JPH0441603Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The present invention relates to an antenna mounted on a broadcasting satellite, and in particular to a reflector for an antenna that obtains a shaped beam, which is composed of a single reflector and a primary feeder. be.

(Prior Art) Satellite broadcasting is an indispensable technology for resolving the difficulty of viewing television broadcasting, and is a large medium that will include more advanced television broadcasting technology in the future.

At the World Radiocommunication Administration Conference (WARC-BS), held from January 10 to February 13, 1977, each country's operations for the purpose of individual reception by broadcasting satellites were
This is possible only in the 12GHz band, and the frequency channels and orbital positions of broadcasting satellites using the 12GHz band are subject to change in the first region (Europe and Africa).
and to each country in the third region (Asia and Oceania).

For example, Japan was able to acquire eight waves at 110 degrees east longitude, but the WARC
- Radiation directivity compliant with BS standards was required.
Current broadcast satellite antennas provide 12G with right-handed circular polarization.
In the Hz band, most of mainland Japan has a gain of 37 dB or more,
All over Japan, including the Ogasawara Islands, Okinawa, and the Nansei Islands.
A shaped beam with coverage of 28 dB or more is required.

The conventional method for forming shaped beam directivity in order to satisfy the above conditions is a multi-beam method that combines the beams obtained by feeding power to three horns. A beam is formed by each horn, and an offset parabolic reflector is used to obtain side rope characteristics that comply with WARC-BS. distance is 85
cm.

For details of this antenna, see, for example, the literature Kajikawa et al. “Development of antenna for broadcasting satellite No. 2 (Characteristics of BBM)” IEICE Technical Report, Vol. 82, No. 80, A.P82-48,
See 1982.

Another embodiment other than the above is a feed cluster method, which is a further subdivision of the multi-beam method. For details, see, for example, Reference J.
Ramasastry et al. “Technical and Regulatory
Aspects of Satellite Broadcasting”the US
Situation, Space Communications and
See Broadcasting, Vol. 1, No. 4, 1983.

(Problem to be solved by the invention) In the shaped beam using the multi-horn method described above, when trying to increase the degree of shaping, the radio waves emitted from the primary horn leak beyond the boundaries of the reflecting mirrors, which is called spillover. As a result, the gain decreases, and if the gain is maintained, the beam spacing becomes too wide, resulting in insufficient beam shaping to suit a service area with a special shape like Japan.

In addition, the method of obtaining a shaped beam using a feed cluster requires a complicated and large power supply circuit.
Due to weight limitations, it is not suitable for satellite antennas that handle large amounts of power.

(Means for Solving the Problems) The present invention was made in order to satisfy the WARC-BS standard for the side lobe characteristics of cross-polarized waves of circularly polarized waves, and to overcome the problems that conventional techniques had. This method uses a primary feeding horn with a relatively simple structure (for example, an elliptical corrugated horn) and shifts a portion of the reflector to change the shape of the area where the gain is high near the center of the radiation beam cross section. , for example, to provide a radiation pattern that more closely matches the shape of Japan.

That is, the reflector-shifted antenna of the present invention is an antenna composed of a feeding horn and a paraboloid of revolution reflector, in which the paraboloid of revolution reflector has an elliptical cross section when viewed from the propagation direction of reflected radio waves. of,
The elliptical cross section is divided into three parts in parallel to the major axis direction, and the divided central part of the strip is shifted parallel to the major axis direction of the elliptical cross section or rotated around the minor axis of the elliptical cross section to obtain the obtained result. The present invention is characterized in that a pattern shape is obtained by expanding an elliptical radiation pattern in the short axis direction.

(Examples) The present invention will be described in detail below by way of examples with reference to the accompanying drawings.

FIG. 1 shows a perspective view of the entire antenna according to the present invention and a corresponding diagram for explaining the principle of beam forming. In Fig. 1, the radio waves emitted from the primary feeding horn 1 are reflected by the reflecting mirror surface 2 and directed toward the earth. It has a structure in which the central part 2b is shifted parallel to the major axis direction of the aperture ellipse (shifted to the upper right in the figure) or slightly rotated around the minor axis of the aperture ellipse (parallel). Although there is a difference in the manner of deviation between deviation and rotation, they are almost the same in terms of drawing.In this invention, parallel deviation and rotation are collectively referred to as deviation.) Note that the boundaries of the three portions 2a, 2b, and 2c are continuously connected.

Therefore, the radio waves reflected from the parallel-shifted or rotated central portion 2b of the reflector create an oblong radiation pattern 3b on the earth, and the radio waves reflected from the upper and lower portions 2a and 2c of the reflector. creates a circular radiation pattern 3a on the earth. The combination of both forms the radiation pattern 3c of this mirror-shifted antenna, which changes from an elliptical shape to a shape that bulges in the direction of its short axis.

Fig. 2 is a front view of the paraboloid of revolution reflector 2, which is the starting point of the present invention, and parts 2a to 2e show how the paraboloid of revolution is divided into strip parts parallel to the major axis direction A ₁ A ₂ . The portion 2b (center) is a shifted portion, and the portions 2d and 2e are portions that gently and continuously connect the portions 2a, 2c and the portion 2b.

FIG. 3 is a cross section of the axis A ₁ -A ₂ of the front view of the second illustrated paraboloid of revolution reflecting mirror 2, where the solid line in the figure is the paraboloid of revolution 4a, and the broken line is the specular shift reflecting mirror according to the present invention. 4b
(The parallel shift and rotation are almost the same in terms of drawing as in Figure 1).

Further, FIG. 4 is an x-axis sectional view of the front view shown in the second figure, in which the solid line in the figure indicates the paraboloid of revolution 5a, and the broken line indicates the mirror shift reflecting mirror surface 5b according to the present invention (this is also 2 (the two deviations are almost the same), and also the fifth
The figure shows the amount of parallel movement in the y direction of the parts 2b, 2d, and 2e shown in the second figure in the deflection reflector according to the present invention (in the case of rotational shift, the horizontal axis of the figure is Δz instead of Δy). If so, they will be almost identical in terms of drawing).

From FIG. 2 to FIG. 5, the detailed shape and dimensions of the specular shift reflector of one embodiment of the present invention are almost clear, but of the two shifts, only the parallel shift will be listed in detail. , the reflecting mirror is 1900 mm x 900 mm, and the focal length (f) is ₉₀₀ mm, and the deflection mirror surface is a strip-shaped part parallel to the y-axis (x ₃ < x <x ₄ ) along the y-axis, and the shifted mirror surface portions (portions 2b, 2d,
The shape of 2e) is given by the following equation.

z = x ² + (y - Δy) ² /4f - f Furthermore, x ₃ = 320mm, x ₄ = 720mm, x ₅ = 370mm, x ₆
= 670 mm, the maximum value of Δy is -5 mm, the blowing angle of the primary feeding horn θ ₀ = 32.4° (Fig. 4), the lower edge angle of the mirror surface θ _a =
6.6° (Fig. 4), the primary feeding horn at this time is an elliptical corrugated horn with an aperture of 87.5 x 31 mm.

(Effect of the invention) In order to show the effect of the invention, Fig. 6 shows the radiation pattern (solid line) of the reflective mirror-shifted antenna according to the embodiment of the invention.
This shows a superimposed map of Japan as seen from a broadcasting satellite. The figure also shows the radiation pattern (dashed line) of a paraboloid of revolution reflector antenna (reflector aperture 1700mm x 800mm, focal length 900mm). By using a reflective mirror-shifted antenna, a gain increase of 1 dB in Japan's metropolitan area and 0.6 to 0.8 dB in other major cities has been achieved compared to a rotating paraboloid antenna.

[Brief explanation of drawings]

Figure 1 shows a perspective view of the entire reflective mirror-shifted antenna, which is the invention, and a diagram for explaining the principle of beam forming. A front view of the parabolic reflector is shown, FIGS. 3 and 4 respectively show the axis _A1 - _A2 and X-axis cross section of the second shown front view, and FIG. 5 shows the second shown portion 2b, The amount of parallel movement of 2d and 2e in the y direction is shown, and FIG. 6 shows a map of Japan superimposed on the radiation pattern of the antenna. 1...Primary feeding horn, 2...Reflector, 2a,
2b, 2c, 2d, 2e...respectively reflecting mirror parts, 3a, 3b, 3c...respectively radiation patterns, 4a, 5a...respectively paraboloids of revolution, 4b, 5b...
Shift reflective mirror surface.

Claims (1)

[Scope of utility model registration request] In an antenna composed of a feeding horn and a paraboloid of revolution reflector, the paraboloid of revolution reflector has an elliptical cross section when viewed from the propagation direction of reflected radio waves, and the paraboloid of revolution reflector is arranged in the major axis direction of the elliptical cross section. The elliptical cross section is divided into three parts in parallel, and the divided center part of the elliptical cross section is shifted parallel to the major axis direction of the elliptical cross section or rotated around the minor axis of the elliptical cross section, and the resulting elliptical radiation pattern is A reflective mirror-shifted antenna characterized by being able to obtain a radially expanded pattern shape.