JPH11284428A - Primary radiator for parabolic antenna feeding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a primary radiator for parabolic antenna feeding, whose symmetry on the patterns of a face E and a face H in a radiation characteristic is satisfactory, which satisfies the request for characteristics, such as good cross polarized wave characteristic, and a reduced manufacture cost. SOLUTION: In a primary radiator for parabolic antenna feeding, a circular coaxial waveguide 2 having a metallic coaxial bar 5 in the direction of a center axis and transmitting a microwave and a conic flare part 3 connected to the circular coaxial waveguide 2 are installed, and a feed horn 1 which converts a microwave reflected from a parabolic antenna to a transmission mode in the waveguide is provided. The metallic coaxial bar 5 of the circular coaxial waveguide 2 is extended to the flare part 3 of the feed horn 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a primary radiator for feeding a parabolic antenna for receiving microwaves from a broadcasting satellite, a communication satellite, or the like, and more particularly to a feed horn for the primary radiator.

[0002]

2. Description of the Related Art There are several types of feed horns in parabolic antenna devices for receiving microwaves from broadcast satellites and communication satellites, depending on their shapes.

FIG. 4 is a sectional view of a conventional example of a conical horn type feed horn. In this figure, the conical horn type feed horn 1 is composed of a circular waveguide portion 2 and a conical flare portion 3.
Reference numeral 4 denotes an opening surface of the flare portion 3. The conical horn type feed horn 1 configured as described above has an opening 4
Is fixed at the focal position of a parabolic antenna (not shown), so that the microwave coming from a broadcasting satellite or a communication satellite and reflected by the parabolic antenna is received by the flare section 3, and the conical shape of the flare section 3 is obtained. Converts the microwave into a transmission mode in the waveguide, is transmitted through the circular waveguide section 2, and is connected to an LNB (low noise block down converter) (not shown) connected to the other end of the circular waveguide section 2. Transmitted. The LNB performs low-noise amplification and frequency conversion of a weak and noisy microwave coming from a broadcasting satellite or a communication satellite, etc., so that it can be used as a signal of a signal level and frequency that can be easily handled thereafter. It has the function of supplying to vessels.

In the case of the conical horn type feed horn 1, the modes distributed on the aperture surface 4 are circular waveguides TE _11.
The mode is dominant.

There is also a multi-mode horn type feed horn having a plurality of modes. The multi-mode horn type feed horn includes a choke type multi-mode horn type 11 having a circular waveguide portion 12 and a flare portion 13 having a choke structure 15 as shown in FIG. A first circular waveguide portion 22 having a diameter capable of transmitting only the TE ₁₁ mode, which is a mode, and a second circular waveguide portion 24 having a diameter capable of transmitting a TM ₁₁ mode, which is a higher-order mode, are formed into a first circular waveguide. Connected by horn 23,
Further, there is a step type feed horn 21 having a structure having a second horn portion 25, and the like. Note that 14 in FIG. 5 and 26 in FIG. 6 each represent an opening surface.

[0006] In the choke type multi-mode horn 11 shown in FIG.
In the step-type feed horn 21 of FIG. 6, the dual mode excitation of the TE ₁₁ mode and the TM ₁₁ mode occurs in the aperture surface 26.

[0007]

In the directivity characteristics of the antenna, a plane where the electric field is maximum in a plane where the gain is maximum is called an E plane, and a plane where the magnetic field is maximum is called an H plane. Here, in the above-mentioned conventional conical horn type feed horn, in the radiation characteristics, the symmetry of the pattern between the E-plane and the H-plane is not good, and the side polarization level of the E-plane is high. There were problems such as poor sex.
This will be described with reference to FIG. The figure shows that the characteristics of the conical horn are set such that the flare angle (feed angle) is adjusted so that the angle at which the relative gain of the radiation characteristics becomes −10 dB to −12 dB becomes 40 to 45 ° when the aperture diameter a of the feed horn is 40 mm. The horn axis length L) is obtained as a parameter. In this case, symmetry (E-plane, H-plane) can be obtained by in-phase excitation with the amplitude ratio between the TM ₁₁ mode and TE ₁₁ mode set to 20%.
And cross polarization is improved. In the figure (A), TM ₁₁
Since there is no mode and only TE ₁₁ mode,
Although poor symmetry of the radiation pattern of the surface, to TM ₁₁ mode is excited with TE ₁₁ mode in a dual-mode horn in the figure (B), have all the radiation patterns of E-plane and H-plane You can see that. FIGS. 8A and 8B show that the cross polarization characteristics are improved correspondingly to the above.

Regarding the problem of this characteristic, when the TE ₁₁ mode and the TM ₁₁ mode are in-phase excited on the feed horn opening surface at an appropriate excitation ratio, the radiation patterns on the E plane and the H plane become symmetrical, and the cross polarization characteristic becomes poor. It is generally well known that the improvement is achieved as compared with a normal conical horn, and in the conventional multi-mode horn, the above-mentioned characteristic problem is solved by exciting the TE ₁₁ mode and the TM ₁₁ mode to the opening. I was However, in a choke type multi-mode horn as shown in FIG. 5, for example, it is inevitable that the diameter of the feed horn opening becomes large, and the feed horn and the housing of the LNB unit are integrated. In such a case, a large number of die-casting dies are required for the production thereof, so that there is a problem that the cost is increased. In the step-type multi-mode horn as shown in FIG. 6, an increase in the axial dimension of the feed horn is unavoidable due to its structure, and the production cost is high for a consumer product requiring low cost. It was not practical.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the weight and size of a feed horn and to reduce the manufacturing cost while satisfying the above requirements for the characteristics.

[0010]

In order to achieve the above object, the present invention provides a circular coaxial waveguide having a metal coaxial rod in the direction of a central axis for transmitting microwaves. In a primary radiator for feeding a parabolic antenna, comprising a feed horn comprising a conical flare portion connected to a tube and converting a microwave reflected from the parabolic antenna into a transmission mode in the waveguide, the circular coaxial waveguide A primary radiator for feeding a parabolic antenna is characterized in that the metal coaxial rod of the tube extends to the flare portion of the feed horn.

[0011]

As described above, when the TE ₁₁ mode and the TM ₁₁ mode are excited in phase with the feed horn opening plane, the radiation patterns on the E plane and the H plane become symmetrical, and the cross polarization characteristic is smaller than that of a normal conical horn. Be improved.

According to the present invention, in a feed horn having a circular coaxial waveguide having a metal coaxial rod in the central axis direction and a conical flare portion, a structure in which the metal coaxial rod extends to the flare portion. by a primary radiator for a parabolic antenna feed, wherein, to generate a TM ₁₁ mode in the metal coaxial rod tip is made to have an effect, such as to excite the TE ₁₁ mode and the TM ₁₁ mode to the opening surface .

By extending the metal coaxial rod to the flare portion in this way, as shown schematically in FIG. 3, from the tip of the metal coaxial rod 5, the metal coaxial rod is connected to the flare portion as in the present invention. X caused by extending
The TM mode is generated by the axial component Ex. If the diameter of the waveguide is fixed, T
The amount of generation of the M mode will be determined.

[0014]

FIG. 1 shows an embodiment of the present invention, in which a circular waveguide 2 and a conical flare portion 3 are connected, and a substantially central portion in the axial direction of the circular waveguide 2 is provided. The conical horn-type feed horn 1 is constituted by a structure in which the metal coaxial rod 5 extends to the flare portion 3. Since the metal coaxial rod is extended to the flare portion in this way, as described in the section of operation, from the tip of the metal coaxial rod 5,
By combining the component Ex in the x-axis direction and the component Ey in the y-axis direction, a line of electric force Ex-y projecting to the flare portion 3 is generated, thereby generating a TM mode. As described with reference to FIG. Good symmetry of the radiation pattern of the
The feed horn has improved characteristics in which the radiation patterns on the E-plane and the H-plane are uniform, and has improved cross-polarization characteristics as described with reference to FIG.

FIG. 2 shows a second embodiment of the present invention, in which an LNB housing and a feed horn are integrated. In the figure, 1 is a feed horn portion, 2 is a circular waveguide, 3 is a flare portion, 4 is an opening surface, 5
Is a metal coaxial rod, 6 is an LNB front case, 7 is an LNB back case,
Reference numeral 8 denotes an LNB circuit mounting board. One end of the metal coaxial rod 5 is attached to and supported by the LNB front case, and the other end extends to the flare section 3 according to the present invention.

With such a structure, it is possible to reduce the number of die-casting dies of the front housing at the time of manufacturing the feed horn.
The length from the B-circuit mounting board surface to the flare portion can be reduced. The size of the opening may, but taking into account the alignment of the dish there is a need to determine the size of the opening, TM ₁₁ mode can be reduced in size and weight by the size that can be transmitted.

[0017]

As described above, the cost of the LNB circuit for recent satellite broadcasting tends to be reduced as well as reduced. The feed horn of the present invention has the same performance as the multi-mode feed horn by generating a TM ₁₁ mode at the tip of the metal coaxial rod and exciting the TE ₁₁ mode and the TM ₁₁ mode on the opening surface. In addition to being able to secure, the flare section is reduced to a size that can transfer the TM ₁₁ mode, and the flare section has the same structure as a normal conical horn, so there is a great effect that cost reduction can be achieved. Things.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the present invention.

FIG. 3 is a cross-sectional view for explaining the operation of the present invention.

FIG. 4 is a cross-sectional view showing a conventional example of a conical horn.

FIG. 5 is a sectional view showing a conventional example of a choke type multi-mode horn.

FIG. 6 is a sectional view showing a conventional example of a chip-type multi-mode horn.

FIG. 7 is a diagram showing an improvement in characteristics.

FIG. 8 is a diagram showing an improvement in characteristics.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Conical type feed horn 2 Circular waveguide 3 Flare part 4 Opening surface 5 Metal coaxial rod 6 LNB front housing 7 LNB back housing 8 LNB circuit mounting board 11 Choke type multi-mode horn type feed horn 12 Circular waveguide DESCRIPTION OF SYMBOLS 13 Flare part 14 Opening surface 15 Choke structure 21 Step type feed horn 22 1st circular waveguide part 23 1st horn part 24 Circular waveguide part 25 2nd horn part 26 Opening surface

Claims (1)

[Claims] 1. A circular coaxial waveguide having a metal coaxial rod in a central axial direction for transmitting microwaves, and a conical flare portion connected to the circular coaxial waveguide, and reflected from a parabolic antenna. In a primary radiator for feeding a parabolic antenna provided with a feed horn for converting the converted microwave into a transmission mode in the waveguide, a metal coaxial rod of the circular coaxial waveguide extends to a flare portion of the feed horn. A primary radiator for feeding a parabolic antenna, characterized by the following structure.