JPH04122108A - Multi-beam antenna - Google Patents

Abstract

PURPOSE:To make a reflecting mirror small by adopting a curved face decided by weighted mean of coordinates of 1st and 2nd paraboloids of revolution for the reflecting mirror and deciding the two paraboloids of revolution so that they are coincident at a one point around the center of the reflecting mirror and their normals are coincident with each other at the coincident point. CONSTITUTION:A curved face decided by weighted mean of coordinates of two different paraboloids of revolution A, B is adopted for the reflecting mirror 1. The coordinates of the paraboloids of revolution A, B are coincident with each other (ZA=ZB) at one point P around the center of the reflecting mirror 1 and a normal vector 2 of the paraboloid of revolution A and a normal vector 2 of the paraboloid of revolution B are coincident with each other at the point P. Thus, the paraboloid of revolution A and the paraboloid of revolution B are almost made coincident with each other in the vicinity of the point P and they are almost coincident over the front face of the reflecting mirror 1. Thus, two electromagnetic waves in largely different directions radiate from the small sized reflecting mirror 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-beam antenna, and particularly to a multi-beam antenna that receives radio waves from two directions that are significantly different from each other.

[Conventional technology]

In recent years, direct satellite broadcasting, in which each home listens to television broadcasts by receiving radio waves from artificial satellites, has become popular. Furthermore, a large number of satellites that can be used for reception have appeared. For example, in Japan, a broadcasting satellite is launched at 110° east longitude in geostationary orbit, but a group of four communication satellites are launched at 150° east longitude, 154° 154°, 158° and 162° east longitude. It is being When these satellites are viewed from Japan, the first group of satellites (one in the above case) and the second group of satellites appear to be relatively separated by about 55 degrees.

In this case, in order to receive radio waves from each satellite at the same time, one antenna is usually required for each satellite. An area larger than 5 units is required, and it is assumed that it will be difficult to secure space for this amount.

Conventional techniques for solving such problems include:
There is a multi-beam antenna using a torus reflector 87 as shown in FIG. A torus b reflecting mirror is a reflecting mirror formed by a curved surface i formed by rotating a parabola around a -las rotation axis 7 which is substantially perpendicular to its central axis. Two primary radiators 91. ≦2 is the number of one primary radiator and the other primary radiator.

On the other hand, it is arranged at a position rotated by the beam separation angle 2 around the torus rotation axis 7.

[Problem to be solved by the invention]

In this conventional multi-beam antenna, as shown in FIG. If the beam separation signal δ is around 10", as in the case where the communication satellites in the group receive only the radio waves, the torus reflector 8 does not have to be very large, but In addition, if broadcasting satellites are included, the beam separation angle δ will be around 55°, and the usage area 81 for the beam direction of the first group and the usage area 8 for the beam direction of the second group.
2, the area of the torus reflector 8 becomes large, and the characteristics of the multi-beam antenna cannot be utilized.

[Means to solve the problem]

The multi-beam antenna of the present invention is determined by weighted averaging of the coordinate values of the first and second paraboloids of revolution, whose respective coordinate values and normal line coincide at one point and which are different from each other, using a weight of 0 or more and 1 or less. a reflecting mirror having a curved surface centered near the one point, at least one first primary radiator disposed near the focal point of the first paraboloid of revolution, and the second paraboloid of revolution. at least one second primary radiator located near the focal point of the object surface.

The value of the weight may be set based on a ratio between a beam gain requirement corresponding to the first primary radiator and a beam gain requirement corresponding to the second primary radiator.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a perspective view of an embodiment of the present invention.

This embodiment includes a reflector 1 and a first group of primary radiators 11.
12, 13, 14, and a second group of primary radiators 21 (one in this embodiment). In the following description, a case will be described in which this embodiment is used as a transmitting antenna, but due to the reversibility of the antenna, similar effects can be obtained when using it as a receiving antenna.

In the configuration of FIG. 1, the first group of primary radiators 11.12
, 13.14 are reflected by the reflecting mirror 1, and then radiated in the directions of 31, 32° and 33.34, respectively. On the other hand, the electromagnetic waves radiated from the second group of primary radiators 21 are reflected by the reflecting mirror 1 and then radiated in the direction 41.

Further explanation will be given with reference to FIG. 2, which is a longitudinal sectional view of the embodiment shown in FIG.

The reflecting mirror 1 is a curved surface obtained as a weighted average of two different paraboloids of revolution A and B. That is, when the formula that defines the paraboloid of revolution A is Z A = f A (X, Y), and the formula that defines the paraboloid of revolution B is Zs = fB (X, Y), the reflecting mirror 1 is Z =ZA m+Za (1m)
Defined in (1). Here, m is the weight of the weighted average. The weight m satisfies 0≦m≦1 and is determined as described below. Note that the x, y, and z coordinate axes are determined as shown in FIG.

Here, as shown in FIG. 2, the paraboloid of revolution A and the paraboloid of revolution B have the same coordinate value at one point P near the center of the reflecting mirror 1 (ZA=211), and The normal vector 2 of the paraboloid of revolution A and the normal vector 2 of the paraboloid of revolution B are set to match. By doing this, the paraboloid of revolution A and the paraboloid of revolution B can be made to almost match in the vicinity of the point P, and can also be made to roughly match over the entire surface of the reflecting mirror 1.

The first group of primary radiators 11, 12, 13.14 are located near the focal point FA of the paraboloid of revolution A, and the second group of primary radiators 2
1 is placed at the focal point F8 of the paraboloid of revolution B.

Now, when the weight m is 1 in equation (1), that is,
When the reflecting mirror 1 coincides with the paraboloid of revolution A (Z=ZA
)think of. At this time, if we consider several rays emitted from point FA, after these rays are reflected by reflector 1 (equal to paraboloid of revolution A in this case), there is no optical path length error, The light ray becomes parallel to the rotation center axis 51 of the paraboloid of revolution A. That is, the beam can be radiated in the direction of the rotation center axis 51 without deterioration in efficiency due to phase errors. Furthermore, when considering several light rays emitted from point FB, these light rays do not become parallel light rays after being reflected by the reflecting mirror 1, resulting in an optical path length error. However, since the reflecting mirror 1 (equal to the paraboloid of revolution A in this case) is approximately equal to the paraboloid of revolution B, the ray becomes approximately parallel to the rotation center axis 52 of the paraboloid of revolution B, and the efficiency due to the phase error is The beam can be radiated in the direction of the rotation center axis 52, although the beam is degraded.

Next, when the weight m is O in equation (1), that is,
When the reflecting mirror 1 coincides with the paraboloid of revolution B (Z=Za
)think of. In this case, the situation is opposite to the above case, and there is no decrease in efficiency due to phase error in the direction of the rotation center axis 52.
Further, the beam can be emitted in the direction of the rotation center axis 51 with a slight decrease in efficiency.

Furthermore, when m=0.5, the reflecting mirror 1 is a paraboloid of revolution A
and the paraboloid of revolution B, and the center axis of rotation 51
The beam can be emitted in the direction of the rotation center axis 52 with almost the same efficiency.

As is clear from the above description, by changing the weight m in the range of 0 to 1, the magnitude relationship of the efficiency of beam radiation in the directions of the central axis 51 and the central axis 52 can be changed. Therefore, the weight m can be determined depending on the magnitude of gain requirements in two different directions.

〔Effect of the invention〕

As explained above, the present invention is composed of a reflecting mirror and a plurality of primary radiators, and the reflecting mirror is a curved surface determined by the weighted average of the coordinate values of two different first and second paraboloids of revolution, These two paraboloids are determined so that they coincide at one point near the center of the reflecting mirror, and their normals coincide at several points, and the plurality of primary radiators are
By arranging it near the focal point of the paraboloid of revolution and the focal point of the second paraboloid of revolution, the entire area of the reflecting mirror can be effectively utilized for the electromagnetic waves corresponding to any -order radiator. Therefore, it has the effect that electromagnetic waves can be emitted in two widely different directions with a relatively small reflecting mirror, and that electromagnetic waves can be received from two widely different directions.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of the present invention, FIG. 2 is a vertical sectional view of the embodiment shown in FIG. 1, and FIG. 3 is a perspective view of an example of a conventional multi-beam antenna. 1... Reflector, 2... Normal vector, 7... Torus rotation axis, 11, 12.13.14... Primary radiator of the first group, 21... Primary of the second group Radiator, 31, 32
゜33.34... Beam radiation direction of the first group, 41...
- Beam radiation direction of the second group, 51.52... Central axis of the paraboloids of revolution A and B.

Claims (1)

[Scope of Claims] The coordinate values of the first and second paraboloids of revolution, whose respective coordinate values and normal lines coincide at one point and are different from each other, are determined by weighted averaging with a weight of 0 or more and 1 or less. The above 1 has a curved surface.
a reflector centered in the vicinity of a point; at least one first primary radiator disposed in the vicinity of the focal point of the first paraboloid of revolution; and in the vicinity of the focal point of the second paraboloid of revolution; and at least one second primary radiator arranged in the multi-beam antenna. 2. The weight value is set based on a ratio between a request for a beam gain corresponding to the first primary radiator and a request for a beam gain corresponding to the second primary radiator. The multi-beam antenna according to claim 1.