JP2014138281A - Polarizer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polarizer in which the monostatic radar reflection cross-sectional area of the beam scanning surface of an antenna is reduced.SOLUTION: A polarizer includes a radome 101 consisting of a plane obliquely crossing a normal (z axis) orthogonal to the beam scanning surface of an antenna while facing the radiation direction thereof, and formed from a dielectric, and a wire grid 102 consisting of a conductor formed on the surface of the radome 101. The wire grid 102 consists of a plurality of conductors arranged at a predetermined interval.

Description

  The present invention relates to a polarizer that is arranged around an antenna and changes the inclination of the polarization plane of an electromagnetic wave.

  A polarizer in which a wire grid is formed on a flat plate or cylindrical dielectric radome is known (for example, see Patent Document 1).

  Patent Document 1 describes a polarizer that can minimize the difference in polarization loss between horizontal polarization and vertical polarization within a necessary horizontal plane angle range. In the polarizer of Patent Document 1, the inclination of the wire grid on the surface arranged farthest from the antenna element with respect to the polarization plane of the electromagnetic wave radiated from the antenna element is expressed as a horizontal plane angle ψ (°) from the front of the antenna element. The slope is such that the difference between the polarization losses of horizontal and vertical polarization within the range is the smallest.

  An antenna is provided on the back of the polarizer. The polarization plane of the electromagnetic wave passing through the polarizer is the main polarization in the direction orthogonal to the extension direction of the wire grid, and the cross polarization is in the direction along the extension direction of the wire grid.

  Patent Document 2 describes a radome with a built-in electric wiring that prevents the antenna from rotating and does not affect the radio wave characteristics by connecting the electric devices before and after the radome or above and below the radome. Yes. The radome with built-in electric wiring in Patent Document 2 uses a radio wave polarization conductor (polarizer grid) inside the radome main body as connection wiring when the electric devices before and after the radome main body or the upper and lower electric devices are connected to each other. In addition, the wiring is connected to an electrical device via a connector. In the radome with built-in electric wiring of Patent Document 2, a cylindrical polarizer is used.

Japanese Patent Laid-Open No. 6-37538 Japanese Patent Laid-Open No. 7-15224

  When an antenna including the above-described polarizer is considered as a receiving antenna, the cross polarization in the polarizer of the incoming radio wave is almost totally reflected. As in Patent Document 1 or 2, in a flat plate or cylindrical polarizer that is orthogonal to the beam scanning plane of a radar, the cross polarization of the incoming radio wave is reflected in the same direction as the arrival direction of the radio wave. Therefore, there is a problem that the monostatic radar reflection cross section (monostatic RCS) with respect to the polarized wave is large and is easily detected by other radar devices.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a polarizer that reduces a monostatic radar reflection cross-sectional area of a beam scanning surface of an antenna.

  In order to achieve the above object, a polarizer according to an aspect of the present invention is formed of a dielectric that is opposed to a radiation direction of an antenna, is inclined with respect to a perpendicular perpendicular to the beam scanning plane of the antenna, and intersects the perpendicular. And a plurality of conducting wires made of conductors formed on the surface of the radome.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizer which reduces the monostatic radar reflective cross section of the beam scanning surface of an antenna can be obtained.

It is a perspective view which shows typically the polarizer which concerns on Embodiment 1 of this invention. It is a side surface expanded view which shows typically the polarizer which concerns on Embodiment 2 of this invention. It is a side surface expanded view which shows typically the radome layer of the polarizer which concerns on Embodiment 3 of this invention. FIG. 9 is a perspective view schematically showing a polarizer according to a third embodiment. It is a perspective view which shows typically the polarizer which concerns on Embodiment 4 of this invention. It is a perspective view which shows typically the polarizer which concerns on Embodiment 5 of this invention.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or equivalent part in a figure.

Embodiment 1 FIG.
1 is a perspective view schematically showing a polarizer according to Embodiment 1 of the present invention. The polarizer 100 includes a conical radome 101 and a wire grid 102 formed on the surface of the radome 101. The radome 101 is formed of a frustoconical dielectric. The wire grid 102 is composed of a plurality of conductors made of conductors arranged at a predetermined interval. An antenna (not shown) is disposed in the internal space of the radome 101. The radome 101 is opposed to the antenna radiation direction.

  The central axis of the truncated cone of the radome 101 is defined as the z axis, and the upper and lower planes of the truncated cone perpendicular to the central axis are defined as the xy plane. Usually, the beam scanning plane of the antenna is an xy plane. In the embodiment, it is assumed that the beam scanning plane of the antenna is horizontally arranged and the center axis (z axis) of the truncated cone of the radome 101 is installed in the vertical direction. The description will be made on the assumption that the radome 101 is installed such that the smaller diameter surface is vertically upward of the upper and lower bases.

  The surface of the radome 101 on which the wire grid 102 is formed is inclined with respect to the perpendicular direction perpendicular to the z-axis direction, that is, the beam scanning surface of the antenna, and intersects the perpendicular line. Each conducting wire of the wire grid 102 is continuous from the upper bottom to the lower bottom of the radome 101, and is inclined with respect to the generatrix of the truncated cone. As for the plane of polarization of the electromagnetic wave passing through the polarizer 100, the direction orthogonal to the extension direction of the wire grid 102 is the main polarization, and the direction along the extension direction of the wire grid 102 is the cross polarization.

  Among the radio waves arriving from the horizontal plane (xy plane), the component corresponding to the cross polarization of the polarizer 100 is almost totally reflected on the surface of the circular truncated cone-shaped polarizer 100. At this time, since the surface of the polarizer 100 is inclined with respect to the vertical line, the reflected wave is reflected obliquely upward and does not return in the horizontal direction. Therefore, the monostatic radar reflection cross section (monostatic RCS) in the horizontal plane can be reduced.

  Among the radio waves arriving from the horizontal plane, a component corresponding to the main polarization of the polarizer 100 passes through the polarizer 100 and is received by an antenna provided therein. Since most of the energy that has passed through the polarizer 100 is consumed at the feed point of the internal antenna, the RCS for the main polarization is originally small.

  The surface of the polarizer 100 is not limited to the side surface of the truncated cone. The surface of the polarizer should just be comprised from the surface which inclines with respect to the perpendicular orthogonal to the beam scanning surface of an antenna, and cross | intersects a perpendicular.

  As described above, the polarizer 100 according to the first embodiment is composed of the plane that is inclined with respect to the perpendicular perpendicular to the beam scanning plane of the antenna and intersects the perpendicular. The area can be reduced.

Embodiment 2. FIG.
FIG. 2 is a side development view schematically showing a polarizer according to Embodiment 2 of the present invention. FIG. 2 shows a part of a development view of the polarizer 100. The same components as those described above are denoted by the same reference numerals and description thereof is omitted.

  The side surface 103 of the polarizer is divided at equal intervals by a dividing line 104 in the circumferential direction of the truncated cone of the radome 101. The dividing line 104 is along the generatrix of the truncated cone. The side surface 103 is further divided into a plurality of stages by divided arcs 105 at unequal intervals in the generatrix direction. By the dividing line 104 and the dividing arc 105, the side surface 103 of the polarizer is divided into a plurality of roughly trapezoidal regions.

  The conducting wires of the wire grid 102 are formed in a straight line so as to connect the diagonals of the roughly trapezoidal region divided by the dividing line 104 and the dividing arc 105. The conductors of the two roughly trapezoidal regions located on the diagonal are connected to each other at the vertex (intersection of the dividing line 104 and the dividing arc 105) where the two regions located on the diagonal contact. Each conducting wire of the wire grid 102 is continuously connected so as to draw a broken line from one edge of the side surface of the truncated cone to the other edge. In the actual polarizer 100, the left and right radial sides of the sector of FIG. 2 are connected to form a truncated cone, and the conducting wire is continuous at the connected sides.

  If the approximate trapezoidal area divided by the dividing line 104 and the dividing arc 105 is made sufficiently fine compared to the wavelength of the frequency for which the polarizer 100 is used, it will be connected almost smoothly to that frequency. appear. Thereby, the inclination of the polarization plane of the electromagnetic wave passing through the polarizer 100 can be made piecewise constant.

  Furthermore, the respective conductors of the wire grid 102 may be formed so as to be inclined at a constant inclination angle θ with respect to the arc on the upper surface side of the divided substantially trapezoidal region.

Embodiment 3 FIG.
In Embodiment 3, a plurality of polarizer layers are stacked to form one polarizer. FIG. 3 is a side development view schematically showing a polarizer layer according to Embodiment 3 of the present invention. FIG. 3 shows a part of a development view of the polarizer layer 116. As in FIG. 2, the side surfaces 113 of the polarizer layer 116 are divided at equal intervals by dividing lines 114 in the circumferential direction of the truncated cone of the radome layer 111. The dividing line 114 is along the generatrix of the truncated cone. The side surface 113 is further divided into a plurality of stages by divided arcs 115 at unequal intervals in the bus line direction. The side surface 113 of the polarizer is divided into a plurality of roughly trapezoidal regions by the dividing line 114 and the dividing arc 115.

  The conducting wires of the wire grid 112 are formed in a straight line so as to connect the diagonals of the roughly trapezoidal region divided by the dividing line 114 and the dividing arc 115. The conductors of the two approximately trapezoidal regions located on the diagonal are connected to each other at the vertex (intersection of the dividing line 114 and the dividing arc 115) where the two regions located on the diagonal contact. Each conducting wire of the wire grid 112 is continuously connected so as to draw a broken line from one edge of the side surface of the truncated cone to the other edge.

  When the divided arc 115 is made narrower (or wider) so that the divided arc 115 is different from the divided arc 105 of FIG. 2, the inclination angle θ ′ of the wire grid 112 conducting wire also becomes different from the inclination angle θ of FIG. Although the dividing line 114 in FIG. 3 is drawn to be the same as the dividing line 104 in FIG. 2, it may be different (the central angle is made smaller or larger).

  If the polarizer 100 of FIG. 2 and the polarizer layer 116 of FIG. 3 are independent layers, and each layer is laminated at a predetermined interval to form a new polarizer 110, the direction of the polarization plane of the electromagnetic wave passing through the polarizer 110 gradually increases. Can be changed.

  FIG. 4 is a perspective view schematically showing a polarizer according to the third embodiment. FIG. 4 shows a state in which the polarizer 110 is configured by laminating the polarizer 100 and the polarizer layer 116.

  For example, if a polarizer layer with θ ′ = 22.5 degrees and θ = 45 degrees is sequentially arranged around an antenna of vertical polarization (polarization plane is 0 degree), the direction of the polarization plane of the electromagnetic wave is 0. The angle can be gradually changed from 45 degrees to 45 degrees, and polarization conversion can be smoothly performed by suppressing the discontinuity of rotation of the polarization plane to a low level. Also in the third embodiment, the surface of each polarizer layer is composed of a surface that is inclined with respect to the perpendicular perpendicular to the beam scanning plane of the antenna and intersects the perpendicular, so that the reflected wave of each polarizer layer is reflected obliquely upward. However, it does not return in the horizontal direction. Therefore, the monostatic radar reflection cross section (monostatic RCS) in the horizontal plane can be reduced.

Embodiment 4 FIG.
FIG. 5 is a perspective view schematically showing a polarizer according to Embodiment 4 of the present invention. In FIG. 5, the polarizer 120 has a shape in which a truncated cone is divided by a plane parallel to the central axis (perpendicular perpendicular to the beam scanning plane of the antenna).

  The polarizer 120 includes a radome 121 and a wire grid 122 formed on the surface of the radome 121. The radome 121 is formed of a dielectric having a shape in which a truncated cone is divided. The wire grid 122 is composed of a plurality of conducting wires made of conductors arranged at equal intervals. An antenna (not shown) is disposed in the internal space of the radome 121. Usually, the beam scanning plane of the antenna is an xy plane.

  In the first to third embodiments, the antenna included therein is considered to be omnidirectional (or all-round beam scanning), but the antenna is not limited to omnidirectional but is unidirectional (or limited angle beam scanning). It may be. At this time, the polarizer 120 is not required except for the direction of the antenna, so that it does not necessarily have a circular shape when viewed in the cross-section of the xy plane, even if a part is missing as shown in FIG. Good.

  FIG. 5 shows an example in which the truncated cone is divided in half by a plane passing through the central axis, that is, the internal angle of the cross section of the xy plane is 180 °. The internal angle of the cross section of the radome 121 is not necessarily 180 °, and the truncated cone may be divided so as to be an acute angle or an obtuse angle.

  The polarizer 120 according to the fourth embodiment is also configured from a surface that is inclined with respect to the perpendicular perpendicular to the beam scanning plane of the antenna and intersects the perpendicular, so that the reflected wave of the polarizer 120 is reflected obliquely upward and horizontally. Will not return. Therefore, the monostatic radar reflection cross section (monostatic RCS) in the horizontal plane can be reduced.

Embodiment 5 FIG.
FIG. 6 is a perspective view schematically showing a polarizer according to Embodiment 5 of the present invention. In the fifth embodiment, a conductor plate is provided in contact with a plane parallel to the perpendicular dividing the truncated cone of the polarizer of the fourth embodiment. As shown in FIG. 6, a metal plate 200 is provided on the surface of the polarizer 120 of the fourth embodiment, which is obtained by dividing the truncated cone.

  By installing the metal plate 200 at a location other than the directional direction of the unidirectional antenna, unnecessary radiation in a direction other than the directional direction of the antenna can be suppressed. In addition, by using the metal plate 200 as a reflecting plate, it is possible to strengthen radio waves in the direction of the unidirectional antenna.

  100 Polarizer, 101 Radome, 102 Wire Grid, 103 Side, 104 Split Line, 105 Split Arc, 110 Polarizer, 111 Radome Layer, 112 Wire Grid, 113 Side, 114 Split Line, 115 Split Arc, 116 Polarizer Layer, 120 Polarizer, 121 radome, 122 wire grid, 200 metal plate.

Claims (7)

A radome formed of a dielectric material that is opposed to a radiation direction of the antenna and that is inclined with respect to a perpendicular perpendicular to the beam scanning plane of the antenna and intersects the perpendicular;
A plurality of conductive wires made of conductors formed on the surface of the radome;
Polarizer equipped with.   The polarizer according to claim 1, wherein the surface of the radome includes a side surface of a truncated cone. The conducting wire is formed in a straight line connecting diagonals of regions of a substantially trapezoidal shape in which the side surface of the truncated cone is equally spaced in the circumferential direction and unequally spaced in the generatrix direction,
The conductors of the two trapezoidal regions located at the opposite corners of the region are connected to each other at the apex where the two regions located at the opposite corners contact each other. It is connected continuously so as to draw a broken line to the edge of
The polarizer according to claim 2.   The polarizer according to claim 3, wherein the conducting wire is formed so as to be inclined at a constant inclination angle with respect to an arc on the upper base side of the truncated cone in the substantially trapezoidal region. The radome includes a plurality of layers stacked in a radiation direction of the antenna,
The radome layers are each formed with conductive wires having different inclination angles on the surface,
The polarizer according to claim 4.   The polarizer according to any one of claims 2 to 5, wherein the radome has a shape in which the truncated cone is divided by a plane parallel to the perpendicular.   The polarizer of Claim 6 provided with the conductor board which contact | connects the surface parallel to the said perpendicular of dividing the said truncated cone of the said radome.

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