JPH0837419A - Corner reflector antenna - Google Patents

Abstract

PURPOSE:To obtain an antenna whose one exciting element has a comparatively wide beam width and whose beam width versus frequency characteristic is wide. CONSTITUTION:Sub reflecting plates 21, 22 are connected opposite to each other to both ends of a corner reflector 13. An open angle alpha of the reflecting plates 11, 12 is selected to be 140-150 deg., a width W of the reflecting plates 11, 12 is selected to be 5/7-2/3L and a width T of the sub reflecting plates 21, 22 is selected to be 1/7L-1/3L, where L is a distance between an exciting element 14 and an apex.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to, for example, a base station antenna of a mobile communication system, shares two or more frequencies, and has a large horizontal beam width (hereinafter abbreviated as "beam width"). The present invention relates to a corner reflector antenna.

[0002]

2. Description of the Related Art FIG. 4A shows a plan view of a conventional corner reflector antenna. The same rectangular reflectors 11 and 12 are connected to each other at an angle α (α <180 °) at one side edge to form a corner reflector 13, and on the narrow angle side of the corner reflector 13, both reflectors 11 and 12 are separated. A half-wavelength dipole excitation element 14 parallel to both reflectors 11 and 12 is arranged at equidistant positions. In the figure, excitation element 1
4 is perpendicular to the paper surface. The feeder line 15 that is passed through the small hole at the corner of the corner reflector 13 is connected to the excitation element 14. The distance between the corner of the corner reflector 13 and the excitation element 14 (vertical angle distance of the excitation element) is L, the opening angle of the corner reflector 13 is α, and the reflection plates 11 and 1 are
The width of 2 is W.

FIG. 4B shows the calculation of the beam width (width of the main beam of directivity in the plane perpendicular to the reflectors 11 and 12 and the excitation element 14) for frequencies of 0.6f to 2f in the conventional corner reflector antenna. It shows what was done. here,
f is 1 GHz. The antenna is designed to have an equivalent diameter of 100 mm in consideration of making it as thin as possible. At this time, the opening angle α is 120 °, the reflector width W is constant at 50 mm, and the apex angle distance L is changed. As is clear from the figure, the beam width becomes narrower as the frequency becomes higher. Here, at frequency f (= 1 GHz), a beam width of about 125 ° is obtained regardless of the apex angle distance L, but at 2f, the beam width varies depending on the apex angle distance L and the beam width is 9
The beam widths do not coincide with each other from 2 ° to 113 °. When the apex angle distance L is converted into a wavelength, when L = 60 mm, f is 0.
Two wavelengths and 2f are 0.4 wavelengths, and the apex angle distance in terms of wavelength is different. Therefore, the beam width differs depending on the used frequency. By resonating two different frequencies with such a corner reflector antenna, the beam widths in a plane perpendicular to each of the reflectors 11 and 12 and the excitation element 14, that is, in a normal horizontal plane, are made to coincide with each frequency. In order to do so, conventionally, as shown in FIG. 4C, two excitation elements 14 and 16 are used, and the 2f excitation element 16 having a high operating frequency is set closer to the reflection plates 11 and 12, and the apex angle thereof is set. The beam widths are adjusted so that the distance L becomes 0.2 wavelength, that is, the wavelength-converted vertical angle distances of both the excitation elements 14 and 16 are matched.

[0004]

As described above, the conventional method has a drawback that two exciting elements must be arranged in order to operate in a wide band or two frequencies. An object of the present invention is to provide a corner reflector antenna which uses one excitation element and whose beam width in the horizontal plane hardly changes in a wider frequency band than the conventional one.

[0005]

According to the present invention, the sub reflectors are connected to both ends of the corner reflector substantially along the radiation direction of the antenna main beam. Furthermore, in the invention of claim 2, the opening angle of the reflector is approximately 140 degrees to 150 degrees,
The width of each reflector is approximately 5/7 L to 2 / with respect to the vertical angle distance L.
3L, and the width of each sub-reflector is approximately 1 / 7L to 1 / 3L
Is.

[0006]

FIG. 1A shows an embodiment of the present invention, in which parts corresponding to those in FIG. 4A are designated by the same reference numerals. In the present invention, both ends of the corner reflector 13, that is, the reflector 1
Sub-reflecting plates 21 and 22 are respectively coupled to the side edges of 1 and 12 opposite to the coupling side edges thereof, and the sub-reflecting plates 21 and 22 are substantially parallel to the extension direction of the antenna main beam, that is, the corner reflector 13 It is made substantially parallel to the straight line connecting the corner and the excitation element 14. From the point of making the entire occupied space as small as possible, the sub-reflecting plates 21 and 22 are placed inside the circle inscribed at the three corners of the corner reflector 13 and both ends.
Are preferably located in parallel with each other as shown in the drawing, but may be slightly inward with respect to each other. Each width of the sub-reflecting plates 21 and 22 is T. Reflector 1
The effects of the widths W of 1 and 12, the widths T of the sub-reflecting plates 21 and 22, the opening angle α, and the vertical distance L on the beam width will be described below.

FIG. 2A shows the antenna structure of FIG.
The frequency characteristics with respect to the beam width when the widths W of 1 and 12 are changed are calculated.
Similar to the tendency shown in B, the beam width becomes narrower as the frequency becomes higher. However, W = 8 / 13-10 / 13
At L, the beam width tends to become wider again as the frequency becomes higher. From the above, W = 8/13 to 10 /
13L is required. However, T = 2 / 13L, opening angle α = 140 °, and L is the vertical angle distance.

FIG. 2B shows the relationship between the width T of the sub-reflecting plates 21 and 22 and the beam width. In the absence of the sub-reflecting plates 21 and 22 (T = 0), the beam width becomes narrower as the frequency becomes higher. ing. However, when T = 2 / 13L to 4 / 13L, the beam width tends to widen again as the frequency becomes higher, and it can be seen that the directivity of 120 ° beam width is obtained. From the above, the width T of the sub-reflector plates 21 and 22 is 2 / 13L.
~ 4 / 13L is required. However, the reflectors 11 and 12
Width W = 10 / 13L, opening angle α = 140 °, and L is the vertical angle distance.

FIG. 3A shows the frequency characteristics of the beam width with respect to the opening angle α. The opening angle α is 140 ° to 150 °.
It turns out that is optimal. However, the width of the reflector W = 1
0 / 13L, the width T of the sub-reflector is 2 / 13L, and L is the vertical angle distance. FIG. 3B shows the relationship between the vertical angle distance L and the beam width. When the vertical angle distance L is 80 mm, the beam width becomes wider as the frequency becomes higher, but at 60 to 70 mm, the beam width becomes high again. Becomes wider or the beam width hardly changes. Further, when the apex angle distance L is as small as 50 mm, the beam width with respect to the frequency tends to be extremely wide as the frequency is higher. From the above, the apex angle distance is 60 to 70 mm.
Will be optimal. However, the width W of the reflecting plate is 50 mm, the width T of the sub-reflecting plate is 10 mm, and the opening angle α is 140 °.

From the above points, preferable numerical examples are as follows. Reflector width W = 50 mm, sub-reflector width T = 10 mm, opening angle α = 140 °, apex angle distance L = 60
mm, and the beam width at f at this time is 122 ° and at 120 ° at 2f, and it is understood that there is a dimension in which the beam width hardly changes. At this time, the excitation element 14
Can be realized by using a dual-frequency antenna equipped with a parasitic element. As such a dual frequency antenna, for example, as shown in FIG. 1B, a ground layer 25 is formed on one surface of one end of a rectangular dielectric plate 24, and a strip is formed at the center of the other surface by extending from the edge of the dielectric plate 24. Lines (not shown on the back side in the figure) are formed, and parallel two lines 26, one ends of which are respectively connected to the strip line and the ground layer 25, are formed facing each other through the dielectric plate 24. One element 27 of the dipole is formed on one surface of the dielectric plate 24 at one end of the dipole 26 at a right angle thereto, and the parallel two lines 26 are formed on the other side of the other element 2 of the dipole.
8 is formed on the other surface of the dielectric plate 24, and a parasitic element 29 is formed on the dielectric plate 24 very close to the dipole elements 27 and 28. The ground layer 25 side is passed through at the corner of the corner reflector 13, and the dipole elements 27 and 28 are located substantially at the location of the excitation element 14. Radiation is performed at the resonance frequency determined by the dipole elements 27 and 28, and radiation is performed at the resonance frequency determined by the parasitic element 29.

This dual-frequency antenna is described in, for example, Karigami and Ehne, "Characteristics of Printed Dipole Antenna with Parasitic Element", Technical Report AP89-2, 1989. As the excitation element 14, a wideband antenna may be used in addition to the dual frequency antenna.

[0012]

As described above, according to the present invention, by providing the sub-reflecting plate, it is possible to obtain an antenna having a wide frequency characteristic with respect to the beam width and a small diameter by using one exciting element. it can.

[Brief description of drawings]

1A is a plan view schematically showing a corner reflector antenna of the present invention, and FIG. 1B is a perspective view showing an example of a dual frequency printed dipole antenna with a parasitic element.

FIG. 2A is a frequency characteristic diagram of a beam width with respect to a reflector width of a corner reflector antenna of the present invention, and B is a frequency characteristic diagram of a beam width with respect to a sub-reflector width of the corner reflector antenna.

3A is a frequency characteristic diagram of a beam width with respect to an opening angle of the corner reflector antenna of the present invention, and FIG. 3B is a frequency characteristic diagram of a beam width with respect to an apex angle distance of the corner reflector antenna.

FIG. 4A is a plan view schematically showing a conventional corner reflector antenna, B is a frequency characteristic diagram of a beam width with respect to its apex distance, and C is a plan view showing a conventional dual-frequency corner reflector antenna. .

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kunio Takema 1-1-26 Matsumoto-cho, Higashimatsuyama City, Saitama Prefecture (72) Inventor Yoshinori Ebata 2-33-8 Higashioizumi, Nerima-ku, Tokyo No. 8 101

Claims (3)

[Claims] 1. A corner reflector in which first and second reflectors are connected at an angle, and an excitation element disposed inside the corner reflector at substantially equal distances from the first and second reflectors. And a first and a second sub-reflecting plate extending substantially along the main radiation beam direction of the corner reflector antenna are connected to both ends of the corner reflector. And a corner reflector antenna. 2. The opening angle of the first and second reflectors is approximately 1
40 degrees to 150 degrees, and the widths of the first and second reflectors are approximately 5 / 7L to 2 / 3L with respect to the distance L between the corner of the corner reflector and the center of the excitation element. The widths of the first and second sub-reflecting plates are approximately 1 / 7L to 1 /
A corner reflector antenna, which is 3 L. 3. The corner reflector antenna according to claim 1, wherein the excitation element is a dual frequency printed dipole antenna with a parasitic element.