JPH06334382A - Wave absorber - Google Patents

Abstract

PURPOSE:To contrive the improvement of the wave absorption performance of a wave absorber by a method wherein a plurality of conical body type recesses, whose axes are arranged almost vertically to the surface of the absorber, are provided in the surface of the wave absorber made of a blowing plastic impregnated with a carbon black. CONSTITUTION:A wave absorber 1 having quadrangular conical body type recesses 2, whose axes are arranged vertically to a surface (b) and whose bases are adjacent to each other, is formed. The absorber 1 is made of a blowing material, such as a polyurethane, a blowing styrole and a plastic, impregnated with a carbon black, that is, a blowing plastic. In this structure, an electrical radiation intrudes (a) almost vertically to the surface (b). The area of the surface of the absorber 1 is the area of a lattice-shaped part shown by 3 and the adjacent quadrangular conical body type recesses 2 are provided in such a way that they come into contact to each other, whereby a fully small value can be given to the area of the surface of the absorber 1. The electrical radiation entering into the absorber 1 having the fully small surface area intrudes in the interior of the absorber while being made to repeat a plurality of times of reflections by the slant faces of the recesses 2 and is converted into a heat energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic wave absorber used for an inner wall surface of an anechoic chamber.

[0002]

2. Description of the Related Art EMC (Electro Magnetic Compatibili
ty) An anechoic chamber is widely used as a facility for evaluation, and in general, a plurality of cone-shaped, triangular-pyramidal, or quadrangular-pyramidal electromagnetic wave absorbers are placed on the walls, ceiling, or floor of the anechoic chamber. There is. Such a radio wave absorber is made of expanded polystyrene containing carbon black, polyurethane foam containing carbon black, or the like.

FIG. 5 shows a first example of a quadrangular pyramid (sramid type) absorber 01. The reason why the radio wave absorber is in the shape of a cone, a triangular pyramid, a quadrangular pyramid, or the like is to gradually increase the cross-sectional area of the radio wave absorber in accordance with the progress a of the radio wave. That is,
If the cross-sectional area of the surface of the radio wave absorber (direction of arrival of radio waves) is small, the equivalent electric conductivity and permittivity there will be small, and the reflection of incident radio waves on the surface will be suppressed, so that the radio waves will enter Radio waves that enter the absorber easily enter the absorber and are efficiently converted into thermal energy and absorbed by the space containing the absorber whose conductivity and dielectric constant are equivalently increased as the absorber cross section gradually increases.

A second example of the absorber 02 is shown in FIGS. 7 and 8. A plurality of wedge-shaped radio wave transparent materials 03 that fit into the valleys d of the wave-shaped radio wave absorber 02a are inserted to form cone-shaped recesses as shown in FIG. As a result, the radio wave absorber 0
The shape of 2a is retained. In addition, the function is almost the same as above, and the radio wave is absorbed.

[0005]

The performance of the radio wave absorber of the above-mentioned first example largely depends on the height of the cone, and the height is generally 1/2 to the wavelength of the radio wave to be absorbed. 1/3
More is needed. For example, frequency 50MHz
The height of the pyramid in FIG. 5 for absorbing the radio wave of (wavelength 6 m) becomes 2 to 3 m, and when it is attached to the wall surface, the tip hangs down due to its own weight and the cone is deformed as shown in FIG. However, there is a problem that the desired electromagnetic wave absorption performance cannot be obtained.

Further, the radio wave absorber 02 of the second example is not so good in absorption performance because the wedge-shaped radio wave transparent material 03 does not absorb radio waves. Further, since many transparent materials 03 have to be inserted and adhered, there is a problem that the number of manufacturing steps is increased.

[0007]

The present invention takes the following means in order to solve the above problems.

That is, in a radio wave absorber made of foamed plastics impregnated with carbon black, a plurality of cone-shaped recesses whose axes are arranged substantially vertically are provided on the surface thereof.

[0009]

In the above means, the radio wave propagates almost perpendicularly to the surface of the radio wave absorber. The cone-shaped recess sufficiently reduces the cross-sectional area of the surface of the radio wave absorber and suppresses the reflection of incident radio waves there. In addition, the radio waves that have entered the absorber are efficiently converted into thermal energy in the space containing the absorber whose conductivity and dielectric constant are equivalently increased with the penetration depth. At this time, the radio wave absorber has a structure defined by a cone-shaped recess formed on the surface (for example, a lattice structure when the concave surface is a regular quadrangular pyramid, a Haniem structure when the concave surface is a regular hexagonal pyramid), The conventional problem that the body hangs down by its own weight and the shape of the cone-shaped recess is deformed and the desired absorption performance cannot be obtained does not occur.

Further, since the increase in the cross-sectional area of the absorber with respect to the radio wave entering the radio wave absorber portion is larger than that of the radio wave absorber 02 of the conventional example, the radio wave absorbing performance is improved.

[0011]

Embodiments (1) A first embodiment of the present invention will be described with reference to FIG. An electromagnetic wave absorber 1 having a quadrangular pyramid-shaped recess 2 is formed on the surface b with its axis perpendicular to each other and adjacent to each base. The radio wave absorber 1 is made of foamed material such as polyurethane impregnated with carbon black, styrofoam, and plastic, that is, foamed plastic.

In the above, the radio wave enters the surface b almost vertically. The area of the surface of the absorber 1 is the area of the lattice-shaped portion indicated by 3, and it can be made a sufficiently small value by providing the adjacent quadrangular pyramidal recesses 2 so as to be in contact with each other. The radio wave that has entered the absorber 1 having a sufficiently small surface area enters the absorber while being repeatedly reflected multiple times by the slope of the quadrangular pyramid-shaped recess 2 and is converted (absorbed) into thermal energy. Here, the quadrangular pyramid-shaped recess 2
The shape of can be determined in consideration of the wavelength of the radio wave to be absorbed, the difficulty of manufacturing and mounting the radio wave absorber, and the like.

When the back surface c of the electromagnetic wave absorber 1 is installed as a side wall on the wall surface of the anechoic chamber, the surface of the absorber 1 has a lattice shape and is deformed by its own weight to deteriorate the performance of the absorber. Does not occur.

Further, integral molding can be easily carried out and the cost can be reduced.

In this embodiment (FIG. 1), the opening width L ₁ = 8 inches, the depth L ₂ = 20 inches, and the bottom portion thickness L ₃ = 4 inches, and the first conventional example (FIG. 5). Then, the width L ₁ ′ = L ₁ , the height L ₂ ′ = L ₂ , and the bottom thickness L ₃ ′ = L of the absorbent body 01.
The actual measurement result of the radio performance when the value is ₃ is -48d for the former.
B, and the latter was -32 dB. From this result, it can be seen that this example is extremely excellent. (2) A second embodiment of the present invention is shown in FIG. The above-mentioned quadrangular pyramid-shaped recess is made into a triangular-pyramidal recess 4. (3) A third embodiment of the present invention is shown in FIG. The quadrangular pyramidal recess of the first embodiment is replaced by a regular hexagonal pyramid recess 5. (4) FIG. 4 shows a fourth embodiment of the present invention. The quadrangular pyramidal recess of the first embodiment is replaced with a conical recess 6.

The shape of the conical recess may be other than the above. Also, a combination of these may be used.

[0017]

As described above, according to the present invention, since a plurality of cone-shaped recesses are provided, the electromagnetic wave absorption performance is high. Further, when it is installed on the wall surface, it does not hang down due to its own weight and its shape is not deformed, so that it can be used without impairing the original performance of the absorber. Further, integral molding can be easily performed.

[Brief description of drawings]

FIG. 1 is a perspective view of a radio wave absorber according to a first embodiment of the present invention.

FIG. 2 is a surface shape diagram of a radio wave absorber according to a second embodiment of the present invention.

FIG. 3 is a surface shape diagram of a radio wave absorber according to a third embodiment of the present invention.

FIG. 4 is a surface shape diagram of a radio wave absorber according to a fourth embodiment of the present invention.

FIG. 5 is a perspective view of a radio wave absorber of a first example of a conventional example.

FIG. 6 is a diagram for explaining the operation of the conventional example.

FIG. 7 is an exploded perspective view of a radio wave absorber of a second example of the related art.

FIG. 8 is a perspective view of a radio wave absorber of the conventional example.

[Explanation of symbols]

 1 Radio wave absorber 2 Square pyramid-shaped recess

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Hirata 4-22 Kannon Shinmachi, Nishi-ku, Hiroshima City Mitsubishi Heavy Industries Ltd. Hiroshima Works

Claims (1)

[Claims] 1. A radio wave absorber made of foamed plastics impregnated with carbon black, characterized in that it has a plurality of cone-shaped recesses whose axes are arranged substantially perpendicularly to the surface thereof.