JP3259211B2 - Antenna device - Google Patents

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 method for eliminating a null point occurring in antenna directivity without substantially changing the shape of a main lobe of antenna directivity. The present invention relates to a small-sized antenna device suitable for a base station device and a terminal device antenna that eliminates a dead zone caused by null by eliminating the antenna device.

[0002]

2. Description of the Related Art An antenna for a base station device used for a private 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 workstation on the desk. .

[0003] The transmission speed is 10 Mb such as a wireless LAN.
In high-speed wireless communication such as exceeding ps, an antenna having a high directivity and a high gain is required. On the other hand, it is desirable that the terminal device be capable of directing 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 to achieve this,
An antenna in which a metal ground plane is divided into a plurality of sectors and a three-dimensional corner reflector antenna having a sector beam for each sector is provided.

FIG. 7 shows an example of a conventional switchable sector beam antenna. FIG. 7A is an overview diagram,
(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, 3
Is a metal ground plate, 4 is an antenna changeover switch, 5 is a 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 formed as a three-dimensional corner reflector antenna by three metal ground plates, reflectors 2 and rear reflectors 6 on both sides of the excitation element. Operate. The antenna performs an operation of first searching for a direction of arrival of a radio wave at a reception level when performing communication, and switching to an antenna of a sector to be used by an antenna switch. In such an antenna, the radiation directivity in the vertical plane is high when the value of θ is in the range of 0 ° or more and 90 ° or less, and the radiation in other ranges becomes close to null. As for, it is required that the side lobe and the back lobe are small and the beam width becomes a value obtained by dividing 360 ° by the number of sectors.

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

FIG. 9 shows a calculation example of the directivity in the vertical plane of the antenna of FIG. 8 using the moment method. In FIG. 9, θ is a spherical coordinate. FIG. 9 shows the height of the excitation element shown in FIG. 8 at a quarter wavelength, the length R of the reflector about 1 wavelength, the angle α of the corner of 30 °, and the height Hr of the reflector forming the corner reflector. Represents the radiation directivity in the vertical plane from θ = −90 ° to θ = 90 ° when is set to 0.4 wavelength. Here, the metal base plate is assumed to be infinity in order 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
Means that the gain is 0 dB when the value of θ is in the range of 0 ° to 90 °.
This is the angle η that becomes i, and here is the dead zone. The back lobe 9 and the back lobe 10 are both about 15 dB lower than the main lobe 8, but this value is preferably 29 dB or more lower than the main lobe. Here, the 3 dB beam width of the radiation directivity in the vertical plane is 90.
°.

FIG. 10 shows a calculation example of the directivity in the horizontal plane of the antenna of FIG. 8 using the moment method. In FIG. 10, φ is a spherical coordinate. In FIG. 10, reference numeral 18 denotes a side lobe having directivity in a horizontal plane. Here, the same values as those of FIG. 9 are used for the antenna structure parameters, and at this time, the 3 dB beam width is 49 °.

FIG. 11 shows 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. In FIG. 11, 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
Terminal 3 has a large transmission antenna gain and a large reception antenna gain. On the other hand, in the 14 terminals, both the transmission antenna gain and the reception antenna gain are small in the direct wave, and both the transmission antenna gain and the reception antenna gain are large in the interference wave. For this reason, there is a defect that D / U deterioration increases.

[0010]

As described above, the conventional three-dimensional corner reflector antenna has a drawback that a null is generated directly above the excitation element, which causes a deterioration in the D / U ratio and a blind spot. there were. In addition, the only way to suppress side lobes and back lobes using a conventional corner reflector is to increase the height of the reflector and the length of the reflector to increase the aperture area. There was a disadvantage that it could not be done. As a means for expanding the apparent aperture area without changing the size of the antenna, there is a method using a dielectric. However, in this case, there is a disadvantage that a loss due to the dielectric or side lobe occurs.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an antenna device which does not cause a null just above an excitation element without losing the shape of a main lobe, and realizes an antenna device The purpose is to reduce the back lobe without changing the size.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is characterized in that a metal ground plate, an excitation element erected on the metal ground plate, and one or more reflection elements surrounding the excitation element are provided. An antenna device on which a plate is mounted, 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 ground plate, wherein the antenna changeover switch is arranged at the center of the metal ground plate, 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 differ from each other in that a rear reflector behind the excitation element is inclined with respect to the direction in which radio waves are emitted.

[0015]

With the structure 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, thereby eliminating dead areas. . Also, by inclining the reflector behind the excitation element toward the excitation element, without increasing the height of the antenna device, without changing the beam width of the horizontal plane directivity and the vertical plane directivity, The emission of the back lobe is reduced by -20 dB without generating unnecessary side lobes.
i.

Further, since the above-mentioned structure is used, a space generated by tilting the rear reflector can be used as a place for installing a switch and a circuit for switching the antenna, and the antenna device can be downsized. It becomes possible.

[0017]

FIG. 1 shows a first embodiment of an antenna device according to the present invention, and shows a structure of a three-dimensional corner reflector in which a reflector behind an excitation element is inclined. FIG. 1A is an overview diagram,
(B) is a side view. In FIG. 1, 1 is an excitation element,
2 is a reflector, 3 is a metal ground plate, 6 is a reflector behind the excitation element 1 installed at an angle, 7 is an angle α of a corner reflector composed of two reflectors, and 19 is an angle of the rear reflector. Angles β, X, Y, and Z indicating the inclination are orthogonal coordinates.

FIG. 2 shows a calculation example using the moment method for the directivity in the vertical plane of the antenna of FIG. In FIG. 2, θ is a spherical coordinate. FIG. 2 shows a value obtained 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. Θ = −90 ° to θ = 90 when the wavelength, the length R of the reflector is 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. ° indicates the radiation directivity in the vertical plane. Here, the metal base plate is assumed to be infinity in order to simplify the calculation.

In FIG. 2, reference numeral 8 denotes a main lobe, which forms a main beam, and reference numeral 9 denotes 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 FIG. 3 of the prior art. On the other hand, the 3 dB beam width in the main lobe of 8 is 93 °, which is larger than the case where the rear reflector 6 is not tilted.

FIG. 3 shows the radiation directivity in the horizontal plane of the antenna of FIG. Compared with FIG. 10 shown in the prior art, the emission of the back lobe is eliminated. 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 inclining the rear reflector of the three-dimensional corner reflector by 27 °, it is possible to eliminate the dead zone of the radiation directivity in the vertical plane and to reduce the back lobe. In the present invention, the corner angle α is 1
This effect can be obtained even at 80 °, that is, when only one reflector is used. Further, the same effect can be obtained when a great angle corner reflector in which the corner angle α is larger than 180 ° is used.

FIG. 4 shows characteristics of the present antenna using the inclination angle β of the rear 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
When the angle is close to 0 °, the gain is as small as −10 dBi or less, but it can be confirmed that when the reflector is tilted, the gain level increases and no null is generated.

FIG. 4B shows the level of the back lobe 10. When the angle β of the inclination of the reflector is 27 °, the radiation to the back lobe is the smallest. When β is in the range of 10 ° to 40 °, the back lobe level is lower by 3 dB or more than in the conventional case where β is 0 °. FIG.
When β is made negative in (b), the back lobe becomes large. However, it can be seen from FIG. 4A that the null can be eliminated. Therefore, the effect is obtained in the case where the back lobe does not cause a problem. is there.

FIG. 4C shows a value of a beam width of 3 dB on a horizontal plane,
FIG. 4D shows the value of the beam width of 3 dB on the vertical plane.
When β is a positive value of 10 ° or more, that is, when the rear reflector is inclined toward the excitation element, it can be confirmed that there is little change in the value of the beam width in both the horizontal plane and the vertical plane.
FIG. 4E shows a 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, in which a three-dimensional corner reflector in which a rear reflector of an excitation element is inclined is arranged in an array, and an antenna changeover switch 4 is provided in a space generated. ing. In the present invention,
Since the space surrounded by the inclined rear reflector can be effectively used, a small antenna device can be realized without using a small and expensive switch.

FIG. 6 shows a third embodiment of the present invention, which is an antenna device in which the director 20 is arranged in front of the excitation element 1. The director 20 is not connected to the antenna change-over switch 4, but functions to give good directivity by being excited by the radio wave radiated from the excitation element 1. Needless to say, the effect of the present invention is also effective in the case where the director is used for one sector antenna. In FIG. 6, reference numeral 20 denotes a director.

[0027]

As described above, the antenna device of the present invention uses the rear reflector inclined to the excitation element. The level directly above the antenna can be increased without increasing the size of the antenna. Further, 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 of the main lobe on the horizontal plane and the vertical plane from the conventional case where the reflector is not tilted. Furthermore, by arranging this antenna on a metal ground plate divided into sectors, it is possible to realize a small antenna device with high space utilization efficiency by installing a sector antenna switch in the space created by tilting the reflector. It becomes possible.

[Brief description of the drawings]

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

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

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

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

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

11 is a diagram illustrating 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 Height of reflector R Reflector length X, Y, Z Cartesian coordinates θ, φ Spherical coordinates 1 Exciting element 2 Reflector 3 Metal ground plate 4 Antenna switch 5 Reflector height Hr 6 Back reflector 7 α , Corner angle of corner reflector 8 main lobe 9 back side lobe 10 back lobe 11 range η 12 to be blind zone 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 Side lobe (directivity in horizontal plane) 19 β, tilt angle of back reflector 20 Wave director

Continuation of the front page (56) References JP-A-52-106291 (JP, A) JP-A-1-114099 (JP, A) JP-A-6-29730 (JP, A) JP-A-48-94345 (JP, A) JP-A-1-204505 (JP, A) JP-A-61-25304 (JP, A) JP-A-64-1723 (JP, U) Patent 175605 (JP, C2) (58) Int.Cl. ⁷ , DB name) H01Q 19/10 H01Q 3/00 H01Q 15/18

Claims (6)

(57) [Claims] 1. A ground plane of at least a surface of a conductor, an excitation element provided on the ground plane, and at least one
In a three-dimensional corner reflector antenna having at least a plurality of co-surface reflectors, a rear reflector provided rearward in a main beam direction with respect to the excitation element is tilted from a direction perpendicular to the ground plane. An antenna device characterized by the above-mentioned. 2. The antenna device according to claim 1, wherein the rear reflector is installed at an angle of 10 ° to 40 ° from a direction perpendicular to the ground plane toward the excitation element. 3. An antenna device comprising: a plurality of the antenna devices according to claim 1; and an antenna changeover switch for selecting one of the plurality of antenna devices. 4. The antenna device according to claim 3, wherein
An antenna device characterized in that a plurality of antenna devices configured have a common reflector adjacent thereto. 5. The antenna device according to claim 3, wherein the plurality of configured antenna devices are radially arranged in a circle, and the antenna switch is arranged in the center of the circle. An antenna device, wherein the rear reflector is arranged so as to surround the antenna switch. 6. The antenna device according to claim 1, wherein a director is provided on the ground plane surrounded by the corner reflector.