EP1330853A1 - Double-beam antenna with two sources - Google Patents

Double-beam antenna with two sources

Info

Publication number
EP1330853A1
EP1330853A1 EP01984045A EP01984045A EP1330853A1 EP 1330853 A1 EP1330853 A1 EP 1330853A1 EP 01984045 A EP01984045 A EP 01984045A EP 01984045 A EP01984045 A EP 01984045A EP 1330853 A1 EP1330853 A1 EP 1330853A1
Authority
EP
European Patent Office
Prior art keywords
prism
lens
source
sources
antenna
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP01984045A
Other languages
German (de)
French (fr)
Inventor
Eric Thales Int. Prop. ESTEBE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Thales SA
Original Assignee
Thales SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Thales SA filed Critical Thales SA
Publication of EP1330853A1 publication Critical patent/EP1330853A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H01Q25/007—Antennas or antenna systems providing at least two radiating patterns using two or more primary active elements in the focal region of a focusing device
    • H01Q25/008—Antennas or antenna systems providing at least two radiating patterns using two or more primary active elements in the focal region of a focusing device lens fed multibeam arrays
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/27—Adaptation for use in or on movable bodies
    • H01Q1/32—Adaptation for use in or on road or rail vehicles
    • H01Q1/3208—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used
    • H01Q1/3233—Adaptation for use in or on road or rail vehicles characterised by the application wherein the antenna is used particular used as part of a sensor or in a security system, e.g. for automotive radar, navigation systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q15/00—Devices for reflection, refraction, diffraction or polarisation of waves radiated from an antenna, e.g. quasi-optical devices
    • H01Q15/02—Refracting or diffracting devices, e.g. lens, prism
    • 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
    • H01Q19/06—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 refracting or diffracting devices, e.g. lens
    • 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
    • H01Q19/06—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 refracting or diffracting devices, e.g. lens
    • H01Q19/062—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 refracting or diffracting devices, e.g. lens for focusing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H01Q25/007—Antennas or antenna systems providing at least two radiating patterns using two or more primary active elements in the focal region of a focusing device

Definitions

  • the present invention relates to a two-beam antenna with two sources. It applies in particular to millimeter radar antennas, such as for example radars for automobiles.
  • the measurements are generally carried out by the known technique of ecartometry, by means of detections in the sum and difference channels of a monopulse antenna.
  • This antenna notably includes a primary source and a lens.
  • the primary source is placed at the focal point of the microwave lens and illuminates this lens.
  • the beam radiated by the antenna, at the exit of the lens, is perpendicular to the plane of the latter and parallel to its focal axis.
  • the radar must cover a sufficiently wide angular range. It is indeed important not to miss a potential obstacle or a vehicle liable to be struck by the carrier vehicle.
  • one solution notably consists in widening the antenna beam, more particularly the beams of its sum and difference channels, since one is in the case of a measurement by deviation measurement.
  • such a solution loses measurement accuracy.
  • Another solution is to double the beams, without increasing their width. Wider angular coverage is thus obtained without losing precision.
  • a second source microwave is added to the previous one, near the focal point of the lens.
  • the minimum angle between the two beams at the exit of the lens depends on this minimum distance. If it is desired to keep the beams sufficiently fine for reasons of measurement accuracy, this minimum distance then has the consequence that the two beams scan disjoint angular domains.
  • the two beams must maintain at least a slight overlap between them.
  • a solution with two juxtaposed antennas has the disadvantages of increasing the overall size of the sensor, and also the costs.
  • the subject of the invention is a two-beam antenna with two sources comprising a microwave lens, a first source Si being located in the vicinity of the focal point of the lens and the second source S 2 being located at a distance d from the first source, in the vicinity of the plane perpendicular to the optical axis containing the focal point.
  • the antenna comprises a polarization filter prism located on the side of the lens opposite to the sources, the two sources having crossed polarizations and the first source Si having a polarization substantially perpendicular to the blades of the prism.
  • the output profile of the prism can be adapted to compensate for the aberrations due to the defocusing of the sources.
  • this profile can be substantially symmetrical with respect to a point P passing through the focal axis of the lens, with a convex part and a concave part.
  • the main advantages of the invention are that it makes it possible to produce a compact and economical two-source antenna, and that it is simple to implement.
  • FIG. 7 another possible embodiment of an antenna according to the invention notably compensating for the aberrations due to the defocusing of the second source;
  • - Figures 8a and 8b a possible embodiment of the assembly consisting of the lens and the prism;
  • FIG. 1 schematically shows a lens antenna at a source.
  • the antenna therefore comprises a lens 1 and a microwave source S-i.
  • the latter is at the focal distance f of the lens. More particularly, it is preferably located at the focal point of the lens.
  • the latter is therefore lit by a source placed in its home.
  • the radiated microwave beam 2 is then perpendicular to the plane of the lens and parallel to the focal axis 3.
  • the lens 1 is made of dielectric material, of relative dielectric constant ⁇ r greater than 1.
  • the relative dielectric constant ⁇ r can be of the order of 2.5 to 3.5.
  • Figures 2a, 2b and 2c show different possible forms, and not limiting, for this lens. It may have a convex face and a planar face, the planar face being oriented towards the source Si as illustrated in FIG. 2a or the convex face being oriented towards the source S ⁇ as illustrated in FIG. 2b.
  • the lens can also have, for example, a bi-convex shape as illustrated in FIG. 2c.
  • FIG. 3 illustrates an exemplary embodiment of a lens antenna where a second source S 2 is associated with the first source Si.
  • the second source S 2 is located at the focal distance f of the lens, and at a distance d from the first source. This second source is therefore located in the plane 31 perpendicular to the optical axis 3 passing through the focal point of the lens and offset by a distance d relative to this focal point. This offset relative to the focal point causes a deviation of the corresponding beam 21 relative to the axis 3 of the lens, at the output of the latter.
  • the angle A 2 between the beam 2 coming from the first source Si and the beam 21 coming from the second source S 2 is substantially equal to the angle Ai at which these two sources Si, S 2 are seen at the center of the lens . This angle depends on the distance d between the two sources.
  • the mechanical size linked to the installation of the second source S 2 means that it is not possible to reduce the distance d below a given threshold. Consequently the angle Ai, and therefore the minimum angle A 2 may remain too large for a given application, for example for a two-beam antenna of a millimeter radar.
  • the angle Ai is indeed such that the two beams coming from the two sources Si, S 2 remain disjoint.
  • FIG. 4a and 4b schematically show a possible embodiment of an antenna according to the invention.
  • a polarization filter prism 41 is associated with the lens 1, the prism 41 being on the side of the lens opposite to the sources Si, S 2 as shown in FIG. 4a.
  • FIG. 4b shows a possible structure of the prism 41 by a view along F. It comprises an array of blades 42 in parallel. More particularly, they are parallel to the direction of the beams 2, 21. These blades are for example made of metal or of dielectric with metallized walls.
  • the prism is for example of circular section. Its profile is for example of trapezoidal shape, as illustrated in FIG. 4a, or approaching it. In other words, the length of the prism increases from one end 43 to the opposite end 44.
  • FIG. 5 illustrates the effect of the prism 41.
  • the latter performs a selective beam deflection as a function of the polarization of the beam.
  • the two sources Si, S 2 are chosen with crossed polarizations.
  • the beam 2 coming from the first source Si has a polarization perpendicular to the blades 42 of the prism, while beam 21 coming from the second source S 2 has a polarization parallel to the blades 42.
  • these two beams are presented as attacking both the prism 41 perpendicularly.
  • the beam 2 of the first source Si is not deflected and the beam 21 of the second source S 2 is deflected.
  • the wavelength guided through the prism is in fact little modified compared to the wavelength in free space.
  • the wavelength guided through the prism is greater than the wavelength in free space. A phase shift is thus obtained depending on the length of the prism passed through.
  • the prism 41 therefore makes it possible to reduce the angle A 2 between the two beams 2, 21 at the antenna output, the angle Ai remaining the same.
  • the output is no longer the lens output but the output of the prism associated with it.
  • the beam 2 from the first source Si is not at first approximation deflected by the prism.
  • the beam deflection, of angle A 2 caused by the offset d of the second source S 2 is reduced thanks to the prism.
  • the angle B 2 between the beams with prism is less than the angle A 2 without prism.
  • the addition of the prism 41 therefore makes it possible to increase the offset d between the two sources S ⁇ S 2 and makes it possible to install two juxtaposed sources of non-congested dimensions. negligible without superposition of these.
  • FIG. 7 illustrates another possible embodiment of an antenna according to the invention which makes it possible to correct the aberrations due to the defocusing of the second source S 2 .
  • the wave emitted at the output of the prism is plane, that is to say equiphase on a plane.
  • the offset d of the second source S 2 with respect to the focus means that the corresponding transmitted wave is no longer entirely flat, which has the particular effect of increasing the level of the secondary lobes of the antenna.
  • the profile of the prism is modified compared to that of the previous figures.
  • the output profile 71 of the prism is no longer a straight line as shown in dotted lines but has a curve for example symmetrical with respect to a point P.
  • This point P is located on the output profile, substantially at the intersection with the focal axis 3 of the lens 1.
  • the half-profile which is on the same side as the second source S 2 with respect to the focal axis 3 has a concave shape while the other half-profile has a convex shape.
  • FIG. 8a and 8b show a possible embodiment of the assembly consisting of the lens 1 and the prism 41.
  • the lens and the prism are produced in the same dielectric block.
  • FIG. 8a represents a profile view of the single part 1
  • FIG. 8b represents a front view, along F, of the latter.
  • the blades 42 of the prism are for example molded in the dielectric block.
  • the dielectric constant ⁇ has blades, greater than the dielectric constant o of the air included in the free space 81 between the blades, is sufficient to ensure the function of polarization filter prism, at least to ensure a reduction in the angle A 2 .
  • the walls of the blades are therefore not necessarily covered with a metallic layer. Since the lens and the prism form a single block, the dielectric constant ⁇ to the blades is for example also the dielectric constant of the lens.
  • the blades 42 are for example made of metal and are embedded in the dielectric block. In this case, it is the space 81 between the blades which comprises for example the same dielectric constant as the lens.
  • Figures 9a and 9b show two other exemplary embodiments where the prism 41 and the radome 91 of the antenna forms only one piece.
  • the radome 91 for example planar, is molded with the prism 41 in the same dielectric material or bonded on the prism.
  • the compensation profile 71 is for example here opposite the lens 1. In the case of a lens with a convex face and a flat face, the latter may face the prism as shown in FIG. 9a or on the opposite side as illustrated in Figure 9b.
  • the blades 42 of the prism can be molded in the dielectric material or in metal as in the case of FIGS. 8a and 8b above.
  • FIG. 6 shows an exemplary embodiment where the second source S 2 is located in the plane perpendicular to the optical axis containing the focal point.
  • the invention nevertheless remains valid if this second source S 2 is placed outside this plane. It is the same if the first source Si is not exactly placed at the focal point of the lens. This difference in position can then be compensated for by playing on the profile 71 of the lens.
  • the first source Si therefore does not need to be placed exactly at the focal point of the lens. This allows in particular a simple implementation of the invention.
  • the microwave lens 1 described above, in particular in FIGS. 2a, 2b and 2c, is a dielectric lens.
  • the use of a metallic lens or of a metallized dielectric material made up of an array of double polarization waveguides is also possible.
  • the lens is then in the form of a grid of non-constant thickness, the holes of which constitute the transmission guides.
  • the focusing effect of the lens uses the difference between the wavelength guided in the array of guides and the wavelength in free space.

Abstract

The invention concerns an antenna comprising a microwave lens (1), having a first source (S1) located proximate to the lens focus and the second source (S2) located at a distance d from the first source, proximate to the plane perpendicular to the focal axis (3). The antenna comprises a polarisation filter prism (41) located on the side of the lens opposite to the sources, the two sources having orthogonal polarisations and the first source (S1) having a polarisation substantially perpendicular to the prism plates. The output profile (71) of the prism can be adapted to compensate aberrations caused by defocusing of the sources. In particular, said profile can be substantially symmetrical relative to a point P passing through the focal axis of the lens, with a convex part and a concave part. The invention is applicable in particular to millimetric radar antennae, such as for example motor vehicle radar

Description

Antenne bi-faisceaux à deux sources Two-beam two-beam antenna
La présente invention concerne une antenne bi-faisceaux à deux sources. Elle s'applique notamment pour les antennes de radars millimétriques, tels que par exemple des radars pour automobiles.The present invention relates to a two-beam antenna with two sources. It applies in particular to millimeter radar antennas, such as for example radars for automobiles.
Il est connu d'équiper des véhicules de moyens de mesures de distance et/ou de vitesse de véhicules ou d'obstacles les précédant. Ces moyens, par exemple à base de techniques radars, permettent notamment d'effectuer une régulation automatique de vitesse des véhicules en fonction du trafic. Ils sont généralement qualifiés dans la littérature anglo-saxonne par le sigle ACC correspondant à l'expression « Automotive Cruise Control ». Les radars utilisés, fonctionnant en bande millimétrique, fournissent des informations d'angle, de distance et de vitesse du véhicule porteur par rapport à des obstacles potentiels ou par rapport à des véhicules le précédant. Ces informations peuvent être exploitées de différentes manières. En particulier, elles peuvent générer une alerte pour le conducteur ou même entraîner une action directe sur le système de freinage et/ou d'accélération. Les mesures sont généralement effectuées par la technique connue d'écartometrie, par l'intermédiaire de détections dans les voies somme et différence d'une antenne monopulse. Cette antenne comporte notamment une source primaire et une lentille. La source primaire est placée au foyer de la lentille hyperfréquence et éclaire cette lentille. Le faisceau rayonné par l'antenne, en sortie de la lentille, est perpendiculaire au plan de cette dernière et parallèle à son axe focal.It is known to equip vehicles with means for measuring distance and / or speed of vehicles or of obstacles preceding them. These means, for example based on radar techniques, make it possible in particular to perform automatic speed regulation of vehicles as a function of traffic. They are generally qualified in Anglo-Saxon literature by the acronym ACC corresponding to the expression "Automotive Cruise Control". The radars used, operating in millimeter band, provide information on the angle, distance and speed of the carrier vehicle in relation to potential obstacles or in relation to vehicles in front. This information can be used in different ways. In particular, they can generate an alert for the driver or even lead to a direct action on the braking and / or acceleration system. The measurements are generally carried out by the known technique of ecartometry, by means of detections in the sum and difference channels of a monopulse antenna. This antenna notably includes a primary source and a lens. The primary source is placed at the focal point of the microwave lens and illuminates this lens. The beam radiated by the antenna, at the exit of the lens, is perpendicular to the plane of the latter and parallel to its focal axis.
Pour être efficace, le radar doit couvrir un domaine angulaire suffisamment large. Il est en effet important de ne pas manquer un obstacle potentiel ou un véhicule susceptible d'être percuté par le véhicule porteur. Pour augmenter le domaine angulaire, une solution consiste notamment à élargir le faisceau d'antenne, plus particulièrement les faisceaux de ses voies somme et différence, puisque l'on est dans le cas d'une mesure par écartométrie. Cependant une telle solution perd en précision de mesure.To be effective, the radar must cover a sufficiently wide angular range. It is indeed important not to miss a potential obstacle or a vehicle liable to be struck by the carrier vehicle. To increase the angular range, one solution notably consists in widening the antenna beam, more particularly the beams of its sum and difference channels, since one is in the case of a measurement by deviation measurement. However, such a solution loses measurement accuracy.
Une autre solution consiste à doubler les faisceaux, sans augmenter leur largeur. On obtient ainsi une couverture angulaire plus large sans toutefois perdre en précision. A cet effet, une deuxième source hyperfréquence est ajoutée à la précédente, à proximité du foyer de la lentille. Pour des raisons d'encombrement mécanique, une distance minimale demeure entre les deux sources. L'angle minimal entre les deux faisceaux en sortie de la lentille dépend de cette distance minimale. Si l'on souhaite garder des faisceaux suffisamment fins pour des raisons de précision de mesure, cette distance minimale a alors pour conséquence que les deux faisceaux balayent des domaines angulaires disjoints. Or, en raison du traitement radar, il faut que les deux faisceaux conservent au moins un léger chevauchement entre eux. Une solution à deux antennes juxtaposées (deux sources et deux lentilles) a pour inconvénients d'augmenter l'encombrement global du capteur, et aussi les coûts. Dans le domaine des radars pour automobiles, l'encombrement et le coût sont notamment deux paramètres significatifs qui doivent être les plus faibles possibles. Un but de l'invention est de pallier les inconvénients précités. A cet effet, l'invention a pour objet une antenne bi-faisceaux à deux sources comportant une lentille hyperfréquence, une première source Si étant située au voisinage du foyer de la lentille et la deuxième source S2 étant située à une distance d de la première source, au voisinage du plan perpendiculaire à l'axe optique contenant le foyer. L'antenne comporte un prisme filtre de polarisation situé du côté de la lentille opposé aux sources, les deux sources ayant des polarisations croisées et la première source Si ayant une polarisation sensiblement perpendiculaire aux lames du prisme.Another solution is to double the beams, without increasing their width. Wider angular coverage is thus obtained without losing precision. For this purpose, a second source microwave is added to the previous one, near the focal point of the lens. For reasons of mechanical bulk, a minimum distance remains between the two sources. The minimum angle between the two beams at the exit of the lens depends on this minimum distance. If it is desired to keep the beams sufficiently fine for reasons of measurement accuracy, this minimum distance then has the consequence that the two beams scan disjoint angular domains. However, due to the radar processing, the two beams must maintain at least a slight overlap between them. A solution with two juxtaposed antennas (two sources and two lenses) has the disadvantages of increasing the overall size of the sensor, and also the costs. In the field of speed cameras for cars, space and cost are in particular two significant parameters which must be as low as possible. An object of the invention is to overcome the aforementioned drawbacks. To this end, the subject of the invention is a two-beam antenna with two sources comprising a microwave lens, a first source Si being located in the vicinity of the focal point of the lens and the second source S 2 being located at a distance d from the first source, in the vicinity of the plane perpendicular to the optical axis containing the focal point. The antenna comprises a polarization filter prism located on the side of the lens opposite to the sources, the two sources having crossed polarizations and the first source Si having a polarization substantially perpendicular to the blades of the prism.
Le profil de sortie du prisme peut être adapté pour compenser les aberrations dues à la défocalisation des sources. En particulier, ce profil peut être sensiblement symétrique par rapport à un point P passant par l'axe focal de la lentille, avec une partie convexe et une partie concave.The output profile of the prism can be adapted to compensate for the aberrations due to the defocusing of the sources. In particular, this profile can be substantially symmetrical with respect to a point P passing through the focal axis of the lens, with a convex part and a concave part.
L'invention a pour principaux avantages, qu'elle permet de réaliser une antenne à deux sources compacte et économique, et qu'elle est simple à mettre en œuvre.The main advantages of the invention are that it makes it possible to produce a compact and economical two-source antenna, and that it is simple to implement.
D'autres caractéristiques et avantages de l'invention apparaîtront à l'aide de la description qui suit faite en regard de dessins annexés qui représentent : - la figure 1 , une antenne à lentille à une source ; - les figures 2a, 2b et 2c, différentes formes possibles de lentilles hyperfréquence ;Other characteristics and advantages of the invention will become apparent from the following description given with reference to the appended drawings which represent: - Figure 1, a lens antenna at a source; - Figures 2a, 2b and 2c, different possible forms of microwave lenses;
- la figure 3, un exemple de réalisation d'une antenne à lentille à deux sources ; - les figures 4a et 4b, un mode de réalisation possible d'une antenne selon l'invention ;- Figure 3, an embodiment of a lens antenna with two sources; - Figures 4a and 4b, a possible embodiment of an antenna according to the invention;
- la figure 5, l'effet d'un prisme filtre de polarisation utilisé dans une antenne selon l'invention ;- Figure 5, the effect of a polarization filter prism used in an antenna according to the invention;
- la figure 6, une illustration de la diminution de l'angle séparant les faisceaux de sortie par l'utilisation d'un prisme filtre de polarisation dans une antenne selon l'invention ;- Figure 6, an illustration of the decrease in the angle separating the output beams by the use of a polarization filter prism in an antenna according to the invention;
- la figure 7, un autre mode de réalisation possible d'une antenne selon l'invention compensant notamment les aberrations dues à la défocalisation de la deuxième source ; - les figures 8a et 8b, un exemple de réalisation possible de l'ensemble constitué de la lentille et du prisme ;- Figure 7, another possible embodiment of an antenna according to the invention notably compensating for the aberrations due to the defocusing of the second source; - Figures 8a and 8b, a possible embodiment of the assembly consisting of the lens and the prism;
- les figures 9a et 9b, deux autres exemples de réalisation où le prisme et le radôme de l'antenne ne forme qu'une seule pièce.- Figures 9a and 9b, two other exemplary embodiments where the prism and the radome of the antenna forms only one piece.
La figure 1 présente de façon schématique une antenne à lentille à une source. L'antenne comporte donc une lentille 1 et une source hyperfréquence S-i. Cette dernière est à la distance focale f de la lentille. Plus particulièrement, elle est de préférence située au foyer de la lentille. Cette dernière est donc éclairée par une source placée en son foyer. Le faisceau hyperfréquence rayonné 2 est alors perpendiculaire au plan de la lentille et parallèle à l'axe focal 3.Figure 1 schematically shows a lens antenna at a source. The antenna therefore comprises a lens 1 and a microwave source S-i. The latter is at the focal distance f of the lens. More particularly, it is preferably located at the focal point of the lens. The latter is therefore lit by a source placed in its home. The radiated microwave beam 2 is then perpendicular to the plane of the lens and parallel to the focal axis 3.
La lentille 1 est en matériau diélectrique, de constante diélectrique relative εr supérieure à 1. Typiquement, la constante diélectrique relative εr peut être de l'ordre de 2,5 à 3,5. Les figures 2a, 2b et 2c montrent différentes formes possibles, et non limitatives, pour cette lentille. Elle peut avoir une face convexe et une face plane, la face plane étant orientée vers la source Si comme l'illustre la figure 2a ou la face convexe étant orientée vers la source SÏ comme l'illustre la figure 2b. Enfin, la lentille peut encore avoir par exemple une forme bi-convexe comme l'illustre la figure 2c. La figure 3 illustre un exemple de réalisation d'une antenne à lentille où une deuxième source S2 est associée à la première source S-i. La deuxième source S2 est située à la distance focale f de la lentille, et à une distance d de la première source. Cette seconde source est donc située dans le plan 31 perpendiculaire à l'axe optique 3 passant par le foyer de la lentille et décalée d'une distance d par rapport à ce foyer. Ce décalage par rapport au foyer provoque une déviation du faisceau 21 correspondant par rapport à l'axe 3 de la lentille, en sortie de cette dernière. L'angle A2 entre le faisceau 2 issu de la première source Si et le faisceau 21 issu de la deuxième source S2 est sensiblement égal à l'angle Ai sous lequel sont vues ces deux sources S-i, S2 au centre de la lentille. Cet angle dépend de la distance d entre les deux sources. L'encombrement mécanique lié à l'installation de la deuxième source S2 fait qu'il n'est pas possible de réduire la distance d en dessous d'un seuil donné. En conséquence l'angle A-i, et donc l'angle A2 minimum peut rester trop grand pour une application donnée, par exemple pour une antenne bi-faisceau d'un radar millimétrique. L'angle Ai est en effet tel que les deux faisceaux issus des deux sources S-i, S2 restent disjoints.The lens 1 is made of dielectric material, of relative dielectric constant ε r greater than 1. Typically, the relative dielectric constant ε r can be of the order of 2.5 to 3.5. Figures 2a, 2b and 2c show different possible forms, and not limiting, for this lens. It may have a convex face and a planar face, the planar face being oriented towards the source Si as illustrated in FIG. 2a or the convex face being oriented towards the source S Ï as illustrated in FIG. 2b. Finally, the lens can also have, for example, a bi-convex shape as illustrated in FIG. 2c. FIG. 3 illustrates an exemplary embodiment of a lens antenna where a second source S 2 is associated with the first source Si. The second source S 2 is located at the focal distance f of the lens, and at a distance d from the first source. This second source is therefore located in the plane 31 perpendicular to the optical axis 3 passing through the focal point of the lens and offset by a distance d relative to this focal point. This offset relative to the focal point causes a deviation of the corresponding beam 21 relative to the axis 3 of the lens, at the output of the latter. The angle A 2 between the beam 2 coming from the first source Si and the beam 21 coming from the second source S 2 is substantially equal to the angle Ai at which these two sources Si, S 2 are seen at the center of the lens . This angle depends on the distance d between the two sources. The mechanical size linked to the installation of the second source S 2 means that it is not possible to reduce the distance d below a given threshold. Consequently the angle Ai, and therefore the minimum angle A 2 may remain too large for a given application, for example for a two-beam antenna of a millimeter radar. The angle Ai is indeed such that the two beams coming from the two sources Si, S 2 remain disjoint.
Les figures 4a et 4b présentent de façon schématique un mode de réalisation possible d'une antenne selon l'invention. Un prisme filtre de polarisation 41 est associé à la lentille 1 , le prisme 41 étant du côté de la lentille opposé aux sources S-i, S2 comme le montre la figure 4a. La figure 4b montre une structure possible du prisme 41 par une vue suivant F. Il comporte un réseau de lames 42 en parallèle. Plus particulièrement, elles sont parallèles à la direction des faisceaux 2, 21. Ces lames sont par exemple en métal ou en diélectrique à parois métallisées. Le prisme est par exemple de section circulaire. Son profil est par exemple de forme trapézoïdale, comme l'illustre la figure 4a, ou s'en rapprochant. En d'autres termes, la longueur du prisme croît d'une extrémité 43 à l'extrémité opposée 44.Figures 4a and 4b schematically show a possible embodiment of an antenna according to the invention. A polarization filter prism 41 is associated with the lens 1, the prism 41 being on the side of the lens opposite to the sources Si, S 2 as shown in FIG. 4a. FIG. 4b shows a possible structure of the prism 41 by a view along F. It comprises an array of blades 42 in parallel. More particularly, they are parallel to the direction of the beams 2, 21. These blades are for example made of metal or of dielectric with metallized walls. The prism is for example of circular section. Its profile is for example of trapezoidal shape, as illustrated in FIG. 4a, or approaching it. In other words, the length of the prism increases from one end 43 to the opposite end 44.
La figure 5 illustre l'effet du prisme 41. Ce dernier effectue une déviation de faisceau sélective en fonction de la polarisation du faisceau. Les deux sources S-i, S2 sont choisies avec des polarisations croisées. Le faisceau 2 provenant de la première source Si présente une polarisation perpendiculaire aux lames 42 du prisme, alors que le faisceau 21 provenant de la deuxième source S2 présente une polarisation parallèle aux lames 42. Pour simplifier la présentation, ces deux faisceaux sont présentés comme attaquant tous deux le prisme 41 perpendiculairement. Le faisceau 2 de la première source Si n'est pas dévié et le faisceau 21 de la deuxième source S2 est dévié. Lorsque la polarisation, c'est-à-dire que le champ électrique, est perpendiculaire aux lames, la longueur d'onde guidée à travers le prisme est en fait peu modifiée par rapport à la longueur d'onde en espace libre. En revanche, lorsque la polarisation est parallèle aux lames, la longueur d'onde guidée à travers le prisme est supérieure à la longueur d'onde en espace libre. On obtient ainsi un déphasage dépendant de la longueur de prisme traversée. Ainsi, en première approximation, seul le faisceau dont la polarisation est parallèle aux lames du prisme est dévié, plus particulièrement son plan équiphase est incliné.FIG. 5 illustrates the effect of the prism 41. The latter performs a selective beam deflection as a function of the polarization of the beam. The two sources Si, S 2 are chosen with crossed polarizations. The beam 2 coming from the first source Si has a polarization perpendicular to the blades 42 of the prism, while beam 21 coming from the second source S 2 has a polarization parallel to the blades 42. To simplify the presentation, these two beams are presented as attacking both the prism 41 perpendicularly. The beam 2 of the first source Si is not deflected and the beam 21 of the second source S 2 is deflected. When the polarization, that is to say that the electric field, is perpendicular to the plates, the wavelength guided through the prism is in fact little modified compared to the wavelength in free space. On the other hand, when the polarization is parallel to the plates, the wavelength guided through the prism is greater than the wavelength in free space. A phase shift is thus obtained depending on the length of the prism passed through. Thus, as a first approximation, only the beam whose polarization is parallel to the blades of the prism is deflected, more particularly its equiphase plane is inclined.
Comme l'illustre la figure 6, dans une configuration de sources S-i, S2 telle que présentée par la figure 3, le prisme 41 permet donc de réduire l'angle A2 entre les deux faisceaux 2, 21 en sortie d'antenne, l'angle Ai restant le même. La sortie est non plus la sortie de lentille mais la sortie du prisme qui lui est associé. Le faisceau 2 issu de la première source Si n'est en première approximation pas dévié par le prisme. Par rapport à un fonctionnement sans prisme, la déviation de faisceau, d'angle A2, provoquée par le décalage d de la deuxième source S2 est diminuée grâce au prisme. En d'autres termes, l'angle B2 entre les faisceaux avec prisme est inférieur à l'angle A2 sans prisme. Ainsi, pour une déviation de faisceau d'angle B2 recherchée, l'adjonction du prisme 41 permet donc d'augmenter le décalage d entre les deux sources S^ S2 et rend possible l'implantation de deux sources juxtaposées d'encombrement non négligeable sans superposition de celles-ci.As illustrated in FIG. 6, in a configuration of sources Si, S 2 as presented by FIG. 3, the prism 41 therefore makes it possible to reduce the angle A 2 between the two beams 2, 21 at the antenna output, the angle Ai remaining the same. The output is no longer the lens output but the output of the prism associated with it. The beam 2 from the first source Si is not at first approximation deflected by the prism. Compared to an operation without a prism, the beam deflection, of angle A 2 , caused by the offset d of the second source S 2 is reduced thanks to the prism. In other words, the angle B 2 between the beams with prism is less than the angle A 2 without prism. Thus, for a desired beam deflection of angle B 2 , the addition of the prism 41 therefore makes it possible to increase the offset d between the two sources S ^ S 2 and makes it possible to install two juxtaposed sources of non-congested dimensions. negligible without superposition of these.
La figure 7 illustre un autre mode de réalisation possible d'une antenne selon l'invention qui permet de corriger les aberrations dues à la défocalisation de la deuxième source S2. En l'absence d'aberration, l'onde émise en sortie du prisme est plane, c'est-à-dire équiphase sur un plan. Le décalage d de la deuxième source S2 par rapport au foyer fait que l'onde émise correspondante n'est plus tout à fait plane, ce qui a notamment pour conséquence d'augmenter le niveau des lobes secondaires de l'antenne. Pour corriger ces aberrations, le profil du prisme est modifié par rapport à celui des figures précédentes. Le profil de sortie 71 du prisme n'est plus une droite comme représentée en pointillés mais présente une courbe par exemple symétrique par rapport à un point P. Ce point P est situé sur le profil de sortie, sensiblement à l'intersection avec l'axe focal 3 de la lentille 1. Le demi-profil qui est du même côté que la deuxième source S2 par rapport à l'axe focale 3 présente une forme concave alors que l'autre demi-profil présente une forme convexe.FIG. 7 illustrates another possible embodiment of an antenna according to the invention which makes it possible to correct the aberrations due to the defocusing of the second source S 2 . In the absence of aberration, the wave emitted at the output of the prism is plane, that is to say equiphase on a plane. The offset d of the second source S 2 with respect to the focus means that the corresponding transmitted wave is no longer entirely flat, which has the particular effect of increasing the level of the secondary lobes of the antenna. To correct these aberrations, the profile of the prism is modified compared to that of the previous figures. The output profile 71 of the prism is no longer a straight line as shown in dotted lines but has a curve for example symmetrical with respect to a point P. This point P is located on the output profile, substantially at the intersection with the focal axis 3 of the lens 1. The half-profile which is on the same side as the second source S 2 with respect to the focal axis 3 has a concave shape while the other half-profile has a convex shape.
Les figures 8a et 8b présentent un mode de réalisation possible de l'ensemble constitué de la lentille 1 et du prisme 41. Dans ce mode de réalisation, la lentille et le prisme sont réalisés dans un même bloc diélectrique. La figure 8a représente une vue de profil de la pièce unique 1 , 41 et la figure 8b représente une vue de face, suivant F, de cette dernière. Dans un premier mode de réalisation possible, les lames 42 du prisme sont par exemple moulées dans le bloc diélectrique. La constante diélectrique ειa des lames, supérieure à la constante diélectrique o de l'air compris dans l'espace libre 81 entre les lames, suffit à assurer la fonction de prisme filtre de polarisation, du moins à assurer une diminution de l'angle A2. Les parois des lames ne sont donc pas nécessairement recouvertes d'une couche métallique. Etant donné que la lentille et le prisme ne forment qu'un seul bloc, la constante diélectrique ειa des lames est par exemple aussi la constante diélectrique de la lentille.Figures 8a and 8b show a possible embodiment of the assembly consisting of the lens 1 and the prism 41. In this embodiment, the lens and the prism are produced in the same dielectric block. FIG. 8a represents a profile view of the single part 1, 41 and FIG. 8b represents a front view, along F, of the latter. In a first possible embodiment, the blades 42 of the prism are for example molded in the dielectric block. The dielectric constant ει has blades, greater than the dielectric constant o of the air included in the free space 81 between the blades, is sufficient to ensure the function of polarization filter prism, at least to ensure a reduction in the angle A 2 . The walls of the blades are therefore not necessarily covered with a metallic layer. Since the lens and the prism form a single block, the dielectric constant ει to the blades is for example also the dielectric constant of the lens.
Dans un deuxième mode de réalisation possible, les lames 42 sont par exemple en métal et sont noyées dans le bloc diélectrique. Dans ce cas, c'est l'espace 81 entre les lames qui comporte par exemple la même constante diélectrique que la lentille.In a second possible embodiment, the blades 42 are for example made of metal and are embedded in the dielectric block. In this case, it is the space 81 between the blades which comprises for example the same dielectric constant as the lens.
Les figures 9a et 9b présentent deux autres exemples de réalisation où le prisme 41 et le radôme 91 de l'antenne ne forme qu'une seule pièce. Dans ces modes de réalisation, le radôme 91 , par exemple plan, est moulé avec le prisme 41 dans un même matériau diélectrique ou collé sur le prisme. Le profil de compensation 71 est par exemple ici en regard de la lentille 1. Dans le cas d'une lentille à face convexe et à face plane, cette dernière peut être face au prisme comme le montre la figure 9a ou à l'opposé comme l'illustre la figure 9b. Les lames 42 du prisme peuvent être moulées dans le matériau diélectrique ou en métal comme dans le cas des figures 8a et 8b précédentes.Figures 9a and 9b show two other exemplary embodiments where the prism 41 and the radome 91 of the antenna forms only one piece. In these embodiments, the radome 91, for example planar, is molded with the prism 41 in the same dielectric material or bonded on the prism. The compensation profile 71 is for example here opposite the lens 1. In the case of a lens with a convex face and a flat face, the latter may face the prism as shown in FIG. 9a or on the opposite side as illustrated in Figure 9b. The blades 42 of the prism can be molded in the dielectric material or in metal as in the case of FIGS. 8a and 8b above.
La figure 6 montre un exemple de réalisation où la deuxième source S2 est située dans le plan perpendiculaire à l'axe optique contenant le foyer. L'invention reste néanmoins valable si cette deuxième source S2 est placée en dehors de ce plan. Il en est de même si la première source Si n'est pas exactement placée au foyer de la lentille. Cet écart de position peut alors être compensé en jouant sur le profil 71 de la lentille. Avantageusement, la première source Si ne nécessite donc pas d'être placée exactement au foyer de la lentille. Cela permet notamment une mise en œuvre simple de l'invention.FIG. 6 shows an exemplary embodiment where the second source S 2 is located in the plane perpendicular to the optical axis containing the focal point. The invention nevertheless remains valid if this second source S 2 is placed outside this plane. It is the same if the first source Si is not exactly placed at the focal point of the lens. This difference in position can then be compensated for by playing on the profile 71 of the lens. Advantageously, the first source Si therefore does not need to be placed exactly at the focal point of the lens. This allows in particular a simple implementation of the invention.
La lentille hyperfréquence 1 décrite précédemment, notamment aux figures 2a, 2b et 2c, est une lentille diélectrique. L'utilisation d'une lentille métallique ou en matériau diélectrique métallisé constituée d'un réseau de guides d'onde à double polarisation est également possible. La lentille se présente alors sous la forme d'une grille d'épaisseur non constante dont les trous constituent les guides de transmission. Dans ce cas, l'effet de focalisation de la lentille utilise la différence entre longueur d'onde guidée dans le réseau de guides et longueur d'onde en espace libre. The microwave lens 1 described above, in particular in FIGS. 2a, 2b and 2c, is a dielectric lens. The use of a metallic lens or of a metallized dielectric material made up of an array of double polarization waveguides is also possible. The lens is then in the form of a grid of non-constant thickness, the holes of which constitute the transmission guides. In this case, the focusing effect of the lens uses the difference between the wavelength guided in the array of guides and the wavelength in free space.

Claims

REVENDICATIONS
1. Antenne bi-faisceaux à deux sources comportant une lentille hyperfréquence (1), caractérisée en ce qu'une première source Si étant située au voisinage du foyer de la lentille et la deuxième source S2 étant située à une distance d de la première source, au voisinage du plan (31) perpendiculaire à l'axe focal de la lentille (3), elle comporte un prisme filtre de polarisation (41) situé du côté de la lentille opposé aux sources, les deux sources ayant des polarisations croisées et la première source Si ayant une polarisation sensiblement perpendiculaire aux lames du prisme (41).1. Two-beam two-beam antenna comprising a microwave lens (1), characterized in that a first source Si being located in the vicinity of the focal point of the lens and the second source S 2 being located at a distance d from the first source, in the vicinity of the plane (31) perpendicular to the focal axis of the lens (3), it comprises a polarization filter prism (41) located on the side of the lens opposite to the sources, the two sources having crossed polarizations and the first source Si having a polarization substantially perpendicular to the blades of the prism (41).
2. Antenne selon la revendication 1 , caractérisée en ce que le profil de sortie (71) du prisme présente une courbe avec une partie convexe et une partie concave pour compenser la défocalisation des sources Si, S2.2. Antenna according to claim 1, characterized in that the output profile (71) of the prism has a curve with a convex part and a concave part to compensate for the defocusing of the sources Si, S 2 .
3. Antenne selon la revendication 2, caractérisée en ce que la courbe est symétrique par rapport à un point P situé sensiblement sur l'axe focal (3) de la lentille.3. Antenna according to claim 2, characterized in that the curve is symmetrical with respect to a point P located substantially on the focal axis (3) of the lens.
4. Antenne selon l'une quelconque des revendications précédentes, caractérisée en ce que la lentille (1) et le prisme (41) sont réalisés dans un même bloc diélectrique.4. An antenna according to any one of the preceding claims, characterized in that the lens (1) and the prism (41) are produced in the same dielectric block.
5. Antenne selon la revendication 4, caractérisée en ce que les lames (42) du prisme sont moulées dans le bloc diélectrique.5. Antenna according to claim 4, characterized in that the blades (42) of the prism are molded in the dielectric block.
6. Antenne selon la revendication 5, caractérisée en ce que les parois des lames (42) sont recouvertes d'une couche métallique.6. Antenna according to claim 5, characterized in that the walls of the blades (42) are covered with a metallic layer.
7. Antenne selon la revendication 4, caractérisée en ce que les lames (42) sont en métal et sont noyées dans le bloc diélectrique.7. Antenna according to claim 4, characterized in that the blades (42) are made of metal and are embedded in the dielectric block.
8. Antenne selon l'une quelconque des revendications précédentes, caractérisée en ce que le prisme (41) et le radôme (91) de l'antenne ne forment qu'une seule pièce. 8. Antenna according to any one of the preceding claims, characterized in that the prism (41) and the radome (91) of the antenna form only one piece.
9. Antenne selon la revendication 8, caractérisée en ce que le prisme et le radôme sont moulés dans un même matériau diélectrique.9. Antenna according to claim 8, characterized in that the prism and the radome are molded from the same dielectric material.
10. Antenne selon la revendication 8, caractérisé en ce que le radôme est collé sur le prisme. 10. Antenna according to claim 8, characterized in that the radome is stuck on the prism.
EP01984045A 2000-06-23 2001-06-22 Double-beam antenna with two sources Withdrawn EP1330853A1 (en)

Applications Claiming Priority (3)

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FR0008091 2000-06-23
FR0008091A FR2810799A1 (en) 2000-06-23 2000-06-23 Double beam radar antenna includes two adjacent sources with microwave lens and polarisation filter
PCT/FR2001/001984 WO2001099229A1 (en) 2000-06-23 2001-06-22 Double-beam antenna with two sources

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GB0313573D0 (en) 2003-06-12 2003-07-16 Qinetiq Ltd Radiation detection apparatus
DE102005033414A1 (en) * 2005-07-18 2007-01-25 Robert Bosch Gmbh antenna means

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GB705209A (en) * 1951-09-07 1954-03-10 Marconi Wireless Telegraph Co Improvements in or relating to ultra short wave radio communication and radar systems
FR2092860B1 (en) * 1970-06-25 1976-09-03 Labo Cent Telecommunicat
FR2450508A1 (en) * 1979-03-02 1980-09-26 Thomson Csf PARALLEL BLADE REFLECTOR FOR MICROWAVE ANTENNAS AND METHOD FOR MANUFACTURING SUCH A REFLECTOR
US5121129A (en) * 1990-03-14 1992-06-09 Space Systems/Loral, Inc. EHF omnidirectional antenna

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