JP2004270143A - Radio wave absorber, radio wave absorbing panel, radio wave absorbing screen, radio wave absorbing wall, radio wave absorbing ceiling, and radio wave absorbing floor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a radio wave absorber, having incombustibility, light-weighted, and suitable for use in the interior. <P>SOLUTION: This radio wave absorber 10 includes: an incombustible radio wave reflector 11; n-layer (n is integers from 2 or more) of incombustible dielectric layers 12<SB>1</SB>to 12<SB>n</SB>disposed on the radio wave incoming side in the radio wave reflector 11; and resistance layers 13<SB>1</SB>to 13<SB>n</SB>disposed between the adjacent dielectric layers and on the radio wave incoming side in the dielectric layer 12<SB>n</SB>disposed on the most remote position. The dielectric layers 12<SB>1</SB>to 12<SB>b</SB>are mainly composed of inorganic material. The resistance layers 13<SB>1</SB>to 13<SB>n</SB>include plate-like or sheet-like resistance film base mainly composed of inorganic material and a resistance film formed on the resistance film base. The radio wave absorber 10 is incombustible on the whole. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radio wave absorber, a radio wave absorption panel, a radio wave absorption screen, and a radio wave absorption device which can be used to prevent radio interference such as radio wave interference and radio wave leakage in a wireless LAN (local area network) constructed indoors. The present invention relates to a wall, a radio wave absorbing ceiling, and a radio wave absorbing floor.
[0002]
[Prior art]
2. Description of the Related Art In recent years, wireless LANs have been attracting attention as network construction technologies in rooms such as offices and homes. However, when constructing a wireless LAN indoors, there is a problem that radio interference such as radio interference and radio leakage is likely to occur. For example, when radio waves used for communication are reflected multiple times due to a wall surface, a partition, or the like, a reduction in data transfer rate, deterioration of a communication signal such as mixing of noise, and interference with other communication devices occur. Also, for example, even if it is desired to provide a plurality of base stations in the office, if the frequency of the radio waves used by the plurality of base stations is the same, radio wave interference occurs between the plurality of base stations, The desired number of lines cannot be secured. Therefore, as one of EMC (Electromagnetic Compatibility) techniques for preventing such a radio wave interference, it is considered that a wall surface or a partition in a room has radio wave absorption performance.
[0003]
For example, Patent Literature 1 describes a non-combustible electromagnetic wave absorbing wall material for an interior. The wall material includes an inorganic radio wave absorbing plate and a radio wave reflector provided on one surface of the inorganic radio wave absorbing plate. The inorganic radio wave absorption plate is made of cement, silica raw material, fiber reinforcing material and ferrite powder having a content of 50 to 70% by weight.
[0004]
Non-Patent Document 1 discloses a λ / 4 type radio wave absorber formed by bonding a resistive film to a gypsum board. In this radio wave absorber, the resistive film is formed by applying a conductive paint to a PET (polyethylene terephthalate) film.
[0005]
[Patent Document 1]
JP-A-2002-364154
[Non-patent document 1]
Proceedings of CMC Technical Seminar “Latest Technology Trends of Electromagnetic Wave Absorbers”, CMC Publishing Co., Ltd., November 18, 2002, pp. 81-82
[0006]
[Problems to be solved by the invention]
The incombustible electric wave absorbing wall material for interior described in Patent Literature 1 is unlikely to be a lightweight wall material in view of its raw materials. Therefore, it is difficult to say that this non-flammable radio wave absorbing wall material for interior is suitable as a wall material for interior. Further, the radio wave absorption characteristics of the non-combustible radio wave absorbing wall material for interior described in Patent Literature 1 have a peak of reflection loss only at a frequency of 2.4 GHz. However, currently, in a wireless LAN, two frequency bands based on two standards of IEEE802.11b and IEEE802.11a, that is, 2.4 GHz band and 5.2 GHz band are used. Therefore, the non-combustible radio wave absorbing wall material for interior described in Patent Literature 1 has a problem that even if radio wave interference in the 2.4 GHz band can be prevented, radio wave interference in the 5.2 GHz band cannot be prevented. In addition, the 2.4 GHz band based on IEEE802.11b is 2.4 GHz to 2.497 GHz in Japan. In addition, the 5.2 GHz band based on IEEE802.11a is 5.15 GHz to 5.25 GHz in Japan.
[0007]
In the radio wave absorber described in Non-Patent Document 1, the resistive film is formed by applying a conductive paint to a PET film. Therefore, this radio wave absorber is not nonflammable and is not suitable for use in indoor walls. In addition, this radio wave absorber has a problem that the radio wave absorption characteristics change depending on the application direction of the conductive paint. Further, the radio wave absorption characteristics of this radio wave absorber have a reflection loss peak only at one frequency. For this reason, this radio wave absorber has a problem that it is impossible to prevent radio interference in both of the two frequency bands used in the wireless LAN.
[0008]
The present invention has been made in view of the above problems, and a first object of the present invention is to provide a radio wave absorber, a radio wave absorption panel, a radio wave absorption panel, a radio wave absorption screen, a non-flammable, lightweight, and suitable for indoor use. It is an object of the present invention to provide an absorbing wall, a radio wave absorbing ceiling and a radio wave absorbing floor.
[0009]
Further, a second object of the present invention, in addition to the first object, is a radio wave absorber, a radio wave absorption panel, a radio wave absorption screen, a radio wave absorption wall, a radio wave absorber which can prevent radio interference in at least two frequency bands. It is an object of the present invention to provide an absorbing ceiling and a radio wave absorbing floor.
[0010]
[Means for Solving the Problems]
The first radio wave absorber of the present invention is:
A non-flammable radio wave reflector,
A non-combustible dielectric layer mainly composed of an inorganic material and arranged on the radio wave arrival side of the radio wave reflector,
A plate-shaped or sheet-shaped resistive film base mainly made of an inorganic material, and including a resistive film formed on the resistive film base, including a resistive layer disposed on the radio wave arrival side of the dielectric layer,
The whole is non-flammable.
[0011]
The second radio wave absorber of the present invention comprises:
A non-flammable radio wave reflector,
An n-layer (n is an integer of 2 or more) non-combustible dielectric layer mainly composed of an inorganic material and disposed on the radio wave arrival side of the radio wave reflector;
Including a plate-shaped or sheet-shaped substrate for a resistance film mainly made of an inorganic material and a resistance film formed on the substrate for a resistance film, the substrate is disposed between two adjacent dielectric layers (n-1). ) Layer of resistance layer,
Mainly composed of an inorganic material, comprising a dielectric layer for radio wave absorption characteristic adjustment arranged on the radio wave arrival side in the dielectric layer farthest from the radio wave reflector,
The whole is non-flammable.
[0012]
The second radio wave absorber of the present invention may have a characteristic that the return loss is 15 dB or more at a plurality of frequencies. Further, the second radio wave absorber of the present invention may have a characteristic that the return loss is 15 dB or more at each of 2.4 GHz and 5.2 GHz.
[0013]
The third radio wave absorber of the present invention is:
A non-flammable radio wave reflector,
An n-layer (n is an integer of 2 or more) non-combustible dielectric layer mainly composed of an inorganic material and disposed on the radio wave arrival side of the radio wave reflector;
Including a plate-shaped or sheet-shaped resistive film base mainly composed of an inorganic material, and a resistive film formed on the resistive film base, between two adjacent dielectric layers and farthest from a radio wave reflector An n-layer resistive layer disposed on the radio wave arrival side of the dielectric layer,
The whole is non-flammable.
[0014]
In the third radio wave absorber of the present invention, the closer the resistance film is to the radio wave reflector, the smaller the sheet resistance may be. Further, the third radio wave absorber of the present invention may have a characteristic that the return loss is 15 dB or more at a plurality of frequencies. Further, the third radio wave absorber of the present invention may have a characteristic that the return loss is 15 dB or more at each frequency of 2.4 GHz and 5.2 GHz.
[0015]
In the first to third radio wave absorbers of the present invention, the resistive film may be formed on the surface on the radio wave arrival side of the resistive film base, or may be formed on the opposite surface. Good.
[0016]
Further, in the present application, "non-flammable" means having a non-flammable performance compatible with a non-flammable material specified in the Building Standards Law, and a non-flammable performance equivalent to the non-flammable performance of a non-flammable material specified in the Building Standards Law To have.
[0017]
The first to third radio wave absorbers of the present invention may further include an interior material arranged so as to cover a surface farthest from the radio wave reflector. In the first to third radio wave absorbers of the present invention, a surface farthest from the radio wave reflector may be coated.
[0018]
In the first to third radio wave absorbers of the present invention, the radio wave reflector is a plate-shaped radio wave reflector base mainly composed of an inorganic material, and a radio wave reflector base on a radio wave arrival side surface. And a conductive film disposed thereon. Further, the radio wave reflector may be bonded to the dielectric layer with an inorganic adhesive or an organic adhesive.
[0019]
Further, in the first to third radio wave absorbers of the present invention, the dielectric layer may be formed of a plate-shaped member having a plurality of holes penetrating in the traveling direction of radio waves, or a plate-shaped foam. Good. In this case, the dielectric layer has a first surface on the radio wave arrival side and a second surface on the opposite side, and at least the first surface of the first surface and the second surface is It may be covered by a plate-shaped or sheet-shaped member mainly made of an inorganic material.
[0020]
In the first to third radio wave absorbers of the present invention, the resistive film may be formed of a conductive material mixed with a coating agent and may be formed of a conductive paint applied on a resistive film base. Good. In this case, the coating agent may include at least one of an inorganic coating agent and an organic coating agent. Further, the conductive material may include at least one of carbon powder, carbon fiber, metal powder, and metal fiber.
[0021]
In the first to third radio wave absorbers of the present invention, the resistance layer may be bonded to the dielectric layer with an inorganic adhesive or an organic adhesive.
[0022]
Further, the radio wave absorbing panel of the present invention is a panel including any one of the first to third radio wave absorbers of the present invention, which is used as at least a part of any of a screen, a wall, a ceiling, and a floor. It is.
[0023]
The radio wave absorption screen of the present invention is a screen including any one of the first to third radio wave absorbers of the present invention, and has a radio wave absorbing function.
[0024]
Further, the radio wave absorbing wall of the present invention is a wall including any of the first to third radio wave absorbers of the present invention, and has a radio wave absorbing function.
[0025]
Further, the radio wave absorbing ceiling of the present invention is a ceiling including any one of the first to third radio wave absorbers of the present invention, and has a radio wave absorbing function.
[0026]
Further, the radio wave absorption floor of the present invention is a floor including the radio wave absorber of any of the first to third aspects of the present invention, and has a radio wave absorbing function.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. First, the configuration of the radio wave absorber according to the present embodiment will be described with reference to FIGS. 1 to 4 are cross-sectional views showing first to fourth examples of the basic configuration of the radio wave absorber according to the present embodiment. Note that, in FIGS. 1 to 4, the arrow denoted by reference numeral 1 indicates the traveling direction of the radio wave.
[0028]
The radio wave absorber 10 shown in FIG. 1 includes a non-combustible radio wave reflector 11 and a non-combustible dielectric layer 12 disposed on the radio wave arrival side of the radio wave reflector 11.₁And the dielectric layer 12₁Resistance layer 13 arranged on the radio wave arrival side in₁And Dielectric layer 12₁Is mainly composed of an inorganic material. Resistance layer 13₁As will be described in detail later, the substrate includes a plate-shaped or sheet-shaped substrate for a resistance film mainly made of an inorganic material, and a resistance film formed on the substrate for a resistance film. The radio wave absorber 10 is nonflammable as a whole.
[0029]
The radio wave absorber 10 according to the present embodiment may have the configuration shown in FIGS. 2 to 4 by further adding another layer to the configuration shown in FIG.
[0030]
The radio wave absorber 10 shown in FIG. 2 includes a non-combustible radio wave reflector 11 and two non-combustible dielectric layers 12 arranged on the radio wave arrival side of the radio wave reflector 11.₁, 12₂And the adjacent dielectric layer 12₁, 12₂Resistance layer 13 arranged between₁And The radio wave absorber 10 shown in FIG. 2 further includes a dielectric layer 12 farthest from the radio wave reflector 11.₂And a dielectric layer 14 for adjusting the radio wave absorption characteristics, which is arranged on the side of the radio wave arrival in the above. Dielectric layer 12₁, 12₂Is mainly composed of an inorganic material. Resistance layer 13₁The configuration of the resistance layer 13 in FIG.₁Is the same as The dielectric layer 14 for adjusting radio wave absorption characteristics is mainly made of an inorganic material, and has a plate shape or a sheet shape. The dielectric layer 14 for adjusting the radio wave absorption characteristics is the dielectric layer 12 farthest from the radio wave reflector 11.₂Protect. The radio wave absorber 10 shown in FIG. 2 is also nonflammable as a whole.
[0031]
A radio wave absorber 10 shown in FIG. 3 includes a non-combustible radio wave reflector 11 and an n-layer (n is an integer of 2 or more) non-combustible dielectric layer 12 disposed on the radio wave arrival side of the radio wave reflector 11.₁~ 12_nAnd a dielectric layer 12 disposed between adjacent dielectric layers and at a position farthest from the radio wave reflector 11._nResistance layer 13 arranged on the radio wave arrival side in₁~ 13_nAnd Dielectric layer 12₁~ 12_nIs mainly composed of an inorganic material. Resistance layer 13₁~ 13_nThe configuration of the resistance layer 13 in FIG.₁Is the same as The radio wave absorber 10 shown in FIG. 3 is also nonflammable as a whole.
[0032]
The radio wave absorber 10 shown in FIG. 4 includes a non-combustible radio wave reflector 11 and an m-layer (m is an integer of 3 or more) non-combustible dielectric layer 12 disposed on the radio wave arrival side of the radio wave reflector 11.₁~ 12_mAnd a resistance layer 13 disposed between adjacent dielectric layers₁~ 13_m-1And The radio wave absorber 10 shown in FIG. 4 further includes a dielectric layer 12 farthest from the radio wave reflector 11._mAnd a dielectric layer 14 for adjusting the radio wave absorption characteristics, which is arranged on the side of the radio wave arrival in the above. Dielectric layer 12₁~ 12_mIs mainly composed of an inorganic material. Resistance layer 13₁~ 13_m-1The configuration of the resistance layer 13 in FIG.₁Is the same as The configuration of the radio wave absorption characteristic adjusting dielectric layer 14 is the same as that of the radio wave absorption characteristic adjusting dielectric layer 14 in FIG. The radio wave absorption characteristic adjusting dielectric layer 14 has a function of arbitrarily adding one frequency at which the return loss peaks by adjusting the input impedance viewed from the radio wave arrival side of the radio wave absorber 10. Further, the dielectric layer 14 for adjusting the radio wave absorption characteristics is a dielectric layer 12 farthest from the radio wave reflector 11._mIt also has the function of protecting The radio wave absorber 10 shown in FIG. 4 is also nonflammable as a whole.
[0033]
The configuration of the radio wave absorber 10 shown in FIG. 2 and the configuration of the radio wave absorber 10 shown in FIG. 4 are collectively expressed as follows. That is, the radio wave absorber 10 shown in FIG. 2 or 4 is composed of a non-combustible radio wave reflector 11 and an n-layer (n is an integer of 2 or more) disposed on the radio wave arrival side of the radio wave reflector 11. Dielectric layer 12₁~ 12_nAnd a resistance layer 13 disposed between adjacent dielectric layers₁~ 13_n-1And The radio wave absorber 10 shown in FIG. 2 or 4 further includes a dielectric layer 12 farthest from the radio wave reflector 11._nAnd a dielectric layer 14 for adjusting the radio wave absorption characteristics, which is arranged on the side of the radio wave arrival in the above.
[0034]
Hereinafter, each dielectric layer in FIGS. 1 to 4 will be referred to as a dielectric layer 12 as a representative. Each of the resistance layers in FIGS. 1 to 4 is referred to as a resistance layer 13.
[0035]
In the radio wave absorber 10 according to the present embodiment, the thickness of the dielectric layer 12, the thickness of the resistive film substrate in the resistance layer 13, the thickness of the dielectric layer 14 for adjusting the radio wave absorption characteristics, and the resistance in the resistance layer 13 The sheet resistance of the film is set to a predetermined value so that the radio wave absorber 10 can exhibit desired radio wave absorption characteristics in a predetermined frequency range.
[0036]
The radio wave absorption characteristic of the radio wave absorber 10 having the configuration shown in FIG. 1 has a peak of the return loss at any one frequency. On the other hand, the radio wave absorber 10 having the configuration shown in FIG. 2 can realize radio wave absorption characteristics in which the peak of the return loss exists at any two frequencies. Further, the radio wave absorber 10 having the configuration shown in FIG. 3 can realize radio wave absorption characteristics in which the peak of the return loss exists at arbitrary n frequencies. Further, the radio wave absorber 10 having the configuration shown in FIG. 4 can realize radio wave absorption characteristics in which the peak of the return loss exists at arbitrary m frequencies.
[0037]
The radio wave absorber 10 shown in any of FIG. 2 to FIG. 4 preferably has a characteristic that the return loss is 15 dB or more at a plurality of frequencies, and in particular, at each frequency of 2.4 GHz and 5.2 GHz. It is preferable to have a characteristic that the return loss is 15 dB or more.
[0038]
In the radio wave absorber 10 having the configuration shown in FIG. 3, it is preferable that the closer the resistance film is to the radio wave reflector 11, the smaller the sheet resistance is. Even if this condition is not satisfied, there are combinations of sheet resistance values that can realize radio wave absorption characteristics in which there are peaks in the return loss at n frequencies. However, in this case, the width of the frequency band in which a desired return loss is obtained becomes narrow. Therefore, in this case, high precision is required to manufacture the radio wave absorber 10 so that a desired return loss is obtained in n frequency bands. In the case where the sheet resistance value becomes smaller as the resistance film becomes closer to the radio wave reflector 11, the radio wave absorber 10 can be easily manufactured so that a desired return loss can be obtained in n frequency bands. Will be possible.
[0039]
The radio wave absorber 10 according to the present embodiment can be used as at least a part of any of a screen, a wall, a ceiling, and a floor. Further, the radio wave absorbing panel according to the present embodiment is a panel including the radio wave absorber 10 according to the present embodiment and having a plate shape of a predetermined size. This radio wave absorbing panel is used as at least a part of any of a screen, a wall, a ceiling, and a floor.
[0040]
Further, as shown in FIG. 5, radio wave absorber 10 according to the present embodiment may further include interior material 15 disposed so as to cover a surface farthest from radio wave reflector 11. FIG. 5 shows an example in which the interior material 15 is provided so as to cover the surface farthest from the radio wave reflector 11 in the radio wave absorber 10 having the configuration shown in FIG. However, in the radio wave absorber 10 shown in FIG. 1, FIG. 2 or FIG. 4, the interior material 15 may be provided so as to cover the surface farthest from the radio wave reflector 11.
[0041]
The interior material 15 plays a role as a decorative material when the radio wave absorber 10 is used as at least a part of a room wall or a partition. A non-combustible cloth such as a glass cloth or a decorative cloth can be used as the interior material 15, but a non-combustible cloth is preferably used.
[0042]
In the radio wave absorber 10 according to the present embodiment, the surface farthest from the radio wave reflector 11 may be coated. The surface to which this coating is applied is the surface of the resistance layer 13, the dielectric layer for adjusting the radio wave absorption characteristics 14 or the interior material 15 on the radio wave arrival side. When the surface of the resistive layer 13 or the dielectric layer 14 for adjusting the electromagnetic wave absorption characteristic is coated, as a pretreatment for coating, the surface of the resistive layer 13 or the dielectric layer 14 for adjusting the electromagnetic wave absorption characteristic is subjected to a primer treatment. Is also good.
[0043]
Next, a method for forming the resistance layer 13 in the present embodiment will be described with reference to FIG. As shown in FIG. 6, the resistance layer 13 includes a plate-shaped or sheet-shaped resistance film base 21 mainly made of an inorganic material, and a resistance film 22 formed on the resistance film base 21. I have.
[0044]
The resistive film 22 is formed, for example, by applying a conductive paint 23 formed by mixing a conductive material to a coating agent on the resistive film base 21 and solidifying the same. The coating agent contains at least one of an inorganic coating agent and an organic coating agent. The conductive material includes, for example, at least one of carbon powder, carbon fiber, metal powder, and metal fiber.
[0045]
As shown in FIG. 6, as a method of applying the conductive paint 23, spray painting is preferable. By using the spray coating, the radio wave absorber 10 having a very small difference in the radio wave absorption characteristics depending on the application direction of the conductive paint 23 can be manufactured. In FIG. 6, reference numeral 24 denotes a discharge portion of the conductive paint 23 in the spray coating device. In particular, by applying the conductive paint 23 on the resistive film base 21 by spray coating using a robot coating device to form the resistive film 22, a stable sheet resistance value of the resistive film 22 can be obtained. .
[0046]
The inorganic coating agent used for the conductive paint 23 is not particularly limited, and those conventionally used as nonflammable inorganic coating agents can be used. Here, an example of an inorganic coating agent used for the conductive paint 23 will be given. The inorganic coating agent includes an alkyl silicate as a main component, water for hydrolyzing the alkyl silicate, and this hydrolysis reaction. It contains an aluminum chelate as a reaction catalyst for accelerating, a methyl acid phosphate as a reaction inhibitor for suppressing a hydrolysis reaction, and an alcohol as a solvent for dissolving the alkyl silicate and water. The alkyl silicate is methyltrimethoxysilane, phenyltrimethylsilane, or the like. As the inorganic coating agent used for the conductive paint 23, a water-based inorganic coating agent may be used in addition to the above examples.
[0047]
The organic coating agent used for the conductive paint 23 is not particularly limited, and for example, a commercially available organic paint can be used.
[0048]
Further, as a coating agent used for the conductive paint 23, a hybrid coating agent obtained by mixing an inorganic coating agent and an organic coating agent may be used.
[0049]
Further, in the case where the conductive film 23 is applied to the thin resistive film base 21 to form the resistive film 22, the occurrence of minute cracks in the resistive film 22 due to the warpage or bending of the resistive film base 21 is prevented. For this purpose, it is preferable to use a flexible coating agent.
[0050]
Here, an example of a method for manufacturing the resistive film base 21 will be described. In this example, the resistive film substrate 21 is formed using a slurry containing a hydrous inorganic compound as a main component. The slurry contains 60 to 90% by weight of sepiolite, and further contains a binder and a reinforcing material such as inorganic fiber and glass fiber. The binder includes a thermoplastic resin for reinforcing the resistive film substrate 21 and a thermosetting resin having a network-like three-dimensional structure and having cohesiveness and water resistance. As the thermoplastic resin, for example, an anionic thermoplastic resin such as polyacrylimide (molecular weight of about 800,000 to 1,000,000) can be used. As the thermosetting resin, for example, a cationic thermosetting resin such as polyamide polyamine epichlorohydrin can be used. A sheet is formed by papermaking using such a slurry, and the sheet is heated and dried at a predetermined temperature, whereby the evaporation of water and the reaction of the binder progress, the sheet is solidified, and the substrate for the resistive film is formed. 21 is obtained.
[0051]
The fact that the resistive film base 21 is mainly made of an inorganic material means that an auxiliary material such as a binder may include an organic material, but the main component is an inorganic material.
[0052]
The resistance layer 13 is bonded to the dielectric layer 12 with, for example, an inorganic adhesive or an organic adhesive.
[0053]
The material and manufacturing method of the dielectric layer 14 for adjusting the radio wave absorption characteristics are the same as those of the resistive film base 21. The dielectric layer 14 for adjusting the radio wave absorption characteristics is also bonded to the dielectric layer 12 with, for example, an inorganic adhesive or an organic adhesive.
[0054]
The inorganic adhesive is not particularly limited, and those conventionally used as nonflammable inorganic adhesives can be used. As the inorganic adhesive, for example, an aluminum phosphate solution, colloidal silica, colloidal alumina, or the like, a curing agent, a water-soluble or water-dispersed inorganic adhesive formed by mixing a catalyst, or the like can be used. .
[0055]
When the resistance layer 13 or the dielectric layer 14 for adjusting radio wave absorption characteristics is bonded to the dielectric layer 12 with an organic adhesive, it is necessary to make the adhesive layer thin so that the non-combustibility of the radio wave absorber 10 can be maintained. is there.
[0056]
Next, the dielectric layer 12 will be described in detail with reference to FIGS. In order to reduce the weight of the radio wave absorber 10 and to provide the radio wave absorber 10 with heat insulation, the dielectric layer 12 is a plate-shaped member having a plurality of holes penetrating in the traveling direction of radio waves, or a plate-shaped member. Preferably, it is formed by a foam. FIGS. 7 to 10 are perspective views showing first to fourth examples of the configuration of the radio wave absorber 10 having the dielectric layer 12 formed by the plate-like member having a plurality of holes as described above. It is.
[0057]
The radio wave absorber 10 of the first example shown in FIG. 7 includes a radio wave reflector 11 and a dielectric layer 12 disposed on the radio wave arrival side of the radio wave reflector 11.₁And the dielectric layer 12₁Resistance layer 13 arranged on the radio wave arrival side in₁And the resistance layer 13₁Dielectric layer 12 arranged on the radio wave arrival side in₂And the dielectric layer 12₂Resistance layer 13 arranged on the radio wave arrival side in₂And Dielectric layer 12₁, 12₂Each has a honeycomb shape having a plurality of holes penetrating in the traveling direction of radio waves. Resistance layer 13₁Is a resistive film substrate 21₁And the resistive film substrate 21₁Resistive film 22 formed on top₁And Base 21 for resistive film₁Is the dielectric layer 12₁At the radio wave arrival side. Resistive film 22₁Is the dielectric layer 12₂At the side opposite to the radio wave arrival side. Resistance layer 13₂Is a resistive film substrate 21₂And the resistive film substrate 21₂Resistive film 22 formed on top₂And Resistive film 22₂Is the dielectric layer 12₂At the radio wave arrival side.
[0058]
The radio wave absorber 10 of the second example shown in FIG. 8 is different from the radio wave absorber 10 shown in FIG.₂Instead, a dielectric layer 14 for adjusting radio wave absorption characteristics is provided. The dielectric layer 14 for adjusting the electromagnetic wave absorption characteristic is formed of the dielectric layer 12.₂At the radio wave arrival side.
[0059]
The radio wave absorber 10 of the third example shown in FIG. 9 is different from the radio wave absorber 10 shown in FIG.₁, 12₂Instead of a corrugated (waveform) dielectric layer 12 having a plurality of holes penetrating in the direction of propagation of radio waves.₁, 12₂Is provided.
[0060]
The radio wave absorber 10 of the fourth example shown in FIG. 10 is different from the radio wave absorber 10 shown in FIG.₁, 12₂Instead of a lattice-shaped dielectric layer 12 having a plurality of holes penetrating in the traveling direction of radio waves.₁, 12₂Is provided.
[0061]
As shown in FIGS. 7 to 10, by using a plate-like member having a plurality of holes penetrating in the traveling direction of the radio wave as the dielectric layer 12, as described above, The structural strength and the load resistance of the radio wave absorber 10 can be made sufficient while reducing the weight.
[0062]
The honeycomb-shaped, corrugated-shaped or lattice-shaped dielectric layer 12 is formed of, for example, a hydrous inorganic compound. Examples of the water-containing inorganic compound include sepiolite, hydrates of aluminum hydroxide, magnesium hydroxide, and calcium hydroxide, gypsum dihydrate, calcium aluminate, and wollastonite. Of these, sepiolite is particularly preferred. Since sepiolite is a flexible hydrous inorganic compound, it has high flexural strength. Therefore, when sepiolite is used as the hydrous inorganic compound, the honeycomb-shaped dielectric layer 12 can be formed as follows. That is, first, a plurality of sheets made of a water-containing inorganic compound are manufactured. Next, a plurality of sheets are stacked while partially adjoining adjacent sheets along a plurality of straight lines arranged at predetermined intervals. Next, a laminate of a plurality of sheets is stretched in the thickness direction. Thereby, a honeycomb-shaped dielectric layer 12 is formed.
[0063]
When the dielectric layer 12 is formed of a plate-like foam, the radio wave absorber 10 can have a sound absorbing function. As the foam used for the dielectric layer 12, for example, a magnesium hydroxide-based inorganic foam plate having the following composition can be used. This magnesium hydroxide-based inorganic foam board contains 60% by weight of magnesium hydroxide, 25% by weight of calcium carbonate, 10% by weight of aluminum hydroxide, 3% by weight of vinyl chloride resin, and 2% by weight of silicon-based resin. I do. As the foam used for the dielectric layer 12, in addition to the above examples, flame-retardant foams such as inocyanurate foam and phenol foam can be used.
[0064]
When the dielectric layer 12 is formed of a plate-shaped member or a plate-shaped foam having a plurality of holes penetrating in the traveling direction of the radio wave, the first of the dielectric layer 12 on the radio wave arrival side in the dielectric layer 12 is formed. It is preferable that at least the first surface of the surface and the second surface opposite thereto is covered with a plate-like or sheet-like member mainly made of an inorganic material. In this case, the plate-shaped or sheet-shaped member that covers the surface of the dielectric layer 12 may be the resistance layer 13, the radio-wave absorption characteristic adjusting dielectric layer 14, or the radio wave reflector 11.
[0065]
The fact that the dielectric layer 12 is mainly made of an inorganic material means that, as in the case of the resistive film base 21, an auxiliary material such as a binder may contain an organic material, but the main component is an inorganic material. It means that
[0066]
Next, the radio wave reflector 11 will be described in detail. The radio wave reflector 11 may be a metal plate such as a steel plate, but a plate-shaped radio wave reflector base mainly made of an inorganic material, and a conductive material disposed on the radio wave arrival side surface of the radio wave reflector base. A structure having a film is preferable. The material and manufacturing method of the base for the radio wave reflector are the same as those of the base for the resistive film 21. The conductive film may be formed of a metal foil bonded to the radio wave reflector base, or may be formed by applying a conductive paint on the radio wave reflector base and solidifying the same.
[0067]
When bonding the metal foil to the radio wave reflector base, for example, an inorganic adhesive or an organic adhesive is used. When an organic adhesive is used, the adhesive layer needs to be thin so that the non-combustibility of the radio wave absorber 10 can be maintained.
[0068]
The conductive paint may be an organic paint, but is preferably an inorganic paint. When an organic conductive paint is used, it is necessary to reduce the thickness of the conductive paint applied so that the non-flammability of the radio wave absorber 10 can be maintained.
[0069]
The radio wave reflector 11 is attached to the dielectric layer 12 with, for example, an inorganic adhesive or an organic adhesive. When an organic adhesive is used, the adhesive layer needs to be thin so that the non-combustibility of the radio wave absorber 10 can be maintained.
[0070]
Next, a radio wave absorption partition according to the present embodiment will be described with reference to FIGS. The radio wave absorbing screen according to the present embodiment is a screen including the radio wave absorber 10 according to the present embodiment, and has a radio wave absorbing function. The radio wave absorption screen according to the present embodiment may be one in which a main part is formed by the radio wave absorber 10 or one in which a radio wave absorption panel including the radio wave absorber 10 is attached to a core material of the screen. May be.
[0071]
FIG. 11 is a cross-sectional view illustrating an example of an installation state of the radio wave absorbing partition 40 whose main part is configured by the radio wave absorber 10. In this example, the radio wave absorption screen 40 has a lower end fixed to the floor 46 and an upper end fixed to the ceiling 47. However, the distance between the lower end of the radio wave absorbing screen 40 and the floor 46 or the distance between the upper end of the radio wave absorbing screen 40 and the ceiling 47 may be increased. Further, the radio wave absorbing screen 40 may be a movable screen such as a sliding wall.
[0072]
FIG. 12 is a cross-sectional view showing an example of a cross-sectional structure of the radio wave absorbing partition 40 shown in FIG. The radio wave absorbing screen 40 shown in FIG. 12 has a radio wave absorbing function only on one of the two surfaces. The radio wave absorbing screen 40 includes a radio wave reflector 11 and a dielectric layer 12 disposed on the radio wave arrival side of the radio wave reflector 11.₁And the dielectric layer 12₁Resistance layer 13 arranged on the radio wave arrival side in₁And the resistance layer 13₁Dielectric layer 12 arranged on the radio wave arrival side in₂And the dielectric layer 12₂Resistance layer 13 arranged on the radio wave arrival side in₂And the resistance layer 13₂And an interior material 45 covering the surface of the radio wave reflector 11 on the side opposite to the radio wave arrival side. The material of the interior material 45 is the same as that of the interior material 15. The surfaces of the interior materials 15 and 45 may be painted.
[0073]
FIG. 13 is a cross-sectional view showing another example of the cross-sectional structure of the radio wave absorbing partition 40 shown in FIG. The radio wave absorbing partition 40 shown in FIG. 13 has a radio wave absorbing function on both sides. The radio wave absorbing screen 40 includes a radio wave reflector 11 and a dielectric layer 12 similar to the radio wave absorbing screen 40 in FIG.₁, Resistance layer 13₁, Dielectric layer 12₂, Resistance layer 13₂And an interior material 15. The radio wave absorption screen 40 shown in FIG. 13 further includes a dielectric layer 12 around the radio wave reflector 11.₁, Resistance layer 13₁, Dielectric layer 12₂, Resistance layer 13₂And dielectric layer 42 provided symmetrically with interior material 15₁, Resistance layer 43₁, Dielectric layer 42₂, Resistance layer 43₂And an interior material 45. This dielectric layer 42₁, Resistance layer 43₁, Dielectric layer 42₂, Resistance layer 43₂Each of the components of the interior material 45 and the dielectric material 12₁, Resistance layer 13₁, Dielectric layer 12₂, Resistance layer 13₂And the interior material 15.
[0074]
The configuration of the radio wave absorbing partition 40 is not limited to the configuration shown in FIG. 12 or 13, and various configurations can be adopted similarly to the radio wave absorber 10.
[0075]
14 and 15 are cross-sectional views each showing an example of an installation state of a radio wave absorbing panel 50 configured by attaching a radio wave absorbing panel 60 to a core material of the screen. The radio wave absorbing partition 50 shown in FIG. 14 is configured by attaching a radio wave absorbing panel 60 to one surface of a plate-shaped core member 51. The radio wave absorbing partition 50 shown in FIG. 15 is configured by attaching a radio wave absorbing panel 60 to both sides of a plate-shaped core member 51. The radio wave absorption panel 60 is a panel including the radio wave absorber 10. The configuration of the radio wave absorption panel 60 is the same as that of the radio wave absorber 10 in which the interior material 15 is disposed on the surface. Further, the surface of the interior material 15 may be painted. When the core 51 is a metal plate, the core 51 may also be used as the radio wave reflector 11 in the radio wave absorber 10.
[0076]
In the examples shown in FIGS. 14 and 15, the lower end of the radio wave absorbing partition 50 is fixed to the floor 46 and the upper end is fixed to the ceiling 47. However, the distance between the lower end of the radio wave absorbing screen 50 and the floor 46 or the distance between the upper end of the radio wave absorbing screen 50 and the ceiling 47 may be increased. Further, the radio wave absorbing screen 50 may be a movable screen such as a sliding wall.
[0077]
Next, a radio wave absorbing wall according to the present embodiment will be described with reference to FIG. The radio wave absorbing wall according to the present embodiment is a wall including the radio wave absorber 10 according to the present embodiment and has a radio wave absorbing function. FIG. 16 is a perspective view showing an example of the configuration of the radio wave absorbing wall according to the present embodiment. The radio wave absorbing wall 70 includes a frame including a stud 71, a runner 72 and a steady rest 73, a plurality of radio wave absorbing panels 60 attached to the frame, and an interior material 75 covering the surface of the radio wave absorbing panel 60. ing.
[0078]
Next, a radio wave absorbing ceiling according to the present embodiment will be described with reference to FIG. The radio wave absorbing ceiling according to the present embodiment is a ceiling including the radio wave absorber 10 according to the present embodiment and has a radio wave absorbing function. FIG. 17 is a perspective view showing an example of the configuration of the radio wave absorption ceiling according to the present embodiment. The radio wave absorption ceiling 80 includes a skeleton including a ridge 81 and a ridge receiver 82, a plurality of radio wave absorption panels 60 attached to the skeleton, and an interior material 85 covering the surface of the radio wave absorption panel 60. I have.
[0079]
Next, a radio wave absorbing floor according to the present embodiment will be described with reference to FIG. The radio wave absorbing floor according to the present embodiment is a floor including the radio wave absorber 10 according to the present embodiment and has a radio wave absorbing function. FIG. 18 is a perspective view showing an example of the configuration of the radio wave absorption floor according to the present embodiment. The radio wave absorption floor 90 includes a plurality of radio wave absorption panels 60 used as floor boards, a plurality of support legs 91 supporting the radio wave absorption panels 60, and an interior material 95 covering the surface of the radio wave absorption panels 60. . As the dielectric layer 12 included in the radio wave absorbing panel 60, a plate-like member having a plurality of holes penetrating in the radio wave traveling direction is used as in the examples shown in FIGS. 60 will have sufficient structural strength and load capacity to be used as a floorboard.
[0080]
Next, the principle of radio wave absorption in radio wave absorber 10 according to the present embodiment will be described. First, as shown in FIG.₁And resistance layer 13₁The principle of radio wave absorption in the radio wave absorber 10 provided with will be described. A resistance film type radio wave absorber including a radio wave reflector, a resistance film having a predetermined sheet resistance value, and a dielectric material disposed therebetween is a kind of λ / 4 type radio wave absorber, and is widely used. Are known. This resistive film type radio wave absorber focuses on the fact that the input impedance looking into the radio wave reflector side becomes infinite at a position separated by λ / 4 (λ is the wavelength of the radio wave) from the radio wave reflector. , A resistance film having a surface resistance value of 377Ω □ equal to the characteristic impedance of free space. Resistive layer 13 in the present embodiment₁Is equivalent to the above-mentioned resistance film. Further, for ease of explanation, the description will be made here ignoring the existence of the resistive film base. Further, in the following description, the normalization means that the standardization is performed using the characteristic impedance of free space (） 377Ω).
[0081]
Here, the dielectric constant of the dielectric is ε_r ^*(* Denotes a complex number.) When a radio wave is vertically incident on the radio wave absorber, the normalized input impedance Z that looks into the radio wave reflector side at a position distant from the radio wave reflector by d.^*Is given by the following equation: Note that “j” represents −１ (−1).
[0082]
Z^*= ｛1 / √ (ε_r ^*)｝ · Tanh ｛j · (2πd / λ) · √ (ε_r ^*)｝
[0083]
Assuming that the sheet resistance value of the resistive film is Rs, a normalized input impedance Z that allows for the radio wave reflector side in front of the resistive film_in ^*Is the input impedance Z^*Can be regarded as the input impedance of a circuit in which the element having the resistance value Rs and the element having the resistance value Rs are connected in parallel. Therefore, the normalized input impedance Z_in ^*Is given by the following equation:
[0084]
Z_in ^*= ｛(Rs / 377) · Z^*｝ / ｛(Rs / 377) + Z^*｝
[0085]
Here, d = λ / {4} (ε_r ^*) In case of｝, impedance Z^*Becomes infinite and the impedance Z_in ^*Becomes 1. As a result, the reflection coefficient on the surface of the resistance film becomes zero.
[0086]
Next, as shown in FIG.₁, 12₂And one resistance layer 13₁The radio wave absorber 10 provided with the radio wave absorbing performance adjusting layer 14 and the two dielectric layers 12 as shown in FIG.₁, 12₂And two resistance layers 13₁, 13₂The principle of radio wave absorption in the radio wave absorber 10 having the above will be described.
[0087]
In this case, the radio wave absorber 10 is a two-layer type radio wave absorber. This two-layer type radio wave absorber can realize radio wave absorption characteristics in which the peak of the return loss exists at any two frequencies. Therefore, according to the two-layer type radio wave absorber, it is possible to widen a frequency range in which a desired return loss is obtained, or to obtain a desired return loss in two frequency bands. The theoretical design of the two-layer type radio wave absorber in the far field can be performed using the transmission line theory similarly to the single-layer type radio wave absorber.
[0088]
Hereinafter, the resistance layer 13₁The first resistive film is referred to as a first resistive film,₂The inside resistance film is called a second resistance film. Further, the sheet resistance of the first resistance film is Rs1, and the sheet resistance of the second resistance film is Rs2. The dielectric layer 12₁The thickness of d₁And the resistive film base 21₁The thickness of d₂And the dielectric layer 12₂The thickness of d₄And the thickness of the dielectric layer 14 for radio wave absorption performance adjustment is d₅And the resistive film base 21₂The thickness of d₆And The dielectric layer 12₁The normalized characteristic impedance and propagation constant of_c1 ^*, Γ₁ ^*And Also, the resistive film substrate 21₁The normalized characteristic impedance and propagation constant of_{c 2} ^*, Γ₂ ^*And Also, the dielectric layer 12₂The normalized characteristic impedance and propagation constant of_{c 4} ^*, Γ₄ ^*And Also, the normalized characteristic impedance and the propagation constant of the dielectric layer_{c 5} ^*, Γ₅ ^*And Also, the resistive film substrate 21₂The normalized characteristic impedance and propagation constant of_{c 6} ^*, Γ₆ ^*And
[0089]
Here, a case is considered where a radio wave is vertically incident on the radio wave absorber 10. Dielectric layer 12₁Input impedance (load impedance) Z in view of the radio wave reflector 11 on the radio wave arrival side of₁ ^*Is given by the following equation:
[0090]
Z₁ ^*= Z_c1 ^*・ Tanhγ₁ ^*d₁
[0091]
Next, the resistive film substrate 21₁Input impedance Z that takes into account the radio wave reflector 11 on the radio wave arrival side of₂ ^*Is given by the following equation:
[0092]
Z₂ ^*= Z_{c 2} ^*・ ｛(Z₁ ^*+ Z_{c 2} ^*tanhγ₂ ^*d₂) / (Z_{c 2} ^*+ Z₁ ^*tanhγ₂ ^*d₂)｝
[0093]
Next, on the front surface of the first resistance film, the normalized input impedance Z₃ ^*Is given by the following equation:
[0094]
Z₃ ^*= ｛(Rs1 / 377) · Z₂ ^*｝ / ｛(Rs1 / 377) + Z₂ ^*｝
[0095]
Next, the dielectric layer 12₂Input impedance Z that takes into account the radio wave reflector 11 on the radio wave arrival side of₄ ^*Is represented by the following recurrence formula.
[0096]
Z₄ ^*= Z_{c 4} ^*・ ｛(Z₃ ^*+ Z_{c 4} ^*tanhγ₄ ^*d₄) / (Z_{c 4} ^*+ Z₃ ^*tanhγ₄ ^*d₄)｝
[0097]
Then, on the radio wave arrival side of the radio wave absorption performance adjusting dielectric layer 14 in FIG._in5 ^*Is represented by the following recurrence formula.
[0098]
Z_in5 ^*= Z_{c 5} ^*・ ｛(Z₄ ^*+ Z_{c 5} ^*tanhγ₅ ^*d₅) / (Z_{c 5} ^*+ Z₄ ^*tanhγ₅ ^*d₅)｝
[0099]
Further, a normalized input impedance Z in which the radio wave reflector 11 side is viewed in front of the second resistive film in FIG.₅ ^*Is given by the following equation:
[0100]
Z₅ ^*= ｛(Rs2 / 377) · Z₄ ^*｝ / ｛(Rs2 / 377) + Z₄ ^*｝
[0101]
Then, the resistive film base 21 shown in FIG.₂Input impedance Z that takes into account the radio wave reflector 11 on the radio wave arrival side of_in6 ^*Is represented by the following recurrence formula.
[0102]
Z_in6 ^*= Z_{c 6} ^*・ ｛(Z₅ ^*+ Z_{c 6} ^*tanhγ₆ ^*d₆) / (Z_{c 6} ^*+ Z₅ ^*tanhγ₆ ^*d₆)｝
[0103]
Two dielectric layers 12₁, 12₂And one resistance layer 13₁Radio wave absorber 10 provided with a dielectric layer 14 for adjusting radio wave absorption performance, or two dielectric layers 12₁, 12₂And two resistance layers 13₁, 13₂In the radio wave absorber 10 provided with the above, there is a condition that the reflection coefficient is set to 0 at any two frequencies. By designing and manufacturing the radio wave absorber 10 under such conditions, it is possible to realize the radio wave absorber 10 having radio wave absorption characteristics in which the peak of the return loss exists at any two frequencies.
[0104]
Similarly to the above description, a radio wave absorber 10 including three or more dielectric layers, a resistance layer disposed between adjacent dielectric layers, and a radio wave absorption performance adjusting dielectric layer 14, A radio wave absorber comprising three or more dielectric layers, and a resistive layer disposed between adjacent dielectric layers and on a radio wave arrival side of the dielectric layer disposed farthest from the radio wave reflector 11. Also for 10, the normalized input impedance on the front surface of the radio wave absorber 10 can be determined. In these radio wave absorbers 10, there are conditions for setting the reflection coefficient to 0 at three or more frequencies. By designing and manufacturing the radio wave absorber 10 under such conditions, it is possible to realize the radio wave absorber 10 having the radio wave absorption characteristic in which the peak of the return loss exists at three or more frequencies.
[0105]
Next, two examples of the radio wave absorber 10 according to the present embodiment and their radio wave absorption characteristics will be described. First, an evaluation system used to evaluate the radio wave absorption characteristics of the radio wave absorber 10 of the embodiment will be described with reference to FIG. This evaluation system is for measuring a radio wave absorption characteristic of a radio wave absorber by a reflected power method. The reflected power method radiates radio waves to the radio wave absorber to be measured, measures the amount of radio wave reflection by the radio wave absorber, and also applies to a metal plate having a reflection surface of the same area as the radio wave absorber to be measured. Similarly, this method measures the amount of radio wave reflection and measures the radio wave absorption characteristics of the radio wave absorber from the ratio of these radio wave reflection amounts.
[0106]
The evaluation system shown in FIG. 19 includes a transmitting antenna 121 that radiates radio waves to a sample 120 to be evaluated, a receiving antenna 122 that receives radio waves reflected by the sample 120, and a network analyzer 123 connected to the receiving antenna 122. And an amplifier 124 having an input terminal connected to the network analyzer 123 and an output terminal connected to the transmission antenna 121. In FIG. 19, the incident angle and the emission angle of the radio wave on the sample 120 are represented by θ. The transmitting antenna 121 and the receiving antenna 122 are arranged so that the distances from the antennas 121 and 122 to the position where the radio wave is incident on the sample 120 are equal. In the embodiment, this distance is 2 m. Further, the evaluation system is installed in the anechoic chamber 125.
[0107]
The network analyzer 123 sends a signal for transmission to the amplifier 124, and the signal is amplified by the amplifier 124 and then given to the transmission antenna 121. Further, a reception signal obtained by the reception antenna 122 is input to the network analyzer 123. The network analyzer 123 measures the characteristics of the sample based on the transmission signal and the reception signal.
[0108]
[First Embodiment]
The radio wave absorber 10 of the first embodiment has a configuration shown in FIG. The radio wave absorber 10 of the first embodiment was manufactured as follows. First, a 1 mm-thick plate-shaped resistive film substrate 21 is spray-coated using a robot coating device.₁By applying a conductive paint on one surface of the₁To form the resistance layer 13₁Was prepared. Resistive film 22₁Is 350Ω □. Similarly, a plate-shaped resistive film substrate 21 having a thickness of 2 mm is formed by spray coating using a robot coating apparatus.₂By applying a conductive paint on one surface of the₂To form the resistance layer 13₂Was prepared. Resistive film 22₂Is 900Ω □. Next, a honeycomb-shaped dielectric layer 12 is provided on a radio wave reflector 11 made of a steel plate.₁Were bonded using an epoxy adhesive. Dielectric layer 12₁Is 15 mm in diameter, and the dielectric layer 12₁Has a thickness of 18 mm. Next, the resistive film 22₁Is defined as the surface on the radio wave arrival side, and the resistance film 22₁Base 21 for resistive film on which is formed₁To the dielectric layer 12₁Was bonded to the surface on the radio wave arrival side of the above using an epoxy adhesive. Next, the resistive film 22₁The honeycomb-shaped dielectric layer 12₂Were bonded using an epoxy adhesive. Dielectric layer 12₂Is 15 mm in diameter, and the dielectric layer 12₂Has a thickness of 14 mm. Next, the resistive film 22₂Is formed on the surface opposite to the radio wave arrival side, and the resistive film substrate 21 is formed.₂Resistive film 22 formed on top₂To the dielectric layer 12₂The radio wave absorber 10 was bonded to the surface on the radio wave arrival side of the above by using an epoxy-based adhesive. The vertical and horizontal dimensions of the radio wave absorber 10 are both 30 cm.
[0109]
Using the evaluation system shown in FIG. 19, the radio wave absorption characteristics of the radio wave absorber 10 of the first embodiment in the frequency range of 2 GHz to 6 GHz were measured by the reflected power method. FIG. 20 shows the measurement results. As can be seen from FIG. 20, the radio wave absorber 10 of the first embodiment has a characteristic that the return loss is 20 dB or more at each of the frequencies of 2.4 GHz and 5.2 GHz. Therefore, the radio wave absorber 10 can be used to prevent radio interference in two frequency bands of 2.4 GHz band and 5.2 GHz band based on two standards of IEEE802.11b and IEEE802.11a. . Also, in a wireless LAN system compatible with IEEE 802.11g, which is currently under consideration for standardization, the same 2.4 GHz band radio wave as that of IEEE 802.11b will be used. The absorber 10 can also be used in this system.
[0110]
FIG. 21 shows the radio wave absorption characteristics of the radio wave absorber 10 of the first embodiment obtained by calculation based on design values and the minimum radio wave absorption characteristics of the radio wave absorber 10 obtained by calculation in consideration of manufacturing errors. . In FIG. 21, reference numeral 131 indicates a radio wave absorption characteristic based on a design value, and reference numeral 132 indicates a minimum radio wave absorption characteristic. The minimum radio wave absorption characteristic is the dielectric layer 12₁, 12₂Thickness and resistance film 22₁, 22₂Is a set of minimum values obtained by calculation for each frequency in anticipation of the manufacturing error of the sheet resistance value. From FIG. 21, according to the radio wave absorber 10 of the first embodiment, there is a possibility that a characteristic in which the return loss is 15 dB or more at each frequency of 2.4 GHz and 5.2 GHz can be obtained even if manufacturing errors are considered. It was confirmed that there was. The manufacturing error estimated here is due to the dielectric layer 12₁And dielectric layer 12₂± 1 mm and ± 1 mm respectively with respect to the design value of the thickness of the resistive film 22.₁And resistance film 22₂Are ± 10% and ± 20%, respectively, with respect to the design value of the sheet resistance value.
[0111]
[Second embodiment]
The radio wave absorber 10 of the second embodiment has the configuration shown in FIG. The radio wave absorber 10 of the second embodiment was manufactured as follows. First, a 1 mm-thick plate-shaped resistive film substrate 21 is spray-coated using a robot coating device.₁By applying a conductive paint on one surface of the₁To form the resistance layer 13₁Was prepared. Resistive film 22₁Is 250Ω □. Next, a honeycomb-shaped dielectric layer 12 is provided on a radio wave reflector 11 made of a steel plate.₁Were bonded using an epoxy adhesive. Dielectric layer 12₁Is 15 mm in diameter, and the dielectric layer 12₁Has a thickness of 20 mm. Next, the resistive film 22₁Is defined as the surface on the radio wave arrival side, and the resistance film 22₁Base 21 for resistive film on which is formed₁To the dielectric layer 12₁Was bonded to the surface on the radio wave arrival side of the above using an epoxy adhesive. Next, the resistive film 22₁The honeycomb-shaped dielectric layer 12₂Were bonded using an epoxy adhesive. Dielectric layer 12₂Is 15 mm in diameter, and the dielectric layer 12₂Has a thickness of 6 mm. Next, a 6-mm-thick plate-shaped dielectric layer 14 for adjusting radio wave absorption characteristics is placed on the dielectric layer 12.₂The radio wave absorber 10 was bonded to the surface on the radio wave arrival side of the above by using an epoxy-based adhesive. The vertical and horizontal dimensions of the radio wave absorber 10 are both 30 cm.
[0112]
Using the evaluation system shown in FIG. 19, the radio wave absorption characteristics of the radio wave absorber 10 of the second embodiment in the frequency range of 2 GHz to 6 GHz were measured by the reflected power method. FIG. 22 shows the measurement results. As can be seen from FIG. 22, the radio wave absorber 10 of the second embodiment has such a characteristic that the return loss is 20 dB or more at each of the frequencies of 2.4 GHz and 5.2 GHz. Therefore, the radio wave absorber 10 can be used to prevent radio interference in two frequency bands of 2.4 GHz band and 5.2 GHz band based on two standards of IEEE802.11b and IEEE802.11a. . Further, the radio wave absorber 10 of the second embodiment can be used in a wireless LAN system compatible with IEEE802.11g.
[0113]
Next, with reference to FIG. 23 to FIG. 27, the multipath suppression effect of the radio wave absorber 10 according to the present embodiment will be described. Multipath means that a radio wave transmitted from the transmission unit reaches the reception unit via a plurality of paths. In a wireless LAN in a room, radio waves are easily reflected by a wall surface, partition, or the like, and as a result, multipath is likely to occur. When multipath occurs, signal degradation occurs due to the combination of the fundamental wave and the delayed wave, or radio waves in a plurality of paths interfere with each other, and the received power varies depending on the position.
[0114]
Here, the result of confirming the multipath suppression effect of the radio wave absorber 10 by simulation will be described. FIG. 23 shows an indoor model used in the simulation. The model in the room has a cubic shape with a width, length and height of 2 m. In the simulation, a model was prepared in which all surfaces in the room were metal surfaces, and a model in which the ceiling surface was a metal surface and the other five surfaces were attached with the radio wave absorber 10 among the six surfaces in the room. In the simulation, the transmitting antenna is arranged at a position 141 which is 0.3 m away from one wall, is equidistant (1 m) from walls on both sides of this wall, and 0.7 m away from the floor. The transmitting antenna is a half-wave dipole antenna and radiates a 2.4 GHz vertically polarized radio wave. In the simulation, the electric field intensity distribution on the plane 142 0.7 m away from the floor was obtained by the finite integration method.
[0115]
FIG. 24 illustrates an electric field intensity distribution in a model in which all surfaces in the room are metal surfaces. FIG. 25 illustrates an electric field intensity distribution in a model in which the radio wave absorber 10 is attached to five surfaces other than the ceiling surface. 24 and 25, the electric field intensity is represented by shading, and the darker the portion, the higher the electric field intensity. From FIG. 24, it can be seen that in the model in which all surfaces in the room are metal surfaces, radio wave interference occurs due to multipath. Further, from FIG. 25, it can be seen that in the model in which the radio wave absorber 10 is attached to five surfaces other than the ceiling surface, interference of radio waves due to multipath is suppressed.
[0116]
FIG. 26 shows a temporal change of the electric field intensity at a measurement point in the plane 142 for a model in which all surfaces in the room are metal surfaces. In addition, the measurement point is 1 m away from one wall (that is, 0.7 m away from the transmission antenna) with which the transmission antenna is placed as a reference, and is separated from the walls on both sides of this wall by the same distance (1 m). 0.7m away from In FIG. 26, the portion denoted by reference numeral 151 corresponds to a direct wave that is not reflected on the indoor surface, and the portion denoted by reference numeral 152 corresponds to a reflected wave that has been reflected once on the indoor surface. The electric field strength of this reflected wave is only about 3 dB smaller than the electric field strength of the direct wave. Further, from FIG. 26, it can be seen that in this model, even after a direct wave arrives at the measurement point, the electric field intensity does not decrease for a long time due to multiple reflections of radio waves.
[0117]
FIG. 27 illustrates a temporal change of the electric field intensity at a measurement point in the plane 142 for a model in which the radio wave absorber 10 is attached to five surfaces other than the ceiling surface. In FIG. 27, a portion denoted by reference numeral 153 corresponds to a direct wave not reflected on the indoor surface, and a portion denoted by reference numeral 154 corresponds to a reflected wave reflected once on the indoor surface. The electric field strength of the reflected wave is smaller than the electric field strength of the direct wave by about 15 dB. Also, from FIG. 27, it can be seen that in this model, the electric field intensity decreases in a short time after the direct wave reaches the measurement point, and this indicates that the occurrence of multipath is suppressed.
[0118]
Next, with reference to FIG. 28 to FIG. 31, the effect of suppressing radio wave interference and radio wave leakage by the radio wave absorber 10 according to the present embodiment will be described. Here, the result of confirming by simulation the effect of suppressing the radio wave interference and the radio wave leakage by the radio wave absorber 10 will be described. FIG. 28 is a plan view of an indoor model used in the simulation, and FIG. 29 is a cross-sectional view showing a cross section of the model perpendicular to the floor. This model has a rectangular parallelepiped shape having a width of 1 m, a length of 3 m, and a height of 2.7 m. Further, in this model, a floor surface 161, a ceiling surface 162, and one wall surface 163 having a width of 1 m are metal surfaces, and the other wall surfaces are surfaces that absorb radio waves. In this model, a partition 165 having a height of 2 m is installed on the floor 161 at a position 2 m away from the wall 163. In the simulation, a model in which the partition 165 was made of metal and a model in which the partition 165 used the radio wave absorber 10 were prepared. Further, in the simulation, the transmitting antenna is arranged at a position 166 which is 1 m away from the wall 163, is equidistant from the walls on both sides of the wall 163 (0.5 m), and is 0.7 m away from the floor. The transmitting antenna is a half-wave dipole antenna and radiates a 2.4 GHz vertically polarized radio wave. In the simulation, the electric field intensity distribution in the cross section shown in FIG. 29 was obtained by the finite integration method.
[0119]
FIG. 30 shows an electric field intensity distribution in a model in which the partition 165 is made of metal. FIG. 31 shows an electric field intensity distribution in a model in which the partition 165 uses the radio wave absorber 10. 30 and 31, the electric field intensity is represented by shading, and the darker the portion, the greater the electric field intensity. FIG. 30 shows that in the model in which the partition 165 is made of metal, radio wave interference and radio wave leakage to the adjacent room have occurred. FIG. 31 shows that in the model in which the partition 165 uses the radio wave absorber 10, radio wave interference and radio wave leakage to the adjacent room are suppressed.
[0120]
As described above, according to the present embodiment, a radio wave absorber, a radio wave absorption panel, a radio wave absorption screen, a radio wave absorption wall, a radio wave absorption ceiling, and a non-flammable and lightweight, suitable for indoor use A radio wave absorbing floor can be realized. Further, by using these, it is possible to prevent radio interference such as radio wave interference and radio wave leakage in a wireless LAN constructed indoors, for example.
[0121]
Further, in the present embodiment, by adopting the basic configuration of the radio wave absorber shown in any one of FIGS. 2 to 4, the radio wave absorption characteristic having the peak of the return loss at at least two frequencies is improved. Can be realized. This makes it possible to prevent radio interference in at least two frequency bands. In particular, at least one of the 2.4 GHz band and the 5.2 GHz band is used by setting the radio wave absorption characteristics of the radio wave absorber so that the return loss is 15 dB or more at each frequency of 2.4 GHz and 5.2 GHz. Radio interference in a wireless LAN can be prevented.
[0122]
Further, in the present embodiment, the weight of the radio wave absorber can be further reduced by forming the dielectric layer by a plate-shaped member or a plate-shaped foam having a plurality of holes penetrating in the traveling direction of radio waves. In addition to this, the radio wave absorber can be provided with heat insulation. Further, by forming the dielectric layer by a plate-shaped member having a plurality of holes penetrating in the traveling direction of radio waves, sufficient strength can be ensured. Further, by forming the dielectric layer with a plate-like foam, the radio wave absorber can have a sound absorbing function.
[0123]
In addition, by forming a resistive film by applying a conductive paint on the resistive film substrate using spray coating, a radio wave absorber having a very small difference in radio wave absorption characteristics depending on the application direction of the conductive paint is realized. be able to.
[0124]
It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, the material of each layer constituting the radio wave absorber 10 is not limited to those described in the embodiment, and can be appropriately selected.
[0125]
【The invention's effect】
As explained above, the radio wave absorber according to any one of claims 1 to 18, the radio wave absorption panel according to claim 19, the radio wave absorption screen according to claim 20, the radio wave absorption wall according to claim 21, According to the radio wave absorption ceiling described in Item 22 or the radio wave absorption floor described in Item 23, a radio wave absorber, a radio wave absorption panel, a radio wave absorption screen, and a radio wave absorption wall which are nonflammable and lightweight and are suitable for indoor use. This provides an effect that a radio wave absorbing ceiling or a radio wave absorbing floor can be realized.
[0126]
Also, the radio wave absorber according to claim 2 or 5, or the radio wave absorber, radio wave absorption panel, radio wave absorption screen, radio wave absorption wall, radio wave absorption ceiling, or the radio wave absorber according to any one of claims to which claim 2 or 5 is cited. According to the radio wave absorption floor, it is possible to prevent radio interference in at least two frequency bands.
[0127]
Also, the radio wave absorber according to claim 13 or 14, or the radio wave absorber, radio wave absorption panel, radio wave absorption screen, radio wave absorption wall, radio wave absorption ceiling, or the radio wave absorber according to any one of claims 13 or 14 According to the radio wave absorption floor, it is possible to reduce the weight of the radio wave absorber and to provide the radio wave absorber with heat insulation.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a first example of a basic configuration of a radio wave absorber according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a second example of the basic configuration of the radio wave absorber according to one embodiment of the present invention.
FIG. 3 is a sectional view showing a third example of the basic configuration of the radio wave absorber according to one embodiment of the present invention.
FIG. 4 is a sectional view showing a fourth example of the basic configuration of the radio wave absorber according to one embodiment of the present invention.
FIG. 5 is a cross-sectional view showing another example of the configuration of the radio wave absorber according to one embodiment of the present invention.
FIG. 6 is an explanatory diagram illustrating a method for forming a resistance layer according to an embodiment of the present invention.
FIG. 7 is a perspective view showing a first example of a configuration of a radio wave absorber having a dielectric layer formed by a plate-shaped member having a plurality of holes.
FIG. 8 is a perspective view showing a second example of the configuration of a radio wave absorber having a dielectric layer formed by a plate-shaped member having a plurality of holes.
FIG. 9 is a perspective view showing a third example of a configuration of a radio wave absorber having a dielectric layer formed by a plate-like member having a plurality of holes.
FIG. 10 is a perspective view showing a fourth example of the configuration of a radio wave absorber having a dielectric layer formed by a plate-like member having a plurality of holes.
FIG. 11 is a cross-sectional view showing an example of an installation state of a radio wave absorbing partition whose main part is constituted by a radio wave absorber.
12 is a sectional view showing an example of a sectional structure of the radio wave absorbing screen shown in FIG.
13 is a sectional view showing another example of the sectional structure of the radio wave absorbing screen shown in FIG.
FIG. 14 is a cross-sectional view illustrating an example of an installation state of a radio wave absorbing screen configured by attaching a radio wave absorbing panel to a core of the screen.
FIG. 15 is a cross-sectional view showing another example of an installation state of a radio wave absorbing screen configured by attaching a radio wave absorbing panel to a core material of the screen.
FIG. 16 is a perspective view showing an example of a configuration of a radio wave absorbing wall according to one embodiment of the present invention.
FIG. 17 is a perspective view showing an example of a configuration of a radio wave absorbing ceiling according to one embodiment of the present invention.
FIG. 18 is a perspective view showing an example of a configuration of a radio wave absorption floor according to one embodiment of the present invention.
FIG. 19 is an explanatory diagram showing an evaluation system used for evaluating the radio wave absorption characteristics of the radio wave absorber of the example in one embodiment of the present invention.
FIG. 20 is a characteristic diagram showing a radio wave absorption characteristic of the radio wave absorber of the first example in one embodiment of the present invention.
FIG. 21 is a graph showing the minimum radio wave absorption obtained by calculation in consideration of the radio wave absorption characteristic and the manufacturing error calculated based on the design value for the radio wave absorber of the first example of the embodiment of the present invention; It is a characteristic view which shows a characteristic.
FIG. 22 is a characteristic diagram showing a radio wave absorption characteristic of the radio wave absorber of the second example in one embodiment of the present invention.
FIG. 23 is a perspective view showing an indoor model used in a simulation for confirming a multipath suppression effect of the radio wave absorber according to one embodiment of the present invention.
FIG. 24 is an explanatory diagram showing a result of a simulation for confirming a multipath suppression effect by the radio wave absorber according to one embodiment of the present invention.
FIG. 25 is an explanatory diagram showing a result of a simulation for confirming a multipath suppression effect by the radio wave absorber according to one embodiment of the present invention.
FIG. 26 is a characteristic diagram showing a result of a simulation for confirming a multipath suppressing effect by the radio wave absorber according to one embodiment of the present invention.
FIG. 27 is a characteristic diagram showing a result of a simulation for confirming a multipath suppression effect by the radio wave absorber according to one embodiment of the present invention.
FIG. 28 is a plan view showing a model of a room used in a simulation for confirming an effect of suppressing radio wave interference and radio wave leakage by the radio wave absorber according to one embodiment of the present invention.
FIG. 29 is a sectional view of the model shown in FIG. 28;
FIG. 30 is an explanatory diagram showing the results of a simulation for confirming the effect of suppressing the radio wave interference and the radio wave leakage by the radio wave absorber according to one embodiment of the present invention.
FIG. 31 is an explanatory diagram showing the results of a simulation for confirming the effect of suppressing the radio wave interference and the radio wave leakage by the radio wave absorber according to one embodiment of the present invention.
[Explanation of symbols]
10 ... radio wave absorber, 11 ... radio wave reflector, 12, 12₁, 12₂... Dielectric layers 13, 13₁, 13₂... Resistive layer, 14 ... Dielectric layer for adjusting radio wave absorption characteristics, 21₁, 22₁... Base for resistive film, 21₂, 22₂... resistance film.

Claims (23)

A non-flammable radio wave reflector,
A non-combustible dielectric layer mainly composed of an inorganic material and disposed on a radio wave arrival side of the radio wave reflector,
A plate- or sheet-shaped resistive film base mainly composed of an inorganic material, and a resistive layer including a resistive film formed on the resistive film base and disposed on the radio wave arrival side of the dielectric layer. ,
A radio wave absorber characterized in that the whole is nonflammable. A non-flammable radio wave reflector,
An n-layer (n is an integer of 2 or more) non-combustible dielectric layer mainly composed of an inorganic material and disposed on a radio wave arrival side of the radio wave reflector;
Including a plate-shaped or sheet-shaped substrate for a resistance film mainly composed of an inorganic material and a resistance film formed on the substrate for a resistance film, the substrate is disposed between two adjacent dielectric layers (n-1). ) Layer of resistance layer,
Mainly composed of an inorganic material, comprising a dielectric layer for adjusting radio wave absorption characteristics arranged on the radio wave arrival side of the dielectric layer farthest from the radio wave reflector,
A radio wave absorber characterized in that the whole is nonflammable. 3. The radio wave absorber according to claim 2, having a characteristic that the return loss is 15 dB or more at a plurality of frequencies. 3. The radio wave absorber according to claim 2, having a characteristic that the return loss is 15 dB or more at each of 2.4 GHz and 5.2 GHz. A non-flammable radio wave reflector,
An n-layer (n is an integer of 2 or more) non-combustible dielectric layer mainly composed of an inorganic material and disposed on a radio wave arrival side of the radio wave reflector;
Including a plate-shaped or sheet-shaped substrate for a resistance film mainly composed of an inorganic material, and a resistance film formed on the substrate for a resistance film, between the two adjacent dielectric layers and the most from the radio wave reflector. An n-layer resistance layer disposed on the radio wave arrival side of the far dielectric layer,
A radio wave absorber characterized in that the whole is nonflammable. The radio wave absorber according to claim 5, wherein a sheet resistance value is smaller as the resistance film is closer to the radio wave reflector. 7. The radio wave absorber according to claim 5, having a characteristic that the return loss is 15 dB or more at a plurality of frequencies. 7. The radio wave absorber according to claim 5, wherein the radio wave absorber has a characteristic that the return loss is 15 dB or more at each frequency of 2.4 GHz and 5.2 GHz. The radio wave absorber according to any one of claims 1 to 8, further comprising an interior material arranged to cover a surface farthest from the radio wave reflector. The radio wave absorber according to any one of claims 1 to 9, wherein a surface farthest from the radio wave reflector is coated. The radio wave reflector includes a plate-shaped radio wave reflector base mainly made of an inorganic material, and a conductive film disposed on a surface of the radio wave reflector base on a radio wave arrival side. The radio wave absorber according to claim 1. The radio wave absorber according to any one of claims 1 to 11, wherein the radio wave reflector is attached to the dielectric layer with an inorganic adhesive or an organic adhesive. 13. The dielectric layer according to claim 1, wherein the dielectric layer is formed of a plate-shaped member having a plurality of holes penetrating in a traveling direction of a radio wave or a plate-shaped foam. Radio wave absorber. The dielectric layer has a first surface on the radio wave arrival side and a second surface on the opposite side, and at least the first surface of the first and second surfaces is mainly 14. The radio wave absorber according to claim 13, wherein the radio wave absorber is covered by a plate-shaped or sheet-shaped member made of an inorganic material. 15. The resistive film according to claim 1, wherein the resistive film is formed by mixing a conductive material with a coating agent, and is formed of a conductive paint applied on the resistive film base. Radio wave absorber. The radio wave absorber according to claim 15, wherein the coating agent includes at least one of an inorganic coating agent and an organic coating agent. 17. The radio wave absorber according to claim 15, wherein the conductive material includes at least one of carbon powder, carbon fiber, metal powder, and metal fiber. 18. The radio wave absorber according to claim 1, wherein the resistance layer is bonded to the dielectric layer with an inorganic adhesive or an organic adhesive. A panel including the radio wave absorber according to any one of claims 1 to 18, wherein the panel is used as at least a part of any of a partition, a wall, a ceiling, and a floor. A screen comprising the radio wave absorber according to claim 1, wherein the screen has a radio wave absorption function. A radio wave absorbing wall comprising the radio wave absorber according to any one of claims 1 to 18, wherein the wall has a radio wave absorbing function. A radio wave absorption ceiling comprising the radio wave absorber according to any one of claims 1 to 18, wherein the ceiling has a radio wave absorption function. A radio wave absorption floor comprising the radio wave absorber according to any one of claims 1 to 18, having a radio wave absorption function.

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