JPH05267884A - Radiowave reflector and radiowave dark room - Google Patents

Abstract

PURPOSE:To make it possible to control a fine adjustment in accordance with various reflecting properties to the earth in the wide frequency range, by placing a magnetic layer on a metal plate and installing a laminated dielectric layer in which two materials having different dielectric constants are stacked alternately on the magnetic layer. CONSTITUTION:A radiowave reflector 10 comprises a conductor plate 1 made of a metal plate such as iron, a ferrite tile 2 made of a magnetic layer connected to the conductor plate 1, and a laminated structure dielectric 5 connected to the tile 2. The dielectric 5 is formed in a stacked structure in which an antistatic sheet 3 of rubber or vinyl type and a structural veneer plywood 4 are stacked alternately. The dielectric 5 is formed so that the antistatic sheet 3 is thicker and the veneer plywood 4 whose dielectric constant is close to that of air is thinner as they approach the surface of the reflector 10. The antistatic sheet 3 is set, to various values of dielectric constant by adjusting its material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio wave reflector, and more particularly to a radio wave reflector and an anechoic chamber having a reflection characteristic almost equal to that of the ground.

[0002]

2. Description of the Related Art Noise measurement of an automobile is carried out at an experimental field called a test site, which has a good radio environment. In this system, a receiving antenna is installed at a position 3 m above the ground 10 m away from the car, and noise power from the car is measured by this antenna. Since this measurement includes the reflection from the ground, a standard for the reflection characteristics of the ground at the test site is set in order to clarify the accuracy of noise measurement. That is, according to the JASO standard, as shown in FIG. 2, the receiving antenna 21 is installed at a position 3 m above the ground, which is 10 m away from the transmitting antenna 20 installed 1 m above the ground.
The site attenuation curve at the frequency of MHz is
It is said that it must be within ± 3db of the standard site attenuation curve.

When simulating such a test site in an anechoic chamber, it is necessary to construct the floor with a radio wave reflector whose reflection characteristic of the floor conforms to the above standards. A conventional example of such a radio wave reflector is, for example, Japanese Patent Publication No. 3-263.
There is one shown in No. 50. In the conventional example, the ferrite layer is provided on the conductor plate, and the resistance film layer is further provided on the ferrite layer. In all of these radio wave reflectors, desired reflection characteristics are realized by controlling the thickness of each layer. In addition, JP-A-58
In the radio wave absorber disclosed in No. -10902, a conductor plate is provided with a ferrite as the first layer and a dielectric is provided as the second layer on the conductor plate. Is the same as. Also, JP-A-57-102337
In the one shown in No. 1 and the like, only the dielectric is used in a single layer.

[0004]

Among the above-mentioned conventional techniques, in the case of the dielectric single layer disclosed in JP-A-57-102337, small pieces of the dielectric are filled to a thickness of 90 to 130 mm. However, since the electric constant changes depending on the packing density, great care must be taken to obtain the necessary reflection characteristics, which affects the construction. In addition, adjustment required a long period of time and there was room for improvement in terms of construction period. In addition, Japanese Patent Publication 3-263
In the multilayer structure shown in No. 50, a resistance film for impedance adjustment is arranged on a ferrite tile (5 mm thick). The ferrite thickness and the resistance film characteristics are adjusted so that the impedance seen from the resistance film is approximately equal to the ground impedance. With this technology, the impedance of the earth at a specific frequency
Although it is possible to make it almost equal to the dance, it is not easy to realize the desired characteristics only with the ferrite tile and the thin resistance film over a wide frequency range (30 to 1000 MHz). Further, the one disclosed in JP-A-58-10902 is a radio wave absorber, and the characteristics as a reflector are not taken into consideration.

An object of the present invention is to provide a radio wave reflector whose characteristics can be easily adjusted and desired reflection characteristics can be easily realized in a wide frequency range, and the reflection characteristics of the ground can be accurately approximated. It is to provide an anechoic chamber having a floor surface.

[0006]

The above-mentioned object is to provide a magnetic material layer arranged in layers on a metal plate, and two materials arranged in layers on the magnetic material layer and having different dielectric constants inside. Is provided by alternately arranging the laminated dielectric layers in layers, and by arranging the radio wave reflector thus constructed on the floor surface of the anechoic chamber.

[0007]

[Function] Since the laminated dielectric layer for controlling the phase of the reflected wave has a layered structure, and the dielectric constant of the entire laminated dielectric layer can be easily controlled only by changing the thickness of each material constituting the layer, the reflection characteristic is improved. It becomes easy to adjust over a wide frequency band, and the thickness of the reflector itself can be reduced. Moreover, since good characteristics can be obtained in a wide frequency band, the reflection characteristics of the ground can be well approximated.

[0008]

FIG. 1 shows an embodiment of the radio wave reflector according to the present invention. This figure is a cross-sectional view of a radio wave reflector 10, which includes a conductor plate 1, a ferrite tile 2 bonded to the conductor plate 1, and a laminated structure dielectric 5 bonded to the ferrite tile 2. The rubber or vinyl antistatic sheet 3 and the structural veneer plate 4 are laminated alternately. The conductor plate 1 serves as a radio wave shield, and iron is suitable. Ferrite is used as a magnetic core such as a coil and a radio wave absorber, and its complex permeability is a material that can be selected in a wide range. Therefore, various reflection characteristics can be realized by providing the ferrite tile 2 on the conductor plate 1 and adjusting the magnetic permeability and thickness thereof. The reason why the laminated dielectric 5 is provided on the ferrite tile 2 is that ferrite has higher impedance than the dielectric. Further, the reason why the dielectric 5 is laminated is that various electromagnetic reflection characteristics can be obtained depending on the layer structure (the number of layers, the thickness of each layer, the individual thickness of the sheet of each layer and the veneer plate). Thus, with various combinations of ferrite tiles and laminated dielectrics, electromagnetic wave reflection characteristics similar to those of the ground are obtained.

The dielectric 5 has a multi-layered structure as described above, and the closer to the surface of the reflector 10 is, the closer the antistatic sheet 3 becomes.
Is thin and the veneer plate 4 is thick, and as the ferrite tile 2 is approached, the antistatic sheet 3 is thicker and the veneer plate 4 is thinner. Veneer board 4
Has a dielectric constant close to that of air. On the other hand, the antistatic sheet 3 has a large dielectric constant, and its value can be set to various values by adjusting the material. Thus, when the distance from the ferrite tile 2 in the surface direction is x, the dielectric constant of the dielectric 5 gradually decreases as x increases, as shown in FIG.
Is illustrated in. Utilizing this characteristic, the contact surface with ferrite having a large permittivity (x = 0) has a dielectric constant substantially equal to that of the ferrite material, and the contact surface with air having a small permittivity (x = d) has the dielectric material 5. Since the permittivity of can be similarly reduced, the discontinuous change in permittivity can be reduced, and complex reflection can be reduced. This simplifies the adjustment of the reflection characteristics and helps achieve the desired reflection characteristics in a wide frequency range.

As an example, the real part of the complex relative permeability of the ferrite tile 2 which is a magnetic material for controlling the amplitude of the reflected wave is about 85 to 1, the imaginary part is about 170 to 6.5,
The real part of the relative permittivity is about 14, the imaginary part is about 1.0, and the thickness is about 8 mm, while the real part of the complex relative permittivity of the dielectric 5 for controlling the phase of the reflected wave is 30 to 30 mm. About 7,
If the imaginary part is about 60 to 3.0 and the thickness is about 15 to 30 mm, good reflection characteristics can be obtained in the 30 to 1000 MHz band. FIGS. 5 and 6 compare the actual measurement values of this embodiment with the ground reflection characteristics (site attenuation, that is, reception power / transmission power). Horizontal polarization (FIG. 5) and vertical polarization (FIG. 6). ) Both show good agreement in the 30 to 1000 MHz band. Here, in FIGS. 5 and 6, (a) is the actual measurement value in the present embodiment, and (b) is the actual measurement value in the ground.
And, in this embodiment, the thickness of the dielectric material is such that the maximum frequency used is 1000 MHz in free space (in vacuum) wavelength 3
It becomes 5 / 100-10 / 100 = 15-30 mm degree of 0 cm, and it can be seen that it can be realized with a much thinner thickness as compared with the prior art (Japanese Patent Laid-Open No. 63-25758).

FIG. 3 shows an embodiment of an anechoic chamber using the radio wave reflector of the present invention on the floor. This figure is a plan view that can be placed on the floor of an anechoic chamber, in which the radio wave reflector 10 of the present invention is spread over the floor of the anechoic chamber surrounded by the electromagnetic wave absorption band 12. Considering this as the ground, the measurement by the JASO measurement method shown in FIG. 2 can be performed in the anechoic chamber.

Incidentally, general wood or other materials may be used in place of the veneer plate, and rubber or vinyl type is used as the sheet, but other organic resin type may be used.

[0013]

According to the present invention, by using a laminated dielectric, the relative permittivity can be easily controlled from about 300 to about 10. Therefore, the amplitude and phase characteristics of the reflected wave and the reflection on the surface of the reflector can be easily controlled. The amplitude and phase characteristics of the electromagnetic wave transmitted into the body and the angle of incidence on the magnetic material can be easily controlled, and fine adjustment corresponding to the reflection characteristics of various grounds can be effectively performed over a wider frequency range than in the prior art.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a radio wave reflector of the present invention.

FIG. 2 is an explanatory diagram of JASO standard.

FIG. 3 is a diagram showing an embodiment of an anechoic chamber using the radio wave reflector of the present invention.

FIG. 4 is a diagram showing a change in a dielectric constant of a laminated dielectric band in a thickness direction.

FIG. 5 shows measured values of horizontal polarization characteristics of the radio wave reflector of the present invention and the ground.

FIG. 6 shows measured values of vertical polarization characteristics of the radio wave reflector of the present invention and the ground.

[Explanation of symbols]

 1 Conductor Plate 2 Magnetic Material (Ferrite Tile) 3 Rubber or Vinyl Antistatic Sheet 4 Structural Veneer Plate 5 Laminated Structure Dielectric 10 Radio Wave Reflector

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yaginuma Efficacy 3-2-1, Sachimachi, Hitachi City, Ibaraki Hitachi Engineering Co., Ltd. (72) Inventor Masahiro Tojo 4-6, Kanda Surugadai, Chiyoda-ku, Tokyo Hitachi, Ltd. (72) Inventor Shinji Shirakawa 1168 Moriyama-cho, Hitachi City, Ibaraki Pref., Energy Research Laboratory, Nitrate Works Co., Ltd. (72) Inventor Yasuaki Kinoshita 1-280, Higashi Koigakubo, Kokubunji, Tokyo Hitachi Central Research Institute In-house (72) Ryozo Tsuruoka 3-2-1, Saiwaicho, Hitachi, Ibaraki Hitachi Engineering Co., Ltd. (72) Inventor Shigeru Osawa 3-16-1 Shin-Yokohama, Kohoku-ku, Yokohama-shi, Kanagawa E & C Engineering Co., Ltd.

Claims (6)

[Claims] 1. A metal plate, a magnetic layer arranged in a layer on the metal plate, and a layer arranged on the magnetic layer in a layered manner. Two materials having different dielectric constants are alternately layered inside. A radio wave reflector comprising: a laminated dielectric layer that is disposed in the. 2. The radio wave reflector according to claim 1, wherein the magnetic layer is a ferrite tile. 3. The radio wave reflector according to claim 1, wherein one of the materials forming the laminated dielectric layer is a veneer plate and the other is a rubber or vinyl antistatic seal. 4. Of the two materials forming the laminated dielectric layer, the material having a larger dielectric constant has a larger thickness, and the material having a smaller dielectric constant has a larger thickness. 5. The radio wave reflector according to claim 1, wherein the thickness of the radio wave is made smaller as it is closer to the magnetic layer. 5. The radio wave reflector according to claim 4, wherein the laminated dielectric layer has a thickness of 5/100 to 10/100 of the shortest usable wavelength. 6. An anechoic chamber in which the radio wave reflector according to claim 1 or 2 or 3 or 4 or 5 is attached to a floor surface.