JP2009071317A - Unwanted radio wave suppressing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an unwanted radio wave suppressing structure which can alleviate a wind load on the foundation and can be easily installed within a limited space. <P>SOLUTION: The structure includes a surface type radio wave absorbing material installed around a road so that unwanted radio wave coming from the neighborhood of the road can be attenuated and suppressed by means of the surface type radio wave absorbing material. In the surface type radio wave absorbing material, a resistive layer is disposed in the incoming direction of the unwanted radio wave interposing an air layer with a reflective layer which reflects radio wave. One resistive layer and one air layer make a pair, and at least one such pair is provided in the absorbing material. The reflective layer and the resistive layer have air gaps through which air passes so as to reduce the wind load on the surface type radio wave absorbing material 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an unnecessary radio wave suppression structure that suppresses unnecessary radio waves flying from the vicinity of a road and improves an electromagnetic wave environment on the road.

In recent years, automatic toll collection (also referred to as ETC (Electronic Toll Collection)) systems and driving support roads (AHS (Advanced)
(Cruise-Assist Highway System). ) And other vehicle operation support systems have been developed. In these systems, narrow area communication (DSRC (Dedicated) is used for communication between roadside devices installed on roads and on-board devices mounted on vehicles using radio waves.
It is also called Short-Range Communication. ) Is used. Therefore, with the development of these systems, improvement of the electromagnetic wave environment on the road is demanded.

Therefore, especially on roads where there is a large amount of vehicle traffic, when using automatic toll collection systems or vehicle operation support systems, radio wave absorption panels such as radio wave absorption panels with radio wave absorption functions can be used to improve the electromagnetic environment on the road. It is conceivable to install a functioning body.

For example, radio wave absorption provided with a radio wave absorber for suppressing unnecessary radio waves generated during radio wave communication or sensing, such as bidirectional communication between a roadside antenna and an onboard device side antenna in an automatic toll collection system A method is shown in which a radio wave absorber, such as a panel, is attached to a road incidental facility, or a main part of the road incidental facility is formed of a radio wave absorber to suppress unnecessary radio waves and solve the above problems. . (For example, JP 2001-217645 A)
JP 2001-217645 A

However, if the radio wave absorption panel as described in Patent Document 1 is installed under a girder, it will be in a state like a wall surface when it is installed between lanes, and will receive a wind load. In general, the wind load is set to 300 kg / m 2, and a large load is applied to the foundation on which the radio wave absorption panel is installed. Therefore, an extremely heavy and huge foundation is required.

The huge foundation itself is expensive in terms of installation costs and effort, but it is limited in the space around existing facilities, for example, between lanes near toll booths where automatic toll collection systems are installed, and driving support roads. It is difficult to install huge foundations in the median strip of the city.

FIG. 16 is an explanatory diagram showing an expressway provided with a vehicle operation support system. A wall height column K is provided on the edges of the upper and lower lanes S, and an antenna A that radiates radio waves related to the vehicle operation support system is installed on the wall height column K together with a soundproof wall B. The operation of the vehicle C is supported when the radio wave R radiated from the antenna A is received by the vehicle-mounted device F mounted on the vehicle C traveling in the lane S.

The radio wave R radiated from the antenna A is strictly set so that the radio wave R having the intensity detected by the vehicle-mounted device F is not radiated outside the communication area in the lane S. However, when a large vehicle T having a curved surface enters the lane S, the radio wave R hitting the curved surface changes direction without being attenuated. If the road incidental equipment near the lane S is formed by using a radio wave reflector such as metal, the unnecessary radio wave R may be generated by the road incidental equipment. Reflection is also conceivable. When the vehicle-mounted device F of the vehicle C receives the unnecessary radio wave R1 outside the communication area, the operation support that is completely irrelevant is provided to the vehicle C, and the vehicle C may behave extremely dangerously.

In order to prevent such a problem, the road auxiliary equipment such as the wall rail K and the soundproof wall B near the antenna A is mainly formed of a radio wave absorber, or a radio wave absorber is provided at a site on the radio wave arrival side. Attaching can attenuate unnecessary radio waves, suppress reflection and transmission, and prevent problems caused by unnecessary radio waves. The road incidental equipment has a wind load calculated or is not planar and does not receive a wind load, and the wind load is not particularly regarded as a problem in providing a radio wave absorption function.

However, the unnecessary radio wave R1 passing over the median separation band G may be received by the vehicle-mounted device F of the vehicle C traveling in the oncoming lane, and the probability of occurrence of a malfunction by receiving the unnecessary radio wave R1 is Much higher than with other roadside equipment. Therefore, it is necessary to suppress unnecessary radio waves by providing a planar wave absorber on the central separation band G in a range where the unnecessary radio waves R1 can pass. However, the central separation band G has a limited space. In many cases, other road incidental facilities such as anti-glare plates are already installed, and there are many places where it is difficult to install a huge foundation considering wind load.

Accordingly, the present invention is intended to provide an unnecessary radio wave suppression structure that can reduce the load on the foundation due to wind load and can be easily provided in a limited space.

In order to solve the above problems, the present invention has the following configuration. That is, the unnecessary radio wave suppression structure according to the present invention is a structure in which a planar radio wave absorber is installed around a road, and unnecessary radio waves flying from the vicinity of the road are attenuated by the planar radio wave absorber and suppressed. The planar wave absorber is provided with a resistance layer sandwiching an air layer in the direction of arrival of unnecessary radio waves of a reflection layer that reflects radio waves, and at least one air layer and resistance layer are provided in a pair. The reflection layer and the resistance layer have a gap that allows air to pass therethrough.

According to the present invention, since the reflection layer and the resistance layer constituting the planar wave absorber have air gaps that allow air to pass therethrough, the wind passes through the air holes and the wind applied to the planar wave absorber. The load is reduced, the load on the foundation is reduced, the foundation can be made smaller, and it is easy to provide a structure that suppresses unnecessary radio waves even in a limited space.

Further, the radio wave reflection layer and / or the resistance layer is a suitable surface selected from the group consisting of a conductive grid sheet, a conductive mesh sheet, or a sheet including a conductive film and having a gap that allows air to pass therethrough. It is at least one having a resistance value.

The air layer is a layer in which an adjustment layer having a conductive pattern is disposed, and the conductive pattern is partly added to a lattice or mesh made of a dielectric. It is characterized by this.

Further, the reflective layer and / or the resistance layer is attached to a frame.

Furthermore, the thickness of the air layer is held by at least one holding material.

The planar wave absorber is characterized in that the return loss with respect to a circularly polarized wave of 5.8 GHz is 20 dB or more in a radio wave incident angle range of 0 degree to 30 degrees.

Furthermore, when the planar wave absorber is installed in the central separation zone, the light shielding angle is set to 8 to 12 degrees with respect to the oncoming vehicle distance of 50 m.

Furthermore, the planar wave absorber is characterized in that a photocatalyst containing layer is formed on the outer surface.

According to the present invention, since the reflection layer and the resistance layer constituting the planar wave absorber have a gap through which air passes, the wind passes through the gap and the wind load applied to the planar wave absorber. The load on the foundation can be reduced and the foundation can be made small, and it can be easy to provide a structure that suppresses unnecessary radio waves even in a limited space.

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 is an explanatory view showing an embodiment of a planar wave absorber in an unnecessary wave suppressing structure according to the present invention. The planar radio wave absorber 1 formed using a radio wave absorbing material has holes 11 for reducing wind pressure by punching.

Further, by forming the air holes 11, even if the planar wave absorber 1 is not transparent, the field of view and lighting from the opposite side or the opposite side with the planar wave absorber 1 interposed therebetween. It is possible to reduce the feeling of pressure on road users and to ensure safety when merging, etc., when lanes are adjacent.

Further, by punching the hole 11 by punching, the hole 11 can be easily drilled by using a punching device or the like, and the hole 11 has a circular shape or a shape close thereto. It is possible to minimize a decrease in strength with respect to the twist or the like of the radio wave absorber 1.

The holes 11 may be as shown in FIG. The planar wave absorber 1 is formed with holes 11 by extending a plurality of rows of slits at intervals in the vertical direction and then expanding the upper and lower portions of the slits in opposite directions. By forming the holes 11 by such a method, the holes 11 can be drilled without generating waste when the radio wave absorbing material is lost.

FIG. 3 shows a reference example of the planar wave absorber 1. The planar wave absorber 1 is formed into a lattice shape by combining the vertical beam 12 and the horizontal beam 13, and the air pressure is reduced by forming the air holes 11. Further, the distance a between the vertical bars 12 and the distance b between the horizontal bars 13 are set to ¼ or less of the wavelength of the radio wave to be suppressed, thereby reducing the radio wave transmitted through the air holes 11 and suppressing unnecessary radio waves. Meanwhile, the wind pressure can be reduced.

FIG. 4 is a cross-sectional view taken along the line AA in FIG. 1, showing a reference example regarding the radio wave absorbing material forming the planar radio wave absorber according to the present invention. As the radio wave absorbing material, there are cases where a synthetic resin blended with a conductive filler such as metal fiber or carbon black, ferrite, or a foamed material thereof is used alone, but as shown in FIG. It is designed to function in a state where the radio wave reflector 22 is lined on the opposite side to the radio wave arrival direction α. By backing the radio wave reflecting material 22, unnecessary radio waves are prevented from being transmitted, and unnecessary radio waves that have passed through the radio wave absorbing material 21 are reflected by the radio wave reflecting material 22 and further attenuated by the radio wave absorbing material 21, so that it is unnecessary. Radio waves are attenuated more efficiently. The radio wave reflecting material 22 is preferably formed of a metal, and becomes a laminated body lined with a metal plate, so that the radio wave absorbing material 2 can be structurally strong.

A protective member 23 may be provided on the radio wave arrival direction α side of the radio wave absorber 21. The protective member 23 is made of a dielectric and is preferably formed using a synthetic resin, glass, or the like. Further, a coating for preventing water droplet adhesion may be applied to the outer surface to prevent irregular reflection of radio waves due to water droplet adhesion.

Furthermore, the radio wave absorbing material 2 may be one in which the radio wave absorbing material 21 is disposed on both sides of the radio wave reflecting material 22 as shown in FIG. With this structure, unnecessary radio waves arriving from both directions α and β can be attenuated and suppressed by the integral radio wave absorbing material 2. In particular, in the central separation band, unnecessary radio waves often come from both sides of the central separation band, and a radio wave absorbing material that absorbs radio waves from both sides can be suitably applied.

FIG. 5 is a cross-sectional view showing another reference example of a radio wave absorbing material forming a planar radio wave absorber according to the present invention. The radio wave absorbing material 2 is formed by laminating a protective member 23, a resistance layer 25, a spacer 24, and a reflective layer 22 in order from the radio wave arrival direction α side. The resistance layer 25 is a film having a resistance film made of a metal oxide or the like, the spacer 24 is formed of a dielectric such as a synthetic resin, and the reflection layer 22 is a film having a metal thin film, a metal wire lattice, or the like. Unwanted radio waves incident from the direction α pass through the protection member 23 and are attenuated by the resistance layer 25. The radio waves that have not been attenuated pass through the spacer 24, are reflected by the reflective layer 22, and pass through the spacer portion 24 again. Thus, unnecessary radio waves are efficiently suppressed by being attenuated by the resistance layer 25.

By changing the thickness of the resistance layer 25 and the spacer 24 and the material of the spacer 24 in accordance with the wavelength of the radio wave that needs to be suppressed, the radio wave suppression efficiency can be further improved. For example, in the case of the wavelength λg of the radio wave in the dielectric, by setting the thickness c of the resistance layer 25 and the spacer 24 to about λg / 4, the radio wave impedance expecting the radio wave traveling direction from the surface of the spacer 24 on the radio wave arrival side. Is adjusted to the impedance of free space, and unnecessary radio waves are attenuated more efficiently. Further, by using the spacer 24 according to the use such as synthetic resin, glass, air, etc., it is possible to set the absorption characteristics of the radio wave absorber.

Furthermore, by making the protective member 23, the resistance layer 25, the spacer 24, and the reflective layer 22 translucent or translucent, respectively, even if the radio wave absorbing material 2 is interposed, it is possible to secure the opposite field of view and lighting. It can reduce the feeling of pressure given to road users when installed in the vicinity, and can contribute to traffic safety by seeing vehicles in adjacent lanes.

Further, as shown in FIG. 4B, by laminating the spacer 24, the resistance layer 25, and the protective member 23 on both sides of the reflective layer 22, both sides of the directions α and β are the same as those shown in FIG. Unnecessary radio waves coming from can be suppressed.

FIG. 6 is a cross-sectional view showing an embodiment of a radio wave absorbing material forming a planar radio wave absorber according to the present invention. The radio wave absorbing material 2 is provided with a resistance layer 25 sandwiching an air layer 26 in an arrival direction α of an unnecessary radio wave of a reflection layer 22 that reflects radio waves. The reflection layer 22 and the resistance layer 25 are conductive grids or conductive layers. It is formed with a sex mesh. A) is provided with one air layer 26 and one resistance layer 25, and b) is provided with two air layers 26 and two resistance layers 25. The reflection layer 22 and the resistance layer 25 have a gap M that allows air to pass therethrough, and the air that forms the air layer 26 is free to flow. 2 can be transmitted.

According to the above configuration, since the reflection layer 22 and the resistance layer 25 constituting the planar wave absorber 1 have the gap M, the wind passes through the gap M, and the planar wave absorber 1. The wind load applied to the base is reduced, the load applied to the base is reduced, the base can be made small, and a structure that suppresses unnecessary radio waves can be easily provided even in a limited space.

Further, the radio wave absorbing material 2 is formed by having a gap M even if it is not a transparent material such as a conductive lattice, a conductive mesh, or air, or a transparent material, and the gap M transmits light together with air. Therefore, it is possible to secure visibility and lighting from the opposite side or the opposite side across the electromagnetic wave absorber 1, reducing the feeling of pressure on road users, and when lanes are adjacent, Safety can be ensured.

If a plurality of pairs of air layer 26 and resistance layer 25 are provided, the thickness of the air layer 26 is appropriately set according to the incident angle of the radio wave, and the radio wave in which the radio wave traveling direction is expected from the surface on the radio wave arrival side. It is easy to match the impedance to the impedance of free space, and it is preferable because it can attenuate unwanted radio waves efficiently at a wide incident angle.

FIG. 7 shows an example of the planar shape of the conductive lattice and the conductive mesh forming the resistance layer 25 and the reflective layer 22, and the rod-like or fibrous conductor 3 is a vertical and horizontal lattice shape, and b) The slanted lattice shape, c) is a brick-stacked shape in an oblique direction, and the gap between the conductors 3 is a gap M. The planar shape of the conductive grid or the conductive mesh is not limited to these, and various patterns can be used. In any planar shape of (a) to (c), the distances a and b between the conductors 3 are preferably set to ¼ or less of the wavelength of radio waves to be suppressed, and more stable radio wave absorption characteristics and radio wave shielding characteristics. More preferably, it is 1/8 or less of the wavelength of the radio wave to be suppressed.

The dedicated or fibrous conductor 3 constituting the conductive grid or the conductive mesh is a dielectric including a conductive material, a surface of a substrate made of a dielectric, a conductive layer formed on the surface, or a metal. It may be. The conductive material may be at least one material selected from carbon, carbon black, carbon fiber, metal powder, metal fiber, and the like. The dielectric may be plastic or glass. Moreover, the glass fiber may be included. In this case, the strength of the conductive lattice or the conductive mesh can be improved. The conductive mesh may be formed using a non-woven conductor.

Further, a protective layer may be provided or coated on the surface of the dedicated or fibrous conductor 3 constituting the conductive lattice or conductive mesh, and further, a water repellent layer or a super water repellent layer may be provided on the surface. Adhesion of water droplets and snow / ice may be prevented, and a photocatalyst-containing layer or the like may be provided to prevent the formation of water droplets and to provide a self-cleaning property for contaminants.

FIG. 8 is an explanatory view showing a sheet including a conductive film forming the resistance layer 25 and the reflection layer 22 and having a gap M. FIG. In (b), the sheet forming the resistance layer 25 and the reflection layer 22 is one in which the conductor 3 is provided with a circular gap M through which air passes. B) is a cross-sectional view taken along line B in A). The conductor 3 is provided with a conductive film 31 on a base 32 and is further bonded to the conductive film 31 via an adhesive layer 34. 33 is provided.

With this structure, it is easy to form the conductive film 31 on the substrate 32, and it becomes easy to obtain a sheet having an appropriate sheet resistance value. If the protective layer 33 is provided, the conductive film 31 can be protected from corrosion, breakage, and the like by the base 32 and the protective layer (or protective film) 33. Furthermore, if the conductive film 31 is a transparent thin film, the transparency of the radio wave absorbing material can be easily improved.

The conductive film 31 may be formed as a film layer using the conductive material as described above. The substrate 32 may be formed in a sheet shape or a film shape using a metal, a synthetic resin, an inorganic material, or the like, regardless of a conductor or a dielectric, but may be various if formed using a synthetic resin. The shape and thickness can be adjusted, which is preferable. The protective layer 33 is not particularly limited as long as it is a dielectric, and a sheet, a film, or the like of a synthetic resin may be used. Further, the outer surface may be coated, or a water repellent layer, a super water repellent layer, a photocatalyst containing layer, or the like may be provided.

If the gap M is provided in an amount of 20 to 80% as described above with respect to the surface area of the conductor 3, it is preferable that both reduction of wind pressure and securing of radio wave absorption performance can be achieved. Further, it is preferable to provide a protective film M1 such as a coating film, a water repellent layer, a super water repellent layer, a photocatalyst containing layer on the inner surface of the gap M to protect the dielectric film 31 and the adhesive layer 34.

FIG. 9 is a cross-sectional view showing another embodiment of the radio wave absorbing material forming the planar radio wave absorber according to the present invention. In the radio wave absorbing material 2, an air layer 26 is provided between the reflective layer 22 and the resistance layer 25, and an adjustment layer 4 having a conductive pattern is further disposed between the air layers 26.

The conductive pattern of the adjustment layer 4 is as shown in FIG. 10, and a) to e) are front views showing the conductive patterns. The adjustment layer 4 is obtained by partially adding a conductor 42 to a lattice or mesh made of a rod-like or fiber-like dielectric 41, and a) a horizontal direction of the intersection of the vertical and horizontal lattices of the dielectric 41, and b. ) Is the vertical and horizontal directions of the intersection of the vertical and horizontal lattices of the dielectric material 41, c) is a space between rectangular portions formed by the vertical and horizontal lattices of the dielectric material 41, and a part thereof is cut away. In the diagonally lower right direction at the intersection of the lattice, e), the conductors 42 are partially added in a V shape in the diagonally lower right direction and the lateral direction of the conductors 41 arranged in both the diagonal direction and the horizontal direction. Is.

By providing such an adjustment layer 4 and forming various conductive patterns, it acts on one polarized wave or both polarized waves or circularly polarized waves to increase the efficiency of attenuating incident unnecessary radio waves and absorb radio waves. It is possible to reduce the thickness of the material and adjust the polarization characteristics of the radio wave absorption characteristics.

For example, in each conductive pattern, b) polarized waves from above, b) polarized waves from above and below, c) right circularly polarized waves from the front, and d) polarized from right diagonally up and diagonally down left. Wave, e) can increase the attenuation efficiency with respect to the left circularly polarized wave from an oblique direction.

The conductive pattern may include or include a conductive material in a dielectric, and at least one selected from a metal, a metal oxide, and a metal nitride is used to make the surface of the dielectric conductive. A thin film may be formed. Alternatively, a conductive film may be formed on the surface of the dielectric using a paint containing a conductive material. The conductive material may be at least one material selected from carbon, carbon black, carbon fiber, metal powder, metal fiber, and the like.

FIG. 11 is a sectional view showing another embodiment of the planar wave absorber according to the present invention. B) In the frame 5, the resistance layer 25 is attached at intervals in the arrival direction α of the radio wave of the reflective layer 22 to form the air layer 26, thereby absorbing the radio wave held around by the frame 5. The material 2 is formed and has radio wave absorption performance. In (b), the air layer 26 and the resistance layer 25 are provided on both sides of the reflective layer 22 so that unwanted radio waves incident on the planar wave absorber 1 from both sides of the directions α and β are attenuated. Can be made. Furthermore, the air layer 26 may be provided with an adjustment layer in which various conductive patterns as described above are formed.

The frame 5 may be formed of a synthetic resin or the like that is a dielectric, but the planar wave absorber 1 can be made of high strength by using a metal. In the case of using metal, it is preferable that the radio wave absorber 21 is attached to a part of the frame 5 where the arrival of unnecessary radio waves can be expected, so that the generation of unnecessary radio waves by the frame 5 can be prevented.

With such a structure, even if the strength of the reflective layer 22 and the resistance layer 25 is weak, the structure can be stabilized by being held by the frame body 5, and the thickness of the air layer 26 can be maintained and stabilized. Radio wave absorption performance can be obtained. Moreover, the planar electromagnetic wave absorber 1 can be made into a panel shape for convenience in installation and installation.

The reflective layer 22 and the resistance layer 25 may be attached by a method as shown in FIG. 12. A) is a front view showing an example of attachment, and B) is a cross-sectional view showing another example. In (b), the conductor 3 is inserted into and fixed to the through-holes 51 formed in the frame 5 at regular intervals, and the gap M is formed between the conductors 3 so that the reflective layer 22 (or resistance) Layer 25) is formed. In (b), the sheet of the reflective layer 22 (or the resistance layer 25) is sandwiched between the inner surface of the frame 5 and the plate 52, and the frame 5 and the plate 52 are fastened by the fastening means 53. (Or the resistance layer 25) is held by the frame 5.

Further, when the reflective layer 22 (or the resistance layer 25) is made of metal, it may be attached by welding. Moreover, you may attach using an adhesive material. It may be directly attached to the frame 5 using screws, bolts, and nuts, or a fixing means as described above may be combined.

FIG. 13 is a cross-sectional view showing still another embodiment of the planar wave absorber 1 according to the present invention. As in the embodiment shown in FIG. 11A), the air layer 26 is formed by providing the resistance layer 25 with an interval on the arrival direction α side of the unnecessary radio waves of the reflection layer 22. 26 is provided with at least one holding member 6 to maintain its thickness.

With this structure, even if at least one of the reflective layer 22 and the resistance layer 25 is a thin sheet or a highly flexible film-like material, the holding material 6 bends due to wind pressure or the like and the air layer 26 It is possible to prevent the thickness from changing and to stabilize the radio wave absorption performance.

The holding material 6 may be made of a dielectric material such as a synthetic resin or a dielectric foam material that has little influence on the transmission of radio waves, and further attenuates incident unnecessary radio waves using a material that absorbs radio waves. It is good also as what assists.

A planar wave absorber 1 formed of the radio wave absorbing material 2 is attached to a support column 102 erected from a base 101 as shown in FIG. 14, and an unnecessary radio wave suppression structure 10 is formed on the central separation band G. By installing, the unnecessary radio wave R <b> 1 passing through the central separation band G and going to the opposite lane is attenuated by the unnecessary radio wave suppression structure 10. By using the planar wave absorber 1, there is no risk of problems due to further reflection of unnecessary radio waves, such as those formed using a radio wave reflecting material such as a wire mesh.

Furthermore, it is preferable that the planar wave absorber according to the present invention has a light shielding angle of 8 to 12 degrees with respect to 50 m between the oncoming vehicles. The shading angle is a scale indicating the anti-glare effect when an anti-glare plate is installed in the central separation zone on an expressway or the like, and as shown in FIG. 15, a vehicle C1 that travels in the opposite direction across the central separation zone. And the angle θ at which the antiglare plate H blocks the light from the headlight of the vehicle C2 from being incident on the driver of the vehicle C1 when C2 is at a distance of 50 m.

The light shielding angle θ is preferably about 10 degrees with respect to the distance between the oncoming vehicles of about 50 m. When the angle is less than 10 degrees, the antiglare effect is lowered, and when the area exceeds 10 degrees, the adjacent lane side becomes difficult to see. Even if the positions of the vehicles C1 and C2 change, the antiglare plate H is provided with an appropriate interval in order to maintain the light shielding angle θ, but the planar wave absorber according to the present invention has holes. Since the holes transmit light as well as wind from the holes, by appropriately setting the size of the holes to be drilled with respect to the thickness of the planar wave absorber, When installed, it is preferable that the light shielding angle θ is 8 to 12 degrees because an excellent antiglare effect can be exhibited instead of the antiglare plate H.

Moreover, the planar wave absorber according to the present invention preferably has a photocatalyst-containing layer formed on the outer surface. Since the photocatalyst-containing layer is formed, the water adhering to the outer surface does not form water droplets but becomes a uniform and extremely thin water film, so that the deterioration of the radio wave absorption characteristics can be alleviated. Moreover, even if hydrophobic contaminants existing around the road are attached by activating the photocatalyst by irradiating ultraviolet rays and making the outer surface superhydrophilic, it can be easily washed away by rain and keep the appearance clean. it can.

Furthermore, since the planar wave absorber according to the present invention can transmit air and sound waves, if it is attached to the front surface of an existing sound absorbing plate, the sound absorbing performance can be provided without impairing the sound absorbing performance. Can do.

It is explanatory drawing which shows one Embodiment of the planar electromagnetic wave absorber concerning this invention. It is explanatory drawing which shows other embodiment of the planar electromagnetic wave absorber concerning this invention. It is explanatory drawing which shows the reference example of the planar electromagnetic wave absorber concerning this invention. It is sectional drawing which shows the reference example of the electromagnetic wave absorption material which forms the planar electromagnetic wave absorber concerning this invention. It is sectional drawing which shows the other reference example of the electromagnetic wave absorption material which forms the planar electromagnetic wave absorber concerning this invention. It is sectional drawing which shows one Embodiment of the electromagnetic wave absorption material which forms the planar electromagnetic wave absorber concerning this invention. It is a front view which shows the example of the electroconductive grating | lattice or electroconductive mesh used for a reflection layer and a resistance layer. It is explanatory drawing which shows the example of the sheet | seat containing the electroconductive film used for a reflection layer and a resistance layer. It is sectional drawing which shows other embodiment of the electromagnetic wave absorption material which forms the planar electromagnetic wave absorber concerning this invention. It is a front view which shows the example of the conductive pattern of an adjustment layer. It is sectional drawing which shows other embodiment of the planar electromagnetic wave absorber concerning this invention. It is explanatory drawing which shows an example of attachment of the reflective layer in the planar electromagnetic wave absorber concerning this invention, and a resistance layer. It is sectional drawing which shows other embodiment of the planar electromagnetic wave absorber concerning this invention. It is explanatory drawing which shows one Embodiment of the unnecessary electromagnetic wave suppression structure concerning this invention. It is a top view explaining the light-shielding angle concerning this invention. It is explanatory drawing which shows the road where the vehicle operation assistance system to which this invention is applied was provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Planar wave absorber 11 Hole 2 Radio wave absorber 21 Radio wave absorber 22 Reflective layer 25 Resistance layer 26 Air layer 3 Conductor 4 Adjustment layer 5 Frame body 6 Holding material 10 Unwanted radio wave suppression structure M Air gap A Antenna B Soundproof Wall K Wall height column G Median separation band R Radio wave C Vehicle F On-board unit T Curved vehicle R1 Unnecessary radio wave θ Shading angle

Claims (8)

A planar wave absorber is installed around the road, and unnecessary radio waves flying from the vicinity of the road are attenuated by the planar wave absorber to suppress the radio wave. A reflecting layer is provided with an air layer sandwiched in the direction of arrival of unwanted radio waves of the reflecting layer, and at least one pair of air layer and resistance layer is provided, and the reflecting layer and the resistance layer transmit air. An unnecessary radio wave suppression structure characterized by having an air gap. The radio wave reflection layer and / or the resistance layer has at least an appropriate sheet resistance value selected from the group consisting of a conductive grid sheet, a conductive mesh sheet, or a sheet including a conductive film and having a gap. The unnecessary radio wave suppression structure according to claim 1, wherein the number is one. The air layer is provided with an adjustment layer having a conductive pattern, and the conductive pattern is partly added to a lattice or mesh made of a dielectric. Item 3. An unnecessary radio wave suppression structure according to Item 1 or 2. The unnecessary radio wave suppression structure according to claim 1, wherein the reflective layer and / or the resistance layer is attached to a frame. The unnecessary radio wave suppression structure according to claim 1, wherein the air layer has a thickness held by at least one holding material. The planar wave absorber has a return loss of 20 dB or more with respect to a circularly polarized wave of 5.8 GHz in a radio wave incident angle range of 0 degrees to 30 degrees. Undesired radio wave suppression structure described. The planar electromagnetic wave absorber has a light shielding angle of 8 to 12 degrees with respect to an oncoming vehicle distance of 50 m when installed in a central separation zone. Unnecessary radio wave suppression structure. The unnecessary electromagnetic wave suppression structure according to any one of claims 1 to 7, wherein the planar wave absorber has a photocatalyst-containing layer formed on an outer surface thereof.

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