JPH10335929A - Antenna for horizontally polarized wave - Google Patents

Abstract

PROBLEM TO BE SOLVED: To constitute a polarized wave diversity antenna of a mobile communication base station in a small size. SOLUTION: An antenna for horizontal polarized wave is constituted, by arranging reflecting plates 21a, 21b, and 21c in the form of an equilateral triangular pipe and attaching one ends of each two monopole antennas 31a and 32a, 31b and 32b, and 32c and 32c to each plate 21a, 21b, and 21c, with the antennas being arranged in a horizontal plane in a state, where the antennas are inclined so that their front approach each other. In each two monopole antennas, antennas 7a, 7b, and 7c for vertically polarized waves are respectively attached to the plates 21a, 21b, and 21c. Each two monopole antennas are fed with electricity in an equal-amplitude opposite-phase state. In addition, reflecting plates 22a, 22b, and 22c are arranged closely to the backs of the plates 21a, 21b, and 21c, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal polarization antenna used for a polarization diversity antenna of a mobile communication base station such as a mobile phone.

[0002]

2. Description of the Related Art In a car / mobile phone system, a fan-shaped three-sector configuration in which one cell (zone) is divided at equal angles may be used in order to improve the frequency use efficiency. At this time, the directivity of the base station antenna in the horizontal plane is 12
The beam width becomes 0 °. Here, in order to introduce polarization diversity reception into a base station, it is necessary to prepare two radiating elements, a vertical polarization antenna and a horizontal polarization antenna, as base station antennas.

When a base station polarization diversity antenna is configured for a three-sector radio zone, both the vertical polarization antenna and the horizontal polarization antenna have a directivity in the horizontal plane of 120.
° It is necessary to set the beam width. Generally, in a vertically polarized antenna, an antenna having a beam width of 120 ° can be realized by setting the width W of the plane reflector at 0.7 wavelength or more and the distance Sv between the antenna and the plane reflector at 0.25 wavelength.

FIG. 8 also shows an antenna for horizontal polarization.
As shown in FIG. 2A, this can be easily realized by attaching the horizontally polarized dipole antenna 1 to the front surface of the plane reflector 2. Here, the directivity of the antenna is determined by the width W of the plane reflector and the distance Sh between the reflector 2 and the dipole antenna 1. For example, by setting W = 0.78 wavelength and Sh = 0.45 wavelength, it is possible to experimentally obtain a directivity of 120 ° beam width as shown in FIG. However, the front-to-back ratio of the directivity in the horizontal plane is in a poor state of 3.5 dB.

In order to improve the front-to-back ratio of the directivity in the horizontal plane, it is necessary to increase the width of the reflector. Increasing the width of the reflector increases the wind receiving area and increases the wind pressure load. The wind pressure load is proportional to the shape of the antenna and the wind receiving area. Also, as shown in FIG. 8B, three antennas for three sectors can be integrated by arranging antennas on each side of the equilateral triangle. That is, three reflectors 2
a, 2b, 2c constitute a regular triangular tube, and horizontal low-wave dipole antennas 1a, 1b, 1c are attached to the respective reflectors 2a, 2b, 2c outside the triangular tube. By housing this whole inside the cylindrical antenna cover 6,
The size of the antenna can be substantially reduced, and the wind pressure load can be reduced. In addition, the shape factor with respect to the wind pressure load is two to three times smaller for a cylinder than for a prism.

If the width of the reflecting plate is fixed at W = 0.78 wavelength, the interval Sv between the antenna of the vertical polarization antenna and the plane reflecting plate can be obtained at a beam width of 120 ° at 0.25 wavelength. On the other hand, in the case of the antenna for horizontal polarization, the interval Sh between the antenna and the reflector needs to be 0.45 wavelength. In order to reduce the size of the antenna, it is necessary to reduce the diameter of the substantial equivalent cylinder. Therefore, it is necessary to reduce the distance Sh so as to be equal to or less than Sv of the vertically polarized antenna. However, in the prior art, the interval Sh is set to 0.
If the spacing is equal to or less than the spacing Sv of the 25-wavelength and vertical-polarization antennas, the beam width in the horizontal plane becomes as small as about 60 °, and a problem arises in that an antenna with a horizontal polarization of 120 ° cannot be realized.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a horizontally polarized antenna capable of relatively freely selecting a beam width in a horizontal plane and having a small size. It is another object of the present invention to provide a horizontally polarized antenna which achieves the above object and can improve the front-to-back ratio characteristic of directivity in a horizontal plane.

[0008]

According to the present invention, two monopole antennas are arranged at an interval with respect to a vertically provided reflector, and these monopole antennas are opposite to each other at equal amplitudes in a horizontal plane. The two monopole antennas are phase-fed and are inclined inward so that their tips approach each other.

According to this configuration, the beam width of the directivity in the horizontal plane can be controlled by changing the element length of the two monopole antennas by about 0.25 to 0.5 wavelengths. The beam width of the directivity in the horizontal plane can be controlled by changing the element spacing between the two monopole antennas. By combining the above, the beam width of the directivity in the horizontal plane can be set relatively easily and freely.

A second planar reflector is provided in close proximity to the monopole antenna of the reflector and on the reflection side, and the size and spacing of these reflectors are selected to improve the front-to-back ratio of directivity in the horizontal plane. be able to.

[0011]

FIG. 1 shows an embodiment of the present invention.
A rectangular planar reflector 21 is vertically arranged, and two monopole antennas 31 and 32 are provided in a horizontal plane substantially at the center of the front surface of the planar reflector 21. Monopole antenna 31,
32, the inner septum S of the tip than the distance S _s of the reflecting plate 21 side end
They are inclined inward from each other so that ₁ is small. The angles θ with respect to the horizontal line are made equal to each other. The monopole antennas 31 and 32 are insulated from the end of the plane reflector 31 and held by the reflector 31. In this example, the midpoint O of the monopole antennas 31, 31 coincides with the center point of the plane reflector 21.

The reflector 2 of the monopole antennas 31, 32
One end is connected to the power supply terminal 5 through the power supply lines 41 and 42, respectively.
Are inserted, and the monopole antennas 31 and 32 are fed with the same amplitude and opposite phases. In this embodiment, a flat reflector 22 is further provided in close proximity to the flat reflector 21 on the side opposite to the monopole antennas 31 and 32 (back surface). In this example, the reflector 22 is also rectangular, and its center is opposed to the center of the reflector 21, and the size of the reflector 22 is approximately the same as that of the reflector 21.

The directivity in the horizontal plane of the antenna structure shown in FIG. 1 was analyzed by the moment method using a wire grid model. First, indicating element spacing, i.e. the relationship between the distance S _s and HPBW in the horizontal plane of the monopole antenna 31 and 32 in FIG. Each width W1 of the reflection plate 21 is set to 0.6 wavelength,
W2 / W1 is 0.9 element length, that is, monopole antenna 3
In this case, the length L of each of the first and second elements 32 is determined to be 0.25 wavelength, and the inclination angle θ of the elements (monopole antennas) 31 and 32 is set to 45 °.

[0014] The result from the element spacing S _s beamwidth increases as increases, and the beam width is 90 ° to 180 ° the element spacing S _s a change in 0.3λ~0.6
The degree can vary greatly. Next, FIG. 3 shows the relationship between the beam width in the horizontal plane and the inclination angle θ of the element. This reflector width W1 of 0.6 wavelength, the W2 / W1 0.9, 0.25 wavelength element length L, and the element spacing S _s 0.
48 wavelengths. From this figure, the beam width in the horizontal plane increases as the inclination angle θ of the element increases.
When the tilt angle θ changes from 30 ° to 60 °, the beam width becomes about 80.
It greatly changes from ° to 170 °.

FIG. 4 shows the relation between the element length L and the beam width in the horizontal plane. This 1.0 wavelength reflector width W1, a W2 / W1 0.9, 0.7 wavelength element spacing S _s,
The element inclination angle θ was set to 45 °. As shown in the figure, as the element length L becomes shorter, the beam width in the horizontal plane becomes larger. When the element length L is changed by 0.25λ to 0.5λ, the beam width greatly changes to about 60 ° to 170 °.

As described above, each parameter, that is, S _s ,
By appropriately selecting θ and L, the beam width in the horizontal plane can be greatly changed. Even if one parameter is fixed, the beam width can be freely selected by selecting the other one or two parameters. It is easy to make the beam width in the horizontal plane of the three-sector base station antenna 120 °.

FIG. 5 shows the relationship between the directivity in the horizontal plane and the front-to-back ratio when the two reflectors 21 and 22 are arranged. The width W1 of the reflector 21 is 0.6 wavelength, the element interval S _S is 0.48 wavelength, the element length L is 0.25 wavelength, and the element inclination angle θ is 45.
°, the distance between the first reflector 21 and the second reflector 22 is d =
The ratio of the directivity in the horizontal plane to the width W2 of the second reflector 22 / the width W1 of the first reflector 21 is shown as a wavelength of 0.06. The lengths of the reflection plates 21 and 22 were the same.
When W2 / W1 = 0.9, the front-to-back ratio is the largest.
By making the width W2 of the second reflector 22 slightly smaller than the width W1 of the first reflector 21, it is improved by about 13 dB as compared with the case without the second reflector 22.

FIG. 6 shows the front-to-back ratio of the directivity in the horizontal plane when the distance d between the reflectors 21 and 22 is changed. Reflector 21
The width W1 0.6Ramuda, the width W2 0.5 of the reflector 22, the same length of the reflecting plates 21 and 22 and the element spacing S _S 0.4
2λ, element length L is 0.25λ, element inclination angle θ is 45
°. From this figure, the interval d is 0.005λ to 0.1.
At 4λ, the front-to-back ratio is set to 20 dB or more, which indicates that the device can be used sufficiently.

In the calculations in FIGS. 2 to 5 and FIG. 7, the length (vertical direction) of the reflectors 21 and 22 was set to 1.5λ. Usually, it is considered that a plurality of antennas shown in FIG. 1 are vertically arranged at one wavelength interval and used as a so-called array antenna, and the length of the reflectors 21 and 22 in the vertical direction is sufficiently longer than the wavelength. . FIG. 7 shows an antenna apparatus for polarization diversity of an asector to which the present invention is applied. The reflecting plates 21a, 21b, 21c are provided so as to form a regular triangular cylinder, and the reflecting plates 21a, 21b, 21c are respectively provided with monopole antennas 31a, 32a, 31b, 32b, 3b.
1c, 32c are provided, respectively, and the reflection plates 21a,
The reflection plates 22a, 22 proximate to the back surfaces of 21b, 21c
b and 22c are provided respectively. Further, each monopole antenna 31a, 32a, 31b, 32b, 31c, 32
supporting pieces 8a, 8 perpendicular to the respective reflectors at the midpoint O of c
b, 8c via vertical polarization antennas 7a, 7b, 7c
Is attached. The entirety is covered with a cylindrical radome 9 to ensure weather resistance and reduce wind load.

The dimensions of this embodiment are, for example, L in the MHz band.
= Λ / 4, S _C = 160 cm, θ = 45 °, W1 = 20
0 cm, W2 = 180 cm, d = 20 cm, support piece 8
a, 8b, and 8c are set to 0.25λ, and the radome 9
Are close to the vertical polarization antennas 7a, 7b, 7c, and the beam width in the horizontal plane of each horizontal polarization antenna is set to approximately 12.
° and could be.

[0021]

As described above, according to the present invention,
The length of the monopole antenna L, the interval S _S monopole antenna, by adjusting either the angle of inclination θ of the monopole antenna, the horizontal beam width can be relatively greatly changed, thus also parameters 3 Therefore, even if one of them is fixed, the other one or two parameters
The horizontal beam width can be predetermined.

Therefore, even when the antenna is configured as a polarization diversity used together with the vertical polarization antenna, the protruding length from the reflector can be made smaller than that of the vertical polarization antenna. It can be easy to withstand. By providing the second reflector close to the rear surface of each reflection plate, the front-rear ratio characteristic of directivity in a horizontal plane can be improved.

[Brief description of the drawings]

FIG. 1 is a structural view of a horizontally polarized antenna of the present invention.

FIG. 2 is a diagram showing a beam width characteristic in a horizontal plane with respect to an element interval S _S in the horizontally polarized antenna of the present invention.

FIG. 3 is a diagram showing a beam width characteristic in a horizontal plane with respect to an inclination angle θ of an element in the antenna for horizontal polarization of the present invention.

FIG. 4 is a diagram showing a beam width characteristic in a horizontal plane with respect to an element length L in a horizontally polarized antenna according to the present invention;

FIG. 5 is a diagram showing a front-rear ratio characteristic of directivity in a horizontal plane with respect to a reflector width in a horizontally polarized antenna of the present invention;

FIG. 6 is a diagram showing a front-rear ratio characteristic of directivity in a horizontal plane with respect to a distance between reflectors in the antenna for horizontal polarization of the present invention;

FIG. 7 is a plan view showing a polarization diversity antenna using the horizontally polarized antenna of the present invention.

8A is a diagram illustrating a conventional horizontal polarization antenna, and FIG. 8B is a plan view illustrating a conventional horizontal polarization antenna having a three-sector configuration.

FIG. 9 is a diagram showing a directional characteristic in a horizontal plane of the conventional horizontal polarization antenna shown in FIG. 8A.

Claims (2)

[Claims] 1. A reflector comprising two reflectors and two monopole antennas, wherein the two monopole antennas are disposed on a surface substantially perpendicular to the reflectors, and the two monopole antennas are provided at the reflector side ends of the two monopole antennas. A horizontally polarized antenna, wherein the two monopole antennas are tilted inward so that the distance between the ends is smaller than the interval, and the two monopole antennas are fed in opposite phases. 2. The horizontally polarized antenna according to claim 1, wherein a second reflector having substantially the same size is disposed on the opposite side of the reflector from the monopole antenna. A horizontally polarized antenna, characterized in that: