Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P5/00—Coupling devices of the waveguide type
  • H01P5/12—Coupling devices having more than two ports
  • H01P5/16—Conjugate devices, i.e. devices having at least one port decoupled from one other port
  • H01P5/19—Conjugate devices, i.e. devices having at least one port decoupled from one other port of the junction type
  • H01P5/22—Hybrid ring junctions
  • H01P5/227—90° branch line couplers
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01P—WAVEGUIDES; RESONATORS, LINES, OR OTHER DEVICES OF THE WAVEGUIDE TYPE
  • H01P5/00—Coupling devices of the waveguide type
  • H01P5/12—Coupling devices having more than two ports
  • H01P5/16—Conjugate devices, i.e. devices having at least one port decoupled from one other port
  • H01P5/19—Conjugate devices, i.e. devices having at least one port decoupled from one other port of the junction type
  • H01P5/22—Hybrid ring junctions
  • H01P5/222—180° rat race hybrid rings
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q11/00—Electrically-long antennas having dimensions more than twice the shortest operating wavelength and consisting of conductive active radiating elements
  • H01Q11/02—Non-resonant antennas, e.g. travelling-wave antenna
  • H01Q11/08—Helical antennas

Definitions

• the field of the invention is that of wide bandwidth antennas with a hemispherical or quasi-hemispherical radiation pattern. More specifically, the invention relates to resonant helical antennas, and in particular the supply of such antennas.
• the antenna of the invention finds applications in particular in the context of mobile satellite communications between fixed users and mobiles of any type, for example aeronautical, maritime or land.
• satellite communication systems are implemented, or are currently under development (for example the INMARSAT, INMARSAT-M, GLOBALSTAR systems, etc.).
• PCS personal communication systems
• the very different incidences of the signals received or transmitted require the antennas to have a radiation diagram with hemispherical coverage.
• the polarization must be circular with an ellipticity ratio better than 5 dB in the useful band.
• the invention can find applications in all systems requiring the use of a wide band, a hemispherical coverage diagram, circular polarization and a good ellipticity ratio.
• the antennas must indeed have the above characteristics either in a very wide bandwidth, of the order of 10%, or in two neighboring sub-bands corresponding respectively to reception and to l 'program.
• This antenna called the resonant quadrifilar helix antenna (HQR)
• HQR resonant quadrifilar helix antenna
• a quadrifilar antenna is formed by four radiating strands.
• An exemplary embodiment is described in detail in the document "Analysis of quadrifilar resonant helical antenna for mobile communications", by A. Sharaiha and C. Terret (IEEE -
• the radiating strands are printed on a thin dielectric substrate, then wound on a cylindrical support transparent from the radioelectric point of view.
• the four strands of the propeller are open or short-circuited at one end and electrically connected at the other end with conductive segments arranged on the base of the lower part of the support cylinder.
• the four strands of the propeller are therefore excited through these conductive segments.
• This antenna conventionally requires a supply circuit, which ensures the excitation of the different antenna strands by signals of the same amplitude in phase quadrature. Several techniques are known for making such supply circuits.
• This technique has the advantage of being relatively simple to carry out and to implement. On the other hand, it leads to a not insignificant size, compared to the size of the antenna (which can for example have a size of the order of ten centimeters). This drawback makes this solution incompatible with many applications, especially when maximum miniaturization is required.
• each two-wire propeller can be powered by a coaxial balun of the so-called "balun” type folded ".
• the two two-wire are then excited in phase quadrature using a hybrid coupler.
• balun / adapter assembly used for this type of antenna (made for example from a coaxial section, the core and the sheath of which form a dipole) is complex and bulky.
• this type of arrangement has the drawback of forming a sort of bandpass filter with a band which is still too narrow.
• This technique eliminates hybrid couplers. On the other hand, it has the drawback of requiring a delicate adjustment of the length of the strands. In addition, the antenna is no longer symmetrical, and production will be more complex. Furthermore, this method remains specifically reserved for systems using a narrow operating band.
• the invention particularly aims to overcome these various drawbacks of the state of the art.
• an objective of the invention is to provide an antenna and its feed system (hereinafter, the term "antenna” includes the actual antenna and its feed system) which has a very wide band of operating frequency, for example greater than 10%.
• Another object of the invention is to provide such an antenna, which is of low cost, and easily industrially achievable.
• the invention aims to provide such an antenna, which can be manufactured in a very small number of successive operations.
• the invention also aims to provide such an antenna, which ensures an equiamplitude excitation of the four strands and a law in exact phase quadrature, and therefore a good quality of circular polarization.
• a resonant helical antenna comprising at least one helix formed by at least two radiating strands printed on a substrate.
• a broadband miniaturized supply structure for said radiating strands printed on said substrate comprising at least one hybrid coupler produced from semi-localized elements, so as to reduce the dimensions thereof.
• the realization of the antenna strands and the supply of printed elements makes it possible to produce the antenna and its supply in a single operation, without specific connection means, and in a particularly reduced format.
• hybrid couplers produced from semi-localized elements makes it possible to obtain the very broad band and the set of desired qualities, and in particular a small footprint, compared to systems based on the use of conventional lines.
• the invention can be applied to all types of helical antenna.
• said propeller is a quadrifilar propeller, formed by four radiating strands supplied by a supply structure comprising three hybrid couplers.
• said supply structure comprises a first hybrid 180 ° coupler associating an input and / or output supply of said antenna with two outputs and / or intermediate inputs phase shifted by 180 °, and two 90 ° hybrid couplers each associating one of said intermediate outputs and / or inputs of said first hybrid coupler at one of the ends of two of said radiating strands.
• said antenna is mounted on a support having first and second distinct parts having different permittivities, said first part carrying said radiating strands and said second part carrying said supply structure.
• said first part carrying the antenna strands has a permittivity greater than 1.
• An antenna as described above can be used alone, or in an antenna array.
• the invention also relates to the manufacture of such antennas, which proves to be particularly simplified, compared to known techniques.
• a resonant helical antenna the following stages are provided: printing on a flat substrate of at least two radiating strands, intended to form a helix, and of an independent broadband miniaturized power supply structure said radiating strands comprising at least one hybrid coupler produced from semi-localized elements, so as to reduce the dimensions thereof; winding said substrate around a cylindrical support.
• FIG. 1 illustrates an example of a quadrifilar helix antenna with integrated feed according to the invention, developed flat;
• FIG. 1 illustrates an example of a quadrifilar helix antenna with integrated feed according to the invention, developed flat;
• FIG. 2 shows the antenna of FIG. 1, wound cylindrical, so as to form an operational helix
• - Figure 3 shows in more detail the feed structure of the antenna of Figures 1 and 2
• Figure 4 illustrates the standing wave ratio (ROS) of a particular embodiment of the antenna of Figures 1 and 2
• Figures 5 and 6 show radiation diagrams measured in right and left circular polarization of the same embodiment, respectively at frequencies 1.98 GHz and 2.2 GHz
• FIG. 7 shows the gain measured in the direction of the maximum radiation of this same antenna, as a function of the frequency
• FIGS. 8 A to 8C illustrate the design of a -3 dB 90 ° coupler according to the invention:
• FIG. 8A conventional coupler made of distributed elements;
• FIG. 8B corresponding representation using cells in ⁇ ;
• FIG. 8A conventional coupler made of distributed elements
• FIG. 8B corresponding representation using cells in ⁇
• FIG. 8A conventional coupler made of distributed elements
• FIG. 8B corresponding representation using cells in ⁇
• FIG. 8C corresponding microstrip line coupler
• Figures 9 A and 9B illustrate the design of a -3 dB 180 ° coupler: - Figure 9 A: representation of a 180 ° hybrid ring;
• FIG. 9B corresponding microstrip line coupler.
• the invention therefore relates to an antenna with an integrated broadband feed system, produced according to a simple manufacturing technique and having a low cost price. As indicated above, the invention can be applied to any type of helical antenna.
• the preferred embodiment described above relates to a quadrifilar antenna.
• the four strands of the antenna and a feed structure are printed on the same substrate.
• Figure 1 illustrates the printed elements when the antenna is developed flat. It firstly comprises four radiating antenna strands 11] to 11 4 .
• the antenna dimensions vary depending on the frequency band and the coverage required.
• the dimensions of these strands can be as follows:
• They are for example made of copper, on a thin dielectric substrate, such as kapton ( ⁇ r ⁇ 3.8).
• the four strands 11] to II 4 are preferably open at their upper end 15 1 to 15 4 . They can also be short-circuited. However, the system of the invention is particularly suitable for the excitation of antennas with more open strands which, for equal performance, have smaller dimensions than the antennas with short-circuited strands.
• the other end 16 1 to 4 strands I6 is connected to the lines of attack of the supply circuit.
• the feed system is produced on the same substrate, in line with the antenna. It is made up of three hybrid couplers 12, 13 and 14 designed as semi-localized elements.
• the first hybrid coupler 12 is connected on the one hand to the antenna signal input (respectively output) 17, and on the other hand to the two inputs (respectively outputs) 18 and 19 of the other two couplers 13 and 14. It is a 180 ° hybrid coupler.
• the hybrid couplers 13 and 14 are two identical 90 ° couplers. They are connected on the one hand to the input 18 (respectively 19) and on the other hand to the end of the strands 16] and I6 2 (respectively I6 3 and I6 4 ). Thus, the four strands are fed in perfect phase quadrature, on a very broadband.
• the assembly thus obtained is then wound on a cylindrical support, to obtain the operational antenna, shown in front view in FIG. 2.
• the cylindrical support is a transparent support from the radioelectric point of view, that is to say having a permittivite close to 1.
• FIG. 3 illustrates more precisely the structure for supplying semi-localized elements according to the invention, magnified substantially by a factor of 3 compared to reality. It comprises two types of printed lines: narrow lines, having an inductive characteristic; wider lines, having a capacitive characteristic.
• the 90 ° couplers 13 and 14 each consist of 4 wide elements 31 d and 31 4 , connected 2 to 2 by 4 lines of small width 32 1 to 32 4 .
• the 190 ° coupler comprises 6 wide elements 331 to 336 connected by 6 narrow lines 34j to 34 ⁇ .
• Figures 8 A and 8C illustrate the design of a -3 dB 90 ° coupler. More information can be found, if necessary, in the thesis of M. Coupez, University of Western Brittany, "Study of phase-shifter structures potentially integrable at 900 MHz", May 1988.
• FIG. 8 A presents a classic diagram of a -3 dB 90 ° coupler in distributed elements. It comprises two line sections 81, 82 of length ⁇ g / 4 and of characteristic impedance Zc, and two line sections 83, 84 of length ⁇ g / 4, and of impedance Zc ⁇ / 2. Each of these line sections can be replaced by ⁇ cells of localized elements, formed of capacitances C and inductances L and L ', as illustrated in FIG. 8B.
• Such an antenna has in particular the following advantages: - the antenna is with open strands, therefore the impedance of each strand is easily adaptable to 50 ⁇ for an antenna having the desired properties (hemispherical coverage and weak reverse polarization); the feed structure using hybrids is broadband, and perfectly balanced: - in amplitude (identical for each strand); and in phase (0 °; ⁇ 90 °; ⁇ 180 °; ⁇ 270 °); the dimensions of the supply device are smaller than those of known systems (a gain of the order of 50% can be obtained). Indeed, we can easily see that each semi-localized element is very much smaller than the line it replaces (which is generally of a size multiple of ⁇ / 4); the antenna has strong strand-by-strand insulation. As an indication, we now present the measurement results obtained from a particular embodiment, intended for communications with equipment and proximity communications.
• the dimensions of the assembly formed by the antenna and the integrated power supply are as follows:
• FIGS. 5 and 6 relate to the radiation diagrams measured in right circular polarization (a) and in left circular polarization (b), respectively at the frequencies 1.98 GHz (FIG. 5) and 2.2 GHz (FIG. 6).
• a right circular polarization
• b left circular polarization
• FIGS. 5 and 6 relate to the radiation diagrams measured in right circular polarization (a) and in left circular polarization (b), respectively at the frequencies 1.98 GHz (FIG. 5) and 2.2 GHz (FIG. 6).
• Figure 7 shows the gain measured in the direction of maximum radiation as a function of frequency.
• the antenna can be used in a very wide band (more than 12%) with good performance (gain, rejection of reverse polarization, omnidirectionality, ).
• An antenna according to the invention can be produced in several ways. Thus, according to a first embodiment, it can be printed flat, as illustrated in Figure 1. It is then wound on a support to form the antenna ( Figure 2).
• the substrate intended to receive the printed elements can be produced directly in its final cylindrical shape.
• the printing of the strands and of the supply structure is carried out directly on the cylinder.
• the antenna of the invention advantageously lends itself to the production of antenna arrays.

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• 1996
  • 1996-03-19 FR FR9603698A patent/FR2746547B1/fr not_active Expired - Fee Related
• 1997
  • 1997-03-13 CN CN97194576.4A patent/CN1218582A/zh active Pending
  • 1997-03-13 WO PCT/FR1997/000455 patent/WO1997035356A1/fr active IP Right Grant
  • 1997-03-13 DE DE69707845T patent/DE69707845T2/de not_active Expired - Fee Related
  • 1997-03-13 ES ES97914394T patent/ES2165036T3/es not_active Expired - Lifetime
  • 1997-03-13 EP EP97914394A patent/EP0888647B1/de not_active Expired - Lifetime
  • 1997-03-13 US US09/142,985 patent/US6181295B1/en not_active Expired - Fee Related
  • 1997-03-13 CA CA002248853A patent/CA2248853A1/en not_active Abandoned
  • 1997-03-13 AU AU21650/97A patent/AU2165097A/en not_active Abandoned

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