JP2001257523A - Base station antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a base station antenna device of a small size, a light weight and a low cost, where radio wave radiation is minimized except for a service area. SOLUTION: A single unipole antenna installed vertically to a ground surface and an antenna device having a reflector in the shape of an umbrella at its upper part are provided for the base station antenna device.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a base station antenna apparatus for a public mobile communication service which has been remarkably developed recently, and more particularly to a base station antenna apparatus suitable for transmitting and receiving radio signals to and from a service area where the service area of the base station is extremely small. It is about.

[0002]

2. Description of the Related Art In a conventional public mobile communication service, various types of base station antenna devices for transmitting and receiving radio signals to and from a service area controlled by each radio base station have been put to practical use. Since the polarization of these antennas is usually vertical polarization according to the system standard, the antenna for vertical polarization will be described below. As the base station antenna device, for example, there is a unipole antenna including a 素 子 wavelength radiating element and a ground plane. When the main plate has a finite length, the directivity greatly changes due to the influence.

Next, there is a slightly complicated type in which a plurality of dipole antennas are arranged at regular intervals and vertically in an array to improve the antenna gain. Furthermore, a plurality of such antenna devices are installed at regular intervals in the vertical or horizontal direction to increase omnidirectionality, or a complex type having improved antenna gain or diversity characteristics. Has also been put to practical use. In some of these antennas, a reflector may be installed near the excitation element of the antenna. This is because the direction of the radio wave radiated from the antenna is radiated strongly only in a specific direction, for example, in a 120-degree sector. Therefore, the gain of the antenna is improved in a specific direction.

[0004] However, the relationship between these antennas and the reflector is that the antenna is installed at a height that is relatively equal to the ground height, that is, on the side surface of the antenna.
The purpose is to increase the intensity in a part of the horizontal direction, which is the radiation direction of radio waves, for example, in a 120-degree sector. In the case of a single excitation element such as a single unipole antenna or a whip antenna, the former is used as an omnidirectional antenna without a reflector, and the latter is provided with a ground wire below the antenna. This is to operate as a single unipole antenna instead of a reflector. As a result, a method has been adopted in which the radiation direction of radio waves is horizontal and the antenna operates as an omnidirectional antenna.

[0005]

However, with the development of mobile communications, especially public mobile communications services,
In order to increase the number of subscribers accommodated and to improve the effective use of frequency, when the above-mentioned unipole antenna or parabolic antenna is used as an antenna of a base station whose service area of one base station is extremely small, the unipole antenna is And the main beam cannot be controlled in the vertical direction. Therefore, as an antenna used for a base station, an antenna having radio wave radiation characteristics adapted to the reduction of the service area of the base station has been required. Radio waves can be effectively radiated into the service area controlled by one radio base station. -On the other hand, outside of the service area, it must have radiation characteristics with as little radio radiation as possible. -Since the system requires a large number of wireless base stations, it should be as inexpensive as possible.・ Easy maintenance and inspection. And so on.

The antenna characteristic conditions for satisfying the above conditions are as follows. -The directivity of the radio wave radiated from the antenna points downward. In particular, it can be easily turned downward even at a large angle that cannot be obtained by the conventional tilt technology. -If one antenna does not satisfy system requirements such as gain, a plurality of antennas can be used. -The production cost is as low as possible.・ Light and small.

[0007]

In order to solve the above-mentioned problems, one unipole antenna which is easy to manufacture and is inexpensive is installed perpendicularly to the ground surface. The reflectors installed on the side surfaces are arranged in a bat-umbrella shape above the unipole antenna (hereinafter, one unipole antenna and the bat-umbrella reflector are referred to as an antenna alone). As a result,
Even at a large angle that cannot be obtained by the conventional tilt technology, it is possible to easily direct the radiation direction of the radio wave largely downward.

Further, by installing a plurality of the above antennas in a vertical direction, it is possible to improve the overall gain of the antenna. The size radius of the above bat-shaped umbrella reflector is about a quarter wavelength, and miniaturization is possible. Further, this reflector may be constituted by a net surface of a similar shape other than a spherical metal plate, and for simplification, the same effect can be obtained even if it is constituted by a bat-umbrella-shaped radial wire. It becomes possible. As a result, the manufacturing cost of the antenna alone including the bat umbrella reflector can be reduced as compared with a conventional antenna having the same characteristics.

Further, the excitation element of the above-mentioned antenna does not necessarily need to be limited to a unipole antenna. That is, if the antenna has the same electrical characteristics as the unipole antenna, it is possible to provide the same electrical characteristics by installing a bat-shaped umbrella-shaped reflector above the antenna. In actual use, a plurality of the above-mentioned antennas are mounted on a support column in a vertical direction. In this case, in order to improve the weather resistance and the impact resistance, etc., the whole of each antenna is often covered with a spherical or elliptical radome. Further, an antenna device installed in a city or the like may be provided with lighting or the like for aesthetic purposes.
Even in such a case, to facilitate maintenance and inspection,
The power supply circuit for each antenna unit and the wiring of the lighting and the like were accommodated in the support, and the antenna device, the power supply circuit, the support and the like were detachable using a connector.

[0010] By providing the above configuration, the present invention can satisfy the demand for the antenna device.

[0011]

FIG. 1 shows an antenna unit 1 according to the present invention.
The following is a basic embodiment of the present invention. In the figure, antenna 1 alone
The received radio wave received at (1) arrives at the upper left feeding line 4. Alternatively, a transmission radio wave is applied to the antenna 1 from the power supply line 4. Hereinafter, a case where radio waves are transmitted from the antenna alone will be described, but the same applies to reception. The excitation element of the antenna unit 1 is formed by one unipole antenna 2,
A metal plate having a part of a spherical surface or the like like a bat umbrella is installed as a reflector 3 on the upper part. In this case, the reflector 3
As the size of the antenna becomes larger, the main directivity of the antenna can be directed to the lower part.

FIG. 2 shows the results of actual measurement (simulation). FIG. 2 illustrates the directional characteristics in the vertical plane (E plane) when the measurement frequency is 2 GHz (the same applies hereinafter). In this case, the reflector was a part of the upper part of a sphere having a diameter of 150 mm, and the diameter of the opening was 106 mm. FIG. 3 shows an antenna device when two antennas 1 of FIG. 1 are vertically arranged in an array. Each of the antennas 1 is held on the left column 5 in FIG. 3, and power is supplied to each of the antennas from the branching board. Upper and lower antenna spacing is 1
It was 50 mm (one wavelength).

FIG. 4 shows the results of actual measurement (simulation). It can be seen from the comparison with FIG. 2 that the leakage to the upper part is reduced and the directional characteristic in the vertical plane (E plane) is sharp downward. Next, FIG. 5 and FIG. 6 show the characteristics when the size of the reflector included in each of the two antennas shown in FIG. 3 vertically arranged in an array is increased.

FIG. 5 shows that the size of the reflector 3 is 300 mm in diameter.
6 shows the case where the diameter of the opening is 212 mm using a part of the upper part of the sphere, and FIG. 6 shows the case where the diameter of the opening is 260 mm using the same spherical shape. The effect of the size of the opening diameter appears in FIG. 5 and FIG.
The main beam is directed downward more than the example shown in FIG.
It can be seen that the directional characteristics in the sharp vertical plane (E plane) are exhibited.

Although the above description has been given of the case where the present invention is applied to a metal plate-shaped reflector, the reflector is not necessarily required to be plate-shaped. FIG. 7 shows an example in which a metal net 3-1 is used as the reflector 3. FIG. 8 shows an embodiment of a simple antenna in which a wire (ground wire) 3-2 extending radially from the base of the unipole antenna 2 is used as the reflector 3. FIG. 8 shows four wires, but the number of wires may be increased in order to prevent radio waves from leaking to the upper part.

In order to improve the weather resistance and impact resistance of each of the above-described antenna devices, the excitation element portion of the antenna or the entire antenna alone may be covered with a dielectric cover (radome). FIG. 9 shows an embodiment in which the unipole antenna 2 which is an excitation element portion of the antenna unit 1 shown in FIG. 1 is covered with a radome 7, and FIG. 10 shows the entire antenna unit 1 shown in FIG. This is an embodiment covered with.
FIG. 11 shows a state in which three antennas 1 shown in FIG. 1 are vertically arranged in an array and used in a practical system. The mutual distance between the individual antennas is about one wavelength. Each antenna unit is mounted on a support 5, and a feed circuit for the antenna device and wiring such as lighting are installed in the support.

In order to enhance the appearance of the antenna device, wiring such as lighting may be provided so that a lighting fixture can be installed even at the tip of the unipole antenna. For this purpose, a method is adopted in which a metal column constituting an excitation element of a unipole antenna is cylindrical and a wiring for lighting or the like is accommodated therein. FIG. 12 shows a case where a light is attached to the tip of the unipole antenna 2 shown in FIG. 9 through an optical fiber.
Further, each antenna alone is usually covered with a radome, but is not shown in the figure. The radome can be colored to match the surroundings as necessary.

Further, as an example of the unipole antenna, a whip antenna having similar electric characteristics can be used, and a metal plate having a part of a bat-like umbrella-shaped sphere or the like on the upper portion of the antenna or a similar shape is used. By installing a metal net, the same electrical characteristics as in the above embodiment can be realized.

[0019]

As described above, according to the base station antenna apparatus of the present invention, the radiation direction of radio waves from the base station, which is required in accordance with the reduction of the service area of the radio base station, is limited to only the service area. Therefore, the main beam direction of the antenna can be directed downward, and the leakage of radio waves to areas other than the service area can be reduced as much as possible. In other words, a single unipole antenna that is easy and inexpensive to manufacture is used, and in addition to this, the reflector installed on the side of the antenna excitation element in the conventional technology is installed in a bat-shaped umbrella above the antenna. It is now possible to easily direct the radiation direction of the radio wave downward even at a large angle that cannot be obtained with the tilt technology. Further, by installing a plurality of the above antennas vertically, it is possible to improve the overall gain of the antenna.

The size of the above bat-shaped umbrella reflector is such that the radius of the opening is about one-half wavelength and the size can be reduced. Further, this reflector may be a net-like shape other than a spherical metal plate, and for the sake of simplicity, the same effect can be obtained with a bat-umbrella-shaped radial wire.
As a result, the manufacturing cost of the antenna alone including the bat umbrella reflector can be reduced as compared with a conventional antenna having the same characteristics.

Furthermore, since wiring such as lighting can be installed outside the feed circuit for the antenna device in the column, it is possible to construct a base station antenna device which does not impair the beauty of the city. . Therefore, the present invention has the remarkable effects described above.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a basic example of an antenna device to which the present invention is applied.

FIG. 2 is a diagram showing a measurement example of electrical characteristics of the antenna device of FIG. 1;

FIG. 3 is a perspective view showing an example in which two antenna devices of FIG. 1 are vertically arranged in an array.

FIG. 4 is a diagram showing a measurement example of electrical characteristics of the antenna device shown in FIG. 3;

FIG. 5 is a diagram showing a measurement example of electric characteristics when the shape of the reflector of the antenna device of FIG. 3 is changed.

FIG. 6 is a diagram showing another measurement example of the electrical characteristics when the shape of the reflector of the antenna device of FIG. 3 is changed.

FIG. 7 is a perspective view showing another embodiment of the antenna device to which the present invention is applied.

FIG. 8 is a perspective view showing an embodiment of the antenna device to which the present invention is applied, which is different from the embodiment of FIG. 7;

FIG. 9 is a perspective view showing an embodiment in which a part of the antenna device of FIG. 1 is covered by a radome;

FIG. 10 is a perspective view showing an embodiment in which the entire antenna device of FIG. 1 is covered by a radome;

11 is a perspective view showing an example in which three antenna devices of FIG. 1 are vertically arranged in an array.

12 is a perspective view showing an example in which a light is installed at the tip of the antenna device shown in FIG. 9 through an optical fiber.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Antenna simple substance 2 Unipole antenna 3 Reflector 4 Feeding line 5 Prop 7 Radome

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01Q 21/08 H01Q 21/08 H04B 7/155 H04B 7/155 F term (Reference) 5J020 AA03 BA08 BC08 CA04 DA03 DA04 5J021 AA01 AA02 AA03 AA04 AA05 AA07 AA11 AB02 BA01 CA06 GA01 GA05 GA08 HA05 JA07 5J046 AB05 AB06 RA01 TA02 5J047 AB05 BB14 5K072 AA19 AA22 BB13 BB25 DD16 GG03 GG19

Claims (7)

[Claims] 1. A base station antenna device comprising: a unipole antenna installed perpendicular to the ground surface; and an antenna device having a umbrella-shaped reflector on an upper part thereof. 2. The base station antenna device according to claim 1, wherein the unipole antenna is a whip antenna. 3. The base station antenna device according to claim 1, wherein the reflector is formed of a metal plate, a metal net or a bat-shaped wire. 4. The base station antenna according to claim 1, wherein said one unipole antenna is covered with a cylindrical dielectric cover. apparatus. 5. The base station antenna device according to claim 1, wherein the antenna and the reflector are covered with a spherical dielectric cover. 6. The base station antenna device according to claim 1, wherein the antenna device is mounted on a support, and a feed circuit for the antenna device and a wiring other than the feed circuit are provided in the support. A base station antenna device housed therein. 7. The base station antenna device according to claim 6, wherein a plurality of the antenna devices are vertically arranged and attached to a support.