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 relates to an electromagnetic wave shielding system applying this electromagnetic wave shielding structure. This electromagnetic wave shielding structure serves as a material for a Faraday cage.

Background Art

[0002] In recent years, many problems have occurred due to electromagnetic waves (external electromagnetic waves). For example, electromagnetic wave noise generated from various devices causes malfunction of electronic devices. In view of the international situation, the risk of an attack by EMP (Electromagnetic Pulse) cannot be ignored. When receiving an attack by EMP, in many cases, electronic devices become inoperable. Also, recently, malfunction of ETC (Electronic Toll Collection System) at toll gates where ETC for toll roads is installed has been regarded as a problem. Specifically, there is a problem that when large vehicles continuously pass through the driving lane for ETC, it may not be possible to accurately determine the passage of those vehicles. It is presumed to be caused by unintended radio wave reflection. Furthermore, it is also necessary to block electromagnetic waves leaking from electronic devices. This is because if the leaked electromagnetic waves are detected and analyzed, it will lead to information leakage. Therefore, many countermeasures against electromagnetic waves have been proposed so far.

[0003] As one of the countermeasures against electromagnetic waves, there is something called a Faraday cage which has been well-known for a long time. A Faraday cage refers to a vessel or cage made of a conductor, or a space surrounded by such a vessel or cage. Since electric lines of force cannot enter the internal space surrounded by the conductor, the external electric field is shielded. Specifically, in the space, charges are redistributed so as to cancel the external electric field, and thus the electric field becomes zero. For example, Japanese Patent Publication No. 9-257948 and Japanese Patent Publication No. 62-36565 describe examples of the use of 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 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Metals are frequently used as conductors in the construction of Faraday cages. However, metals have poor corrosion resistance, making them unsuitable for outdoor use in rainy conditions. This invention was made in view of the problems with conventionally used Faraday cages, and aims to provide an electromagnetic wave shielding structure as a constituent material for a Faraday cage that reinforces the weaknesses of the Faraday cage, and furthermore, an electromagnetic wave shielding system using this electromagnetic wave shielding structure. [Means for solving the problem]

[0006] To achieve this objective, the present invention provides an electromagnetic wave shielding structure (100, 100A) comprising a first member (110) made of a first conductive material and a second member (120) made of a second material having a conductivity lower than that of the first material and higher corrosion resistance than that of the first material, wherein the second member (120) covers at least a portion of the surface of the first member (110), and at least one of the surface (111) of the first member (110) on the side of the first member (110) that is in contact with the second member (120) and the outer surface of the second member (120) The electromagnetic wave shielding structure (100, 100A) has irregularities formed on it to diffusely reflect the external electromagnetic waves that it is intended to shield, and the height or depth of the irregularities is 1 / 10 to 1 / 50 of the wavelength of the external electromagnetic waves. An electromagnetic wave shielding structure (100, 100A) is provided. The first member (110) has a first surface (111) that is exposed to electromagnetic waves and a second surface (112) located on the opposite side of the first surface (111), and it is preferable that the second member (120) covers at least the first surface (111) of the first surface (111) and the second surface (112).

[0007] Preferably, of the first member (110) and the second member (120A), at least the second member (120A) has a mesh structure. Preferably, the second member (120B) consists of at least two auxiliary mesh members (120X, 120Y) with mutually different mesh patterns, and covers the first member (110) with the auxiliary mesh members (120X, 120Y) overlapping. The second member (120) has a first surface that covers the surface of the first member (110) and a second surface located on the opposite side of the first surface, and it is preferable that the surface of the second surface has irregularities (122) or that the second surface is formed in a corrugated shape. 。 The aforementioned The first member (110A) may be rod-shaped or linear, and the second member (120D) may cover the outer surface of the first member (110A).

[0008] The first material mentioned above is, for example, gold, silver, or copper. The second material is, for example, stainless steel or titanium. Preferably, the second material has the property of transmitting electromagnetic waves rather than reflecting them. In this case, for example, glass or resin can be selected as the second material. The first member (100B, 100C) preferably has irregularities (113) formed on the surface in contact with the second member (120), forming a mesh structure, or the surface in contact with the second member (120) is curved. In this case, the second material is preferably resin. stomach.

[0009] Preferably, the electromagnetic wave shielding structure (100, 100A) further comprises a grounding wire (130) for grounding the first member (110). The aforementioned electromagnetic wave shielding structure (100C) flat It is configured as a panel, and each side of the panel has a protrusion (101) and a recess (102) to enable connection with an adjacent panel. Within the same plane as the aforementioned panel It is preferable that it is formed. Furthermore, the present invention provides an electromagnetic wave shielding system installed in a driving lane (201) where an ETC is installed, wherein the electromagnetic wave shielding system comprises an electromagnetic wave shielding body (300, 350) formed between the driving lane (201) and a second driving lane (202) adjacent to the driving lane (201), the electromagnetic wave shielding body prevents radio waves emitted from a roadside antenna (210A) installed in the second driving lane (202) and reflected after hitting a vehicle (252) traveling in the second driving lane (202) from reaching the roadside antenna (210) in the driving lane (201), and the electromagnetic wave shielding body (300, 350) is made of the above-described electromagnetic wave shielding structure.

[0010] Preferably, the electromagnetic shielding body (300, 350) has a length equivalent to at least one large vehicle. The electromagnetic shielding body is, for example, a wall-like structure (300). It is preferable that the height of the wall-like structure (300) is set higher than the height of the roadside antenna (210) that transmits radio waves to the vehicle (251) traveling in the travel lane (201). Preferably, 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) in between. The electromagnetic wave shielding body can also be configured, for example, as a tunnel-shaped structure (350) that covers the driving lane (201). Preferably, the tunnel-shaped 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 is an electromagnetic wave shielding system installed in a travel lane (201) where ETC is installed. The electromagnetic wave shielding system includes an electromagnetic wave shielding body (360) disposed on the front side of a roadside antenna (210) installed in the travel lane (201) in the travel direction of a vehicle (251) traveling on the travel lane (201). The electromagnetic wave shielding body (360) is arranged such that radio waves emitted from the roadside antenna (210) reach the preceding vehicle (251), but a part of the reflected wave (312) of the radio waves from the succeeding vehicle (253) following the preceding vehicle (251) is located in the path toward the roadside antenna (210). The electromagnetic wave shielding body (360) provides an electromagnetic wave blocking system that is composed of the above-described electromagnetic wave blocking structure. The reference numerals in parentheses are for clarifying the correspondence with the embodiments described later and are not intended to limit the scope of the rights.

Advantages of the Invention

[0012] In the electromagnetic wave blocking structure according to the present invention, the second material has higher corrosion resistance than the first material. Therefore, compared with a Faraday cage composed only of the first member made of the first material, the Faraday cage composed of the present electromagnetic wave blocking structure has higher resistance to an outdoor environment where moisture and other corrosion factors exist. Thus, the Faraday cage composed of the present electromagnetic wave blocking structure is more suitable for outdoor use than a conventional Faraday cage. According to the electromagnetic wave shielding system of the present invention, it is possible to prevent interference of radio waves of roadside antennas between two adjacent travel lanes, and it is possible to prevent malfunction of ETC caused by such radio wave interference.

Brief Description of the Drawings

[0013] [Figure 1]It is a perspective view of an electromagnetic wave shielding structure according to a first embodiment of the present invention. [Figure 2] It is a plan view of a first modification example of a second member constituting the electromagnetic wave shielding structure. [Figure 3] It is a plan view of a second modification example of a second member constituting the electromagnetic wave shielding structure. [Figure 4] FIG. 4(A) is a plan view of a third modification example of a second member constituting the electromagnetic wave shielding structure, and FIG. 4(B) is a side view thereof. [Figure 5] It is a perspective view of an electromagnetic wave shielding structure according to a second embodiment of the present invention. [Figure 6] It is a perspective view of an electromagnetic wave shielding structure according to a third embodiment of the present invention. [Figure 7] It is a plan view of an electromagnetic wave shielding structure according to a fourth embodiment of the present invention. [Figure 8] It is a cross-sectional view of a first member according to a first example of a fifth embodiment of the present invention. [Figure 9] It is a cross-sectional view of a first member according to a second example of a fifth embodiment of the present invention. [Figure 10] It is a perspective view showing an overview of a tollgate on a toll road where an ETC is installed. [Figure 11] It is a front view of a first example of an electromagnetic wave shielding system according to a sixth embodiment of the present invention. [Figure 12] It is a front view of a second example of an electromagnetic wave shielding system according to a sixth embodiment of the present invention. [Figure 13] In an electromagnetic wave shielding system according to a seventh embodiment of the present invention, it is a schematic view seen from the side showing the positional relationship among a roadside antenna, a traveling vehicle, and a following vehicle thereof. [Figure 14] It is a schematic view seen from above similar to FIG. 13.

Embodiments for Carrying Out the Invention

[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 consists of a first member 110 made of a first material, a second member 120 made of a second material, and a grounding wire 130 for grounding the first member 110. The first component 110 has a cubic shape. The first material constituting the first component 110 is a conductor. For example, the first material is a metal, more specifically, a highly conductive metal such as gold, silver, or copper. The second component 120 is a flat plate with a constant thickness. The second material constituting the second component 120 is made of a material having a conductivity lower than that of the first material and higher corrosion resistance than that of the first material. For example, the second material may be stainless steel or titanium.

[0015] The first cubic member 110 has a first face 111 and a second face 112 located on the opposite side of the first face 111. When the electromagnetic wave shielding structure 100 is exposed to electromagnetic waves, for example, if the first surface 111 of the first member 110 is exposed to electromagnetic waves, the second member 120 is configured to completely cover the first surface 111 of the first member 110. When electromagnetic waves from an external source strike the second member 120, some of the electromagnetic waves are 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 ground wire 130. In other words, by grounding the first member 110, it is possible to prevent electromagnetic waves from leaking to the outside. As a result, external electromagnetic waves cannot pass through (penetrate) the electromagnetic wave shielding structure 100. Outwardly, it appears that the external electromagnetic waves are absorbed by the electromagnetic wave shielding structure 100 (absorption effect).

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

[0017] In this embodiment, the first member 110 is configured as a cube, but the shape of the first member 110 is arbitrary. It can be any shape. 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 to configure the second member 120 to partially cover the first surface 111. For example, in an environment where electromagnetic waves are concentrated only in a portion of the first surface 111 of the first member 110, it is possible to cover only that portion with the second member 120. In the electromagnetic wave shielding structure 100 according to this embodiment, stainless steel or titanium was given as an example of the second material constituting the second member 120. However, even if measures to prevent or reduce reflection are applied to the surface of the second member 120 (see, for example, Figures 4(A) and 4(B) described later), it is not possible to completely suppress the generation of reflected waves.

[0018] Therefore, 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. 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 ground wire 130. In this embodiment, the second member 120 is configured to be flat, but the shape of the second member 120 is not limited to a flat plate. Figure 2 is a plan view of the first modified example of the second member 120. The second member 120A in the first modified example is formed in a mesh-like structure. For example, as shown in Figure 2, the second member 120A has a mesh structure formed by holes 121 of the same diameter arranged in a matrix. By making the second component 120A a mesh structure, it is possible to reduce manufacturing costs through material reduction, reduce weight, improve wind resistance, and improve visibility (the status of the first component 110 can be visually assessed). The mesh shape is arbitrary. For example, the second member 120A may be formed in a net-like (mesh-like) shape, and the mesh shape can be selected according to the situation.

[0019] It is not necessarily required that all holes 121 have the same diameter; it is possible for multiple holes 121 to have different diameters. Furthermore, it is possible to form multiple holes 121 randomly rather than in a matrix. Furthermore, it is possible to make the first member 110, as well as the second member 120A, have the same mesh structure as the second member 120A, that is, to make the entire electromagnetic wave shielding structure 100 a mesh structure. 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 they may be different from each other. Figure 3 is a perspective view of a second modified example of the second member 120. As shown in Figure 3, the second member 120B in the second modified example is composed of two auxiliary members 120X and 120Y. The auxiliary member 120X is the same as the second member 120A shown in Figure 2. The auxiliary member 120Y has a mesh shape with multiple holes formed in a matrix, but the diameter of each hole in the auxiliary member 120Y and the distance (pitch) between adjacent holes are different from those of the auxiliary member 120X.

[0020] In other words, both auxiliary member 120X and auxiliary member 120Y have a mesh shape, but their mesh patterns are different from each other. As shown in Figure 3, the auxiliary members 120X and 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 covers 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. The most effective mesh pattern for an external electromagnetic wave varies depending on its physical properties (amplitude, wavelength, etc.) and external factors such as the angle of incidence. Therefore, by using two auxiliary members 120X and 120Y with different mesh patterns in combination, the effectiveness of shielding against various external electromagnetic waves can be improved. In this embodiment, the second member 120B is configured as consisting of two auxiliary members 120X and 120Y, but the number of auxiliary members constituting 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 shielding against various external electromagnetic waves becomes.

[0021] Figure 4(A) is a plan view of a third modified example of the second member 120, and Figure 4(B) is a side view thereof. As shown in Figures 4(A) and 4(B), in the third modified example, the second member 120C has multiple convex bodies 122 of the same shape formed in a matrix on its outer surface (the surface opposite to the surface in contact with the first member 110). Each convex body 122 has the shape of a regular square pyramid. In the second members 120, 120A, and 120B shown in Figures 1 to 3, a portion of the external electromagnetic waves are reflected. By forming a convex body 122 on the surface of the second member 120C, it becomes possible to cause diffuse reflection (scattering) of the external electromagnetic waves, thereby suppressing the propagation of energy due to reflection. The shape of the convex body 122 is not limited to a regular square pyramid. Any shape can be selected. Furthermore, not all convex bodies 122 need to be the same shape; it is possible for at least some of the convex bodies 122 to have a different shape from the others.

[0022] Furthermore, it is possible to form a concave body instead of a convex body 122, and it is also possible to form a combination of a convex body 122 and a concave body. Alternatively, instead of forming the convex body 122, the surface of the second member 120C can be made corrugated. To diffusely reflect external electromagnetic waves using surface irregularities, the height or depth of the irregularities is considered appropriate to be approximately 1 / 10 to 1 / 50 of the wavelength. For example, among external electromagnetic waves (electromagnetic waves present in the natural environment), ultraviolet light has the shortest wavelength, which is approximately 10 to 200 nm. Therefore, for example, the height or depth of the irregularities is set to approximately 2 nm to 10 nm for ultraviolet light. When forming irregularities on the first surface 111, the second surface 112 of the first member 110, 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) to diffusely reflect external electromagnetic waves, 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) Figure 5 is a perspective view of the electromagnetic wave shielding structure 100A according to the second embodiment of the present invention. In the electromagnetic wave shielding structure 100 shown in Figure 1, the second member 120 is attached to only one side (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 sides (first surface 111 and second surface 112) of the first member 110. In this way, by arranging the second member 120 on both sides 111 and 112 of the first member 110, the absorption of electromagnetic waves and resistance to the outdoor environment can be improved, 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 member 120 is attached to both sides of the first member 110, it becomes unnecessary to consider such an orientation.

[0024] (Third embodiment) Figure 6 is a perspective view of the electromagnetic wave shielding structure 100B according to the 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 shielding structure 100B also provides the same effects as the electromagnetic wave shielding structure 100 according to the first embodiment. Furthermore, a mesh-shaped electromagnetic wave shielding structure can be formed by weaving together wire-shaped electromagnetic wave shielding structures 100B. Even if the first member 110 is not flat (Figure 1) but rod-shaped or linear, it is still possible to construct an electromagnetic wave shielding structure as in this embodiment.

[0025] (Fourth embodiment) Figure 7 is a plan view of the electromagnetic wave shielding structure 100C according to the fourth embodiment of the present invention. The electromagnetic wave shielding structure 100C is, for example, an electromagnetic wave shielding structure 100 according to the first embodiment, configured as a square panel. Each of the four sides of panel 100C has a protrusion 101 and a recess 102 formed at the same position. Both the protrusion 101 and the recess 102 are cubic in shape, and the protrusion 101 can be fitted into the recess 102. By interlocking the protrusions 101 and recesses 102 on one side of panel 100C with the recesses 102 and protrusions 101 on one side of an adjacent panel 100C, these two panels 100C can be joined together. In this way, by providing protrusions 101 and recesses 102 on each side of 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 fit 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 has been 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 diffusely reflects electromagnetic waves that could not be absorbed by the first member 110. Figure 8 is a cross-sectional view of the first member 110B according to the first example of this embodiment. The first member 110B has a wave-like shape at 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 into the ground via the ground wire 130. Electromagnetic waves that are not absorbed by the first member 110B are diffusely reflected and attenuated by the wave-shaped surface of the first member 110B. In this way, by making the first member 110B a waveform shape, it is possible to effectively deal with electromagnetic waves that have passed through the second member 120.

[0027] The shape of the first member 110B is not limited to a wave shape; it can be any curved shape. Furthermore, it is not limited to a regularly curved structure like the wave shown in Figure 8, but can also be an irregularly curved structure. When selecting a first member 110B with a corrugated shape, it is preferable that the second material constituting the second member 120 be resin. If glass or metal is selected as the second material constituting the second member 120, it becomes necessary to mold the second member 120 to match the corrugated shape of the first member 110B. However, if resin is selected as the second material, it becomes possible to construct the second member 120 by coating the corrugated surface of the first member 110B with liquid resin and drying it, thereby greatly simplifying the manufacturing process of the second member 120.

[0028] Furthermore, as shown by the dashed lines in Figure 8, it is also possible to provide the second member 120 on both sides of the first member 110B. Figure 9 is a cross-sectional view of the first member 110C according to a second example of this embodiment. On the first member 110C, convex bodies 113 similar to the convex body 122 shown in Figure 4 are regularly formed on the surface that contacts the second member 120 (the first surface 111 in Figure 1). Similar to the case of the first member 110B with a waveform shape, electromagnetic waves that are not absorbed by the first member 110C are diffusely reflected and attenuated by the convex body 113 formed on the surface of the first member 110C. Similar to 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 the concave body.

[0029] Similar to the first example shown in Figure 8, it is preferable that the second material constituting the second member 120 is resin. Furthermore, as shown by the dashed line in Figure 9, a convex body 113 can also be formed on the opposite side of the first member 110C (the second side 112 in Figure 1), and this convex body 113 can be covered with a second resin member 120. As a third example, the first member 110 can also be made into a mesh structure, similar to the second member 120A (see Figure 2). By making the first member 110 a mesh structure, electromagnetic waves that were not absorbed by the first member 110 can be diffusely reflected and attenuated, similar to the case of the first member 110B which has 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 present in the natural environment), ultraviolet light has the shortest wavelength, which is approximately 10 to 200 nm. Therefore, in practice, it is possible to reflect external electromagnetic waves without forming a relatively large convex body 113 on the first surface 111 of the first member 110. Therefore, it is sufficient for the first surface 111 of the first member 110 to have irregularities with a height or depth shorter than the wavelength of external electromagnetic waves (e.g., ultraviolet rays). In other words, 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 external electromagnetic waves, it is possible to diffusely reflect the external electromagnetic waves and, as a result, attenuate them. Similar to the first example, when minute irregularities are formed on the first surface 111 of the first member 110, the second material constituting the second member 120 is preferably resin. Furthermore, it is possible to form minute irregularities on both surfaces 111 and 112 of the first member 110, and it is also possible to form minute irregularities 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-described electromagnetic wave shielding structures 100, 100A, and 100C. As mentioned above, in recent years, problems have occurred where ETC malfunctions occur at toll booths on toll roads where ETC is installed. The electromagnetic wave shielding system according to this embodiment addresses this problem. Generally speaking, ETC is a system that automatically pays tolls by communicating wirelessly between roadside antennas installed at toll gates on expressways and other toll roads and ETC onboard units installed in vehicles. Figure 10 is a perspective view showing an overview of a toll booth on a toll road where ETC is installed. For example, let's assume there is a first lane 201 and an adjacent second lane 202. Toll booths are installed for each lane. The following explanation will focus on the case of the first lane 201. The ETC system installed in the first driving lane 201 consists of a roadside antenna 210 that transmits radio waves to the ETC onboard unit installed in the vehicle, a display panel 220 that displays the toll fee, and a barrier 230 that opens and closes the first driving lane 201.

[0032] The roadside antenna 210 is mounted on a mounting bar 211 that spans the first travel lane 201, is located in the center of the first travel lane 201, and transmits radio waves to the traveling vehicle 251 from above. When a vehicle is identified via wireless communication between the roadside antenna 210 and the ETC onboard unit, the toll is displayed on the display panel 220. Once payment of the toll is complete, the barrier gate 230, which was previously closed, opens. When the vehicle 251 passes through the barrier gate 230, the barrier gate 230 closes. As mentioned above, when vehicles (especially large vehicles) pass through a lane in succession, it may be difficult to accurately determine the passage of those vehicles. The suspected causes for this are explained below.

[0033] When vehicle 251 traveling in the first lane 201 approaches the roadside antenna 210, the roadside antenna 210 detects the presence of vehicle 251 and transmits radio waves toward vehicle 251. When the ETC onboard unit installed in vehicle 251 receives the radio waves from the roadside antenna 210, the ETC onboard unit transmits ID information for identifying vehicle 251 toward the roadside antenna 210. Once payment of the toll is completed via wireless communication between the roadside antenna 210 and the ETC onboard unit, the barrier gate 230 opens. Assume that when vehicle 251 is approaching roadside antenna 210, vehicle 252 is also approaching roadside antenna 210A in the second travel lane 202, which is adjacent to the first travel lane 201. In this case, the roadside antenna 210A in the second travel lane 202 transmits radio waves to the approaching vehicle 252, similar to the roadside antenna 210. Some of the radio waves transmitted by the roadside antenna 210A are received by the ETC onboard unit in vehicle 252, but some of the radio waves that are not received by the ETC onboard unit may be reflected back by vehicle 252. If some of these reflected radio waves are received by the roadside antenna 210 in the first travel lane 201, the roadside antenna 210 will receive both the radio waves from the ETC onboard unit in vehicle 251 and the reflected radio waves from vehicle 252. As a result, the roadside antenna 210 will determine this double reception as an error and will keep the barrier gate 230 closed without opening it. Therefore, vehicle 251 will not be able 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 and 210A between two adjacent travel lanes 201 and 202. Figure 11 is a front view of a first example of the electromagnetic wave shielding system according to this embodiment. The electromagnetic wave shielding system in the first example is configured as a radio wave shielding wall 300. The radio wave shielding wall 300 stands upright between the first travel lane 201 and the second travel lane 202. By installing 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. As a result, the roadside antenna 210 can receive only the radio waves transmitted from the ETC onboard unit of the vehicle 251 traveling in the first travel lane 201, thereby preventing the aforementioned double reception and, consequently, preventing malfunctions of the ETC system.

[0035] Currently, while toll booths with ETC systems sometimes have highly electromagnetic wave-absorbing fibers attached to their walls, the effect of preventing electromagnetic wave reflection is limited to the toll booth walls. It is impossible to prevent reflected radio waves from the adjacent second lane 202 from reaching the roadside antenna 210, and therefore the problem caused by reflection from the adjacent lane remains unresolved. To completely resolve this problem, it is necessary to install a radio wave shielding wall 300. The radio wave shielding wall 300 can be installed over a length L1 (see Figure 10) from the roadside antenna 210 to the opening / closing bar 230, but it is preferable to install it within a minimum length L2 (see Figure 10) that includes the roadside antenna 210 (the length spanning both sides of the roadside antenna 210). In that case, the length of the radio wave shielding wall 300 should be the length of one vehicle, specifically the length of one large vehicle. As shown in Figure 11, it is preferable that the height of the radio wave shielding wall 300 be 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, 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. Therefore, 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. Figure 12 is a front view of a second example of the electromagnetic wave shielding system according to this embodiment. The electromagnetic wave shielding system in the second example is configured as a tunnel 350 that covers the first travel lane 201. By providing the tunnel 350, radio waves reflected from the vehicle 252 traveling in the second travel lane 202 are absorbed or reflected by the tunnel 350, similar to the case of the radio wave shielding wall 300, and do not reach the roadside antenna 210 in the first travel lane 201. As a result, the roadside antenna 210 can receive only the radio waves transmitted from the ETC onboard unit of the vehicle 251 traveling in the first travel lane 201, thereby preventing the aforementioned double reception.

[0037] The height of the tunnel 350 is set to a height that allows the roadside antenna 210 to be contained within it, as shown in Figure 12. Furthermore, the location of the tunnel 350 is set within a range of at least length L2, similar to the location of the radio wave shielding wall 300, and the length of the tunnel 350 is set to be 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 roadside antenna 210 is defined as the 5.8GHz band according to the standard (DSRC standard). As mentioned above, in order to diffusely reflect (scatter) external electromagnetic waves by the unevenness of the surface, the height or depth of the unevenness is considered appropriate to be 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 convex bodies 113 and 122 are formed on the surface of the first member 110 or the second member 120 as a radio wave shielding wall 300 or tunnel 350, or an electromagnetic wave shielding structure in which a predetermined surface roughness is given to the surface of the first member 110 or the second member 120, it is effective to set the height or depth of these unevenness 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-described electromagnetic wave shielding structures 100, 100A, and 100C. The electromagnetic wave shielding system according to the sixth embodiment described above prevents problems caused by radio waves reflected from the adjacent second travel lane 202 reaching the roadside antenna 210 of the first travel lane 201. However, there is another cause for such problems. Figure 13 is a schematic diagram viewed from the side showing the positional relationship between the roadside antenna 210, the moving vehicle 251, and the following vehicle 253, while Figure 14 is a schematic diagram viewed from above. Referring to Figure 13, a portion 311 of the radio waves 310 emitted by the roadside antenna 210 towards vehicle 251 traveling in the first lane 201 may be reflected off the body of vehicle 251 (for example, the roof or side body of vehicle 251) and reach a following vehicle 253 as reflected wave 311A. The reflected wave 311A ​​that reaches the following vehicle 253 may be reflected again off the body of the following vehicle 253, and this reflected wave 312 may reach the roadside antenna 210. Thus, even when reflected waves 312 from the following vehicle 253 reach the roadside antenna 210, a problem occurs in which the passing of a vehicle cannot be accurately determined.

[0039] The electromagnetic wave shielding system according to this embodiment addresses such problems. The electromagnetic wave shielding system according to this embodiment includes a radio wave shielding wall 360 positioned in front of the roadside antenna 210 when viewed from the direction of travel of the vehicle 251. The radio wave shielding wall 360, like the radio wave shielding wall 300 and the tunnel 350, consists of electromagnetic wave shielding structures 100, 100A, and 100C, and is in the shape of a flat plate. The roadside antenna 210 is set to emit radio waves when, for example, vehicle 251 approaches to a distance M1 of 30m. Since the speed when passing through a toll booth equipped with ETC is legally limited to 20km / h or less, the distance M2 between vehicle 251 and the following vehicle 253 can be estimated to be approximately 20m. The position of the radio wave shielding wall 360 is determined under these conditions 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 vertical length (height) H (or the position of its lower end) is set as follows: The length H of the roadside antenna 210 is set so that radio waves emitted from the roadside antenna 210 reach the vehicle 251 without being blocked by the radio wave shielding wall 360, but reflected waves 312 from a following vehicle 253 are shielded when they are heading towards the roadside antenna 210. In other words, the length H of the radio wave shielding wall 360 is determined so that, regardless of the position of the upper and lower ends of the radio wave shielding wall 360, radio waves emitted from the roadside antenna 210 reach the preceding vehicle 251, but the radio wave shielding wall 360 is located in the middle of the path of reflected waves 312 from a following vehicle 253 that is heading towards the roadside antenna 210. As shown in Figure 14, the width W of the radio wave shielding wall 360 is equal to the width of the first travel lane 201. Since the roadside antenna 210 is located in the center of the first travel lane 201, the entire roadside antenna 210 is covered by the radio wave shielding wall 360 in the horizontal direction.

[0041] As described above, the electromagnetic wave shielding system according to this embodiment can prevent reflected waves 312 from the following vehicle 253 from reaching the roadside antenna 210, thereby preventing the occurrence of problems caused by reflected waves 312 from the following vehicle 253. Furthermore, 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 applied to a wide range of applications, such as building materials for nuclear shelters, materials for protective facilities or equipment against electromagnetic pulse attacks (EMP), and covers for electronic equipment against electromagnetic interference. Electromagnetic wave shielding systems, which utilize electromagnetic wave shielding structures, can be applied not only to troubleshooting ETC (Electronic Toll Collection) systems as described above, but also to evacuation facilities against lightning strikes and other similar applications. [Explanation of Symbols]

[0043] 100 Electromagnetic wave shielding structure according to the first embodiment of the present invention 110 First component 120, 120A Second component 130 Ground wire 201 First running lane 202 Second running lane 210, 210A Roadside antenna Vehicles 251, 252, 253 300 Radio wave shielding wall 350 tunnels 360 Radio wave shielding wall

Claims

1. A first member made of a first material which is a conductor, A second member comprising a second material having a conductivity lower than that of the first material and higher corrosion resistance than that of the first material, An electromagnetic wave shielding structure comprising, The second member covers at least a portion of the surface of the first member. An electromagnetic wave shielding structure wherein at least one of the surface of the first member on the side in contact with the second member and the outer surface of the second member has irregularities formed on it for diffusely reflecting external electromagnetic waves that are to be shielded by the electromagnetic wave shielding structure, and the height or depth of the irregularities is 1 / 10 to 1 / 50 of the wavelength of the external electromagnetic waves.

2. The first member has a first surface exposed to electromagnetic waves and a second surface located on the opposite side of the first surface. The electromagnetic wave shielding structure according to claim 1, characterized in that the second member covers at least the first surface among the first and second surfaces.

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

4. The electromagnetic wave shielding structure according to claim 2, characterized in that the second member consists of at least two auxiliary mesh members having mutually different mesh patterns, and covers the first member with the auxiliary mesh members overlapped.

5. The second member has a first surface that covers the surface of the first member, and a second surface located on the opposite side of the first surface. The electromagnetic wave shielding structure according to claim 2, characterized in that the surface of the second surface has irregularities formed on it, or the second surface is formed in a corrugated shape.

6. The electromagnetic wave shielding structure according to claim 1, characterized in that the first member is rod-shaped or linear, and the second member covers the outer circumferential surface of the first member.

7. The electromagnetic wave shielding structure according to claim 1, characterized in that the first material is gold, silver, or copper.

8. The electromagnetic wave shielding structure according to claim 1, characterized in that the second material is stainless steel or titanium.

9. The electromagnetic wave shielding structure according to claim 1, characterized in that the second material does not reflect electromagnetic waves but transmits them.

10. The electromagnetic wave shielding structure according to claim 9, characterized in that the second material is glass or resin.

11. The electromagnetic wave shielding structure according to claim 1, characterized in that the first member has irregularities formed on the surface in contact with the second member, forming a mesh structure, or the surface in contact with the second member is curved.

12. The electromagnetic wave shielding structure according to claim 11, characterized in that the second material is a resin.

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

14. The electromagnetic wave shielding structure according to claim 1, wherein the electromagnetic wave shielding structure is configured as a flat panel, and each side of the panel has a protrusion and a recess formed in the same plane as the panel to enable connection with an adjacent panel.

15. An electromagnetic wave shielding system installed in a driving lane where an ETC (Electronic Toll Collection) system is installed, The electromagnetic wave shielding system includes an electromagnetic wave shielding body formed between the driving lane and a second driving lane adjacent to the driving lane. The electromagnetic wave shielding body prevents radio waves emitted from the roadside antenna installed in the second driving lane, which are reflected off vehicles traveling in the second driving lane, from reaching the roadside antenna in the driving lane. An electromagnetic wave shielding system wherein the electromagnetic wave shielding body consists of an electromagnetic wave shielding structure according to any one of claims 1 to 14.

16. The electromagnetic wave shielding system according to claim 15, characterized in that the electromagnetic wave shield has a length of at least the length of one large vehicle.

17. The electromagnetic wave shielding system according to claim 15, characterized in that the electromagnetic wave shielding body consists of a wall-like structure.

18. The electromagnetic wave shielding system according to claim 17, characterized in that the height of the wall-like structure is set higher than the height of the roadside antenna that transmits radio waves to vehicles traveling in the travel lane.

19. The electromagnetic wave shielding system according to claim 17, characterized in that the wall-like structure has a length along the driving lane that includes at least the roadside antenna of the driving lane between them.

20. The electromagnetic wave shielding system according to claim 15, characterized in that the electromagnetic wave shielding body is a tunnel-shaped structure covering the driving lane.

21. The electromagnetic wave shielding system according to claim 20, characterized in that the tunnel-like structure has a length along the travel lane that includes at least the roadside antenna of the travel lane between them.

22. An electromagnetic wave shielding system installed in a driving lane where an ETC device is installed, The electromagnetic wave shielding system includes an electromagnetic wave shielding body positioned in front of a roadside antenna installed in the driving lane, in the direction of travel of a vehicle traveling in the driving lane. The electromagnetic wave shield is positioned such that radio waves emitted from the roadside antenna reach the preceding vehicle, but some of the reflected waves from the following vehicle are located along the path toward the roadside antenna. An electromagnetic wave shielding system wherein the electromagnetic wave shielding body consists of an electromagnetic wave shielding structure according to any one of claims 1 to 14.

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