JPH0216797A - Radio wave absorption device - Google Patents

Abstract

PURPOSE:To improve wave absorption efficiency by propagating reflected wave excepting absorbed wave of wave propagated to a recessed surface of a first wave absorber to a focus position of the recessed surface and by absorbing it again through a second wave absorber. CONSTITUTION:A wave absorption device consists of foam of urethane, styrene form, plastic, etc., whereto carbon powders are impregnated. The wave absorption device consists of a first wave absorber 10 which is provided with a semi- spherical recessed surface of a specified focus distance to a wave incident surface and a second wave absorber 12 consisting of a ferrite magnetic substance arranged at a focus position of the recessed surface. At recessed surfaces 10a, 10b, incident wave diverges to wave lambda' which is absorbed into the absorber 10 and wave lambda'' which is reflected, and the wave lambda'' is concentrated to the focus position. Since the absorber 12 is arranged at the focus position, wave lambda'' is absorbed effectively through the absorber 12. Wave absorption efficiency can be improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a radio wave absorption device, and particularly to a radio wave absorption device suitable for use in an anechoic chamber or the like.

[Conventional technology]

Generally, in anechoic chambers and laboratories that use radio waves, radio wave absorbers are placed on the ceilings, walls, etc. to eliminate unnecessary reflections of radio waves.

Various shapes are used as this radio wave absorber. For example, as shown in FIG. 6, a pyramid-shaped absorber 1 is formed by using urethane as a foam and impregnating the urethane with carbon powder. It is also known that the structure has a similar composition and is formed into an inverted pyramid shape. Furthermore, as shown in FIG. 7, it is also known that a corrugated absorber 2 is formed by impregnating expanded polystyrene with carbon powder and is attached to a fetusite plate 3.

[Problem to be solved by the invention]

However, in any case, the radio wave incident surface of such a conventional radio wave absorber is simply a combination of planar slopes with concavities and convexities.
The incident radio wave λ is divided into the absorbed radio wave λ' and the reflected radio wave λ" on the concave surface of the absorber, and the reflected radio wave λ" is transmitted to the outside of the absorber without reaching the absorber surface again, as shown in FIG. There was a problem in that there was a situation in which it was propagated to

This invention was made in view of the problems of the prior art, and aims to solve the problems by providing a simple and inexpensive structure, excellent radio wave absorption performance, and easy installation. It is said that

[Means to solve the problem]

In order to solve the above problems, the present invention consists of a foam such as urethane, expanded polystyrene, or plastic impregnated with carbon powder, and 1. a first radio wave absorber having a hemispherical concave surface with a predetermined focal length formed on the radio wave incident surface; and a second radio wave absorber made of a ferrite magnetic material disposed at the focal point of the concave surface.
It is equipped with a radio wave absorber.

[Effect]

In the present invention, of the radio waves propagated to the concave surface of the first radio wave absorber, reflected radio waves other than the absorbed portion propagate to the focal position of the concave surface and are absorbed again by the second radio wave absorber. In this way, since radio waves are absorbed in two stages using the principle of a concave mirror, the number of reflections propagating outside the device is significantly reduced, and the radio wave absorption performance is improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 4. This embodiment is applied to a radio wave absorbing device for a wall surface, and FIGS. 1 to 3 show one unit of the radio wave absorbing device, and FIG. 4 shows an example in which a plurality of the units are combined.

1 to 4, 10 is a first radio wave absorber (
1 unit), and 12 indicates the second radio wave absorber.

The first radio wave absorber 10 is made of a foam made of urethane impregnated with carbon powder, thereby providing radio wave absorbing properties. Each of the radio wave absorbers 10 of 1 unit l- is processed into a box shape as a whole, and a hemispherical concave surface 10a with a focal length F is provided at the center of the surface on which the radio waves are incident (radio wave incident surface). At the same time, hemispherical concave surfaces 10b, . Partial recess 10b' divided into four parts
..., 10b' are formed. Here, the radius of each concave surface 10a, 10b is set to a size of, for example, about 1/4 wavelength depending on the wavelength of a single radio wave or a plurality of radio waves used.

That is, in this embodiment, when configuring a wall radio wave absorbing device, a plurality of units of first radio wave absorbers 10.・
. . , 10 are laid adjacent to each other as shown in FIG. 4, whereby large concave surfaces 10a,
..., 10a between small concave surfaces 10b, ..., 10
It constitutes a radio wave absorbing wall supplemented by b. Here, the focal positions of the concave surfaces 10a and 10b are arranged to be on the same plane in the depth direction of the radio wave absorber 10. Further, the back surface of the radio wave absorber 10 is formed as a shield surface.

On the other hand, each of the second radio wave absorbers 12 is made of a ferromagnetic material having radio wave absorption characteristics. This second radio wave absorber 12. ..., 12 is as shown in Fig. 4,
Each row of concave surfaces 10a, 10b in the vertical direction of the wall surface is tied and hung at regular intervals by a string-like member 14 made of nylon or the like, whereby each absorbent body 12 is tied to each concave surface 10a in the vertical direction of the wall surface.
, 10b, respectively. Here, the size of the second radio wave absorber 12 is changed depending on the diameters of the concave surfaces 10a and 10b.

Next, the effects of this embodiment will be explained.

The radio waves arriving at the radio wave absorber (wall surface) of this embodiment are transmitted to the first and second radio wave absorbers 10. ..., 10 and 12.
. . , 12 have radio wave absorption characteristics, so they are well absorbed. In particular, in each of the concave surfaces 10a and 10b that occupy the majority of the radio wave incident surface, the incident radio wave λ is divided into a radio wave λ' that is absorbed into the absorber 10 and a radio wave λ'' that is reflected, as shown in FIG. The reflected radio waves λ″ are collected at their respective focal positions. Since the second radio wave absorber 12 is disposed at each focal point position, most of the reflected radio wave λ'' is well absorbed by the second radio wave absorber 12.At this time, the incident radio wave The direction of incidence does not necessarily have to be perpendicular to the radio wave incidence plane; even if it is oblique, the principle of a concave mirror ensures that it returns to its focal position.

In this way, this example has a two-stage radio wave absorption structure that uses the principle of a concave mirror, so compared to the conventional method, the components reflected from the wall surface and extracted are significantly reduced, resulting in an excellent absorption effect. can get. Moreover, the second radio wave absorber 12 is
Since the size is sufficient to cover the vicinity of the focal point of each concave surface 10a, 10b, the amount of ferrite used is reduced.
This reduces the manufacturing cost and weight of the device. Furthermore, the mounting method differs from the conventional method in that the second radio wave absorber 12. ..., 12 as a string member 14. . . , 14, and is simply hung at each focal point position, which has the advantage of being easy to attach.

Next, another embodiment of the present invention will be described based on FIG. This embodiment shows a case in which a radio wave absorbing device according to the embodiment described above is attached to each of a ceiling, a wall surface, and a floor surface to construct a laboratory, an anechoic chamber, or the like that utilizes radio waves. Here, in the case of a wall surface, the structure is similar to the above-mentioned embodiment, and in the case of a ceiling, an intermediate structure made of nylon or the like is used to support the string-like member 14 on which the second radio wave absorber 12 is arranged at each intermediate point. A support member 16 is interposed between the ceiling surface and the string member 14. Also, on the floor, a second radio wave absorber 12
are directly supported at each focal point by rod-shaped support members 18 made of wood, plastic, etc., which are set upright on the floor.

Therefore, even in this embodiment, the same effects as those of the above-mentioned embodiment can be obtained.

Note that the first radio wave absorber 10 in each of the embodiments described above
Alternatively, foamed polystyrene impregnated with carbon powder may be used. Moreover, the string-like member 14 may be a rod-like member. Furthermore, depending on the purpose of use, either one of the large and small concave surfaces 10a and 10b may be formed. Furthermore, the shape of one unit of the first radio wave absorber 10 is also arbitrary.

〔Effect of the invention〕

As explained above, in the present invention, the first filter having a radio wave absorbing effect. Incoming radio waves are absorbed by the second radio wave absorber, and a hemispherical concave surface is formed on the radio wave incident surface of the first radio wave absorber, and the reflected radio waves from this concave surface are absorbed by the second radio wave absorber. Although the structure is simple, the amount reflected and propagated from the first radio wave absorber to the outside of the device is significantly reduced, resulting in good radio wave absorption performance. It has the effect of being In addition, since the second radio wave absorber can be arranged in a concentrated manner at the focal point of the concave surface, the amount of ferrite used can be reduced, reducing manufacturing costs and weight. It has the effect of being able to.

[Brief Description of the Drawings] Fig. 1 is a front view showing a radio wave absorption surface of a radio wave absorption device (1 unit) according to an embodiment of the present invention, Fig. 2 is a right side view of Fig. 1, and Fig. 3 is a cross-sectional view taken along the line ■-■ in Fig. 1, Fig. 4 is a front view of a radio wave absorbing wall constructed by installing a plurality of radio wave absorbing devices shown in Fig. 1, and Fig. 5 is a diagram showing other aspects of the present invention. FIGS. 6 and 7 are perspective views showing conventional examples, and FIG. 8 is an explanatory diagram showing an example of conventional radio wave reflection. In the figure, 10 is a first radio wave absorber, 10a and 10b are concave surfaces, 10b' is a recess as a part of the concave surface, and 12 is a second radio wave absorber.

Claims (1)

[Claims] (1) A first radio wave absorber made of a foam such as urethane, styrofoam, or plastic impregnated with carbon powder, and having a hemispherical concave surface with a predetermined focal length formed on the radio wave incident surface, and a focal position of the concave surface. A radio wave absorber comprising: a second radio wave absorber made of a ferrite magnetic material disposed in the radio wave absorber.