JPH098546A - Antenna system - Google Patents

Abstract

PURPOSE: To provide the antenna system with a small back lobe without changing the size of antenna, causing a null point just above an exciting element and losing the shape of the main lobe. CONSTITUTION: In a corner reflector antenna having at least a ground plate 3 whose surface is made of a conductor, an exciting element 1 provided on the ground plate, and at least one reflecting plate 2, a rear reflecting plate 6 provided behind a main beam direction of the exciting element is provided at a tilt from a vertical direction of the ground plate 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device for high speed wireless data communication such as a wireless LAN, and more particularly to a null point generated in the antenna directivity without changing the shape of the main lobe of the antenna directivity. The present invention relates to a small-sized antenna device that eliminates a dead area caused by nulls and is suitable as an antenna for a base station device and a terminal device.

[0002]

2. Description of the Related Art An antenna for a base station device used for a local wireless LAN or the like is installed on an indoor ceiling or the like, and an antenna for a terminal device is installed on a desk or a personal computer or a workstation on the desk. .

Transmission speed of 10 Mb, such as wireless LAN
For high-speed wireless communication exceeding ps, an antenna with sharpened directivity and high gain is required. On the other hand, it is desirable that the terminal device can direct the beam in all directions of 360 ° in the horizontal plane so that the base station can receive radio waves in any direction. As an antenna that realizes this,
An antenna has been considered in which a metal ground plane is divided into a plurality of sectors and a three-dimensional corner reflector antenna having a sector beam is installed in each sector.

FIG. 7 shows an example of a conventional switchover type sector beam antenna. Fig.7 (a) is an outline view,
(B) is a top view (XY plane), (c) is a side view (XZ plane)
It is. In FIG. 7, 1 is an excitation element, 2 is a reflector, and 3 is
Is a metal base plate, 4 is an antenna changeover switch, 5 is the height Hr of a reflector, 6 is a reflector behind the excitation element 1, 12 is radiation directivity, X, Y and Z are orthogonal coordinates, and θ and φ are spherical surfaces. The coordinates are shown. FIG. 7 shows an example in which the number of sectors is 12, and the antenna device in each sector is a three-dimensional corner reflector antenna with a metal base plate 3 and reflectors 2 and rear reflectors 6 on both sides of the excitation element. Operate. This antenna searches for the direction in which the radio wave arrives at the reception level when first communicating, and switches to the antenna of the sector used by the antenna changeover switch. In such an antenna, as for the radiation in the vertical plane, the gain is high in the range where the value of θ is 0 ° or more and 90 ° or less, and the radiation in the other range is close to null, and the radiation directivity in the horizontal plane. As for, the side lobe and the back lobe are small and the beam width is required to be 360 ° divided by the number of sectors.

FIG. 8 shows the structure of a conventional three-dimensional corner reflector antenna device in one sector. In FIG. 8, 1 is an excitation element, 2 is a reflection plate, 3 is a metal base plate, and 6
Is a rear reflector behind the exciting element, and 7 is a corner angle α, X, Y, Z formed by the two reflectors in rectangular coordinates. R is the length of the reflector 2.

FIG. 9 shows an example of calculation of the directivity in the vertical plane of the antenna of FIG. 8 using the method of moments. In FIG. 9, θ is a spherical coordinate. FIG. 9 shows that the height of the excitation element shown in FIG. 8 is a quarter wavelength, the length R of the reflection plate is about one wavelength, the corner angle α is 30 °, and the height Hr of the reflection plate forming the corner reflector is Hr. Shows a vertical in-plane radiation directivity from θ = −90 ° to θ = 90 ° when is 0.4 wavelength. Here, the metal ground plane is assumed to be infinite to simplify the calculation.

In FIG. 9, 8 is a main lobe, 9 is a back side lobe, and 10 is a back lobe. 11
Indicates that the gain is 0 dB in the range where the value of θ is 0 ° or more and 90 ° or less.
It is an angle η at which i becomes a dead zone. Both the back lobe of 9 and the back lobe of 10 are lower by 15 dB than the main lobe of 8, but it is desirable that this value be lower than the main lobe by 29 dB or more. Here, the vertical in-plane radiation directivity 3 dB beam width is 90
°.

FIG. 10 shows an example of calculation of the directivity in the horizontal plane of the antenna of FIG. 8 using the method of moments. In FIG. 10, φ is a spherical coordinate. In FIG. 10, reference numeral 18 is a side lobe having directivity in the horizontal plane. Here, the antenna structure parameter has the same value as in FIG. 9, and the 3 dB beam width is 49 ° at this time.

FIG. 11 shows an example in which a monopole antenna with a metal ground plane is used as a base station antenna, and the sector beam antenna with a metal ground plane shown in FIG. 7 is used as a terminal antenna. In FIG. 11, reference numerals 13, 14, 15, and 16 are terminal antennas using a switchable sector beam antenna, and 17 is a base station antenna using a monopole antenna with a metal ground plane. In FIG. 11, 1
The terminal No. 3 has a large transmitting antenna gain and a large receiving antenna gain. On the other hand, the 14 terminals have small transmission antenna gain and reception antenna gain in direct waves, and large transmission antenna gain and reception antenna gain in interference waves. Therefore, there is a drawback that D / U deterioration increases.

[0010]

As described above, the conventional three-dimensional corner reflector antenna has a drawback in that a null is generated just above the exciting element, which deteriorates the D / U ratio and causes a dead zone. there were. Further, in order to suppress side lobes and back lobes using a conventional corner reflector, there is only means for increasing the height of the reflection plate or the length of the reflection plate to increase the aperture area, and therefore the antenna can be made small. There was a drawback that I could not. Further, there is a method of using a dielectric as a means for expanding the apparent aperture area without changing the size of the antenna, but in this case, there are drawbacks such as loss due to the dielectric and side lobes.

The present invention has been made in order to solve the above problems, and realizes an antenna device in which nulls do not occur directly above the excitation element without compromising the shape of the main lobe, and the antenna device The purpose is to reduce the back lobe without changing the size.

[0012]

Means for Solving the Problems The features of the present invention for achieving the above-mentioned object are to provide a metal base plate, an excitation element standing on the metal base plate, and one or more reflections so as to surround the excitation element. An antenna for mounting a plate, wherein the reflector is tilted.

An antenna device comprising a plurality of the antennas, an antenna changeover switch for switching the plurality of antennas, and a metal base plate, wherein the antenna changeover switch is arranged at the center of the metal base plate and is reflected. It is an antenna device characterized in that a plate is arranged so as to surround an antenna changeover switch.

The conventional corner reflector antenna and the three-dimensional corner reflector antenna are different from each other in that the rear reflector, which is behind the exciting element with respect to the direction of the radio wave, is inclined.

[0015]

With the structure as described above, radiation from the excitation element is reflected by the inclined reflecting plate and acts so as to eliminate the null point generated on the excitation element, eliminating dead spots. . Also, by tilting the reflector behind the excitation element toward the excitation element, without increasing the height of the antenna device, the horizontal plane directivity, without changing the beam width of the vertical in-plane directivity, Also, the back lobe radiation is -20 dB without causing unnecessary side lobes.
It can be reduced to i.

Further, because of the structure as described above, the space created by tilting the rear reflector can be used as a place for installing a switch and a circuit for switching the antenna, thus making the antenna device compact. It becomes possible.

[0017]

1 is a first embodiment of an antenna device of the present invention, showing the structure of a three-dimensional corner reflector in which a reflecting plate behind an exciting element is tilted. Figure 1 (a) is an overview diagram,
(B) is a side view. In FIG. 1, 1 is an exciting element,
2 is a reflection plate, 3 is a metal base plate, 6 is a reflection plate behind the excitation element 1 installed at an angle, 7 is a corner reflector angle α composed of two reflection plates, and 19 is a rear reflection plate. The angles β, X, Y and Z indicating the inclination are orthogonal coordinates.

FIG. 2 shows an example of calculation of the directivity in the vertical plane of the antenna of FIG. 1 using the method of moments. In FIG. 2, θ is a spherical coordinate. FIG. 2 shows a value when the inclination angle β of the rear reflector is 27 ° and other structural parameters are the same as those in FIG. 7 of the prior art, that is, the height of the excitation element shown in FIG. 1 is 1/4. Θ = −90 ° to θ = 90 when the wavelength and the length R of the reflector are about 1 wavelength, the angle α of the corner is 30 °, and the height Hr of the reflector forming the corner reflector is 0.4 wavelength. It shows a vertical radiation pattern of °. Here, the metal ground plane is assumed to be infinite to simplify the calculation.

In FIG. 2, 8 is a main lobe which forms a main beam, and 9 is a back side lobe (side lobe appearing at θ <0). This antenna has almost no 10 back lobes shown in FIG. 2 of the prior art. Also, the backside lobe of 9 is about 10 dB smaller than that of the prior art FIG. On the other hand, the 3 dB beam width in the main lobe of 8 is 93 °, which is larger than when the rear reflector 6 is not tilted.

FIG. 3 shows the radiation directivity in the horizontal plane of the antenna of FIG. The back lobe radiation is eliminated as compared with FIG. 10 shown in the related art. Here, the 3 dB beam width is 47 °, which is almost the same as the case of FIG. The side lobes are also small.

As described above, it can be understood that by tilting the rear reflector of the three-dimensional corner reflector by 27 °, the dead area of the radiation directivity in the vertical plane can be eliminated and the back lobe can be reduced. In the present invention, the corner angle α is 1
This effect can be obtained even when there is only one reflecting plate at 80 °. Further, the same effect can be obtained when a corner reflector having a corner angle α of more than 180 ° is used.

FIG. 4 shows the characteristics of the present antenna with the tilt angle β of the back reflector 6 shown in FIG. 1 as a parameter. FIG.
(A) shows the level of the radiation directivity in the vertical plane when the value of θ in FIG. 1 is 0 °. Do not tilt the reflector, β is 0
It can be confirmed that the gain is small and the null level disappears when the reflector is tilted, although the gain is small at -10 dBi or less near 0 °.

FIG. 4B shows the level of the back lobe 10. The angle β of inclination of the reflector is 27 °, and the radiation to the back lobe is the smallest. Further, in the range of β of 10 ° to 40 °, the back lobe level is lowered by 3 dB or more as compared with the conventional case of β of 0 °. FIG.
When β is made negative in (b), the back lobe becomes large, but it can be seen from FIG. 4 (a) that the null can be eliminated, so that it is effective when the back lobe is not a problem. is there.

FIG. 4C shows the value of the beam width of 3 dB on the horizontal plane,
FIG. 4D shows the value of the beam width of 3 dB on the vertical surface.
It can be confirmed that when β is a positive value of 10 ° or more, that is, when the back reflector is tilted toward the excitation element, there is little change in the beam width value in the horizontal plane and the vertical plane.
FIG. 4 (e) shows the change in gain, where β is 10 ° to 4 °.
The value is almost constant in the range of 0 °.

FIG. 5 shows a second embodiment of the present invention, which shows an antenna device in which an array of three-dimensional corner reflectors in which the rear reflector of the excitation element is tilted is arranged and an antenna changeover switch 4 is provided in the generated space. ing. In the present invention,
Since the space surrounded by the tilted back reflector can be effectively used, it is possible to realize a small antenna device without using a small and expensive switch.

FIG. 6 shows a third embodiment of the present invention, which is an antenna device in which a director 20 is arranged in front of the excitation element 1. Although the director 20 is not connected to the antenna changeover switch 4, it is excited by the radio wave radiated from the excitation element 1 and functions to give a good directivity. It goes without saying that the effects of the present invention are also effective when a director is used for one sector antenna in this way. Reference numeral 20 in FIG. 6 is a director.

[0027]

As described above, in the antenna device of the present invention, the rear reflecting plate is tilted with respect to the exciting element. The level directly above the antenna can be increased without increasing the size of the antenna. Furthermore, by tilting the rear reflector toward the excitation element, the level directly above the antenna can be increased without increasing the size of the antenna, and at the same time, without generating side lobes,
The back lobe can be reduced without changing the beam width in the main lobe on the horizontal plane or the vertical plane as compared with the conventional case in which the reflector is not tilted. Furthermore, by arranging this antenna in an array on a metal base plate that is divided into sectors, a sector antenna changeover switch is installed in the space created by tilting the reflector, and a small antenna device with high space utilization efficiency can be realized. It will be possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a first embodiment of the present invention. (A)
Is a schematic view and (b) is a lateral view.

FIG. 2 is an example of analysis using the method of moments of the first embodiment of the antenna device of the present invention, which shows the radiation directivity in the vertical plane.

FIG. 3 is an analysis example using the method of moments of the first embodiment of the antenna device of the present invention, showing the radiation directivity in the horizontal plane.

FIG. 4 is a diagram showing the effect of the present invention, showing antenna characteristics when the tilt angle β of the rear reflector behind the excitation element is used as a parameter by analysis using the method of moments. (A) shows the gain at θ = 0 °, which is a dead spot in the conventional antenna device. (B) shows the radiation level of the back lobe. (C) has shown the 3 dB beam width of directivity in a horizontal plane. (D) shows a vertical in-plane directivity 3 dB beam width. (E) shows the gain.

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

FIG. 6 is a diagram showing a third embodiment of the present invention.

FIG. 7 is a diagram showing a first conventional antenna device.

FIG. 8 is a diagram showing a second conventional antenna device.

FIG. 9 is a diagram showing vertical in-plane directivity of a conventional antenna device as an analysis value by a method of moments.

FIG. 10 is a diagram showing directivity in a horizontal plane of a conventional antenna device as an analysis value by a method of moments.

11 is a diagram showing an example in which a monopole antenna with a metal ground plane is used as a base station antenna, and a sector beam antenna with a metal ground plane shown in FIG. 7 is used as a terminal antenna.

[Explanation of symbols]

 Hr Reflector height R Reflector length X, Y, Z Cartesian coordinates θ, φ Spherical coordinates 1 Excitation element 2 Reflector 3 Metal base plate 4 Antenna changeover switch 5 Reflector height Hr 6 Back reflector 7 α , Corner angle of corner reflector 8 Main lobe 9 Backside lobe 10 Backlobe 11 Dead zone η 12 Radiation directivity 13 Terminal sector beam antenna 14 Terminal sector beam antenna 15 Terminal sector beam antenna 16 Terminal sector beam Antenna 17 Monopole antenna with metal ground plane 18 Sidelobe (directional in horizontal plane) 19 β, Back reflector tilt angle 20 Waveguide

Claims (6)

[Claims] 1. A ground plane of which at least a surface is a conductor, an excitation element provided on the ground plane, and at least one.
In a three-dimensional corner reflector antenna having a small number of co-surfaced conductor reflectors, a rear reflector provided behind the main beam direction with respect to the excitation element is provided tilted from a direction perpendicular to the ground plane. An antenna device characterized by. 2. The antenna device according to claim 1, wherein the rear reflector is installed so as to be tilted in a range of 10 ° to 40 ° from the vertical direction of the base plate toward the excitation element. 3. An antenna device comprising a plurality of the antenna devices according to claim 1 or 2, and an antenna changeover switch for selecting one of the plurality of antenna devices. 4. The antenna device according to claim 3,
An antenna device, characterized in that a plurality of adjacent antenna devices have a common reflector. 5. The antenna device according to any one of claims 3 to 4, wherein a plurality of configured antenna devices are radially arranged in a circle, and the antenna changeover switch is arranged in the center of a circle. An antenna device, wherein the rear reflector is arranged so as to surround the antenna changeover switch. 6. The antenna device according to claim 1, further comprising a director provided on the main plate surrounded by the corner reflector.