JP2009238852A - Frame body of radiowave absorber, and construction method of radiowave absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a frame body of a radiowave absorber capable of satisfying required performance such as a dynamic characteristic, radiowave performance and a perspective property; and to provide a construction method of a radiowave absorber. <P>SOLUTION: The frame body 30 of a radiowave absorber 10 is composed of a base part of a shape corresponding to the outline of the radiowave absorber 10, and a plurality of cross-sectionally L-shaped claw parts 36 formed at predetermined intervals on an edge part of the base part on a radiowave entering surface side, and abutting on an edge part of the radiowave absorber 10 to support the radiowave absorber 10. The length (a) of the claw part 36 is set to satisfy a≤2λ with respect to a radio wavelength λ; the width (b) of the claw part is set to satisfy b≤15 mm; and a claw rate (c) (a/(a+clearance length d of an adjacent claw part)) is set to satisfy c≤60%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a frame for a radio wave absorber and a method for constructing the radio wave absorber, and more particularly to a frame for supporting a radio wave absorber for absorbing unwanted radio waves and a method for constructing the radio wave absorber.

  In recent years, as one of ITS (Intelligent Transport Systems), ETC (Electronic Toll Collection) using DSRC (Dedicated Short Range Communications) has been very popular. It's being used. Around this ETC antenna facility, radio wave absorbers are often installed in various structures in order to prevent system malfunction caused by radio wave multiple reflection between the antennas. In other words, DSRC uses 5.8 GHz radio waves, but a radio wave absorber is installed around the system to absorb unnecessary radio waves for the purpose of reducing malfunction of the equipment due to unnecessary radio waves caused by irregular reflection of the radio waves. Has been.

  As the radio wave absorber, those using a vinylidene chloride synthetic fiber as in Patent Document 1, those using a carbon-containing foam as in Patent Document 2, and polycarbonate multilayer materials as in Patent Documents 3 and 4 were used. Things are known.

  Synthetic fibers and foamed absorbers can be placed in the case as in Patent Documents 2, 5, 6, and 7 to prevent deterioration due to ultraviolet rays and prevent water from entering, It is often used by attaching. Further, as shown in FIGS. 6 and 8 of Patent Document 1, and as shown in FIG. 5 of Patent Document 2, a mounting bracket for installation on the structure is attached to the case.

On the other hand, in the polycarbonate multilayer material, as shown in FIG. 10 of Patent Document 4, holes are made in the polycarbonate multilayer material and fixed to the structure with bolts, or a panel is formed with a frame material such as metal or FRP. As described in Patent Document 8, a construction method of dropping into an H steel support is performed.
Japanese Patent No. 3359630 Japanese Patent No. 3288999 Japanese Patent No. 3993486 JP 2003-289220 A Japanese Patent No. 3802353 JP 2003-41523 A, Japanese Patent No. 3359630 “Development of transparent electromagnetic wave absorber for ETC” Mitsubishi Electric Industrial Time Report No. 101 P53, fig. 12

  However, in many cases, synthetic fibers and foamed absorbers are put in a case and a mounting mechanism is provided on the case. However, a highly durable radio wave absorber (for example, a glass absorber) has a case. There is a disadvantage that it is unnecessary and use of the case leads to an increase in cost.

  In addition, when a relatively heavy material such as glass or polycarbonate is put in a case, there is a problem that structural instability remains when it is installed horizontally on a toll booth. Since the case is required to have radio wave permeability, it is known in Patent Document 5 that a thin material having a low dielectric constant is used, and is not suitable for holding a heavy material.

  Further, in the case of the bolt type in the polycarbonate multilayer material, there has been a problem of deterioration of the resistance film due to water intrusion from the hole. In paragraph [0044] of Patent Document 4, it is recommended to install a sealing material on the end face of the through hole in order to prevent deterioration of the film. Further, when the radio wave absorber is made of glass, there is a problem that it is difficult to make a hole and the cost is increased.

  Furthermore, in the case of the frame drop type, there is reflection of the frame itself on the radio wave incident surface. In particular, when the radio wave absorber is increased in size, the frame body is also increased in size, so that the radio wave absorption performance is deteriorated. In particular, in order to improve the transparency, there has been a demand for a relative reduction in the area of the frame by increasing the size of the transparent wave absorber.

  The radio wave absorber described in paragraphs [0030] and [0034] of Patent Document 7 has a problem that the performance of the absorber may be deteriorated because the metal frame is exposed on a relatively large area. there were.

  On the other hand, a glass wave absorber has been proposed. Unlike the fiber and foam absorbers, this radio wave absorber has high rigidity and high durability, so it can be used without putting a conductive film in the case or attaching a protective material to the front. is there. In addition, it has excellent performance in terms of durability, scratch resistance and the like as compared with a polycarbonate absorbent body having high rigidity.

  However, a simple construction method for road structures and a reliable construction method that does not impair various performances have not been found. That is, the glass wave absorber is because it is necessary to consider the difficulty of drilling and the concentration of stress on that portion when drilling. In this case, it is conceivable to install a glass wave absorber on the structure through a frame such as a frame, but the mechanical characteristics, radio wave performance to minimize radio wave reflection from the frame, transparency, etc. No frame body that satisfies the required performance has been found.

  The present invention has been made in view of such circumstances, and provides a frame for a radio wave absorber capable of satisfying necessary performance such as mechanical characteristics, radio wave performance, and transparency, and a method for constructing the radio wave absorber. The purpose is to do.

  In order to achieve the above object, the present invention provides a radio wave absorber frame supporting a radio wave absorber, wherein the base portion of the frame body is disposed at a peripheral portion of a surface of the radio wave absorber where no radio wave is incident; An L-shaped cross-section that is provided at a predetermined interval from the base portion of the frame body to the edge on the radio wave incident surface side through the side surface of the radio wave absorber and supports the radio wave absorber by contacting the edge of the radio wave absorber. A length a of the claw portion is a ≦ 2λ with respect to the electric wavelength λ, a width b of the claw portion is b ≦ 15 mm, and a claw rate c (a / ( a + The gap length d) between adjacent claws is c ≦ 60% to provide a radio wave absorber frame.

  Further, according to the present invention, when the frame of the radio wave absorber is used in an ETC facility, it is preferable that a ≦ 104 mm is set.

  Furthermore, according to the present invention, the frame is preferably made of metal.

  Furthermore, according to the present invention, the radio wave absorber is preferably made of glass.

  In order to achieve the object, the present invention attaches the radio wave absorber frame according to any one of claims 1 to 4 to the radio wave absorber at a radio wave absorber manufacturing factory, and the frame is attached. A method for constructing a radio wave absorber is provided, wherein the radio wave absorber is conveyed to a construction site, and the radio wave absorber is fixed to a structure constructed at the construction site via the frame.

  According to the frame of the radio wave absorber according to the present invention, since the main body of the frame body is a frame body, it has strength that contributes to wind pressure resistance, and the claw portion that supports the edge of the radio wave absorber has a frame. Since the body is provided at predetermined intervals, there is an effect that the radio wave absorption performance is not deteriorated while maintaining the strength. Moreover, since the nail | claw part is formed in the cross-sectional L-shape, ie, the lower part of the frame is cut out, draining becomes unnecessary. When drainage is no longer necessary, when laminated glass is applied as a radio wave absorber, there is an effect of reducing deterioration of the resistive film and conductive film sandwiched between the glass plates, and the resistive film and conductive film are deteriorated by moisture. The cause of lowering the durability of the body can be eliminated.

  Moreover, since the strength of the frame body is increased by making the frame body made of metal, the frame body is suitable as a frame body of a large radio wave absorber.

  Furthermore, when the radio wave absorber is a transparent member made of glass or the like, the area occupied by the frame body is smaller than the area of the radio wave absorber when the radio wave absorber is viewed from the front. It becomes an absorber.

  Furthermore, when the radio wave absorber is made of glass, the frame body is attached in advance at a glass manufacturing factory, thereby preventing breakage during conveyance of the radio wave absorber and improving workability at a construction site. Further, a relatively heavy material can be held horizontally on the ceiling without adversely affecting radio waves and without worrying about the structure.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments will be described below by taking ETC as an example of a radio wave absorber frame and a radio wave absorber construction method according to the present invention in accordance with the attached drawings.

  FIG. 1 is a cross-sectional view of a radio wave absorber 10 supported by a radio wave absorber frame according to an embodiment. FIG. 2 shows an outline of the ETC facility. On the ceiling surface of the canopy 13 and the roadside antenna structure (gantry) 12, a radio wave absorber 10 supported by a radio wave absorber frame is installed. ing. Note that the ETC facility where the radio wave absorber 10 is installed is not limited to the ceiling surface of the roadside antenna structure 12 and the canopy 13, but can also be installed in an ETC facility such as a transparent partition wall of a toll gate island.

  As shown in FIG. 1, the radio wave absorber 10 is a laminated glass configured by sandwiching an intermediate film 14, which is a resin sheet made of PVB or EVA, between two glass plates 16 and 18. Here, the glass plate 16 is a glass plate on the radio wave incident side, and a conductive film 20 having a predetermined resistance value is formed on a contact surface of the glass plate 16 with the intermediate film 14, so that the glass plate 18 is in contact with the intermediate film 14. A conductive film 22 having a predetermined resistance value is formed on the surface.

  The sheet resistance value of the conductive film 20 is set to be larger than the sheet resistance value of the conductive film 22, and radio waves to be absorbed are transmitted through the conductive film 20, reflected by the conductive film 22, and canceled by the reflected radio waves. It is configured.

These conductive films 20 and 22 have transparency and are composed mainly of one or more metal oxides selected from the group consisting of Sn, In, and Zn. For example, F-doped SnO ₂ (here, (Also simply referred to as tin oxide), antimony-doped SnO ₂ , Sn-doped In ₂ O ₃ (ITO), aluminum-doped ZnO, gallium-doped ZnO, and the like. In the embodiment, transparent tin oxide (SnO ₂ ) is coated on the glass surface by a CVD method.

  In the method of manufacturing the radio wave absorber 10, the intermediate film 14 is sandwiched between two glass plates 16 and 18 coated with tin oxide conductive films 20 and 22 by a CVD method and heated to a predetermined temperature in an autoclave. At the same time, it is manufactured by pressing at a predetermined pressure. This manufacturing method is basically the same as the manufacturing method of laminated glass.

  As the intermediate film 14 which is a resin sheet, a PVB, EVA film or the like used for laminated glass for construction is used. When the glass edge is exposed, it is suitable to use an EVA film with little influence of water.

  FIG. 3A shows a column (structure) 32, 32 constructed in an ETC facility with the radio wave absorber 10 supported by the frame 30 of the embodiment, and bolts (not shown) via the frame 30. ) Is a front view installed. 3B is a cross-sectional view taken along a line 1-1 in FIG. 3A, and FIG. 3C is a cross-sectional view taken along a line 2-2 in FIG. Further, FIG. 3D is an enlarged view of a main part of FIG.

  The radio wave absorber 10 shown in FIG. 3A has a frame 30 attached in advance at a laminated glass manufacturing plant that is a manufacturing plant of the radio wave absorber 10. Thereby, the breakage prevention at the time of conveyance of the electromagnetic wave absorber 10 with the frame 30 and the workability in a construction site improve.

  The frame body 30 of the radio wave absorber 10 is provided at a predetermined interval between a metal base portion having a shape corresponding to the outline of the radio wave absorber 10 and an edge portion of the base portion on the radio wave incident surface side. Are made up of a plurality of claw portions 36, 36... Having an L-shaped cross section for supporting the radio wave absorber 10. The base portion and the claw portion 36 may be manufactured integrally, but when both are made of metal, they may be joined by welding or the like.

  As shown in FIG. 4, the claw portions 36 of the frame body 30 are provided with a predetermined interval. In other words, since the claw portion 36 is cut out on the surface other than the surface on which the claw portion 36 of the radio wave absorber 10 contacts, drainage of the radio wave absorber 10 is not necessary. When drainage is not required, the radio wave absorber 10 made of laminated glass has an effect of reducing deterioration of the conductive films 20 and 22 sandwiched between the glass plates, and the radio wave absorber 10 that the conductive films 20 and 22 deteriorate due to moisture. The cause of lowering the durability can be eliminated.

  The radio wave absorber 10 supported by the claw part 36 has a claw part 36 within a claw length range a of the claw part 36 (see FIG. 3D) via a setting block 38 as shown in FIG. The frame body 30 is supported by the gasket 40 disposed in the gap between the claw portion 36 and the radio wave absorber 10 and the gasket 42 disposed in the gap between the base portion and the radio wave absorber 10. Close contact. That is, the positional relationship between the radio wave absorber 10 and the frame 30 in a range position where the claw portion 36 does not exist is a positional relationship in which the base portion is separated from the radio wave absorber 10 as shown in FIG.

  3D, the length a of the claw portion 36 of the frame 30 is set to a ≦ 2λ (104 mm) with respect to the electric wavelength λ, and the width b of the claw portion 36 is b. ≦ 15 mm is set, and the claw rate c (a / (a + gap length d between adjacent claw portions 36)) is set to c ≦ 60%. When this frame 30 is used for ETC equipment, it is set to 2λ = 104 mm, that is, a ≦ 104 mm. Furthermore, the length a of the claw portion 36 is preferably 1.5λ (78 mm) and the claw rate c is preferably 50% from the viewpoint of mechanical characteristics and radio wave performance.

  Hereinafter, the Example of the frame 30 of the electromagnetic wave absorber 10 based on experiment and the comparative example are demonstrated.

<Example>
The following experiment confirmed that among the effects of the invention, “does not reduce radio wave absorption performance”.

  An outline of the experimental apparatus is shown in FIG. In the experimental apparatus 44 shown in the figure, circularly polarized horn antennas 46 and 46 are installed on an arch 46 having a radius of about 2 m. The measurement system including the antennas 46 and 46 is in an anechoic box 48 made of a radio wave absorber, and the installation base 52 of the test body 50 is also made of an absorber and a foamed polystyrene having little reflection.

  Using the metal reflector as a reference, the time domain function of the vector network analyzer was used, and the radio wave absorption performance at 5.8 GHz was obtained with the influence of unnecessary propagation waves eliminated. Further, as shown in FIG. 6, the incident angle Φ with respect to the radio wave absorber is set to 4, 20, 45, and 55 degrees.

  In actual use, since various types of radio wave incidence can be considered for the radio wave absorber, experiments were performed with three types of patterns shown in FIGS. 7A, 7B, and 7C to confirm the performance. For example, FIG. 7A shows a configuration in which a plurality of radio wave absorbers (four radio wave absorbers of 500 mm × 500 mm) are combined, and the radio wave is generated in a portion A where the corners of the base portion 34. Is assumed to be irradiated. 7 (b) and 7 (c) are also evaluations in which a plurality of radio wave absorbers 10 and 10 are combined. FIG. 7 (b) is a base portion of adjacent radio wave absorbers 10 and 10 and a central portion of 34. It is assumed that A is irradiated with radio waves. FIG. 7C assumes a case where radio waves are applied to the central portion A of the radio wave absorber 10. In addition, the clearance gap between the electromagnetic wave absorbers 10 and 10 shown in these figures was 10 mm.

  As a performance criterion, Type-B of JH specifications (formerly Japan Highway Public Corporation. ETC countermeasure construction method first edition. Ver.1.0 (00/10/17) .2000) shown in FIG. 8 was adopted.

  Further, the table of FIG. 9 shows the specifications of the examples and comparative examples, the table of FIG. 10 shows a list of results, and FIGS. 11A, 11B, and 11C show representative examples of the results.

  In both the comparative example and the example, a glass radio wave absorber (thickness 9 mm) was used. Comparative Examples 1 to 5 are general C-shaped channel-shaped frames in which the claw portions are not processed. As the frame body, SUS304 and FRP material were used. As the FRP, a continuous pultrusion molding having excellent strength characteristics was adopted. The thicknesses of SUS304 and FRP were set to 2 mm and 6 mm, respectively, due to structural requirements.

  Examples 1 and 2 and Comparative Example 5 are frame bodies having claw portions using SUS304.

  Glass is held on the frames used in Comparative Examples 1 to 5 and Examples 1 and 2 using a setting block 38 and gasket materials 40 and 42 as shown in FIG. The groove width of the claw portion is 23 mm, and the gaskets 40 and 42 made of EPDM are used so that the glass comes to the center of the groove. The setting block 38 was made of chloroprene rubber having a thickness of 3 mm.

  As shown in FIGS. 10, 11 (A), and (B), Examples 1 and 2 showed almost the same performance as the performance of a single glass absorber that does not use a frame as a reference example. Moreover, it turned out that the performances of Comparative Examples 2 to 4 using a frame having no nail part and Comparative Example 5 having a nail ratio exceeding 60% are deteriorated.

  Further, depending on how the claw portion is processed, the frame body may or may not be visible when the base portion behind the glass is seen from the direction of radio wave incidence as shown in FIG. Although not shown in the chart, in the case of Examples 1 and 2, it was found that both specifications satisfy JIS specifications.

  In the embodiment, laminated glass is used as the radio wave absorber. However, the present invention is not limited to this, and opaque and rigid glass or resin can also be applied. Further, the frame body may be made of FRP.

Sectional drawing of the electromagnetic wave absorber which concerns on embodiment Schematic structure diagram of ETC facility The figure which shows the structure of the electromagnetic wave absorber supported by the frame of embodiment The principal part perspective view of the electromagnetic wave absorber supported by the frame of embodiment Outline diagram of experimental equipment Figure used to explain the incident angle of radio waves Explanatory drawing which showed the electromagnetic wave absorber of three kinds of patterns carried out by experiment Table of JH spec Type-B performance standard values Table illustrating the specifications of the examples and comparative examples Table showing the list of experimental results Table showing typical examples of experimental results

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Radio wave absorber, 12 ... Roadside antenna structure, 13 ... Canopy, 14 ... Intermediate film, 16 ... Glass plate, 18 ... Glass plate, 20 ... Conductive film, 22 ... Conductive film, 30 ... Frame, 32 ... Column , 34 ... Base part, 36 ... Claw part, 38 ... Setting block, 40 ... Gasket, 42 ... Gasket, 44 ... Experimental apparatus, 46 ... Antenna, 48 ... Anechoic box, 50 ... Specimen, 52 ... Installation stand

Claims (5)

In the frame of the radio wave absorber that supports the radio wave absorber,
A base portion of a frame body installed at a peripheral portion of a surface where no radio wave is incident on the radio wave absorber;
An L-shaped cross section that is provided at a predetermined interval from the base portion of the frame body through the side surface of the radio wave absorber to the edge portion on the radio wave incident surface side and supports the radio wave absorber by contacting the edge portion of the radio wave absorber. Consisting of a plurality of nails,
The length a of the claw is a ≦ 2λ with respect to the electric wavelength λ,
The width b of the claw is b ≦ 15 mm,
A frame body of a radio wave absorber, wherein a claw rate c (a / (a + gap length d between adjacent claw portions)) is c ≦ 60%.   The radio wave absorber frame according to claim 1, wherein a ≦ 104 mm is set when the radio wave absorber frame is used in an ETC facility.   The radio wave absorber frame according to claim 1, wherein the frame is made of metal.   The radio wave absorber frame according to claim 1, wherein the radio wave absorber is made of glass.   The radio wave absorber frame according to any one of claims 1 to 4 is attached to the radio wave absorber at a radio wave absorber manufacturing factory, and the radio wave absorber to which the frame is attached is transported to a construction site, A method for constructing a radio wave absorber, comprising fixing the radio wave absorber to a structure constructed at the construction site via the frame.

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