JPH11126991A - Radio wave absorbing wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio-wave absorbing characteristics and weather- resistance which is equal to or better than normal as well as high strength for, especially, good workability by setting a distance between a ferrite tile and a reflector to a specific value or less. SOLUTION: With an interval equal to 10% or longer than the length of a ferrite tile 1 in magnetic-field component direction, the ferrite tile 1 is provided in the magnetic-field component direction. With less than 10%, a required radio-wave absorption characteristics is not provided at high frequency. In addition, each ferrite tile 1 is attached with a reflection foil body 5 of metal thin plate and foil, on its indoor side, as a radio-wave reflector, in such way as with no interruption in electric-wave direction. When a reflection bar is employed as a reflector, with the use of stainless steel bar or reinforcing-bar processed for lust-proof, it is provided near the ferrite tile 1, within 15 mm from it. Thus, a radio-wave absorbing wall of weather-resistance, workability, and strength which are equal to or better than normal is obtained.

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 a VHF band and a UHF band using a ferrite tile, and the distance between the ferrite tile and a reflector provided on the back side in the direction of the arriving radio wave is reduced to 15 mm or less. The present invention relates to a radio wave absorption wall which can obtain excellent radio wave absorption characteristics and realize excellent weather resistance, workability, and strength.

[0002]

2. Description of the Related Art In recent years, the occurrence of television wave reception disturbance (television ghost failure) due to the rise of buildings has become a major social problem, and a television ghost radio wave absorption wall (panel) used as a countermeasure is becoming indispensable. In particular, ferrite-based radio wave absorbers are thin, exhibit good radio wave absorption characteristics, have excellent weather resistance, and are chemically stable, and are therefore frequently used as radio wave absorbers to be attached to building walls.

Conventionally, a sintered ferrite utilizing the magnetic resonance phenomenon, that is, a plate made of Ni—Zn based or Mn—Zn based sintered ferrite is provided with a metal plate backing, so that the radio wave absorbing ability is improved. These ferrite-based radio wave absorbers are generally used in dimensions of 100 mm × 100 m.
m, a tile having a thickness of about 5 to 10 mm, and these are laid and constructed to form an absorbing wall.

[0004] For example, Japanese Patent Publication No. 55-13600 discloses a reinforcing material for solving the problem that a ferrite plate is peeled off due to a difference in thermal expansion coefficient between a ferrite plate and a metal plate in a conventional radio wave absorber. 100mm × 100 on the surface of buried concrete, mortar, etc.
A three-layer structure has been proposed in which a magnetic plate of a ferrite tile having a thickness of 2 mm is fixed and an exterior material such as mortar is provided on the surface of the magnetic plate.

Also, Japanese Patent Publication No. 55-49798 discloses
For the purpose of reducing the number of ferrite plates used and increasing the practicality as a building material without lowering the radio wave absorption characteristics, the ferrite plates are coupled so as to be continuous in the direction of the magnetic field component of the incoming radio wave, and the electric field component Disclosed is a configuration in which the gaps are arranged so as to be discontinuous in the direction.

[0006] However, in the above configuration, when it is required from an aesthetic viewpoint that the exterior material disposed outside the ferrite plate is made of natural stone, porcelain tile, or the like, the exterior material must have sufficient strength to have sufficient strength. It is necessary to increase the thickness of the material, and by attaching this thick exterior material, the radio wave absorption characteristics deteriorate.

[0007] When a radio wave absorber is used to prevent interference from unnecessary reflected radio waves of a high-rise building, generally,
The radio wave absorption characteristics in which the return loss in a frequency band of about 100 MHz to 200 MHz is 10 to 15 dB (absolute value) or more are required. In the above configuration, the absorption characteristics at 100 MHz are good, but the 200 MHz. The characteristics cannot be sufficiently obtained, and only a very narrow band radio wave absorption characteristic can be obtained.

[0008]

In order to sufficiently exhibit the radio wave absorption performance of the ferrite radio wave absorber, a radio wave reflector is required on the back side in the direction of the radio wave coming from the ferrite. Structural rebar plays this role.

Japanese Patent Application Laid-Open No. 2-170599 discloses a structure in which ferrite is disposed on a radio wave reflecting material such as a reinforcing bar, a wire mesh, or a metal plate. Strength cannot be maintained. In addition, concrete wraps around the rebar, but if it is close to the outer wall surface, it tends to rust and is not practical. Therefore, in practice, it is necessary to embed the reflector in the concrete while keeping the fog of about 30 mm.

As a countermeasure against TV ghost caused by the conventional radio wave absorption wall, the VHF band (around 100 to 200 MHz) has been the mainstream.
There is a demand for a radio wave absorption wall having good return loss characteristics in the UHF band (470 to 770 MHz). Each of the above-mentioned radio wave absorption walls aims at absorbing unnecessary radio waves in the VHF band.

[0011] The inventors of the present invention aim at a radio wave absorbing wall having a good return loss characteristic in the UHF band, since the impedance of concrete itself cannot be ignored, the radio wave absorbing performance is susceptible to the influence of concrete cover. However, no proposal has been made on the configuration of a reflector that is optimal for a radio wave absorption wall for the UHF band.

The present invention provides a radio wave absorbing wall for the UHF band which is newly required, having a radio wave absorbing property and weather resistance equal to or higher than those of the conventional one, having a high strength and particularly excellent workability. It aims to provide radio wave absorption walls.

[0013]

Means for Solving the Problems The present inventors have used sintered ferrite tiles for the purpose of forming a radio wave absorbing wall for the UHF band having a structure excellent in weather resistance, workability, and strength. As a result of various examinations of the arrangement, the ferrite tiles were arranged with a large gap in the direction of the magnetic field component of the arriving radio wave, and the tiles were arranged almost continuously in the direction of the electric field of the arriving radio wave. When the plate or foil is attached to the back of the tile, the workability is excellent, the peak value of the return loss is 470 to 770 MHz, and-
It has been found that a radio wave absorbing wall having a characteristic of 15 dB or less can be obtained, and that the configuration of the reflector is also effective in the VHF band.

Further, the present inventors have found that when a reinforcing bar is used as a reflector of the radio wave absorbing wall for the UHF band, the performance of the reflector is insufficient if the pitch of the horizontal streaks parallel to the direction of the electric field component is larger than 40 mm. We found that it is necessary to arrange the corrosion-resistant reflectors at an appropriate pitch because the radio wave absorption performance of the radio wave absorption wall decreases.

Further, the present inventors provide a support frame having a simple structure by disposing a support member for supporting the weight of each tile at least between sintered ferrite tiles in the direction of the magnetic field component of the arriving radio wave. It has been found that the dry method can be more easily performed by using.

Furthermore, the present inventors arrange the non-conductive material having no water absorption in the gap between the sintered ferrite tiles in the direction of the magnetic field component of the arriving radio wave, so that the magnetic gap becomes accurate and the dielectric The inventor of the present invention has found that since the rate is stable, there is no deterioration or change with time of the radio wave absorption characteristics.

[0017]

1 is a perspective explanatory view and a sectional view showing an embodiment of a radio wave absorbing wall according to the present invention. The ferrite tile 1 is used as a magnetic material, and the ferrite tiles 1 are arranged almost continuously in the direction of the electric field component of the arriving radio wave (the left and right direction E in the figure), and are arranged in the concrete 4 with a gap in the direction of the magnetic field component (the vertical direction H in the figure). It is configured to be covered with the exterior material 2 on the outside. Reference numeral 3 in the figure denotes a structural reinforcing bar in the concrete 4.

Here, in order to shift the peak of the return loss of the radio wave absorbing wall to a higher frequency and obtain good radio wave absorption characteristics in the UHF band, the length of the ferrite tile 1 in the direction of the magnetic field component is 10% or more. The ferrite tile 1 is arranged in the direction of the magnetic field component (H direction) with a gap.
If it is less than 0%, required radio wave absorption characteristics cannot be obtained at high frequencies. The tile interval is most preferably 30 to 80%.

Further, here, a reflective foil member 5 made of a thin metal plate or foil is attached to each ferrite tile 1 on the indoor side as a radio wave reflector. Yes, it can be easily attached to the back of the ferrite tile 1 with a double-sided tape or an adhesive, so that workability is very good.

The material of the reflecting foil member 5 is preferably a material having corrosion resistance and conductivity. A thin foil plate such as Al or conductive tape, a tin plate, or a stainless steel foil can be selected, as shown in FIG. When the reflective foil member 5 is installed on the back surface of the ferrite tile, the size thereof is equal to or smaller than the size of the tile in the direction of the magnetic field component and is continuously mounted in the direction of the electric field component. In addition, the size of the contact portion of the ferrite tile is at least 200 mm or more, and the discontinuous portion is 100 m.
m or less.

Are arranged continuously in the direction of the electric field component shown in FIG.
In the case of a configuration in which a gap is provided in the direction of the magnetic field component, concrete goes around the gap in the direction of the magnetic field component, so that the ferrite tile 1 can be prevented from dropping or shifting downward due to its weight. Than the case where the gap is opened in the component direction and the
The ferrite tile can be thinner.

Further, the ferrite tile 1 is formed into a rectangular shape even if it is not a conventionally used square.
The length of the incoming radio wave in the direction of the magnetic field component may be shorter than the direction of the electric field component, and conversely, the size of the incoming radio wave in the direction of the electric field component may be shorter than the direction of the magnetic field component.

As shown in FIG. 3, the reflector 6 is used as a reflector.
When the ferrite tile 1 is used, it is possible to use a stainless steel reinforcing bar or a reinforcing steel bar subjected to rustproofing and arrange the ferrite tile 1 in the vicinity of 15 mm or less. In particular, when obtaining good radio wave absorption characteristics in the UHF band, in order to maintain the function as a reflector, it is necessary to arrange the horizontal streaks 7 parallel to the electric field direction component at a pitch of 40 mm or less.

However, if the pitch of the horizontal streaks 7 is too small, the concrete does not go around, so the optimum is 30 to 35 mm. FIG. 3 shows that the ferrite tiles 1 are continuously arranged in the direction of the electric field. Further, in FIG. 3, the pitch of the vertical streak is displayed narrow, but it is preferably about 150 mm.

In a conventional dry method using a frame, for example, as shown in FIG. 8, a rectangular frame 20 has horizontal rails 22, 21 sandwiched between vertical rails 21, 21 in the direction of the magnetic field component. An intermediate rail 23 is disposed between the upper and lower rails 22. Since a plurality of ferrite tiles 1 are continuously placed between the upper and lower horizontal rails 22, the entire rectangular frame 20, especially the horizontal rail 22 is required to withstand its weight. Need to be strengthened.

However, according to the present invention, in the case where a gap is formed in the direction of the electric field component and a gap is formed in the direction of the magnetic field component, the lattice-shaped rectangular frame 10 is used as shown in FIG. It is possible to use a material capable of withstanding the load of only one ferrite tile 1 for the horizontal inner frame 12 and the vertical inner frame 13 with respect to the outer frame 11, and use a simple reinforcing material having relatively low strength. It is possible to In addition, there is an advantage that the ferrite tile 1 can be easily mounted on the rectangular frame 10 simply by putting it in the frame one by one. Reference numeral 5 in FIG. 4 denotes a reflecting foil body also serving as an adhesive layer.

As described above, the magnetic field gap in the direction of the magnetic field component of the ferrite tile is filled with concrete, a calcium silicate plate used for the frame, and the like. Easy to accumulate moisture in case. Concrete, in particular, contains some moisture in itself and takes a considerable number of years to dry completely.

When water accumulates in the magnetic field gap as described above, the dielectric constant increases, the radio wave absorption performance decreases, and the change in water content makes the absorption performance unstable. Therefore, as shown in FIG. 5, in the present invention, a non-conductive material 8 having no water absorption and a low dielectric constant, such as hard urethane or vinyl chloride, is provided in the magnetic field gap between the ferrite tiles 1 and 1 in the direction of the magnetic field component. By inserting a material or the like, it is possible to prevent the radio wave absorption performance from being reduced or changed due to moisture, and it is also possible to keep the magnetic field gap dimension accurate. It is also an effective method to form the horizontal inner frame 12 of the rectangular frame 10 shown in FIG. 4 from the above-mentioned non-conductive material.

In the radio wave absorbing wall of the present invention, a ferrite having any known composition can be used for the ferrite tile, and the ferrite can be appropriately selected according to the application, absorption characteristics, and the like.
Ni-Zn based, Ni-Cu-Zn
And Mg-Zn based ferrites.

As the building material in the present invention, an outer wall material such as concrete or mortar is used.
In order to be able to be used as a building material for an outer wall of a building, it is preferable to bury a structural metal aggregate such as a reinforcing bar, a wire mesh, and a metal plate. Furthermore, in addition to ordinary exterior wall materials such as concrete and mortar, non-conductive fiber reinforced concrete containing glass fiber, vinyl fiber, etc. is adopted to obtain a stronger radio wave absorption wall for high-rise buildings. Can be.

Further, the ferrite tile may be fixed to the building material with a wire, a fitting, an adhesive, or the like, or may be embedded in a groove prepared in advance in the building material. Further, in the radio wave absorbing wall of the present invention, the exterior material laminated on the surface of the ferrite tile may be a known exterior material such as a natural stone plate or a porcelain tile, and a fixing material is appropriately disposed between the two.

[0032]

Example 1 As a radio wave absorbing wall according to the present invention, Ni—Cu—Z having dimensions of 100 mm × 100 mm × 6 mm was formed on a ferrite tile.
An n-type sintered ferrite is used and placed in a building material made of concrete in which a reinforcing bar is buried with a spacing of 25 mm in the direction of the electric field component of incoming radio waves and 70 mm in the direction of the magnetic field component. A tile having a thickness of 23 mm was used. As the reflector according to the present invention, a stainless steel rebar having a close contact with a ferrite tile was used, and the pitch of the horizontal rebar was 35 mm and the pitch of the vertical rebar was 150 mm.

FIG. 6 shows the results of measuring the radio wave absorption characteristics of the radio wave absorption wall according to the present invention. The peak value of the return loss plotted with black circles is at 620 MHz, which is -25 dB.

Embodiment 2 As a radio wave absorbing wall according to the present invention, a Ni—Cu—Z having a size of 100 mm × 100 mm × 6 mm was formed on a ferrite tile.
In an architectural material made of concrete using an n-type sintered ferrite and having a structural reinforcing bar buried therein, a continuous wave of 1000 mm in the direction of the electric field component of the arriving radio wave and 5 mm in the direction of the magnetic field component.
They were arranged at intervals of 0 mm, and a 23 mm thick porcelain tile or the like was used as the exterior material. The reflector used was one in which an Al foil was closely attached to a ferrite tile.

As shown in FIG. 7, the result of measuring the radio wave absorption characteristics of the radio wave absorbing wall according to the present invention shows a peak of the return loss at 600 MHz, and the value is -30 dB or less.

[0036]

According to the present invention, a sintered ferrite tile is used, and a radio wave absorbing wall having excellent weather resistance, workability, and strength equivalent to the conventional one can be obtained. When a plate or foil of a conductive material such as aluminum having corrosion resistance is continuously arranged and attached to the back surface of the tile, the workability is excellent, and the peak value of the return loss is 470 to 770M.
Hz, and a radio wave absorbing wall having a characteristic of -15 dB or less can be obtained. In addition, using a stainless steel reinforcing bar or a reinforcing steel bar subjected to rustproofing, the ferrite tile 1 is arranged within 15 mm or less, and the electric field direction component and The pitch of the parallel horizontal streak 7 is 4
When arranged at 0 mm or less, good radio wave absorption characteristics can be obtained particularly in the UHF band.

The radio wave absorbing wall according to the present invention can realize a dry method more efficiently by using a grid-like frame by utilizing the space in the direction of the magnetic field component, or a non-conductive material having no water absorption in the space. Can be arranged to stabilize the radio wave absorption characteristics.

[Brief description of the drawings]

FIGS. 1A and 1B are an explanatory perspective view and a sectional view showing an embodiment of a radio wave absorbing wall according to the present invention.

FIG. 2 is a perspective explanatory view of a ferrite tile showing details of a reflection foil body of FIG. 1;

FIGS. 3A and 3B are a perspective explanatory view and a sectional view showing another embodiment of the radio wave absorbing wall according to the present invention.

FIGS. 4A and 4B are a front explanatory view and a sectional view showing another embodiment of the radio wave absorbing wall according to the present invention.

FIG. 5 is an explanatory front view showing another embodiment of the radio wave absorbing wall according to the present invention.

FIG. 6 is a graph showing a relationship between frequency and return loss.

FIG. 7 is a graph showing a relationship between frequency and return loss.

8A and 8B are a front explanatory view and a cross-sectional view showing another example of the configuration of a conventional radio wave absorbing wall.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ferrite tile 2 Exterior material 3 Structural reinforcing bar 4 Concrete 5 Reflective foil 6 Reflecting bar 7 Horizontal bar 8 Non-conductive material 10, 20 Rectangular frame 11 Outer frame 12 Horizontal inner frame 13 Vertical inner frame 21 Vertical beam 22 Horizontal beam 23 Middle beam

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tsutomu Nishiwaki 2-15-17 Egawa, Shimamoto-cho, Mishima-gun, Osaka Sumitomo Special Metals Co., Ltd. Yamazaki Works (72) Inventor Yoshihiro Imai Egawa, Shimamoto-cho, Mishima-gun, Osaka 2-15-15 Sumitomo Special Metals Co., Ltd. Yamazaki Works

Claims (6)

[Claims] In a radio wave absorbing wall in which a number of magnetic materials made of sintered ferrite tiles are arranged in a building material and a reflector is arranged on the indoor side, the distance between the ferrite tile and the reflector is 15 mm or less. Radio wave absorption wall. 2. The radio wave absorbing wall according to claim 1, wherein the reflector is a reflection streak or a foil made of a corrosion resistant material. 3. The radio wave absorbing wall according to claim 1, wherein the corrosion-resistant foil material is substantially continuous in the direction of the electric field component of the incoming radio wave. 4. The radio wave absorbing wall according to claim 1, wherein the streaks parallel to the electric field component direction of the reflecting streaks are arranged at a pitch of 40 mm or less. 5. The UHF band radio wave absorption characteristic according to claim 1, wherein a support member for supporting the weight of each tile is provided at least between the sintered ferrite tiles in the direction of the magnetic field component of the arriving radio wave. Radio wave absorbing wall. 6. An excellent radio wave absorption characteristic in the UHF band according to claim 5 or 6, wherein a non-conductive material having no water absorption is arranged in a gap between the sintered ferrite tiles in a magnetic field component direction of an incoming radio wave. Radio wave absorbing wall.