JP4202572B2 - Omnidirectional antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an omnidirectional antenna formed by combining a plurality of planar antennas.
[0002]
[Prior art]
An omnidirectional antenna may be used as a base station antenna such as a mobile phone or a PHS. Some omnidirectional antennas are configured by combining a plurality of antennas as described above. For example, there is a combination of a plurality of antennas each including a reflector and a radiating element.
[0003]
[Problems to be solved by the invention]
Such an omnidirectional antenna desirably has a large gain. In order to increase the gain, it is necessary to increase the area of each antenna. That is, when only one antenna element is used, it is necessary to enlarge the reflector to some extent. When a non-directional antenna is configured by combining a plurality of antenna elements, it is desirable that the phase difference between the antennas is small. However, when the antennas are arranged on the same plane and combined, a phase difference occurs between the individual antennas. This tendency becomes more prominent as the reflector is larger, and there is a problem that complete omnidirectionality cannot be obtained.
[0004]
An object of the present invention is to obtain an antenna having high gain and good omnidirectionality.
[0005]
[Means for Solving the Problems]
The omnidirectional antenna according to the present invention has three or more planar antennas combined such that each closed side in the same plane forms a planar shape having the same length . The planar shape can be a polygon such as a triangle or a quadrangle. The planar antenna may be for linearly polarized waves or circularly polarized waves. The planar antenna can include at least a reflector and a radiating element, and the radiating element can have various shapes such as a circular shape, a rectangular shape, or a crank shape. Each radiating element is provided on each substrate so that the radiation directions of the beams do not intersect. In each of these planar antennas, a common reflector is provided at the junction with the adjacent planar antenna so as to protrude to the outside in common with the adjacent planar antenna. The common reflector is provided substantially perpendicular to the plane. The outputs of the respective planar antennas are combined in phase, and the amount of protrusion to the outside of the common reflector is about 1/4 of the spatial wavelength of the received signal.
[0006]
According to this omnidirectional antenna, since the common reflector is provided on both sides of each antenna element, the total area of the reflector is larger than when no common reflector is provided and the gain is improved. To do. In addition, since the reflectors are provided in common for the adjacent antennas, the reflectors of the respective antennas can be made small, and the phase difference between the adjacent antennas is reduced. Therefore, an omnidirectional antenna can be obtained. And since it is a common reflecting plate, manufacture is easier than the case where an additional reflecting plate is provided for each antenna and these additional reflecting plates are combined. In addition, it is desirable for each common reflector to have the same shape in order to reduce the phase difference. Moreover, it is desirable that each reflector has the same shape.
[0007]
Each of the planar antennas may include at least one radiating element formed continuously in a direction substantially perpendicular to the plane. In this case, each planar antenna can be continuously provided in a direction substantially perpendicular to the plane, for example, a substrate and a reflector provided on one surface thereof, and a radiation element provided on the other surface, Alternatively, a reflecting plate is provided on one surface of a long substrate arranged in a direction substantially perpendicular to the plane, and a plurality of radiating elements are provided on the other surface along the length direction of the substrate. You can also. In either case, the common reflector can also be extended along each planar antenna in a direction substantially perpendicular to the plane.
[0008]
When configured in this way, the number of radiating elements can be increased, so that the gain of the omnidirectional antenna can be increased.
[0010]
Each planar antenna includes a substrate that is combined to form the closed planar shape, a reflecting plate formed on the inner surface of the substrate, a planar radiating element formed on the outside of the substrate , Can be provided .
[0011]
In such a configuration, the radiation beams from the radiation elements do not cross each other, and the common reflectors do not interfere with each other.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The omnidirectional antenna according to the first embodiment of the present invention is for receiving, for example, a 2.6 GHz band radio wave, and includes a plurality of, for example, four planar antennas 2a to 2a as shown in FIG. 2d. Each of the planar antennas 2a to 2d has the same shape and size. Each of the planar antennas 2a to 2d includes a rectangular substrate having the same size, for example, a square substrate, for example, dielectric substrates 4a to 4d. The dielectric substrates 4a to 4d are formed with reflecting plates 6a to 6d over the entire area of one surface thereof as shown in FIG. These reflectors 6a to 6d can be formed by, for example, applying conductive metal plating to the dielectric substrates 4a to 4d or depositing a conductive metal thin film. Conductive metal radiating elements 8a to 8d are formed on the other surfaces of the dielectric substrates 4a to 4d. In this embodiment, the radiating elements 8a to 8d are circular and have the same size. The planar antennas 2a to 2d have the reflectors 6a to 6d as described above and the radiating elements 8a to 8d provided so as to be spaced apart from each other by a certain distance (thickness of the dielectric substrate).
[0013]
Such planar antennas 2a to 2d are combined so as to form a closed planar shape, for example, a square, in a certain plane. That is, the planar antennas 2a to 2d are assembled so as to form an angle of 90 degrees with each other so as to form each surface of a cube having upper and lower surfaces opened. In this assembled state, in each of the planar antennas 2a to 2d, the reflecting plates 6a to 6d are located on the inner surface side of the cube, and the radiating elements 8a to 8d are located on the outer surface side. With this configuration, the radiation beams of the planar antennas 2a to 2d do not intersect each other. The outputs of the planar antennas 2a to 2d configured in this way are combined by cables having the same length. That is, any received output is synthesized without phase adjustment by the phase shifter.
[0014]
In each of the planar antennas 2a to 2d, common reflectors 10a to 10d are formed at the boundaries with the adjacent planar antennas, for example, at the apexes of each square formed by the dielectric substrates 4a to 4d. These common reflectors 10a to 10d are formed in a rectangular shape whose long sides are approximately equal to the length of one side of the dielectric substrates 4a to 4d. The common reflectors 10a to 10d are attached such that the long sides thereof coincide with the joint portions of the dielectric substrates 4a to 4d, and the short sides protrude outward. As is apparent from FIG. 1B, each of the common reflectors 10a to 10d has an equal angle with each of the two dielectric substrates located on both sides thereof. The short sides of the common reflectors 10a to 10d all have the same length. Since these common reflectors 10a to 10d are provided radially outward, they do not physically interfere with each other. These common reflectors 10a to 10d are formed symmetrically with respect to a straight line passing through the center of the square formed by the dielectric substrates 4a to 4d.
[0015]
A radome 12 is disposed outside the common reflectors 10a to 10d so as to surround the planar antennas 2a to 2d. The radome 12 is formed, for example, in a cylindrical shape, and the common reflectors 10a to 10d are coupled to the inner peripheral surface thereof. In this way, each of the common reflectors 10a to 10d supports the radome 12. Therefore, it is not necessary to separately provide a holder on each of the dielectric substrates 4a to 4d, and since these common reflectors 10a to 10d can be used for positioning the radome 12, the characteristics of each planar antenna are not affected.
[0016]
FIG. 2 shows a short of each of the common reflectors 10a to 10d when the dimension D of the reflectors 6a to 6d is 0.7λ ₀ (λ ₀ is the free space wavelength of the received signals of these planar antennas 2a to 2d). the dimension d of the edge, 0 (no common reflector), 0.09λ _0, 0.18λ _0, indicates the respective combined directivity characteristics when a 0.26Ramuda _0, 3, 0.8Ramuda dimension D ₀ and then, the dimension d 0,0.09λ _0, 0.18λ _0, indicates the respective combined directivity characteristics when a 0.26Ramuda _0, 4 dimensions D, and when the 0.9Ramuda _0, dimension d the, 0,0.09λ _0, 0.18λ _0, indicates the respective combined directivity characteristics when a 0.26λ _0.
[0017]
From these figures, it can be seen that by providing the common reflectors 10a to 10d, the combined directional characteristics approach omnidirectional characteristics. That is, when the dimension D is constant, increasing the dimension d gradually approaches omnidirectionality, and when d is 0.26λo (about λo / 4), from d = 0 to d = 0.26λo. combined directivity characteristic closest to the omnidirectional between is obtained. Further, the gain is similar to the case of D = 0.8λo and d = 0, and the case of D = 0.7λo and d = 0.09λo, and D = 0.9λo, d = The case of 0 is almost the same as the case of D = 0.89λo and d = 0.09λo. In general, the larger D is, the larger the gain is. Therefore, it is possible to obtain the same gain as when D is large and no common reflector is provided even in a state where D is small. It is shown that the gain is increased by the provision. As described above, when a plurality of antennas are combined on the same plane, a high-gain and non-directional combined pattern can be obtained without increasing the reflectors 6a to 6d.
[0018]
In general, an omnidirectional antenna is provided on a rooftop of a building, for example, and may be used as an antenna for mobile communication. It is desirable that the omnidirectional antenna mounted on the rooftop of a building be small and not easily affected by wind pressure. Since the omnidirectional antenna can be reduced in size, it is suitable for such an application.
[0019]
FIG. 5 shows an omnidirectional antenna according to the second embodiment. In the omnidirectional antenna of this embodiment, the dielectric substrates 4a to 4d are long. That is, the dielectric substrates 4a to 4d have a rectangular shape that is long in a direction substantially perpendicular to the plane formed by these. A plurality of radiating elements 8a to 8d are formed on the outer surface of each of the dielectric substrates 4a to 4d in a line along the long side direction. Of course, each of the radiating elements 8a to 8d has the same size and shape. Reflectors 6a to 6d are formed on the entire back surface of each dielectric substrate. The long sides of the common reflectors 10a to 10d also have a length equal to the length of each dielectric substrate 4a to 4d.
[0020]
With this configuration, the number of radiating elements 8a to 8d can be increased as compared with the omnidirectional antenna of FIG. 1, and thus the combined gain can be improved as compared with the omnidirectional antenna of FIG. Also in this omnidirectional antenna, similarly to the omnidirectional antenna of FIG. 1, a cylindrical radome can be provided and this radome can be supported by each common reflector. Further, by stacking a large number of the omnidirectional antennas shown in FIG. 1 in a direction substantially perpendicular to the closed plane, the omnidirectionality is improved in synthetic gain compared to the one-element omnidirectional antenna shown in FIG. An antenna can be obtained. Also in this case, a total of four common reflectors can be provided in common for a plurality of combined antennas composed of four planar antennas constituting a closed planar shape, similar to that shown in FIG.
[0021]
FIG. 6 shows an omnidirectional antenna according to the third embodiment. This omnidirectional antenna is configured in the same manner as the omnidirectional antenna of the first embodiment, except that the three planar antennas 2a to 2c are used so that the closed planar shape is substantially an equilateral triangle. Yes. Equivalent parts are denoted by the same reference numerals and description thereof is omitted.
[0022]
When the omnidirectional antenna of FIG. 6 is configured using the planar antenna of the same size and shape used in the omnidirectional antenna of FIG. 1, the size can be further reduced as compared with the omnidirectional antenna of FIG. it can.
[0023]
In the above embodiment, squares and regular triangles are shown as closed planar shapes, but other shapes such as regular polygons such as regular hexagons and regular octagons may be used. In addition, in order to make the closed planar shape a regular polygon, each dielectric substrate has the same size and shape. However, when the closed planar shape does not have to be a regular polygon, different sizes and shapes are used. It is also possible to use a dielectric substrate. In each of the above embodiments, a circular element is used as the radiating element. However, various types such as a rectangular element and a crank type element can be used, and a linearly polarized element can also be used. It may be for circular polarization.
[0024]
【The invention's effect】
As described above, in the omnidirectional antenna according to the present invention, an antenna having high gain and good omnidirectionality can be obtained by providing a common reflector.
[Brief description of the drawings]
FIG. 1 is a perspective view and a plan view of an omnidirectional antenna according to a first embodiment of the present invention.
The dimensions of the common reflection plate in the case where the dimensions of the reflector omnidirectional antenna was 0.7Ramuda ₀ in FIG. 2 FIG. 1, which is a comprehensive directivity characteristic diagram in the case of changing from 0 to 0.26λ _0.
3 is a comprehensive directional characteristic diagram when the dimension of the common reflector is changed from 0 to 0.26λ ₀ when the dimension of the reflector of the omnidirectional antenna of FIG. 1 is 0.8λ _0. FIG.
4 is a comprehensive directional characteristic diagram when the dimension of the common reflector is changed from 0 to 0.26λ ₀ when the dimension of the reflector of the omnidirectional antenna of FIG. 1 is 0.9λ _0. FIG.
FIG. 5 is a perspective view of an omnidirectional antenna according to a second embodiment of the present invention.
FIG. 6 is a plan view of an omnidirectional antenna according to a third embodiment of the present invention.
[Explanation of symbols]
2a to 2d Planar antennas 4a to 4d Dielectric substrates 6a to 6d Reflectors 8a to 8d Radiating elements 10a to 10d Common reflector

Claims (3)

Three or more planar antennas combined so that each closed side in the same plane forms a planar shape of the same length ;
In each of these planar antennas, a common reflector provided to protrude to the outside in common with the adjacent planar antenna at the junction with the adjacent planar antenna,
An omnidirectional antenna in which the outputs of the planar antennas are combined in phase, and the amount of protrusion of the common reflector to the outside is about 1/4 of the spatial wavelength of the received signal.   2. The omnidirectional antenna according to claim 1, wherein each planar antenna has a radiating element formed continuously in a direction substantially perpendicular to the plane. 2. The omnidirectional antenna according to claim 1, wherein each of the planar antennas includes a substrate combined so as to form the closed planar shape, a reflecting plate formed on an inner surface of the substrate, and an outside of the substrate. An omnidirectional antenna comprising a planar radiating element formed on the side.

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