JP2001244686A - Radio wave absorber, radio wave dark box, radio wave darkroom, radio wave absorption panel, and radio wave absorbing screen - Google Patents

Abstract

PROBLEM TO BE SOLVED: To actualize a radio wave absorber which has superior radio wave absorption characteristics in the wide frequency bans from microwaves to millimeter waves, can prevent a rise in temperature, and is thick. SOLUTION: The radio wave absorber is equipped with a radio wave reflector 10 made of a metal plate, a 1st radio wave absorber 11 which is arranged having one surface adjacently to the surface of the radio wave reflector 10 on the radio-wave arrival side, and a 2nd radio wave absorber 12 which is arranged adjacently to the surface of the 1st radio wave absorber 11 on the radio wave arrival side. The 1st radio wave absorber 11 is formed of a foamed body containing a conductive material. The 2nd radio wave absorber 12 is formed of a heat-resisting base material and a conductive material and has opening parts 12a which penetrate it along the thickness. The thickness d1 of the 1st radio wave absorber 11 is less than the thickness d2 of the radio wave absorber 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave absorber for absorbing a radio wave of high power, and an anechoic box, an anechoic chamber, a radio wave absorbing panel and a radio wave absorbing screen using the radio wave absorber.

[0002]

2. Description of the Related Art In recent years, microwaves (radio waves having a frequency of about 1 GHz to 30 GHz) and millimeter waves (a frequency of 30 GHz) have been developed.
Various types of radars using radio waves of up to 300 GHz have been put to practical use. Such a radar needs to emit a large amount of power when detecting a distant object. From the viewpoint of safety, it is preferable to develop and evaluate such a high-power radar in a closed space surrounded by a high-power radio wave absorber that absorbs high-power microwaves and millimeter waves.

As a radio wave absorber for absorbing microwaves and millimeter waves, there has been a pyramid-shaped radio wave absorber in which an organic foam such as foamed polyethylene or polyurethane is mixed or impregnated with a conductive material such as carbon. . However, since organic materials have low heat resistance and are damaged by heat generated during irradiation with high-power radio waves, a radio-wave absorber using an organic foam as a base material cannot be used for high power. In the present application, a high-power radio wave refers to a radio wave whose power is 1 W / cm ² or more, for example. When a high-power radio wave is applied to a radio wave absorber using an organic foam as a base material, the temperature of the radio wave absorber rises to 120 ° C. or more, and exceeds the heat resistant temperature of the organic foam as a base material. .

For this reason, a high-power radio wave absorber using a heat-resistant base material such as ceramic or glass has been proposed.

[0005] For example, the document "Development of radio wave absorbers for high power" in the 1989 Spring National Convention of the Institute of Electronics, Information and Communication Engineers, B-98, describes a hollow pyramid-shaped radio wave absorber made of ceramic or glass fiber ( Hereinafter, this is referred to as a first conventional radio wave absorber.)

[0006] Also, the document "Study of High Power Radio Wave Absorber Applying Resistive Film Array", 1996, General Conference of the Institute of Electronics, Information and Communication Engineers, B-285, describes a pyramid-shaped radio wave absorber made of conductive foamed polyethylene. A radio wave absorber (hereinafter, referred to as a second conventional radio wave absorber) having a configuration in which a radio wave attenuator composed of a grid-like resistive film array made of a glass nonwoven fabric as a base material is disposed on the front surface is disclosed.

[0007]

However, since the radio wave absorber of the first prior art has a hollow pyramid shape, heat is trapped inside the hollow pyramid-shaped structure due to heat generation during irradiation of high-power radio waves. However, there is a safety problem that the temperature rise is large.

On the other hand, in the radio wave absorber of the second conventional example, since the radio wave attenuator on the front side is formed of a grid-like resistive film array having good heat dissipation, the temperature rise can be suppressed to a small level. However, in the radio wave absorber of the second conventional example, the radio wave attenuator on the front side is provided for the purpose of weakening the power of radio waves to the extent that the pyramid-shaped radio wave absorber on the back side can withstand. Therefore, the radio wave absorption performance of the radio wave absorber of the second conventional example greatly depends on the performance of the pyramid-shaped radio wave absorber on the back side. For this reason, in the radio wave absorber of the second conventional example, the radio wave attenuator is added to the front surface of the pyramid-shaped radio wave absorber to increase the overall thickness, but the radio wave absorption performance is not improved. There is a problem that the space becomes large. For example, according to the example described in the above-mentioned document "1996 Institute of Electronics, Information and Communication Engineers General Conference B-285" Study of high-power radio wave absorber applying resistive film array ""
A radio wave attenuator with a thickness of 30 cm is added to the front surface of a pyramid-shaped radio wave absorber with a thickness of 30 cm, and the total thickness is 60 cm, which is twice the thickness of the pyramid-shaped radio wave absorber. The absorption performance is not as good as that of the pyramid-shaped radio wave absorber.

Therefore, for example, in a radio wave absorber using only a grid-like resistive film array as disclosed in Japanese Patent Application Laid-Open No. Hei 6-132691, the use of a heat-resistant material as the base material allows the heat dissipation to be improved. Good, small temperature rise,
It is also conceivable to configure a radio wave absorber for high power with a small thickness. However, there is a limit in reducing the diameter of the opening formed by being surrounded by the resistance coating line in manufacturing the resistance coating line. Therefore, the radio waves that we are trying to absorb
In the case of a radio wave having a wavelength on the order of millimeters such as a millimeter wave, the radio wave is transmitted (passes) between the gratings. Therefore, there is a problem that a radio wave absorber using only a grid-shaped resistive film array cannot provide sufficient radio wave absorption performance for millimeter waves.

The present invention has been made in view of the above problems, and has as its object to have excellent radio wave absorption characteristics in a wide frequency band from microwaves to millimeter waves, to prevent temperature rise, and to reduce thickness. Another object of the present invention is to provide an electromagnetic wave absorber having a small size, an anechoic box, an anechoic chamber, an electromagnetic wave absorbing panel, and an electromagnetic wave absorbing screen using the electromagnetic wave absorber.

[0011]

A first radio wave absorber according to the present invention comprises a first radio wave absorber containing a conductive material and a first radio wave absorber disposed on the radio wave arrival side of the first radio wave absorber. A second radio wave absorber, wherein the second radio wave absorber includes a heat-resistant base material and a conductive material, has a plurality of openings penetrating in a thickness direction, and has a first radio wave absorber. The thickness of the absorber is smaller than the thickness of the second radio wave absorber.

A second radio wave absorber according to the present invention comprises a first radio wave absorber portion containing a conductive material, and a second radio wave absorber portion disposed on the radio wave arrival side of the first radio wave absorber portion. The second electromagnetic wave absorber section includes a heat-resistant base material and a conductive material, has a plurality of openings penetrating in the thickness direction, and is capable of receiving a second electromagnetic wave at a frequency of 1 GHz. The radio wave absorption of the single radio wave absorber alone is larger than the radio wave absorption of the first radio wave absorber alone.

In the first or second radio wave absorber of the present invention, microwave absorption is mainly performed by the second radio wave absorber, and millimeter wave absorption is mainly performed by the first radio wave absorber. It is possible. In general, the thickness of the radio wave absorber is substantially proportional to the wavelength of the radio wave to be absorbed. Therefore, the thickness of the first radio wave absorber that mainly absorbs the millimeter wave is the thickness of the first radio wave absorber that mainly absorbs the microwave. 2 can be made smaller than the thickness of the radio wave absorber. Also, in the first radio wave absorber of the present invention, the second radio wave absorber having a plurality of openings is arranged on the radio wave arrival side because the second radio wave absorber is formed using a heat-resistant base material. Can be prevented.

In the second radio wave absorber of the present invention,
The thickness of the radio wave absorber may be smaller than the thickness of the second radio wave absorber.

In the first or second radio wave absorber of the present invention, the thickness of the first radio wave absorber may be one third or less of the thickness of the second radio wave absorber.

Further, in the first or second radio wave absorber of the present invention, the first radio wave absorber may be made of a foam containing a conductive material.

In the first or second radio wave absorber according to the present invention, the first radio wave absorber may have a flat plate shape.

[0018] In the first or second radio wave absorber of the present invention, the heat-resistant base material constituting the second radio wave absorber may contain a hydrous inorganic compound. In this case, the hydrous inorganic compound may be sepiolite.

In the first or second radio wave absorber of the present invention, the diameter of the opening in the second radio wave absorber may be in the range of 5 mm to 50 mm.

Further, in the first or second radio wave absorber of the present invention, the diameter of the opening in the second radio wave absorber may be in the range of 10 mm to 25 mm.

Further, in the first or second radio wave absorber of the present invention, the second radio wave absorber portion includes a plurality of heat-resistant base materials and a conductive material, respectively, and penetrates in the thickness direction. A plurality of layer portions having openings may be stacked in the thickness direction. In this case, the diameter of the opening in the layer portion on the radio wave arrival side between adjacent layer portions may be equal to or larger than the diameter of the opening in the other layer portion. Further, between adjacent layer portions, the ratio of the conductive material in the layer portion on the radio wave arrival side may be equal to or less than the ratio of the conductive layer in the other layer portion. Further, the opening in the layer portion has a cross-sectional shape other than a circle, and the direction of the opening in at least one of the plurality of layer portions may be different from the direction of the opening in the other layer portion. Good. Further, the positions of the openings may be shifted from each other between adjacent layer portions.

In the first or second radio wave absorber according to the present invention, at least a part of the second radio wave absorber on the radio wave arrival side may have a shape that becomes thinner toward the radio wave arrival side. .

Further, in the first or second radio wave absorber of the present invention, at least a part of the second radio wave absorber on the radio wave arrival side has a portion where a conductive material is added to the base material. Alternatively, the pattern may become thinner on the radio wave arrival side.

Further, the first or second radio wave absorber of the present invention may further comprise a radio wave reflector disposed on the side of the first radio wave absorber opposite to the side from which radio waves arrive.

The anechoic box of the present invention is an anechoic box having an inner wall for absorbing radio waves, wherein the first or second radio wave absorber of the present invention is arranged on at least a part of the inner wall. is there.

The anechoic chamber of the present invention is an anechoic chamber having an inner wall for absorbing radio waves, wherein the first or second radio wave absorber of the present invention is disposed on at least a part of the inner wall. is there.

The radio wave absorption panel of the present invention is the first of the present invention.
Alternatively, it includes a second radio wave absorber.

The radio wave absorption screen of the present invention includes the first or second radio wave absorber of the present invention.

[0029]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an explanatory diagram showing an example of a configuration of a radio wave absorber according to an embodiment of the present invention,
FIG. 2 is an explanatory view showing another example of the configuration of the radio wave absorber according to one embodiment of the present invention, and FIG. 3 shows still another example of the configuration of the radio wave absorber according to one embodiment of the present invention. FIG. 4 is a perspective view showing another example of the configuration of the radio wave absorber according to the embodiment of the present invention. 1 and 2 are:
It includes a perspective view of the radio wave absorber shown in (a) and a side view of the radio wave absorber shown in (b).

As shown in FIGS. 1 to 4, the radio wave absorber according to the present embodiment is a radio wave reflector 1 made of a metal plate.
0, a first radio wave absorber 11 and a first radio wave absorber 1 which are formed in, for example, a flat plate shape, and are arranged such that one surface is adjacent to the surface of the radio wave reflector 10 on the radio wave arrival side.
1 has a second radio wave absorber 12 arranged adjacent to the other surface, that is, the surface on the radio wave arrival side. The thickness d ₁ of the _first radio wave absorber 11 is smaller than the thickness d ₂ of the second radio wave absorber 12. First
The thickness d ₁ of the radio wave absorber 11 is, for example, one third or less of the thickness d ₂ of the second radio wave absorber.

The first radio wave absorber 11 is made of a foam containing a conductive material. Specifically, the first
The radio wave absorber 11 is made of an organic foam such as foamed polyethylene, foamed polystyrene, foamed polyurethane, etc.
Those containing a conductive material such as carbon black or carbon graphite can be used. The amount of the conductive material is preferably adjusted so that the volume specific resistance of the first radio wave absorber 11 is about 10 ² to 10 ³ Ωcm. Further, an inorganic foam may be used instead of the organic foam.

The shape of the first radio wave absorber 11 is as follows.
Various shapes such as a flat plate shape, a pyramid shape, a wedge shape and the like are possible, but a flat plate shape is preferable from the viewpoint of easy production and installation.

The second radio wave absorber 12 includes a heat-resistant base material and a conductive material, and has a plurality of openings 12a penetrating in the thickness direction. The shape of the second radio wave absorber 12 may be a honeycomb shape as shown in FIG.
3, a corrugated shape (waveform) as shown in FIG. 3, or a shape similar to the corrugated shape as shown in FIG. 4. The second
If the shape of the radio wave absorber 12 is a shape having a plurality of openings 12a penetrating in the thickness direction, FIGS.
Other shapes may be used.

[0034] In the present application, "heat resistance" means that the heat resistance temperature is 150 ° C or higher. The heat resistant temperature of the heat resistant base material is more preferably 200 ° C. or more,
It is more preferable that the temperature is at least 00 ° C. In addition, a heat-resistant base material is determined to be a non-combustible material if the temperature inside the furnace rises to 50 ° C. or less when placed in a furnace at 750 ° C. for 20 minutes (Ministry of Construction Notification No. 1828). Is more preferable for safety.

Examples of the heat-resistant base material constituting the second electromagnetic wave absorber section 12 include ceramics and glass, and among them, a water-containing inorganic compound is preferable from the viewpoint of production and cost. Examples of the water-containing inorganic compound include, specifically, sepiolite, aluminum hydroxide, magnesium hydroxide, each hydrate of calcium hydroxide, gypsum dihydrate, calcium aluminate hydrate, wollastonite and the like. However, it is particularly preferable to use sepiolite.

Next, a method for manufacturing the second radio wave absorber 12 having a honeycomb shape will be described. Honeycomb shaped second
As a method of manufacturing the radio wave absorber 12, a method of integrally molding using a material to be the second radio wave absorber 12 or a method of manufacturing a sheet made of the material to be the second radio wave absorber 12 are described. There are various methods, such as a method of manufacturing the second radio wave absorber 12 by bonding the sheets together.

Here, with reference to FIGS. 5 and 6, an example of a method of manufacturing the second radio wave absorber 12 having a honeycomb shape will be described. FIG. 5 is a perspective view showing the honeycomb-shaped second radio wave absorber 12, and FIG. 6 is an enlarged perspective view showing a portion A in FIG. In this method, a wet sheet is manufactured by papermaking using a slurry containing a water-containing inorganic compound (and may further contain a conductive material), and the wet sheet is dried and solidified to obtain a sheet containing a water-containing inorganic compound as a main component. 21 are manufactured, and the sheet 21 is laminated in a honeycomb shape. In order to stack the sheets 21 in a honeycomb shape, for example, as shown in FIG. 6, a plurality of sheets 21 are stacked while adjoining the adjacent sheets 21 partially using an adhesive 22. The laminate may be stretched. As the adhesive 22, for example, an inorganic adhesive is used. As the inorganic adhesive, any adhesive such as a water glass type, a phosphate type, a colloidal silica type, and a colloidal alumina type can be used. Although an organic adhesive such as vinyl acetate can be used instead of the inorganic adhesive, the inorganic adhesive is superior in heat resistance.

The second radio wave absorber 12 having the shape shown in FIG. 3 or FIG. 4 can also be manufactured by laminating the sheet 21 described above.

As a method of manufacturing the grid-like second radio wave absorber 12 as shown in FIG. 2, for example, as shown in FIG. 7, a sheet having a plurality of cuts containing a hydrous inorganic compound as a main component, as shown in FIG. There is a method of manufacturing the radio wave absorber 12 by manufacturing a large number of sheets 25 and assembling the sheets 25 in a lattice shape.

As a method for imparting conductivity to the structure such as the honeycomb shape or the lattice shape that constitutes the second electromagnetic wave absorber portion 12, a honeycomb shape or a grid shape is formed from a heat-resistant base material and a material containing a conductive material. And a method of forming a conductive layer made of a conductive material on the surface of a honeycomb-shaped or lattice-shaped structure made of a heat-resistant base material. Second
Examples of the conductive material used for the radio wave absorber 12 include:
There are carbon black, carbon graphite, carbon fiber and the like.

In the radio wave absorber according to this embodiment, the microwave is mainly absorbed by the second radio wave absorber 12 and the millimeter wave is mainly absorbed by the first radio wave absorber 11. For a radio wave of a frequency of 1 GHz included in the microwave, the radio wave absorption of the second radio wave absorber 12 alone becomes larger than the radio wave absorption of the first radio wave absorber 11 alone. I have.

Here, as the diameter of the opening 12a of the second radio wave absorber 12 increases, the wavelength of the radio wave passing through the opening 12a expands to a longer wavelength. In addition, the transmission amount of the radio wave in the second radio wave absorber 12 increases, and the radio wave transmitted through the second radio wave absorber 12 cannot be absorbed by the first radio wave absorber 11. Conversely, as the diameter of the opening 12a of the second radio wave absorber 12 decreases, the second radio wave absorber 1
2 becomes difficult to manufacture, the manufacturing cost increases, and the mass increases. Considering these facts, the diameter of the opening 12a in the second electromagnetic wave absorber 12 is preferably in the range of 5 mm to 50 mm, and particularly in the range of 10 mm to 25 mm.
mm.

As will be described later with reference to embodiments, the second radio wave absorber 12 includes a plurality of openings each including a heat-resistant base material and a conductive material and penetrating in the thickness direction. A plurality of layer portions having 12a may be stacked in the thickness direction. As a method of laminating a plurality of layers, there is a method of bonding with an organic adhesive such as an inorganic adhesive or an epoxy resin. Comparing the inorganic adhesive and the organic adhesive, the inorganic adhesive is superior in heat resistance.

When the second radio wave absorber 12 is formed by laminating a plurality of layer portions in the thickness direction, the opening of the layer portion on the radio wave arrival side is formed between adjacent layer portions. The diameter may be equal to or larger than the diameter of the opening in the other layer portion. Further, between adjacent layer portions, the ratio of the conductive material in the layer portion on the radio wave arrival side may be equal to or less than the ratio of the conductive layer in the other layer portion. Further, the opening in the layer portion has a cross-sectional shape other than a circle, and the direction of the opening in at least one of the plurality of layer portions may be different from the direction of the opening in the other layer portion. Good. Further, the positions of the openings may be shifted from each other between adjacent layer portions.

Further, at least a part of the second radio wave absorber 12 on the radio wave arrival side may have a shape that becomes thinner toward the radio wave arrival side. Further, at least a part of the second radio wave absorber 12 on the radio wave arrival side may have a pattern in which the portion of the base material to which the conductive material is added becomes thinner toward the radio wave arrival side.

Hereinafter, the configurations of nine examples and three comparative examples in this embodiment and their characteristics will be described.

FIG. 8 is an explanatory view showing the structure of the radio wave absorber of Comparative Example 1. 8A is a perspective view of the radio wave absorber, and FIG. 8B is a side view of the radio wave absorber. The radio wave absorber of Comparative Example 1 is a radio wave reflector 11 using an aluminum plate.
The configuration is such that a lattice-shaped conductive radio wave absorber 112 is joined to the zero radio wave arrival side. The thickness of the conductive electromagnetic wave absorber 112 is 25 mm. Hereinafter, the opening in the conductive electromagnetic wave absorber 112 is referred to as a cell. In Comparative Example 1, the cross-sectional shape of the cell is a square. Hereinafter, the shortest diameter in the cross section of the cell is referred to as the cell diameter. In Comparative Example 1, the diameter of the cell was 20 mm. The conductive radio wave absorber 112 has carbon on the surface of a lattice-like structure made of sepiolite as a base material.
It was manufactured by coating at a rate of 5 g / liter. here,
The “ratio of 0.5 g / liter” means “the ratio of 0.5 g / liter to the total volume of the conductive electromagnetic wave absorber 112 including the cell”. Hereinafter, the same applies to the case where the values are different. This comparative example 1 is used for comparison with the following example 1.

FIG. 9 is an explanatory view showing the structure of the radio wave absorber of the first embodiment. 9A is a perspective view of the radio wave absorber, and FIG. 9B is a side view of the radio wave absorber. The radio wave absorber of the first embodiment is a radio wave reflector 10 using an aluminum plate.
The first radio wave absorber 11 and the lattice-shaped second radio wave absorber 12 are sequentially stacked on the radio wave arrival side. The thickness of the first radio wave absorber 11 is 5 mm, and the thickness of the second radio wave absorber 12 is 25 mm. Hereinafter, the opening in the second radio wave absorber 12 is also referred to as a cell. In the first embodiment, the cross-sectional shape of the cell is a square. In Example 1, the diameter of the cell was 20 mm. The first radio wave absorber 11 was manufactured by mixing carbon into foamed polyethylene. The second radio wave absorber 12 was manufactured by applying carbon at a rate of 0.5 g / liter on the surface of a lattice-like structure made of sepiolite as a base material. Here, “the ratio of 0.5 g / liter” means “the ratio of 0.5 g / liter to the total volume of the second radio wave absorber 12 including the cell”. Hereinafter, the same applies to the case where the values are different.

FIG. 10 is an explanatory view showing the structure of the radio wave absorber of the second embodiment. 10A is a perspective view of the radio wave absorber, and FIG. 10B is a side view of the radio wave absorber. The radio wave absorber according to the second embodiment has a configuration in which a first radio wave absorber 11 and a second honeycomb-shaped radio wave absorber 12 are sequentially stacked on the radio wave arrival side of a radio wave reflector 10 using an aluminum plate. It has become. The thickness of the first radio wave absorber 11 is 5 m
m, the thickness of the second radio wave absorber 12 is 25 mm.
In Example 2, the cross-sectional shape of the cell is a hexagonal shape,
The diameter of the cell is 20 mm. In the second embodiment, the cells are arranged such that the direction of the shortest diameter in the cross section of the cell is oriented in the vertical direction. First radio wave absorber 11
Was manufactured by mixing carbon into foamed polyethylene.
The second electromagnetic wave absorber 12 was manufactured by applying carbon at a rate of 0.5 g / liter on the surface of a honeycomb-shaped structure made of sepiolite as a base material.

FIG. 11 is an explanatory view showing the configuration of the radio wave absorber of Comparative Example 2. 11A is a perspective view of the radio wave absorber, and FIG. 11B is a side view of the radio wave absorber. The radio wave absorber of Comparative Example 2 has a configuration in which a honeycomb-shaped conductive radio wave absorber 112 is joined to a radio wave arrival side of a radio wave reflector 110 using an aluminum plate. The conductive radio wave absorber 112 includes two honeycomb-shaped radio wave absorbers 112.
A and 112B are joined together. The radio wave absorber 112A is arranged on the radio wave reflector 110 side, and the radio wave absorber 112B is arranged on the radio wave arrival side. The thickness of each of the radio wave absorbers 112A and 112B is 25 mm, and the thickness of the conductive radio wave absorber 112 is 50 mm.
In the radio wave absorbers 112A and 112B, the cross section of the cell is hexagonal, and the diameter of the cell is 20 mm. In the radio wave absorbers 112A and 112B, the cells are arranged such that the direction of the shortest diameter in the cross section of the cell is oriented in the vertical direction. In Comparative Example 2, the radio wave absorbers 112A and 112B are arranged such that the directions and positions of the cells match. Radio wave absorbers 112A, 11
2B was produced by applying carbon at a rate of 0.5 g / liter on the surface of a honeycomb-shaped structure using sepiolite as a base material. Comparative Example 2 is used for comparison with the following Example 3.

FIG. 12 is an explanatory view showing the structure of the radio wave absorber of the third embodiment. 12A is a perspective view of the radio wave absorber, and FIG. 12B is a side view of the radio wave absorber. The radio wave absorber according to the third embodiment has a configuration in which a first radio wave absorber 11 and a honeycomb-shaped second radio wave absorber 12 are sequentially stacked on the radio wave arrival side of a radio wave reflector 10 using an aluminum plate. It has become. The second radio wave absorber 12 has a configuration in which two honeycomb-shaped radio wave absorbers 12A and 12B are joined, and the radio wave absorber 12A is arranged on the radio wave reflector 10 side, and the second radio wave absorber 12 12B is arranged on the radio wave arrival side. The radio wave absorber portions 12A and 12B correspond to the layer portions in the present invention. The thickness of the first radio wave absorber 11 is 5 mm. The thickness of each of the radio wave absorbers 12A and 12B is 25 mm, and the thickness of the second radio wave absorber 12 is 50 mm. In the radio wave absorbers 12A and 12B, the cross-sectional shape of the cell is hexagonal, and the diameter of the cell is 2 mm.
0 mm. In the radio wave absorbers 12A and 12B, the cells are arranged so that the direction of the shortest diameter in the cross section of the cell is oriented in the vertical direction. In the third embodiment, the radio wave absorbers 12A and 12B are arranged so that the directions and positions of the cells match. The first radio wave absorber 11 was manufactured by mixing carbon into foamed polyethylene. Radio wave absorber 12 of second radio wave absorber 12
A and 12B were produced by applying carbon at a rate of 0.5 g / liter on the surface of a honeycomb-shaped structure using sepiolite as a base material.

FIG. 13 is a side view showing the structure of the radio wave absorber of the fourth embodiment. The radio wave absorber according to the fourth embodiment has a configuration in which a first radio wave absorber 11 and a honeycomb-shaped second radio wave absorber 12 are sequentially laminated on the radio wave arrival side of a radio wave reflector 10 using an aluminum plate. It has become. The second radio wave absorber 12 is composed of two honeycomb-shaped radio wave absorbers 12.
A and 12B are joined together, and the radio wave absorber 12A is disposed on the radio wave reflector 10 side, and the radio wave absorber 1
2B is arranged on the radio wave arrival side. The thickness of the first radio wave absorber 11 is 5 mm. Radio wave absorber 12A, 1
The thickness of each of 2B is 25 mm, and the thickness of the second electromagnetic wave absorber 12 is 50 mm. Radio wave absorber 12
In A and 12B, the cross-sectional shape of the cell is a hexagonal shape, and the diameter of the cell is 20 mm. Hereinafter, in the drawings, a cell having a diameter of 20 mm is referred to as a 20 mm cell. Further, in the fourth embodiment, the cell is arranged such that the direction of the shortest diameter in the cross section of the cell in the radio wave absorber 12A is oriented in the horizontal direction, and the direction of the shortest diameter in the cross section of the cell in the radio wave absorber 12B. The cells are arranged so as to face in the vertical direction. As described above, in the fourth embodiment, the directions of the cells of the two radio wave absorbers 12A and 12B are different from each other. The first radio wave absorber 11 was manufactured by mixing carbon into foamed polyethylene. The radio wave absorbers 12A and 12B of the second radio wave absorber 12 were manufactured by applying carbon at a rate of 0.5 g / liter on the surface of a honeycomb structure using sepiolite as a base material.

FIG. 14 is a side view showing the structure of the radio wave absorber of Comparative Example 3. The radio wave absorber of Comparative Example 3 has a configuration in which a honeycomb-shaped conductive radio wave absorber 112 is joined to the radio wave arrival side of a radio wave reflector 110 using an aluminum plate. The conductive electromagnetic wave absorber 112 has a honeycomb shape of 6.
The two radio wave absorbers 112A to 112F
They are arranged in order from the 10 side and joined to each other. Each of the radio wave absorbers 112A to 112F has a thickness of 25 mm, and the conductive radio wave absorber 112 has a thickness of 15 mm.
0 mm. In the radio wave absorbers 112A to 112F, the cross section of the cell is hexagonal, and the diameter of the cell is 20.
mm. In Comparative Example 3, the radio wave absorber 112
In A, 112C and 112E, the cells are arranged so that the direction of the shortest diameter in the cross section of the cell is horizontal, and in the radio wave absorbers 112B, 112D and 112F, the direction of the shortest diameter in the cross section of the cell is the vertical direction. The cells are arranged to face. As described above, in Comparative Example 3, the cell directions of the radio wave absorbers 112A to 112F are alternately different. The radio wave absorbers 112A to 112F were manufactured by applying carbon at a rate of 0.5 g / liter on the surface of a honeycomb-shaped structure made of sepiolite as a base material.
This comparative example 3 is used for comparison with the following example 5.

FIG. 15 is a side view showing the structure of the radio wave absorber of the fifth embodiment. The radio wave absorber of the fifth embodiment has a configuration in which a first radio wave absorber 11 and a second honeycomb-shaped radio wave absorber 12 are sequentially stacked on the radio wave arrival side of a radio wave reflector 10 using an aluminum plate. It has become. The thickness of the first radio wave absorber 11 is 50 mm. The second radio wave absorber 12 includes six honeycomb-shaped radio wave absorbers 12A to 12A.
2F are arranged in order from the radio wave reflector 10 side and joined to each other. Each of the radio wave absorbers 12A to 12F has a thickness of 25 mm, and the second radio wave absorber 12
Has a thickness of 150 mm. Radio wave absorbers 12A-12
In F, the cross-sectional shape of the cell is a hexagonal shape, and the diameter of the cell is 20 mm. In the fifth embodiment, in the radio wave absorbers 12A, 12C, and 12E, the cells are arranged so that the direction of the shortest diameter in the cross section of the cell is in the horizontal direction, and in the radio wave absorbers 12B, 12D, and 12F, The cells are arranged such that the direction of the shortest diameter is vertical. Thus, in the fifth embodiment, the directions of the cells of the radio wave absorbers 12A to 12F are alternately different.
The first radio wave absorber 11 was manufactured by mixing carbon into foamed polyethylene. The radio wave absorbers 12A to 12F of the second radio wave absorber 12 were manufactured by applying carbon at a rate of 0.5 g / liter on the surface of a honeycomb-shaped structure using sepiolite as a base material.

FIG. 16 is a side view showing the structure of the radio wave absorber of the sixth embodiment. The radio wave absorber according to the sixth embodiment has a structure in which a first radio wave absorber 11 and a second honeycomb-shaped radio wave absorber 12 are sequentially stacked on the radio wave arrival side of a radio wave reflector 10 using an aluminum plate. It has become. The thickness of the first radio wave absorber 11 is 50 mm. The second radio wave absorber 12 includes six honeycomb-shaped radio wave absorbers 12A to 12A.
2F are arranged in order from the radio wave reflector 10 side and joined to each other. Each of the radio wave absorbers 12A to 12F has a thickness of 25 mm, and the second radio wave absorber 12
Has a thickness of 150 mm. Radio wave absorbers 12A-12
In F, the cross-sectional shape of the cell is a hexagonal shape, and the diameter of the cell is 20 mm. In the sixth embodiment, in the radio wave absorbers 12A, 12C, and 12E, the cells are arranged so that the direction of the shortest diameter in the cross section of the cell is in the horizontal direction, and in the radio wave absorbers 12B, 12D, and 12F, The cells are arranged such that the direction of the shortest diameter is vertical. In the sixth embodiment, the radio wave absorber 12
A and 12B are manufactured by applying carbon at a rate of 1 g / liter on the surface of a honeycomb-shaped structure based on sepiolite, and the radio wave absorbers 12C and 12D are honeycomb-shaped structures based on sepiolite. It is manufactured by applying carbon at a rate of 0.5 g / l on the surface of the body, and the radio wave absorbers 12E and 12F are coated with 0.3 g / l of carbon on the surface of a honeycomb-shaped structure based on sepiolite. Produced by applying in proportions. Thus, the ratio of the radio wave absorbers 12C and 12D containing the conductive material is smaller than the ratio of the radio wave absorbers 12A and 12B containing the conductive material, and the ratio of the radio wave absorbers 12E and 12F containing the conductive material. Is smaller than the ratio of the radio wave absorbers 12C and 12D containing the conductive material. The first radio wave absorber 11 was manufactured by mixing carbon into foamed polyethylene.

FIG. 17 is a side view showing the structure of the radio wave absorber of the seventh embodiment. The radio wave absorber according to the seventh embodiment has a configuration in which a first radio wave absorber 11 and a second honeycomb-shaped radio wave absorber 12 are sequentially stacked on the radio wave arrival side of a radio wave reflector 10 using an aluminum plate. It has become. The thickness of the first radio wave absorber 11 is 50 mm. The second radio wave absorber 12 includes six honeycomb-shaped radio wave absorbers 12A to 12A.
2F are arranged in order from the radio wave reflector 10 side and joined to each other. Each of the radio wave absorbers 12A to 12F has a thickness of 25 mm, and the second radio wave absorber 12
Has a thickness of 150 mm. Radio wave absorbers 12A-12
In F, the cross-sectional shape of the cell is a hexagonal shape. In Example 7, the radio wave absorbers 12A and 12B have a cell diameter of 10 mm, the radio wave absorbers 12C and 12D have a cell diameter of 15 mm, and the radio wave absorbers 12E and 12F.
In this case, the diameter of the cell is 20 mm. Hereinafter, in the figure, a cell having a diameter of 10 mm is referred to as a 10 mm cell, and a cell having a diameter of 15 mm
Is referred to as a 15 mm cell. In the seventh embodiment, in the radio wave absorbers 12A, 12C and 12E, the cells are arranged so that the direction of the shortest diameter in the cross section of the cell is in the horizontal direction, and in the radio wave absorbers 12B, 12D and 12F, the cells are arranged. The cells are arranged so that the direction of the shortest diameter in the cross section is vertical. First radio wave absorber 1
No. 1 was produced by mixing carbon into foamed polyethylene. In the seventh embodiment, the radio wave absorbers 12A, 12B
Is manufactured by applying carbon at a rate of 0.6 g / liter on the surface of a honeycomb-shaped structure based on sepiolite, and the radio wave absorbers 12C and 12D are formed on a honeycomb-shaped structure based on sepiolite. Carbon on the surface of.
The radio wave absorbers 12E and 12F were produced by applying carbon at a rate of 0.3 g / liter on the surface of a honeycomb-shaped structure made of sepiolite as a base material.

FIG. 18 is a side view showing the structure of the radio wave absorber of the eighth embodiment. The radio wave absorber of the eighth embodiment is similar to the radio wave absorber 12 of the radio wave absorber of the seventh embodiment shown in FIG.
The diameter of the cells A and 12B is 15 mm, and the radio wave absorbers 12A to 12D are manufactured by applying carbon at a rate of 0.45 g / liter on the surface of a honeycomb-shaped structure based on sepiolite. It was done. Example 8
Other configurations of the radio wave absorber of the third embodiment are the same as those of the radio wave absorber of the seventh embodiment.

FIG. 19 is a side view showing the structure of the radio wave absorber of the ninth embodiment. The radio wave absorber of the ninth embodiment is the same as the radio wave absorber of the eighth embodiment shown in FIG.
The shape of the end portion on the radio wave arrival side is narrower toward the radio wave arrival side. Other configurations of the radio wave absorber of the ninth embodiment are the same as those of the radio wave absorber of the eighth embodiment.

FIG. 20 shows the results of measuring the radio wave absorption characteristics of each of the radio wave absorbers of Examples 1 to 9 and Comparative Examples 1 to 3 with respect to 1 GHz microwave, 10 GHz microwave and 100 GHz millimeter wave. Is shown.
In Examples 2 and 3 and Comparative Example 2, the case where the radio wave absorber was arranged so that the direction of the shortest diameter in the cross section of the cell was directed to the direction of the electric field of radio waves (indicated as direction 1 in FIG. 20), The radio wave absorption characteristics are measured when the radio wave absorber is arranged so that the direction of the longest diameter in the cross section of the cross section is directed to the direction of the electric field of the radio wave (referred to as direction 2 in FIG. 20).

From the measurement results shown in FIG. 20, it can be seen that the radio wave absorber of each example of the present embodiment can obtain excellent radio wave absorption characteristics in a wide frequency band from microwaves to millimeter waves. . In particular, when the comparative example 1 is compared with the example 1, the comparative example 2 is compared with the example 3, and the comparative example 3 is compared with the example 5, the radio wave absorber according to the present embodiment shows It can be seen that the electromagnetic wave absorption characteristics for millimeter waves are improved as compared to a radio wave absorber in which only the conductive radio wave absorber 112 is disposed in front of the radio wave reflector 110.

FIG. 21 shows the radio wave absorption characteristics of the first radio wave absorber 11 alone (referred to as the back single body in FIG. 21) and the second radio wave absorber 12 alone (see FIG. 21). In FIG. 21, the radio wave absorbing characteristic of Example 5 in which the first radio wave absorbing portion 11 and the second radio wave absorbing portion 12 are combined (shown as a combination in FIG. 21). The results of measuring the radio wave absorption characteristics are shown. In addition,
The radio wave absorption characteristics of the radio wave absorber alone are radio wave absorption characteristics when a radio wave reflector is placed on the back of the radio wave absorber alone. From the measurement results shown in FIG. 21, the amount of radio wave absorption of the second radio wave absorber unit 12 alone (the front surface single unit) with respect to the radio wave of the frequency of 1 GHz included in the microwave is shown as the first radio wave absorber unit 11 alone. It can be seen that the amount of radio wave absorption is larger than that of the back surface alone. As described above, in the radio wave absorber according to the present embodiment, the microwave is mainly absorbed by the second radio wave absorber 12 and the millimeter wave is mainly absorbed by the first wave absorber.
This is performed by the radio wave absorber 11.

Next, the operation of the radio wave absorber according to the present embodiment when a high power radio wave is incident will be described.

When the high-power radio wave is a microwave, the radio wave has a long wavelength, so that the radio wave does not easily pass through the opening (cell) of the second radio wave absorber 12 disposed on the radio wave arrival side. It is well absorbed by the radio wave absorber 12. At this time, the second radio wave absorber 12 generates heat by absorbing the high-power radio wave. However, since the second radio wave absorber 12 has a shape having a large number of openings, it has good heat dissipation. In addition, the temperature rise of the second radio wave absorber 12 is suppressed. Moreover, since the base material of the second radio wave absorber 12 is heat resistant, it is extremely safe.

On the other hand, when the high-power radio wave is a millimeter wave, the wavelength is short, so that the amount of the radio wave transmitted through the opening (cell) of the second radio wave absorber 12 increases, and the radio wave Is not sufficiently absorbed by the radio wave absorber 12. But the second
The radio wave transmitted through the radio wave absorber 12 is absorbed by the first radio wave absorber 11 disposed on the back side. At this time, since the electric power of the radio wave incident on the first radio wave absorber 11 is somewhat weakened by the second radio wave absorber 12 on the front side, the conductive material constituting the first radio wave absorber 11 is reduced. Even if the conductive foam is an organic foam, the first radio wave absorber 11 is not damaged by heat generation.

As described above, in the radio wave absorber according to the present embodiment, the absorption of microwaves is mainly performed by the second radio wave absorber 12 disposed on the front side, and the absorption of millimeter waves is performed by
The first radio wave absorber 11 mainly arranged on the back side plays the role.

In general, the thickness of the radio wave absorber is proportional to the wavelength of the radio wave to be absorbed. Therefore, the thickness of the first radio wave absorber 11 which mainly absorbs millimeter waves whose wavelength is on the order of millimeters is mainly used. Is mainly responsible for the absorption of microwaves with wavelengths on the order of centimeters to ten centimeters.
Can be made thinner than the thickness of the radio wave absorber 12.

From the above, according to the present embodiment,
It has excellent radio wave absorption characteristics in a wide frequency band from microwaves to millimeter waves, can prevent a temperature rise even when high power radio waves are incident, and can realize a radio wave absorber having a small thickness.

Further, in the radio wave absorber according to the present embodiment, when the first radio wave absorber 11 has a flat plate shape, the manufacture of the radio wave absorber becomes easy.

In the radio wave absorber according to the present embodiment, when the heat-resistant base material forming the second radio wave absorber section 12 contains a hydrous inorganic compound such as sepiolite, Manufacturing of the absorber becomes easy.

In the radio wave absorber according to the present embodiment, the diameter of the opening of the second radio wave absorber 12 is
5 mm to 50 mm, especially 10 mm to 25 m
When it is within the range of m, it is possible to suppress an increase in the manufacturing cost and mass of the radio wave absorber while maintaining the radio wave absorption performance of the second radio wave absorber 12 for microwaves.

FIGS. 12, 13, 15 to 1
As shown in FIG. 9, in the radio wave absorber according to the present embodiment, a plurality of second radio wave absorber sections 12 each including a heat-resistant base material and a conductive material and penetrating in the thickness direction are provided. When a plurality of layer portions having openings are laminated in the thickness direction, the second radio wave absorber 1 having a large thickness is formed.
2 can be easily manufactured.

In this case, as shown in FIGS. 17 to 19, the diameter of the opening in the layer portion on the radio wave arrival side between adjacent layer portions is made larger than the diameter of the opening portion in the other layer portion. In addition, it is possible to suppress the reflection of the radio wave on the radio wave arrival side surface of the radio wave absorber.

Further, as shown in FIG. 16, the ratio of the layer containing the conductive material on the radio wave arrival side to the ratio containing the conductive material in the other layer is not more than the ratio between the adjacent layers. Thereby, it is possible to suppress the reflection of the radio wave on the surface of the radio wave absorber on the radio wave arrival side.

As shown in FIGS. 13, 15 to 19, the opening in the layer portion has a cross-sectional shape other than a circle, and the opening in at least one layer portion of the plurality of layer portions. By making the direction different from the direction of the openings in the other layers, it is possible to prevent the radio wave absorption characteristics of the radio wave absorber from changing due to the direction of the radio wave absorber, especially when the radio wave is linearly polarized. Becomes possible.

Further, as shown in FIG. 22, when the positions of the openings are shifted from each other between the adjacent layer portions (radio wave absorber portions 12A and 12B), the apparent in the second radio wave absorber portion 12 is changed. The diameter of the upper opening is smaller than the diameter of the opening in each layer (the radio wave absorbers 12A and 12B). Accordingly, it is possible to make the diameter of the opening in each layer portion (radio wave absorbers 12A and 12B) relatively large while maintaining the radio wave absorption performance of the second radio wave absorber 12 with respect to microwaves. It becomes easy to manufacture the absorber, and it is possible to suppress an increase in manufacturing cost and mass of the radio wave absorber. Note that shifting the positions of the openings between adjacent layer portions can be applied to any of the third to ninth embodiments.

As shown in FIG. 19, in the radio wave absorber according to the present embodiment, the second radio wave absorber 12
In the case where at least a part of the radio wave arrival side is formed to be thinner toward the radio wave arrival side, it is possible to suppress the reflection of radio waves on the surface of the radio wave absorber on the radio wave arrival side.

Further, as shown in FIG. 23, at least a part of the second radio wave absorber 12 (including one formed by laminating a plurality of layers) on the radio wave arrival side has a base material. The portion 32 where the conductive material is added (generally applied) to the portion 31 may have a pattern that becomes thinner toward the radio wave arrival side. This makes it possible to suppress the reflection of radio waves on the radio wave arrival side surface of the radio wave absorber.

When the radio wave absorber according to the present embodiment is mounted on a wall, the integrated radio wave absorber may be mounted on the wall, but first, as shown in FIG. After attaching the first radio wave absorber 11 (and the radio wave reflector 10 when the wall surface 14 is not metal), the second radio wave absorber 12 is attached to the front surface of the first radio wave absorber 11. May be attached. At this time, in order to facilitate handling when the second radio wave absorber 12 is attached, the second radio wave absorber 12 is attached to a thin plate-like support 15 in advance, and this support 15 is Through the second
The radio wave absorber 12 may be attached to the first radio wave absorber 11. In this case, as the material of the support member 15, a material having high radio wave transparency, such as a honeycomb board or a foam, is selected.

Next, an anechoic box and an anechoic chamber according to the present embodiment will be described with reference to FIG. FIG.
FIG. 2 is an explanatory diagram showing a schematic configuration of an anechoic box and an anechoic chamber according to the present embodiment. In FIG. 25, reference numeral 50 indicates an anechoic box or an anechoic chamber. The anechoic box is used for measuring antenna characteristics of a mobile wireless terminal or the like, or measuring the influence of an electromagnetic wave irradiation on an electronic device or the like. The anechoic chamber is used to measure the radiated noise intensity of a device that generates noise that causes electromagnetic interference to other devices, or to test a malfunction by irradiating an electronic device with a strong electromagnetic field. The anechoic chamber is distinguished from an anechoic chamber in which a person may work in that the person does not work therein. Both the anechoic box and the anechoic chamber have inner walls for absorbing radio waves. The anechoic box and the anechoic chamber according to the present embodiment use the radio wave absorber 51 according to the present embodiment on at least a part of an inner wall for absorbing radio waves.

Next, a radio wave absorbing panel and a radio wave absorbing partition according to the present embodiment will be described with reference to FIG. FIG. 26 is an explanatory diagram showing a schematic configuration of a radio wave absorbing panel and a radio wave absorbing partition according to the present embodiment. FIG.
In the figure, reference numeral 60 indicates a radio wave absorbing panel or a radio wave absorbing partition. The radio wave absorption panel and the radio wave absorption screen are both plate-like structures for absorbing radio waves. The radio wave absorption panel is used by being attached to another structure, and the radio wave absorption screen is used alone. The radio wave absorbing panel and the radio wave absorbing partition according to the present embodiment include the radio wave absorber 61 according to the present embodiment.

The anechoic box, anechoic chamber,
According to the radio wave absorption panel or the radio wave absorption partition, excellent radio wave absorption characteristics can be obtained in a wide frequency band from microwaves to millimeter waves, and a temperature rise can be prevented even when a high-power radio wave is incident. In addition, the anechoic box according to the present embodiment,
According to the anechoic chamber, the radio wave absorbing panel or the radio wave absorbing screen, the thickness of the radio wave absorber can be reduced, so that the space occupied by the radio wave absorber can be reduced, and the space used for measurement and the like can be increased accordingly. Will be possible.

The present invention is not limited to the above embodiment, but can be variously modified. For example, the radio wave absorber of the present invention can be used not only for high-power radio waves, but also for general applications of absorbing radio waves.

[0083]

As described above, claims 1 to 3 are described.
According to the radio wave absorber described in any one of the above items 3, it is possible to mainly absorb microwaves by the second radio wave absorber and to absorb millimeter waves mainly by the first radio wave absorber. Therefore, there is an effect that excellent radio wave absorption characteristics can be obtained in a wide frequency band from microwaves to millimeter waves. Further, according to the present invention, since the second radio wave absorber having a plurality of openings is configured on the radio wave arrival side, the temperature can be prevented from rising. This has the effect. According to the present invention, the thickness of the first radio wave absorber that mainly absorbs millimeter waves is made smaller than the thickness of the second radio wave absorber that mainly absorbs microwaves. Therefore, there is an effect that the thickness can be reduced.

Further, according to the radio wave absorber of the fourth or twenty-first aspect, the first radio wave absorber is formed in a flat plate shape, so that it is easy to manufacture the radio wave absorber.

Further, according to the radio wave absorber of the fifth, sixth, twenty-second or twenty-third aspect, the heat-resistant base material constituting the second radio wave absorber portion contains a hydrous inorganic compound.
This has the effect of facilitating the manufacture of the radio wave absorber.

According to the radio wave absorber according to the seventh, eighth, twenty-fourth, or twenty-fifth aspect, the diameter of the opening in the second radio wave absorber is within a predetermined range. While maintaining the radio wave absorption performance of the radio wave absorber,
This has the effect of suppressing an increase in the manufacturing cost and mass of the radio wave absorber.

According to the radio wave absorber of any one of claims 9 to 13 or 26 to 30, a plurality of layers are laminated to form a second radio wave absorber. Therefore, the second radio wave absorber having a large thickness can be easily manufactured.

According to the radio wave absorber of claim 10 or 27, the diameter of the opening in the layer portion on the radio wave arrival side between the adjacent layer portions is larger than the diameter of the opening portion in the other layer portion. Therefore, there is an effect that it is possible to suppress the reflection of the radio wave on the surface of the radio wave absorber on the radio wave arrival side.

According to the radio wave absorber of the present invention, the ratio of the conductive material in the layer portion on the radio wave arrival side between the adjacent layer portions and the conductive material in the other layer portion can be reduced. Since the ratio is not more than the included ratio, there is an effect that it is possible to suppress the reflection of the radio wave on the surface of the radio wave absorber on the radio wave arrival side.

According to the radio wave absorber of the twelfth or twenty-ninth aspect, the opening in the layer portion has a cross-sectional shape other than a circle, and the opening in the at least one layer portion of the plurality of layer portions. Since the direction is different from the direction of the openings in the other layer parts, it is possible to prevent the radio wave absorption characteristics of the radio wave absorber from changing depending on the direction of the radio wave absorber, especially when the radio wave is linearly polarized. It has the effect that it becomes possible.

According to the radio wave absorber of the present invention, since the positions of the openings are shifted from each other between the adjacent layer portions, the radio wave absorption performance of the second radio wave absorber for microwaves is improved. While maintaining, it is possible to make the diameter of the opening in each layer part relatively large,
It is possible to produce the radio wave absorber easily and to suppress the increase in the manufacturing cost and the mass of the radio wave absorber.

According to the radio wave absorber of the present invention, at least a part of the second radio wave absorber on the radio wave arrival side has a shape that becomes narrower toward the radio wave arrival side. There is an effect that it is possible to suppress the reflection of radio waves on the radio wave arrival side surface of the absorber.

According to the radio wave absorber of claim 15 or 32, at least a portion of the second radio wave absorber on the radio wave arrival side, the portion where the conductive material is added to the base material. In addition, since the pattern has a pattern that becomes thinner on the radio wave arrival side, it is possible to suppress the reflection of radio waves on the radio wave arrival side surface of the radio wave absorber.

Further, according to the anechoic box, anechoic chamber, anechoic panel or anechoic screen of the present invention, excellent electromagnetic wave absorption characteristics can be obtained in a wide frequency band from microwaves to millimeter waves, and a rise in temperature can be prevented. In addition to this, there is an effect that it is possible to secure a large space used for measurement and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating an example of a configuration of a radio wave absorber according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing another example of the configuration of the radio wave absorber according to one embodiment of the present invention.

FIG. 3 is a perspective view showing still another example of the configuration of the radio wave absorber according to one embodiment of the present invention.

FIG. 4 is a perspective view showing still another example of the configuration of the radio wave absorber according to one embodiment of the present invention.

FIG. 5 is a perspective view showing a honeycomb-shaped second radio wave absorber in one embodiment of the present invention.

FIG. 6 is an enlarged perspective view showing a portion A in FIG. 5;

FIG. 7 is a perspective view illustrating a method of manufacturing the second grid-shaped radio wave absorber according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram illustrating a configuration of a radio wave absorber of Comparative Example 1.

FIG. 9 is an explanatory diagram illustrating a configuration of a radio wave absorber according to the first embodiment.

FIG. 10 is an explanatory diagram illustrating a configuration of a radio wave absorber according to a second embodiment.

FIG. 11 is an explanatory diagram illustrating a configuration of a radio wave absorber of Comparative Example 2.

FIG. 12 is an explanatory diagram illustrating a configuration of a radio wave absorber according to a third embodiment.

FIG. 13 is a side view illustrating a configuration of a radio wave absorber according to a fourth embodiment.

FIG. 14 is a side view showing a configuration of a radio wave absorber of Comparative Example 3.

FIG. 15 is a side view illustrating a configuration of a radio wave absorber according to a fifth embodiment.

FIG. 16 is a side view illustrating a configuration of a radio wave absorber according to a sixth embodiment.

FIG. 17 is a side view illustrating a configuration of a radio wave absorber according to a seventh embodiment.

FIG. 18 is a side view illustrating a configuration of a radio wave absorber according to an eighth embodiment.

FIG. 19 is a side view illustrating a configuration of a radio wave absorber according to a ninth embodiment.

FIG. 20 is an explanatory diagram showing the results of measuring the radio wave absorption characteristics of each radio wave absorber of the example and the comparative example.

FIG. 21 is a characteristic diagram illustrating a radio wave absorption characteristic of the radio wave absorber of the fifth embodiment.

FIG. 22 is a perspective view illustrating an example of a configuration of a second radio wave absorber according to one embodiment of the present invention.

FIG. 23 is an explanatory diagram showing another example of the configuration of the second radio wave absorber in one embodiment of the present invention.

FIG. 24 is an explanatory diagram illustrating an example of a method of attaching a radio wave absorber according to one embodiment of the present invention.

FIG. 25 is an explanatory diagram showing a schematic configuration of an anechoic box and an anechoic chamber according to the present embodiment.

FIG. 26 is an explanatory diagram showing a schematic configuration of a radio wave absorbing panel and a radio wave absorbing partition according to the present embodiment.

[Explanation of symbols]

10 radio wave reflector, 11 first radio wave absorber, 12
2nd radio wave absorber part, 12a ... opening part.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Koji Takizawa Inventor F-term (reference) in TDK Corporation 1-1-13 Nihonbashi, Chuo-ku, Tokyo 2E001 DE01 DH01 FA26 GA01 GA12 GA87 HA11 HA14 HB01 HB04 HD03 HD08 HD09 JA06 LA04 5E321 AA42 BB01 BB32 CC16 GG11

Claims (37)

[Claims] A first radio wave absorber including a conductive material; a second radio wave absorber disposed on a radio wave arrival side of the first radio wave absorber; The radio wave absorber includes a heat-resistant base material and a conductive material, and has a plurality of openings penetrating in a thickness direction. The thickness of the first radio wave absorber is equal to the thickness of the second radio wave. A radio wave absorber characterized by being smaller than the thickness of the absorber part. 2. The radio wave absorber according to claim 1, wherein the thickness of the first radio wave absorber is one third or less of the thickness of the second radio wave absorber. 3. The radio wave absorber according to claim 1, wherein the first radio wave absorber is formed of a foam containing a conductive material. 4. The radio wave absorber according to claim 1, wherein said first radio wave absorber has a flat plate shape. 5. The radio wave absorber according to claim 1, wherein the heat-resistant base material constituting the second radio wave absorber section contains a hydrous inorganic compound. 6. The radio wave absorber according to claim 5, wherein said hydrous inorganic compound is sepiolite. 7. The radio wave absorber according to claim 1, wherein the diameter of the opening in the second radio wave absorber is in a range of 5 mm to 50 mm. 8. The radio wave absorber according to claim 1, wherein a diameter of the opening in the second radio wave absorber is in a range of 10 mm to 25 mm. 9. The second electromagnetic wave absorber section includes a plurality of layer portions each including a heat-resistant base material and a conductive material and having a plurality of openings penetrating in a thickness direction. 9. The radio wave absorber according to claim 1, wherein the radio wave absorber is laminated. 10. The radio wave absorber according to claim 9, wherein, between adjacent layer portions, the diameter of the opening in the layer portion on the radio wave arrival side is equal to or larger than the diameter of the opening portion in the other layer portion. . 11. The method according to claim 9, wherein, between adjacent layer portions, the ratio of the conductive material in the layer portion on the radio wave arrival side is equal to or less than the ratio of the conductive material in the other layer portion. 10. The radio wave absorber according to 10. 12. The opening in the layer portion has a cross-sectional shape other than a circle, and the direction of the opening in at least one of the plurality of layer portions is the same as the direction of the opening in the other layer portion. The radio wave absorber according to any one of claims 9 to 11, which is different from the above. 13. The radio wave absorber according to claim 9, wherein the positions of the openings are shifted from each other between adjacent layer portions. 14. The apparatus according to claim 1, wherein at least a part of the second radio wave absorber on the radio wave arrival side has a shape that becomes thinner toward the radio wave arrival side. Radio wave absorber. 15. At least a portion of the second radio wave absorber on the radio wave arrival side, the portion of the base material to which the conductive material is added has a pattern that becomes thinner toward the radio wave arrival side. The radio wave absorber according to any one of claims 1 to 9, wherein: 16. The radio wave according to claim 1, further comprising a radio wave reflector disposed on a side of said first radio wave absorber opposite to a radio wave arrival side. Absorber. 17. A first radio wave absorber including a conductive material, and a second radio wave absorber disposed on the radio wave arrival side of the first radio wave absorber, wherein the second radio wave absorber is provided. The radio wave absorber section includes a heat-resistant base material and a conductive material, has a plurality of openings penetrating in a thickness direction, and is provided with a second radio wave absorber section for radio waves having a frequency of 1 GHz. A radio wave absorber characterized in that the radio wave absorption amount of a single unit is larger than the radio wave absorption amount of the first radio wave absorber unit alone. 18. The radio wave absorber according to claim 17, wherein a thickness of the first radio wave absorber is smaller than a thickness of the second radio wave absorber. 19. The radio wave absorber according to claim 18, wherein a thickness of said first radio wave absorber is one third or less of a thickness of said second radio wave absorber. 20. The radio wave absorber according to claim 17, wherein said first radio wave absorber is made of a foam containing a conductive material. 21. The radio wave absorber according to claim 17, wherein said first radio wave absorber portion has a flat plate shape. 22. The radio wave absorber according to claim 17, wherein the heat-resistant base material constituting the second radio wave absorber section contains a hydrated inorganic compound. 23. The radio wave absorber according to claim 22, wherein said hydrous inorganic compound is sepiolite. 24. The radio wave absorber according to claim 17, wherein a diameter of the opening in the second radio wave absorber is in a range of 5 mm to 50 mm. 25. The radio wave absorber according to claim 17, wherein the diameter of the opening in the second radio wave absorber is in a range of 10 mm to 25 mm. 26. The second radio wave absorber section, wherein each of the plurality of layer portions including a heat-resistant base material and a conductive material and having a plurality of openings penetrating in a thickness direction is formed in a thickness direction. 2. The device according to claim 1, wherein the device is laminated.
The radio wave absorber according to any one of 7 to 25. 27. The radio wave absorber according to claim 26, wherein, between adjacent layer portions, the diameter of the opening in the layer portion on the radio wave arrival side is equal to or larger than the diameter of the opening portion in the other layer portion. . 28. The method according to claim 26, wherein, between adjacent layer portions, the ratio of the conductive material in the layer portion on the radio wave arrival side is equal to or less than the ratio of the conductive material in the other layer portion. 28. The radio wave absorber according to 27. 29. An opening in the layer portion has a cross-sectional shape other than a circle, and the direction of the opening in at least one of the plurality of layer portions is the same as the direction of the opening in the other layer portion. 29. The radio wave absorber according to claim 26, wherein the radio wave absorber is different from the radio wave absorber. 30. The radio wave absorber according to claim 26, wherein the positions of the openings are shifted from each other between the adjacent layer portions. 31. The apparatus according to claim 17, wherein at least a part of the second radio wave absorber on the radio wave arrival side has a shape that becomes thinner toward the radio wave arrival side. Radio wave absorber. 32. At least a part of the second radio wave absorber on the radio wave arrival side, the portion of the base material to which the conductive material is added has a pattern that becomes thinner toward the radio wave arrival side. The radio wave absorber according to any one of claims 17 to 26, wherein: 33. The radio wave according to claim 17, further comprising a radio wave reflector disposed on a side of said first radio wave absorber opposite to a radio wave arrival side. Absorber. 34. A radio wave anechoic box having an inner wall for absorbing radio waves, wherein the radio wave absorber according to claim 1 is disposed on at least a part of the inner wall. Anechoic box. 35. A radio wave anechoic chamber having an inner wall for absorbing radio waves, wherein the radio wave absorber according to claim 1 is disposed on at least a part of the inner wall. Anechoic chamber. 36. A radio wave absorption panel for absorbing radio waves, comprising the radio wave absorber according to claim 1. Description: 37. A radio wave absorption screen for absorbing radio waves, comprising the radio wave absorber according to any one of claims 1 to 33.