JPS6347061Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a fan-shaped beam antenna suitable for small to medium capacity microwave multidirectional multiplex communication.

The small to medium capacity microwave multidirectional multiplex communication system uses a wide-angle fan-shaped beam antenna (beam width Θ1/
2≒45°) to communicate equally and simultaneously with several slave stations dispersed within a service area, and has the advantage that communication lines can be constructed economically. The slave station side is equipped with a pencil beam antenna for general microwave multiplex communication (Θ1/2≒ in the 2GHz band).
5°) is used. When implementing this method, if the service area is wide, it cannot be covered by one wide-angle fan beam antenna, so it is necessary to combine this antenna with multiple pencil beam antennas, or to combine multiple pencil beam antennas. A combination of wide angle fan beam antennas is performed. In such a case, each antenna is required to have a steep beam rise and low side lobes in order to suppress mutual interference between adjacent antennas in combination and interference waves from other lines.

By the way, when two wide-angle fan beam antennas are used in combination as described above, the total beam width may be too wide depending on the desired service area, and radio waves may be emitted in unnecessary directions, causing interference with other lines. This causes an inconvenience. In addition, when a multi-directional line is configured by combining one wide-angle fan beam antenna and several pencil beam antennas, the total wind area of these antennas becomes considerably large, so it is necessary to make the support tower on which the antenna is mounted strong. Therefore, the economic efficiency of the entire line will be hindered.

This problem can be solved by having the wide-angle fan beam antenna cover the main area of the desired service area, and the remaining area being covered by an arbitrary medium-angle fan beam antenna.
Conventionally, no medium-angle fan beam antenna that can be adapted to such uses has been proposed.

Note that it is also possible to use a parabolic reflector with a rectangular aperture shape or a fan beam antenna equipped with a parabolic cylindrical reflector used for radar etc. for the above multiplex communication, but this type of antenna However, there is a problem that the beam rises slowly and mutual interference occurs when a plurality of beams are combined. Moreover, the spillover amount of the excitation wave of the primary radiator leaking from the short side direction of the reflecting mirror is superimposed on the wide-angle directivity, resulting in poor F/B characteristics (front-to-back ratio characteristics of directivity).
Therefore, it does not meet the requirements for a low sidelobe antenna, and there is interference with other lines. Therefore, this type of antenna cannot be used as an antenna for multidirectional multiplex communication systems.

An object of the present invention is to provide an antenna capable of radiating a desired medium-angle fan beam suitable for use in combination with the wide-angle fan beam described above.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.

The fan beam antenna according to the present invention has two antennas having the same shape, as shown in FIG.
The compound curved reflector 4 has a shape in which two parabolic reflector parts 2 and 2' are symmetrically arranged and joined together.

The original shape of each of the above-mentioned reflecting mirror sections 2, 2' is a deep-type (focal position is within the aperture plane) axisymmetric paraboloid of revolution reflecting mirror 1 shown in FIG. It is obtained by cutting with a plane that passes through the focal point F and makes an angle α with the optical axis x. In other words, the overcut side is the reflecting mirror section 2,
It becomes 2'. Note that the reference numeral 3 indicates the reflecting mirror portion on the undercut side.

The reflector 1 in its original form is one that has been widely used as an antenna for microwave ultra-super multiplex communication systems, and is therefore relatively inexpensive and easily available.
Processing (forming by drawing, etc.) is also easy. In this embodiment, the reflecting mirror sections 2, 2' are obtained by cutting a lens whose focal length to aperture diameter ratio f/D is 0.25.

Two reflecting mirror parts 2, 2' obtained by the above method
The compound curved reflector 4 shown in FIG. 2, which is formed by joining the parabolic cut ends of By arranging the primary radiator 5 at the intersection position (corresponding to the focal position of the original reflecting mirror 1), it functions as a fan beam antenna.

That is, when the reflecting mirror 4 is excited by the primary radiator 5, each radiated wave by the parabolic reflecting mirror parts 2, 2' is generated at angles x, It has directivity, ′ in the x′ direction, and their combined directivity is fan-shaped as shown by the solid line.

Furthermore, since the antenna has a low side lobe design, the primary radiator 5 has an illuminance distribution of the excitation wave on the reflecting mirror aperture of approximately cos θ (θ is the radiation angle from the front of the radiator). I am using it.

The main beam directivity of the fan-shaped beam antenna according to the present invention having the above configuration changes depending on the cutting angle α of the reflecting mirror portions 2, 2', and curves 7, 8, 9 and 10 in FIG. are, respectively, the above angle α is 5°,
The main beam directivity is shown when configured to have an angle of 6°, 7°, and 8°. As is clear from the figure, as the angle α becomes larger, a fan-shaped beam with a wider angle can be obtained, but on the other hand, the unevenness at the tip of the beam becomes larger. Practically, it is preferable to suppress the above-mentioned unevenness to within 3 dB, and each directivity shown in the figure satisfies this condition. Each antenna with these directivity has a beam width Θ1/2, which is the angular width at a level 3 dB lower than the maximum radiation value of the beam.
They function well as medium-angle fan beam antennas with beam widths of 12°, 17°, 20°, and 22°, respectively.

A solid curve 6 in the figure shows the main beam directivity of a pencil beam antenna using the original paraboloid of revolution reflector 1 shown in FIG. 1, and its beam width is about 5 degrees.

The antenna according to the present invention has the above-mentioned original shape reflector 1.
It can also be constructed using a shallow parabolic reflector whose focal point is in front of the aperture plane, but in the case of this type of antenna that requires low side ropes, the above embodiment Preferably, the deep reflector shown is used as the original reflector. Second
In the case shown in the figure, the curved reflector 4 can of course be integrally molded, but from the viewpoint of economy and precision, it is better to adopt an assembly mode in which the original parabolic reflector 1 is cut as described above. is a good idea.

The fan-shaped beam antenna according to the present invention has a medium-angle main beam directivity as described above. Therefore, by combining an appropriate number of antennas of the present invention with the wide-angle fan beam antenna, or with the antenna and the pencil beam antenna,
A multidirectional multiplex communication line can be configured with the minimum required number of antennas depending on the angle of the service area as seen from the master station. This means that the wind pressure load on the support tower can be reduced as much as possible by minimizing the total wind area of the antenna mentioned above, and that it is possible to prevent harmful effects on other lines due to unnecessary angular beam directions. Therefore, by using the antenna of the present invention, it is possible to construct a communication line that is more economical and practical from a comprehensive perspective.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view conceptually showing a paraboloid of revolution reflector, which is the original form of the compound curved reflector used in the fan beam antenna of the present invention, and Fig. 2 is the configuration of an antenna according to an embodiment of the present invention. FIG. 3 is a diagram showing the main beam directivity of the antenna according to the present invention. 1... Original paraboloid of revolution reflector, 2, 2'...
Parabolic reflector section, 4...Compound curved reflector, 5...
Primary radiator.

Claims (1)

[Scope of utility model registration request] The mirror surface of the larger shape of the two mirror bodies that would be obtained by cutting an axially symmetric rotating parabolic reflector along a plane that passes through its focal point and intersects the optical axis at a predetermined angle α. A reflecting mirror formed by joining two reflecting mirror parts 2, 2' having the same shape as the body in such a manner that their parabolic end surfaces match;
a fan beam antenna comprising a primary radiator for exciting the reflector;