EP0131512B1 - Dual reflector antenna with quasitoroidal coverage - Google Patents

Dual reflector antenna with quasitoroidal coverage Download PDF

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Publication number
EP0131512B1
EP0131512B1 EP84401409A EP84401409A EP0131512B1 EP 0131512 B1 EP0131512 B1 EP 0131512B1 EP 84401409 A EP84401409 A EP 84401409A EP 84401409 A EP84401409 A EP 84401409A EP 0131512 B1 EP0131512 B1 EP 0131512B1
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EP
European Patent Office
Prior art keywords
network
reflector
antenna
antenna according
axis
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EP84401409A
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German (de)
French (fr)
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EP0131512A1 (en
Inventor
Serge Drabowitch
Claude Aubry
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Thales SA
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Thomson CSF SA
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
    • H01Q3/24—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
    • H01Q3/245—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching in the focal plane of a focussing device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q19/00—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic
    • H01Q19/10—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces
    • H01Q19/102—Combinations of primary active antenna elements and units with secondary devices, e.g. with quasi-optical devices, for giving the antenna a desired directional characteristic using reflecting surfaces wherein the surfaces are of convex toroïdal shape

Definitions

  • the present invention relates to an antenna with quasi toroidal coverage with two reflectors, for the emission and / or reception of a microwave wave.
  • Various embodiments of static antennas are known, including a structure consisting of a set of antenna shaped slabs, arranged in a trunk of a pyramid; the coverage obtained is semi-spherical and the operation is satisfactory; its disadvantage, however, is that it has a high cost price.
  • An antenna known as a dome antenna is also known, which is constituted by a network of radiating elements allowing a scanning of the beam according to a cone of limited angle, of the order of 90 °, covered by a hemispherical dome, which comprises elements phase shifting the radiation passing through it, so that the scanning angle of the beam outside the dome is equal to 180 °.
  • This structure has the particular advantage of reducing the number of active elements necessary compared to the previous solution, but it has a number of drawbacks among which the complexity of manufacturing the dome which must include phase shifters, the volume of the resulting antenna and the losses occurring by reflection on the wall of the dome.
  • a microwave antenna comprising a source in the shape of a horn and two reflectors; the reflector placed in front of the horn is formed by two arcs of ellipse and has a vertex in the axis of the antenna; these various elements are arranged so that the phase center of the horn is one of the focal points of the ellipse and that the other focal point of the ellipse is that of the second reflector, formed by a parabolic arc.
  • a multibeam antenna comprising a plurality of horns illuminating a single reflector.
  • the present invention relates to a static antenna making it possible to avoid these drawbacks by using a double reflection system, the reflectors being passive and of revolution, which is relatively simple and therefore inexpensive to manufacture.
  • the subject of the invention is an antenna as defined by claim 1.
  • This antenna comprises means 1 for emitting a microwave radiation, constituted for example by a network of radiating elements substantially planar and parallel to a plane XOY, for example horizontal, of revolution around an axis OZ normal to XOY. It receives the energy to be transmitted from means 5, for example placed under the network 1, on a plane 6 supporting the antenna, for example also substantially parallel to XOY, and transmitting to the network 1 the microwave energy and the commands required by means 51.
  • the network 1 can be constituted for example by a plurality of sources, supplied by a matrix of circuits for forming one or more beams, represented in FIG. 1 as part of the means 5.
  • the network 1 can also use phase shifters as illustrated below, these various devices constituting means for controlling the law of illumination of the network in phase and possibly in amplitude.
  • the energy radiated by the network 1 is reflected by a reflector 2, of revolution around the axis OZ, in the form of a substantially elliptical or parabolic cap for example, the concavity of which is turned towards the network 1.
  • the rays reflected by the reflector 2 are reflected a second time by a reflector 3 which is itself in the form of a ring surrounding the network 1, this ring having a meridian whose concavity is turned towards the reflector 2; the reflector 3 is also of revolution around the axis OZ; it preferably extends to plane 6 supporting the antenna.
  • the antenna also includes a radome 4, the presence of which is not essential for its operation but which allows, in addition to the conventional functions of a radome, to support the reflector 2.
  • This radome 4 is substantially of revolution around the OZ axis like reflector 2; it can be cylindrical or conical; it is preferably based on the one hand on the circumference 20 of the reflector 2 and on the other hand on the outer circumference 30 of the reflector 3.
  • FIG. 2 represents an embodiment of the network 1 of FIG. 1.
  • a plate 12 in the form of a disc with an OZ axis, comprising radiating elements 11 and 14 respectively on its two faces, for example of the dipole type.
  • Each of the elements 11 is connected to an element 14 by means of a phase shifting circuit 13.
  • the network 1 thus formed is illuminated by a source or a system of primary microwave sources 10 of axis OZ.
  • the radiation emitted by the system 10 is picked up by the elements 11; after the phase shift induced by the circuits 13, the radiation is re-emitted by the radiating elements 14.
  • the angles of emission of energy by all of the radiating elements 14 are determined by the value of the phase shifts conferred by each of the circuits 13 and by the characteristics of the system 10.
  • FIG. 3a represents a partial view of an alternative embodiment of the array (1) used in the antenna according to the invention, in which the radiating elements 14 of FIG. 2 are of the unipole type.
  • FIG. 3a a fraction of the plate 12 is seen in section in which are inserted radiating elements of the unipole type, marked 15, which are solids of revolution for example as shown in the figure of conical shape, this which allows for greater bandwidth.
  • grooves 16 circularly around each unipole 15, these grooves constituting traps for the microwave wave; the depth of the grooves 16 is of the order of a quarter of the wavelength ( ⁇ ) emitted. As shown in the figures, the grooves 16 may be tangent circles.
  • the unipoles 15 are arranged in staggered rows.
  • the height of the unipoles is of the order of ⁇ / 4
  • the angle at the top of the cone formed by a unipole can be of the order of 20 ° and the diameter of the circles formed by the grooves, of the order of A / 2.
  • FIG. 3b the meridian section of the coverage diagram (envelope of the possible radiation diagrams) obtained with a network 1 made up of unipoles as shown in FIG. 3a is shown in polar coordinates.
  • the coverage of such a network is of quasi toroidal shape, that is to say of which the director is a closed non-circular curve, with a zero along the axis OZ and a zero in the plane XOY.
  • the maximum opening angle is for example between 45 ° and 60 °.
  • the geometry adopted for the reflectors 2 and 3 is a function, from the characteristics of the network 1, of the law of coverage in site desired for the whole of the antenna, for example a cosecanted law. Such a law is shown by way of example in FIG. 4.
  • a curve 7 represents the law of coverage of the antenna, which is almost toroidal and limited. substantially, on the one hand, by a plane parallel to XOY and, on the other hand, by a cone of axis OZ and of angle at the vertex y. It appears that the coverage of the antenna according to the invention is not hemispherical; however, this drawback is considered to be negligible, since the only targets which cannot be reached by such an antenna are those which are close to OZ, that is to say generally close to the zenith, i.e. - again say close targets.
  • the first method consists in considering the diagram of each source in the presence of reflectors, writing the expressions connecting the energy densities at the level of the network 1, the first then the second reflectors, then integrating the expressions obtained.
  • Another method consists in decomposing the network illuminations and consequently the resulting diagrams, in the absence and in the presence of reflectors, on the basis of orthogonal functions with circular symmetry. The calculation shows that there are a multiplicity of possible solutions for the equations of the meridians of the reflectors 2 and 3, the desired coverage diagram of the antenna being previously fixed; a particular radiation pattern is then obtained by the choice of the weighting law of the network in phase and possibly in amplitude; this is of course an advantage.
  • the final choice of the couple of meridians is preferably done using the technique known as conformation known in Cassegrain type systems and which consists, after having calculated the two reflectors, to modify by successive approximations the meridian of one of them to get closer to the desired radiation pattern, then modify the second reflector accordingly.
  • the element 4 can be a continuous radome or a simple support, continuous or not, metallic or dielectric of the reflector 2. It can also carry a polarization filter, formed of conductive wires parallel to the polarization direction to be eliminated. It can also carry a polarizer making it possible to radiate for example a wave with circular polarization: in this case, it carries conductive wires oriented at 45 ° with respect to the incident polarization.
  • An antenna has been described above using passive focusing devices, which make it possible to modulate the gain of the array and thereby limit the number of active elements necessary, for a given gain, compared to direct radiation antennas.
  • this antenna uses the reflection phenomenon, thus avoiding losses at the interfaces encountered in transmission systems.
  • it uses two reflectors, which on the one hand gives greater flexibility in the choice and focusing of the reflectors and on the other hand limits the size of the antenna.
  • the reflectors are passive and of revolution, which is relatively simple and inexpensive to manufacture.
  • this antenna is adapted to the radiation of any polarization: constant polarization throughout the diagram and parallel to OZ if the network consists of unipoles, in the XOY plane if the network consists of current loops parallel to XOY, and circular if the network consists for example of propellers or any other source of circular polarization.
  • the antenna described above is therefore capable of transmitting and receiving a directive beam electronically scanning the antenna coverage area. It is also likely to operate in multibeam mode.
  • the means 1 can be any and for example constituted by an omnidirectional source, with the exception of the reservation made above on the angle a m ( Figure 1).
  • the means 1 When the multibeam antenna is used for reception, the means 1 must be constituted by a network, associated with a beam forming matrix (analog or digital) connected to a set of receivers; as is known, when the beam forming matrix is digital, it must be placed upstream of the receivers.
  • the beam-forming matrix like the receivers are included in the means 5.
  • the OZ axis can be vertical, but it is not at all necessary. It is thus also that the network 1 has been described as flat, but that it may be slightly concave, its concavity being turned towards the reflector 2, in order to facilitate the focusing of the energy that it radiates on this reflector. Finally, the use of the single-pole network as described in FIG. 3 is not limited to an antenna as described in FIG. 1, but extends to any type of antenna using a network.

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

Description

La présente invention a pour objet une antenne à couverture quasi torique à deux réflecteurs, pour l'émission et/ou la réception d'une onde hyperfréquence.The present invention relates to an antenna with quasi toroidal coverage with two reflectors, for the emission and / or reception of a microwave wave.

De nombreuses applications radar exigent une antenne susceptible de fournir des faisceaux tournants. Il est connu d'obtenir de tels faisceaux tournants à l'aide d'antennes tournantes; celles-ci présentent de nombreux inconvénients bien connus, notamment le manque de souplesse, qui ont conduit à développer des antennes statiques où le mouvement du faisceau est réalisé électroniquement.Many radar applications require an antenna capable of providing rotating beams. It is known to obtain such rotating beams using rotating antennas; these have many well-known drawbacks, in particular the lack of flexibility, which has led to the development of static antennas where the movement of the beam is carried out electronically.

Différentes réalisations d'antennes statiques sont connues, parmi lesquelles une structure constituée d'un ensemble d'antennes en forme de dalles, disposées selon un tronc de pyramide; la couverture obtenue est demi-sphérique et le fonctionnement en est satisfaisant; son inconvénient toutefois est d'avoir un prix de revient élevé. On connaît également une antenne dite antenne dôme, qui est constituée par un réseau d'éléments rayonnants permettant un balayage du faisceau selon un cône d'angle limité, de l'ordre de 90°, recouvert par un dôme hémisphérique, qui comporte des éléments déphasant les rayonnements le traversant, de sorte que l'angle de balayage du faisceau à l'extérieur du dôme soit égal à 180°. Cette structure a notamment pour avantage de diminuer le nombre d'éléments actifs nécessaires par rapport à la solution précédente, mais elle présente un certain nombre d'inconvénients parmi lesquels la complexité de fabrication du dôme qui doit inclure des déphaseurs, le volume de l'antenne résultante et les pertes se produisant par réflexion sur la paroi du dôme.Various embodiments of static antennas are known, including a structure consisting of a set of antenna shaped slabs, arranged in a trunk of a pyramid; the coverage obtained is semi-spherical and the operation is satisfactory; its disadvantage, however, is that it has a high cost price. An antenna known as a dome antenna is also known, which is constituted by a network of radiating elements allowing a scanning of the beam according to a cone of limited angle, of the order of 90 °, covered by a hemispherical dome, which comprises elements phase shifting the radiation passing through it, so that the scanning angle of the beam outside the dome is equal to 180 °. This structure has the particular advantage of reducing the number of active elements necessary compared to the previous solution, but it has a number of drawbacks among which the complexity of manufacturing the dome which must include phase shifters, the volume of the resulting antenna and the losses occurring by reflection on the wall of the dome.

On connaît par ailleurs, du document US-A- 3 551 676, un système aéroporté pour la détection optique d'avions, fonctionnant en réception; ce système comporte un ensemble de deux réflecteurs dont les concavités se font face, focalisant le rayonnement lumineux issus des avions à détecter sur un récepteur optique ponctuel. On connaît également, du document FR-A-1.392.013, une antenne microonde comportant une source en forme de cornet et deux réflecteurs; le réflecteur disposé devant le cornet est formé de deux arcs d'ellipse et présente un sommet dans l'axe de l'antenne; ces différents éléments sont disposés de sorte que le centre de phase du cornet soit l'un des foyers de l'ellipse et que l'autre foyer de l'ellipse soit celui du deuxième réflecteur, formé d'un arc de parabole. On connaît encore, du document FR-A-1.571.407, une antenne multifaisceau comportant une pluralité de cornets illuminant un réflecteur unique.Also known from document US-A-3,551,676 is an airborne system for the optical detection of aircraft, operating in reception; this system comprises a set of two reflectors whose concavities face each other, focusing the light radiation coming from the airplanes to be detected on a point optical receiver. Also known from document FR-A-1,392,013, a microwave antenna comprising a source in the shape of a horn and two reflectors; the reflector placed in front of the horn is formed by two arcs of ellipse and has a vertex in the axis of the antenna; these various elements are arranged so that the phase center of the horn is one of the focal points of the ellipse and that the other focal point of the ellipse is that of the second reflector, formed by a parabolic arc. Also known from document FR-A-1,571,407 is a multibeam antenna comprising a plurality of horns illuminating a single reflector.

La présente invention a pour objet une antenne statique permettant d'éviter ces inconvénients en utilisant un système à double réflexion, les réflecteurs étant passifs et de révolution, ce qui est relativement simple donc peu onéreux à fabriquer.The present invention relates to a static antenna making it possible to avoid these drawbacks by using a double reflection system, the reflectors being passive and of revolution, which is relatively simple and therefore inexpensive to manufacture.

Plus précisément, l'invention a pour objet une antenne telle que définie par la revendication 1.More specifically, the subject of the invention is an antenna as defined by claim 1.

D'autres objets, caractéristiques et résultats de l'invention ressortiront de la description suivante, illustrée par les dessins annexés où:

  • la figure 1 représente un mode de réalisation de l'antenne selon l'invention;
  • la figure 2 représente un mode de réalisation d'un réseau rayonnant utilisé dans l'antenne selon l'invention;
  • la figure 3a représente une variante de réalisation de ce réseau, et la figure 3b, un diagramme de rayonnement s'y rapportant; ,
  • la figure 4, représente le diagramme de couverture de l'antenne selon l'invention.
Other objects, characteristics and results of the invention will emerge from the following description, illustrated by the appended drawings where:
  • FIG. 1 represents an embodiment of the antenna according to the invention;
  • FIG. 2 represents an embodiment of a radiating network used in the antenna according to the invention;
  • FIG. 3a represents an alternative embodiment of this network, and FIG. 3b, a radiation diagram relating thereto; ,
  • FIG. 4 represents the coverage diagram of the antenna according to the invention.

Sur ces différentes figures, les mêmes références se rapportent aux mêmes éléments.In these different figures, the same references relate to the same elements.

Sur la figure 1, on a donc représenté un mode de réalisation de l'antenne selon l'invention. Afin de simplifier l'exposé, on décrit le fonctionnement de l'antenne dans le cas de l'émission, étant entendu qu'une telle antenne est adaptée aussi bien à l'émission qu'à la réception.In Figure 1, there is therefore shown an embodiment of the antenna according to the invention. In order to simplify the description, the operation of the antenna in the case of transmission is described, it being understood that such an antenna is suitable both for transmission and for reception.

Cette antenne comporte des moyens 1 pour émettre un rayon nement hyperfréquence, constitués par exemple par un réseau d'éléments rayonnants sensiblement plan et parallèle à un plan XOY, par exemple horizontal, de révolution autour d'un axe OZ normal à XOY. Il reçoit l'énergie à émettre de moyens 5, par exemple placés sous le réseau 1, sur un plan 6 supportant l'antenne, par exemple également sensiblement parallèle à XOY, et transmettant au réseau 1 l'énergie hyperfréquence et les commandes nécessaires par des moyens 51. Le réseau 1 peut être constitué par exemple par une pluralité de sources, alimentées par une matrice de circuits de formation d'un ou plusieurs faisceaux, représentée sur la figure 1 comme partie des moyens 5. Le réseau 1 peut également utiliser des déphaseurs comme illustré ci-dessous, ces divers dispositifs constituant des moyens de commande de la loi d'illumination du réseau en phase et éventuellement en amplitude.This antenna comprises means 1 for emitting a microwave radiation, constituted for example by a network of radiating elements substantially planar and parallel to a plane XOY, for example horizontal, of revolution around an axis OZ normal to XOY. It receives the energy to be transmitted from means 5, for example placed under the network 1, on a plane 6 supporting the antenna, for example also substantially parallel to XOY, and transmitting to the network 1 the microwave energy and the commands required by means 51. The network 1 can be constituted for example by a plurality of sources, supplied by a matrix of circuits for forming one or more beams, represented in FIG. 1 as part of the means 5. The network 1 can also use phase shifters as illustrated below, these various devices constituting means for controlling the law of illumination of the network in phase and possibly in amplitude.

L'énergie rayonnée par le réseau 1 est réfléchie par un réflecteur 2, de révolution autour de l'axe OZ, en forme de calotte sensiblement elliptique ou parabolique par exemple, dont la concavité est tournée vers le réseau 1.The energy radiated by the network 1 is reflected by a reflector 2, of revolution around the axis OZ, in the form of a substantially elliptical or parabolic cap for example, the concavity of which is turned towards the network 1.

Les rayonnements réfléchis par le réflecteur 2 sont réfléchis une seconde fois par un réflecteur 3 qui est, lui, en forme d'anneau entourant le réseau 1, cet anneau ayant une méridienne dont la concavité est tournée vers le réflecteur 2; le réflecteur 3 est également de révolution autour de l'axe OZ; il s'étend de préférence jusqu'au plan 6 supportant l'antenne.The rays reflected by the reflector 2 are reflected a second time by a reflector 3 which is itself in the form of a ring surrounding the network 1, this ring having a meridian whose concavity is turned towards the reflector 2; the reflector 3 is also of revolution around the axis OZ; it preferably extends to plane 6 supporting the antenna.

L'antenne comporte encore un radome 4, dont la présence n'est pas indispensable à son fonctionnement mais qui permet, outre les fonctions classiques d'un radome, de supporter le réflecteur 2. Ce radome 4 est sensiblement de révolution autour de l'axe OZ comme le réflecteur 2; il peut être cylindrique ou conique; il s'appuie de préférence d'une part sur la circonférence 20 du réflecteur 2 et d'autre part sur la circonférence extérieure 30 du réflecteur 3.The antenna also includes a radome 4, the presence of which is not essential for its operation but which allows, in addition to the conventional functions of a radome, to support the reflector 2. This radome 4 is substantially of revolution around the OZ axis like reflector 2; it can be cylindrical or conical; it is preferably based on the one hand on the circumference 20 of the reflector 2 and on the other hand on the outer circumference 30 of the reflector 3.

La figure 2 représente un mode de réalisation du réseau 1 de la figure 1.FIG. 2 represents an embodiment of the network 1 of FIG. 1.

Sur cette figure, on distingue une plaquette 12 en forme de disque d'axe OZ, comportant des éléments rayonnants 11 et 14 respectivement sur ses deux faces, par exemple du type dipôle.In this figure, there is a plate 12 in the form of a disc with an OZ axis, comprising radiating elements 11 and 14 respectively on its two faces, for example of the dipole type.

Chacun des éléments 11 est relié à un élément 14 par l'intermédiaire d'un circuit déphaseur 13. Le réseau 1 ainsi constitué est éclairé par une source ou un système de sources primaires hyperfréquences 10 d'axe OZ.Each of the elements 11 is connected to an element 14 by means of a phase shifting circuit 13. The network 1 thus formed is illuminated by a source or a system of primary microwave sources 10 of axis OZ.

Ainsi qu'il est connu, le rayonnement émis par le système 10 est capté par les éléments 11; après le déphasage induit par les circuits 13, le rayonnement est réémis par les éléments rayonnants 14. Les angles d'émission de l'énergie par l'ensemble des éléments rayonnants 14 sont déterminés par la valeur des déphasages conférés par chacun des circuits 13 et par les caractéristiques du système 10.As is known, the radiation emitted by the system 10 is picked up by the elements 11; after the phase shift induced by the circuits 13, the radiation is re-emitted by the radiating elements 14. The angles of emission of energy by all of the radiating elements 14 are determined by the value of the phase shifts conferred by each of the circuits 13 and by the characteristics of the system 10.

La figure 3a représente une vue partielle d'une variante de réalisation du réseau (1) utilisé dans l'antenne selon l'invention, dans lequel les éléments rayonnants 14 de la figure 2 sont du type unipôle.FIG. 3a represents a partial view of an alternative embodiment of the array (1) used in the antenna according to the invention, in which the radiating elements 14 of FIG. 2 are of the unipole type.

Sur la figure 3a, on a donc représenté une fraction de la plaquette 12 vue en coupe dans laquelle sont insérés des éléments rayonnants du type unipôle, repérés 15, qui sont des solides de révolution par exemple comme représenté sur la figure de forme conique, ce qui permet une plus grande largeur de bande.In FIG. 3a, a fraction of the plate 12 is seen in section in which are inserted radiating elements of the unipole type, marked 15, which are solids of revolution for example as shown in the figure of conical shape, this which allows for greater bandwidth.

Afin de diminuer le couplage entre les unipôles 15, on dispose dans une variante de réalisation des rainures 16 circulairement autour de chaque unipôle 15, ces rainures constituant des pièges pour l'onde hyperfréquence; la profondeur des rainures 16 est de l'ordre du quart de la longueur d'onde(À) émise. Comme représenté sur les figures, les rainures 16 peuvent être des cercles tangents.In order to reduce the coupling between the unipoles 15, there are in a variant embodiment grooves 16 circularly around each unipole 15, these grooves constituting traps for the microwave wave; the depth of the grooves 16 is of the order of a quarter of the wavelength (λ) emitted. As shown in the figures, the grooves 16 may be tangent circles.

Selon une réalisation préférée, les unipôles 15 sont disposés en quinconces.According to a preferred embodiment, the unipoles 15 are arranged in staggered rows.

A titre d'exemple, la hauteur des unipôles est de l'ordre de À/4, l'angle au sommet du cône formé par un unipôle peut être de l'ordre de 20° et le diamètre des cercles formés par les rainures, de l'ordre de À/2.By way of example, the height of the unipoles is of the order of λ / 4, the angle at the top of the cone formed by a unipole can be of the order of 20 ° and the diameter of the circles formed by the grooves, of the order of A / 2.

Sur la figure 3b, on a représenté en coordonnées polaires la section méridienne du diagramme de couverture (enveloppe des diagrammes de rayonnement possibles) obtenu avec un réseau 1 constitué d'unipôles tel qu'illustré sur la figure 3a.In FIG. 3b, the meridian section of the coverage diagram (envelope of the possible radiation diagrams) obtained with a network 1 made up of unipoles as shown in FIG. 3a is shown in polar coordinates.

Il apparaît que la couverture d'un tel réseau est de forme quasi torique, c'est-à-dire dont la directrice est une courbe fermée non circulaire, avec un zéro selon l'axe OZ et un zéro dans le plan XOY. L'angle d'ouverture maximal est par exemple compris entre 45° et 60°.It appears that the coverage of such a network is of quasi toroidal shape, that is to say of which the director is a closed non-circular curve, with a zero along the axis OZ and a zero in the plane XOY. The maximum opening angle is for example between 45 ° and 60 °.

En se reportant à la figure 1 on voit qu'un tel diagramme est particulièrement adapté à l'antenne selon l'invention, dans laquelle il est souhaitable d'éviter tout rayonnement dans un angle am pour que ne se produise pas de réflexion parasite et multiple entre le réseau 1 et le réflecteur 2.Referring to Figure 1 we see that such a diagram is particularly suitable for the antenna according to the invention, in which it is desirable to avoid any radiation at an angle a m so that parasitic reflection does not occur and multiple between network 1 and reflector 2.

La géométrie adoptée pour les réflecteurs 2 et 3 est fonction, à partir des caractéristiques du réseau 1, de la loi de couverture en site souhaitée pour l'ensemble de l'antenne, par exemple une loi cosécantée. Une telle loi est représentée à titre d'exemple sur la figure 4.The geometry adopted for the reflectors 2 and 3 is a function, from the characteristics of the network 1, of the law of coverage in site desired for the whole of the antenna, for example a cosecanted law. Such a law is shown by way of example in FIG. 4.

Sur cette figure, on a reporté le support 6 de l'antenne, son réseau 1 et ses deux réflecteurs 2 et 3. On a représenté en outre par une courbe 7 la loi de couverture de l'antenne, qui est quasi torique et limitée sensiblement, d'une part, par un plan parallèle à XOY et, d'autre part, par un cône d'axe OZ et d'angle au sommet y. Il apparaît que la couverture de l'antenne selon l'invention n'est pas hémisphérique; toutefois, cet inconvénient est considéré comme 'négligeable, du fait que les seules cibles qui ne peuvent être atteintes par une telle antenne sont celles qui sont voisines de OZ, c'est-à-dire généralement voisine du zénith, c'est-à-dire encore des cibles proches.In this figure, the support 6 of the antenna, its network 1 and its two reflectors 2 and 3 have been reported. In addition, a curve 7 represents the law of coverage of the antenna, which is almost toroidal and limited. substantially, on the one hand, by a plane parallel to XOY and, on the other hand, by a cone of axis OZ and of angle at the vertex y. It appears that the coverage of the antenna according to the invention is not hemispherical; however, this drawback is considered to be negligible, since the only targets which cannot be reached by such an antenna are those which are close to OZ, that is to say generally close to the zenith, i.e. - again say close targets.

Deux méthodes de calcul de réflecteurs sont possibles. La première méthode consiste à considérer le diagramme de chaque source en présence de réflecteurs, à écrire les expressions reliant les densités énergétiques au niveau du réseau 1, du premier puis du deuxième réflecteurs, puis à intégrer les expressions obtenues. Une autre méthode consiste à décomposer les illuminations du réseau et par suite les diagrammes résultants, en l'absence et en présence des réflecteurs, sur une base de fonctions orthogonales à symétrie circulaire. Le calcul montre qu'il existe une multiplicité de solutions possibles pour les équations des méridiennes des réflecteurs 2 et 3, le diagramme de couverture souhaité de l'antenne étant préalablement fixé; un diagramme de rayonnement particulier est alors obtenu par le choix de la loi de pondération du réseau en phase et éventuellement en amplitude; cela constitue bien entendu un avantage. Le choix définitif du couple de méridiennes se fait de préférence en utilisant la technique dite de conformation connue dans les systèmes de type Cassegrain et qui consiste, après avoir calculé les deux réflecteurs, à modifier par approximations successives la méridienne de l'un d'eux pour se rapprocher du diagramme de rayonnement recherché, puis modifier corrélativement le second réflecteur.Two methods of calculating reflectors are possible. The first method consists in considering the diagram of each source in the presence of reflectors, writing the expressions connecting the energy densities at the level of the network 1, the first then the second reflectors, then integrating the expressions obtained. Another method consists in decomposing the network illuminations and consequently the resulting diagrams, in the absence and in the presence of reflectors, on the basis of orthogonal functions with circular symmetry. The calculation shows that there are a multiplicity of possible solutions for the equations of the meridians of the reflectors 2 and 3, the desired coverage diagram of the antenna being previously fixed; a particular radiation pattern is then obtained by the choice of the weighting law of the network in phase and possibly in amplitude; this is of course an advantage. The final choice of the couple of meridians is preferably done using the technique known as conformation known in Cassegrain type systems and which consists, after having calculated the two reflectors, to modify by successive approximations the meridian of one of them to get closer to the desired radiation pattern, then modify the second reflector accordingly.

En se reportant à la figure 1, l'élément 4 peut être un radome continu ou un simple support, continu ou non, métallique ou diélectrique du réflecteur 2. Il peut en outre porter un filtre de polarisation, formé de fils conducteurs parallèles à la direction de polarisation à éliminer. Il peut également porter un polariseur permettant de rayonner par exemple une onde à polarisation circulaire: dans ce cas, il porte des fils conducteurs orientés à 45° par rapport à la polarisation incidente. Il peut encore constituer un écran mobile: il porte alors par exemple des fils conducteurs parallèles entre eux, par exemple parallèles à la direction OZ, portant en série chacun des diodes, rendues conductrices à volonté; dans cet exemple, il est possible de réaliser un écran mobile: la partie écran est alors constituée d'un ensemble de fils dont les diodes sont conductrices, réfléchissant ainsi l'énergie dont la polarisation est parallèle à eux.Referring to FIG. 1, the element 4 can be a continuous radome or a simple support, continuous or not, metallic or dielectric of the reflector 2. It can also carry a polarization filter, formed of conductive wires parallel to the polarization direction to be eliminated. It can also carry a polarizer making it possible to radiate for example a wave with circular polarization: in this case, it carries conductive wires oriented at 45 ° with respect to the incident polarization. It can also constitute a mobile screen: it then carries, for example, conductive wires tors parallel to each other, for example parallel to the direction OZ, carrying in series each of the diodes, made conductive at will; in this example, it is possible to produce a movable screen: the screen part then consists of a set of wires whose diodes are conductive, thus reflecting the energy whose polarization is parallel to them.

On a décrit ci-dessus une antenne utilisant des focalisateurs passifs, qui permettent de moduler le gain du réseau et par là-même de limiter le nombre d'éléments actifs nécessaires, pour un gain donné, par rapport aux antennes à rayonnement direct. De plus, cette antenne utilise le phénomème de réflexion, évitant ainsi les pertes aux interfaces rencontrées dans les systèmes à transmission. En outre, elle utilise deux réflecteurs, ce qui d'une part confère une plus grande souplesse dans le choix et la mise au point des réflecteurs et d'autre part limite l'encombrement de l'antenne. Par ailleurs, les réflecteurs sont passifs et de révolution, ce qui est de fabrication relativement simple et peu onéreuse. Enfin, cette antenne est adaptée au rayonnement de toute polarisation: polarisation constante dans tout le diagramme et parallèle à OZ si le réseau est constitué d'unipôles, dans le plan XOY si le réseau est constitué de boucles de courant parallèles à XOY, et circulaire si le réseau est constitué par exemple d'hélices ou de toute autre source de polarisation circulaire.An antenna has been described above using passive focusing devices, which make it possible to modulate the gain of the array and thereby limit the number of active elements necessary, for a given gain, compared to direct radiation antennas. In addition, this antenna uses the reflection phenomenon, thus avoiding losses at the interfaces encountered in transmission systems. In addition, it uses two reflectors, which on the one hand gives greater flexibility in the choice and focusing of the reflectors and on the other hand limits the size of the antenna. Furthermore, the reflectors are passive and of revolution, which is relatively simple and inexpensive to manufacture. Finally, this antenna is adapted to the radiation of any polarization: constant polarization throughout the diagram and parallel to OZ if the network consists of unipoles, in the XOY plane if the network consists of current loops parallel to XOY, and circular if the network consists for example of propellers or any other source of circular polarization.

L'antenne décrite ci-dessus est donc susceptible d'émettre et de recevoir un faisceau directif balayant électroniquement la zone de couverture de l'antenne. Elle est également susceptible de fonctionner en régime multifaisceau. Dans le cas d'une antenne multifaisceau utilisée uniquement à l'émission, les moyens 1 peuvent être quelconques et par exemple constitués par une source omnidirectionnelle, à la réserve près faite ci-dessus sur l'angle am (figure 1). Lorsque l'antenne multifaisceau est utilisée en réception, les moyens 1 doivent être constitués par un réseau, associés à une matrice de formation de faisceaux (analogique ou numérique) connectée à un ensemble de récepteurs; ainsi qu'il est connu, lorsque la matrice de formation de faisceaux est numérique, elle doit être placée en amont des récepteurs. Sur le schéma de la figure 1, la matrice de formation de faisceaux comme les récepteurs sont inclus dans les moyens 5.The antenna described above is therefore capable of transmitting and receiving a directive beam electronically scanning the antenna coverage area. It is also likely to operate in multibeam mode. In the case of a multibeam antenna used only for transmission, the means 1 can be any and for example constituted by an omnidirectional source, with the exception of the reservation made above on the angle a m (Figure 1). When the multibeam antenna is used for reception, the means 1 must be constituted by a network, associated with a beam forming matrix (analog or digital) connected to a set of receivers; as is known, when the beam forming matrix is digital, it must be placed upstream of the receivers. In the diagram of FIG. 1, the beam-forming matrix like the receivers are included in the means 5.

La description faite ci-dessus l'a été à titre d'exemple non limitatif; cest ainsi par exemple que l'axe OZ peut être vertical, mais que ce n'est nullement nécessaire. C'est ainsi également que le réseau 1 a été décrit plan, mais qu'il peut être légèrement concave, sa concavité étant tournée vers le réflecteur 2, afin de faciliter la focalisation de l'énergie qu'il rayonne sur ce réflecteur. Enfin, l'utilisation du réseau d'unipôles tel que décrit figure 3 n'est pas limitée à une antenne telle que décrite figure 1, mais s'étend à tout type d'antenne utilisant un réseau.The description given above has been given by way of nonlimiting example; for example, the OZ axis can be vertical, but it is not at all necessary. It is thus also that the network 1 has been described as flat, but that it may be slightly concave, its concavity being turned towards the reflector 2, in order to facilitate the focusing of the energy that it radiates on this reflector. Finally, the use of the single-pole network as described in FIG. 3 is not limited to an antenna as described in FIG. 1, but extends to any type of antenna using a network.

Claims (9)

1. A static antenna with quasitoroidal coverage, adapted to ensure the emission and/or reception of a microwave beam, the antenna admitting substantially an axis of revolution (OZ) and comprising: a microwave energy source susceptible of emitting or receiving the microwave beam, the source being centered on the axis of revolution; a first concave reflector (2) centered on the axis of revolution; a second reflector (3) of annular shape, centered on the axis of revolution and extending at that side of the source (1) which is remote from the first reflector (2), whose meridien has a concavity directed at each of its points towards the first reflector (2); the source and the two reflectors being arranged in such a way that the greatest part of the energy emitted or received by the source is reflected by the two reflectors; the antenna being characterized in that the beam is an electronically scanned directive beam; that the microwave energy source is constituted by a network of radiating elements, each of the radiating elements being associated to corresponding means for phase-shifting the micro-wave passing therethrouugh, the network being susceptible of emitting or receiving the beam in a direction which can be controlled electronically by controlling the phase-shifting means, the network being placed perpendicular to the axis of revolution; in that the first reflector (2) has the shape of a hood whose concavity is, at each of its points, directed towards the network (1); and that the contour of the network is inscribed within the inner contour of the annular reflector (3).
2. An antenna according to claim 1, characterized in that it further comprises means (4) for supporting the first reflector (2), adapted to support the periphery (20) of the latter.
3. An antenna according to claim 2, characterized in that the supporting means (4) form in addition a radome.
4. An antenna according to claim 2 or 3, characterized in that the supporting means (4) further form a polarizer or a polarizing filter.
5. An antenna according to claim 2 or 3, characterized in that the supporting means form in addition a movable screen.
6. An antenna according to any one of the preceding claims, characterized in that the first reflector (2) has the shape of a substantially elliptic or else parabolic hood.
7. An antenna according to any one of the preceding claims, characterized in that the network (1) comprises a plurality of radiating elements of the unipolar type (15).
8. An antenna according to one of the preceding claims, characterised in that the network (1) comprises means for controlling its law of illumination.
9. An antenna according to one of the preceding claims, of the multi-beam type, insuring reception of a microwave beam, characterised in that the network (1) is associated to a matrix of beam formation connected to a set of receivers.
EP84401409A 1983-07-08 1984-07-03 Dual reflector antenna with quasitoroidal coverage Expired - Lifetime EP0131512B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8311430 1983-07-08
FR8311430A FR2548836B1 (en) 1983-07-08 1983-07-08 QUASI-TORIC COVERED ANTENNA WITH TWO REFLECTORS

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EP0131512A1 EP0131512A1 (en) 1985-01-16
EP0131512B1 true EP0131512B1 (en) 1990-09-05

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EP (1) EP0131512B1 (en)
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FR (1) FR2548836B1 (en)

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FR2548836B1 (en) 1986-02-21
US4740791A (en) 1988-04-26
DE3483122D1 (en) 1990-10-11
FR2548836A1 (en) 1985-01-11
EP0131512A1 (en) 1985-01-16

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