JPH11308043A - Antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize an antenna for a mobile communication base station 60 deg. sector zone so as to house it in a radome of 100 mm diameter. SOLUTION: Dipole antennas 21 and 22, which are vertically extended with an interval D≈1/4 wavelength kept with respect to a vertical reflector 1, and as for the antennas 21 and 22, a horizontal interval S≈1/2 wavelength, and a vertical interval H≈1/2 wavelength, and they are subjected to common mode feeding. Parasitic elements 41 and 42 are provided at positions that are an interval G≈0.177 wavelength or less, side plane reflectors 51 and 52 which are inclined at an angle θ≈2.0 deg. outwardly from a plane perpendicular to the reflector 1 are provided integrally with T≈0.13 wavelength on both sides of the reflector 1 and the width of the reflector 1 is set W≈0.5 to 0.57 wavelength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used, for example, in a base station antenna apparatus in mobile communication, and in-phase combines two directional radiated beams so that the beam width in a horizontal plane is approximately 60 °. In particular, the present invention intends to reduce the size of the antenna device.

[0002]

2. Description of the Related Art FIG. 12 shows a conventional antenna device of this kind. Half-wavelength dipole antennas 21 and 22 which are opposed to the vertically standing reflecting plate 1 on the same side and extended in the vertical direction are arranged at intervals. Each interval D between the reflector 1 and the dipole antennas 21 and 22 is about a quarter wavelength, the horizontal interval S between the dipole antennas 21 and 22 is about a half wavelength, and the vertical interval H is also about a half wavelength. Wavelength.

[0003] In order to form a half-width of directional characteristics 60 ° in a horizontal plane of the antenna device, that is, a so-called 60 ° beam antenna, as shown in FIG.
A wavelength Wo is required, and the diameter Wo of the protective radome 3 to cover the antenna device needs to be about 0.99 wavelength. FIG. 14 shows the calculated values of the directivity characteristics in the horizontal plane at this time.
It can be seen that the beam width (width at which the half value width is reduced by 3 dB) is 60 °.

In order to further reduce the size of the above-mentioned antenna device, as shown in FIGS. 15 and 16, parasitic elements 41 and 42 are provided in parallel with the dipole antennas 21 and 22 on the opposite side to the reflector 1. There is something that arranges. Reflector 1
The distance D between the dipole antennas 21 and 22 is about a quarter wavelength, the horizontal distance S between the dipole antennas 21 and 22 is about a half wavelength, the vertical distance H is about a half wavelength, Each interval G between the parasitic element 22 and the parasitic elements 41 and 42 is about a quarter wavelength. Parasitic elements 41 and 42
Is about 0.24 wavelength.

In order to obtain a 60 ° beam antenna, the width W of the reflector 1 needs to be about 0.83 wavelength, and the diameter of the radome 3 needs to be about 0.89 wavelength as shown in FIG. As for the characteristics, a beam width of 60 ° is obtained as shown in FIG.

[0006]

The radio zone configuration in the cellular mobile communication system uses a sector zone configuration in which a horizontal plane is angularly divided in order to increase the subscriber capacity and effectively use the frequency. . At this time 36
As the number of sectors that divide 0 °, a three-sector or six-sector wireless zone configuration is often used. 60 ° to cover 360 ° when adopting a 6-sector wireless zone configuration
Six beam antenna devices are required. In order to mount many antenna devices on a rooftop of a tower or a building as described above, miniaturization of the antenna with reduced antenna load and installation space is an important study subject in antenna design.

[0007] The side lobe level in the directional characteristics of the base station antenna is an important amount that determines the amount of interference between radio zones. Reducing the side lobe level allows for repeated use of frequency between closer zones. Reducing the side lobe is also an important consideration in antenna design.

[0008]

An antenna device according to the present invention is a device comprising two dipole antennas, respective parasitic elements and a reflector, and particularly, both sides of the reflector are bent toward the dipole antenna. Extended side reflectors are provided which open slightly outward from each other.

With this configuration, it is possible to reduce side lobes and downsize the antenna device.

[0010]

FIG. 1 shows an embodiment of the present invention.
This example is suitable for a mobile communication base station antenna in which two elements of a 120 ° beam antenna are combined in phase to form a 60 ° beam antenna. Two vertically extending dipole antennas 21 and 22 are provided at a distance D on the same side with respect to the vertically provided reflector 1, and include the dipole antennas 21 and 22, respectively.
Dipole antennas 2 in a plane perpendicular to
A parasitic element 4 which is opposed to the dipole antennas 21 and 22 in parallel at a distance G from the antennas 1 and 22;
1, 42 are provided.

In this embodiment, on both sides of the reflector 1, side reflectors 51, 52 are provided which are inclined at an angle of θ ° outward with respect to a plane perpendicular to the reflector 1. Generally, the reflector 1 and the side reflectors 51 and 52 are integrally formed. Said D
Is about a quarter wavelength, and the dipole antennas 21 and 2
2, the horizontal interval S is about a half wavelength, the vertical interval H is about a half wavelength, and the length of the parasitic elements 41 and 42 is about 0.2.
Four wavelengths (36 mm).

The width W of the reflector 1, the width T of the side reflectors 51 and 52, the inclination angle θ of the side reflectors 51 and 52, and the respective distances G between the dipole antennas 21 and 22 and the corresponding parasitic elements 41 and 42. Can use parameters calculated by the method of moments to determine and optimize each parameter. The moment method is a method in which an antenna is divided into minute sections, the current flowing in the minute sections is obtained from boundary conditions, and the current distribution of the antenna is known, so that the electromagnetic field created by the antenna, the input / output impedance of the antenna, etc. are derived. is there.

Using this moment method, the width W of the reflector 1, the width T of the side reflectors 51, 52, the side reflectors 51, 5
The optimum values of the width W of the reflection plate 1, the width T of the side reflection plate, and the inclination angle θ of the side reflection plate can be determined by changing the inclination angle .theta. In this embodiment, the width W of the reflection plate 1 is set as these optimum values.
0.7 wavelength (105 mm), preferably the side reflector 5
The width of 1,52 is about 0.13 wavelength (20 mm) and the inclination angle is 2
Obtained at 0 ° setting. The diameter of the radome at this time is about 0.82 wavelength (123 mm).

Further, by optimizing the value of each distance G between the dipole antennas 21 and 22 and the corresponding parasitic elements 41 and 42, the size can be further reduced, that is, the width W of the reflector 1 is reduced to 0.5 to 0. .57 wavelength (75-85 mm), for example, as a value that fits in a radome having a diameter of about 0.67 wavelength (100 mm), for example, when W = 75 mm, G = 26.
When 5 mm (0.177 wavelength) or less and W = 85 mm, G
= 20.5 mm (0.137 wavelength) or less.

Hereinafter, it will be described that the above numerical values are optimal. The measurement was performed in the frequency band of 1.920 GHz to 2.160 GHz, and four frequencies (1.920 GHz, 2,000 GHz, 2.0
80 GHz, 2.160 GHz). Figure 2 shows 2.
FIG. 7 is a diagram plotting the beam width with respect to θ when the width T of the side reflector at about 000 GHz is about 0.13 wavelength (20 mm): constant. From the figure, the beam width in the horizontal plane is 60 °
It can be seen that a smaller θ is better to obtain. However, when measuring the beam concentration in the above frequency band,
When the inclination of the side reflectors 51 and 52 is small, the beam becomes too sharp in a high frequency band, and the frequency characteristics tend to be poor. Measurement frequency when changing θ with T = 20 mm 1.920 GHz, 2,000 GHz, 2.080 GHz, 2.1
FIG. 5A shows the beam width (dB) at 60 GHz. At 1.920 GHz, the beam width is -2.5 dB and-
Calculate 3.5dB beam width, 2,000GHz and 2.080GHz
Judging from whether or not the beam width of -3 dB at 2.160 GHz falls within this range, the beam width becomes too small in a high frequency band and does not fall within this range, that is, the frequency characteristics are poor. Become. The frequency characteristics are good when θ = 20 or more. From the above, it is optimal to obtain a beam of about 60 ° at θ = 20 ° at T = 0.13 wavelength (20 mm).

FIG. 3 is a plot of the beam width and the side lobe level with respect to T when θ = 20 °: constant at a value of 2,000 GHz. If T = 10 mm or less, the beam width increases, and the side lobe level also increases. When T = 10 mm, the beam width is good and the side lobe level is good at -20 dB or less (generally, the side lobe level should be -20 dB or less). However, if T = 20 mm or less, the frequency characteristics are poor. This means that θ = 20 ° and the beam width (dB) at each measurement frequency when T is changed is shown in FIG. 5B.
From the values in this figure, the beam width is widened at a high frequency, as in the case of FIG. 5A, and the frequency characteristics are deteriorated. From the above, θ
When T = 20 °, T = 20 mm was determined to be optimal. However, the width T is not less than 0.13 wavelength (20 mm), and the beam width is not so reduced from FIG. 3 and the side lobe level is further reduced. Therefore, T may be 0.13 wavelength or more.

With respect to the width W of the reflector 1, the beam width increases when the dipole antenna horizontal interval S is reduced. Therefore, the antenna horizontal interval S is kept constant at about a half wavelength to reduce the size of W. . FIG. 6 is a plot of the beam width in the horizontal plane and the side lobe level with respect to the width W of the reflector 1. Even if the width W of the reflector 1 becomes as small as 0.5 wavelength, the beam width satisfies almost 60 ° beam. The side lobe level also satisfies approximately -20 dB.

To further reduce the size of the antenna device so that the radome diameter becomes 100 mm or less, each distance G between the dipole antennas 21 and 22 and the corresponding parasitic elements 41 and 42 is reduced. When the width T of the side reflectors 51, 52 is about 0.5.
At 13 wavelengths (20 mm) and an inclination angle of 20 °,
The width W of the reflector 1 that fits in a radome having a diameter of 100 mm is 0.57 wavelength (85 mm) or less. On the other hand, if the antenna interval S is set to 0.5 wavelength (75 mm) or less, the beam width becomes large, so that the width W of the reflector 1 is 0.5 to 0.5.
It is required to have a wavelength of 0.57 (75 mm to 85 mm).

FIG. 7 shows the plane of the antenna device and the radome 3.
Assuming that W = 0.5 wavelength (75 mm) (dashed line), the maximum value GM1 of the distance G is about 0.177 wavelength (26.5 mm), and W = 0.57 wavelength (85 m).
m) (solid line), the maximum value GM2 of G is about 0.137
Wavelength (20.5 mm). 8 and 9 show cases where W = 0.5 wavelength (75 mm) and W = 0.5 wavelength (75 mm).
2.000 GH for 0.57 wavelength (85 mm)
The calculated values of the beam width and side lobe level for G at z are shown below. From these calculated values, the beam width is approximately 60 ° at the maximum G where the radome diameter is less than 100 mm. However, since the beam width does not suddenly increase even if G is reduced, G may be smaller than the maximum value that allows the radome diameter to be 100 mm. With respect to the width T of the side reflectors 51 and 52, the beam width increases as T increases.
Is optimally 0.13 wavelength (20 mm). However, even in the case of more than that, a value almost 60 ° is obtained.

As for the side lobe level, even if G is less than the maximum value at a radome diameter of 100 mm, it is almost -20d.
B or less is satisfied. As described above, the width W of the reflector 1 is about 0.5 to 0.57 wavelength, and the dipole antennas 21 and 22
And the distance G between the parasitic elements 41 and 42 is 100 m in diameter.
The maximum value that fits in the radome, which is m, or a value smaller than the maximum value can be said to be optimal. As an example, W = 75 mm (0.5
(Wavelength) T = 20 mm G = 26.5 mm (0.177
FIG. 10 shows the directivity in the horizontal plane in the case of (wavelength), and W = 85 m
m (0.57 wavelength) · T = 20 mm · G = 20.5 mm
FIG. 11 shows the directivity in the horizontal plane in the case of (0.137 wavelength). The horizontal beam width satisfies approximately 60 ° and the side lobe level satisfies approximately −20 dB or less.

[0021]

As described above, according to the present invention, by attaching the side reflection plate obliquely to the reflection plate,
An antenna device with a small radome diameter could be designed. For antenna devices without side reflectors,
The radome diameter has been reduced by about 25-33%.

[Brief description of the drawings]

FIG. 1A is a perspective view showing an embodiment of the present invention, and FIG.
FIG. 2 is a plan view of the antenna device shown in FIG.

FIG. 2 is a view showing a simulation result of a change characteristic of a beam width with respect to θ when T = 20 mm (constant) in the embodiment of FIG. 1;

FIG. 3 is a diagram showing a simulation result of a change in a beam width with respect to T and a change characteristic of a side lobe level with respect to T when θ = 20 ° (constant) in the embodiment of FIG. 1;

FIG. 4 is a diagram showing a directional characteristic in a horizontal plane (at 2,000 GHz) in the optimal design of the embodiment of FIG. 1;

5A is a diagram illustrating a beam width at each frequency when T is set to 20 mm and θ is changed, and FIG. 5B is a diagram illustrating a beam width at each frequency when T is changed when θ is changed to 20 °. It is.

FIG. 6 shows changes in the horizontal plane beam width and the side lobe level with respect to the width W of the reflector when θ = 20 ° (constant) and the dipole antenna interval S is fixed to about a half wavelength in the embodiment of FIG. 1; The figure which shows the simulation result of a characteristic.

FIG. 7 is a plan view showing an embodiment of the present invention adapted to fit in a radome having a diameter of 100 mm.

FIG. 8 shows the distance G between the dipole antenna and the parasitic element and the width T of the side reflector when the width W of the reflector is 0.5 wavelength.
The figure which shows each calculation value of the horizontal beam width (FIG. A) and the side lobe level (FIG. B) with respect to the change of.

FIG. 9 is a diagram showing calculated values of a horizontal beam width (FIG. A) and side lobe levels (FIG. B) with respect to changes in distances G and T when W is set to 0.57 wavelength.

FIG. 10: W = 75 mm, T = 20 mm, G = 26.5
The figure which shows the directional characteristic in the horizontal plane of the antenna apparatus of this invention in the case of mm.

FIG. 11: W = 85 mm, T = 20 mm, G = 20.5
The figure which shows the directional characteristic in the horizontal plane of the antenna apparatus of this invention in the case of mm.

FIG. 12 is a perspective view showing a conventional antenna device.

FIG. 13 is a plan view in which a radome is attached to the antenna device shown in FIG. 12;

FIG. 14 is a diagram showing a directional characteristic in a horizontal plane of the antenna device of FIG. 12;

FIG. 15 is a perspective view showing another example of the conventional antenna device.

FIG. 16 is a plan view in which a radome is attached to the antenna device shown in FIG. 15;

FIG. 17 is a diagram showing a directional characteristic in a horizontal plane of the antenna device shown in FIG. 15;

Claims (2)

[Claims] 1. A reflector on one plane, two dipole antennas parallel to the reflector and spaced apart by a distance D, and the reflector including the dipole antennas, respectively. It is located on a vertical plane and is located away from the respective dipole antennas by a distance G on the opposite side of the reflector, and comprises a parasitic element parallel to these dipole antennas. An antenna device which is excited with the same phase and the same amplitude, and has, on both side ends of the reflector, a side reflector having a width of about 0.13 wavelength or more, which is inclined by about 20 ° outward from the vertical direction of the reflector. An antenna device characterized by the above-mentioned. 2. The antenna device according to claim 1, wherein the width W of the reflector is about 0.5 to 0.57 wavelength, and the distance G between the dipole antenna and the parasitic element is about 0.177 wavelength. An antenna device having a wavelength of about 0.137 or less.