JPH0550881B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to an antenna system capable of receiving or transmitting left and right circularly polarized waves.

<Prior Art> In recent years, satellite broadcasting has begun to be put into practical use in many countries, and various antennas for receiving satellite broadcasting have been developed.

In particular, for satellite broadcasting using the 12 GHz band, circularly polarized waves are used to avoid interference between channels and interference between broadcast signal waves between countries. Frequency usage allocation has been determined. The location of the satellite in geostationary orbit has also been determined for many countries, and the location of the satellite in the same location, left rotation,
Different satellites transmitting right-handed circularly polarized waves may be deployed.

Under these circumstances, if left-handed and right-handed circularly polarized signals can be received simultaneously or individually using one satellite reception antenna system, more satellite broadcasting signals can be received, which is extremely useful for use. It is valid.

Generally, a satellite reception antenna system consists of one antenna reflector and one primary radiator, and the primary radiator is fixed at one focal point of the reflector.

Conventionally, a fifth radiator consisting of a waveguide phone is fixed at one focal point of the reflector and serves as a primary radiator that receives both left-handed and right-handed circularly polarized waves simultaneously or individually.
There is something like the picture.

The input side of the circularly polarized wave is composed of a circular waveguide 11,
A dielectric plate 12 that delays the wavelength (λ) of a signal passing through the waveguide by λ/4 is fixed at a specific position within the waveguide. Further, the circular waveguide 11 is converted into a rectangular waveguide 13, for example, a left-handed circularly polarized wave.
The LC is taken out from the output terminal 14 as a linearly polarized signal. On the other hand, in the circular waveguide 11 section,
A rectangular waveguide 15 is connected orthogonally to the output terminal 14, and the right-handed circularly polarized wave is extracted from the output terminal 16.

The conventional method requires the circular waveguide 11, the rectangular waveguides 13 and 15, the waveguide converter 17, the dielectric plate 12, etc., which results in a very large size and weight. It is heavy, and in order to extract both circularly polarized waves with one circular aperture, the output terminal 14,
16, the fixed position of the dielectric plate 2, etc.
Its production is extremely difficult.

Therefore, if an antenna system capable of receiving both left-handed and right-handed circularly polarized waves could be easily realized using a very simple method, it would be a very effective means.

<Object of the Invention> The present invention has been made in view of the above points, and combines a reflector having a geometrically asymmetrical shape such as an offset parabolic reflector with left-handed and right-handed circularly polarized primary radiators. The circularly polarized primary radiators are arranged at different positions relative to the reflector, and left-handed and right-handed circularly polarized waves are extracted from each primary radiator. In other words, by utilizing the difference in the reflection directivity (beam) angle of left-handed circularly polarized waves and right-handed circularly polarized waves by an asymmetric reflector, left-handed and right-handed circularly polarized primary radiators are placed at different positions, and the Both circularly polarized signals reflected by the reflector are extracted by the radiator.

In this case, the primary radiator may be any primary radiator specific to left-handed or right-handed circularly polarized waves, but if you use a simple one such as a helical antenna or a double antenna, you can easily create an antenna system. is configured.

In addition to being used for reception, the present invention can also be configured as a transmission antenna system based on the same principle.

<Example> As a typical example of the present invention, an antenna system using an asymmetric offset parabolic antenna in which a part of a paraboloid of revolution is removed will be described.

Figure 3 shows a normal offset parabolic antenna, where 1 is a paraboloid of revolution, 2 is a reflector consisting of a part of the paraboloid, 3 is a primary radiator, B is an incoming electromagnetic beam, and F is a rotating radiator. The focal point of the object plane 1 is shown, and the primary radiator 3 is fixed at its focal point F.

This offset parabolic antenna uses a reflector (reflector plate) that is not rotationally symmetrical, as shown in Figure 3.
This is an antenna in which the primary radiator 3 is placed outside the aperture through which radio waves enter, thereby avoiding blocking by the primary radiator 3. In the case of this antenna, when excited with linearly polarized waves, cross-polarized components are generated due to the asymmetry of the reflecting surface. On the other hand, in the case of circularly polarized waves, there is a 90° phase shift and it becomes a positive polarized component, so cross-polarized waves do not occur, and the direction of the main beam changes between right-handed and left-handed circularly polarized waves. do.

FIG. 4 explains how the direction of the main beam changes. Here, it is assumed that radio waves are emitted from the focal point F, and FIG. 4 shows a view of the offset parabolic antenna seen from above in FIG.
When right-handed and left-handed circularly polarized waves are irradiated from the focal point F, the main beam of the right-handed circularly polarized waves is reflected by the reflector 2 and is directed in the direction of the solid arrow.
The left-handed circularly polarized main beam points in the direction of the dotted arrow. The dashed-dotted arrow indicates the direction of the main beam in the case of linear polarization, which is oriented parallel to the Z-axis of the offset parabolic antenna.

The present invention applies the above-mentioned difference in reflection characteristics of circularly polarized waves, and a specific example thereof is shown in FIG. FIG. 1 is also a diagram of the offset parabolic antenna seen from above.

In Figure 1, 2 is the same reflector as mentioned above, F is the focal point of the paraboloid of revolution (1, see Figure 2),
3R is a right-handed circularly polarized primary radiator, and 3L is a left-handed circularly polarized primary radiator. Right-handed circularly polarized primary radiator 3R
is on the right side of the focal point F (upper side in the figure) on the plane consisting of the Z axis and the Y axis when viewed from above, and the left-handed circularly polarized primary radiator 3L is on the plane parallel to the Z axis and the Y axis. They are fixedly placed on the left side (bottom side in the figure) of the rotational symmetry axis, separated by an angle θ that cancels out the beam deviation due to circular polarization. This angle is the same as the angle θ between the Z axis and the solid arrow or the dotted arrow described in FIG.

With the above configuration, the right-handed circularly polarized wave and the left-handed circularly polarized wave arriving from the same direction as the front (i.e., the Z-axis direction) are reflected by the reflector 2, change the direction of the main beam, and simultaneously or individually transmit the primary radiation. It is received by devices 3R and 3L.

When used as a transmitting antenna, due to the arrangement of each of the primary radiators 3R and 3L as described above, the direction of the main beam of both circularly polarized waves reflected by the reflector 2 is right-handed circularly polarized and left-handed circularly polarized. both in front (i.e., Z
They will be radiated in the same direction (axis).

The primary radiators 3R and 3L may be any primary radiators specific to right-handed or left-handed circularly polarized waves, but small devices such as helical elements and microstrip elements can also be used as the elements. By using these, the system can be configured even more compactly.

In addition, as shown in FIG.
If the asymmetry of the reflector is emphasized by bringing the angle θ closer to the reflector 2, the angle θ shown in FIG. 1 can be made larger. This is both primary radiators 3R and 3L
This is very convenient when fixing the arrangement (see Fig. 1).

Although the above explanation uses a paraboloid of revolution, it can also be implemented in a similar manner using a parallel cylindrical surface.

<Effects of the Invention> As explained above, the present invention utilizes the fact that in a reflector having a geometrically asymmetrical shape, such as an offset parabolic antenna, the radiation beam directions of left-handed and right-handed circularly polarized waves are different. , unique primary radiators for left-handed and right-handed circularly polarized waves are placed at different positions, and both left-handed and right-handed circularly polarized signals coming from the same direction (same geostationary orbit position, etc.) are separated by each radiator. and can be sent or received.

Therefore, in particular, signals with different circular polarization characteristics transmitted from one or more satellites can be received simultaneously by one reflector, and as a primary radiator, it can be used as a left-handed or right-handed radiator. By using a device unique to circularly polarized waves, we have eliminated the need for a complicated primary radiator for both left-handed and right-handed circularly polarized waves, as explained in Figure 5, so in broadcasting satellite receivers, etc. It can be used extremely effectively.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing one embodiment of the present invention, Fig. 2 is a diagram illustrating changes in reflection characteristics showing another embodiment of the present invention, and Fig. 3 is a diagram illustrating a general offset parabolic antenna. 4 are diagrams for explaining the reflection characteristics of circularly polarized waves in an offset parabolic antenna, and FIG. 5 is a schematic configuration diagram of a primary radiator showing a conventional example. 1... Paraboloid of revolution, 2... Reflector (reflector), 3R... Right-handed circularly polarized primary radiator, 3L...
Left-handed circularly polarized primary radiator, F...focal point, θ...angle of change of main beam.

Claims (1)

[Claims] 1. Consisting of a part of a paraboloid of revolution or a parabolic cylinder, the radio wave reflection characteristics are geometrically shaped to provide different radiation characteristics for right-handed circularly polarized waves and left-handed circularly polarized waves. Reflector with an asymmetrical shape
and a right-handed circularly polarized primary radiator and a left-handed circularly polarized primary radiator, near the focal point of the curved surface of the reflector (reflector),
The right-handed circularly polarized primary radiation is placed at two positions in which the directions of the right-handed circularly polarized and left-handed circularly polarized main beams are changed, each by an angle θ that cancels the deviation of the beam due to the circularly polarized wave from the axis of rotation. a left-handed circularly polarized primary radiator and a left-handed circularly polarized primary radiator are respectively fixedly arranged, and right-handed or left-handed circularly polarized waves arriving at the reflector (reflector) from the same direction are divided into the right-handed circularly polarized primary radiator and the left-handed circularly polarized primary radiator. An antenna system characterized by simultaneous or individual reception by radiators. 2. Both circularly polarized waves emitted simultaneously or individually from the right-handed circularly polarized primary radiator and the left-handed circularly polarized primary radiator are reflected by the reflector (reflector plate) and radiated in the same direction. An antenna system according to claim 1.