JP2553585B2 - Offset satellite dish - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an offset parabolic antenna for transmitting and receiving microwave signals.

2. Description of the Related Art As a conventional technology, for example, “Satellite Broadcast Reception Guide” edited by the Television Reception Improvement Committee (November 1983), Japan Broadcast Publishing Association, page 80, is shown in FIG. (B)
Shows the outline of the offset parabolic antenna. A is a perspective view and B is a diagram for explanation. Here, reference numeral 1 is a parabolic reflector, which reflects a radio wave coming from the direction of the arrow and focuses it on the primary radiator 2 at the focal point. Reference numeral 3 is an input terminal of the primary radiator 2, and 4 is an output terminal. A communication device such as a waveguide or a frequency converter is connected to the output terminal 4. Reference numeral 5 is called the projection surface of the parabolic reflector 1. The primary radiator 2 is located outside this projection surface 5 so as not to obstruct the passage of radio waves. I call it an antenna.

An example of a conventional primary radiator is shown in FIG. A is a perspective view and B is a cross-sectional view. Here, a horn antenna whose inner diameter is gradually increased is used as the primary radiator. Reference numerals 2, 3 and 4 are as described above, and reference numeral 6 is a metal portion forming a horn antenna through which radio waves pass. Reference numeral 7 is a ring-shaped groove, and the number of link-shaped grooves 7 is experimentally determined so that optimum values of directivity and antenna gain can be seen. Reference numeral 8 is a resin case for preventing foreign matter such as rainwater and dust from entering through the input terminal of the horn antenna. This resin case 8
The thickness of is as thin as 0.5 mm to 1 mm, and the flatness is not good, so
Often, a gap 9 is apt to occur apart from the metal portion 6.
FIG. 6 shows a state in which the gap 9 is generated.

Problems to be Solved by the Invention Here, the results of measuring the return loss characteristics from the output terminal 4 of the primary radiator are shown in FIG. 7, where A is a case 8 of normal resin and B is a gap 9. This is the case. The return loss characteristic is deteriorated due to the gap 9. Therefore, a primary radiator having a structure in which the return loss characteristic does not deteriorate is desired, and the present invention provides an offset parabolic antenna in which the return loss characteristic does not deteriorate.

Means for Solving the Problems In the primary radiator of the offset parabolic antenna of the present invention, a thin case of low-loss resin attached to the input terminal of the horn antenna is bent inside the input terminal. It has a different structure. The diameter of the resin case to be deformed is slightly larger than the diameter of the input terminal of the horn antenna. The depth of the horn antenna is about 1 mm.

Function The resin case is deformed so as to bend inward from the input terminal, and the circle and diameter for deformation are made larger than the diameter of the horn antenna input terminal. Therefore, when the resin case is attached to the primary radiator, The resin case will always adhere to the tip of the metal part of the secondary radiator. That is, there is no gap between the two, and the return loss characteristic can be improved.

Embodiment A primary radiator of an offset antenna according to an embodiment of the present invention will be described below with reference to FIG. The diameter of the output terminal 4 of the primary radiator 2 is 17.5 mm, and the length is arbitrary. The horn antenna spreads at an angle θ of about 35 degrees, and the diameter of the input terminal 3 is about 33.
mm. The ring-shaped groove 7 has a depth of 6.1 mm and a width of about 3 mm. Here, the resin case 8 is gently bent inward by about 1 mm from the point indicated by the diameter A larger than the diameter B of the input terminal 3 in the direction of the arrow C. Then, when the horn antenna is pushed over, the inside corner D of the resin case 8 matches the outside corner E of the primary radiator 2, and the resin case 8 is held. At this time, at the input terminal 3 of the horn antenna,
Since the resin case 8 is bent toward the horn, the two are always in close contact at point B.

Another embodiment of the present invention is shown in FIG. Here, 10 is a stopper, which is a ring-shaped projection protruding inside the resin case 8. Reference numeral 11 is a groove in which a part of the metal portion 6 of the primary radiator 2 is recessed in a link shape. Compared to the embodiment of FIG. 1, the primary radiator 2 has a number of ring-shaped grooves 7 and
Although 11 has changed, the dimensions of the horn antenna part are the same. Compared to the embodiment shown in FIG. 1, the resin case 8 has a straight portion from A to D that is bent, the DD surface is flat, and the depth is about 1 mm. Where the resin case 8 is C
When pushed in the direction, the stopper 10 of the case 8 is inserted into the groove 11 to hold the resin case 8. At this time, the portion of the input terminal 3 of the horn antenna is always in close contact with the point B. It should be noted that the material of the resin case 8 of the embodiment can be practically used, such as Teflon, polyethylene, or polypropylene, which causes little loss of microwaves. The return loss characteristics measured from the output terminal 4 of these two examples are almost unchanged, and the characteristics are shown in FIG. Here, A is a case in which a flat plate-shaped case having no deflection is brought into close contact, and B is a case in which there is deflection and brought into close contact. B is slightly smaller, but the characteristics are improved.

As described above, according to the present invention, when the horn antenna is used as a primary radiator and its wide input terminal is covered with a low-loss resin case, the case is placed inside the horn antenna from the input terminal. By flexing the structure, the case inevitably comes into close contact with the horn antenna, and an offset parabolic antenna having a good return loss characteristic can be provided.

[Brief description of drawings]

1 and 2 are cross-sectional views of a primary radiator of an offset parabolic antenna according to an embodiment of the present invention, respectively.
The figure is a characteristic diagram of the return loss of the present embodiment, a schematic diagram for explaining the parabolic antenna of FIGS. 4A and 4B, an exploded perspective view and a sectional view of a conventional primary radiator of FIGS. 5A and 5B. FIG. 6 is a sectional view of a conventional example, and FIG. 7 is a characteristic diagram of return loss of the conventional example and a primary radiator. 1 ... Parabolic reflector, 2 ... Primary radiator, 3 ... Primary radiator input terminal, 4 ... Primary radiator output terminal, 6 ...
… Metal part, 7 …… Ring-shaped groove, 8 …… Resin case.

Claims (1)

(57) [Claims] 1. A horn antenna is used as a primary radiator,
While covering the wide input terminal with a low-loss resin case, bend the case toward the inside of the horn antenna from the above input terminal, and the diameter of the bend is greater than the diameter of the input terminal. An offset parabolic antenna characterized by being enlarged.