JPS6242498A - Radio wave absorbing body - 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 [Field of Industrial Application] The present invention relates to a radio wave absorber for suppressing unnecessary reflection and scattering of electromagnetic waves.

[Conventional technology]

When a radio wave absorber used indoors, such as an anechoic chamber, is required to have a wide frequency band as its radio wave absorption characteristics, the shape of the radio wave absorber may be pyramid-shaped or patterned as shown in Figure 4. It is often used after being molded into a shape.

Conventionally, the absorbing material constituting the radio wave absorbing bar has been a foamed resin mixed with carbon, graphite, whole powder, etc. to increase dielectric loss, or ferrite with large magnetic loss.

[Problem that the invention seeks to solve]

However, the nine radio wave absorbers made of a foamed resin mixed with a visiting loss material have weak mechanical strength, and the pyramid must be made larger as the frequency band becomes lower. On the other hand, ferrite ttJ1. According to the absorber, since a large magnetic loss can be utilized in a low frequency band, a relatively small pyramid can be used, but it is expensive, and although it has high hardness, it has the disadvantage of being brittle.

An object of the present invention is to provide a radio wave absorber that has excellent wave absorption properties and is strong enough to be used as a Japanese timber.

[Means to solve the problem]

The present invention does not contain cartilage in base materials such as concrete and mortar.
In a molded body formed into a pyramid shape or seed shape by mixing G E loss material such as carbon, graphite, metal powder, etc., a part of the structure of the molded body is mixed with magnetic loss material such as ferrite, etc.
This is a radio wave absorber characterized by being replaced with (9).

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

Concrete IJ mortar, which is generally used as a construction material, and other base materials are mixed with cargen, graphite, metal powder, etc. to increase dielectric loss, and this is made into a pyramid-shaped or wedge-shaped molded body. Shape. The surface where these are spatially arranged as shown in FIG. 4 functions as a radio wave absorbing wall and has strong mechanical strength, so that it can be used as a wall material for construction. However, an absorber using only dielectric loss needs to be made larger as the frequency band becomes lower.

In the case where the base material is made of foamed resin and has been put into practical use, for example, the height of the pyramid reaches 2 m or more in the case of 30 FvlHz. In the present invention, in order to avoid increasing the size in the low frequency band, FIG. 1 shows a part of the structure of the molded body 1, which is molded into the above pyramid shape or #-1t wedge shape.

As shown in FIGS. 2 and 3, the ferrite molded body 2 has been replaced with a ferrite molded body 2 which has a large magnetic loss in the low frequency band.

With such a configuration, the magnetic loss of the ferrite works efficiently in the low frequency band, and the size of the concrete material can be reduced.

The dielectric loss material using a pyramid-shaped, Vi, or PA-shaped molded body can obtain excellent radio wave absorption characteristics.

As the electromagnetic waves are incident, the volume ratio of the pyramid-shaped or wedge-shaped lossy material in the space gradually changes.
This is due to the gradual change in spatial impedance. As shown in Fig. 1, in a structure in which a part of the structure on the lower surface side of the female Lamirado bottom body 1 is replaced with a ferrite molded body 2 of the same shape, even when electromagnetic waves are incident on the ferrite from the concrete material, the impedance changes are gradual. In addition, in the high frequency band, the magnetic loss of ferrite becomes small, and it has properties 2 of a dielectric material having a dielectric constant equivalent to that of concrete material. Therefore, in the high frequency band, it is equivalent to a pyramid-shaped radio wave absorber using normal dielectric loss.

In the low frequency band, the magnetic loss of ferrite acts effectively and good radio wave absorption characteristics can be obtained.

Another embodiment in which ferrite is inserted into a concrete molded body is shown in FIGS. 2 and 3. FIG. 3 shows a case where a cylindrical or prismatic ferrite molded body 2 is inserted into a concrete molded body 1. In this configuration, it is necessary to adjust the cross-sectional area of the ferrite molded body 2 to equalize the equivalent rust rate and magnetic permeability on the surface where the electromagnetic wave W is incident, and to reduce the surface reflection component. Become. Therefore, the magnetic permeability of ferrite is μ
The area of the incident surface is 6s, and the cross section of the ferrite molded body is adjusted. However, 1 is the dielectric constant of ferrite and concrete. Even in this configuration, ferrite has the effect of improving the radio wave absorption characteristics in the low frequency band.

FIG. 3 shows a configuration in which the ferrite molded body 2 is pyramid-shaped and inserted into the top of the concrete molded body 1 in the opposite direction. In this case as well, as described in FIG. 3, ΔS and S are adjusted so that the equivalent permittivity and magnetic permeability are equal on the plane of incidence of electromagnetic waves.

The method for inserting the shape of the ferrite molded body may be freely selected depending on the actual use.

〔Effect of the invention〕

According to the present invention, since the concrete material occupies most of the volume of the radio wave absorber, it has high mechanical strength and can be used as a building material.Moreover, since a part of the structure is replaced with ferrite, it has a low It has the effect 2 of improving the absorption characteristics of the frequency band.

[Brief explanation of drawings]

Figure 1 is a sectional view showing one embodiment of the present invention, Figures 2 and 3 are
The figures are sectional views showing other embodiments, and FIG. 4 is a sectional view showing a basic type of radio wave absorber. 1... Molded body containing dielectric loss material, 2... Ferrite molded body W... Electromagnetic wave, S... Area of incidence of electromagnetic waves on the molded body, ΔS... Cross-sectional area of ferrite molded body.

Claims (1)

[Claims] (1) In a molded body formed into a pyramid or wedge shape by mixing a dielectric loss material such as carbon, graphite, or metal powder into a base material such as concrete or mortar, a part of the structure of the molded body may be ferrite, etc. A radio wave absorber characterized by replacing the magnetic loss material with a magnetic loss material.