Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
  • H01Q9/04—Resonant antennas
  • H01Q9/44—Resonant antennas with a plurality of divergent straight elements, e.g. V-dipole, X-antenna; with a plurality of elements having mutually inclined substantially straight portions
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/24—Combinations of antenna units polarised in different directions for transmitting or receiving circularly and elliptically polarised waves or waves linearly polarised in any direction
  • H01Q21/26—Turnstile or like antennas comprising arrangements of three or more elongated elements disposed radially and symmetrically in a horizontal plane about a common centre

Definitions

• the present invention relates to multiband antennas with circular or linear polarization and having a frequency flexibility.
• the invention finds particular application in satellite positioning systems such as GPS and Galileo, as well as in satellite broadcasting systems for multimedia content.
• Multiband antennas are, for example, used in satellite positioning or broadcasting systems to reduce the number of antennas on board or positioned on the ground.
• Such antennas can combine several frequency bands in one and the same antenna. They also allow the combination of several applications.
• Multiband antennas comprising four inverted L-shaped radiating elements arranged on a low dielectric constant support. Such an antenna is for example described in the document WO
• the structure of the current antennas is limited by the shape of the radiating elements and their arrangement relative to each other which limits the reduction of the bulk, especially when one seeks to increase their flexibility in terms of operating frequencies .
• the invention proposes an antenna comprising a plurality of metallic elements, said metallic elements being in point contact with a ground plane and equidistributed around a central axis of symmetry of the antenna, perpendicular to the ground plane.
• each metal element extends from the point contact at a non-zero angle of inclination with respect to said ground plane and in that the ground plane comprises at least one recess. so that in operation, the adaptation of the antenna is better in a specified frequency band than when the ground plane is full.
• the antenna of the invention is advantageously integrated in satellite positioning systems and / or in satellite broadcasting systems for multimedia content.
• FIG. 1 illustrates the antenna of the invention wherein the metal elements are metal strands
• FIGS. 3a and 3b illustrate the side views of two possible non-rectilinear geometries for the metal elements of the antenna of the invention
• FIGS. 4a and 4b illustrate possible patterns for the metal elements of the antenna of the invention
• FIG. 5 illustrates the antenna of FIG. 2 with the plane of mass extended by a cylinder and filters and switches. arranged on metal elements
• FIGS. 6a and 6b respectively show the reflection coefficient (dB) as a function of the frequency (GHz) of the antenna of FIG. 5 simulated when the switches placed on each metal element are respectively open and closed
• FIGS. 7a, 7b and 7c illustrate the radiation pattern of the antenna of FIG. 5 simulated in the frequencies 1, 189 GHz, 1, 280 GHz and 1, 575 GHz respectively;
• FIGS. 8a, 8b and 8c respectively show a solid ground plane, a ground plane with four recesses of rectangular shape and a ground plane with four recesses circular shape;
• FIGS. 9a and 9b respectively show the reflection coefficient (dB) as a function of frequency for the antenna of FIG. 5, an antenna with a solid ground plane (FIG. 8a) and an antenna with a ground plane comprising four recesses of circular shape (Figure 8c).
• FIG. 1 illustrates an antenna comprising metal elements which, in operation, are able to radiate, thus forming radiating elements.
• the antenna structure generally comprises a plurality of metal elements, 10, 20, 30, 40.
• the antenna typically comprises four metal elements.
• the metal elements 10, 20, 30, 40 are distributed around a central axis of symmetry D of the antenna, perpendicular to the ground plane M (it is understood here that the axis of symmetry passes through the center O of the plane mass M).
• the metallic elements are in point contact 11, 21, 31, 41 with the ground plane M. They also extend from the ground plane M at a non-zero inclination angle ⁇ relative to the ground plane M.
• the angle of inclination ⁇ of the metal elements with the ground plane M is dependent on the application. It can therefore be right, acute (less than 90 °) or obtuse (greater than 90 °).
• the metal elements are equidistributed around a circle of center, the center O of the ground plane M.
• the antenna comprises four metal elements and 90 ° separate the portion 11, 21, 31, 41 of each metal element in point contact with the ground plane M.
• the metal elements, 10, 20, 30, 40 are identical and their angle of inclination ⁇ with respect to the ground plane M is equal to 45 °.
• the angle of inclination ⁇ initiated at each metal element is such that the metal elements are oriented in the same direction, they can be oriented towards the axis of symmetry D of the antenna or in one direction opposite.
• the metal elements are oriented towards the axis of symmetry D of the antenna perpendicular to the ground plane M.
• the metal elements 10, 20, 30, 40 are printed on a dielectric substrate, this substrate being further supported by a pyramidal structure S having no radiofrequency properties.
• the pyramidal structure may further comprise a number of sides greater than four.
• Such a structure ensures the mechanical strength of the antenna and can be made of polystyrene material.
• FIG. 2 illustrates an antenna comprising a pyramidal structure S on which are placed the printed metal elements on a dielectric substrate.
• the structure is of a shape adapted to the inclination of the metal elements 10, 20, 30, 40.
• the structure S has a pyramidal shape.
• a structure S of this form is preferably used for producing the antenna.
• the metal elements are arranged on each of the faces of the structure S.
• Metal elements can take different forms.
• Figures 3a, 3b respectively illustrate a metal element in the form of a circular arc strand and a metal element in the form of broken strand.
• Figures 4a and 4b illustrate fractal geometry patterns obtained after several iterations of a triangular shape.
• the shape, pattern, length, and inclination of the metal elements are parameters that affect the bandwidth and antenna radiation pattern.
• ground plane M has dimensions that will condition the performance of the antenna in terms of radiation.
• the ground plane M is typically circular.
• the thickness and the radius of the ground plane M are dimensioned so as to limit the reflections on its edges.
• the ground plane M may comprise a recess 50 formed at its center to improve the adaptation of the antenna, this is illustrated in Figure 1.
• the recess is circular, square or octagonal.
• FIG. 5 illustrates an antenna comprising a cylinder 60 or straight waveguide, extending the ground plane.
• the dimensions of the cylinder are adapted to the recess 50.
• Such a cylinder acts as a waveguide operating under its cutoff frequency which limits the rear radiation of the antenna.
• the ground plane M can be extended by a pyramid (pyramidal waveguide) or a cone (conical waveguide), this shape being truncated as necessary depending on the congestion constraints and the performance characteristics. back radiation.
• the extension of the ground plane M by a cone, a pyramid or a cylinder contributes to improving the performance of the antenna and also constitutes an additional means of adjustment of the antenna.
• the shape of the guide section (straight, pyramidal or conical) is identical to the recess in the ground plane M. Depending on the targeted application, it is possible not to use a shape extending the ground plane M to reduce the size of the antenna.
• the ground plane M may comprise several recesses. Such a configuration makes it possible to control the rear radiation while having a better adaptation than in the case where the ground plane M is full (in FIG. 8a is shown an antenna with a solid ground plane M).
• the ground plane M must include a number of recesses equal to the number of metal elements, that is to say four recesses.
• FIGS. 8b and 8c show a ground plane M comprising four recesses 80-83, 84-87.
• the recesses 80-83 are rectangular in shape. The rectangular shape is such that the point contact of each metal element with the ground plane M defines the middle of one of the sides of each upper part of the rectangular shape.
• the recesses 84-87 are circular in shape, each adjacent to a point contact.
• the tangent T at the upper part of the recess of circular shape passes through the corresponding point contact.
• the latter are equidistributed in the same way as the metallic elements (the radiating elements of the antenna).
• the rectangular shaped recesses are inscribed inside a square of center O, the center of the ground plane M, the distance from the center O to the point contacts defining the mediators of the square.
• the recesses of circular shape are themselves inscribed inside the circle squared mentioned above.
• the recesses may further be rectangular in shape, octagonal.
• the four recesses of the ground plane M may be extended by straight waveguides, pyramidal or conical, possibly truncated. These waveguides are arranged at the recesses and are such that the shape of their sections at the contact with the ground plane M is identical to the recesses formed therein.
• the antenna is powered by means of excitations 12, 22, 32, 42 located at the contact 11, 21, 31, 41 of each metal element 10, 20, 30, 40 with the ground plane M.
• transmission lines 13, 23, 33, 43 are used in the extension of each metal element.
• the excitation points are connected to the ends of these transmission lines below the ground plane M which will be pierced accordingly.
• the transmission lines are for example microstrip lines of characteristic impedance equal to 50 ⁇ formed in the same material as the substrate S on which the metal elements are printed.
• the antenna shown is circular or linear polarization.
• the linear polarization is obtained when two metallic elements are fed, in this case they are fed with voltages of identical amplitudes in phase opposition.
• the circular polarization is obtained when four metal elements are powered, in this case they are supplied with identical amplitude voltages in phase quadrature.
• the antenna further has a flexible character and / or multiband.
• F1, F2, F3, F4 typically consist of a circuit comprising an inductor L and a capacitor C connected in parallel. These filters are placed on each of the metal elements.
• the switches make it possible to adjust the length and / or the geometry of the metal elements. More specifically, in terms of performance, they make it possible to move the operating frequencies of the antenna to lower frequencies, especially when they are switched to the closed position. It should be noted that on each of the metal elements the filters and the switches are positioned identically on each of the metal elements in order to maintain the symmetry of the radiating structure.
• the prototypes made include four radiating elements.
• the prototype produced is in particular that illustrated in FIG.
• the antenna comprises four radiating metal strands of width equal to 1 mm printed on a dielectric substrate disposed on a support in polystyrene material pyramid-shaped.
• the dielectric substrate has a dielectric permittivity equal to 2.08 and a thickness typically equal to 0.762 mm.
• the metal elements are extended by microstrip lines of width equal to 2.39 mm on which we will connect the excitations associated with each metal element.
• the antenna allows according to the power supply to have a linear or circular polarization.
• Linear polarization is obtained by feeding two opposite metallic elements.
• the circular polarization is obtained by feeding the four metal elements.
• the frequency flexibility is obtained by means of switches arranged along the metal elements.
• the multiband appearance is achieved by means of band-cut filters arranged along the metal elements.
• the prototype made here is bi-band and targets the following three bands
• band 1 E5a / L5 and E5b
• band 2 E6
• band 3 L1 extended.
• the band 3 is always present and according to the open or closed position of the switches, we will be able to have the band 1 and the band 3 or the band 2 and the band 3.
• the frequencies of the bands targeted by the antenna are, by way of illustration and without limitation, those of the GPS system (in English, “Global Positioning System”) and the Galileo system.
• L1 band 1, 563-1, 587 GHZ (civilian applications)
• L2 band 1, 215-
• band L5 1, 164-1, 197 GHz (for modernization of the current GPS system).
• the frequencies of the Galileo system are as follows.
• Band E5a 1, 164-1, 197 GHz
• band E5b 1, 197-1, 214 GHz
• band E5 extended 1, 142-1, 252 GHz (for applications requiring high accuracy)
• band E6 1 , 260-1, 300 GHz
• extended band L1 see GPS system: 1, 559-1, 591 GHz.
• Figures 6a and 6b illustrate the reflection coefficient (dB) as a function of the operating frequency (GHz) when the switches are in the open position (see Figure 6a) and in the closed position (see Figure 6b).
• dB reflection coefficient
• the curve 60 is obtained by simulations performed on the prototype, the curve 61 is the desired target curve and the curve 62 corresponds to the nominal specifications of adaptation in the target bands.
• the antenna is bi-band by the use of filters.
• the band 3 extended L1
• the bands 1 and 2 are respectively reached according to the open or closed position of the switches. Still with reference to FIGS. 6a and 6b, it can be seen that the adaptation for each of the bands concerned meets the nominal specifications required.
• the selected bands allow the same antenna to be used for civil safety applications (aviation, etc.) or commercial satellite navigation services.
• the choice between flexibility and multiband is guided by the application and especially the proximity of the frequency bands to be covered.
• the nature of the filters employed imposes a minimum separation between two successive frequency bands.
• FIGS. 7a, 7b and 7c illustrate the radiation pattern of the antenna of FIG. 5 simulated in the frequencies 1, 189 GHz, 1, 280 GHz and 1, 575 GHz respectively.
• the antenna presented has a circular polarization, the radiating elements are powered in quadrature phase.
• the curve 70 is the left circular polarization radiation pattern
• the curve 71 is the right circular polarization radiation pattern
• the curve 72 is a template representing the minimum required values in main polarization.
• the radiation patterns obtained are of a quasi-hemispherical nature, allowing the reception of a maximum of satellite signals in visibility.
• This type of radiation pattern is characteristic of receiving antennas for satellite navigation applications.
• the cross polarization obtained in simulation is less than -10 dB in the half-space of interest, thus ensuring a purity of polarization necessary for the proper functioning of the antenna.
• FIGS. 9a and 9b illustrate the comparative performance of an antenna with a ground plane comprising a recess provided at its center extended by a cylinder, an antenna with a solid ground plane, an antenna with a ground plane comprising four recesses.
• Figure 9a shows the reflection coefficient (dB) as a function of the operating frequency (GHz).
• the curves 60, 90 and 91 illustrate the reflection coefficient for respectively the antenna with a ground plane comprising a recess provided in its center extended by a cylinder, for the antenna with a ground plane comprising four recesses. , for the antenna with a solid ground plane and the curve 62 represents the expected specifications.
• curve 91 is an intermediate solution between a solution with a solid ground plane, curve 90 and the best solution namely an antenna with a ground plane comprising a recess in its center.
• the different embodiments of the ground plane offer different resonant frequencies.
• the radiating elements have been optimized in adaptation for the ground plane comprising a recess formed in its center and extended by a cylinder, curve 60.
• the same radiating elements arranged on a solid ground plane have a frequency shift upwards about 14%, curve 90, which implies that the correction of this shift in Frequency requires an elongation of the radiating elements of the same order.
• the same radiating elements arranged on a ground plane comprising four recesses have an upward frequency shift of 8%, curve 91, which implies a radiating element elongation of less than half compared to the solution with a solid ground plane.
• Figure 9b illustrates the radiation pattern (dBi) as a function of theta angle (degrees).
• the curves 93, 94 and 71 represent the left circular polarization for respectively the antenna with a ground plane comprising a recess provided at its center extended by a cylinder, for the antenna with a ground plane comprising four recesses.
• the curves 97, 96 and 70 represent the crossed polarization for respectively the antenna with a ground plane comprising a recess provided at its center extended by a cylinder, for the antenna with a ground plane comprising four recesses.
• the curve 72 represents the expected specifications for the main polarization.
• antenna performance is equivalent.
• the performance of the antenna with a ground plane comprising a recess in the center extended by a cylinder is best in the half-space of interest (theta angle between -90 ° and + 90 °).
• this solution has a greater rear radiation (theta angle close to ⁇ 180 °) than solutions with a solid ground plane or four recesses.
• the performance of the antenna with a solid ground plane is similar to the performances with a ground plane comprising four recesses, both in the half-space of interest and in the backward radiation.
• the antenna with a ground plane comprising four recesses makes it possible to dispense with the use of a cylinder in order to improve the level of the rear radiation. This also allows a gain on the total height of the antenna while maintaining acceptable performance in terms of adaptation and cross polarization.
• the antenna thus described allows its structure to have many possibilities as to the different possible settings (inclination, geometry of the metal elements and the ground plane, filters and / or switches on the metal elements) of the antenna contributing to a multiplicity of targeted applications.
• the different degrees of freedom as to the inclination and the geometry of the metallic elements make it possible to optimize the bulk of such an antenna and to adapt the radiation pattern of the antenna to the intended applications.

Landscapes

• Variable-Direction Aerials And Aerial Arrays (AREA)
• Waveguide Aerials (AREA)
• Aerials With Secondary Devices (AREA)
• Details Of Aerials (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=38721745

Family Applications (1)

Country Status (5)

Families Citing this family (5)

Family Cites Families (9)

• 2007
  • 2007-04-13 FR FR0754447A patent/FR2915025B1/fr not_active Expired - Fee Related
• 2008
  • 2008-04-14 CA CA2683048A patent/CA2683048C/fr not_active Expired - Fee Related
  • 2008-04-14 WO PCT/EP2008/054507 patent/WO2008125662A1/fr active Application Filing
  • 2008-04-14 US US12/595,702 patent/US8289223B2/en not_active Expired - Fee Related
  • 2008-04-14 EP EP08736205.9A patent/EP2147479B1/de not_active Not-in-force

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events