JPS624400A - Antenna for microwave - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a microwave antenna, and in particular, to a microwave antenna.
Concerning measures to improve the back ratio.

(Technical background) In long-distance microwave wireless communication systems, it is necessary to amplify signals by installing relay stations (not shown in Figure 6) at regular intervals to compensate for propagation loss in the propagation path. . In this case, the receiving antenna and the transmitting antenna are often placed facing each other as shown in FIG.

The following issues arise here. Some of the incident radio waves or radio waves from the ground may be received by the transmitting antenna rather than by the receiving antenna. To express this difference, the f, b meter is used to express the Freon 1-back ratio. To maintain good communication quality,
It is said that it is desirable that the feedback ratio is 60 dB or more.

On the other hand, in Shintsu's metal parabolic antenna, A is calculated using the following formula.

f, b Δ = G + (10 to 13) [d [3] [1b Here G is the antenna benefit 19° Therefore, if G is increased, Δ is 60f, b It is possible to increase the number to 68 or more.

However, G is related to the aperture of the parabolic antenna, and increasing the aperture means that the weight of the antenna system will increase, which means that it will be necessary to cover a large amount of the steel tower to hold it, and the antenna system will be As the aperture increases, it becomes increasingly difficult to increase the surface area, which is often disadvantageous from an engineering perspective.

Currently, horn reflectors are used to increase the A to 60 dB or more, but these are also heavy and require large towers, making them unsuitable for performance.

Therefore, it is possible to improve the front-back ratio by a method other than antenna gain, for example, as shown in Fig. 8(a).
The method shown in FIG. 9 (b) is adopted.

Of these, those shown in FIGS. 8(a) and 8(b) are the outer periphery 1 of the parabolic metal plate 1 attached to the parabolic antenna. Radio wave absorbers 2 and 2' are provided at the outer edge 1a of the parabolic metal plate to attenuate the current at the outer peripheral edge 1a of the parabolic metal plate. The radio wave absorber can be used as two scales as shown in the figure or as a single type. And the monthly interest rate is Gomufuerai]
- is suitable, but the thickness must be approximately 8 mk:'l, which causes the problem of considerably increasing the weight of the antenna.

Also, Figure 9 shows the sub-tank tAi that goes down to Karegren Andeno.
The flare plate 4 is set at a set number in order to cancel out the anti-reflection from the stay for supporting n. This flare 8211 has a shape determined by complicated calculations and is difficult to produce.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and therefore, Freon 1
- It is an object of the present invention to provide a microwave antenna that has a good back ratio, a small flip-flop, and is easy to install.

(Summary of the Invention) In order to achieve this object, the present invention uses an electromagnetic wave absorber (hereinafter referred to as a new absorber) made of a mixture of ferrite powder, carbon powder, and a binder such as rubber to replace the conventional rubber film.
Focusing on the fact that the thickness of the rim R'J has good electromagnetic wave absorption characteristics, this microwave antenna is made by attaching the above new absorber to a part of the antenna that should not be exposed to T5 magnetic waves. It is composed of ′! 1. That is, the above-mentioned electromagnetic wave absorber has a weight mixing ratio F of ferrite powder and carbon powder to binder 1 determined by the following formulas (1) and (2).

and C.

F, L: (24,3-5,41o(l II') /
r (G112)・・・・・・・・・・・・・・・
...(1)C6ζ(1,65/(t-1,4))
−0,252,4≦and≦8.0 (mm) ・・・・・・・・・・・・・・・・・・(2) Here μ
is a fly before powdering! The permeability f of ~ is the absorption frequency (G
'1-IZ) t is the thickness of the radio wave absorber (mm) And by adopting this configuration, it is possible to reduce the weight of the Antep City ■ while maintaining a good J:Riff 1-Con 1-Back ratio.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to FIGS. 1 to 5.

FIG. 1 shows an embodiment of a parabolic antenna, where 1 is a parabolic metal plate, and the new absorber 2A (J&) is attached to the outer periphery of this parabolic metal plate 1.

This new absorber 2A has a groove shaped to fit into the 1iIIIi-plane circular bend formed on the outer periphery of the parabolic metal plate 1, and the new absorber 2A itself has a certain degree of flexibility. : Has elasticity. Therefore, fitting the new absorber 2A to the outer peripheral edge of the parabolic metal plate 1 is easy.
You can get 1.

This J: New absorber 2A on the outer periphery of the sea urchin parabolic metal plate 1
When the parabolic metal plate 1 is attached (), a current induced by electromagnetic waves will no longer flow through the outer peripheral edge of the parabolic metal plate 1. Therefore, it is possible to prevent the current flowing on the outer peripheral edge surface of the parabolic metal plate 1 from going around to the back side and generating an electromagnetic field from the back side.

Figures 2 and 3 show examples of Casegrain antennas. It is necessary to suppress the reflection caused by 3. That is, electromagnetic waves from the tJ4 emitter are reflected by the sub-reflecting surface 5, reflected by the main reflecting surface 3, and electromagnetic waves heading for the next station are reflected by the stay 3. In this case, vertically polarized waves and horizontally polarized waves are included.

Therefore, a new absorber 4A is installed around the stay 3 to suppress electromagnetic wave reflection from around the stay 3.

At the same time as suppressing reflection from the stay 3, electromagnetic wave radiation from the back surface of the main reflective surface can be prevented by providing a new absorber 2A on the outer peripheral edge of the main reflective surface as shown in FIG.

FIG. 4 J3 and FIG. 5 show detailed structural examples of the new absorber 2△ attached to the outer peripheral edge of the parabolic reflecting surface 1. First, in the example shown in Fig. 4, in addition to the groove A that fits into the outer peripheral edge of the parabolic reflecting surface, a groove 8 is provided in the new absorber 2A to fit the collar 6 made of rubber or the like. Oki, iM
By fitting the outer peripheral edge of the parabolic reflecting surface into A and pushing the stopper 6 into the outer circumferential edge 8 (I) of the parabolic reflecting surface 1, the new absorber 2A is firmly fitted into the outer peripheral edge 8 (I) of the parabolic reflecting surface 1. In the example, in advance, a member 7 such as an iron lobe is inserted into the groove where the outer peripheral edge of the parabolic reflecting surface 1 of the new absorber T42A is located, and the open end of the groove is pushed wide, and the outer peripheral edge of the parabolic reflecting surface When the member 7 is bitten to a certain extent, the parabolic reaction occurs due to the return elasticity of the new absorber 2A.
Attach to side 1.

In the examples shown in FIGS. 4 and 5, the new absorbent body 2A will definitely have a joint. Since this joint can cause rainwater to enter, it is best to place it at the bottom in the installed state, or in the case of the example shown in Figure 4, use the suppression by the stopper 6 to prevent gaps from forming at the joint. do it like this.

The new absorbent used in the present invention has the following differences in characteristics compared to conventional rubber fluorite.

Rubber ferrites 1 to 1 are made by using rubber as a binder and mixing ferrite powder, and their radio wave absorption characteristics have been studied in detail. When a flat plate of rubber ferrite is lined with a metal plate and a plane radio wave is incident from the surface,
When the frequency is 4 GHz or less, the thickness is about 8 nm, and when the frequency is 4, GH2 or more, it absorbs radio waves of f G l-12.

There was a limit to the thickness of this sea urchin.

However, in a new absorber made using rubber as a binder and ferrite powder and new carbon powder added as described in the present invention, it was found that the thickness d became thinner as shown in Figure 10 due to the addition of carbon powder a. . The example shown in FIG. 10 uses ferrite powder made from a material with a magnetic permeability of 2700, and is mixed in a weight ratio of 1 to 1 to ferrite: carbon powder: binder: -3:x:1. x = O is dlll = 8 for the conventional rubber die 1, but when X is increased, dl and l become thinner, and when X = 1.2, 2
．． It can be seen that it becomes thinner to 4na.

Therefore, less material is needed for the same purpose, and at the same time the cost is lower because carbon is cheaper than ferrite.

〔Effect of the invention〕

As described above, the present invention configures a microwave antenna by attaching an electromagnetic wave absorber made of a mixture of ferrite powder, carbon powder, and rubber in a predetermined ratio to a part of the antenna that should not be affected by electromagnetic waves. It is possible to provide a lightweight antenna while maintaining a good back-to-back ratio.

[Brief explanation of drawings]

Fig. 1 is a vertical cross-sectional view of an embodiment of the present invention regarding a parabolic antenna, and Figs. Figures 1, 4 and 5 show details of the part 1 for attaching an electromagnetic wave absorption shield to the outer periphery of a parabolic antenna.
Figures 6 and 7 are diagrams showing application examples of the antenna according to the present invention, and Figures 8 (a) and (b) do not show the IIIa structure.
and Figure 9 shows an example of a conventional microwave antenna.
10 are absorption characteristic diagrams of the new absorbent used in the present invention. 1... Parabolic metal plate (parabolic anti-DI ti),
2.2△, 4A...electromagnetic wave absorber, 3...stay for supporting sub-reflector. Applicant's agent Kiyoshi Inomata Figure 2 Figure 5 Figure 6 Figure 7 Figure 9 Figure 10

Claims (1)

[Claims] 1. Ferrite powder, carbon powder, and binder are mixed at a weight mixing ratio Fp determined by the following formulas (1) and (2), with the binder being 1, and carbon powder at Cp. A microwave antenna whose parts that should not be exposed to electromagnetic waves are covered with a mixed electromagnetic wave absorber. 2. A microwave antenna according to claim 1, wherein the electromagnetic wave absorber is attached to the outer peripheral edge of a parabolic antenna. 3. A microwave antenna according to claim 1, wherein the electromagnetic wave absorber is provided around a stay for supporting a sub-reflector of a Cassegrain antenna.