JPS5820161B2 - antenna device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an antenna device that is an aperture antenna used in a high frequency band higher than microwaves and has an excellent wide-angle radiation pattern.

An example of a conventional aperture antenna is shown in FIG.

In FIG. 1, 1 is a feeding horn, 2 is a reflecting mirror surface which is a part of a parabolic mirror of revolution, and 3 is a cylindrical structure.

In the antenna having such a configuration, a spherical wave radiated from the feeding horn 1 is reflected by the reflecting mirror surface 2 to become a plane wave, which passes through the cylindrical structure 3 and is radiated to the outside.

However, in this case, the edge of the opening P1. A diffraction phenomenon occurs at P2, and the wide-angle radiation pattern is degraded by the diffracted waves.

In other words, if we define an angle θ indicating a sufficiently distant observation point S as shown in Fig. 1, when θ is greater than 90°, the diffracted wave Ed contributing to the radiation level of S is the diffracted wave from Pl. , which is expressed by the following equation, assuming that the electric field strength at Pl is Ei.

S is the distance between Pl and S, a is the radius of the aperture, and k is the wave number.

Here, D(φ, φ') is a diffraction coefficient, which is expressed in the following form according to the geometric optical diffraction theory.

(l is the case where the polarization is parallel to the edge (the force is perpendicular).

In order to eliminate such drawbacks, the present invention has developed a conical metal plate or a metal plate consisting of a set of straight lines that form a fixed angle with respect to the direction of propagation of radio waves at each point on the edge of the opening. It is characterized by the provision of a shielding plate with a structure provided with a radio wave absorber, the purpose of which is to reduce diffracted waves by lowering the incident level to the edges that contribute to the wide-angle radiation pattern: to have an excellent wide-angle radiation pattern The purpose is to realize an antenna device, and the drawings will be described in detail below.

FIG. 2 shows an embodiment of the present invention, which has a structure in which a conical shielding plate 4 is attached to the edge of the aperture of the aperture antenna shown in FIG.

With such a structure, it is the diffracted wave Ed from Qt that contributes to the wide-angle radiation pattern, and if the electric field strength at Ql is E, it can be expressed by the following equation.

The electric field Ei1 at Ql is a diffracted wave from Pl, so P
It is determined from the electric field strength Ei at l by the following equation.

Here, 01 indicates the angle formed by the radio wave path and the baffle plate as shown in FIG. 2, and Sl indicates the distance between Pl and Ql.

DI (φ, φ') is expressed by the following equation.

As an example of calculation, 2a-1661!1711 θ1-2
FIG. 3 shows the calculation results for the case of 0°, S1=293 mm, and frequency of 31 GHz.

In Figure 3, the vertical axis is the diffracted wave E from Pl or Ql.
The relative level of d (dB), the horizontal axis shows the angle θ.

It can be seen from this figure that the level of diffracted waves contributing to the wide-angle radiation pattern can be significantly improved.

In addition, in FIG. 3, the solid line A indicates P in the conventional case of FIG.
The level of the diffracted wave is shown from Ql, and the broken line B shows the level of the diffracted wave from Ql in the second embodiment of the present invention.

Furthermore, by providing a radio wave absorber inside the baffle plate, the opening edge P1 shown in FIG. It is possible to prevent the diffracted wave from P2 from being reflected inside the deflection wave and affecting the radiation pattern.

Although the case where the shape of the aperture is circular has been described above, the present invention is not limited to this and may be used for apertures of any shape.

Furthermore, although the above explanation has been made for the case where the wavefront of the aperture is a plane, the present invention is not limited to this, and as shown in FIG. An aperture antenna that emits shaped waves can also be used in the same way.

In addition to being used alone as an aperture antenna, it can also be used in the primary radiator system of the antenna, as shown in FIG. 5, to improve the wide-angle radiation pattern of the entire antenna.

Furthermore, by using an offset type antenna, it is possible to avoid deterioration of the wide-angle radiation pattern due to blocking caused by the shield plate.

As described above, in the antenna device according to the present invention,
The effect of the conical baffle plate provided at the edge of the opening has the advantage that an antenna device with an excellent wide-angle radiation pattern can be easily realized.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view showing the configuration of a conventional antenna device;
The figure is a sectional view showing the configuration of one embodiment of the present invention, FIG. 3 is a diagram showing calculation results showing the effects of the present invention, and FIG. 4 is a sectional view showing the configuration of another embodiment of the present invention. FIG. 5 is a sectional view when the present invention is used as one of the components of an antenna device. In the figure, 1 is a feeding horn, 2 is a reflecting mirror surface, 3 is a cylindrical shielding plate, 4 is a shielding plate of the present invention, 5 is a sub-reflector, and 6 is a main reflector. Further, the solid line A in FIG. 3 represents the diffracted wave from the edge P1 of the conventional antenna device shown in FIG. 1, and the broken line B represents the diffracted wave from the edge Q1 in the case of the embodiment of the present invention shown in FIG. This indicates the level. In the drawings, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1. It has an aperture antenna used in a high frequency band above the microwave band, and a radio wave path leading to the aperture of the aperture antenna is covered with a structure made of a metal plate. In this type of antenna device, a shielding plate made of a cone-shaped metal plate made of a set of straight lines forming a predetermined angle with respect to the direction of propagation of radio waves at each point of the opening is provided on the edge of the opening. Characteristic antenna device. 2. The antenna device according to claim 1, characterized in that a radio wave absorber is provided on the surface of the barrier plate made of a metal plate on the side closer to the radio wave path. 3. In an antenna device that is used in a high frequency band above the microwave band and has a primary radiator system as part of the antenna system, each point on the line is placed at the edge of the aperture of the secondary radiator. An antenna device comprising a shielding plate made of a cone-shaped metal plate made of a set of straight lines forming a predetermined angle with respect to the direction of propagation of radio waves. 4. The antenna device according to claim 3, characterized in that a radio wave absorber is provided on the surface of the barrier plate made of a metal plate on the side closer to the radio wave path. 5. The antenna device according to claim 3, wherein the antenna system is an offset type antenna system.