JPH0635519Y2 - Radio wave absorption wall - Google Patents

Description

[Detailed Description of the Invention] [Industrial application] The present invention relates to an electromagnetic wave absorbing wall, and in particular, an electromagnetic wave absorber is attached to a part of the outer wall of a building or the like to prevent unnecessary reflected electric waves in the VHF and UHF bands. It relates to a radio wave absorption wall.

[Conventional technology]

Recently, unnecessary reflected radio waves from high-rise buildings have become an obstacle to television broadcasting, and radio wave pollution such as causing ghosts on television screens has become a problem. As a countermeasure against this, the use of electromagnetic wave absorption walls on the outer walls of high-rise buildings is increasing. As the electromagnetic wave absorbing wall, those described in JP-B-55-13600 and JP-B-55-49798 are known. This conventional example is shown in FIG. FIG. 2 (a) is a plan view showing the method of arranging the magnetic plates, and FIG. 2 (b) is a cross-sectional view of the electromagnetic wave absorbing wall. In this radio wave absorber, a ferrite plate 23 as a magnetic plate is fixed to the surface of a mortar 22 in which a metal plate 21 is embedded, and an exterior material 24 such as mortar is provided on the ferrite plate 23. The ferrite plate 23 is arranged continuously in the magnetic field direction L of the incoming radio wave and discontinuously in the electric field direction M.

[Problems to be solved by the device]

In the above conventional radio wave absorption wall, since the dielectric material such as mortar and stone is arranged in front of the ferrite, the absorption characteristics of the magnetic material are not sufficiently exhibited, and as shown by the curve 32 in FIG. However, there is a problem in that a satisfactory return loss cannot be obtained and the return loss is particularly small on the high frequency side. This mortar, stone material, etc. are used as exterior materials,
A thickness of 25 mm or more is required due to reliability such as mechanical strength, and it is generally used with a thickness of 30 mm.

Without this exterior material, the return loss characteristics would be the curves in Fig. 3.
As shown in 34, a sufficiently satisfactory return loss can be obtained in a wide frequency range, but this is not preferable because it impairs aesthetics.

Also, as a measure to increase the return loss on the high frequency side,
There is a means for providing a small gap between ferrite plates arranged continuously in the magnetic field direction and moving the return loss to the high frequency side. However, as shown by the curve 33 in FIG. 3, this means conversely reduces the return loss on the low frequency side.

There are other means such as thinning the ferrite or increasing the gap ratio in the electric field direction, but in either case, the return loss becomes small on the low frequency side.

As described above, when the exterior material is on the front surface of the ferrite, there is a problem that a high return loss cannot be obtained over a wide frequency range.

The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a radio wave absorption wall having a good return loss characteristic in a wide frequency range.

[Means for Solving the Problems]

As a result of earnest research to achieve the above-mentioned object, the inventors of the present invention have found that in a radio wave absorption wall having a plurality of magnetic bodies attached,
The magnetic body is discontinuously arranged in the direction of the electric field component of the incoming radio wave, and the magnetic body is composed of a plurality of continuous portions in the direction of the magnetic field component of the incoming radio wave, and the gap between the continuous portions is sufficiently larger than the length of the continuous portion. It was discovered that the return loss characteristic becomes good in a wide frequency range if the gap is formed so as to be concentrated in the magnetic field direction so that the present invention is conceived.

That is, the radio wave absorbing wall of the present invention is constructed by disposing a plurality of radio wave absorbing panels to which a plurality of magnetic substances are attached, and the magnetic substance in each of the radio wave absorbing panels is an electric field component of an incoming radio wave. Discontinuity in the direction, and in the direction of the magnetic field component of the incoming radio wave, it is arranged so as to have one or two or more gaps except the gaps existing at the upper and lower ends of the radio wave absorption panel, and the gap is 20 mm to 200 mm. And is sufficiently shorter than a continuous portion composed of a plurality of continuous magnetic bodies separated by the gap.
That is, it is characterized in that gaps are concentratedly formed in the direction of the electric field component.

[Action]

The non-reflective condition of the radio wave absorption wall is that the impedance of the radio wave absorption wall viewed from the direction of arrival of radio waves is matched with the impedance of free space (Zo = 337Ω).

The frequency characteristic of the real part of the impedance of the conventional radio wave absorption wall is illustrated by the curve 41 in FIG. 4, and the frequency characteristic of the imaginary part is illustrated by the curve 51 in FIG.

In a conventional electromagnetic wave absorption wall, the impedance approaches 100 to 120MHz, which is close to the impedance in free space, and the return loss increases, but it decreases at 200MHz.

The concentrated gap type electromagnetic wave absorbing wall according to the present invention further increases the amount of reflective attenuation at high frequencies while maintaining the reflective attenuation characteristics of the conventional electromagnetic wave absorbing wall.

In the lumped-gap type electromagnetic wave absorption wall of the present invention, the frequency characteristics of the real part and the imaginary part of the impedance around the central part of the continuous part of the magnetic body are respectively the curves 41 and 41 of FIG.
Corresponding to the curve 51 in FIG. 5, the frequency characteristics of the real part and the imaginary part of the impedance around the concentrated gap are illustrated by the curve 42 in FIG. 4 and the curve 52 in FIG. 5, respectively.

By combining the impedance of this continuous part and the gap part,
The real part and the imaginary part of the impedance of the radio wave absorption wall are shown by a broken line 43 in FIG. 4 and a broken line 53 in FIG. 5, respectively.

It is clear that in the frequency range of 150 MHz or less, while maintaining the characteristics of the conventional electromagnetic wave absorption wall, at high frequencies, the impedance of the conventional electromagnetic wave absorption wall approaches the impedance of free space and the return loss becomes higher. Especially 200MHz
It is remarkable in the vicinity.

The radio wave absorption wall in the present invention can change the impedance of the continuous portion and the impedance of the concentrated gap portion by making the continuous portion and the concentrated gap portion of the magnetic body in the direction of the magnetic field component of the incoming radio wave have arbitrary configurations. The impedance of the entire electromagnetic wave absorption wall can be controlled. Therefore, it is possible to control the reflection attenuation characteristic of the entire radio wave absorption wall, and obtain a radio wave absorption wall in a wide band.

〔Example〕

FIG. 1 is a plan view showing an arrangement of magnetic bodies according to an embodiment of the present invention. As shown in FIG. 1, a plurality of magnetic bodies are arranged in a plurality of rows so that gaps are evenly present in the magnetic field direction, and one or two magnetic bodies are arranged so that a concentrated gap method is also provided in the magnetic field direction. The above gap is provided.
From the viewpoint of construction, it is preferable to form a radio wave absorbing wall panel made of a predetermined number of magnetic materials and attach the panel to the outer wall of the building in a predetermined arrangement. In the embodiment of FIG. 1, it is preferable that the panel length A in the magnetic field direction is about 1 to 5 m and the panel length B in the electric field direction is about 0.5 to 5 m.

As a magnetic material attached to such a panel, molding,
From the viewpoint of ease of sintering and construction, each side is 30 to 200 mm
Something is preferable. This magnetic body is arranged on a plurality of panels. (1) The magnetic body is attached continuously except that one or more gaps are provided so that the magnetic field direction is a concentrated gap method. ) Regarding the electric field direction, it is necessary to arrange so that a gap exists between each magnetic body row (arrangement in the magnetic field direction).

Regarding the magnetic field direction, two gaps D, D are shown in FIG. 1, but the number of the gaps is not limited to that, and may be one or three or more. Further, the voids C, C existing at the upper and lower ends of the panel also form a gap when the panel is continuously attached to the outer wall,
It will be taken into consideration when calculating the gap ratio described later.

The size of each gap D needs to be sufficiently smaller than the length of the connecting portion of the magnetic body, but is about 20 to 200 mm, preferably 5 mm.
0 to 150 mm is suitable. If the gap D is less than 20 mm, absorption on the high frequency side becomes insufficient, and if it exceeds 200 mm,
The interaction between the continuations is weakened (ie, each continuum is as if it were isolated).

Further, since the number of gaps varies depending on the size of the gap, it is preferable to set the number of gaps to have a predetermined gap ratio. Here, the “gap ratio” refers to a value (expressed as a percentage) obtained by dividing the synthesis of the sizes of the gaps by the total length of the array of magnetic bodies including the gaps. In the case of FIG. 1, the gap ratio in the magnetic field direction can be expressed by (2D + 2C) / A × 100%. Further, the gap ratio in the electric field direction can be expressed by nE / B × 100% (however, n represents (column of magnetic material + 1)).

In the electromagnetic wave absorbing wall of the present invention, the gap ratio in the electric field direction varies depending on the thickness of the ferrite plate, etc., but is preferably 30 to 50%, and the gap ratio in the magnetic field direction is 1 to 10%, preferably 3 to. 8% is suitable.

If the gap ratio in the direction of the electric field is less than 30%, the electromagnetic wave absorption wall becomes heavy and expensive, and if it exceeds 50%, the required attenuation cannot be obtained, or the thickness of ferrite needs to be increased. It is inappropriate because it exists. Further, if the gap ratio in the magnetic field direction is less than 1%, no significant improvement can be obtained,
If it exceeds 10%, the return loss is insufficient, which is unsuitable.

In the embodiment shown in FIG. 1, the continuous portion F of the central ferrite plate 1 is 400 to 2,000 mm, and gaps D and D of 50 to 150 mm are formed above and below it, respectively, and further above and below it. Is preferably a continuous portion of the ferrite plate 1 of 1,000 to 2,000 mm.

The magnetic body may be formed of any material as long as it exhibits soft magnetic characteristics, but a ferrite plate is preferable from the viewpoint of characteristics and cost. This ferrite plate is Ni-
Zn ferrite, Ferroc planer type Ba ferrite,
It can be formed of soft ferrite such as Mn-Mg-Zn ferrite and Mn-Zn ferrite.

The present invention will be described in more detail by the following specific examples.

Example 1 A panel for outer wall (length A4m, width B3m20cm) shown in FIG.
A ferrite plate 1 of 100 mm, width 100 mm, and thickness 9 mm was used. In the lateral direction (electric field direction) of this panel,
The ferrite plates 1 are arranged with an interval E of 60 mm, and in the vertical direction (magnetic field direction), a gap C of 10 mm each is provided above and below.
Is formed, and the continuous portion F of the 800 mm ferrite plate 1 is formed in the center.
And the gaps D and D of 90mm above and below
Is formed, and there is a continuous portion of the ferrite plate 1 of 1,500 mm above and below. Note that FIG. 1 shows a small number of ferrite plates for simplification.

In this embodiment, the gap ratio in the electric field direction is 40% and the gap ratio in the magnetic field direction is 5%.

The return loss characteristic of this embodiment is shown by the curve 31 in FIG. As a conventional example, the reflection attenuation characteristic when there is no gap in the magnetic field direction is shown in the curve 33 of FIG.
A return loss characteristic when a gap in the magnetic field direction is provided for each sheet is shown by a curve 32 in FIG.

As shown in FIG. 3, the radio wave absorbing wall of the present invention has excellent return loss over a wide frequency range.

The radio wave absorption wall is required to have a large return loss for TV radio waves.
A return loss of 15 dB or more is required in the range of Hz to 200 MHz. From the data in FIG. 3, it can be seen that the electromagnetic wave absorbing wall of the present invention satisfies the target characteristics, but in the conventional example, the return loss at 100 MHz or 200 MHz is insufficient.

[Effect of device]

INDUSTRIAL APPLICABILITY The present invention is excellent in the reflection attenuation ability for TV radio waves in a wide frequency range, and when used as an outer wall of a building such as a high-rise building, it is effective in preventing unnecessary reflection radio waves such as ghost prevention of TV radio waves.

[Brief description of drawings]

FIG. 1 is a plan view showing an arrangement of magnetic bodies according to one embodiment of the present invention, FIG. 2 is a plan view (a) and a sectional view (b) of a conventional example, and FIG. FIG. 4 is a graph showing return loss characteristics of an example according to the present invention and a conventional example, and FIGS. 4 and 5 are graphs showing frequency characteristics of impedance and combined impedance of the present invention and the conventional example. 1,23 …… Magnetic material (ferrite plate) 21 …… Metal plate 22 …… Mortar 24 …… Exterior material

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Yoshiyuki Moriyama 33-12 Minamieicho, Tottori City, Tottori Prefecture Hitachi Ferrite Co., Ltd. Tottori Factory (72) Creator Yuji Matsumoto 550-1 Zenkeiji, Kanra-cho, Kanra-gun, Gunma Prefecture Hitachi Ferrite Co., Ltd. EMC Center (72) Inventor Kazuro Hanatani, 3-8 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. Tokyo Branch (72) Inventor, Jiji Toshi City, 2-2, Jinnan, Shibuya-ku, Tokyo No. 1 within the Japan Broadcasting Corporation Broadcasting Center (56) Reference JP-A-1-257398 (JP, A)

Claims (1)

[Scope of utility model registration request] 1. A radio wave absorbing wall configured by arranging a plurality of radio wave absorbing panels having a plurality of magnetic bodies attached, wherein the magnetic bodies in each of the radio wave absorbing panels are improper in the electric field component direction of an incoming radio wave. It is arranged continuously and in the direction of the magnetic field component of the incoming radio wave so as to have one or two or more gaps except for the voids existing at the upper and lower ends of the radio wave absorption panel, and the gap has a length of 20 mm to 200 mm. The electromagnetic wave absorption wall having a length that is sufficiently shorter than a continuous portion made of a plurality of continuous magnetic bodies separated by the gap.