JP2003008344A - Antenna apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To have two main beams in different directions, to achieve the fitness to the base station antenna of mobile radio communication, and to reduce a side lobe. SOLUTION: Arcuate reflectors 21 and 31 having radiuses of 0.2λand 0.53λ (λis wavelength in use), respectively, are provided while a center axis 22 coincides, an angle α=β to the center axis 22 of the reflection plates 21 and 31 is set to 200 deg., half-wavelength dipole antennas 24 and 25 are arranged on the same surface including the center axis 22 while the antennas 24 and 25 deviate from the center axis to an opposite side by 0.25λeach, and parasitic elements 41 and 42 having a length of 0.4λare arranged at a position of 0.017λ ahead of the dipole antennas 24 and 25. Power is fed to the dipole antennas 24 and 25 via a 90-degree hybrid circuit 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device which can be applied to, for example, a base station antenna device in mobile communication and has two directional characteristic beams in different directions.

[0002]

2. Description of the Related Art Conventionally, it has been known that directivity beams are directed in two different directions by feeding two antenna elements using a hybrid circuit (hereinafter, HYB circuit) having a phase difference of 90 °. FIG. 7 shows a perspective view of such a conventional antenna device. The reflector 11 includes side pieces 11b and 11c in which both side edges of a rectangular main plate 11a are bent and extended at right angles in the same direction.
That is, two radiating elements (dipole antennas) 12 and 13 are installed on the side pieces 11b and 11c side, and these radiating elements 12 and 13 are parallel to the side edges of the reflector 11,
Moreover, the side pieces 11b and 11c are arranged in the arrangement direction. These radiating elements 12 and 13 are respectively connected to the HYB circuit 1
4 are connected to two terminals 14a and 14b. The width W1 of the reflector 11 is about 1λ (where λ is the wavelength used), and the side piece 11b.
And the protrusion length L1 of 11c is about 0.25λ, the radiating element 1
Each length L2 of 2 and 13 is about 0.5λ, the distance D1 between the radiating elements 12 and 13 is about 0.5λ, and the radiating elements 12 and 13 are
The distance S1 between the reflector and the main plate 11a of the reflector 11 is about 0.25λ.
Is.

The signal input to the first terminal 15 of the HYB circuit 14 must be transmitted from the radiating element 13 with a phase difference of the HYB circuit 14, which is delayed by 90 ° in this case, from the radiating element 12. And two radiating elements 12 and 1
The radio waves radiated from 3 are combined, and the directivity thereof is as shown by the curve 18 in FIG. Further, the combined directivity of the radiated radio waves from the radiating elements 12 and 13 based on the signal input to the second terminal 16 of the HYB circuit 14 is a curve 19 in FIG.
As shown in.

[0004]

However, in this conventional antenna device, side lobes peculiar to the array antenna are generated as shown in FIG. That is, in addition to the main beams (beams in the desired direction) 18m and 19m, the main beam 1
Side lobes 18s and 19s of about -10 dB are formed as compared with 8 m and 19 m. Sidelobe 18
s and 19s cause interference, and cause noise and subscriber capacity. An object of the present invention is to provide an antenna device having a small side lobe.

[0005]

According to the present invention, an arc-shaped reflector is used, and the first and second dipole antennas are arranged on the concave side of the arc of the arc-shaped reflector, and the first and second dipole antennas are arranged. The second dipole antenna is arranged in the arrangement direction of both side edges of the reflector and is substantially parallel to the side edges. These first and second dipole antennas are H
Power is supplied with a phase difference of 90 ° by the YB circuit.

[0006] Preferably, on a plane parallel to the plane including both side edges of the reflector and passing through the central axis of the arc of the reflector, the first
And the second dipole antenna is installed at a distance of about 0.25 of the used wavelength from the central axis in the direction of both side edges. Furthermore, it is preferable that a second arc-shaped reflector having a central axis substantially the same as that of the reflector is provided outside the arc-shaped reflector.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to examples. (First Embodiment) FIG. 1A is a perspective view of a first embodiment of the present invention, and FIG. 1B is a plan view of a reflector 21. Working frequency λ
Is 2 GHz. As the arc-shaped reflection plate 21, a cylinder having a radius r1 = 6 cm (of about 0.4 wavelength at the used frequency) is formed into one of two parts divided by a plane passing through the central axis 22. On the plane 23 including the central axis 22 and both side edges 21a and 21b of the reflector 21, one side edge 21a (left) side S1 = 3 from the central axis 22.
First dipole antenna 24 at the position of 0 mm (0.2λ)
However, the other side edge 21b (right) side S1 = 3 from the central axis 22
The second dipole antenna 25 at the position of 0 mm (0.2λ)
Are arranged, and these dipole antennas 24 and 25 are parallel to the central axis 22. The dipole antennas 24 and 25 are connected to the terminals 14a and 14 of the HYB circuit 14, respectively.
b, respectively. The arc-shaped reflector 21 is a metal plate, a mesh or a wedge sufficiently small for the wavelength, or a metal foil (metal layer) supported by a dielectric.

FIG. 2 shows the directivity characteristic 19 on the surface side perpendicular to the dipoles 24 and 25 when power is supplied to the terminal 15 of the HYB circuit 14. The main beam direction (the direction of maximum gain) is about 20 ° to the left of the front of the antenna (90 °), and the beam width (the angle between the points where the gain is decreased by −3 dB with respect to the maximum value of the gain). ) Is about 62 ° main beam 1
It will be 9m. Also, it can be seen that the side lobe 19s is about -18 dB in the right 90 ° (0 ° in the figure) direction with respect to the front of the antenna, which is about 8 dB smaller than that shown in FIG. When power is supplied to the terminal 16 of the HYB circuit 14, its directional characteristics are characteristic 19 and the front of the antenna (90 in FIG. 2).
(Direction °) becomes symmetrical.

As shown in FIG. 1B, the angle range α of the arc-shaped reflecting plate 21 with respect to its central axis 22 is 180 ° to 200 °.
Is preferable, and when the angle is larger than 200 °, the frequency characteristic is deteriorated, and the direction of the main beam 19m is in front (90 ° in FIG. 2).
Direction). The distance S2 = 2S1 between the first and second dipole antennas 24 and 25 is 0.25λ˜0.
About 75λ is preferable, and about 0.5λ is particularly preferable. (Second Embodiment) FIG. 3A is a perspective view of a second embodiment of the present invention.
, And the parts corresponding to those in FIG. 1A are denoted by the same reference numerals.

The second embodiment is different from the antenna device of the first embodiment in that the radius r2 is provided outside the arc-shaped reflector 21.
A circular arc-shaped reflector 31 of 8 cm (about 0.53 wavelength at the used frequency) is provided with the central axis 22 as the central axis. In this example, both side edges 21a and 21b of the reflection plate 21 are located on the surface 23, and both side edges 31a and 31b of the reflection plate 31 are located. Others are the same as those in the first embodiment shown in FIG. 1A. is there. FIG. 4 shows a terminal 15 of the HYB circuit 14.
Shows the directivity in the plane perpendicular to the dipole antennas 24 and 25 when the power is supplied to the antenna. The frequency used is 2 GHz. From FIG. 4, the main beam 19m is directed to the left by about 20 ° with respect to the front of the antenna and the beam width is about 60.
It becomes a beam of °.

The side lobe 19s is approximately -1 in the right 75 ° direction with respect to the front of the antenna as compared with the main beam 19m.
It is 9 dB, which is smaller than that shown in FIG. 7 by about 9 dB. Both side edges 31a and 31b of the outer arc-shaped reflector 31 have a plan view as shown in FIG. 3B.
It may be positioned on the front side of the antenna without being positioned on the surface 23 including both side edges 21a and 21b of the inner arc-shaped reflector 21. That is, the angle β of the outer reflector 31 with respect to the central axis 22 is equal to the angle α of the inner reflector 31 with respect to the central axis 22.
It may be larger. When α = β, 180 ° < α =
β < 200 ° is preferable. 160 ° when α <β
< Α < 200 °, 160 ° < β < 220 ° are preferable. If the angle is larger than these angles, the frequency characteristics deteriorate and the direction of the main beam faces the front of the antenna device.
The dipole antennas 24 and 25 may be moved back and forth by about 0.07λ with respect to a plane 26 that is perpendicular to the plane that passes through the central axis 22 and bisects the arc-shaped reflector 21 and that includes the central axis 22. This also applies to the first embodiment. Note that α
For> 180 °, the side edges 21a and 21b, and 31a and 31b, respectively, are preferably located equidistant from the surface 26 and forward. Radius r of the outer circular reflector 31
2 may be larger than the radius r1 of the inner arc-shaped reflector 21, but if it is made too large, the size of the antenna device becomes large and the size thereof is limited.

(Third Embodiment) A perspective view of a third embodiment of the present invention is shown in FIG. 5A and a plan view thereof is shown in FIG. 5B, and portions corresponding to those in FIG. 3A are designated by the same reference numerals. The third embodiment is different from the second embodiment shown in FIG. 3A in that the central axes 22 of the inner arc-shaped reflector 21 and the outer arc-shaped reflector 31 are respectively different.
The angles α and β with respect to 220 ° and the side edges 21a and 3
1a and the central axis 22 are located on the same plane, and the side edges 21b and 31b and the central axis 22 are located on the same plane. Further, in this third embodiment, each dipole antenna 24 and 25 is
With a distance D2 = 0.25 cm (about 0.017 wavelength at the used frequency) from these antennas in front of
The parasitic elements 41 and 42 of mm (about 0.4 wavelength at the used frequency) are arranged.

FIG. 6 shows the directivity in the plane perpendicular to the dipole antennas 24 and 25 when power is supplied to the terminal 15 of the HYB circuit 14. The frequency used is 2 GHz. The main beam 19m is on the left about 20 ° with respect to the front of the antenna, and its beam width is about 60 °. Further, it can be seen that the side lobe 19s is about -24 dB in the right 75 ° direction with respect to the front of the antenna as compared with the main beam, which is 14 dB smaller than that shown in FIG. 7. The parasitic elements 41 and 42 may be smaller than 0.5λ.

Although the embodiment has been described with the dimension at 2 GHz, the dimension can be changed by the wavelength ratio according to the frequency used, and the other frequency can be used. It should be noted that the present invention is not limited to the above-described embodiment, but may be modified in other forms having the same function, and the present invention can be variously modified and added within the scope of the above-mentioned configuration. For example, in contrast to the first embodiment shown in FIG. 1, the third embodiment shown in FIG.
The parasitic elements 41 and 42 in the embodiment may be installed in front of the dipole antennas 24 and 25. Furthermore, the first to third
A plurality of the antenna devices shown in the embodiment may be arranged in the extension direction of the dipole antennas 24 and 25.

[0015]

As described above, the antenna device of the present invention can reduce side lobes as compared with the conventional antenna device.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing the directivity of the antenna device of the first embodiment shown in FIG.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram showing the directivity of the antenna device of the second embodiment shown in FIG.

FIG. 5 is a diagram showing a third embodiment of the present invention.

6 is a diagram showing the directivity of the antenna device of the third embodiment shown in FIG.

FIG. 7 is a perspective view showing a conventional antenna device.

8 is a diagram showing an image of directivity in the conventional antenna device shown in FIG.

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5J020 AA03 BA08 BC03 BC09 DA09                 5J021 AA02 AA07 AB03 BA01 CA06                       DB02 DB03 FA34 GA05 GA08                       HA05 HA10

Claims (5)

[Claims] 1. An arcuate reflector and first and second arcuate reflectors arranged on the concave side of the arcuate reflector in the direction of arrangement of both side edges of the arcuate reflector and substantially parallel to the side edges. An antenna device comprising: a dipole antenna; and a hybrid circuit that feeds the first and second dipole antennas with a phase difference. 2. A second arc-shaped reflector having a center axis substantially the same as the center axis of the arc of the arc-shaped reflector is provided on the opposite side of the arc-shaped reflector from the first and second dipole antennas. The antenna device according to claim 1, wherein: 3. A first parasitic element and a second parasitic element in front of the first dipole antenna and the second dipole antenna, respectively.
The antenna device according to claim 1, further comprising a parasitic element. 4. The first dipole antenna and the second dipole antenna are located on the same plane including substantially the central axis of the arc of the arc-shaped reflector, as claimed in any one of claims 1 to 3. The antenna device as described in 1. 5. An antenna device comprising a plurality of the antenna devices according to claim 1 arranged vertically.