JPH0936654A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact antenna device which can improve its gain by using a grounding plate consisting of a conductor, the side face of a cylinder consisting of the conductor formed on the grounding plate and an array consisting of at least a single monopole element and making the cylinder serve as a reflector to the array of the monopole element. SOLUTION: An antenna device consists of a cylindrical reflector 1, a monopole Yagi antenna 2, a metallic grounding board 3, an exciter 6 consisting of a monopole element, and a wagveguide 7 consisting of a monopole element. The radii of both reflector 1 and board 3 are shown by S and R respectively. Thus a cylinder is used to the reflector of the antenna 2, so that the antenna adjustment can be facilitated. Furthermore, such an antenna is placed as a sector in its circumference direction. Thus the antenna has a reduced dead sector where the horizontal plane radiation pattern has a sector beam and the vertical plane radiation pattern has radiation between 30 deg. and 90 deg. and can be suitably applied to a radio LAN.

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 in particular, has a directivity of a cosecant square beam on a vertical plane and a fan beam on a horizontal plane, and has a high gain. The present invention relates to an antenna device for a small wireless LAN terminal, characterized in that an antenna capable of suppressing reflected waves is realized by a small and light antenna whose antenna height is suppressed.

[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 in which a metal ground plane as shown in FIG. 7 is divided into a plurality of sectors and a three-dimensional corner reflector antenna having a sector beam is installed in each sector is considered.

FIG. 7A is a schematic view, and FIG. 7B is a top view (X).
(Y plane) and (c) are side views (XZ plane). In FIG. 7, 6 is an exciter, 8 is a corner reflector antenna, 3 is a metal base plate, 4 is an antenna changeover switch, 9 is a corner reflector height Hr, 10 is a corner length lr of the corner reflector, and 12 is radiation directivity. , X, Y, and Z are orthogonal coordinates, and θ and φ are spherical coordinates. FIG. 7 shows an example when the number of sectors is 12, and the antenna devices in each sector are 3 on the metal ground plane and 2 on both sides of the exciter.
The three reflectors and 13 reflectors operate as a three-dimensional corner reflector antenna. 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, the value of θ is 0 for vertical in-plane radiation directivity.
The gain is high in the range from 90 ° to 90 °, and the radiation in other ranges is close to null. Regarding the radiation directivity in the horizontal plane, side lobes and back lobes are small, and the beam width is 360 ° in the number of sectors. A value that is divided by is required. The gain of the antenna having such a structure is determined by the antenna aperture area at the end of the corner reflector, which is defined by the distance between the reflectors and the height of the reflector. Therefore, the corner angle for the 30 ° beam is 30 °
In order to obtain a high gain with a corner reflector of 20 ° or a corner reflector for a 20 ° beam with a corner angle of 20 °, it is necessary to make the height and length of the reflector very large. It was difficult. Further, if the corner length of the corner reflector formed of a metal plate is increased, not only the size cannot be reduced, but also the weight becomes heavy.

On the other hand, in the conventional monopole Yagi antenna, the reflector is made of a linear element (Ohm Company, Antenna Engineering Handbook, p. 117). When such an antenna is used in a high frequency band exceeding 20 GHz, one wavelength is shortened to 15 mm or less, and therefore there is a drawback that a slight manufacturing error of the structure has a great influence on antenna characteristics such as directivity. Further, in the case of using the conventional linear element, the reflector must be close to the radiating element in order to realize an antenna with a small beam width and a high gain. On the other hand, when the reflection plate is brought close to the radiating element, it is difficult to achieve impedance matching at 50Ω.

[0006]

As described above, in the conventional three-dimensional corner reflector antenna, a null is generated just above the exciter, which causes the D / U ratio to deteriorate, resulting in 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 to solve the above problems, and is concerned with the miniaturization of an antenna.

SUMMARY OF THE INVENTION The present invention has been made to improve the above-mentioned drawbacks, and an object of the present invention is to provide an antenna device having a small size and a high gain.

[0008]

According to the present invention, the above problems can be solved by the means described in the claims. That is, the present invention is an antenna device including a ground plane made of a conductor and a conductor cylinder or a side surface of a polygonal prism formed on the ground plane, and an array made of one or more monopole elements. Is an antenna device in which the monopole element serves as a reflector.

No conventional monopole antenna with a ground plane has a cylindrical or polygonal prism type reflector.

Further, according to the present invention, the ground plane is divided into a plurality of sectors centered on the central portion of the ground plane or in the vicinity of the central portion, and an array of one or more monopole elements is provided for each sector. The antenna device is characterized in that one cylinder used as a reflector of an array of pole elements is installed so that the center of sector division becomes the center of the cylinder.

The reflector of the conventional sector beam antenna uses a corner reflector having a corner angle of 360 ° divided by the number of sectors or a value smaller than this, which is narrow using only a cylinder or a polygonal prism. There was no antenna with high beam width and high gain.

Further, the present invention is characterized in that a plurality of partition plates are installed between the monopole elements which are installed on the ground plane. By providing the partition plate, it is possible to suppress reflection from an adjacent element.

According to the present invention, the monopole Yagi, which operates as a surface wave antenna, originally has directivity,
Since the reflector is cylindrical, a reflector with a large opening is placed on this. As a result, this antenna can realize a sharp beam and high gain as compared with the case where a corner reflector antenna is used, with the same ground plane radius and the same height of the reflector. Since the monopole antenna with a cylindrical reflector has a cylindrical reflector, the area for reflecting radio waves is larger than when a linear element is used as the reflector, and as a result, an antenna that does not affect a slight manufacturing error can be realized. When a cylindrical reflector is used, the directivity can be sharply reduced to some extent even if the reflector and the radiating element are separated from each other, so that impedance matching can be easily achieved. By installing the partition plate, it is possible to obtain the effect of reducing the side lobe in the directivity in the conical plane.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of an antenna device of the present invention, 1 is a cylindrical reflector, 2 is a monopole Yagi array, 3 is a metal base plate, 6 is an exciter using a monopole element, and 7 Is a director with a monopole element. S is the radius of the cylindrical reflector, and R is the radius of the ground plane. The one cylindrical reflector may be realized as a polygon.

FIG. 2 shows a second embodiment of the antenna device of the present invention, in which 1 is a cylindrical reflector, 2 is a monopole Yagi array, and 3 is a metal base plate. The one cylindrical reflector may be realized as a polygon. Further, the antenna changeover switch can be housed inside the cylindrical reflector, and the monopole Yagi array can be changed over and used.

FIG. 3 shows a third embodiment of the present invention, in which 1 is a cylindrical reflector, 2 is a monopole Yagi array, 3 is a metal base plate, and 5 is a partition plate.

FIG. 4 shows an example in which the characteristics of the second and third embodiments of the present invention are calculated using the method of moments. FIG. 4 shows the gain values when the array length is used as a parameter in comparison between the case of a three-dimensional corner reflector and the case of a monopole with a cylindrical reflector. In FIG. 4, (a)
2B shows the results in the case of the monopole with a cylindrical reflector shown in FIG. 2, and FIG. 7B shows the case of the monopole with the cylindrical reflector in which the partition plate shown in FIG. 3 is installed. FIG.
The values indicated by the broken lines are the gain characteristics of the conventional corner reflector shown in FIG. Here, it is assumed that the radius S of the cylinder is 2 wavelengths, the height of the cylinder is 2/3 wavelengths, the corner length is 0.5 wavelengths, and the size of the metal base plate is infinite. Here, the array length is the minimum required size of the ground plate, that is, the minimum required ground plate radius R.
Assuming that is the sum of the array length and the radius of the cylinder, the antenna with the structure shown in FIG. 2 in which the cylindrical reflector is installed and the antenna with the partition plate in FIG. It can be seen that the gain is higher than in the case of the reflector alone.

FIG. 5 shows the radiation directivity of the antenna of the second embodiment of the present invention by the calculated value using the moment method. Here, the radius of the cylindrical reflector is 2 wavelengths, the height of the cylindrical reflector is 0.67 wavelengths, the radius of the circular metal base plate is 6 wavelengths, the number of elements of the monopole array is 12, and the element spacing is 0.
It has two wavelengths. FIG. 5 (a) shows the radiation directivity in the horizontal plane,
FIG. 5 (b) shows vertical in-plane radiation directivity. The horizontal plane has a fan shape, and the vertical plane has an ideal pattern shape from θ = 30 ° to 90 ° as a sector antenna used for a wireless LAN with little dead area.

FIG. 6 shows a partition plate according to the third embodiment of the present invention,
The radiation directivity of the monopole Yagi antenna with a cylindrical reflector is shown by the measured value. FIG. 6A shows the case without the partition plate, and FIG. 6B shows the case with the partition plate of the present invention. Here, the radius of the cylindrical reflector is 2 wavelengths, the height of the cylindrical reflector is 0.67 wavelengths, the radius of the circular metal base plate is 5 wavelengths, the number of elements of the monopole array is 9, and the element spacing is 0.2 wavelengths. There is. It can be seen that the side lobes and back lobes, which are unnecessary radiation, can be reduced by installing the partition plate.

[0020]

As described above, in the antenna device of the present invention, the antenna can be adjusted more easily than before by using the cylinder for the reflector of the monopole Yagi antenna. Furthermore, by arranging this antenna in sectors in the circumferential direction, the antenna has a fan-shaped directivity in the horizontal plane, and the directivity in the vertical plane radiates from θ = 30 ° to 90 °. A suitable antenna can be obtained.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a second embodiment of the antenna device of the present invention.

FIG. 3 is a diagram showing a third embodiment of the antenna device of the present invention.

FIG. 4 is a diagram showing an effect of the present invention, showing antenna characteristics by analysis using the method of moments.

FIG. 5 is a diagram showing the directivity of the antenna device according to the second embodiment of the present invention.

FIG. 6 is a diagram showing the directivity of an antenna device according to a third embodiment of the present invention.

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

[Explanation of symbols]

 lr Height of cylindrical reflector R Length of metal base plate X, Y, Z Cartesian coordinate θ, φ Spherical coordinate 1 Cylindrical reflector 2 Monopole Yagi antenna 3 Metal base plate 4 Antenna changeover switch 5 Partition plate 6 # 1, Exciter 7 # 2- # n, Waveguide 8 Corner reflector antenna 9 Corner reflector height Hr 10 Corner length lr 12 Radiation directivity

Claims (6)

[Claims] 1. A ground plane made of a conductor, a side surface of a cylinder made of a conductor formed on the ground plane, and an array of at least one monopole element, wherein the cylinder is arranged with respect to the array of monopole elements. An antenna device characterized by being configured as a reflector. 2. The antenna device according to claim 1, wherein the array includes an exciter having a monopole element and a director having at least one monopole element. 3. The antenna device according to claim 1, wherein one cylinder is provided near the center of the base plate, and an array of the plurality of monopole elements is provided so that the cylinder serves as a common reflector. An antenna device characterized by the above. 4. The antenna device according to claim 3,
An antenna device, wherein an antenna changeover switch configured to switch and use an array of the plurality of monopole elements is housed in the cylinder. 5. The antenna device according to claim 3, wherein a partition plate is provided between the arrays of the plurality of monopole elements. 6. The antenna device according to claim 1, wherein the cylinder is a polygonal prism.