JP2017034452A - Polarization shared array antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization shared array antenna capable of reducing a difference between an in-horizontal-plane beam width of a vertically polarized wave and an in-horizontal-plane beam width of a horizontally polarized wave.SOLUTION: A polarization shared array antenna comprises: a cylindrical reflector 400; a dipole antenna 100X for vertical polarization which is disposed around the cylindrical reflector; first and second half-wavelength dipole antennas 210X and 220X for horizontal polarization that are disposed around the cylindrical reflector; and a planar reflector 300X which is fixed to the cylindrical reflector. A distance between center points of the neighboring half-wavelength dipole antennas for vertical polarization is a 1/2 length of a wavelength λ corresponding to a resonant frequency. A pair of first and second half-wavelength dipole antennas for horizontal polarization are disposed while being separated from the center points by a 1/4 length of the wavelength λ, respectively. The center points of the half-wavelength dipole antennas for vertical polarization are separated from a reflection surface of the cylindrical reflector by the 1/4 length of the wavelength λ.SELECTED DRAWING: Figure 1

Description

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

  In recent years, base station antennas for mobile communication have adopted MIMO (multiple-input and multiple-output) technology that increases frequency utilization efficiency and wireless transmission speed. 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, it consists of a vertically polarized dipole antenna placed perpendicular to the ground and a horizontally polarized dipole antenna placed horizontally to the ground. It is known that the horizontal beam width of a horizontal dipole antenna is different from the horizontal beam width of a 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.

  A technique for optimizing the service area by flexibly changing the antenna directivity by signal processing has attracted attention. This technology enables reallocation of frequency resources, leading to improved communication quality.

  Therefore, the present invention provides a polarization-sharing array antenna that can reduce the difference between the beam width in the horizontal plane of vertical polarization and the beam width in the horizontal plane of horizontal polarization while being an array antenna that can change the directivity of the antenna. For the purpose.

  The dual-polarization array antenna of the present invention includes a cylindrical reflector having a central axis perpendicular to the ground, and a vertically polarized half-wave dipole antenna disposed at equal intervals around the cylindrical reflector. The first half-wave dipole antenna for horizontal polarization having the same resonance frequency as the half-wave dipole antenna for vertical polarization and arranged at equal intervals around the cylindrical reflector, and for the vertical polarization A second horizontally polarized half-wave dipole antenna having the same resonance frequency as that of the half-wave dipole antenna and arranged at equal intervals around the cylindrical reflector, along a direction extending radially from the central axis The distance between the center points of adjacent half-wavelength dipole antennas for vertically polarized waves is half the wavelength corresponding to the resonance frequency. For each of the vertically polarized half-wave dipole antennas, one of the first horizontally polarized half-wave dipole antennas and one of the second horizontally polarized half-wave dipole antennas, Are arranged apart from the center point of the corresponding vertically polarized half-wave dipole antenna by a length of 1/4 of the wavelength corresponding to the resonance frequency in the direction perpendicular to the ground. A planar reflector is disposed between the wave half-wave dipole antennas, and each central point of the vertically polarized half-wave dipole antenna is 1 / of the wavelength corresponding to the resonance frequency from the reflection surface of the cylindrical reflector. 4 apart.

  According to the present invention, the difference between the beam width in the horizontal plane of the vertically polarized wave and the beam width in the horizontal plane of the horizontally polarized wave can be reduced while the array antenna can change the directivity of the antenna.

FIG. 3 is a perspective view of the polarization sharing array antenna of the embodiment. The front view of the polarization shared array antenna of embodiment. The top view of the polarization shared array antenna of embodiment. Directivity (H = 1λ, W = 0.25λ) of the polarization sharing array antenna of the embodiment. (A) Vertical polarization. (B) Horizontal polarization. Antenna characteristics (W = 0.25λ) of the polarization sharing array antenna of the embodiment. (A) Gain. (B) Beam width. Antenna characteristics (H = 1λ) of the dual-polarization array antenna of the embodiment. (A) Gain. (B) Beam width.

  Embodiments of the present invention will be described with reference to the drawings. Note that FIG. 1 to FIG. 3 are for explaining the embodiment of the present invention, and that the dimensions of each component of the polarization sharing array antenna shown in FIG. 1 to FIG. 3 are not necessarily accurate. I want to be.

<Components of a polarization shared array antenna>
As shown in FIG. 1 to FIG. 3, in the polarization sharing array antenna 1 of the present embodiment, the symbol X represents each element of the symbol set {A, B, C, D, E, F}.
1) one cylindrical reflector 400 having a central axis 401 perpendicular to the ground;
2) N vertically polarized half-wave dipole antennas 100X arranged at equal intervals around the cylindrical reflector 400;
3) N first horizontal polarization half-wave dipoles having the same resonance frequency as the resonance frequency f of the vertically polarized half-wave dipole antenna 100X and arranged at equal intervals around the cylindrical reflector 400 An antenna 210X;
4) N second horizontally polarized half-wave dipole antennas 220X having the same resonance frequency as the resonance frequency f and arranged at equal intervals around the cylindrical reflector 400;
5) It includes N planar reflectors 300X fixed to the cylindrical reflector 400 along a direction extending radially from the central axis of the cylindrical reflector 400. However, FIGS. 1 to 3 illustrate the case of N = 6.

<Cylindric reflector>
The cylindrical reflector 400 only needs to have a surface (that is, an outer surface) opposite to the surface (that is, the inner surface) toward the central axis 401 as an electromagnetic wave reflecting surface, and there is no particular limitation on the other conditions. However, it is formed of, for example, a thin metal.

<Half-wavelength dipole antenna for vertical polarization>
In the N vertically polarized half-wave dipole antennas 100X, the linear distance between the center points of the adjacent vertically polarized half-wave dipole antennas 100X is approximately ½ of the wavelength λ corresponding to the resonance frequency f. In addition, the center points of the N vertically polarized half-wave dipole antennas 100X are arranged around the cylindrical reflector 400 so as to be in one plane P (not shown) parallel to the ground. Has been.

  Each vertically polarized half-wave dipole antenna 100X has a pair of antenna elements arranged at a slight distance along a straight line perpendicular to the ground (in FIGS. 1 to 3, the configuration of the dipole antenna is well known, and In order to avoid complication of the figure, the antenna element is not labeled) and a pair of feeders 101X (in FIGS. 1 to 3, the configuration of the dipole antenna is well known, and the figure is complicated) In order to avoid this, only one of the pair of feed lines is provided with a reference numeral). Each of the antenna elements of each vertically polarized half-wave dipole antenna 100X is an electrical conductor having a shape extending along a straight line perpendicular to the ground, and has a quarter of the wavelength λ corresponding to the resonance frequency f. It has a length that is a few percent shorter than the length. One end of the pair of antenna elements faces the other end. The midpoint of an imaginary straight line connecting a pair of opposing ends is the “center point” of the vertically polarized half-wave dipole antenna 100X. One of the pair of feed lines 101X is connected to one end of the corresponding one antenna element, and the other is connected to one end of the corresponding other antenna element. Each feeder 101X is a coaxial cable, for example.

  Each feed line 101X of the vertically polarized half-wave dipole antenna 100X extends toward the cylindrical reflector 400 along a direction extending radially and radially with respect to the central axis 401. Each feed line 101X of the vertically polarized half-wave dipole antenna 100X is inserted through a through-hole (not shown) formed in the cylindrical reflector 400. For example, each feed line is passed through an insulator (not shown). The electrical insulation between 101X and the cylindrical reflector 400 is maintained. Each feed line 101X passes through the inside of the cylindrical reflector 400 and is connected to a feed circuit (not shown) for the vertically polarized half-wave dipole antenna 100X through a balun or the like as necessary. ing. Since the feeding method and the like are the same as those of the conventional dipole antenna, description thereof is omitted.

  The center point of each of the N vertically polarized half-wave dipole antennas 100X is approximately ¼ of the wavelength λ corresponding to the resonance frequency f from the reflection surface (that is, the outer surface) of the cylindrical reflector 400. is seperated. In other words, the distance between the central point of the vertically polarized half-wave dipole antenna 100X and the through-hole of the cylindrical reflector 400 through which each of the feeders 101X is inserted is a wavelength λ corresponding to the resonance frequency f. The length is about 1/4. For this reason, in order to set the diameter of the cylindrical reflector 400 significantly, it is preferable that N is an integer of 3 or more.

<Plane reflector>
Each planar reflector 300X is sufficient if it has its surface as an electromagnetic wave reflecting surface, and other conditions are not particularly limited, but are formed of, for example, a thin metal.

  Between the adjacent vertically polarized half-wave dipole antennas 100X, one of the N planar reflectors 300X is disposed. In the example of FIGS. 1 to 3, N planar reflectors 300X are arranged at equal intervals, and each of the planar reflectors 300X is arranged at an equal distance from the adjacent vertically polarized half-wave dipole antenna 100X. Has been. In other words, the arrangement of the N vertically polarized half-wave dipole antennas 100X around the cylindrical reflector 400 is different from the arrangement of the N planar reflectors 300X around the cylindrical reflector 400. The center axis 401 is shifted by 180 / N degrees. The planar reflector 300A will be described as a representative of the N planar reflectors 300X. In the example shown in FIGS. 1 to 3, between the vertically polarized half-wave dipole antenna 100A and the vertically polarized half-wave dipole antenna 100B. , A single planar reflector 300A is disposed at an equal distance from the vertically polarized half-wave dipole antenna 100A and the vertically polarized half-wave dipole antenna 100B.

  Although there is no special limitation in the shape of each planar reflector 300X, it is preferable that all are the same shape, and in the example shown in FIGS. 1-3, each planar reflector 300X has a rectangular shape. In this example, N planar reflectors 300X are arranged such that the centers of the planar reflectors 300X (intersections of diagonal lines of the planar reflectors 300X) are in one plane Q (not shown) parallel to the ground. Is arranged. Although it is not essential that the surface Q coincides with the surface P, it is preferable that both coincide. More preferably, the plane parallel to the ground that bisects the height of the cylindrical reflector 400 (the length in the direction perpendicular to the ground) coincides with the plane Q and the plane P.

<Half wavelength dipole antenna for horizontal polarization>
For each of the vertically polarized half-wave dipole antennas 100X, one of the N first horizontally polarized half-wave dipole antennas 210X and the N second horizontally polarized half-wave dipole antennas 100X. One of 220X is separated from the center point of the corresponding vertically polarized half-wave dipole antenna by a length of approximately 1/4 of the wavelength λ corresponding to the resonance frequency f in the direction perpendicular to the ground. Are arranged.

  The vertical polarization half-wave dipole antenna 100A will be described as a representative of N vertical polarization half-wave dipole antennas 100X. In the example shown in FIGS. The first horizontally polarized half-wave dipole antenna 210A is separated from the center point of the vertically polarized half-wave dipole antenna 100A vertically upward by about 1/4 of the wavelength λ corresponding to the resonance frequency f. Is arranged. However, the center point of the first horizontally polarized half-wave dipole antenna 210A is located approximately vertically above the center point of the vertically polarized half-wave dipole antenna 100A. Further, with respect to the vertically polarized half-wave dipole antenna 100A, the second horizontally polarized half-wave dipole antenna 220A has a resonance frequency f vertically downward from the center point of the vertically polarized half-wave dipole antenna 100A. The corresponding wavelengths λ are arranged at a distance of approximately 1/4. However, the center point of the second horizontally polarized half-wave dipole antenna 220A is positioned substantially vertically below the center point of the vertically polarized half-wave dipole antenna 100A.

  Each of the first half-wave dipole antennas 210X for horizontally polarized waves has a pair of antenna elements arranged at a slight distance along a straight line parallel to the ground (in FIGS. 1 to 3, the configuration of the dipole antenna is well known). In addition, in order to avoid complication of the figure, the antenna element is not labeled) and a pair of feed lines 211X (in FIGS. 1 to 3, the configuration of the dipole antenna is well known, In order to avoid complication of the figure, only one of the pair of power supply lines is provided with a reference numeral). The antenna elements of the first horizontally polarized half-wave dipole antennas 210X are electric conductors each having a shape extending in a direction parallel to the ground and perpendicular to the central axis 401, It has a length shorter by a shortening rate of several percent than the length of ¼ of the wavelength λ corresponding to the resonance frequency f. Each antenna element has a linear shape or a curved or bent shape as will be described later. One end of the pair of antenna elements faces the other end. The midpoint of the imaginary straight line connecting the pair of opposing ends is the “center point” of the first horizontally polarized half-wave dipole antenna 210X. One of the pair of feed lines 211X is connected to one end of the corresponding one antenna element, and the other is connected to one end of the corresponding other antenna element. Each feeder 211X is a coaxial cable, for example.

  Each feed line 211X of the first horizontally polarized half-wave dipole antenna 210X extends toward the cylindrical reflector 400 along a direction extending perpendicularly and radially to the central axis 401. Each feed line 211X of the first horizontally polarized half-wave dipole antenna 210X passes through a through hole (not shown) formed in the cylindrical reflector 400, for example, via an insulator (not shown). The electric insulation between each power supply line 211X and the cylindrical reflector 400 is maintained. Each feed line 211X passes through the inside of the cylindrical reflector 400, and if necessary, a feed circuit (not shown) for the first half-wave dipole antenna 210X for horizontal polarization via a balun or the like. It is connected to the. Since the feeding method and the like are the same as those of the conventional dipole antenna, description thereof is omitted.

  Similarly, each second horizontally polarized half-wave dipole antenna 220X includes a pair of antenna elements (a configuration of a dipole antenna in FIG. 1 to FIG. 3) that is arranged with a little space along a straight line parallel to the ground. In order to avoid complication of the figure, the antenna elements are not labeled) and a pair of feed lines 221X (in FIGS. 1 to 3), the configuration of the dipole antenna is well known. In addition, in order to avoid complication of the drawing, only one of the pair of power supply lines is provided with a reference numeral). Each of the antenna elements of each second horizontally polarized half-wave dipole antenna 220X is an electrical conductor having a shape extending in a direction parallel to the ground and perpendicular to the central axis 401, It has a length shorter by a shortening rate of several percent than the length of ¼ of the wavelength λ corresponding to the resonance frequency f. Each antenna element has a linear shape or a curved or bent shape as will be described later. One end of the pair of antenna elements faces the other end. The midpoint of the imaginary straight line connecting the pair of opposing ends is the “center point” of the second horizontally polarized half-wave dipole antenna 220X. One of the pair of feed lines 221X is connected to one end of the corresponding one antenna element, and the other is connected to one end of the corresponding other antenna element. Each feeder 221X is, for example, a coaxial cable.

  Each feed line 221X of the second horizontally polarized half-wave dipole antenna 220X extends toward the cylindrical reflector 400 along a direction extending radially and perpendicularly to the central axis 401. Each feed line 221X of the second half-wave dipole antenna 220X for horizontal polarization passes through a through hole (not shown) formed in the cylindrical reflector 400, and for example, via an insulator not shown. The electric insulation between each feeder 221X and the cylindrical reflector 400 is maintained. Each feed line 221X passes through the inside of the cylindrical reflector 400, and if necessary, a feed circuit (not shown) for the second half-wave dipole antenna 220X for horizontal polarization via a balun or the like. It is connected to the. Since the feeding method and the like are the same as those of the conventional dipole antenna, description thereof is omitted.

<Shape of antenna element of half-wave dipole antenna for horizontal polarization>
Depending on the shape and size of the flat reflector 300X, the other end of the antenna element of the first half-wave dipole antenna 210X for horizontal polarization may be close to the flat reflector 300X and both may be electromagnetically coupled. There is a possibility that the other end of the antenna element of the horizontally polarized half-wave dipole antenna 220X is close to the planar reflector 300X and electromagnetically couples them. In order to prevent or reduce such electromagnetic coupling, each antenna element of the first horizontally polarized half-wave dipole antenna 210X has a curved or bent shape in a plane parallel to the ground, and the second horizontal polarization Each antenna element of the wave half-wave dipole antenna 220X may have a curved or bent shape in a plane parallel to the ground.

  The “curved or bent shape” is such that the length along the antenna element from one end to the other end of one antenna element is several percent of the length of ¼ of the wavelength λ corresponding to the resonance frequency f. The length is short by the shortening rate ”, and the linear distance from one end of the antenna element to the other end is only a shortening rate of several percent than the length of ¼ of the wavelength λ corresponding to the resonance frequency f. It means that the shape is shorter than “short length”. As an example of “curvature”, the first horizontal polarization half-wave dipole antenna 210A will be described as a representative of the N first horizontal polarization half-wave dipole antennas 210X, as shown in FIGS. In addition, in the space including the cylindrical reflector 400, the normal is parallel to the vertical direction with respect to the central axis 401 and is divided by a plane including the center point of the first horizontally polarized half-wave dipole antenna 210A. The other end of the antenna element is included, and there is one or more inflection points between one end of the antenna element and the other end. An example of “bending” is bellows folding. Each pair of antenna elements of the first horizontal polarization half-wave dipole antenna 210X and each pair of antenna elements of the second horizontal polarization half-wave dipole antenna 220X may have the same shape. preferable.

<Directivity>
According to the dual-polarization array antenna 1, the number of fed vertically polarized half-wave dipole antennas 100X is one or more, and the first corresponding to each fed vertical polarized half-wave dipole antenna 100X. In addition, the second horizontally polarized half-wave dipole antennas 210X and 220X are also fed, and directivity corresponding to the feeding pattern is obtained.

  In FIG. 4, the planar reflector 300X has the same rectangular shape, its height H (length in a direction perpendicular to the ground) is 1λ, and its width W (length in a direction horizontal to the ground). ) Is 0.25λ, and the directivity of the polarization sharing array antenna 1 when N = 6 is shown. As can be seen from FIG. 4, when power is supplied to the six vertically polarized half-wave dipole antennas 100A, 100B, 100C, 100D, 100E, and 100F, the first and second horizontally polarized half-wave dipole antennas 210A, 210B, 210C, 210D, 210E, 210F, 220A, 220B, 220C, 220D, 220E, and 220F are also fed, and the directivity of the polarization sharing array antenna 1 becomes omni directivity. For example, when feeding power to four vertically polarized half-wave dipole antennas 100A, 100B, 100D, and 100E, the first and second horizontally polarized half-wave dipole antennas 210A, 210B, 210D, 210E, and 220A are used. , 220B, 220D, and 220E are also fed, and the directivity of the polarization sharing array antenna 1 becomes bidirectional directivity. Further, for example, when supplying power to two vertically polarized half-wave dipole antennas 100A and 100B, the first and second horizontally polarized half-wave dipole antennas 210A, 210B, 220A and 220B are also fed and polarized. The directivity of the shared array antenna 1 is unidirectional. Further, for example, when supplying power to one vertically polarized half-wave dipole antenna 100A, the first and second horizontally polarized half-wave dipole antennas 210A and 220A are also fed, and the directivity of the shared polarization array antenna 1 Sex becomes unidirectional.

<Horizontal beam width>
FIG. 5 shows the polarization shared array antenna 1 according to the height H of the planar reflector when the planar reflector 300X has the same rectangular shape, its width W is 0.25λ, and N = 6. The change in gain and beam width is shown. FIG. 6 shows the gain of the polarization-sharing array antenna 1 according to the width W of the planar reflector when the planar reflector 300X has the same rectangular shape, its height H is 1λ, and N = 6. The change in beam width is shown. In FIGS. 5 and 6, HPBW on the vertical axis is the half power beamwidth [°]. In the graph showing the change in the beam width, the beam width in the horizontal plane when the number of feeds to the vertically polarized half-wave dipole antenna is 1 is when the height H is 0 and the width W is smaller than 0.1λ. Since the main beam is divided into two directions and the direction is not the target direction, and the number of feeds to the half-wavelength dipole antenna for vertical polarization is 6, both the horizontal plane beam width and the vertical plane beam width are 360 degrees. It was not plotted because it was.

  As can be seen from FIGS. 5 and 6, it can be seen that the gain and beam width of the polarization sharing array antenna 1 are changed by changing the combination of the height H and width W of the planar reflector 300X. In particular, in order to make the vertical polarization gain, beam width, horizontal polarization gain, and beam width close to each other, it is preferable that the height H is approximately 0.75λ to 1λ and the width W is approximately 0.20λ or more. .

  As described above, according to this embodiment, although the antenna can change the directivity of the antenna, the beam width in the horizontal plane by the dipole antenna for vertical polarization and the beam width in the horizontal plane by the dipole antenna for horizontal polarization in any directivity. The difference with can be reduced.

  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 (6)

A cylindrical reflector having a central axis perpendicular to the ground;
A vertically polarized half-wave dipole antenna disposed at equal intervals around the cylindrical reflector;
A first horizontally polarized half-wave dipole antenna having the same resonance frequency as that of the vertically polarized half-wave dipole antenna and arranged at equal intervals around the cylindrical reflector;
A second horizontally polarized half-wave dipole antenna having the same resonance frequency as that of the vertically polarized half-wave dipole antenna and arranged at equal intervals around the cylindrical reflector;
A planar reflector fixed to the cylindrical reflector along a direction extending radially from the central axis,
The distance between the center points of the adjacent half-wave dipole antennas for vertically polarized waves that is adjacent to each other is a half of the wavelength corresponding to the resonance frequency.
For each of the vertically polarized half-wave dipole antennas, one of the first horizontally polarized half-wave dipole antennas and one of the second horizontally polarized half-wave dipole antennas. Are arranged apart from the center point of the corresponding half-wave dipole antenna for vertical polarization by a length of 1/4 of the wavelength corresponding to the resonance frequency in a direction perpendicular to the ground,
The planar reflector is disposed between the adjacent vertically polarized half-wave dipole antennas,
Each of the center points of the vertically polarized half-wave dipole antennas is a polarization-sharing array antenna that is separated from the reflecting surface of the cylindrical reflector by a quarter of the wavelength corresponding to the resonance frequency. The dual-polarized array antenna according to claim 1,
Each of the planar reflectors has a length in the direction perpendicular to the ground that is not less than 0.75 times and not more than 1 time the wavelength corresponding to the resonance frequency. In the polarization sharing array antenna according to claim 1 or 2,
Each of the planar reflectors has a length in a direction parallel to the ground that is 0.20 times or more the wavelength corresponding to the resonance frequency. The dual-polarized array antenna according to any one of claims 1 to 3,
The antenna element of the first half-wave dipole antenna for horizontal polarization is curved or bent in a plane parallel to the ground,
2. A polarization sharing array antenna, wherein the antenna element of the second half-wave dipole antenna for horizontal polarization is curved or bent in a plane parallel to the ground. The dual-polarized array antenna according to any one of claims 1 to 4,
The number of the vertically polarized half-wave dipole antennas to be fed is one or more,
A polarization sharing array antenna, wherein the first and second half-wave dipole antennas for horizontal polarization corresponding to each of the fed half-wave dipole antennas for vertical polarization are also fed. The dual-polarized array antenna according to any one of claims 1 to 5,
Each of the planar reflectors is disposed at an equidistant position from the adjacent vertically polarized half-wave dipole antennas.

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