EP0109322A1 - Doppelreflektorantenne für einen Nachführungsradar mit verbesserter Zielauffassung - Google Patents

Doppelreflektorantenne für einen Nachführungsradar mit verbesserter Zielauffassung Download PDF

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Publication number
EP0109322A1
EP0109322A1 EP83402077A EP83402077A EP0109322A1 EP 0109322 A1 EP0109322 A1 EP 0109322A1 EP 83402077 A EP83402077 A EP 83402077A EP 83402077 A EP83402077 A EP 83402077A EP 0109322 A1 EP0109322 A1 EP 0109322A1
Authority
EP
European Patent Office
Prior art keywords
reflector
waves
plane
antenna
main reflector
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Withdrawn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
EP83402077A
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English (en)
French (fr)
Inventor
Jean Bouko
François Salvat
Claude Coquio
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
Thomson CSF 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 Thomson CSF SA filed Critical Thomson CSF SA
Publication of EP0109322A1 publication Critical patent/EP0109322A1/de
Withdrawn legal-status Critical Current

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    • 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
    • H01Q19/18—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 having two or more spaced reflecting surfaces
    • H01Q19/19—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 having two or more spaced reflecting surfaces comprising one main concave reflecting surface associated with an auxiliary reflecting surface
    • H01Q19/195—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 having two or more spaced reflecting surfaces comprising one main concave reflecting surface associated with an auxiliary reflecting surface wherein a reflecting surface acts also as a polarisation filter or a polarising device
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H01Q25/002—Antennas or antenna systems providing at least two radiating patterns providing at least two patterns of different beamwidth; Variable beamwidth antennas

Definitions

  • the present invention relates to antennas with double reflector for tracking radar making it possible to improve acquisition, and more particularly to antennas of the Cassegrain type of large dimensions.
  • large antennas antennas having a diameter greater than 70 ⁇ , ⁇ being the working wavelength.
  • a Cassegrain type antenna conventionally comprises a concave main reflector of generally parabolic shape, a convex auxiliary reflector, of generally hyperbolic shape, and a microwave source, these elements being placed in relation to each other so that the auxiliary reflector returns towards the reflector main the radiation emitted by the source.
  • This type of antenna is particularly suitable for equipping tracking radars because it has the characteristics necessary for this. Indeed, Cassegrain type antennas with large dimensions have a narrow beam of radiation, that is to say a small opening angle.
  • a first solution consists in widening the beam by defocusing either of the primary source or of the auxiliary reflector in the case of the antenna with double reflector.
  • the focal point of the paraboloid no longer coincides with the phase center of the source, the distribution of fields (electric and magnetic) on the opening of the reflector is no longer equiphase.
  • the opening is no longer equiphase the beams which are reflected are no longer parallel to the axis of symmetry of the reflector, which causes a widening of the beam. This is achieved at the expense of gain and efficiency of the antenna, as defocusing is always accompanied by a loss of energy.
  • the auxiliary reflector is defocused on the axis of symmetry of the main reflector, the result obtained is identical, the beam is widened at the expense of the gain of the antenna .
  • a second solution consists in modifying the phase law of the radiation effectively under the control of a computer to avoid loss of yield, but this solution only applies to antennas with electronic scanning, or these antennas are of a very high cost.
  • the two solutions presented also have the drawback of not being able to obtain a beam widening greater than two or three times the width at half power given by the radiation diagram in normal operation, without deformation of this diagram.
  • a third solution consists in using a second antenna, smaller than the main antenna, and having the characteristics necessary for the acquisition of targets.
  • This third solution has the drawback of increasing the size and the weight which the radar turret must support.
  • technological problems due to the parallax between the two antennas must be taken into account, which complicates operation.
  • the invention provides a tracking antenna of the Cassegrain type, making it possible to have a sufficiently wide beam to acquire targets in a first phase, and making it possible to have a sufficiently narrow beam to allow the pursuit of these targets with great precision.
  • the subject of the invention is therefore a double reflector antenna for tracking radar making it possible to improve the acquisition, comprising a main reflector, an auxiliary reflector of dimensions much smaller than the dimensions of the main reflector, a source emitting spherical electromagnetic waves at rectilinear crossed polarizations, one of the focal points of the secondary reflector being merged with the focal point of the main reflector, the other focal point being located in the phase center of the source, so that the auxiliary reflector returns the radiation emitted by the the source, mainly characterized in that the auxiliary reflector is semi-transparent, thus making it possible to allow certain waves to pass and to reflect the others, and in that an optical element, of suitable dimensions to intercept the waves passing through the auxiliary reflector, makes it possible to transform these waves into plane waves, to obtain an equiphase plane in the equipha plane from the antenna and obtain a wider beam by focusing these waves.
  • the antenna for tracking radar represented in FIG. 1 comprises a primary source 1 which radiates spherical electromagnetic waves with crossed rectilinear polarizations. It therefore emits waves in two orthogonal polarizations.
  • This source is generally, and in particular in the case of Cassegrain antennas, an electromagnetic horn whose dimensions are appropriate for correctly lighting the auxiliary reflector.
  • a Cassegrain antenna also includes, in a manner known in itself, a main reflector 2 of parabolic shape which has for focus a point F1 located on its axis of symmetry Oz, 0 being the top of the paraboloid.
  • the source 1 can be placed either upstream of the vertex 0 of the main reflector, either at this vertex 0, or inside the reflector on the axis Oz. In this figure, the source 1 is placed inside.
  • the Cassegrain antenna also includes an auxiliary reflector 3 of hyperbolic shape, of dimensions much smaller than the dimensions of the main reflector 2 and which has for point point F1 and point F2 phase center of the source 1.
  • any radius F2 N is reflected by the hyperboloid in a direction NR seeming to emanate from F1.
  • Fl is the focal point of the paraboloid 2
  • the radius RQ reflected by the latter is parallel to Oz.
  • the reflected waves are plane waves in phase in the plane of the opening.
  • the auxiliary reflector 3 is semi-transparent. It is transparent for rectilinear polarization of the emitted wave and for cross polarization with this wave, it behaves like a conventional reflector.
  • This reflector 3 is constituted by a set of wires which are parallel to each other. It allows, depending on the position of the wires with respect to this polarization, to let through the waves whose polarization is perpendicular to the wires.
  • the auxiliary reflector 3 must have wires in planes parallel to the polarization of vertical incident waves to reflect these waves in order to illuminate the main reflector.
  • the reflector will however be transparent to horizontally polarized waves.
  • the antenna also comprises downstream of the auxiliary reflector 3 an optical element 5 of the electromagnetic lens type, making it possible to focus the waves passing through the reflector 3 at infinity.
  • the dimensions of this element are suitable for intercepting the radiation passing through this reflector 3 and to obtain an equiphase plane coincident with the plane P.
  • the diameter d being much less than D, if d is about ten times smaller than D, the opening ⁇ 2 is ten times wider than ⁇ 1.
  • Figure 2 shows an alternative embodiment
  • the source 1 is placed upstream of the main reflector 2 on the axis Oz, which allows for example to operate the antenna in scanning.
  • the optical element 5 can then be placed at the apex 0 of the reflector 2.
  • the distance 1 between the apex 0 and the fover F1 is limited and must not overwrite the Rayleigh area. Under these conditions the waves focused by the element 5 remain focused near the secondary reflector
  • FIG. 3 shows a partial diagram relating to a first embodiment of the optical element 5.
  • This embodiment is suitable for an antenna having a wide passband.
  • the element optical 5 is constituted by a convex planar electromagnetic lens of hyperbolic shape, of focal point F2 and of refractive index greater than one, this is the case of a dielectric. This type of lens allows you to work in a wide range of frequencies.
  • the planar section of the lens is therefore in the P plane and the refractive index is chosen so that the waves are in phase in this plane.
  • the hyperbolic surface of the lens therefore merges with that of the reflector 3.
  • the polarization rotator 5 consists, for example, of a set of grids, three generally, whose orientation of the wires is 45 ° relative to the electric field vector E of the polarization of the wave focused by the lens 5 .
  • FIG. 4 shows a partial diagram relating to a second embodiment.
  • the convex plane lens 5 is an ellipsoid with a focal point F2 and a refractive index of less than one, this is the case with metallic lenses.
  • This structure generally reduces the bandwidth of the antenna, it is more particularly suitable for applications which do not require a large bandwidth.
  • the antenna with double reflector makes it possible to obtain both a narrow beam and a wide beam since certain emitted waves having a given rectilinear polarization are reflected successively on the auxiliary reflector 3 then on the main reflector 2, while the waves having a cross polarization pass through the second reflector 3.
  • the widening of the beam is all the greater the smaller the diameter of the lens compared to the diameter of the main reflector .

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  • Aerials With Secondary Devices (AREA)
EP83402077A 1982-11-05 1983-10-25 Doppelreflektorantenne für einen Nachführungsradar mit verbesserter Zielauffassung Withdrawn EP0109322A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8218597A FR2535906B1 (fr) 1982-11-05 1982-11-05 Antenne a double reflecteur pour radar de poursuite permettant d'ameliorer l'acquisition
FR8218597 1982-11-05

Publications (1)

Publication Number Publication Date
EP0109322A1 true EP0109322A1 (de) 1984-05-23

Family

ID=9278940

Family Applications (1)

Application Number Title Priority Date Filing Date
EP83402077A Withdrawn EP0109322A1 (de) 1982-11-05 1983-10-25 Doppelreflektorantenne für einen Nachführungsradar mit verbesserter Zielauffassung

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Country Link
EP (1) EP0109322A1 (de)
FR (1) FR2535906B1 (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2234858A (en) * 1988-09-02 1991-02-13 Thorn Emi Electronics Ltd Cassegrain antenna
EP0446610A1 (de) * 1990-03-07 1991-09-18 Hughes Aircraft Company Vergrösserte phasengesteuerte Gruppenantenne mit digitalem Strahlformungsnetzwerk
CN101738715B (zh) * 2009-12-25 2011-06-15 中国科学院武汉物理与数学研究所 高焦比集光器
CN106785426A (zh) * 2016-07-26 2017-05-31 深圳市鼎耀科技有限公司 宽波束毫米波圆极化天线

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3049708A (en) * 1959-11-20 1962-08-14 Sperry Rand Corp Polarization sensitive antenna system
FR1477571A (fr) * 1966-02-25 1967-04-21 Csf Perfectionnements aux antennes à dispositif de focalisation
GB1107378A (en) * 1964-06-26 1968-03-27 Marconi Co Ltd Improvements in or relating to self-orienting directional radio receivers
US4220957A (en) * 1979-06-01 1980-09-02 General Electric Company Dual frequency horn antenna system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3049708A (en) * 1959-11-20 1962-08-14 Sperry Rand Corp Polarization sensitive antenna system
GB1107378A (en) * 1964-06-26 1968-03-27 Marconi Co Ltd Improvements in or relating to self-orienting directional radio receivers
FR1477571A (fr) * 1966-02-25 1967-04-21 Csf Perfectionnements aux antennes à dispositif de focalisation
US4220957A (en) * 1979-06-01 1980-09-02 General Electric Company Dual frequency horn antenna system

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2234858A (en) * 1988-09-02 1991-02-13 Thorn Emi Electronics Ltd Cassegrain antenna
FR2661562A1 (fr) * 1988-09-02 1991-10-31 Thorn Emi Electronics Ltd Antenne cassegrain.
EP0446610A1 (de) * 1990-03-07 1991-09-18 Hughes Aircraft Company Vergrösserte phasengesteuerte Gruppenantenne mit digitalem Strahlformungsnetzwerk
CN101738715B (zh) * 2009-12-25 2011-06-15 中国科学院武汉物理与数学研究所 高焦比集光器
CN106785426A (zh) * 2016-07-26 2017-05-31 深圳市鼎耀科技有限公司 宽波束毫米波圆极化天线
CN106785426B (zh) * 2016-07-26 2024-01-30 深圳市鼎耀科技有限公司 宽波束毫米波圆极化天线

Also Published As

Publication number Publication date
FR2535906A1 (fr) 1984-05-11
FR2535906B1 (fr) 1985-09-20

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Inventor name: SALVAT, FRANCOIS

Inventor name: BOUKO, JEAN