JPH11330770A - Electronic wave absorption wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of ferrite being used and to improve the performance for absorbing electronic waves in MHz-GHz band by specifying the gap rate between the electric field of arrival electronic waves and a ferrite magnetic material in the direction of a magnetic field for an electronic wave absorption wall in a wall with reinforced concrete and exterior finish materials. SOLUTION: A ferrite plate 1 is arranged at an equal interval of (c) in the direction of a magnetic field and is arranged at equal intervals of (a) in the direction of an electric field. A gap rate is the total ratio of the interval of the ferrite plate 1 in a predetermined range, where the ferrite plate 1 of a wall is arranged and is calculated from (interval/interval + ferrite plate)×100 for an arrangement at equal intervals. A gap rate c/d in the direction of a magnetic field is set to 20-50% and a gap rate a/b in the direction of an electric field is set to 25-45%. Even if the size of the ferrite plate 1 is adjusted appropriately and the interval is increased, sufficient reflection loss can be obtained in a UHF (300 MHz-3 GHz) band, thus reducing the amount of usage of the ferrite plate and reducing the weight of an electronic wave absorption wall.

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 which is applied to an outer wall of a high-rise building or the like and which prevents unnecessary reflected waves of an incoming television wave, and more particularly to a radio wave absorbing wall for a UHF band. It is.

[0002]

2. Description of the Related Art In recent years, unnecessary reflected radio waves from high-rise buildings have become obstacles to television broadcasting, and there has been a problem of radio wave pollution such as producing ghosts on television screens. As a countermeasure, there is a method of embedding a radio wave absorber in the outer wall of a high-rise building, and various radio wave absorption walls in which a magnetic material such as ferrite is embedded have been proposed.

FIG. 7 shows an example of a conventional radio wave absorbing wall. The radio wave absorption wall has an exterior material 51 disposed on the front surface, a ferrite plate 52 disposed on the rear surface thereof, and a concrete 54 together with a reinforcing bar 53. This radio wave absorption wall
It is manufactured as a unit by the PC method and mounted on a wall to form a wall of a high-rise building or the like. In the conventional radio wave absorption wall, the ferrite plate 52 is arranged in a direction (vertical direction) of a magnetic field component of an incoming radio wave.
In the direction of the electric field component of incoming radio waves (horizontal direction).

[0004]

In the conventional radio wave absorbing wall, since the ferrite plate is continuously arranged in the direction of the magnetic field component, there is a problem that the ratio of the ferrite plate in the wall is high and the weight of the wall is heavy. Was. In addition, since the ferrite plate is placed between the exterior material and concrete and its area is large, the adhesion strength of the exterior material is weak, and additional parts such as metal fittings for firmly fixing the exterior material are required, and the man-hour is also increased. There was such a problem. In addition, the conventional radio wave absorption wall is VHF
In many cases, it is designed to cope with radio waves in the band, and there is a problem that the radio wave absorption performance in the UHF band is insufficient.
Also, conventional radio wave absorption walls are designed mainly on the assumption that radio waves are incident perpendicular to the wall, and the problem is that the radio wave absorption performance for radio waves incident obliquely on the wall is insufficient. was there.

[0005] In view of the above, the present invention is to reduce the amount of ferrite plate used and to reduce the weight of the wall, or to reduce the amount of ferrite plate used and improve the adhesion strength of the exterior material. It is an object of the present invention to improve the radio wave absorption performance in the UHF band, or to improve the radio wave absorption characteristics for obliquely incident radio waves.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a radio wave absorbing wall in which a ferrite magnetic material is disposed inside a wall having a reinforced concrete forming the skeleton of the outer wall and an exterior material forming the outer wall. The radio wave absorbing wall has a gap ratio of the ferrite magnetic material in the electric field direction of the incoming radio wave of 25 to 45% and a gap ratio in the magnetic field direction of 20 to 50%. The present invention can obtain good radio wave absorption characteristics particularly in the UHF band.

The present invention also provides the ferrite magnetic material,
5 ≦ μ ′ ≦ 20, 10 ≦ μ ″ ≦ 25 (at 600MH
z) A radio wave absorbing wall characterized by the following.

Further, the present invention is the radio wave absorbing wall, wherein the thickness (width in the thickness direction of the wall) of the ferrite magnetic material is 2 to 6 mm. Preferred is 3-5 mm. In the present invention, the distance from the surface of the exterior material to the ferrite magnetic material is preferably 15 to 35 mm. If it is outside this range, it becomes difficult to obtain the radio wave absorption characteristics in the UHF band.

Further, the present invention is the radio wave absorbing wall, wherein a dielectric having a dielectric constant of 5 or less is arranged in a gap portion of the ferrite magnetic material in the direction of the electric field and / or the direction of the magnetic field. As a dielectric having a dielectric constant of 5 or less, for example,
Urethane foam or the like can be used. Further, the gap portion of the ferrite magnetic material can be arranged in the magnetic field direction, the electric field direction, or both directions.

[0010]

According to the present invention, the gap ratio of the ferrite magnetic substance in the direction of the electric field of an incoming radio wave is 25 to 45%,
The gap ratio in the magnetic field direction is set to 20 to 50%. This gap ratio is a ratio of the sum of the intervals of the ferrite plates in a predetermined range in which the ferrite plates of the wall are arranged, and when arranged at equal intervals, (gap / (interval +
(Ferrite plate) x 100).

FIG. 1 shows an arrangement structure of a ferrite plate according to an embodiment of the present invention. FIG. 1 shows the arrangement of the ferrite plates, and does not show exterior materials, concrete, reflectors, and the like. Exterior materials, concrete, reflectors, etc.
It can be designed appropriately. In this embodiment, the ferrite plates are arranged at regular intervals with an interval c in the direction of the magnetic field, and are arranged at regular intervals with an interval a in the direction of the electric field. In this embodiment, the gap ratio in the magnetic field direction (c / d × 100)
Is 35% and the gap ratio in the electric field direction (a / b × 100)
Is set to 40%. The shape of the ferrite plate 1 is 100 mm × 100 mm × 5 mm (thickness),
At 600 MHz, μ ′ = 11 and μ ″ = 18. The return loss characteristics of this embodiment are shown in FIG. 2. 35% of FIG. 2 indicates the return loss characteristics of this embodiment. This reflection loss is caused by the fact that the angle of incidence of the radio wave is 45 degrees with respect to the wall surface.
This is the characteristic when the light is obliquely incident at an angle of degrees.

FIG. 2 shows the return loss characteristics when the gap ratio in the magnetic field direction is changed in the above embodiment. Each gap ratio is shown in the figure. In this embodiment, only the gap ratio in the magnetic field direction is changed, and other conditions are the same. In this case, the UHF band (470M
Hz to 770 MHz), the gap ratio in the magnetic field direction is 25% to 45%. However, by changing other configurations, the gap ratio in the direction of the magnetic field becomes 20 to 50.
% In the UHF band (470 MHz to 770 MHz)
When the incident angle of the radio wave was 25 to 65 degrees, appropriate radio wave absorption characteristics were obtained.

In the present invention, the gap ratio in the direction of the electric field is suitably from 25 to 45%. Otherwise, the reflection loss is reduced. The characteristics of the ferrite plate are 5
≦ μ ′ ≦ 20, 10 ≦ μ ″ ≦ 25 (at 600 MHz)
In other cases, the reflection loss is reduced. The size of the ferrite plate is 30 mm × 30
mm or more, the thickness is preferably 2 to 6 mm,
Otherwise, the return loss decreases.

FIG. 3 shows a layout structure of a ferrite plate according to another embodiment of the present invention. In this embodiment, a gap material 2 is interposed in a gap portion of a ferrite plate 1 in a magnetic field direction. Thereby, it becomes easy to arrange the ferrite plates 1 at intervals. As the gap material 2, urethane foam (dielectric constant: 1.3) was used. Preferably, the gap material has a dielectric constant of 5 or less.
More preferably, the dielectric constant is 3 or less. As the gap material, urethane foam, styrene foam, or the like can be used, and urethane foam is particularly preferable. By inserting the gap material having a dielectric constant of 5 or less between the ferrite plates, the amount of concrete entering between the ferrite plates is limited, the radio wave absorption characteristics are improved, and it is particularly effective for improving the radio wave absorption characteristics in the UHF band. .

FIGS. 4 and 5 show the arrangement of ferrite plates according to another embodiment of the present invention. In the embodiment shown in FIG. 4, a gap member 2 is interposed in a gap portion of the ferrite plate 1 in the electric field direction. As a gap material,
As described above. In the embodiment shown in FIG. 5, the gap material 2 is interposed in the gap portion of the ferrite plate 1 in the magnetic field direction, and the gap material 2 is further provided in the gap portion in the electric field direction.
Is interposed. This gap material 2 is also as described above.

FIG. 6 shows an arrangement of a ferrite plate according to another embodiment of the present invention. The embodiment shown in FIG.
A gap material 2 is interposed in a gap portion of a ferrite plate 1 in a magnetic field direction. The gap material is as described above. Further, the width of the gap material 2 is formed smaller than the width of the ferrite plate 1. Thereby, when the concrete is cast, the concrete enters and has an effect of preventing the ferrite plate or the like from falling off. A similar effect can be obtained by making the thickness of the gap material smaller than the thickness of the ferrite plate.

According to the present invention, a sufficient reflection loss can be obtained in the UHF band even if the gap ratio in the magnetic field direction is increased to 20 to 50% and the interval between the ferrite plates is increased. In this case, the gap ratio in the electric field direction is 25 to 45%,
The characteristics of the ferrite plate are as follows: 5 ≦ μ ′ ≦ 20, 10 ≦ μ ″ ≦
25 (at 600 MHz), the size of the ferrite plate is
It is 30 mm x 30 mm or more, and the thickness is appropriately adjusted under the conditions of 2 to 6 mm. The incident angle of the radio wave is 25 to 6
At 5 degrees, the desired return loss was obtained. As a result, the amount of the ferrite plate used can be reduced, and the weight of the radio wave absorption wall can be reduced. Further, the amount of the ferrite plate used can be reduced, and the adhesion strength of the exterior material can be improved.

[0018]

According to the present invention, the ferrite magnetic material conventionally arranged continuously in the direction of the magnetic field component can be reduced by 20 to 50%.
Even if they are arranged with a large gap ratio, it is possible to provide a radio wave absorbing wall capable of obtaining a sufficient reflection loss. Also,
In the UHF band, a sufficient reflection loss can be obtained. In addition, a sufficient reflection loss can be obtained for a radio wave that is obliquely incident on the radio wave absorption wall. In addition, it is possible to reduce the weight of the radio wave absorption wall and improve the adhesion strength of the exterior material.

[Brief description of the drawings]

FIG. 1 is a view showing a method for arranging ferrite plates according to one embodiment of the present invention.

FIG. 2 is a diagram showing a return loss characteristic of an example according to the present invention.

FIG. 3 is a view showing a method for arranging ferrite plates according to another embodiment of the present invention.

FIG. 4 is a view showing a method of arranging ferrite plates according to another embodiment of the present invention.

FIG. 5 is a view showing a method for arranging ferrite plates according to another embodiment of the present invention.

FIG. 6 is a view showing a method for arranging ferrite plates according to another embodiment of the present invention.

FIG. 7 is a perspective view of a conventional example.

[Explanation of symbols]

 1 Ferrite plate 2 Gap material

Claims (4)

[Claims] An electromagnetic wave absorbing wall in which a ferrite magnetic material is disposed inside a wall having a reinforcing steel concrete forming a frame of an outer wall and an exterior material forming an outer wall. 25-45 body gap ratio
%, And the gap ratio in the magnetic field direction is 20 to 50%. 2. The ferrite magnetic material according to claim 1, wherein 5 ≦ μ ′ ≦ 2.
2. The radio wave absorbing wall according to claim 1, wherein 0, 10 ≦ μ ″ ≦ 25 (at 600 MHz). 3. The radio wave absorbing wall according to claim 1, wherein the thickness (width in the thickness direction of the wall) of the ferrite magnetic material is 2 to 6 mm. 4. The radio wave absorbing wall according to claim 1, wherein a dielectric having a dielectric constant of 5 or less is arranged in a gap portion of said ferrite magnetic body in said electric field direction and / or magnetic field direction.