Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/28—Combinations of substantially independent non-interacting antenna units or systems
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01Q—ANTENNAS, i.e. RADIO AERIALS
  • H01Q21/00—Antenna arrays or systems
  • H01Q21/29—Combinations of different interacting antenna units for giving a desired directional characteristic

Definitions

• the subject of the invention relates to an omnidirectional compact and very broadband antennal system having a separate access access and reception access and very strongly decoupled, that is to say, an antennal element having a function of emission and an antenna element having a reception function.
• the invention lies in the field of antennas or antenna systems dedicated to electromagnetic wave emission / reception applications in a very wide band, for example 30-3000 MHz.
• the concept implemented in the invention can be integrated on all types of carrier (ground, naval or airborne). It is particularly suitable for integration on the roof of a mobile carrier (civilian and military vehicles). It can be exploited in other frequency bands than the one mentioned above.
• Different antennal structures are known to the Applicant, such as monopole type antennas, saber antennas, dipole type antennas, biconical or discone antennas, or antennas loaded with a resistor or a resistor. box of agreement.
• the antenna structure according to the invention solves at least one or more of the aforementioned problems.
• a first conductive plate having a length L1 and a width 11, of surface S1,
• a second conductive plate having a length L2 and a width 12, of surface S2,
• Broadband excitation means having an outer surface and a surface profile adapted to generate or capture a biased electric field vertical line created between the two plates under the effect of a signal applied at a point of excitation of said first antennal element, said electric field propagating within a guide structure formed by the first plate, the second plate and the broadband excitation means, said excitation means has a pseudoconic form.
• At least one conductive link disposed between the first conductive plate and the second conductive plate, the one or more metal links being connected to said plates via at least one matching circuit,
• the second antennal element is, for example, nested in a conical portion itself integrated in the high pseudo-conical portion of said broadband excitation means.
• the second antennal element may consist of a first element adapted to operate at low frequencies, said first element being constituted by volumic turns of constant diameter and pitch per spiral side, a second element having a logarithmic square spiral profile. planar plane placed in continuity and in the same plane as said first element, a third element adapted for high frequencies and made by conformation on a pyramid with four sides of a logarithmic spiral with a square profile.
• the four-sided pyramid as well as the support of the elements can be made of relative permittivity foam close to 1.
• Said conductive plates are provided with orifices for fixing the metal links and adaptation circuits.
• Said matching circuits or antenna load circuits are constituted by one or more of the elements selected from the following list: resistance, capacitance and / or power choke.
• the matching circuit consists of one or more power resistors.
• the first antennal element has an optimized radiation towards the ground and the horizon.
• the second antennal element associated with the metallic plane covered with the ferrite tiles has an optimized radiation upwards and the horizon, ie. in a hemispherical way.
• the antennal system has a strong decoupling between the first antennal emission element and the antennal receiving element. It operates according to an electric field component in vertical polarization. The presence of the plane of ferrite tiles accentuates the decoupling between the antennal emission element and the antennal receiving element by trapping the currents at the level of the metal plane.
• the first antennal element supports strong powers.
• FIG. 1A a perspective view of the transmission-reception system according to a possible embodiment configuration
• FIG. 1C a detail of the constitution of the antenna 1 or first antennal element
• FIG. 1D an example of positioning of the antenna system according to the invention on a carrier
• FIG. 2 a detailed view of the reception (or interception) antenna
• FIG. 3A a view from above of the profile of the spiral arms that can be envisaged
• FIG. 4 the decoupling obtained in measurement between the transmission part and the interception part of the system for a given configuration
• FIG. 1A represents a perspective view of an exemplary embodiment of the antenna system according to the invention.
• the antenna 1 used in the present description for illustrative purposes is detailed in the applicant's patent application FR 08 07230.
• the antenna 1 consists, for example, of a lower plate 6 made of a conductive material such as a metal material having, for example, a length L1 of 2000mm and a width 11 of 1700 mm.
• This plate may be a planar or substantially planar metallic part independent or any of a carrier V ( Figure 1 D).
• a second conductive plate which in this example corresponds to the upper plate 5 and has a length L2 in this example of 2000 mm and a width 12 of 1700 mm ( Figure 1 B) forms the upper plane of the antennal system according to the invention.
• the plate 6 forming the lower plane and the plate 5 forming the upper plane may have an identical surface respectively S1, S2.
• the two plates can be made of the same metallic material adapted to microwave frequencies.
• the lower plate 6 and the upper plate 5 are spaced apart by a distance or gap E.
• the value of the spacing E between the two plates is chosen according to the minimum frequency of use.
• the spacing E may be less than the wavelength, corresponding to the minimum operating frequency, divided by 8.
• the larger the dimensions of the plates the smaller the spacing of the plates may be.
• the antennal system comprises a second antenna or antenna element 2 placed, for example, above the first antenna 1.
• a second antenna or antenna element 2 placed, for example, above the first antenna 1.
• the metal cavity may be of any shape, nevertheless the use of a conical or pseudoconic type of cavity makes it possible to improve the radiation performance of the antenna 2 for reception or interception on the horizon.
• the transmitting or scrambling antenna 1 is constituted by a broadband exciter 4 positioned between the metal planes 5 and 6 in which a matrix of holes Ti is formed in order to receive metal links 7 loaded by power resistors 8 or of adaptation circuits.
• the metal links 7 have the particular function of allowing electrical conduction between the various elements.
• the dielectric spacers 9 and 10 have the particular function of ensuring a mechanical rigidity of the system.
• the power resistors 8 may be arranged either in the upper part of the metal link 7 at the level of the upper plate 6, or as mentioned in FIGS. 1A, 1B in the lower part of the metal link 7 at the level of the lower plate. 6 of the antenna.
• the power resistance it is possible to use a charging circuit or adaptation circuit composed of one or more of the elements chosen from the following list: resistance, inductance, and / or capacity, the elements mentioned being used alone or in combination, knowing that the final function will be to ensure the adaptation of the antennal system.
• the resistance values chosen to illustrate the invention provide an adaptation of the antenna 1 to a characteristic impedance 50 ohms, and accept high power on the transmission path.
• the conductive metal bonds 7 may be made of any type of material having conductive properties adapted to microwave frequencies.
• the receiving antenna 2 is placed above a metal plane 12 covered almost completely by ferrite tiles 1 1 ( Figure 1 B).
• These tiles can have a shape, a thickness and characteristics of permittivity and variable permeability insofar as they retain absorption properties for the frequency bands 30 MHz -1000 MHz, in this example. They must remain attached to each other as much as possible. It is therefore appropriate to fix them, to stick them or to reduce their freedom of movement by an appropriate device. They make it possible to reduce to a few cm the thickness of the antenna 2 by absorption of the currents reflected on the metallic plane 12. They also make it possible to reduce the coupling between the transmitting antenna 1 and the receiving antenna 2 and of to make possible the radiation of the receiving antenna 2 in vertical polarization on the horizon, while not disturbing the radio performance of the transmitting antenna 1.
• the radiation of the transmitting antenna 1 is specifically oriented towards the horizon or towards the ground while the receiving antenna 2 equipped with these ferrite tiles proposes a radiation directed towards the horizon or toward the upper hemisphere. .
• This decorrelation of the radiation patterns greatly favors the decoupling between the two antennas.
• the direction of the radiation arrows is symbolized in FIG.
• the receiving antenna 2 (or interception) and the transmitting antenna 1 (or scrambling) according to the invention provide by construction an electromagnetic wave with a predominantly vertical polarization on the horizon.
• the broadband exciter has the particular function of establishing an electric field E guided between the two planes (5, 6) and its outer wall S 3 .
• the exciter may consist of several conductive facets (metal, for example) 2Oi whose profile of their outer wall has been optimized to operate on the bandwidth of the antenna.
• the assembly of the different facets 20i (for example, with symmetry of revolution), as well as their profile are chosen to ensure a progressive and omnidirectional transition of the electric field between an excitation point 21 disposed at the level of the lower plane 6 and the plane
• the excitation point 21 is, for example, a conductive cylinder formed for example in a machined metal material, providing the mechanical and electrical interface between the core of the connector 22 and the broadband exciter.
• the facets 20i may be metal plates, metal fabric or formed of metal rods.
• the facets 20i are, for example, connected to each other and to the upper plate 5 with metal screws (or conductive). Any other fastener allowing electrical continuity between the two parts may be considered. It is also possible to use a mechanically welded technique.
• the various metal parts are, for example, screwed or nested with each other so as to ensure good mechanical strength and electrical continuity from the core of the connector 22 to the exciter junction - upper plate. Any other technique allowing an assembly ensuring, on the one hand, a mechanical strength and on the other hand an electrical continuity can be used.
• the combination of elements 20 and 23 forms the broadband exciter.
• the assembly has an outer surface Se and a surface profile Ps adapted to generate a linear vertical polarization electric field created between the two plates 5, 6, under the effect of a signal applied at an excitation point 21 of the antenna, said electric field propagating within a guiding structure formed by the upper plate, the lower plate and the excitation means.
• the metal cone 23 makes it possible to ensure the mechanical and electrical interface between the facets 20i and the excitation point 21.
• the exciter can take different forms and consist of one or more parts as long as this gradual transition is ensured between the two planes or the two plates.
• the progressive transition is defined in the context of the invention as a transition or mechanical profile progressive symmetry of revolution between the excitation point 21 and the upper plate 5 for very broadband impedance matching.
• the broadband excitation means generates, for example, a vertically polarized electric field.
• the broadband excitation means is, for example, adapted to create an electric field propagating between the two plates said antenna generating an omnidirectional radio radiation in azimuth oriented towards the ground and the horizon.
• the use of facets to form the outer wall of the exciter offers advantages such as facilitating the assembly and manufacture of the system.
• the excitation of the facets 20i is provided by a conical metal cylinder 23 at the top of which is placed the excitation point 21 and at the base of which are fixed the metal facets 20i.
• This part 23 of the system is not necessarily conical, but may be cylindrical, hemispherical, exponential or logarithmic, according to shapes and profiles known to those skilled in the art.
• the dimensions above are given for illustrative purposes. Indeed, the dimensions of the upper plane may be greater, smaller or equal to the dimensions of the lower plane according to the desired orientation of the radiation, to the ground, the horizon or the sky.
• the shape of the plates can be rectangular, circular, square, ovoid or polygonal complex depending on the surface acceptable by the wearer and the specification relating to the omnidirectionality of the radiation patterns.
• Figure 2 shows a detailed view of the receiving antenna having in this example an interception role. It is constituted by the ferrite plane 1 1 placed on the metal plane 12 on the one hand, and by a logarithmic spiral discretized (ie whose logarithmic evolution is not done continuously but by piece) two-armed, B1, B2, square profile formed by the elements 13, 14 and 15, respectively adapted for low frequencies, medium frequencies and high frequencies.
• a logarithmic spiral discretized ie whose logarithmic evolution is not done continuously but by piece
• B1, B2 square profile formed by the elements 13, 14 and 15, respectively adapted for low frequencies, medium frequencies and high frequencies.
• Element 13 is constituted by volume turns of constant diameter and pitch per spiral side, that is, each spiral side will see a constant pitch that will be different from another spiral side.
• a logarithmic progression for example, makes it possible to change the pitch of the turns between two consecutive sides of the square spiral. These turns make it possible to inductively charge the profile of the spiral and thus reduce its surface bulk.
• the portion 14 is a planar logarithmic square spiral profile placed in continuity and in the same plane as the element 13.
• the portion 15 is made by conformation of a logarithmic spiral square profile on a pyramid with four faces. The conformation of 15 allows an improvement of the radiation performance at the high frequency horizon.
• the four-sided pyramid as the support 16 of the elements 13 and 14 is made, for example, of relative permittivity foam close to 1.
• Ferrite tiles contribute to the reduction of the height of the receiving antenna but also to the absorption of currents This last point also favors the optimization of the decoupling between the reception and the emission, corresponding in the context of the application to the interception and to the jamming.
• FIGS. 3A and 3B give a more detailed view of the elements 13, 14 and 15.
• the pitch used between each turn constituting the element 13 is chosen constant here by side of the antenna to facilitate the industrial realization of the element 13.
• the progression of this step can follow different quasi-logarithmic laws. However, care should be taken to use profiles with an important step on the first turns in order to minimize the phenomena of mismatch induced by overly pronounced reflection phenomena on these inductive elements.
• the excitation of the arms of the complete spiral forming the antenna 2 is in the center of 15 via a broadband impedance transformer with its outputs in phase opposition.
• the impedance ratio to be established is a function of the diameter of the wires constituting the arms of the spiral at level 15 and to a lesser extent of 13 and 14.
• Conductive elements 17 provide the electrical connections between elements 14 and 15.
• FIG. 4 shows the measured decoupling obtained between the transmitting antenna 1 and the receiving antenna 2 on the frequency band
• FIG. 5 represents the measured standing wave ratios obtained for the transmitting antenna 1 and the intercepting antenna 2 on the 30 MHz-3000 MHz frequency band for a configuration established according to the principle described above.
• this ratio remains lower than 6 over the whole band and less than 2: 1 from 100 MHz.
• the use of this antenna system in the presence of a small 4x4 type carrier vehicle reduces this ratio to 3: 1 over the entire band 30 MHz - 3000 MHz.
• the interceptor antenna the standing wave ratio is less than 4: 1 on 95% of the band, with an interceptor antenna 2 of 500 mm x 500 mm on a plane 11 of 700 mm x 700 mm .
• the antenna according to the invention notably has the following advantages:
• a significant decoupling between the transmitting antenna and the receiving antenna is obtained on the one hand, thanks to the decorrelation of the radiation patterns of each of the antennas and on the other hand, by the absorbing action of the currents by the ferrites placed between the modified spiral antenna and the transmitting antenna,
• the wide bandwidth adaptation of the receiving (or interception) antenna is obtained based on an antenna concept that is almost independent of the modified spiral type frequency.
• This modified spiral antenna is square. She has two arms inductively loaded on the last laps. This inductive load is carried out using volumic turns.
• the structure has a logarithmic progression both in the spiral pitch and the progression of its generator. To facilitate the realization of the antenna, the diameter and the pitch of each side of the spiral are for example constant.
• the optimization of the radiation on the horizon of the receiving antenna is obtained in particular thanks to the shape of the central part of the antenna, relative to the upper part of the bandwidth, which is shaped on a pyramid to four sides.
• the gain of the receiving antenna is directly related to the impedance matching of the antenna.
• the gain realized will be even better than the antenna will be well adapted.
• the receiving (or interception) antenna is particularly compact. Its interweaving at the heart of the transmitting (or jamming) antenna favors this aspect. On the other hand, the fact that the modified spiral is disposed on a ferrite plane or an equivalent goes in the same direction.
• the transmission and reception accesses are directly adapted to a characteristic impedance of 50 Ohms.

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• 2009
  • 2009-06-30 FR FR0903185A patent/FR2947391B1/fr active Active
• 2010
  • 2010-06-16 WO PCT/EP2010/058494 patent/WO2011000703A1/fr active Application Filing
  • 2010-06-16 EP EP10723616.8A patent/EP2449629B1/de active Active

Non-Patent Citations (1)

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