JPH0983237A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the antenna system suitable for a base station antenna for a mobile communication system in which omnidirectivity of a horizontal plane and a low radiation angle of a vertical plane are realized. SOLUTION: An opening angle of 90 deg. is provided between 1st and 2nd loop antennas 42, 43 and 3rd and 4th loop antennas 44, 45 connecting respectively to both ends of a parallel feeder 41 by taking notice of it that the horizontal plane directivity of a twin loop antenna has figure 8 shaped directivity and the antenna has a low radiation angle. The horizontal plane directivity SH4 of the system 4 is made omnidirectional by combining orthogonally the figure 8 shaped directivity of the 1st and 2nd loop antennas 42, 43 and the figure 8 shaped directivity of the 3rd and 4th loop antennas 44, 45 in air so as to realize the antenna system with a low radiation angle.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device used for a base station side antenna of a mobile communication system, for example, which is omnidirectional on a horizontal plane and has a low radiation angle on a vertical plane.

[0002]

2. Description of the Related Art As is well known, the characteristics of a transmitting / receiving antenna in a base station of a mobile communication system are such that the antenna ground height on the mobile side of interest is low, so that the radiation angle of the radio wave radiation on the vertical plane is low. In addition, in order to secure the service area in all directions of 360 degrees, the horizontal plane directivity is required to be omnidirectional.

The suitability of the conventional antenna for this requirement will be described.

4A and 4B show the horizontal plane directivity and the vertical plane directivity of the vertical antenna 1, respectively. As shown in FIG. 4A, this vertical antenna 1 has the advantage that the horizontal plane directivity SH1 is non-directional and the structure is simple. However, as shown in FIG. 4 (b), since the radio wave radiation angle of the vertical plane directivity SV1 is high and unnecessary radio wave radiation is present in the diagonally upward direction of the vertical plane, it is necessary to use the radiation angle for use in mobile communication. A large amount of transmission power is required to secure a service area equivalent to that of a low antenna.

FIG. 5 shows the structure of an omnidirectional antenna device using a 1/2 wavelength dipole antenna with a reflector. Reference numerals 21 to 24 are 1/2 wavelength dipole antennas with a reflector, respectively. Directivity is directed to N (north), E (east), S (south), W (west). Each of the antennas 21 to 24 is connected via a branch feeder 271 to 274 to a 4-distributor 26 that divides the power supplied from the main feeder 25 into four.

The horizontal plane directivity and the vertical plane directivity of the antenna device 2 are shown in FIGS. 6 (a) and 6 (b), respectively. That is, in this antenna device 2, the radio wave radiation angle of the vertical plane directivity can be freely set by installing the antenna downward.

However, since the horizontal plane directivity of the antenna alone is unidirectional, the radiation direction is shifted by 90 degrees in the horizontal plane as a four-sided configuration, and the horizontal plane directivity of the four sided antennas is combined to make the horizontal plane non-directional. Need to get sex. Therefore, each of the four dipole antennas 21 to 24
A 4 divider 26 that distributes the transmission power to is required.

Generally, the power loss of the four distributors is usually about 1 dB or more, and about 20% of the transmission power is consumed by the distributor 25, which is equivalent to an antenna that does not require a distributor. In order to secure the above, a large amount of transmission power is still required.

FIGS. 7A and 7B show the horizontal plane directivity and the vertical plane directivity of the 4L twin loop antenna 3, respectively.

In this 4L twin loop antenna 3, one loop antenna resonates at one wavelength, and the horizontal plane directivity SH3 thereof shows an 8-shaped directivity as shown in FIG. 7 (a). As shown in FIG. 7B, the vertical plane directivity SV3 has a characteristic equivalent to that of a vertical eight-stage stack of 1 / 2λ dipole antennas, and is characterized in that the radiation angle of a vertical plane directivity radio wave is extremely low.

Further, since the twin loop antenna 3 can feed power to a plurality of loop antennas at the same time without using a distributor, it is possible to use a distributor such as the antenna device 2 of the 1/2 wavelength dipole antenna with a reflector shown in FIG. It is a well-known fact that there is no loss. However, as shown in FIG. 7A, the twin-loop antenna has a figure-8 directivity on the horizontal plane, and is therefore not suitable for use as a base station antenna for mobile communication that requires omnidirectionality. .

Here, as the prior art, the actual Kaihei 2-86 is used.
No. 208 (hereinafter referred to as "prior art 1") discloses at least two one-wavelength loop antennas connected to parallel feed lines at different angles, and a feed point for feeding one wavelength loop antenna from the center of the parallel feed lines. With the use of a distributor, a branch feeder, etc., it is possible to easily obtain a multi-directional directivity, a mechanically simple and high-gain wideband "twin-loop receiving antenna for UHF television. Is disclosed.

Further, in Japanese Patent Laid-Open No. 59-44107 (hereinafter referred to as prior art 2), two 8-character directional antennas and one omnidirectional antenna which are arranged orthogonally to each other are used. Discloses a "cardioid directional antenna capable of rotating in the beam direction" which enables the beam to be electrically rotated in all directions without using a drive mechanism and is downsized.

Further, a beam direction variable antenna is realized with a simple structure by combining two 8-shaped directional antennas orthogonal to each other in Japanese Patent Laid-Open No. 58-83401 (hereinafter referred to as prior art 3). An "antenna" is disclosed.

[0015]

As described above, in the conventional antenna device, the radiation angle of the vertical plane directivity is high, and the distributor is required to obtain the non-directional horizontal plane directivity. There is a problem that the transmission power cannot be effectively used due to the radiation angle and the loss of the distributor.

An object of the present invention is to solve the above problems and to realize an omnidirectionality in a horizontal plane and a low radiation angle in a vertical plane, and to provide an antenna device suitable as a base station antenna for a mobile communication system. To do.

Here, the invention of the prior art 1 is the same as the present invention in that a twin loop antenna is used, but there is no specific configuration for realizing omnidirectionality in the horizontal plane and low radiation angle in the vertical plane. , Which is different from the technical idea of the present invention.

The invention of the prior art 2 is capable of electrically rotating the beam in all directions without using a drive mechanism, and does not realize the non-directionality of the horizontal plane as in the present invention.

The invention of Prior Art 3 is an antenna for varying the beam direction, and there is nothing about the technical idea of the present invention which realizes omnidirectionality in a horizontal plane and low radiation angle in a vertical plane by using a twin loop antenna. Not disclosed.

[0020]

An antenna device of the present invention for solving the above problems is connected to one end of a parallel feed line,
First and second loop antennas having loop lengths formed so as to resonate at one wavelength of transmission / reception wavelengths, and loop lengths connected to the other ends of the parallel feed lines so as to resonate at one wavelength of transmission / reception wavelengths. Is formed, and an opening angle of 90 degrees is provided between the first, second and third and fourth loop antennas.

That is, considering that the horizontal plane directivity of the twin loop antenna has a figure 8 directivity and the radiation angle is low, 90 degrees are provided between the first, second, third, and fourth loop antennas. By setting the opening angle of 8 and synthesizing the figure 8 directivity of the first and second loop antennas and the figure 8 directivity of the third and fourth loop antennas in the air, the horizontal plane directivity can be improved. The antenna device is omnidirectional and has a low radiation angle.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a block diagram of a standard 4L twin loop antenna. As can be seen from FIG. 2, first and second loop antennas 42 and 43 tuned to the wavelength of the transmission / reception frequency are connected to one end of the parallel feed line 41. Further, third and fourth loop antennas 44 and 45, which are also tuned to the wavelength of the transmission / reception frequency, are connected to the other end of the parallel feeder 41.

The feed configuration of this twin loop antenna is shown in FIG.
As shown in, the feeder 47 feeds power to the parallel feed line 41 via the impedance matching device 46.

In such a standard 4L twin loop antenna, the first loop antenna 42, the second loop antenna 43, the third loop antenna 44, and the fourth loop antenna 4 are used.
5 has an angle between the loop antennas of 0 degrees,
The horizontal plane directivity shows the figure 8 directivity as shown in FIG.

Therefore, the antenna device of the present invention that can be used for mobile communication is constructed as shown in FIG. 1 (a). That is, this antenna device utilizes the characteristics of the twin loop antenna, and the first and second loop antennas 4
2 and 43 have an opening angle of +45 degrees with respect to the parallel power supply line 41. Further, the other end of the parallel feed line 41 is connected to third and fourth loop antennas 44 and 45 which are also tuned to the wavelength of the transmission / reception frequency, and an opening angle of −45 degrees with respect to the parallel feed line 41. To have.

According to the above structure, an opening angle of 90 degrees is provided between the first and second loop antennas 42 and 43 and the third and fourth loop antennas 44 and 45 with the parallel feed line 41 interposed therebetween. Therefore, the first and second loop antennas 4
The 8-shaped directivity of 2 and 43 and the 8-shaped directivity of the third and fourth loop antennas 44 and 45 are orthogonal to each other. In this way, each loop antenna
By synthesizing the character directivity in the air, it is possible to realize the non-directional horizontal plane SH4 as shown in FIG. 4B. Of course, due to the characteristics of the twin loop antenna, the radiation angle of the radio wave radiation generated by the vertical plane directivity SV4 is sufficiently low.

Therefore, the antenna device having the above-described structure has a non-directional horizontal plane directivity and a sufficiently low radiation angle, which makes it extremely suitable as an antenna on the base station side used for mobile communication. .

[0029]

As described above, according to the present invention, the four loop antennas resonated at the transmission / reception frequency are connected to each other by 90 degrees.
Since the horizontal plane directivities of the respective loop antennas are orthogonally combined in the air to be omnidirectional by having a configuration with an opening angle of degrees, it is required as a base station antenna for mobile communication, It is possible to provide an antenna device that can realize omnidirectionality on a horizontal plane and a low radiation angle on a vertical plane, eliminate distribution loss by eliminating a distributor, and effectively radiate power. it can.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an antenna device according to an embodiment of the present invention and directivity of a vertical plane and a horizontal plane.

FIG. 2 is a diagram showing a configuration of a twin loop antenna used in the present invention.

FIG. 3 is a diagram showing a power feeding configuration of the twin loop antenna shown in FIG.

FIG. 4 is a diagram showing a horizontal plane directivity and a vertical plane directivity in a vertical antenna.

FIG. 5 is a diagram showing a configuration of an antenna device using a half-wave dipole antenna with a reflector.

6 is a diagram showing a horizontal plane directivity and a vertical plane directivity in the antenna device shown in FIG.

FIG. 7 is a diagram showing a horizontal plane directivity and a vertical plane directivity of an antenna device using a twin loop antenna.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Vertical system antenna 2 Antenna apparatus with 1/2 wavelength dipole antenna with reflector 21-24 24 1/2 wavelength dipole antenna with reflector 25 Main feeder 26 4 Distributor 271-274 Branch feeder 3 Twin loop antenna 4 Antenna apparatus 41 Parallel feed line 42 first loop antenna 43 second loop antenna 44 third loop antenna 45 fourth loop antenna 46 impedance matching device 47 feeder

Claims (2)

[Claims] 1. A first and a second loop antenna connected to one end of a parallel feed line and having a loop length so as to resonate with one wavelength of a transmission / reception wavelength, and connected to the other end of the parallel feed line. And a third and fourth loop antenna having a loop length formed so as to resonate with one wavelength of the transmission / reception wavelength, and 90 between the first, second, third, and fourth loop antennas. An antenna device having an opening angle of 4 degrees. 2. The first and second loop antennas have an opening angle of +45 degrees with respect to the parallel feed lines, and the third and fourth loop antennas have −45 with respect to the parallel feed lines. The antenna device according to claim 1, wherein the antenna device has an opening angle of 4 degrees.