Electromagnetic wave shield that selectively transmits specific electromagnetic waves

Abstract

To provide electromagnetic wave shielding means for shielding electromagnetic waves of a specific frequency.SOLUTION: In an electromagnetic wave shield, a receiving antenna is provided on one side of an electromagnetic wave shielding body having a symmetrical surface, and a transmitting antenna is provided on the other side, and both antennas are electrically connected, and electromagnetic waves of frequencies that can be received by the receiving antenna and emitted by the transmitting antenna among the bands shielded by the electromagnetic wave shielding body are selectively transmitted.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an electromagnetic wave shielding means. More specifically, the present invention relates to a means for selectively transmitting electromagnetic waves of a specific frequency in an electromagnetic wave shielding body that can originally shield electromagnetic waves in a wide frequency band.

Background Art

[0002] In recent years, the use of electromagnetic waves in various aspects as an information communication medium has been advancing, for example, in the automotive field, information communication field, etc. When using such electromagnetic waves, it is important to eliminate unnecessary electromagnetic waves that cause noise from the viewpoints of preventing misrecognition and improving sensitivity, and various electromagnetic wave shielding bodies that absorb or reflect electromagnetic waves for shielding are provided.

Disclosure of the Invention

Problems to be Solved by the Invention

[0003] Generally, the frequency band of electromagnetic waves that an electromagnetic wave shielding body can shield is continuous and wide. However, in some cases, it is recognized that it is technically necessary to selectively transmit electromagnetic waves of a specific frequency through the electromagnetic wave shielding body.

Means for Solving the Problems

[0004] As a result of investigations to solve the above problems, the present inventor has found that by incorporating the function of an antenna that receives and transmits electromagnetic waves of a specific frequency into an electromagnetic wave shielding body, even if the frequency band of the electromagnetic waves to be shielded is continuous and wide, electromagnetic waves of a desired frequency can be freely selected and transmitted through the electromagnetic wave shielding body, and thus the present invention has been completed.

[0005] That is, the present invention provides an electromagnetic wave shield that selectively transmits electromagnetic waves of frequencies that can be received by a receiving antenna and transmitted by a transmitting antenna among the bands shielded by the electromagnetic wave shield, characterized in that a receiving antenna is provided on one side surface of an electromagnetic wave shield having a symmetry plane, a transmitting antenna is provided on the other side surface, and the two antennas are electrically connected. (Hereinafter, also referred to as the electromagnetic wave shield of the present invention).

[0006] "Shielding of electromagnetic waves" means blocking or suppressing electromagnetic waves to which one is exposed by absorption or reflection.

[0007] The "electromagnetic wave shield having a symmetry plane" is an electromagnetic wave shield (hereinafter, also referred to as a base shield) that is the basis of the electromagnetic wave shield of the present invention. "Having a symmetry plane" means a shape having surfaces that are three-dimensionally opposed to each other on its surface. As long as this condition is satisfied, the shape, material, structure, type, etc. of the base shield are not limited, but the shape is preferably flat plate-like or sheet-like. In that case, the front and back surfaces of the flat plate or sheet correspond to the "symmetry plane". The overall shapes of the receiving antenna and the transmitting antenna can be selected according to the shape of the base shield, but are preferably flat plate-like or sheet-like. A flat plate is literally a "flat plate" and is incorporated as a definition regardless of flexibility, strength or presence / absence of rigidity. A sheet is something that is thin and spread out and is incorporated as a definition regardless of the presence / absence of flexibility.

[0008] Therefore, one of the preferred embodiments of the electromagnetic wave blocker of the present invention is that a receiving antenna having an overall flat plate-like or sheet-like shape is laminated and fixed on one of the flat plate surface or the sheet surface of a flat plate-like or sheet-like electromagnetic wave shield, and a transmitting antenna having an overall flat plate-like or sheet-like shape is laminated and fixed on the other, and the two antennas have substantially the same electrical characteristics and are electrically connected to each other, which is an electromagnetic wave shield.

[0009] The types of the receiving antenna and the transmitting antenna are not particularly limited. However, in the case of a flat plate antenna or a sheet antenna, a form in which a linear antenna is incorporated in the flat plate or the sheet surface is preferable. The receiving antenna and the transmitting antenna are electrically connected. By adjusting the pattern formed by the linear antenna, the thickness (width) of the wire itself, the width between the wires, etc., the frequency of the electromagnetic wave to be received and transmitted can be adjusted. The frequency of the electromagnetic wave to be received and transmitted needs to be included in the frequency band of the electromagnetic wave that the base shielding body can shield.

[0010] In the electromagnetic wave shielding body of the present invention, among the exposed electromagnetic waves, among the electromagnetic waves in the frequency band that the base shielding body can originally shield, Symmetry the electromagnetic wave (hereinafter also referred to as a specific electromagnetic wave) having a frequency received by the receiving antenna provided on one surface (electromagnetic wave exposure side) of the base shielding body and transmitted from the transmitting antenna on the other surface (electromagnetic wave blocking or suppressing side) passes through the electromagnetic wave shielding body via the antenna mechanism, and among the electromagnetic waves in the band that can be shielded as the physical properties of the base shielding body, only the specific electromagnetic wave can be positively transmitted.

[0011] The present invention has an aspect of a method for transmitting an electromagnetic wave using the electromagnetic wave shielding body of the present invention. That is, the present invention provides a method for transmitting an electromagnetic wave (hereinafter also referred to as the electromagnetic wave transmission method of the present invention) in which a receiving antenna is provided on one side surface of an electromagnetic wave shielding body having a symmetry plane, a transmitting antenna is provided on the other side surface, and the above two antennas are electrically connected, so that among the bands shielded by the above electromagnetic wave shielding body, an electromagnetic wave having a frequency that can be received by the receiving antenna and transmitted by the transmitting antenna is selectively transmitted through the electromagnetic wave shielding body.

Advantages of the Invention

[0012] According to the present invention, there is provided an electromagnetic wave shielding body that transmits an electromagnetic wave having a specific frequency among the bands of electromagnetic waves that the base electromagnetic wave shielding body can block. Further, a method for transmitting a specific frequency from the band of electromagnetic waves that the electromagnetic wave shielding body originally has and can shield is provided.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0014] Hereinafter, the present invention will be described with reference to the drawings.

[0015] FIG. 1 is a drawing showing an embodiment of the electromagnetic wave shield of the present invention. FIG. 1(1) is a schematic longitudinal sectional view of the electromagnetic wave shield 10 of the present invention viewed from the side in the thickness direction. The electromagnetic wave shield 10 has a flat or sheet-like receiving antenna 12 laminated and fixed on one plane of a sheet-like or flat base shield 11, and a flat or sheet-like transmitting antenna 13 laminated and fixed on the other plane. The receiving antenna 12 and the transmitting antenna 13 are electrically connected via a connection point 12-13. FIG. 1(2) is a plan view of the receiving antenna 12 viewed from the direction of arrow A. In the figure, a and b indicate the longitudinal and lateral sizes of the plane (horizontal am, vertical bm). Since the transmitting antenna 13 is substantially the same as the receiving antenna 12, its illustration is omitted. The receiving antenna 12 is composed of an insulating film 121 and a linear antenna 122. The linear antenna 122 is fixed and provided on the plane of the insulating film 121, and spirals inward in a square spiral shape from the starting end 1221 to the ending end 1222. Also, the starting end 1221 is electrically connected to the starting end of a square spiral-shaped linear antenna provided in the same manner in a transmitting antenna 13 (not shown) provided on the surface of the electromagnetic wave shield 10 of the present invention on the opposite side.

[0016] The base shield 11 can be freely selected from those having a band of a desired shielding frequency. The material of the insulating film 121 is not particularly limited as long as it has insulating properties, but a material suitable for pattern printing of the linear antenna 122 is preferred. Examples include polyethylene terephthalate (PET), polypropylene, fluororesin, polyester, polyimide, polyethylene naphthalate, etc., but are not limited thereto. The material of the linear antenna 122 is a conductive material, and examples include conductive metals such as gold, silver, copper, and aluminum, or alloys thereof, and conductive polymers. A paste-like conductive material can be made into a linear antenna portion of a desired shape by means such as printing.

[0017] The electromagnetic waves radiated in the direction of arrow A are shielded in the shielding frequency band by the electromagnetic wave shielding ability inherent in the base shield 11, and the transmission in the direction of arrow B is blocked or suppressed. On the other hand, the electromagnetic waves with frequencies that can be received by the receiving antenna 12 and transmitted by the transmitting antenna 13 pass through the electromagnetic wave shield 10 via the antenna mechanism and are selectively radiated in the direction of arrow B. The wavelength of the transmitted electromagnetic waves can be set and selected according to the material, thickness (width), width c between lines, etc. of the linear antenna 122. The frequency of the transmitted electromagnetic waves needs to be included in the frequency range of the shielding frequency band inherent in the base shield 11.

Example

[0018] Hereinafter, examples of the present invention will be disclosed.

[0019] [Manufacturing Example] Manufacturing of the Electromagnetic Wave Shield of the Present Invention The electromagnetic wave shield 10 of the present invention described in FIG. 1 was specifically manufactured. As the base shield 11, Dotite XO-9021 (manufactured by Fujikura Kasei Co., Ltd.), which is a magnetic shielding paint, was formed into a sheet and used. Dotite XO-9021 has been recognized to have an excellent electromagnetic wave blocking effect in a wide band (0.1 - 1000 MHz). The sheet thickness of the base shield was 500 μm, and the longitudinal and transverse lengths were both 150 mm. In addition, for the above sheet thickness (500 μm), when 100-μm-thick Dotite XO-9021 was stacked and the electromagnetic shielding effect for each 100 μm from 100 μm to 500 μm was examined by the KEC method, 500 μm thickness had the highest shielding effect, so this sheet thickness was adopted. FIG. 2(1) shows the results of examining the electromagnetic shielding effect [dB] between 0.1 - 1000 MHz for each of the above film thicknesses, and FIG. 2(2) extracts and shows the results for 500 μm thickness from among them. Basically, it was confirmed that transmission at a specific frequency was not recognized in the above band.

[0020] The insulating sheet forming the receiving antenna 12 and the transmitting antenna 13 used a PET film for pattern printing with a vertical dimension of 150 mm and a horizontal dimension of 300 mm. According to the design of the square helix of the linear antenna 122 in FIG. 1, pattern printing was performed using an Ag paste (type FA-323 for flexible substrates). In this pattern printing, a linear antenna portion with a desired square helix structure was provided on the PET film with the same square helix structure at two positions symmetric with respect to a line (folding line) that vertically cuts the midpoint in the horizontal direction (length direction) of the insulating sheet, and a connecting line was provided such that the starting points of these square helix structures were electrically conductive. FIGS. 3(3), 4(3), and 5(3) show the state where the above two square helix structures and these electrical connection lines are printed on the PET film. It was used as the receiving antenna and the transmitting antenna for the examples. The line width of the linear antenna drawn on the PET film with the Ag paste was 2 mm, and the distance between adjacent lines forming the helix was 3 mm. Three types of antenna pattern sizes (antenna lengths) were prepared: (1) small pattern: 413 mm (assumed frequency 726 MHz), (2) medium pattern: 1000 mm (assumed frequency 300 MHz), (3) large pattern: 1770 mm (assumed frequency 169 MHz). The resistance value between the innermost end of the receiving antenna (the innermost end of the helix) and the innermost end of the transmitting antenna was: (1) small pattern: 10 Ω, (2) medium pattern: 15 Ω, (3) large pattern: 35 Ω.

[0021] The PET film was folded along the above folding line and attached to the front and back surfaces of the sheet-shaped base shield prepared as described above so that sheet-shaped antennas with the same antenna pattern were positioned, and an electromagnetic wave shield of the present invention for testing was produced. Two types of attachment methods were prepared: "front-facing", where the antenna pattern was exposed on the front side of the electromagnetic wave shield, and "back-facing", where the insulating sheet side was on the front side of the electromagnetic wave shield, that is, the antenna pattern was not exposed with the insulating sheet intervening.

[0022] [Example] Examination of the transmission effect of electromagnetic waves at specific frequencies in small, medium, and large patterns (1) Small pattern Figure 3 shows the results of examining the electromagnetic wave shielding effects of the "front side" (Figure 3(1)) and "back side" (Figure 3(2)) in a test product according to the configuration of the small pattern (Figure 3(3)) in accordance with the KEC method. As a result, it became clear that the shielding effect of electromagnetic waves at the assumed transmission frequency dropped specifically. The transmission frequency shifted to the lower wavelength side for the front side compared to the back side.

[0023] (2) Medium pattern Figure 4 shows the results of examining the electromagnetic wave shielding effects of the "front side" (Figure 4(1)) and "back side" (Figure 4(2)) in a test product according to the configuration of the medium pattern (Figure 4(3)) in accordance with the KEC method. As a result, it became clear that the shielding effect of electromagnetic waves at the assumed transmission frequency dropped specifically. The transmission frequency shifted to the lower wavelength side for the front side compared to the back side.

[0024] (3) Large pattern Figure 5 shows the results of examining the electromagnetic wave shielding effects of the "front side" (Figure 5(1)) and "back side" (Figure 5(2)) in a test product according to the configuration of the large pattern (Figure 5(3)) in accordance with the KEC method. As a result, it became clear that the shielding effect of electromagnetic waves at the assumed transmission frequency dropped specifically. The transmission frequency shifted to the lower wavelength side for the front side compared to the back side.

Explanation of symbols

[0025] 10: Electromagnetic wave shielding body of the present invention 11: Base shielding body 12: Receiving antenna 121: Insulating film 122: Linear antenna 1221: Starting end of the linear antenna 1222: Ending end of the linear antenna 13: Transmitting antenna 12 - 13: Connection point between the receiving antenna and the transmitting antenna A: Arrow from the electromagnetic wave exposure side B: Arrow in the electromagnetic wave transmission direction a: Width and length of the receiving antenna 12 b: Width and length of the transmitting antenna 13 c: Width between lines

Claims

1. A receiving antenna, which is a linear antenna incorporated in an insulating film having an overall flat or sheet-like shape, is provided on one side surface of an electromagnetic wave shield having a symmetry plane, and a transmitting antenna, which is a linear antenna incorporated in an insulating film having an overall flat or sheet-like shape, is provided on the other side surface, and the receiving antenna and the transmitting antenna are electrically connected. An electromagnetic wave shield that selectively transmits electromagnetic waves having frequencies that can be received by the receiving antenna and transmitted by the transmitting antenna within the band shielded by the electromagnetic wave shield.

2. The electromagnetic wave shield according to claim 1, wherein the shape of the electromagnetic wave shield having the symmetry plane is flat or sheet-like.

3. A receiving antenna, which is a linear antenna incorporated in an insulating film having an overall flat or sheet-like shape, is laminated and fixed on one of the flat surfaces or sheet surfaces of a flat or sheet-like electromagnetic wave shield, and a transmitting antenna, which is a linear antenna incorporated in an insulating film having an overall flat or sheet-like shape, is laminated and fixed on the other. The receiving antenna and the transmitting antenna have the same electrical characteristics and are electrically connected to each other. An electromagnetic wave shield.

4. A receiving antenna, which is a linear antenna incorporated in an insulating film having an overall flat or sheet-like shape, is provided on one side surface of an electromagnetic wave shield having a symmetry plane, and a transmitting antenna, which is a linear antenna incorporated in an insulating film having an overall flat or sheet-like shape, is provided on the other side surface. By electrically connecting the receiving antenna and the transmitting antenna, electromagnetic waves having frequencies that can be received by the receiving antenna and transmitted by the transmitting antenna within the band shielded by the electromagnetic wave shield are selectively transmitted through the electromagnetic wave shield. A method for transmitting electromagnetic waves.

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