JP2016131278A - Polarization sharing antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization sharing antenna having a structure capable of making the beam width within the horizontal plane of a dipole antenna for vertical polarization coincident with the beam width within the horizontal plane of a dipole antenna for horizontal polarization.SOLUTION: A polarization sharing antenna contains a cross dipole antenna 20 configured so that two dipole antennas 21, 23 having the same resonance frequency are arranged to be perpendicular to each other, and a reflector 10. The reflector 10 contains a partial spherical surface reflection part 11 having a reflection face. One spherical plane is divided into two curved planes by a circle corresponding to an intersection line between the spherical plane and one flat plane, and the reflection face of the reflector 10 has the shape of one of the curved planes which has a smaller area. The cross dipole antenna 20 is located at a position which is away from the intersection point between the reflection face and a line connecting the center of a spherical body having the spherical plane on the surface thereof and the center of the circle toward the circle along the line by the distance corresponding to a quarter of the wavelength corresponding to the resonance frequency so that the line is perpendicular to the respective extension directions of the antenna elements 21a, 23a constituting each dipole antenna 21, 23.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a polarization sharing antenna that can be used for mobile radio communication, fixed radio communication, and the like.

  In recent years, the traffic of mobile communication has increased at a rate of 2 times / year, so that the efficiency of radio resources is desired. For this reason, MIMO (multiple-input and multiple-output) technology that increases frequency utilization efficiency and wireless transmission speed is employed in mobile communication base station antennas. According to MIMO technology, a large number of antennas are required, but taking into account the space restrictions for installing the base station antenna, a dual-polarized antenna that shares orthogonal vertical polarization and horizontal polarization is often used. . However, according to the dual-polarized antenna, which consists of a vertically polarized dipole antenna arranged perpendicular to the ground and a horizontally polarized dipole antenna placed horizontally with the earth, the horizontal polarization plane of the vertically polarized dipole antenna It is known that the beam width differs from the horizontal plane beam width of the horizontally polarized dipole antenna. For this reason, in such a dual-polarized antenna, various techniques have been developed in order to match the beam widths in the horizontal plane as much as possible (see, for example, Patent Document 1 and Non-Patent Document 1).

JP 09-98019 A

Yasuko Kimura, Yoshio Ebine, “Narrow beam of 3 sector polarization diversity antenna for base station in mobile communication”, IEICE Technical Report, AP2005-94, pp.623-67, Oct.2005.

  For example, according to the invention disclosed in Patent Document 1, it is necessary to combine two vertically polarized dipole antennas and one horizontally polarized dipole antenna with respect to one flat reflector. To make the beam width in the horizontal plane of two vertically polarized dipole antennas equal to the beam width in the horizontal plane of one horizontally polarized dipole antenna, only the distance between each antenna element constituting each dipole antenna and the flat reflector In addition, it is necessary to adjust the horizontal distance between the antenna elements constituting the two vertically polarized dipole antennas. For this reason, there has been a problem that the number of parts and many elements to be adjusted are large.

  An object of the present invention is to provide a dual-polarized antenna having a simple configuration capable of matching the horizontal plane beam width of a vertically polarized dipole antenna with the horizontal plane beam width of a horizontally polarized dipole antenna. To do.

  The dual-polarized antenna according to the present invention is a dual-polarized antenna including a cross dipole antenna configured by orthogonally arranging two dipole antennas having the same resonance frequency, and a reflector, and the reflector is a single spherical surface. Including a partial spherical reflector having a reflective surface with a shape having a smaller area among the curved surfaces obtained by dividing the spherical surface by a circle that is an intersection line with the one plane. In a position separated from the intersection of the straight line connecting the center of the sphere with the center of the circle and the reflection surface and the reflection surface toward the circle along the straight line by a quarter of the wavelength corresponding to the resonance frequency, The straight line is arranged so as to be orthogonal to the extending direction of each antenna element constituting each dipole antenna.

  According to the present invention, a simple configuration combining the partial spherical reflector with a crossed dipole antenna composed of one vertically polarized dipole antenna and one horizontally polarized dipole antenna is used. The beam width in the horizontal plane of the polarization dipole antenna can be matched with the beam width in the horizontal plane of the horizontal polarization dipole antenna.

The front view of the polarization sharing antenna of an embodiment. Sectional drawing (A-A 'sectional view taken on the line) of the polarization sharing antenna of embodiment. The horizontal plane beam width of the vertically polarized dipole antenna and the horizontal plane beam width of the horizontally polarized dipole antenna (R = 0.35λ) in the dual polarization antenna of the embodiment. The beam width in the horizontal plane of the vertically polarized dipole antenna and the beam width in the horizontal plane of the horizontally polarized dipole antenna (R = 0.53λ) in the dual polarization antenna of the embodiment. In the dual-polarized antenna according to the embodiment, the horizontal plane beam width of the vertically polarized dipole antenna and the horizontal plane beam width of the horizontally polarized dipole antenna (R = 0.70λ). Polarization antenna for reference example. (A) Front view. (B) Sectional drawing (B-B 'line sectional drawing). The horizontal plane beam width of the vertically polarized dipole antenna and the horizontal plane beam width of the horizontally polarized dipole antenna in the dual polarization antenna of the reference example.

  Embodiments of the present invention will be described with reference to the drawings. As shown in FIGS. 1 and 2, the dual-polarized antenna 100 according to this embodiment includes a cross dipole antenna 20 and a reflector 10.

<Cross dipole antenna>
The cross dipole antenna 20 has a conventionally known configuration and is composed of two dipole antennas 21 and 23 having the same resonance frequency f. The two dipole antennas 21 and 23 are arranged orthogonally. Hereinafter, this configuration will be described.

Dipole antenna 21, feed which is connected to one end of each of the two antenna elements 21a to slightly open the pair of antenna elements 21a which are arranged, opposite apart along the perpendicular imaginary line L ₂₁ to the ground It is comprised with the electric wire 21b. If the dipole antenna 21 is a half-wave dipole antenna, each antenna element 21a is typically an electrical conductor having a shape which is stretched formed in a direction parallel to the imaginary straight line L _21, the wavelength corresponding to the resonance frequency f lambda It has a length shorter by a shortening rate of several percent than the length of 1/4. Each feeder line 21b is a coaxial cable, for example. Hereinafter, the dipole antenna 21 is referred to as a vertically polarized dipole antenna 21.

Further, the dipole antenna 23 includes a pair of antenna elements 23a which are spaced slightly apart along the horizontal imaginary line L ₂₃ to the ground, is connected to one end of each of the two antenna elements 23a facing And the feeder line 23b. If the dipole antenna 23 is a half-wave dipole antenna, each antenna element 23a is typically an electrical conductor having a shape which is stretched formed in a direction parallel to the imaginary straight line L _23, 1/4 of the wavelength λ It has a length that is a few percent shorter than the length. Each feeder line 23b is a coaxial cable, for example. Hereinafter, the dipole antenna 23 is referred to as a horizontally polarized dipole antenna 23.

When the vertically polarized dipole antenna 21 and the horizontally polarized dipole antenna 23 are viewed from the direction perpendicular to the virtual straight line L ₂₁ and the virtual straight line L ₂₃ (see FIG. 1), the gap between the two antenna elements 21a facing each other is The vertically polarized dipole antenna 21 and the horizontally polarized dipole antenna 23 are arranged so that the gap between the two opposing antenna elements 23a partially matches. In particular, in the present embodiment, the virtual straight line L ₂₁ and the virtual straight line L ₂₃ have an intersection point P (not shown), and the pair of antenna elements 21a are along the virtual straight line L ₂₁ so as to be symmetric with respect to the intersection point P. are disposed, a pair of antenna elements 23a are arranged along a virtual straight line L ₂₃ so as to be symmetrical with respect to the intersection point P.

<Reflector>
The reflector 10 includes a partial spherical reflecting portion 11 having a partial spherical surface as a reflecting surface, and a cylindrical reflecting portion 13 having a cylindrical reflecting surface as necessary. Hereinafter, this configuration will be described.

  To be precise, the partial spherical surface has a shape having a smaller area among curved surfaces obtained by dividing the spherical surface by a circle that is an intersection line of one spherical surface and one flat surface H. It is sufficient for the partial spherical reflecting portion 11 to have such a partial spherical surface as an electromagnetic wave reflecting surface, and other conditions are not particularly limited, but are formed of, for example, a thin metal.

  The diameter of the cylindrical reflecting surface of the cylindrical reflecting portion 13 is equal to the diameter of the circle. The cylindrical reflecting portion 13 is sufficient if it has such a cylindrical reflecting surface as an electromagnetic wave reflecting surface, and other conditions are not particularly limited, but are formed of, for example, a thin metal. The cylindrical reflecting portion 13 is arranged so that the reflecting surface of the cylindrical reflecting portion 13 is connected to the reflecting surface of the partial spherical reflecting portion 11. In particular, in this embodiment, the partial spherical reflector 11 and the cylindrical reflector 13 are integrally formed, and the reflective surface of the cylindrical reflector 13 is continuously connected to the reflective surface of the partial spherical reflector 11. Yes.

<Relationship between crossed dipole antenna and reflector>
The cross dipole antenna 20 includes a virtual straight line L from an intersection C (not shown) between a virtual straight line L ₁ connecting the center G of the sphere having the spherical surface and the center of the circle and the reflecting surface of the partial spherical reflecting portion 11. It is arranged at a position along the circle ₁ by a length d that is approximately ¼ of the wavelength λ toward the circle. In particular, in the present embodiment, the intersection P between the virtual straight line L ₂₁ and the virtual straight line L ₂₃ is on the virtual straight line L ₁ , and the distance between the intersection P and the intersection C is d. Further, the extending directions of the antenna elements 21a and 23a constituting the dipole antennas 21 and 23 (that is, the virtual straight line L ₂₁ and the virtual straight line L ₂₃ ) are orthogonal to the virtual straight line L ₁ . In other words, the reflector 10 is arranged such that the virtual straight line L ₂₁ is parallel to or on the plane H and the virtual straight line L ₂₃ is parallel to the plane H or on the plane H. On the other hand, a cross dipole antenna 20 is arranged.

  The partial spherical reflecting portion 11 has four through holes (not shown) formed in the vicinity of the intersection C. Each feed line 21b of the vertically polarized dipole antenna 21 is inserted through a corresponding through hole. For example, electrical insulation between the feed line 21b and the partial spherical reflector 11 is maintained via an insulator (not shown). . Similarly, each feed line 23b of the horizontally polarized dipole antenna 23 is inserted through a corresponding through hole, and electrical insulation between the feed line 23b and the partial spherical reflector 11 is maintained through an insulator (not shown), for example. I'm leaning. Each feed line 21b is connected to a feed circuit (not shown) for the vertically polarized dipole antenna 21 through a balun or the like as necessary. Each feed line 23b is connected to a feed circuit (not shown) for the horizontally polarized dipole antenna 23 through a balun or the like as necessary. Since the feeding method and the like are the same as those of the conventional cross dipole antenna, the description thereof is omitted.

<Horizontal beam width>
3 to 5 show the horizontal plane beam width of the vertically polarized dipole antenna 21 and the horizontal plane beam width of the horizontally polarized dipole antenna 23 for the dual polarization antenna 100. In each figure, the vertical axis represents the half power beamwidth [°], which is the beam width in the horizontal plane, and the horizontal axis represents the opening angle θ [°]. Moreover, in each figure, h represents the height of the cylindrical reflective portion 13 (the length of which is parallel to the imaginary straight line L ₁ direction), R represents the radius of the sphere. The opening angle θ is an angle in which the reflection surface of the partial spherical reflector 11 is viewed from the center G of the sphere, in other words, two intersections between an arbitrary plane including the virtual straight line L ₁ and the circle, and the sphere. This is the apex angle when the line segment connecting the two intersections in the triangle formed by the center G of the base is the base.

  As can be seen from FIG. 3 to FIG. 5, when the radius R of the sphere is at least 0.35 times to 0.70 times the wavelength λ, the opening angle θ and the height h of the cylindrical reflecting portion 13 are determined. Depending on the combination, the beam width in the horizontal plane of the vertically polarized dipole antenna 21 and the beam width in the horizontal plane of the horizontally polarized dipole antenna 23 can be matched. Further, the cylindrical reflector 13 is not essential (that is, when the height h = 0), but if the height h is at least 0.058 times to 0.175 times the wavelength λ, the cylindrical reflector is used. Compared to the case where there is no 13, the difference between the beam width in the horizontal plane of the vertically polarized dipole antenna 21 and the beam width in the horizontal plane of the horizontally polarized dipole antenna 23 is not significantly increased. When the height h is in the range of 0.110 to 0.120 times the wavelength λ, the beam width in the horizontal plane of the vertically polarized dipole antenna 21 and the horizontal plane of the horizontally polarized dipole antenna 23 are independent of the opening angle θ. The difference from the beam width is practically sufficiently small (about 10 ° or less), and the usefulness of the cylindrical reflecting portion 13 can be confirmed. Further, as the opening angle θ decreases, the difference between the beam width in the horizontal plane of the vertically polarized dipole antenna 21 and the beam width in the horizontal plane of the horizontally polarized dipole antenna 23 tends to increase. Is preferably 80 ° or more.

  For reference, FIG. 7 shows the horizontal plane beam width of the vertical polarization dipole antenna and the horizontal polarization beam width of the horizontal polarization dipole antenna in the dual polarization antenna 900 different from the dual polarization antenna 100 described above. The dual-polarized antenna 900 is different from the dual-polarized antenna 100 in that it has a reflector 50 instead of the reflector 10 (see FIG. 6). The reflector 50 has not a partial spherical reflection part but a square flat plate reflection part. In addition, for comparison, in the case where rectangular plate-like side wall reflecting portions are extended toward the cross dipole antenna on each of the four sides of the flat plate reflecting portion (however, adjacent side wall reflecting portions are connected to each other as shown in FIG. 6). The beam width in each horizontal plane is also shown in FIG. The cross dipole antenna is disposed at a position separated from the flat plate reflection portion by a length d = λ / 4. As can be seen from FIG. 7, according to the dual-polarized antenna 900 shown in FIG. 6, the vertical polarization dipole antenna has a combination of the side length W of the flat plate reflection portion and the height g of the side wall reflection portion. Although the difference between the beam width in the horizontal plane and the beam width in the horizontal plane of the horizontally polarized dipole antenna can be reduced to some extent, the beam width in the horizontal plane of the vertically polarized dipole antenna and the beam in the horizontal plane of the horizontally polarized dipole antenna The width cannot be matched. From this, the usefulness of the partial spherical reflector can be confirmed.

  As described above, according to the present invention, the beam width in the horizontal plane of the vertically polarized dipole antenna and the horizontally polarized wave can be obtained while combining a conventional crossed dipole antenna with a reflector having at least a partial spherical reflector. The beam width in the horizontal plane of the dipole antenna can be matched.

  In addition, the present invention is not limited to the above-described embodiment, and can be appropriately changed without departing from the spirit of the present invention.

Claims (5)

A cross dipole antenna configured by orthogonally arranging two dipole antennas having the same resonance frequency;
A dual-polarized antenna including a reflector,
The reflector is
Including a partial spherical reflector having, as a reflecting surface, a shape whose area is not large among curved surfaces obtained by dividing the spherical surface by a circle that is an intersection line of one spherical surface and one plane;
The cross dipole antenna is
The length of ¼ of the wavelength corresponding to the resonance frequency from the intersection of the straight line connecting the center of the sphere having the spherical surface to the center of the circle and the reflecting surface toward the circle along the straight line A polarization-sharing antenna, characterized in that the straight line is arranged at a distance so as to be orthogonal to the extending direction of each antenna element constituting each of the dipole antennas. The dual-polarized antenna according to claim 1,
The reflector further includes a cylindrical reflection portion having a cylindrical reflection surface having a diameter equal to the diameter of the circle,
The cylindrical reflector is
A dual-polarized antenna, wherein the reflection surface of the cylindrical reflection portion is disposed so as to be connected to the reflection surface of the partial spherical reflection portion. The dual-polarized antenna according to claim 2,
The dual-polarized antenna according to claim 1, wherein a length of the reflecting surface of the cylindrical reflecting portion in a direction parallel to the straight line is 0.058 to 0.175 times the wavelength. The dual-polarized antenna according to any one of claims 1 to 3,
The polarization antenna according to claim 1, wherein a radius of the sphere is 0.35 to 0.70 times the wavelength. The dual-polarized antenna according to any one of claims 1 to 4,
The dual-polarized antenna according to claim 1, wherein an opening angle when the reflection surface of the partial spherical reflector is viewed from the center of the sphere is 80 ° or more.

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