JPS603242B2 - antenna device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION In order to improve the front-to-side radiation ratio and front-to-back radiation ratio of wide-angle radiation characteristics in a Sekiguchi plane antenna such as a parabolic antenna or a Cassegrain antenna, This relates to radio wave shielding that can be installed.

Conventionally, this type of device has been equipped with a radio wave shielding plate 2 around the Sekiguchi of the reflecting mirror 1 as shown in Fig. 1a, and
As shown in the figure, there is an uneven metal fin 3 around the Sekiguchi area of the reflector 1.
There was a format that provided . The radiated electric field on the sides and rear of the antenna is given by the radio waves from the primary radiator 5 that are shielded by the reflector 1 or the fin wave and hit the edge 4a of the plate 2 or metal fin 3, and the diffracted waves from the edge 4a. . Figure 1a
By attaching the radio wave shielding plate 2 as shown in FIG. Therefore, the wide-angle radiation characteristics can be improved to some extent, but if a relatively good one is to be achieved, there is a momme point at which the width of the radio wave shielding plate 2 becomes wider. As shown in FIG. 1b, the method of improving the wide-angle radiation characteristics by making the phases of the diffracted waves from the edge 4a of the reflecting mirror 1 and the diffracted waves from the edge 4a of the metal fin 3 opposite to each other is compared. The disadvantages are that the frequency band with good characteristics is narrow and the angular range is narrow. In order to eliminate these drawbacks, the present invention provides two or more radio wave shields along the periphery of the aperture of the reflector of the aperture antenna, and makes a suitable hole in the radio wave shield closest to the reflector. By increasing the number of antennas, the radio waves propagating to the sides and rear of the antenna are reduced.The drawings will be described in detail below.

FIG. 2 shows an embodiment of the present invention, in which a perforated metal plate 7 is provided along the periphery of the entrance of the reflector 1, and a hole is provided outside the perforated metal plate 7 when viewed from the primary radiator 5. A diffracted wave shielding plate 6 made of a metal plate, wire mesh, or linear metal is provided at a position that does not protrude beyond the edge 4a.

FIG. 3 is an enlarged view of the periphery of the reflecting mirror 1. With this structure, the incident wave 8 that has entered the perforated metal plate 7 from the primary radiator 5 can be transmitted to the green 4 of the perforated metal plate 7.
The diffracted waves 9 are diffracted by the three edges a and the edges 4c on both sides of the hole.
It becomes a. These diffracted waves 9a interfere with each other, forming a composite electric field with a large difference in strength. Therefore, the configuration is such that the edge 4b of the diffracted wave shielding plate 6 is located at the position where the combined electric field is the minimum, and the green 4b of the diffracted wave shielding plate 6, the green 4a of the perforated metal plate, and the phase center of the primary radiator The line connecting
By configuring it to be convex in the direction of propagation of radio waves reflected from the reflecting mirror 1, the electric field at the edge 4b of the diffracted wave shielding plate 6 can be minimized. Therefore, the diffracted waves 9b propagating from the edge 4b of the diffracted wave shielding plate 6 to the sides and rear of the antenna become very small. On the other hand, as shown in Figure 4, by making the tip of the diffraction wave shielding plate green and gently bent, the direction of the electric field of the incident wave incident on the edge can be easily aligned, and the strength and weakness of the composite electric field can be adjusted. The electric field at the edge can be minimized regardless of the position of the edge. Further, by providing a plurality of diffracted wave shielding plates 6, the diffracted waves propagating to the sides and rear of the antenna become diffracted waves twice or more, and can be sufficiently reduced by 4. In addition, although the case of a parabolic antenna has been described above, the present invention is not limited to this, and similar effects can be obtained even when used around the sub-reflector or main reflector of a Cassegrain antenna.

As described above, in the antenna device according to the present invention, two or more crab wave shields are provided along the periphery of the sekiguchi of the reflector, and an appropriate hole is made in the radio wave shield closest to the reflector. This has the advantage that the radio waves propagating to the sides and rear of the antenna can be reduced, and the front-to-side radiation ratio and front-to-back radiation ratio can be improved.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a reflector equipped with a conventional radio wave shield, Fig. 2 is a side view of an embodiment of the inventive device, Fig. 3 is an enlarged view of the area around the opening in Fig. 2, FIG. 4 is an enlarged view of the area around the opening of another embodiment of the device of the present invention. In the figure, 1 is a reflector, 2 is a radio wave shielding plate, 3 is a metal fin,
4 is an edge, 5 is a primary radiator, 6 is a diffracted wave shielding plate, 7 is a perforated metal plate, 8 is an incident wave, and 9 is a diffracted wave. In the drawings, the same or corresponding parts are denoted by the same reference numerals. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In an aperture antenna consisting of a primary radiator and a reflector, a radio wave shield with holes is provided along the periphery of the aperture of the reflector, and the radio wave shield is A line that connects the edge of one or more radio wave shields at a position that does not protrude beyond the edge of the object, the edge of the radio wave shield with a hole, and the phase center of the primary radiator. An antenna device characterized in that the antenna device is configured to have a convex shape with respect to the traveling direction of radio waves reflected from the reflecting mirror. 2. The antenna device according to claim 1, which uses a metal plate as a radio wave shield. 3. The antenna device according to claim 1, which uses a wire mesh as a radio wave shield. 4. The antenna device according to claim 1, which uses a linear metal as a radio wave shield.