Electromagnetic wave shielding structure

Abstract

To provide an electromagnetic wave shielding structure (Faraday cage material) that is highly resistant to outdoor environments.SOLUTION: An electromagnetic wave shielding structure (100) includes a first member (110) made of a first material that is an electrical conductor, and a second member (120) made of a second material having a lower electrical conductivity than that of the first material and a higher corrosion resistance than that of the first material, where the second member (120) covers at least a portion of the surface of the first member (110).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electromagnetic wave shielding structure that blocks the passage of electromagnetic waves, and further to an electromagnetic wave shielding system that uses this electromagnetic wave shielding structure. This electromagnetic wave shielding structure is used as a material for a Faraday cage. [Background technology]

[0002] In recent years, many problems have arisen due to electromagnetic waves (external electromagnetic waves). For example, electromagnetic noise generated from various devices can cause electronic devices to malfunction. Considering the current international situation, the risk of EMP (Electromagnetic Pulse) attacks cannot be ignored. In many cases, an EMP attack renders electronic devices unusable. Recently, malfunctions of the Electronic Toll Collection System (ETC) at toll booths on toll roads have become a problem. Specifically, when large vehicles pass through an ETC lane in succession, the system may not be able to accurately determine whether or not the vehicles have passed through. This is believed to be caused by unintended reflection of radio waves. Furthermore, it is also necessary to block electromagnetic waves leaking from electronic devices, because if leaked electromagnetic waves are detected and analyzed, they can lead to information leakage. For this reason, many measures against electromagnetic waves have been proposed.

[0003] One of the measures against electromagnetic waves is something called a Faraday cage, which has long been well known. A Faraday cage refers to a container or cage made of a conductor, or a space enclosed by such a container or cage. Since electric field lines cannot penetrate into the space inside a conductor, the electric field from the outside is blocked. Specifically, electric charges are rearranged in the space to cancel out the electric field from the outside, so the electric field becomes zero. For example, Japanese Patent Application Laid-Open Nos. 9-257948 and 62-36565 disclose examples of using a Faraday cage. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-257948 [Patent Document 2] Japanese Patent Application Publication No. 62-36565 Summary of the Invention [Problem to be solved by the invention]

[0005] Metals are often used as conductors in Faraday cages. However, metals have low corrosion resistance and are therefore unsuitable for use outdoors where it may rain. The present invention has been made in consideration of the problems with the Faraday cages that have been used conventionally, and aims to provide an electromagnetic wave shielding structure that can be used as a constituent material of a Faraday cage to reinforce the weak points of the Faraday cage, and further, an electromagnetic wave shielding system that uses this electromagnetic wave shielding structure. [Means for solving the problem]

[0006] To achieve this object, the present invention provides an electromagnetic wave shielding structure (100, 100A) comprising a first member (110) made of a first material that is an electrical conductor, and a second member (120) made of a second material having a lower electrical conductivity than the first material and a higher corrosion resistance than the first material, wherein the second member (120) covers at least a portion of the surface of the first member (110). It is preferable that the first member (110) has a first surface (111) exposed to electromagnetic waves and a second surface (112) located opposite the first surface (111), and the second member (120) covers at least the first surface (111) of the first surface (111) and the second surface (112).

[0007] Of the first member (110) and the second member (120A), at least the second member (120A) preferably has a mesh structure. It is preferable that the second member (120B) is made up of at least two auxiliary mesh members (120X, 120Y) having mutually different mesh patterns, and that the auxiliary mesh members (120X, 120Y) are overlapped to cover the first member (110). The second member (120) has a first surface covering the surface of the first member (110) and a second surface located opposite the first surface, and it is preferable that the second surface has an uneven surface (122) or is formed in a corrugated shape. It is preferable that at least one of the surface (111) of the first member (110) on the side where the first member (110) contacts the second member (120) and the outer surface of the second member (120) is formed to have a surface roughness having a maximum height or maximum depth shorter than the wavelength of the external electromagnetic wave. The first member (110A) may be rod-shaped or wire-shaped, and the second member (120D) may cover the outer circumferential surface of the first member (110A).

[0008] The first material is, for example, gold, silver or copper. The second material is, for example, stainless steel or titanium. The second material is preferably one that does not reflect electromagnetic waves but transmits them, and in this case, for example, glass or resin is selected as the second material. The first members (100B, 100C) preferably have a mesh structure or a curved surface in contact with the second member (120) such that the surface is uneven (113) and is in contact with the second member (120). In this case, the second material is preferably a resin. It is preferable that one of the two surfaces of the first member and at least one of the outer surfaces of the second member have irregularities for diffusely reflecting external electromagnetic waves, and the height or depth of the irregularities is 1 / 10 to 1 / 50 of the wavelength of the external electromagnetic waves.

[0009] It is preferable that the electromagnetic wave shielding structure (100, 100A) further comprises a ground wire (130) for grounding the first member (110). The electromagnetic wave shielding structure (100C) is configured as a panel, and it is preferable that each side of the panel has a convex portion (101) and a concave portion (102) formed thereon to enable coupling with an adjacent panel. Furthermore, the present invention provides an electromagnetic wave shielding system installed in a travel lane (201) in which an ETC is installed, the electromagnetic wave shielding system comprising an electromagnetic wave shield (300, 350) formed between the travel lane (201) and a second travel lane (202) adjacent to the travel lane (201), the electromagnetic wave shielding preventing radio waves emitted from a roadside antenna (210A) installed in the second travel lane (202) and reflected off a vehicle (252) traveling in the second travel lane (202) from reaching the roadside antenna (210) of the travel lane (201), the electromagnetic wave shielding body (300, 350) being composed of the electromagnetic wave shielding structure described above.

[0010] The electromagnetic wave shield (300, 350) preferably has a length of at least one large vehicle. The electromagnetic wave shield is, for example, a wall-like structure (300). The height of the wall-like structure (300) is preferably set higher than the height of the roadside antenna (210) that transmits radio waves to traveling vehicles (251) in the travel lane (201). It is preferable that the wall-like structure has a length along the travel lane (201) that includes at least the roadside antenna (210) of the travel lane (201) therebetween. The electromagnetic wave shield may be configured, for example, as a tunnel-like structure (350) that covers the travel lane (201). It is preferable that the tunnel-like structure (350) has a length along the travel lane (201) that includes at least the roadside antenna (210) of the travel lane (201) therebetween.

[0011] Furthermore, the present invention provides an electromagnetic wave shielding system installed in a travel lane (201) in which an ETC is installed, the electromagnetic wave shielding system comprising an electromagnetic wave shielding body (360) arranged in front of a roadside antenna (210) installed in the travel lane (201) in the travel direction of a vehicle (251) traveling in the travel lane (201), the electromagnetic wave shielding body (360) being arranged so that radio waves emitted from the roadside antenna (210) reach a preceding vehicle (251), but a reflected wave (312) of a portion of the radio waves from a following vehicle (253) following the preceding vehicle (251) is located midway along the path toward the roadside antenna (210), and the electromagnetic wave shielding body (360) is composed of the above-mentioned electromagnetic wave shielding structure. The reference symbols in parentheses are intended to clarify the correspondence with the embodiments described below, and are not intended to limit the scope of the rights thereto. Effect of the Invention

[0012] In the electromagnetic wave shielding structure according to the present invention, the second material has higher corrosion resistance than the first material. Therefore, compared to a Faraday cage consisting only of a first member made of the first material, a Faraday cage made of this electromagnetic wave shielding structure has higher resistance to outdoor environments where moisture and other corrosive factors exist. Thus, a Faraday cage made of this electromagnetic wave shielding structure is more suitable for outdoor use than a conventional Faraday cage. The electromagnetic wave blocking system of the present invention can prevent interference of radio waves from roadside antennas between two adjacent driving lanes, thereby making it possible to prevent malfunction of ETC caused by such radio wave interference. [Brief description of the drawings]

[0013] [Figure 1] 1 is a perspective view of an electromagnetic wave shielding structure according to a first embodiment of the present invention; [Diagram 2] 11 is a plan view of a first modified example of a second member constituting an electromagnetic wave blocking structure. FIG. [Diagram 3] 13 is a plan view of a second modified example of the second member constituting the electromagnetic wave blocking structure. FIG. [Figure 4] FIG. 4(A) is a plan view of a third modified example of the second member that constitutes the electromagnetic wave shielding structure, and FIG. 4(B) is a side view of the same. [Diagram 5] FIG. 11 is a perspective view of an electromagnetic wave shielding structure according to a second embodiment of the present invention. [Figure 6] FIG. 11 is a perspective view of an electromagnetic wave blocking structure according to a third embodiment of the present invention. [Figure 7] FIG. 13 is a plan view of an electromagnetic wave blocking structure according to a fourth embodiment of the present invention. [Figure 8] FIG. 13 is a cross-sectional view of a first member according to a first example of the fifth embodiment of the present invention. [Figure 9] FIG. 13 is a cross-sectional view of a first member according to a second example of the fifth embodiment of the present invention. [Figure 10] FIG. 1 is a perspective view showing an overview of a toll booth of a toll road where ETC is installed. [Figure 11]13 is a front view of a first example of an electromagnetic wave shielding system according to a sixth embodiment of the present invention. FIG. [Figure 12] 13 is a front view of a second example of an electromagnetic wave shielding system according to a sixth embodiment of the present invention. FIG. [Figure 13] 13 is a schematic diagram showing the positional relationship between a roadside antenna, a traveling vehicle, and its following vehicle in an electromagnetic wave blocking system according to a seventh embodiment of the present invention, as viewed from the side. FIG. [Figure 14] FIG. 14 is a schematic view similar to FIG. 13, seen from above. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] First Embodiment FIG. 1 is a perspective view of an electromagnetic wave shielding structure 100 according to a first embodiment of the present invention. The electromagnetic wave shielding structure 100 is composed of a first member 110 made of a first material, a second member 120 made of a second material, and an earth wire 130 that earths the first member 110. The first member 110 has a cubic shape. The first material constituting the first member 110 is a conductor. For example, the first material is a metal, and more specifically, a highly conductive metal such as gold, silver, or copper. The second member 120 has a flat plate shape with a constant thickness. The second material of the second member 120 is made of a material having a lower electrical conductivity than the first material and a higher corrosion resistance than the first material, for example, stainless steel or titanium.

[0015] A first member 110 having a cubic shape has a first surface 111 and a second surface 112 located opposite to the first surface 111 . When the electromagnetic wave blocking structure 100 is exposed to electromagnetic waves, for example, assuming that the first surface 111 of the first member 110 is exposed to the electromagnetic waves, the second member 120 is configured to completely cover the first surface 111 of the first member 110. When external electromagnetic waves strike the second member 120, part of the electromagnetic waves is reflected by the surface of the second member 120. The remaining electromagnetic waves pass through the second member 120, strike the first member 110, and are emitted to the ground via the earth wire 130. In other words, by grounding the first member 110, it is possible to prevent the electromagnetic waves from leaking to the outside. As a result, the external electromagnetic waves cannot pass (penetrate) through the electromagnetic wave blocking structure 100. From the outside, it appears that the external electromagnetic waves are absorbed by the electromagnetic wave blocking structure 100 (absorption effect).

[0016] The second material has higher corrosion resistance than the first material. Therefore, compared to a Faraday cage made only of the first member made of the first material, the Faraday cage made of the electromagnetic wave shielding structure 100 has higher resistance to outdoor environments where moisture and other corrosive factors exist. Thus, the Faraday cage made of the electromagnetic wave shielding structure 100 is more suitable for outdoor use than the conventional Faraday cage. The electromagnetic wave shielding structure 100 according to this embodiment is not limited to the above-mentioned structure, and various modifications are possible. Although the electromagnetic wave shielding structure 100 according to this embodiment is configured to include the ground wire 130, it is not necessarily required that the electromagnetic wave shielding structure 100 has the ground wire 130 from the beginning. For example, it is possible to first manufacture the electromagnetic wave shielding structure 100 without the earth wire 130, and then additionally provide an earth wire 130 connecting the first member 110 to the ground at the installation location of the Faraday cage consisting of the electromagnetic wave shielding structure 100.

[0017] In this embodiment, the first member 110 is configured to have a cubic shape, but the shape of the first member 110 is arbitrary. Any shape is possible. In this embodiment, the second member 120 is configured to completely cover the first surface 111 of the first member 110, but it is also possible for the second member 120 to be configured to partially cover the first surface 111. For example, in an environment in which electromagnetic waves are concentrated only in a partial area of ​​the first surface 111 of the first member 110 , it is possible to cover only that area with the second member 120 . In the electromagnetic wave blocking structure 100 of this embodiment, stainless steel or titanium is given as an example of the second material constituting the second member 120. However, even if measures are taken to prevent or reduce reflection on the surface of the second member 120 (for example, see Figures 4(A) and 4(B) described below), it is not possible to completely suppress the generation of reflected waves.

[0018] For this reason, it is possible to use a material that does not reflect electromagnetic waves but transmits them, such as glass or resin, as the second material. The electromagnetic waves pass through the second member 120 made of glass or resin, are absorbed by the first member 110, and are then released into the ground via the earth wire 130. In this embodiment, the second member 120 is configured to have a flat plate shape, but the shape of the second member 120 is not limited to a flat plate. FIG. 2 is a plan view of a first modified example of the second member 120. As shown in FIG. The second member 120A according to the first modified example is formed in a mesh shape. For example, as shown in Fig. 2, the second member 120A has holes 121 of the same diameter formed in a matrix shape, thereby forming a mesh structure. By making the second member 120A have a mesh structure, it is possible to reduce manufacturing costs by reducing the amount of material, to make the member lighter, to improve wind resistance, and to improve visibility (the condition of the first member 110 can be visually grasped). The shape of the mesh is arbitrary. For example, the second member 120A may be formed in a net shape (mesh shape), and the mesh shape can be selected according to the situation.

[0019] It is not necessary that all the holes 121 have the same diameter, and it is also possible for the diameters of the multiple holes 121 to be different from one another. Also, it is also possible to form the multiple holes 121 randomly rather than in a matrix pattern. It is also possible to form not only the second member 120A but also the first member 110 into a mesh structure similar to that of the second member 120A, that is, to form the electromagnetic wave shielding structure 100 into a mesh structure as a whole. In this case, the mesh pattern of the first member 110 and the mesh pattern of the second member 120A may be the same or different from each other. FIG. 3 is a perspective view of a second modified example of the second member 120. As shown in FIG. As shown in FIG. 3, the second member 120B in the second modified example is made up of two auxiliary members 120X and 120Y. The auxiliary member 120X is the same as the second member 120A shown in FIG. Auxiliary member 120Y has a mesh shape with a plurality of holes formed in a matrix, but the diameter of each hole of auxiliary member 120Y and the distance (pitch) between adjacent holes are different from those of auxiliary member 120X.

[0020] That is, the auxiliary members 120X and 120Y both have a mesh shape, but the mesh patterns are different from each other. 3, the auxiliary member 120X and the auxiliary member 120Y are attached in an overlapping state so as to cover the first surface 111 of the first member 110. Specifically, the auxiliary member 120X is attached so as to cover the first surface 111 of the first member 110, and the auxiliary member 120Y is attached so as to cover the surface of the auxiliary member 120X. Which mesh pattern is effective for an external electromagnetic wave varies depending on external factors such as the physical properties (amplitude, wavelength, etc.) of the external electromagnetic wave and the angle of incidence, etc. For this reason, by overlapping two auxiliary members 120X and 120Y with different mesh patterns, it is possible to improve the effectiveness of blocking various external electromagnetic waves. In this embodiment, the second member 120B is configured to include two auxiliary members 120X and 120Y, but the number of auxiliary members that configure the second member 120B is not limited to two. It is also possible to use three or more auxiliary members. The more auxiliary members are used, the more effective the blocking of various external electromagnetic waves becomes.

[0021] FIG. 4(A) is a plan view of a third modified example of the second member 120, and FIG. 4(B) is a side view of the same. As shown in Figures 4(A) and 4(B), the second member 120C in the third modified example has a plurality of identically shaped convex bodies 122 formed in a matrix pattern on its outer surface (the surface opposite to the surface in contact with the first member 110). Each of the convex bodies 122 has a regular square pyramid shape. 1 to 3, a part of the external electromagnetic wave is reflected by the second members 120, 120A, and 120B. By forming the convex body 122 on the surface of the second member 120C, it becomes possible to diffusely reflect (scatter) the external electromagnetic wave, and it is possible to suppress the propagation of energy due to the reflection. The shape of the convex body 122 is not limited to a regular square pyramid. Any shape can be selected. In addition, all the convex bodies 122 do not need to have the same shape, and at least some of the convex bodies 122 can have a different shape from the other convex bodies 122.

[0022] It is also possible to form a concave body instead of the convex body 122, and it is also possible to form the convex body 122 and the concave body in combination. Alternatively, instead of forming the convex bodies 122, the surface of the second member 120C may be formed in a corrugated shape. In order to diffusely reflect external electromagnetic waves using surface irregularities, it is considered appropriate that the height or depth of the irregularities is about 1 / 10 to 1 / 50 of the wavelength. For example, among external electromagnetic waves (electromagnetic waves present in the natural environment), ultraviolet rays have the shortest wavelength, which is about 10 to 200 nm. Therefore, for example, the height or depth of the irregularities for ultraviolet rays is set to about 2 nm to 10 nm. When forming irregularities for diffusely reflecting external electromagnetic waves on the first surface 111, the second surface 112, or the outer surface of the second member 120 (the surface opposite to the surface in contact with the first surface 111 of the first member 110), it is preferable to set the height or depth of the irregularities to approximately 1 / 10 to 1 / 50 of the wavelength of the external electromagnetic waves.

[0023] Second Embodiment FIG. 5 is a perspective view of an electromagnetic wave blocking structure 100A according to the second embodiment of the present invention. 1, the second member 120 is attached only to one surface (first surface 111) of the first member 110. In contrast, in the electromagnetic wave shielding structure 100A according to this embodiment, the second member 120 is attached to both surfaces (first surface 111 and second surface 112) of the first member 110. In this way, by disposing the second member 120 on both sides 111, 112 of the first member 110, it is possible to improve the electromagnetic wave absorption and resistance to the outdoor environment, and it becomes unnecessary to consider the orientation of the electromagnetic wave shielding structure 100A. That is, in the electromagnetic wave shielding structure 100, it was necessary to orient the second member 120 toward the side exposed to external electromagnetic waves, but in the electromagnetic wave shielding structure 100A, since the second members 120 are attached to both sides of the first member 110, it becomes unnecessary to consider such an orientation.

[0024] Third embodiment FIG. 6 is a perspective view of an electromagnetic wave blocking structure 100B according to a third embodiment of the present invention. In this embodiment, the first member 110A is rod-shaped or linear (wire-shaped), and the second member 120D is configured to cover the outer circumferential surface of the first member 110A. The electromagnetic wave blocking structure 100B also provides the same effects as the electromagnetic wave blocking structure 100 according to the first embodiment. Moreover, by weaving the wire-shaped electromagnetic wave shielding structure 100B, a mesh-shaped electromagnetic wave shielding structure can be formed. Even if the first member 110 is not flat (FIG. 1) but rod-like or wire-like, it is possible to form an electromagnetic wave shielding structure as in this embodiment.

[0025] (Fourth embodiment) FIG. 7 is a plan view of an electromagnetic wave blocking structure 100C according to a fourth embodiment of the present invention. The electromagnetic wave blocking structure 100C is, for example, the electromagnetic wave blocking structure 100 according to the first embodiment configured as a square panel. A protrusion 101 and a recess 102 are formed at the same position on each of the four sides of the panel 100C. Both the protrusion 101 and the recess 102 are cubic in shape, and the protrusion 101 can be fitted into the recess 102. The two panels 100C can be joined together by fitting the protruding portion 101 and the recessed portion 102 on one side of the panel 100C into the recessed portion 102 and the protruding portion 101 on one side of the adjacent panel 100C, respectively. In this way, by providing the convex portions 101 and the concave portions 102 on each side of the panel 100C, the required number of panels 100C can be joined together. The shapes of the convex portion 101 and the concave portion 102 are arbitrary. As long as the convex portion 101 can be fitted into the concave portion 102, the convex portion 101 and the concave portion 102 can have any shape.

[0026] Fifth embodiment The first member 110 may not be able to absorb all of the electromagnetic waves that have passed through the second member 120, and some of the electromagnetic waves may be reflected. In this embodiment, the shape of the first member 110 is changed from the flat plate shape in the above embodiment to a shape that addresses this problem. In this embodiment, the first member 110 is configured to have a structure that diffuses and reflects electromagnetic waves that cannot be absorbed by the first member 110 . FIG. 8 is a cross-sectional view of a first member 110B according to a first example of this embodiment. The first member 110B has a corrugated shape on the surface in contact with the second member 120. Most of the electromagnetic waves that have passed through the second member 120 are absorbed by the first member 110B, and then discharged to the ground via the earth wire 130. The electromagnetic waves that are not absorbed by the first member 110B are diffusely reflected by the corrugated surface of the first member 110B and are attenuated. In this way, by forming the first member 110B in a corrugated shape, it is possible to effectively deal with the electromagnetic waves that have passed through the second member 120.

[0027] The shape of the first member 110B is not limited to a corrugated shape, and may be any shape as long as it is curved. Also, it is not limited to a regularly curved structure such as the corrugated structure shown in FIG. 8, and may be an irregularly curved structure. When selecting the first member 110B having a corrugated shape, it is preferable that the second material constituting the second member 120 is resin. If glass or metal is selected as the second material constituting the second member 120, it is necessary to mold the second member 120 to match the corrugated shape of the first member 110B, but if resin is selected as the second material, it is possible to form the second member 120 by coating the corrugated surface of the first member 110B with liquid resin and drying it, and the manufacturing process of the second member 120 can be significantly simplified.

[0028] Also, as shown by the dashed lines in FIG. 8, it is possible to provide second members 120 on both sides of the first member 110B. FIG. 9 is a cross-sectional view of a first member 110C according to a second example of this embodiment. In the first member 110C, on the surface (first surface 111 in FIG. 1) in contact with the second member 120, convex bodies 113 similar to the convex bodies 122 shown in FIG. 4 are regularly formed. As in the case of the corrugated first member 110B, the electromagnetic waves that are not absorbed by the first member 110C are diffusely reflected by the convex portions 113 formed on the surface of the first member 110C and are attenuated. As in the case of the convex body 122, the shape of the convex body 113 is arbitrary, and it is also possible to form a concave body instead of the convex body 113, or to form a combination of the convex body 113 and a concave body.

[0029] As in the first example shown in FIG. 8, the second material constituting the second member 120 is preferably a resin. In addition, as shown by the dashed line in Figure 9, a convex body 113 can also be formed on the opposite surface of the first member 110C (the second surface 112 in Figure 1), and this convex body 113 can also be covered with a second member 120 made of resin. As a third example, the first member 110 may have a mesh structure similar to the second member 120A (see FIG. 2). By forming the first member 110 in a mesh structure, electromagnetic waves that are not absorbed by the first member 110 can be diffusely reflected and attenuated, similar to the case of the first member 110B having a corrugated shape. As a fourth example of this embodiment, it is possible to form minute irregularities on the first surface 111 of the first member 110 (to make the first surface 111 of the first member 110 rough).

[0030] For example, among external electromagnetic waves (electromagnetic waves existing in the natural environment), ultraviolet rays have the shortest wavelength, which is about 10 to 200 nm. Therefore, in reality, it is possible to reflect external electromagnetic waves without forming a relatively large object such as the convex body 113 on the first surface 111 of the first member 110. For this reason, it is sufficient that the first surface 111 of the first member 110 has irregularities with a height or depth shorter than the wavelength of the external electromagnetic wave (for example, ultraviolet light). That is, if the first surface 111 of the first member 110 is formed to have a surface roughness with a maximum height or maximum depth shorter than the wavelength of the external electromagnetic wave, the external electromagnetic wave can be diffusely reflected, and as a result, attenuated. As in the first example, when minute projections and recesses are formed on first surface 111 of first member 110, the second material constituting second member 120 is preferably a resin. It is also possible to form minute projections and recesses on both sides 111 and 112 of the first member 110, and it is also possible to form minute projections and recesses on the outer surface of the second member 120.

[0031] (Sixth embodiment) This embodiment relates to a first example of an electromagnetic wave shielding system using the above-mentioned electromagnetic wave shielding structures 100, 100A, and 100C. As described above, in recent years, there have been problems with ETC malfunctions at toll booths where ETC is installed on toll roads. The electromagnetic wave blocking system according to this embodiment is intended to address these problems. Generally, ETC is a system for automatically paying tolls by wirelessly communicating between roadside antennas installed at toll gates on expressways and other toll roads and an ETC on-board unit installed in a vehicle. FIG. 10 is a perspective view showing an overview of a toll booth of a toll road where an ETC is installed. For example, assume that there is a first driving lane 201 and an adjacent second driving lane 202. A toll booth is provided for each driving lane. The case of the first driving lane 201 will be described below. The ETC installed in the first travel lane 201 is composed of a roadside antenna 210 that transmits radio waves to an ETC on-board unit mounted on a traveling vehicle, a display panel 220 that displays the toll, and an opening and closing bar 230 that opens and closes the first travel lane 201.

[0032] The roadside antenna 210 is attached to an attachment bar 211 that spans the first driving lane 201, is positioned in the center of the first driving lane 201, and transmits radio waves to the moving vehicle 251 from above the moving vehicle 251. When a traveling vehicle is identified by wireless communication between the roadside antenna 210 and the ETC vehicle-mounted unit, the toll is displayed on the display panel 220, and when the toll payment is completed, the gate barrier 230, which was closed until then, opens. When a traveling vehicle 251 passes the gate barrier 230, the gate barrier 230 closes. As described above, when vehicles (especially large vehicles) pass through the driving lane in succession, it may not be possible to accurately determine whether or not these vehicles have passed through. The presumed cause of this is explained below.

[0033] When a vehicle 251 traveling in the first travel lane 201 approaches the roadside antenna 210, the roadside antenna 210 detects the presence of the vehicle 251 and transmits radio waves toward the vehicle 251. When an ETC vehicle-mounted unit mounted on the vehicle 251 receives radio waves from the roadside antenna 210, the ETC vehicle-mounted unit transmits ID information for identifying the vehicle 251 toward the roadside antenna 210. When the payment of the toll is completed via wireless communication between the roadside antenna 210 and the ETC vehicle-mounted unit, the gate 230 opens. It is assumed that when a vehicle 251 is approaching the roadside antenna 210, a vehicle 252 is also approaching a roadside antenna 210A of a second travel lane 202 adjacent to the first travel lane 201. In this case, the roadside antenna 210A of the second travel lane 202 transmits radio waves to the approaching vehicle 252, similar to the roadside antenna 210. A part of the radio waves transmitted by the roadside antenna 210A is received by the ETC on-board unit of the vehicle 252, but a part of the radio waves that is not received by the ETC on-board unit may be reflected back to the vehicle 252. When a part of this reflected radio wave is received by the roadside antenna 210 of the first travel lane 201, the roadside antenna 210 receives a double reception of the radio wave from the ETC on-board unit of the vehicle 251 and the reflected radio wave from the vehicle 252. As a result, the roadside antenna 210 judges this state of double reception to be an error, and keeps the gate 230 closed without opening it. This makes it impossible for the vehicle 251 to pass through the toll gate.

[0034] Thus, the malfunction of the ETC (the inability of the ETC to accurately determine whether vehicle 251 should be allowed to pass) is thought to be caused by interference of radio waves from roadside antennas 210, 210A between two adjacent driving lanes 201, 202. FIG. 11 is a front view of a first example of an electromagnetic wave shielding system according to this embodiment. The electromagnetic wave shielding system according to the first example is configured as a radio wave shielding wall 300. The radio wave shielding wall 300 stands upright between a first driving lane 201 and a second driving lane 202. By providing the radio wave shielding wall 300, radio waves reflected from the vehicle 252 traveling in the second travel lane 202 are absorbed or reflected by the radio wave shielding wall 300 and do not reach the roadside antenna 210 in the first travel lane 201. This allows the roadside antenna 210 to receive only radio waves transmitted from the ETC on-board unit of the vehicle 251 traveling in the first travel lane 201, preventing the above-mentioned double reception and ultimately preventing malfunction of the ETC.

[0035] At present, the walls of toll booths where ETC is installed are sometimes covered with fabrics that have high electromagnetic wave absorption properties, but the effect of preventing electromagnetic wave reflection is limited to the walls of the toll booths, and it is impossible to prevent the reflected radio waves from the adjacent second travel lane 202 from reaching the roadside antenna 210, so the problem of reflection from adjacent travel lanes has not been solved. In order to completely solve this problem, it is necessary to install a radio wave shielding wall 300. The radio wave shielding wall 300 can be provided over the length L1 (see FIG. 10) from the roadside antenna 210 to the gate bar 230, but it is preferable to provide it within the range of the length L2 (see FIG. 10) including the roadside antenna 210 (the length on both sides of the roadside antenna 210) at the shortest. In that case, the length of the radio wave shielding wall 300 needs to be the length of one vehicle, specifically, the length of one large vehicle. As shown in FIG. 11, it is preferable that the height of the radio wave shielding wall 300 is higher than the position of the roadside antenna 210.

[0036] By setting the radio wave shielding wall 300 higher than the position of the roadside antenna 210, the reflected radio waves from the adjacent second driving lane 202 cannot pass over the radio wave shielding wall 300 and enter the first driving lane 201, so that all reflected radio waves from the second driving lane 202 are absorbed or reflected by the radio wave shielding wall 300 and do not reach the roadside antenna 210. FIG. 12 is a front view of a second example of an electromagnetic wave shielding system according to this embodiment. The electromagnetic wave blocking system according to the second example is configured as a tunnel 350 covering the first travel lane 201 . By providing the tunnel 350, as in the case of the radio wave shielding wall 300, radio waves reflected from the vehicle 252 traveling in the second travel lane 202 are absorbed or reflected by the tunnel 350 and do not reach the roadside antenna 210 in the first travel lane 201. Therefore, the roadside antenna 210 can receive only radio waves transmitted from the ETC on-board unit of the vehicle 251 traveling in the first travel lane 201, thereby preventing the above-mentioned double reception.

[0037] The height of the tunnel 350 is set to a height that can accommodate the roadside antenna 210 therein, as shown in FIG. Similarly to the position of the radio wave shielding wall 300, the position of the tunnel 350 is set within a range of at least the length L2, and the length of the tunnel 350 is set to at least the length of one large vehicle, similar to the length of the radio wave shielding wall 300. The frequency of the radio waves emitted by the roadside antenna 210 is set to 5.8 GHz by the standard (DSRC standard). As described above, in order to diffusely reflect (scatter) external electromagnetic waves by surface irregularities, it is considered appropriate that the height or depth of the irregularities is about 1 / 10 to 1 / 50 of the wavelength. The wavelength of 5.8 GHz band radio waves is about 5.2 cm. Therefore, when using an electromagnetic wave shielding structure in which the convex bodies 113, 122 are formed on the surface of the first member 110 or the second member 120 as the radio wave shielding wall 300 or the tunnel 350, or an electromagnetic wave shielding structure in which the surface of the first member 110 or the second member 120 is given a predetermined surface roughness, it is effective to set the height or depth of the irregularities in the range of 2 mm to 1 cm.

[0038] Seventh embodiment This embodiment relates to a second example of an electromagnetic wave shielding system using the above-mentioned electromagnetic wave shielding structures 100, 100A, and 100C. The electromagnetic wave blocking system according to the sixth embodiment described above is intended to prevent problems caused by radio waves reflected from the adjacent second travel lane 202 reaching the roadside antenna 210 in the first travel lane 201, but there is another reason why such problems may occur. FIG. 13 is a schematic diagram showing the positional relationship between the roadside antenna 210, a traveling vehicle 251, and its following vehicle 253 as seen from the side, and FIG. 14 is a schematic diagram showing the positional relationship as seen from above. 13, a part 311 of radio waves 310 emitted by roadside antenna 210 toward vehicle 251 traveling in first travel lane 201 may be reflected by the body of vehicle 251 (for example, the roof or side body of vehicle 251) and reach following vehicle 253 as reflected wave 311A. Reflected wave 311A ​​that reaches following vehicle 253 may be further reflected by the body of following vehicle 253, and this reflected wave 312 may reach roadside antenna 210. In this way, reflected wave 312 from following vehicle 253 behind vehicle 251 reaching roadside antenna 210 may also cause a problem in that it is not possible to accurately determine whether a vehicle is passing.

[0039] The electromagnetic wave blocking system according to this embodiment is intended to address such problems. The electromagnetic wave shielding system according to this embodiment includes a radio wave shielding wall 360 that is disposed in front of the roadside antenna 210 when viewed in the direction in which the vehicle 251 is traveling. The radio wave shielding wall 360, like the radio wave shielding wall 300 and the tunnel 350, is made up of the electromagnetic wave shielding structures 100, 100A, and 100C and has a flat plate shape. For example, roadside antenna 210 is set to emit radio waves when vehicle 251 approaches within a distance M1 of 30 m. Since the legal speed limit for passing through a toll booth where ETC is installed is 20 km / h or less, it can be estimated that inter-vehicle distance M2 between vehicle 251 and following vehicle 253 is approximately 20 m. The position of radio wave shielding wall 360 is determined under these conditions, which are given as an example.

[0040] The radio wave shielding wall 360 is installed so that its upper end is at the same height as the upper end of the roadside antenna 210, and its length (height) H in the vertical direction (or the position of its lower end) is set as follows. The length H of the roadside antenna 210 is set so that the radio wave emitted from the roadside antenna 210 reaches the vehicle 251 without being blocked by the radio wave shielding wall 360, but blocks the reflected wave 312 from the following vehicle 253 when the reflected wave 312 heads toward the roadside antenna 210. In other words, the length H of the radio wave shielding wall 360 is determined so that the radio wave emitted from the roadside antenna 210 reaches the preceding vehicle 251 regardless of the positions of the upper and lower ends of the radio wave shielding wall 360, but the radio wave shielding wall 360 is located in the middle of the path of the reflected wave 312 from the following vehicle 253 following the preceding vehicle 251 toward the roadside antenna 210. 14, the width W of the radio wave shielding wall 360 is equal to the width of the first driving lane 201. Since the roadside antenna 210 is located in the center of the first driving lane 201, the roadside antenna 210 is entirely covered by the radio wave shielding wall 360 in the horizontal direction.

[0041] As described above, according to the electromagnetic wave blocking system of this embodiment, it is possible to prevent the reflected wave 312 from the following vehicle 253 from reaching the roadside antenna 210, and therefore it is possible to prevent the occurrence of problems caused by the reflected wave 312 from the following vehicle 253. The radio wave shielding wall 360 in this embodiment can be used together with the radio wave shielding wall 300 in the sixth embodiment. [Industrial Applicability]

[0042] The electromagnetic wave shielding structure according to the present invention can be used in a wide range of applications, for example, as building materials for nuclear shelters, materials for protective facilities or equipment against electromagnetic pulse attacks (EMP), and covers for electronic devices against electromagnetic interference. The electromagnetic wave blocking system that uses the electromagnetic wave blocking structure can be used not only as a countermeasure against the above-mentioned ETC problems, but also as an evacuation facility against lightning strikes. [Explanation of symbols]

[0043] 100 Electromagnetic wave shielding structure according to the first embodiment of the present invention 110 First member 120, 120A Second member 130 Earth Wire 201 First Travel Lane 202 Second Travel Lane 210,210A Roadside antenna 251,252,253 vehicles 300 Radio wave shielding wall 350 Tunnel 360 Radio wave shielding wall

Claims

1. a first member made of a first material that is an electrical conductor; a second member made of a second material having a lower electrical conductivity than the first material and a higher corrosion resistance than the first material; An electromagnetic wave shielding structure comprising: The electromagnetic wave shielding structure, wherein the second member covers at least a portion of the surface of the first member.

2. the first member has a first surface exposed to electromagnetic waves and a second surface located opposite the first surface, 2. The electromagnetic wave shielding structure according to claim 1, wherein the second member covers at least the first surface out of the first surface and the second surface.

3. 3. The electromagnetic wave shielding structure according to claim 2, wherein at least the second member out of the first member and the second member has a mesh structure.

4. 3. The electromagnetic wave shielding structure according to claim 2, wherein the second member is made up of at least two auxiliary mesh members having mutually different mesh patterns, and the auxiliary mesh members are overlapped to cover the first member.

5. the second member has a first surface covering a surface of the first member and a second surface located on the opposite side to the first surface, 3. The electromagnetic wave shielding structure according to claim 2, wherein the second surface has an uneven surface or the second surface is formed in a corrugated shape.

6. 2. The electromagnetic wave shielding structure according to claim 1, wherein at least one of the surface of the first member on the side where the first member contacts the second member and the outer surface of the second member is formed to have a surface roughness having a maximum height or maximum depth shorter than the wavelength of the external electromagnetic wave.

7. 2. The electromagnetic wave shielding structure according to claim 1, wherein the first member is rod-shaped or wire-shaped, and the second member covers an outer peripheral surface of the first member.

8. 2. The electromagnetic wave shielding structure according to claim 1, wherein the first material is gold, silver or copper.

9. 2. The electromagnetic wave shielding structure according to claim 1, wherein the second material is stainless steel or titanium.

10. 2. The electromagnetic wave shielding structure according to claim 1, wherein the second material has a property of not reflecting electromagnetic waves but transmitting them.

11. 11. The electromagnetic wave shielding structure according to claim 10, wherein the second material is glass or resin.

12. 2. The electromagnetic wave shielding structure according to claim 1, wherein the first member has an uneven surface in contact with the second member, is formed as a mesh structure, or has a curved surface in contact with the second member.

13. 13. The electromagnetic wave shielding structure according to claim 12, wherein the second material is a resin.

14. The electromagnetic wave blocking structure according to claim 1, characterized in that either one of the two surfaces of the first member and at least one of the outer surfaces of the second member have irregularities for scattering external electromagnetic waves, and the height or depth of the irregularities is 1 / 10 to 1 / 50 of the wavelength of the external electromagnetic waves.

15. 2. The electromagnetic wave shielding structure according to claim 1, further comprising a ground wire for grounding the first member.

16. 2. The electromagnetic wave shielding structure according to claim 1, wherein the electromagnetic wave shielding structure is configured as a panel, and each side of the panel is formed with a convex portion and a concave portion to enable connection with an adjacent panel.

17. An electromagnetic wave shielding system installed in a driving lane where an ETC is installed, The electromagnetic wave shielding system includes an electromagnetic wave shield formed between the driving lane and a second driving lane adjacent to the driving lane, the electromagnetic wave shield prevents radio waves emitted from a roadside antenna installed in the second travel lane and reflected by a vehicle traveling in the second travel lane from reaching the roadside antenna of the travel lane, 17. An electromagnetic wave shielding system, comprising the electromagnetic wave shielding structure according to claim 1.

18. 20. The electromagnetic wave shielding system according to claim 17, wherein the electromagnetic wave shield has a length equal to at least the length of one large vehicle.

19. The electromagnetic wave shielding system according to claim 17, wherein the electromagnetic wave shielding body is a wall-shaped structure.

20. 20. The electromagnetic wave shielding system according to claim 19, wherein the height of the wall-like structure is set to be higher than the height of the roadside antenna that transmits radio waves to vehicles traveling in the travel lane.

21. The electromagnetic wave shielding system according to claim 19, characterized in that the wall-like structure has a length along the travel lane that includes at least the roadside antenna of the travel lane between them.

22. The electromagnetic wave shielding system according to claim 17, wherein the electromagnetic wave shielding body is a tunnel-shaped structure covering the driving lane.

23. The electromagnetic wave shielding system according to claim 22, wherein the tunnel-like structure has a length along the travel lane that includes at least the roadside antenna of the travel lane.

24. An electromagnetic wave shielding system installed in a driving lane where an ETC is installed, The electromagnetic wave shielding system includes an electromagnetic wave shielding body arranged in front of a roadside antenna installed in the travel lane in a travel direction of a vehicle traveling in the travel lane, the electromagnetic wave shield is disposed so that radio waves emitted from the roadside antenna reach the preceding vehicle, but a part of the radio waves reflected from a following vehicle following the preceding vehicle is located midway along a path toward the roadside antenna, 17. An electromagnetic wave shielding system, comprising the electromagnetic wave shielding structure according to claim 1.

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