JPH0426242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a circularly polarized parabolic antenna device used for microwave communications such as receiving satellite broadcasting.

(Summary of the Invention) The present invention provides a circularly polarized parabolic antenna device used for microwave communications such as receiving satellite broadcasting, in which the primary radiator is a single-wire cylindrical shape or has a tapered or flared shape at the end of the cylindrical shape. It uses a backfire helical antenna with

(Prior art) Conventionally, this type of SHF circularly polarized parabolic antenna device used an endfire helical antenna as a primary radiator, as shown in Japanese Patent Laid-Open No. 56-93402. . FIG. 5 shows an example of the configuration in this case. In this figure, an endfire helical antenna 2 is arranged at the focal point of a parabolic reflector 1, and power is supplied to this by a coaxial line 3.

(Problems to be Solved by the Invention) By the way, in the above conventional configuration, the endfire helical antenna 2 is used as the primary radiator.
Since the feeding point is parabolic reflector 1
As a result, the coaxial line 3 is drawn out across the entire surface of the parabolic reflector 1. Therefore, blocking occurs due to the coaxial line 3, and since the coaxial line 3 becomes long, loss is also large. Furthermore, there was also a problem with the support strength of the endfire helical antenna 2.

(Means for Solving the Problems) In view of the above points, the present invention uses a backfire helical antenna as the primary radiator, thereby reducing power loss and blocking.
The present invention aims to provide a parabolic antenna device that can improve mechanical strength.

The present invention arranges a single-wire cylindrical shape or a backfire helical antenna having a tapered or flared end at the end of the cylindrical shape on the focal point side of a reflecting mirror, and connects a coaxial line to the backfire helical antenna. Depending on the configuration,
The above problems have been resolved.

(Function) The backfire helical antenna used in the present invention has directivity toward the feeding point, that is, the main lobe faces toward the feeding point, so the end near the reflecting mirror can be used as the feeding point. . Therefore, when the backfire helical antenna is placed at the focal point of the reflector, the feed coaxial line can be drawn out over the shortest distance on the center axis of the reflector. Therefore, there is almost no blocking caused by the coaxial line, and power loss can also be reduced. Furthermore, structurally, it is easy to ensure the support strength of the backfire helical antenna.

(Example) Hereinafter, an example of a parabolic antenna device according to the present invention will be described with reference to the drawings.

In FIG. 1, a backfire helical antenna 5 is placed at the focal point of a parabolic reflector 1,
A coaxial line (for example, a semi-rigid cable) 6 is connected to a feeding point on the reflector side of this backfire helical antenna 5.

Here, the backfire helical antenna 5 consists of a matching disk 7 connected to the outer conductor 6A of the coaxial line 6 and one spiral connected to the center conductor 6B, as shown in FIG. It may consist of a shaped conductor 8, or it may have a structure as shown in FIG. 2D, omitting the matching disk.

In principle, the current flowing on the line of the helical antenna smoothly travels on the spiral of the helical antenna. Usually, the tip of the helical antenna has a larger reflector than the circumference of the helix (that is, if the entire helix is considered a cylinder, the circumference of the cylinder (hereinafter referred to as the helix circumference)). Electromagnetic waves are emitted from the (endfire helical antenna), but as the circumference of the reflector starts out being slightly larger than the circumference of the spiral, it goes through the same size, and gradually becomes smaller, Electromagnetic waves will be radiated to the (power feeding end side). In other words, a bat clove is produced. The dimensions of the backfire helical antenna are selected with the idea of making active use of this backlobe. Here, the reflecting plate is referred to as a matching disk.

In Fig. 2 A, B, C, and D, S is the circumferential length of the spiral conductor 8, α is the pitch angle of the spiral, c is the circumferential length of the matching disk 7, and β is the taper 8T or flare 8F.
is the angle of

Note that matching between the coaxial line 6 and the helical conductor 8 is performed to reduce reflection between the coaxial line 6 and the helical conductor 8 and to improve V, S, W, and R as an antenna. It is necessary to take The matching can be achieved by appropriately adjusting the distance a between the matching disk 7 and the straight portion 9 of the spiral conductor facing the matching disk 7, or by adjusting the connecting portion between the spiral conductor 8 and the coaxial line 6 ( There are two methods: expanding the shape of the spiral conductor into a tapered shape (conical shape) from the feeding end of the backfire helical antenna and matching it with the circumference S of the corresponding spiral conductor. Of course, improvements can be made by combining these.

The most preferable arrangement of the backfire helical antenna 5 and the coaxial line 6 is when the direction of the helical axis of the backfire helical antenna 5 and the direction in which the coaxial line 6 is drawn out are located on the central axis of the reflector 1. The directivity of the backfire helical antenna 5 at this time, that is, the main lobe MB, is shown, for example, by the dotted line in FIG.

Although not shown in Fig. 2, a single-wire backfire helical antenna has a matching plate at the feeding end, and the feeding end of a spiral conductor wound in a cylindrical shape is tapered. It is also possible to have a structure in which the portion has a flared shape.

Next, the operation of the above embodiment will be explained in the case of reception. Electromagnetic waves incident in the direction of arrow W in FIG. At this time, the backfire helical antenna 5 has a main lobe.
Since the MB is located on the feeding point side, the electromagnetic waves reflected by the reflector 1 are efficiently received by the backfire helical antenna 5. In this case, the backfire helical antenna 5 is
Like normal endfire helical antennas, it exhibits good characteristics when the received electromagnetic waves are circularly polarized.

The parabolic antenna device shown in the above embodiment is
Since the backfire helical antenna 5 is used as the primary radiator used in combination with the reflector 1, the feed point can be set at the end close to the reflector 1, and the coaxial line 6 for power feed can be drawn out at the shortest distance. be able to. Therefore, power loss can be reduced, and there is no need for the coaxial line 6 to cross the front surface of the reflecting mirror 1, so that blocking does not occur. Furthermore, by using a semi-rigid cable, rigid cable, etc. as the coaxial line 6, it can be used as a support for the backfire/helical antenna 5, simplifying the support structure and ensuring sufficient mechanical strength. It's easy. moreover,
It has a simple structure, is suitable for mass production, and is advantageous in terms of miniaturization.

FIG. 3 shows a specific example of a backfire helical antenna, in which a matching disk 7 connected to an outer conductor 6A of a coaxial line 6 and a spiral conductor 8 connected to a center conductor 6B are made of foamed resin. 10 shows a configuration covered by 10. This makes the backfire helical antenna waterproof and prevents the spiral conductor 8 from deforming.

Figure 4 shows a specific example of a helical conductor of a backfire helical antenna, with a cylindrical insulated resin substrate (a flexible substrate bent into a cylindrical shape may also be used).
20 shows a structure in which a conductive pattern 21 made of copper or the like is formed by plating, vapor deposition, etching, or the like. Thereby, it is possible to improve the mass productivity of the spiral conductor.

(Effects of the Invention) As explained above, according to the parabolic antenna device of the present invention, a backfire helical antenna is arranged on the side where the focal point of the reflector is present, and a coaxial line is connected to the backfire helical antenna. Since the backfire helical antenna was used as the primary radiator, power loss and blocking were reduced, and mechanical strength could be improved.Moreover, the structure was simple, and it was suitable for mass production, so it had no practical effects. Extremely large.

[Brief explanation of drawings]

Fig. 1 is a side sectional view showing an embodiment of the parabolic antenna device according to the present invention, Fig. 2 A, B, C, and D are side sectional views showing the backfire helical antenna used in the embodiment, and Fig. 3. 4 is a side sectional view showing a specific example of a backfire helical antenna, FIG. 4 is a perspective view showing a specific example of a spiral conductor in a backfire helical antenna,
FIG. 5 is a side sectional view of a conventional parabolic antenna device. 1... Parabolic reflector, 5... Backfire helical antenna, 6... Coaxial line, 7...
Matching disk, 8... Spiral conductor, 10... Foamed resin body, 20... Cylindrical insulating resin substrate, 21... Conductive pattern.

Claims (1)

[Claims] 1. A single wire type backfire helical antenna wound into a cylindrical shape is arranged on the side where the focal point of the reflecting mirror is present, and a coaxial line is connected to the backfire helical antenna. Parabolic antenna device. 2. The parabolic antenna device according to claim 1, wherein the single-wire backfire helical antenna has a matching plate at its feeding end. 3. The parabolic antenna device according to claim 1, wherein the single-wire backfire helical antenna has a tapered feeding end. 4. The parabolic antenna device according to claim 1, wherein the single-wire backfire helical antenna has a flared tip. 5. Claim 1, wherein the single-wire backfire helical antenna has a matching plate at the feeding end, the cylindrical feeding end is tapered, and the tip has a flared shape. Parabolic antenna device described. 6. The parabolic antenna device according to claim 1, wherein the single-wire backfire helical antenna is located at the focal point of the reflecting mirror, and the coaxial line is installed on the central axis of the reflecting mirror.