/FR2002/000072 patent/WO2002056418A1/fr active IP Right Grant
  • 2002-01-10 AT AT02711934T patent/ATE403952T1/de not_active IP Right Cessation
  • 2002-01-10 EP EP02711934A patent/EP1350285B1/de not_active Expired - Lifetime
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