JPH10224076A - Wave absorbing wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wave absorbing wall having a large plane shape, thin, light and appropriate for false image prevention measures for aerial raders. SOLUTION: Reinforcing bars 12 as reflecting members are attached to the rear of a first glass fiber containing mortar board 10, and are short-circuited. To the first glass fiber containing mortar board 10, 60wt.% of Mn-Zn ferrite powder (powder diameter 0.6mm or smaller) is added and formed into a platy shape by spraying. Then, a wave absorbing wall having an excellent absorbing property in 1GHz band can be constituted. As compared with a ferrite tile, it is possible to mass-produce first glass fiber containing mortar boards 10 of larger shapes. And it becomes possible to obtain thinner and lighter ones, since thick concrete is unnecessary unlike before.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave absorbing wall for eliminating an adverse effect (radio wave obstruction) caused by radio wave reflection generated on various types of wall surfaces. It is about.

[0002]

2. Description of the Related Art As measures against television ghosts which are famous as radio wave barriers, for example, Japanese Patent Publication No.
As shown in Japanese Patent Publication No. 55-49798 and Japanese Patent Publication No. 55-49798, a tile made of a ferrite sintered body having a good radio wave absorption characteristic in a VHF band or a UHF band is provided on the outer wall surface of a building (high-rise building) such as concrete. Is generally performed.

[0003] The above-mentioned invention is a basic patent,
After that, various improvements have been made. However, the layout of tiles made of ferrite sintered bodies and the method of mounting are all based on tiles (ferrite plates).

FIG. 7 shows an example of a radio wave absorbing curtain wall for a TV ghost using such tiles. That is, a tile 2 made of a ferrite sintered body is attached to the surface of the concrete 1 constituting the outer wall at a predetermined interval, and a decorative plate 3 is bonded and integrated on the surface. In addition, a reinforcing bar cage 4 is embedded in the concrete 1.

[0005] Focusing on the actual manufacturing process,
The tile 2 is attached to a predetermined position on the back surface of the decorative plate 3 using an adhesive, and then the reinforcing steel basket 4 is disposed at a predetermined distance (for example, about 3 cm) using the fixing hardware 5. In this state, a concrete form (not shown) covering the periphery is installed, and then concrete is poured (thickness: 15 cm) to manufacture (the thickness of the entire curtain wall is 17 cm).
About). Therefore, the tile 2 is buried in the concrete 3 as shown in FIG.

[0006]

However, in the case of using the conventional ferrite sintered body tile 2 described above, since the ferrite sintered body itself is very heavy, the tile 2 made of such ferrite sintered body is stuck. A problem arises in the workability and safety of wearing. In addition, since the tile 2 has a very small planar shape of only about 100 mm square, the attaching operation becomes very complicated.

Further, since the tile 2 made of a ferrite sintered body is heavy, it is necessary to ensure the strength for holding the ferrite sintered body, the wind resistance and the fireproof function, and the thickness of the concrete 3 is also as described above. And the weight of the concrete 3 increases accordingly. As a result, the entire building becomes extremely heavy, and foundation work and steel frame work must be performed to support the weight of the building, and the processing is complicated, which leads to a prolonged construction and higher costs.

Further, the radio wave absorption characteristics slightly change depending on the composition and dimensions of the ferrite constituting the tile 2.
Therefore, it is necessary to dimension the tile 2 with high precision, but it is difficult to accurately dimension the tile 2 in combination with shrinkage during sintering. In addition, there is a possibility that cracks or chips may occur after manufacturing, and the tile in which such a situation occurs becomes a defective product. Therefore, due to the difficulty in dimensioning and the cracks and the like, the yield at the time of manufacturing a tile having desired characteristics is poor, and the cost is further increased. Further, in practice, determination of a dimension and a shape having desired characteristics is also performed through trial and error, and a complicated process is required because the shrinkage ratio varies.

On the other hand, a control tower, which is one of the airport facilities, communicates with an airplane taking off and landing, and detects a flying object existing in a monitoring area using an aeronautical radar. When such processing is performed, radio waves of a predetermined frequency are used. Therefore, if there is a high-rise building around the control tower in the direction of incoming and outgoing radio waves, the radio waves will be reflected on the outer wall of the high-rise developer, and the airplane will be in a place where the results of monitoring by aeronautical radar do not exist. However, there is a problem that a false image such as the above occurs.

Conventionally, since there is no high-rise building that creates a false image in the vicinity because it is installed near the airport near the seaside or the like, there is no need to pay much attention to countermeasures against the false image based on the building. . However, recently, high-rise buildings are being constructed near airports such as near the seashore or at sea, and measures against the false images are also required.

Therefore, it has been considered that a radio wave absorbing wall is formed by using a ferrite tile in the same manner as a conventional countermeasure against TV ghost. However, since aeronautical radar is in the 1 GHz band, ferrite tiles cannot almost completely absorb radio waves in such a frequency band.

Further, even if a ferrite tile capable of absorbing radio waves in the 1 GHz band can be formed, in the case of the mortar containing fibers, which is the object of the present invention, a large force is applied to the tile when the mortar is solidified due to a large shrinkage. In addition, the tiles may be cracked or broken, and eventually, the desired absorption characteristics may not be obtained.

Further, as described above, the radio wave absorbing wall using ferrite tiles is very heavy, so if a building with radio wave absorbing measures on the fragile sea or near the coast is installed, the ground subsidence may occur. It may not be practically usable.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and has as its object to solve the above-mentioned problems, to have a large planar shape and a small wall thickness, to be light in weight. It can be easily installed, has good radio wave absorption characteristics in any frequency band, and especially has a radio wave absorption wall that can absorb radio waves in the 1 GHz band or more and can almost completely absorb radio waves for aeronautical radar. To provide.

[0015]

In order to achieve the above-mentioned object, in a radio wave absorbing wall according to the present invention, a ferrite powder is mixed with fiber-containing mortar to form a plate, and a radio wave in a desired frequency band is formed. (Claim 1). Here, the “fiber” is mixed in the mortar as a reinforcing material such as a glass fiber, a vinylon fiber, an aramid fiber, a carbon fiber, and a steel fiber, and is not limited to those exemplified above.

The ferrite powder mixed in the mortar is
It performs the same function as conventional ferrite tiles and absorbs radio waves radiated on the wall. The powder can be handled in the same manner as the aggregate mixed in the mortar, and can be easily mixed. In addition, since it is not necessary to form the dimensions and shapes with high precision, the manufacturing is facilitated. And by changing the type, particle size and mixing amount of ferrite powder,
Since the frequency bands to be absorbed are different, a radio wave absorbing wall corresponding to an arbitrary frequency band can be constructed.

The ferrite powder is mixed in the mortar, and if it is mixed in a predetermined amount, desired radio wave absorption characteristics are exhibited. Therefore, the wall material is thickened to support the ferrite tile like a ferrite tile. There is no necessity, and the thickness of the radio wave absorption wall of the present invention may be set to a thickness required for the wall material, so that the wall thickness is reduced and the weight can be reduced. Moreover, in the present invention, since the mortar containing fibers is used, the strength is large and the member size (thickness) can be reduced as compared with the conventional mortar, so that the weight can be reduced and the effect is more remarkable.

The radio wave absorbing wall having such a configuration can be used as an inner wall (partition wall) of a building, a wall material of an anechoic chamber or a dark box, and further, can be used as an outer wall of a building (claim). Item 2). To show an example of a structure when used as an outer wall, a fiber-containing mortar is formed by mixing ferrite powder, and a decorative tile is provided on a surface of a plate-like material that can absorb radio waves in a desired frequency band, A reflection member can be provided on the back side of the plate-like object (claim 3). By using it for the outer wall in this way, it is effective for TV ghost countermeasures and countermeasures against false images in aeronautical radar, and high-rise buildings can be installed at arbitrary locations.

The material and mixing conditions of the ferrite powder to be mixed are appropriately set according to the frequency of the radio wave to be absorbed.
In the case of absorbing radio waves in the z-band, it is a powder of Mn-Zn-based ferrite or Mg-Zn-based ferrite having a particle size of 0.6 mm or less and mixing 50 to 60 wt%. 4).

The above conditions are set for the following reasons. That is, when a wall material is formed of fiber-containing mortar, it is generally sprayed. That is, the mortar is injected from the nozzle. Therefore, if an object having a particle diameter larger than the diameter of the nozzle exists in the mortar, the spraying is not performed naturally. Therefore, in consideration of the diameter of the nozzle currently used, the particle diameter is set to 0.6 mm or less as described above so that the nozzle can smoothly eject without clogging.

The larger the particle size, the better the absorption characteristics (peak value). Therefore, it is preferable to use one having a diameter of 0.6 mm or less as large as possible. Also, the reason why the mixing range is set to 50 to 60 wt% is that the particle diameter is set to 0.6 mm or less as described above. If the mixing range is less than 50 wt%, the magnetic permeability becomes too low and sufficient absorption characteristics cannot be obtained ( This is because the peak value becomes smaller). The lower limit is due to the upper limit of the particle size. For example, when the particle size is set to 1.0 mm, even if the mixing amount is 40 wt%, the absorption that can withstand practical use is sufficient. Characteristics are obtained. Further, the upper limit is set to 60 wt% because no more mixing is possible when the spraying method is used.

[0022]

FIG. 1 shows an embodiment of a radio wave absorbing wall according to the present invention. As shown in the figure, a decorative board 11 is mounted on the surface of a plate-shaped first glass fiber-containing mortar board 10 which is a main component of the present invention. Further, a reinforcing bar 12 as a reflecting member is mounted on the back surface of the first mortar board 10 containing glass fibers. Then, the second glass fiber-containing mortar board 13 is provided on the back surface of the reinforcing bar 12.
Is installed.

The decorative plate 11 is formed using a stone plate, a tile, and other exterior materials. After the radio wave absorber 10 is formed, it is arranged on the surface of the radio wave absorber 10 in a predetermined layout. As an example, as shown in FIG. 2 (A), they are arranged vertically and horizontally, and when viewed microscopically, as shown in FIG.
Adjacent decorative boards 11 are arranged at predetermined intervals. Further, the reinforcing bar 12 is formed in a shape in which a vertical bar and a horizontal bar are assembled in a lattice shape, and short-circuited by the reinforcing bar 12. In addition, the mortar board 13 containing the second glass fiber is
There is no function as a radio wave absorption, and it is provided to have a desired thickness so as to exert a proper role as a building material such as giving a predetermined strength to the whole radio wave absorption wall.

Here, the first glass fiber-containing mortar board 10 which is a main part of the present invention will be described. In this example,
A predetermined ferrite powder is mixed with a mortar containing glass fiber to form a plate shape. As the ferrite to be used, for example, Mn-Zn based ferrite or Mg-
Zn-based ferrite can be used. The particle size of the ferrite powder, the mixing amount, the thickness of the first glass fiber-containing mortar board 10, and the like take appropriate values according to the frequency band to be subjected to radio wave absorption.

The ferrite powder can be formed by firing a ferrite once to form a sintered body and pulverizing the obtained sintered body. Then, when such pulverization is performed, the particle size of the obtained powder varies, but it is sufficient to extract the powder within the range of the particle size at which desired characteristics can be obtained by sieving. Therefore, there is no problem in the present invention, even if a part is missing before or after the sintered body is obtained.

In the illustrated example, the reinforcing bar 12 is in direct contact with the back surface of the first glass fiber-containing mortar board 10, but the present invention is not limited to this. For example, the second glass fiber-containing mortar may be used. It may be arranged on the back side of the board 13. In addition, a metal mesh or a metal plate may be used as the reflection member instead of the reinforcing bar.

** Experimental Results Next, various experiments described below were performed to verify the effects of the present invention. That is, first, Mn-Zn-based ferrite having a particle size of 0.6 mm or less is mixed in a mortar containing glass fiber at 60 wt%. Then, the mixture is formed into a plate shape by a spraying method using the mixture. This is the first glass fiber-containing mortar board described above. And
On the surface, a decorative panel is installed, and on the back side, a normal glass fiber mortar board is placed with a reinforcing bar in between,
A structure as shown in FIG. 1 is manufactured. In addition, the thickness of the first glass fiber-containing mortar board on the back side of the decorative board is 6
mm.

As a result, as shown in FIG.
It peaked at MHz, and radio wave absorption characteristics that could be absorbed in a relatively wide band were obtained. And, in this radio wave absorption wall, 1030-10
Since high absorption characteristics are obtained in a frequency band of 90 MHz, when a radio wave absorption wall related to the outer wall of a high-rise building around an airport is used, there is no reflection on the wall, and no false image occurs.

On the other hand, except that the ferrite to be mixed is Mg-Zn ferrite and the thickness of the first glass fiber-containing mortar board on the back side of the decorative board is 11 mm, the radio wave absorption is performed in the same manner as described above. The wall was manufactured. As a result, a radio wave absorption characteristic as shown in FIG. 4 was obtained. Even with such a configuration, characteristics having good absorption characteristics were obtained with respect to 1 GHz band radio waves used as aeronautical radars.

Further, an Mn-Zn ferrite having a particle size of 50 μm or less was added to the mortar containing glass fiber in an amount of 50 wt.
%, And the thickness of the first glass fiber-containing mortar board on the back side of the decorative board was adjusted to 8 mm. Otherwise, the radio wave absorbing wall was manufactured in the same manner as in each of the above-described experiments. Then, as shown in FIG. 5, characteristics having good absorption characteristics were obtained for radio waves in the 2 GHz band.

Further, in a mortar containing glass fiber,
Mg-Zn ferrite having a particle size of 0.1 mm or less
0 wt% was mixed, and the thickness of the first glass fiber-containing mortar board on the back side of the decorative board was adjusted to 8 mm. Otherwise, the radio wave absorbing wall was manufactured in the same manner as in each of the above-described experiments. Then, as shown in FIG. 6, characteristics having good absorption characteristics were obtained for radio waves in the 3 GHz band.

Although illustration of specific frequency characteristics is omitted, a radio wave absorber was manufactured under various conditions.
When the amount of ferrite mixed increases, the peak of the absorption characteristic shifts to the lower frequency side, and when the amount of ferrite mixed decreases, the peak of the absorption characteristic shifts to the higher frequency side.

As for the thickness of the sheet, the thicker the sheet, the larger the amount of ferrite present. As a result, the peak of the absorption characteristic shifts to the lower frequency side. The peak shifts to the high frequency side.

Therefore, a radio wave absorber having good absorption characteristics at a desired frequency can be manufactured by changing the mixing amount and the plate thickness according to the specifications and conditions. In particular, the dimensional accuracy is the same as that of ordinary concrete casting, so it is easy to form into the desired dimensional shape, and there is almost no shrinkage due to firing like a conventional tile. A radio wave absorber with good performance is obtained.

When the above range is satisfied, good characteristics can be obtained in the GHz band. However, in order to improve the radio wave absorption characteristics in the frequency band outside the range, it is needless to say that the above conditions are not satisfied. Good. By lowering the frequency band at the peak portion of the absorption characteristics, the VHF band and the U
A radio wave absorbing wall having good absorption characteristics can be manufactured in the HF band, which is suitable for a measure against television ghost. Furthermore, in the present invention, the present invention is not limited to the outer wall of a building, and may be used for an inner wall, or used for a wall of an anechoic chamber or an anechoic box.
The field of application can be varied.

In the above embodiment, glass fiber is used as the fiber to be mixed into the mortar. However, the present invention is not limited to this, and various fibers used as building materials may be used. Can be used.

[0037]

As described above, in the radio wave absorbing wall according to the present invention, the overall thickness can be reduced and the weight can be reduced. As a result, the inner dimensions can be made larger for a building having the same outer dimensions, and since it is lightweight, foundation work and the like can be easily performed, and assembling work can also be easily performed. In particular, fiber-containing mortars have higher strength than ordinary mortars and can be reduced in member size (thickness), so that the weight can be reduced, and such effects are more remarkably exhibited.

The radio wave absorber can be easily manufactured in the same shape and the dimensions can be formed with high precision, so that desired characteristics can be easily obtained. further,
It is possible to produce a relatively large shape compared to a conventional ferrite tile, and it is easy to assemble and construct on site. In addition, dimensional accuracy when producing a sintered body by firing a predetermined ferrite is not required, and even if the sintered body is broken during firing, there is no problem because it is finally pulverized, so there is no problem. It can be easily manufactured.

Further, in the case of a conventional ferrite tile, the direction of polarization that can be absorbed is determined by the layout of the arrangement.
The performance is further improved because it is independent of the polarization direction. Furthermore, since the peak band is wider than that of ferrite tiles, the radio wave absorption characteristics of the final product can be improved without requiring high-precision control of the dimensional shape and composition ratio of the formed product from this point. Desired characteristics are obtained.

Further, particularly when configured as in claim 4, it is possible to absorb radio waves used for aeronautical radars in the 1 GHz band or higher, and it is possible to reliably suppress generation of false images in the radar.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of an embodiment of a radio wave absorbing wall according to the present invention.

FIG. 2A is a front view thereof. (B) is a side view thereof.

FIG. 3 is a graph showing an example of a radio wave absorption characteristic of the product of the present invention.

FIG. 4 is a graph showing an example of a radio wave absorption characteristic of the product of the present invention.

FIG. 5 is a graph showing an example of a radio wave absorption characteristic of the product of the present invention.

FIG. 6 is a graph showing an example of a radio wave absorption characteristic of the product of the present invention.

FIG. 7 is a diagram showing a conventional example.

[Explanation of symbols]

 Reference Signs List 10 first mortar board containing glass fiber 11 decorative board 12 reinforcing bar 13 mortar board containing glass fiber

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuo Yamada 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Hideo Tanaka 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Wignaraja Shiva Kumaran 1-25-1, Nishishinjuku, Shinjuku-ku, Tokyo Taisei Construction Co., Ltd. (72) Inventor Masao Kosaka 3-1-2 Yoyogi, Shibuya-ku, Tokyo Showa Mining Co., Ltd. (72) Inventor Akira Matsuyama 891-5 Yamaki, Ichihara-shi, Chiba (72) Inventor Manabu Teranishi 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. (72) Inventor Yoshitake Masumi Fuji Electric Chemical Co., Ltd. 5-36-11 Shimbashi, Minato-ku, Tokyo (72) Inventor Makoto Ishikura 5-36-11 Shimbashi, Minato-ku, Tokyo Fuji Electric Chemical Co., Ltd. In-house

Claims (4)

[Claims] A radio wave absorbing wall formed by mixing a ferrite powder with a fiber-containing mortar to form a plate and absorbing radio waves in a desired frequency band. 2. A plate-like object (10) formed by mixing ferrite powder with fiber-containing mortar and capable of absorbing radio waves in a desired frequency band is an outer wall of a building. Radio wave absorption wall. 3. A decorative plate (11) is provided on a surface of a plate-like material (10) capable of absorbing radio waves in a desired frequency band by mixing ferrite powder with a mortar containing fibers. A radio wave absorbing wall comprising a reflecting member (12) provided on the back side of a plate-like object. 4. The ferrite powder is a powder of Mn—Zn-based ferrite or Mg—Zn-based ferrite, and has a particle diameter of 0.6 mm or less and is mixed by 50 to 60 wt%. The radio wave absorbing wall according to claim 1.