JPH04368009A - Parabolic antenna - Google Patents

Abstract

PURPOSE:To improve the directivity, to surely receive a radio wave from a desired broadcast satellite and to prevent the deterioration in the cross polarized characteristic by selecting a reflecting plate to have an elliptic aperture and selecting a feed horn to be a dual mode horn. CONSTITUTION:A reflecting plate 12 is formed to be an elliptic aperture long in the lateral direction, a feed horn 13 is selected to be an elliptic aperture long in the longitudinal direction and they are formed to be a dual mode horn. When the reflecting plate 12 is selected to be an elliptic aperture long in the lateral direction, the directivity in the horizontal direction is made sharp and since the directivity in the vertical direction is relatively broader, the feed horn 13 into which a radio wave reflected in the reflecting plate 12 is made incident is selected to be an elliptic aperture having the major axis in the vertical direction. Furthermore, since a circularly polarized wave cannot be converted efficiently into an electric signal, the circularly polarized wave is converted into a linearly polarized wave. Thus, a radio wave from a desired broadcast satellite is surely received.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parabolic antenna suitable for use, for example, in receiving satellite broadcasting.

0002

2. Description of the Related Art When receiving satellite broadcasting, a parabolic antenna is used. As shown in FIG. 7, this parabolic antenna includes a reflector 1 and a polarization converter 2 that converts the radio waves reflected by the reflector 1 from circularly polarized waves to linearly polarized waves. This reflecting plate 1 is designed to have a circular shape (having a circular opening) when viewed from a broadcasting satellite. Therefore, the polarization conversion unit 2 also uses a feed horn with a circular aperture to guide the radio waves reflected by the reflection plate 1 to the polarization conversion system.

0003

[Problems to be Solved by the Invention] Since the conventional parabolic antenna has a reflector with a circular aperture as described above,
When multiple broadcasting satellites are placed relatively close together, there is a problem in that it is easy to receive radio waves from unintended broadcasting satellites.

[0004] The present invention was made in view of the above situation, and it is possible to reliably receive radio waves from a desired broadcasting satellite even in a case where many broadcasting satellites are located relatively close to each other. This is to make it possible to do the following.

[0005]

[Means for Solving the Problems] In the parabolic antenna of the present invention, the reflector is composed of a reflector having an elliptical aperture, and the feed horn is an elliptical multimode horn having an ellipse in a direction perpendicular to the direction of the ellipse of the reflector. It is characterized by being composed of.

[0006]

[Operation] In the parabolic antenna having the above structure, the reflector has a horizontally elongated elliptical aperture, the feed horn has a vertically elongated oval aperture, and is a multi-mode horn having a stepped portion in the middle. Therefore, it is possible to reliably receive radio waves from a desired broadcasting satellite without interfering with cross-polarization characteristics.

[0007]

Embodiment FIG. 5 is a side view showing the structure of an embodiment of the parabolic antenna of the present invention. As shown in the figure, in this parabolic antenna, a reflector 12 is attached to a support 11, and a polarization converter 13 is arranged at a position where radio waves reflected by the reflector 12 are concentrated. The polarization conversion section 13 connects the converter section 1 to the converter section 1 via the waveguide 14.
5.

When the reflector 12 is directed toward the broadcasting satellite, circularly polarized radio waves transmitted from the broadcasting satellite are reflected by the reflector 12 and are concentratedly incident on the polarization converter 13 . The polarization converter 13 converts the incident circularly polarized radio waves into linearly polarized radio waves. The radio waves converted into linearly polarized waves are guided to the waveguide 14 and enter the converter section 15. The converter section 15 converts the incident linearly polarized radio waves into electrical signals and outputs them to a tuner (not shown).

As shown in FIG. 6, the reflecting plate 12 is an elliptical aperture reflecting plate having a long axis in the horizontal direction. By setting the horizontal direction as the major axis in this way, it becomes possible to sharpen the horizontal directivity characteristics. Therefore, in cases where a large number of broadcasting satellites are located relatively close to each other,
It becomes possible to reliably receive radio waves from a desired broadcasting satellite.

[0010] When the reflector 12 has a horizontally long elliptical opening as described above, the directivity in the horizontal direction becomes sharp, but the directivity in the vertical direction becomes relatively wide, so that the radio waves reflected by the reflector 12 are not incident. It is necessary that the feed horn (described later) of the polarization converting unit 13 to be converted has an elliptical aperture having a long axis in the vertical direction.

[0011] By the way, radio waves transmitted from broadcasting satellites are circularly polarized waves in order to facilitate the installation of a receiving antenna (so that the receiving antenna can be installed without considering the polarization plane of the radio waves). ing. Since the circularly polarized wave cannot be efficiently converted into an electric signal as it is, this circularly polarized wave is converted into a linearly polarized wave in the polarization converter 13.

[0012] This rotation direction of the circularly polarized waves is used to suppress interference between two broadcasting satellites when they are located relatively close to each other. For example, if Japan uses circularly polarized radio waves that rotate in the right direction, if a South Korean broadcasting satellite is launched and placed in the vicinity, interference from the South Korean broadcasting satellite's radio waves will appear in Japan. In order to prevent interference from the Japanese broadcasting satellite's radio waves from occurring in South Korea, the radio waves from the South Korean broadcasting satellite are circularly polarized in the counterclockwise direction.

However, if the reflecting plate 12 has an elliptical aperture as shown in FIG. 6, the degree of discrimination of the left-handed or right-handed circularly polarized waves becomes poor. That is, for example, even if you try to receive a circularly polarized wave that rotates clockwise (or rotates counterclockwise), it will rotate counterclockwise (or rotate clockwise).
Circularly polarized waves will also be received. This also applies, for example, to the case where a vertically linearly polarized radio wave and a horizontally linearly polarized radio wave are to be distinguished, and the discrimination becomes difficult. That is, the cross-polarization characteristics will deteriorate.

Therefore, in the present invention, the polarization converter 1
As shown in FIGS. 1 to 3, the feed horn in No. 3 is constituted by a multi-mode horn having a vertically elongated elliptical opening.

That is, as shown in these figures, the reflector 1
The feed horn, into which the radio waves reflected by 2 are incident, is composed of parts 21 to 23. The portion 21 is an elliptical opening, and the major axis direction is vertical and the minor axis direction is horizontal. That is, the direction of this ellipse is perpendicular to the direction of the ellipse of the reflecting plate 12 shown in FIG.

A portion 22 having a constant diameter is formed at the back of the portion 21 whose diameter gradually decreases.
A portion 23 is formed further inside 2 so that the cross section is circular and the diameter thereof gradually decreases. this part 2
A stepped portion 25 is formed between 2 and 23, forming a multi-mode horn.

A waveguide 24 having a constant diameter is formed further inside the portion 23. Further inside the waveguide 24, an end plate 26 having a space 27 is arranged. A film substrate 28 is placed in the space formed by the waveguide 24 and the space 27. This film substrate 28, as shown in FIG.
One of the probes (described later) is arranged to face the waveguide 24, and the other probe is arranged to face the waveguide 14.

When formed into a multi-mode horn in this way,
Higher-order modes of the electric field are generated, and the above-mentioned cross-polarization characteristics are improved. That is, for example, when attempting to receive clockwise rotating circularly polarized radio waves, it is possible to suppress the counterclockwise rotating circularly polarized wave component. This makes it possible to compensate for deterioration in cross-polarized wave characteristics due to the use of an elliptical aperture in the reflecting plate 12.

FIG. 4 shows a pattern formed on the film substrate 28. A probe 31, branch portions 32, 33, a coupling portion 34, and a probe 35 are integrally formed on a flexible, extremely thin film substrate 28, made of aluminum, for example. The branch parts 32, 33 and the coupling part 34 constitute a suspended line 42, the probe 31 constitutes a conversion part 41 that converts a waveguide mode into a suspended line mode, and the probe 35
constitutes a converter 43 that converts suspended line mode into waveguide mode.

The probe 31 has a substantially square shape and is arranged at a position corresponding to the waveguide 24 (in the waveguide of the waveguide 24). Branch portions 32 and 33 are connected to one side of the square and the other side perpendicular to the square. The branching parts 32 and 33 are formed to be longer than the branching part 33 so that the lengths of their transmission paths differ by 1/4 of the reception wavelength λ. The other ends of the branch portions 32 and 33 are connected at a connecting portion 34. A probe 35 is further coupled to this coupling portion 34, and this probe 35 is arranged at a position corresponding to the waveguide 14 (in the waveguide of the waveguide 14). In addition, branch parts 32 and 33
A printed resistor 36 is placed in the middle. This constitutes a Wilkinson type synthesis circuit.

[0021] In Japan, the radio waves transmitted by broadcasting satellites are circularly polarized waves that rotate clockwise (right-handed rotation), and these waves are perpendicular to each other, with one phase leading the other by 90 degrees. It is constructed by combining two electric fields. λ/4
The longer branch 32 detects a component whose phase is 90 degrees ahead, as indicated by arrow A in FIG. Detect ingredients. Since the transmission path of the component detected by the branching unit 32 is longer by λ/4, the component detected by the branching unit 33 reaches the coupling unit 34 with a phase delay of 90 degrees than that of the component detected by the branching unit 33. That is, in the coupling section 34, the two components are in phase, so the coupling section 34 and the probe 35 coupled thereto output a linearly polarized wave component. This linearly polarized radio wave propagates within the waveguide 14 and is supplied to the converter section 15. There, it is converted into an electrical signal.

When a pattern as shown in FIG. 4 is formed on the film substrate 28, not only clockwise-rotating circularly polarized waves but also counterclockwise (left-handed) rotating circularly polarized waves are received. Therefore, a printed resistor 36 is arranged to suppress this counterclockwise circularly polarized wave component. By inserting this printed resistor 36, the counterclockwise circularly polarized wave component can be suppressed. Therefore, together with the use of a multi-mode horn, cross-polarization characteristics can be improved.

[0023]

As described above, according to the parabolic antenna of the present invention, the reflector has an elliptical aperture and the feed horn is a multi-mode horn, so the directivity is improved and the radio waves from the desired broadcasting satellite can be transmitted. Not only can reception be ensured, but also deterioration of cross-polarization characteristics can be prevented.

[Brief explanation of drawings]

FIG. 1 is a front view showing the configuration of a polarization converter 13 in the embodiment of FIG. 5. FIG.

FIG. 2 is a sectional view taken along line AA in FIG. 1.

FIG. 3 is a sectional view taken along line BB in FIG. 2;

4 is a diagram illustrating the configuration of a pattern of the film substrate 28 in FIG. 2. FIG.

FIG. 5 is a side view showing the configuration of the parabolic antenna of the present invention.

6 is a front view showing the direction of the ellipse of the reflector 12 and the polarization converter 13 in the embodiment of FIG. 5. FIG.

FIG. 7 is a diagram illustrating the aperture relationship between a reflector and a polarization converter in a conventional parabolic antenna.

[Explanation of symbols]

11 Pillar 12 Reflector 13 Polarization conversion section 14 Waveguide 15 Converter section 21 to 23 parts 25 Stepped section 28 Film substrate

Claims (1)

[Claims] 1. A parabolic antenna comprising a reflector that reflects radio waves and a feed horn that propagates the radio waves reflected by the reflector, wherein the reflector is an elliptical aperture reflector, and the feed horn is a reflector that has an elliptical opening. , a parabolic antenna characterized in that it is an elliptic multi-mode horn having an ellipse in a direction perpendicular to the direction of the ellipse of the reflector.