Electromagnetic wave reflecting device and electromagnetic wave reflecting fence

Abstract

The invention provides an electromagnetic wave reflecting device which can maintain electromagnetic wave reflecting performance indoors and outdoors and can be stably arranged. An electromagnetic wave reflection device is provided with: a reflection panel that reflects an electromagnetic wave in a desired frequency band selected from among frequency bands of 1-170 GHz; and a frame that holds the reflective panel, the frame having a conductive portion, the reflective panel being held by the frame such that an edge of the reflective panel is not exposed outside the frame, and at least a portion of the conductive portion of the frame being covered with a non-conductive protective member or protective coating.

Description

Technical Field

[0001] The invention relates to an electromagnetic wave reflecting device and an electromagnetic wave reflecting fence. Background Art

[0002] Due to the automation of manufacturing processes and office work, and the introduction of control and management based on AI (Artificial Intelligence), indoor base stations have been introduced in factories, workshops, offices, commercial facilities, etc. In the fifth generation (hereinafter referred to as "5G") mobile communication standard, a frequency band below 6GHz, called "sub-6", and a 28GHz band classified as a millimeter wave band are provided. In the next generation of 6G mobile communication standards, it is expected to expand to the sub-terahertz band. By using such a high-frequency band, the communication bandwidth is greatly expanded, and a large amount of data communication can be carried out with low latency. In 5G, it is expected to be applied not only to public mobile communication networks, but also to communication volume control based on IoT (Internet of Things) technology, autonomous driving, industrial IoT represented by "smart factories", etc. A structure in which an electromagnetic wave reflection device is configured along at least a portion of the production line is proposed (for example, refer to patent document 1).

[0003] Millimeter wave and sub-terahertz band radio waves are high frequencies, so they have high rectilinear propagation, short propagation distances, and large propagation losses. In indoor facilities such as factories, workshops, and commercial facilities, there are various obstacles such as equipment and structures, making it difficult to maintain high communication quality. The use of electromagnetic wave reflection devices can improve the radio wave propagation environment, but it is expected to cover a wide range of communication environments depending on the area of ​​the facility. The same requirement also exists in places where there are points where base station antennas cannot be seen (NLOS: Non-Line-Of-Sight), such as building streets, where there are many reflections from walls and roadside trees, and outdoor event venues.

[0004] Patent Document 1: International Publication No. 2021 / 199504

[0005] When an electromagnetic wave reflecting device is set up indoors or outdoors, it is hoped that equipment technicians and construction workers can simply assemble and set it according to the layout of the site. When an electromagnetic wave reflecting device is set up over a large area, it is necessary to design an electromagnetic wave reflecting device with a good reflection characteristic and a stable structure, including both a panel for electromagnetic wave reflection and a supporting body for supporting the panel. If a part of the panel protrudes from the supporting body, reflection at an angle different from the desired reflection angle may occur, and sometimes the improvement effect of the communication environment cannot be fully obtained. In addition, the supporting body of the supporting panel may rust due to the influence of moisture and salt, and the reflection direction may change, and the reduction of reflection efficiency is worrying. Summary of the invention

[0006] An object of the present invention is to provide an electromagnetic wave reflecting device that can maintain electromagnetic wave reflecting performance indoors or outdoors and can be stably installed.

[0007] In one embodiment, the electromagnetic wave reflection device comprises:

[0008] a reflective panel that reflects radio waves in a desired frequency band selected from a frequency band of 1 GHz to 170 GHz; and

[0009] A frame holding the above-mentioned reflective panel,

[0010] The frame has a conductive portion, the reflective panel is held by the frame in a manner such that an edge of the reflective panel is not exposed outside the frame, and at least a portion of the conductive portion of the frame is covered by a non-conductive protective member or protective coating.

[0011] An electromagnetic wave reflecting device is realized which can maintain electromagnetic wave reflecting performance indoors or outdoors and can be stably installed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a schematic diagram of an electromagnetic wave reflection fence formed by connecting multiple electromagnetic wave reflection devices.

[0013] Figure 2 It means along Figure 1 Figure 2 shows an example of a horizontal cross-section of a frame constructed along line AA.

[0014] Figure 3 It means the panel is Figure 2 (A) Diagram of the inserted state of the framework.

[0015] Figure 4 It means the panel is Figure 2 (B) Diagram of the inserted state of the framework.

[0016] Figure 5 is a diagram of a framework model used for simulation of reflection characteristics.

[0017] Figure 6 It is a diagram showing a calculation method of reflection characteristics.

[0018] Figure 7 It is a diagram showing the electromagnetic wave analysis space.

[0019] Figure 8 It is a diagram showing the electromagnetic wave analysis space.

[0020] Fig. 9 It is a horizontal cross-sectional view of the frame of Example 5.

[0021] Fig.10 It is a horizontal cross-sectional view of the frame of Example 6.

[0022] Fig.11 It is a horizontal cross-sectional view of the frame of Example 7.

[0023] Fig.12 It means the panel is Fig. 9 Figure 4 shows the inserted state of the frame.

[0024] Fig.13 It means the panel is Fig.10 Figure 4 shows the inserted state of the frame.

[0025] Fig.14 It is a diagram showing a modified example of the frame. DETAILED DESCRIPTION

[0026] In an embodiment, at least a portion of the conductive portion of the frame holding the reflection panel of the electromagnetic wave reflection device is protected by a non-conductive protective coating or a non-conductive protective component, and the reflection panel is maintained so that the edge of the reflection panel is not exposed outside the frame. The edge of the reflection panel refers to the end face in the thickness direction connecting the front and back surfaces of the reflection panel. By maintaining the reflection panel so that the edge of the reflection panel is not exposed outside the frame, undesired reflection in directions other than the designed reflection direction is suppressed. A non-conductive protective coating or a non-conductive protective component is provided on at least the outer surface of the conductive portion of the frame. The conductive opposing surface opposite to the edge of the reflection panel inside the frame may be covered with a protective coating or a protective component, or may be exposed without a coating. Thus, the weather resistance and reflection characteristics of the electromagnetic wave reflection device are well maintained. In the following embodiments, the same components are marked with the same reference numerals to avoid repeated descriptions.

[0027] Figure 1 Schematic diagram of an electromagnetic wave reflection fence 100 formed by connecting electromagnetic wave reflection devices 10-1, 10-2 and 10-3. Figure 1 In the embodiment, three electromagnetic wave reflection devices 10-1, 10-2 and 10-3 (hereinafter, sometimes appropriately collectively referred to as "electromagnetic wave reflection devices 10") are connected by a frame 50 to form an electromagnetic wave reflection fence 100, but the number of connected electromagnetic wave reflection devices 10 is not particularly limited. The surface on which the electromagnetic wave reflection device 10 is set is set as an XY plane, and the direction orthogonal to the XY plane is set as a Z direction. The Z direction is the height direction of the electromagnetic wave reflection fence 100, and the Y direction is the connection direction of the electromagnetic wave reflection device 10 and the width direction of the frame 50.

[0028] The electromagnetic wave reflecting devices 10-1, 10-2 and 10-3 respectively have reflecting panels 11-1, 11-2 and 11-3 (hereinafter, sometimes appropriately collectively referred to as "reflecting panels 11"). Each reflecting panel 11 reflects electromagnetic waves above 1 GHz and below 170 GHz, preferably above 1 GHz and below 100 GHz, and more preferably above 1 GHz and below 80 GHz. Each reflecting panel 11 has a conductive film designed according to the reflection mode, frequency band, etc. of the target as a reflecting film. The conductive film can also be formed by a periodic pattern, a mesh pattern, a geometric pattern, a transparent film, etc. As an example, the reflecting panel 11 has a structure of a repeated pattern of a metal mesh sandwiched by two dielectrics. The density of the metal mesh and the period of the repeated pattern are designed according to the frequency of the reflected electromagnetic wave. In this example, the metal mesh pattern is designed to reflect electromagnetic waves of 4 GHz ± 1.5 GHz, but it can also be designed to be in the range of 28 GHz ± 5 GHz.

[0029] Each of the reflective panels 11-1, 11-2, and 11-3 may have a mirror reflective surface with an incident angle and an output angle of electromagnetic waves being equal, or a non-mirror reflective surface with different incident angles and reflection angles. In addition to diffusion surfaces and scattering surfaces, non-mirror reflective surfaces also include artificial reflective surfaces designed to reflect radio waves in a desired direction, i.e., metasurfaces.

[0030] From the viewpoint of maintaining the continuity of the reflection potential, the reflection panels 11-1, 11-2, and 11-3 are preferably electrically connected to each other. As described later, in the electromagnetic wave reflection device 10 and the electromagnetic wave reflection fence 100, as long as the edge of the reflection panel 11 is not exposed outside the frame 50, a scattering cross-sectional area of ​​more than 80% of that in the case of an electromagnetic wave reflection device using a single panel without a connecting portion can be obtained. Therefore, the adjacent reflection panels 11 can be electrically connected to each other by physically contacting the frame 50, or can be held inside the frame 50 without physically contacting the frame 50.

[0031] The electromagnetic wave reflecting device 10 has a foot 56 for supporting the frame 50 in addition to the reflecting panel 11 and the frame 50. In addition to the frame 50, a top frame 57 for holding the upper end of the reflecting panel 11 and a bottom frame 58 for holding the lower end may also be used. In this case, the frame 50, the top frame 57 and the bottom frame 58 constitute a frame for holding the entire circumference of the reflecting panel 11. The frame 50 may also be called a "side frame" according to its positional relationship relative to the top frame 57 and the bottom frame 58. By setting the top frame 57 and the bottom frame 58 on the basis of the frame 50, the mechanical strength and safety of the reflecting panel 11 during transportation and assembly can be ensured. Depending on the application, the reflecting panel 11 may be held by the frame 50, the top frame 57 and the bottom frame 58 without using the foot 56 and may be set on a wall or a ceiling.

[0032] Figure 2 A horizontal cross-section view parallel to the XY plane is shown along Figure 1 The cross-sectional structure of the frame 50 may be Figure 2 The structure shown in (A) can also be Figure 2 The structure shown in (B). Figure 2 The frame 50A of (A) has a main body 500A formed of a conductive material, and a non-conductive cover 501 is provided on the outer surface of the conductive main body 500A. The cover 501 functions as a protective component of the frame 50A. The conductive main body 500A has slits 51 formed on both sides in the width direction. The slits 51 hold the side edges of the reflective panel 11. The side edges of the reflective panel 11 are along Figure 1 The edge in the height (Z) direction.

[0033] The main body 500A is formed with a cavity 52 communicating with the slit 51 and a hollow portion 55 not communicating with the slit 51 and the cavity 52. ​​The hollow portion 55 is not essential, but by providing the cavity 52 and the hollow portion 55 in the frame 50A, the frame 50A can be made lighter.

[0034] Figure 2 The frame 50B of (B) has a main body 500B formed of a conductive material, and a non-conductive cover 501 is provided on the outer surface of the conductive main body 500B. The cover 501 functions as a protective component of the frame 50B. The frame 50B has slits 51 formed on both sides of the width direction of the main body 500B. The main body 500B is formed with a cavity 52 connected to the slit 51, a groove 53 provided in the cavity 52, and a hollow portion 55 not connected to the cavity 52 and the groove 53. The groove 53 is provided at a position opposite to the slit 51 across the cavity 52. ​​The groove 53 holds the side edge of the reflection panel 11 inserted from the slit 51. By providing the cavity 52 and the hollow portion 55 in the frame 50B, the frame 50B can be made lightweight. By providing the groove 53 in the cavity 52, the reflection panel 11 is stably maintained.

[0035] Figure 3 1 is a horizontal cross-sectional view showing the state where the reflection panel 11 is inserted into the frame 50A. Figure 3 In (A), the reflective panel 11 is inserted deep into the cavity 52, and the edge 11e of the reflective panel 11 abuts against the main body 500A. The reflective panel 11 has a structure in which a conductive layer 112 such as a metal mesh is sandwiched between dielectric layers 113. The conductive layer 112 forms a reflective surface of the reflective panel 11 and is designed to reflect electromagnetic waves of a desired frequency band in a desired direction at a desired level. At the edge 11e of the reflective panel 11, the conductive layer 112 is in physical contact with the main body 500A and is electrically connected to the adjacent reflective panel 11 via the main body 500A.

[0036] exist Figure 3 In (B), as indicated by the arrow, the reflective panel 11 is offset in the direction toward the outside of the frame 50A. The edge 11e of the reflective panel 11 is separated from the main body 500A, and there is no physical or electrical contact between the conductive layer 112 of the reflective panel 11 and the conductive main body 500A, but the edge 11e of the reflective panel 11 is maintained inside the cavity 52 and is not exposed outside the frame 50A. In this state, there is no electrical connection based on physical contact between adjacent reflective panels 11, but the electric field generated on the reflective surface of the reflective panel 11 can propagate from the conductive layer 112 to the main body 500A of the frame 50A. Figure 3 In the state (B), a scattering cross-sectional area of ​​80% or more of that in the case of using a continuous panel can be obtained, and the reflection characteristics are maintained. The reason why the reflection characteristics are maintained will be described later.

[0037] For each of the reflective panels 11, the pattern of the conductive layer 112, the thickness of the dielectric layer 113, the dielectric constant, etc. are designed to obtain the desired reflective characteristics. Even when most of the frame 50A is formed of a non-conductive material such as resin, at least the surface facing the edge 11e of the inserted reflective panel 11 to the surface facing the edge of the adjacent reflective panel 11 is formed of a conductor. Figure 3 Even in the state (B), a scattering cross-sectional area of ​​80% or more of that in the case of using an electromagnetic wave reflecting device with a continuous panel can be obtained.

[0038] Figure 4 1 is a horizontal cross-sectional view showing the state where the reflection panel 11 is inserted into the frame 50B. Figure 4 In (A), the reflective panel 11 is inserted deep into the groove 53 of the cavity 52, and the edge 11e of the reflective panel 11 abuts against the body 500B. At the edge 11e of the reflective panel 11, the conductive layer 112 is in physical contact with the body 500B and is electrically connected to the adjacent reflective panel 11 via the body 500B.

[0039] exist Figure 4 In (B), as shown by the arrow, the reflective panel 11 is offset in the direction toward the outside of the frame 50B, and the edge 11e is located outside the groove 53. The conductive layer 112 of the reflective panel 11 is not in physical contact with the conductive body 500B, but the edge 11e of the reflective panel 11 is maintained inside the cavity 52 and is not exposed outside the frame 50B. The reflected electric field generated by the conductive layer 112 of the reflective panel 11 can propagate from the edge 11e to the body 500B of the frame 50B. Figure 4 In the state (B), a scattering cross-sectional area of ​​80% or more of that in the case of using a continuous panel can be obtained, and the reflection characteristics are maintained. The reason for this will be described later.

[0040] For each of the reflective panels 11, the pattern of the conductive layer 112, the thickness of the dielectric layer 113, the dielectric constant, etc. are designed to obtain the desired reflective characteristics. Even when most of the frame 50B is formed of a non-conductive material such as resin, at least the surface facing the edge 11e of the inserted reflective panel 11 to the surface facing the edge of the adjacent reflective panel 11 is formed of a conductor. Figure 4 Even in the state (B), a scattering cross-sectional area of ​​80% or more of that in the case of using an electromagnetic wave reflecting device with a continuous panel can be obtained.

[0041] The simulation was used to verify to what extent the reflection panel 11 held by the frame 50 maintains the reflection characteristics until it deviates. Figure 5 This is a model diagram of a frame 50M used for simulation of reflection characteristics. Figure 4 The frame 50B is made of the same type of aluminum as the main body 500. The overall thickness T of the main body 500 is set to 16.0 mm, and the width W is set to 60.0 mm. A polyvinyl chloride (PVC) cover 501 with a thickness of 5.0 mm and a width of 60.0 mm is installed on the outer surface of the main body 500. The PVC cover 501 is an example of a non-conductive protective component. The radius of curvature of the corner of the cover 501 is 2.0 mm. The reflective panel is inserted from the end surface 503 not covered by the cover 501.

[0042] The thickness t1 of the hollow portion 55 formed in the body 500 is 6.0 mm, and the width w4 is 20.0 mm. The thickness t2 of the cavity 52 is 11.0 mm, and the width w3 is 7.5 mm. The thickness t3 of the groove 53 provided in the cavity 52 is 5.5 mm, and the width w5 is 3.75 mm. The interval t4 of the slit 51 is 6.0 mm, and the dimension w5 in the width direction is 3.75 mm. The distance w1 from the entrance of the slit 51 to the groove 53 is 15.0 mm, and the distance w2 between the grooves 53 is 30.0 mm.

[0043] The reflective panel 11 is inserted into the deep groove of the groove 53 from the slits 51 on both sides of the main body 500. Figure 4 The state of (A) is set to be offset by 0.0 mm. From the state of offset by 0.0 mm, the reflective panel 11 is moved toward Figure 4 The reflection characteristics are calculated by shifting the direction of the arrow (outward) of (B) little by little. The reflection panel 11 used in the simulation is a structure in which a conductive layer 112 of SUS with a thickness of 1.0 mm is sandwiched and bonded by a dielectric layer 113 of polycarbonate with a thickness of 2.0 mm. The total thickness of the reflection panel 11 is 5.0 mm.

[0044] Figure 6Calculation method for indicating reflection characteristics. Reflection characteristics are indicated by the radar cross section (RCS) on the vertical axis, that is, the peak ratio of the scattering cross section. RCS is used as an indicator of the ability to reflect incident electromagnetic waves. The peak ratio is the ratio of the peak intensity of the scattering cross section when the reflective panel 11 is connected by the frame 50 to the peak intensity of the scattering cross section of a panel that is not connected by the frame 50.

[0045] The two reflective panels 11 are connected by a frame 50, thereby reducing the main peak intensity of the RCS compared to a single reflective panel that is not connected. The smaller the degree of reduction, the better the reflection characteristics. As long as the intensity of the main peak is reduced within 20%, that is, more than 80% of the scattering cross-sectional area of ​​the electromagnetic wave reflection device of one panel can be obtained, it can effectively function as an electromagnetic wave reflection device. In the evaluation, a general three-dimensional electromagnetic field simulation software is used to reflect a 3.8GHz plane wave through the electromagnetic wave reflection device, and the scattering cross-sectional area is analyzed.

[0046] Figure 7 and Figure 8 The analysis space 201 of the electromagnetic wave simulation is shown. The thickness direction of the reflection panel 11 is set to the x direction, the width direction is set to the y direction, and the height direction is set to the z direction (refer to Figure 1 ), the analysis space is represented by (dimension in the x direction) × (dimension in the y direction) × (dimension in the z direction). When the frequency of the incident electromagnetic wave is 3.8 GHz, the size of the analysis space is set to 150 mm × 500 mm × 500 mm. Figure 8 As shown, the boundary condition is a design in which an electromagnetic wave absorber 202 is arranged around the analysis space 201 .

[0047] Under the above conditions, the offset amount of the reflective panel 11 was changed from 0.0 mm, and the intensity ratio of the main peak of the scattering cross-sectional area was calculated.

[0048] <Example 1>

[0049] The reflective panel 11 is inserted into the depth of the groove 53 of the cavity 52 of the aluminum body of the frame 50 (offset 0.0mm), and an electromagnetic wave with a frequency of 3.8GHz is incident on the electromagnetic wave reflection device. The incident angle is changed from 0° to 60° at intervals of 10°, and the intensity ratio of the main peak of the scattering cross-sectional area at each incident angle is calculated. The incident angle of 0° is vertical incidence to the reflective panel 11. The reflection characteristics are evaluated using the average value of the intensity ratio of the main peak calculated at multiple incident angles. The intensity ratio of the main peak at each incident angle is shown in Table 1.

[0050] [Table 1]

[0051] Angle of incidence 0° 10° 20° 30° 40° 50° 60° Strength ratio 0.81 0.83 0.84 0.81 0.91 0.90 0.71

[0052] The average value of the intensity ratio of the main peak when the deviation is 0.0 mm is 0.83, and it can be seen that good reflection characteristics can be obtained in the structure in which a plurality of reflection panels are connected by the frame 50 .

[0053] <Example 2>

[0054] Inside the frame 50, the reflective panel 11 is offset from the state of 0.0 mm in both directions by 0.5 mm (offset by 0.5 mm), and an electromagnetic wave with a frequency of 3.8 GHz is incident. When the offset is 0.5 mm, the conductive layer 112 of the reflective panel 11 is not in physical contact with the main body 500 of the frame 50, but the edge 11e of the reflective panel 11 is located inside the groove 53, and the reflective panel 11 is reliably held by the groove 53 and the slit 51. The incident angle is changed from 0° to 60° at intervals of 10° and the intensity ratio of the main peak of the scattering cross-sectional area at each incident angle is calculated. The intensity ratio of the main peak at each incident angle is shown in Table 2.

[0055] [Table 2]

[0056] Angle of incidence 0° 10° 20° 30° 40° 50° 60° Strength ratio 0.83 0.81 0.80 0.78 0.86 0.88 0.68

[0057] The average value of the intensity ratio of the main peak when offset by 0.5 mm is 0.81. Although the average value of the intensity ratio of the main peak is slightly lower than that of Example 1, 80% or more of the main peak of the scattering cross-sectional area of ​​one panel can be obtained, and the electromagnetic wave reflecting device can be effectively functioned.

[0058] <Example 3>

[0059] Inside the frame 50, the reflective panel 11 is offset from the state of 0.0 mm in both directions by 7.5 mm (offset by 7.5 mm), and an electromagnetic wave with a frequency of 3.8 GHz is incident. When the offset is 7.5 mm, the edge 11e of the reflective panel 11 is separated from the groove 53, but is located inside the cavity 52, and the reflective panel 11 is held by the slit 51. The incident angle is changed from 0° to 60° at intervals of 10° and the intensity ratio of the main peak of the scattering cross-sectional area at each incident angle is calculated. The intensity ratio of the main peak at each incident angle is shown in Table 3.

[0060] [Table 3]

[0061] Angle of incidence 0° 10° 20° 30° 40° 50° 60° Strength ratio 0.78 0.81 0.83 0.77 0.88 0.86 0.63

[0062] The average value of the intensity ratio of the main peak when offset by 7.5 mm is 0.80. Although the average value of the intensity ratio of the main peak is further reduced compared with Example 2, 80% or more of the main peak of the scattering cross-sectional area of ​​one panel can be obtained, and the electromagnetic wave reflecting device can be effectively functioned.

[0063] <Example 4>

[0064] Inside the frame 50, the reflective panel 11 is moved from a state of being offset by 0.0 mm to Figure 4 The direction indicated by the arrow in (B) is offset by 15.0 mm (offset by 15.0 mm) to allow electromagnetic waves with a frequency of 3.8 GHz to be incident. When the offset is 15.0 mm, the position of the edge 11e of the reflective panel 11 is consistent with the end face 503 in the width direction of the frame 50M, and is not exposed to the outside of the frame 50M. The incident angle is changed from 0° to 60° at intervals of 10° and the intensity ratio of the main peak of the scattering cross-sectional area at each incident angle is calculated. The intensity ratio of the main peak at each incident angle is shown in Table 4.

[0065] [Table 4]

[0066] Angle of incidence 0° 10° 20° 30° 40° 50° 60° Strength ratio 0.80 0.80 0.80 0.77 0.88 0.89 0.68

[0067] The average value of the intensity ratio of the main peak when the offset is 15.0 mm is 0.80. By preventing the edge 11e of the reflective panel 11 from being exposed to the outside of the frame 50M, it is possible to obtain more than 80% of the main peak of the scattering cross-sectional area of ​​one panel as in Example 3. However, from the perspective of stable holding of the reflective panel 11, the edge 11e of the reflective panel 11 is preferably inserted into the slit 51. Figure 5 In the model, it is preferable to insert about 2.0 mm to 3.0 mm into the slit 51.

[0068] <Comparative Example 1>

[0069] Inside the frame 50, the reflective panel 11 is moved from a state of being offset by 0.0 mm to Figure 4 The direction indicated by the arrow in (B) is offset by 25.0 mm (offset by 25.0 mm) to allow electromagnetic waves with a frequency of 3.8 GHz to be incident. When the offset is 25.0 mm, the edge 11e of the reflective panel 11 is completely separated from the frame 50M and exposed outside the frame 50M. The incident angle is changed from 0° to 60° at intervals of 10° and the intensity ratio of the main peak of the scattering cross-sectional area at each incident angle is calculated. The intensity ratio of the main peak at each incident angle is shown in Table 5.

[0070] [Table 5]

[0071] Angle of incidence 0° 10° 20° 30° 40° 50° 60° Strength ratio 0.80 0.68 0.67 0.65 0.76 0.82 0.54

[0072] The average value of the intensity ratio of the main peak when offset by 25.0 mm is 0.70. Since the edge 11e of the reflective panel 11 is exposed to the outside of the frame 50M, the loss in the conductive layer 112 increases, and only 70% of the main peak of the scattering cross-sectional area of ​​one panel can be obtained. When the reflective panel 11 is not held by the frame 50 but is bonded to a wall, for example, good reflection characteristics can be obtained at vertical incidence and an incident angle of 50°, but the angle range that can be covered as an electromagnetic wave reflection device is limited.

[0073] <Comparative Example 2>

[0074] Inside the frame 50, the reflective panel 11 is moved from a state of being offset by 0.0 mm to Figure 4 The direction indicated by the arrow in (B) is offset by 20.0 mm (offset by 20.0 mm) to allow electromagnetic waves with a frequency of 3.8 GHz to be incident. When the offset is 25.0 mm, the edge 11e of the reflective panel 11 is completely separated from the frame 50M and exposed outside the frame 50M. The incident angle is changed from 0° to 60° at intervals of 10° and the intensity ratio of the main peak of the scattering cross-sectional area at each incident angle is calculated. The intensity ratio of the main peak at each incident angle is shown in Table 6.

[0075] [Table 6]

[0076] Angle of incidence 0° 10° 20° 30° 40° 50° 60° Strength ratio 0.80 0.73 0.73 0.70 0.81 0.86 0.60

[0077] The average value of the intensity ratio of the main peak when offset by 20.0 mm is 0.75. Compared with Comparative Example 1, the edge 11e of the reflective panel 11 is brought closer to the frame 50M, but the edge 11e is exposed to the outside of the frame 50M, thereby causing loss in the conductive layer 112, and only 75% of the main peak of the scattering cross-sectional area of ​​one panel can be obtained. When the reflective panel 11 is not held by the frame 50 but is bonded to a wall, for example, good reflection characteristics can be obtained at vertical incidence and in the range of 40° to 50°, but the angle range that can be covered as an electromagnetic wave reflection device is limited.

[0078] According to Examples 1 to 4 and Comparative Examples 1 and 2, the conductive layer 112 of the reflective panel 11 may not necessarily be in physical contact with the conductive main body 500 of the frame 50. As long as the edge 11e of the reflective panel 11 is not exposed to the outside of the frame 50, the reflective panel 11 is held on the frame 50 with the edge 11e in contact or not in contact with the opposing surface of the main body 500, and the desired reflection characteristics can be obtained. This indicates that the entire main body 500 of the frame 50 may not necessarily be formed of a conductive material. This is because, as long as the edge 11e of the reflective panel 11 is not exposed to the outside of the frame 50, even if the conductive layer 112 of the reflective panel 11 is not in contact with the conductive portion of the main body 500, the desired reflection characteristics can be obtained through the conductive portion of the main body 500.

[0079] Therefore, the reflection characteristics when a non-conductive coating is provided on a part of the surface of the frame 50 are verified. When the electromagnetic wave reflection device 10 or the electromagnetic wave reflection fence 100 is set indoors or outdoors, rust occurs on the metal surface of the frame 50 due to the influence of moisture and salt. If the non-conductive coating can be used as an anti-rust coating, the weather resistance is improved and the reflection characteristics can be well maintained. Below, the reflection characteristics of the frame with the non-conductive coating applied are measured.

[0080] <Example 5>

[0081] Fig. 9 is a horizontal cross-sectional view of a frame 50C of Example 5. The frame 50C has Figure 3 The main body 500A of the frame 50A is the same type as the conductive main body 500C. At least a portion of the surface of the conductive main body 500C is covered with a non-conductive protective coating 59 such as aluminum oxide (Al2O3). Fig. 9 In the figure, the outer surface of the main body 500C and the inner wall of the hollow part 55, the slit 51 and the cavity 52 are covered with a non-conductive protective coating 59, and the conductive opposing surface 521 inside the frame 50C opposite to the edge 11e of the reflective panel 11 is not covered with the protective coating 59.

[0082] After the reflective panel 11 is inserted into the cavity 52 until the edge 11e (see Figure 3 The reflection attenuation is measured by the S parameter method using a vector network analyzer and a free space oblique incidence measurement device until the reflection (A)) is in contact with the opposing surface 521. As the S parameter (scattering parameter), the reflection (S 11 ) relative to the transmission (S 21 The reflection attenuation of the incident electromagnetic wave to the electromagnetic wave reflection device is 0.00 dB when the incident electromagnetic wave is 4.9 GHz, and is -0.02 dB when the incident electromagnetic wave is 28.0 GHz.

[0083] <Example 6>

[0084] Fig.10 is a horizontal cross-sectional view of a frame 50D of Example 6. The frame 50D has Figure 4 The main body 500B of the frame 50B is the same type as the conductive main body 500D. At least a portion of the surface of the conductive main body 500D is covered with a non-conductive protective coating 59 such as aluminum oxide (Al2O3). Fig.10In the embodiment, the outer surface of the body 500D, the hollow portion 55, the slit 51 and the inner wall of the cavity 52 are covered with a non-conductive protective coating 59, and the bottom surface 531 and the side surface 532 of the groove 53 are not covered with the protective coating 59. The bottom surface 531 of the groove 53 is the surface facing the edge 11e of the reflective panel 11.

[0085] After the reflective panel 11 is inserted into the groove 53 until the edge 11e (see Figure 4 The reflection attenuation in the electromagnetic wave reflection device is measured by the S parameter method using a vector network analyzer and a free space oblique incidence measurement device until the reflection (A)) contacts the bottom surface 531 of the groove 53. As the S parameter (scattering parameter), the reflection (S 11 ) relative to the transmission (S 21 The reflection attenuation of the incident electromagnetic wave to the electromagnetic wave reflection device is 0.00 dB when the incident electromagnetic wave is 4.9 GHz, and is -0.01 dB when the incident electromagnetic wave is 28.0 GHz.

[0086] <Example 7>

[0087] Fig.11 FIG. 5 is a horizontal cross-sectional view of a frame 50E of Embodiment 7. The frame 50E has Figure 3 The main body 500A of the frame 50A is the same type of conductive main body 500E. All surfaces of the main body 500E in contact with the outside air are covered with a protective coating 59 of aluminum oxide (Al2O3). Fig. 9 and Fig.10 In contrast, the protective coating 59 on the surface facing the edge 11 e of the inserted reflection panel 11 is not peeled off, but the protective coating 59 is provided on the entire surface of the main body 500E.

[0088] After the reflective panel 11 is inserted into the cavity 52 until the edge 11e (see Figure 3 The reflection attenuation in the electromagnetic wave reflection device is measured by the S parameter method using a vector network analyzer and a free space oblique incidence measurement device until the main body 500E covered with the protective coating 59 is in contact with the main body 500E. As the S parameter (scattering parameter), the reflection (S 11 ) relative to the transmission (S 21 The reflection attenuation when the incident electromagnetic wave to the electromagnetic wave reflection device is 4.9 GHz is -0.05 dB of the incident electromagnetic wave, and the reflection attenuation when the incident electromagnetic wave to the electromagnetic wave reflection device is -0.10 dB.

[0089] Based on Examples 5 and 6, it can be seen that by covering the surface of the conductive body 500 other than the surface facing the edge 11e of the reflective panel 11 with the non-conductive protective coating 59, the reflection attenuation can be suppressed to a minimum and a protective effect can be obtained. According to Example 7, even when the surface facing the edge 11e of the reflective panel 11 is covered with the non-conductive protective coating 59, the increase in the reflection attenuation is small, and both the protective effect and the maintenance of the reflective characteristics can be achieved. In Examples 5, 6, and 7, the measurement is performed in a state where the reflective panel 11 is inserted until it abuts against the body 500 of the frame (the offset is zero), but as in Examples 2 to 4, when the edge 11e of the reflective panel 11 is kept in a state where it is not exposed outside the frame 50, it is estimated that good reflective characteristics can be maintained.

[0090] For example, Fig.12 As shown, even when the reflective panel 11 is inserted into the conductive body 500C to which the protective coating 59 is applied except for the facing surface 521, the reflective characteristics equivalent to those of the fifth embodiment are expected. Fig.13 As shown, even when the reflective panel 11 is inserted halfway into the conductive body 500D in which the protective coating 59 is applied to the surfaces other than the bottom surface 531 and the side surface 532 of the groove 53, the reflective characteristics equivalent to those of the sixth embodiment are expected. Alternatively, the bottom surface 531 of the groove 53 may be exposed and the side surface 532 may be covered with the protective coating 59. Fig.12 and Fig.13 In both cases, it is not necessary to cover all the inner surfaces of the frame except the surface facing the edge 11e of the reflective panel 11 with the protective coating 59. It is also possible to provide a non-conductive protective coating 59 on at least a portion of the surface of the conductive portion of the frame except the surface facing the edge 11e. For example, the inner walls of the groove 53 and the cavity 52 may not be covered with the protective coating 59, while the inner wall of the slit 51 and the outer surface of the frame may be covered with the protective coating. In addition, the inner wall of the hollow portion 55 may not necessarily be covered with the protective coating 59. Even in Fig.11 Even when the reflection panel 11 is inserted halfway into the main body 500E in the structure of , the reflection characteristics equivalent to those of Example 7 can be expected.

[0091] The present invention has been described above based on a specific embodiment, but the present invention is not limited to the above-mentioned structural example. The conductive layer 112 of the reflective panel 11 may also extend from the edge 11e to the surface of any dielectric layer 113. In this case, in particular Fig.10When the reflective panel 11 is inserted into the deep groove of the groove 53 in which the bottom surface 531 and the side surface 532 are exposed in the frame 50D, the electrical connection between the adjacent reflective panels 11 is well maintained. When the slit is coated with a protective coating, even if there is no direct electrical connection, diffuse reflection in the slit is achieved by scattering based on the edge, and as a result, the reflection angle of the electromagnetic wave reflecting device becomes a desired direction. Instead of sandwiching the conductive layer 112 between two dielectric layers 113, the conductive layer 112 may be formed on the surface of a dielectric plate and a ground layer may be formed on the back. The surface of the conductive layer 112 formed on the surface of the dielectric plate may be covered with a protective sheet such as resin.

[0092] The above-mentioned embodiments may be combined with each other. From the viewpoint of the ease of manufacturing process, the protective coating 59 may be applied to the entire surface of the frame 50, and after the protective coating 59 on the surface facing the edge 11e of the reflective panel 11 is peeled off, the non-conductive cover 501 may be bonded to the protective coating 59 covering the outer side of the frame 50. Alternatively, Fig.14 As shown in the modified example, a resin cover 501 may be provided on the outer surface of the conductive portion of the frame 50, and a resin cover 501 may be provided on the end surface 503 (refer to Figure 5 ) and the inner wall are coated with a protective coating 59 so that the opposite surface to the edge 11e of the reflective panel 1 is exposed. Fig.14 In the frame 50F shown in (A), Figure 2 (A) A protective coating 59 is applied to a portion of the inner wall of the conductive body 500F of the same shape that is not covered by the cover 501, so that the conductive facing surface 521 is exposed. Fig.14 In the frame 50G shown in (B), Figure 2 (B) A protective coating 59 is applied to a portion of the inner wall of the conductive body 500G of the same shape that is not covered by the cover 501, so that the bottom surface 531 and the side surface 532 of the conductive groove 53 are exposed. Fig.11 As shown, the protective coating 59 on the opposing surface 521 or 531 may be left without being removed. A non-conductive protective coating 59 may be applied to the conductive portion of the frame not only on the frame 50 but also on one or both of the top frame 57 and the bottom frame 58. In this case, the protective coating 59 on the conductive opposing surface facing the top edge or the bottom edge of the reflective panel 11 may be peeled off or maintained.

[0093] In the electromagnetic wave reflection fence 100 formed by connecting a plurality of electromagnetic wave reflection devices 10, two adjacent reflection panels 11 are held on the frame 50 in a state where the edge 11e is in contact with or not in contact with the conductive facing surface 521 or 531 of the frame 50. There may be a case where the flatness of the installation surface of the electromagnetic wave reflection fence 100 is not sufficient, and the reflection panel 11 may not be fully inserted into the deep part of the frame 50 depending on the installation environment, but by adopting the frame structure of the embodiment, even if the edge of the reflection panel 11 is slightly offset, as long as it is not exposed outside the frame 50, it is possible to maintain good reflection characteristics.

[0094] The size (width × height) of the reflection panel 11 of the electromagnetic wave reflection device 10 can be appropriately selected within the range of 30cm × 30cm to 3m × 3m. If the size of the reflection panel 11 becomes larger, the requirement for the stability of the installation becomes higher, but by adopting the frame structure of the embodiment, the degradation of the reflection characteristics can be suppressed and the reflection panel 11 can be stably maintained. In the case where a plurality of reflection panels 11 are connected and used as an electromagnetic wave reflection fence 100, even if the position of the edge 11e of the reflection panel 11 is slightly offset, the reflection potential can be well maintained between adjacent reflection panels. The electromagnetic wave reflection device and the electromagnetic wave reflection fence of the embodiment are also effectively used in indoor and outdoor activity facilities, facilities such as factories, production lines, offices with many electronic devices, etc.

[0095] This application claims priority based on Japanese Patent Application No. 2022-077189 filed on May 9, 2022, and includes the entire contents of the Japanese Patent Application.

[0096] Description of Reference Numerals

[0097] 10, 10-1, 10-2, 10-3...electromagnetic wave reflecting device; 11, 11-1, 11-2, 11-3...reflecting panel; 11e...edge; 112...conductive layer; 113...dielectric layer; 50, 50A, 50B, 50C, 50D, 50E...frame (side frame); 501...cover (protective component); 51...slit; 52...cavity; 521...opposing surface; 53...groove; 531...bottom surface; 532...side surface; 55...hollow portion; 56...foot; 57...top frame; 58...bottom frame; 59...protective coating; 100...electromagnetic wave reflecting fence.

Claims

1. An electromagnetic wave reflection device, characterized in that: have: a reflective panel that reflects radio waves in a desired frequency band selected from a frequency band of 1 GHz to 170 GHz; and a frame holding the reflective panel, The frame has a conductive portion, the reflective panel is held by the frame in a manner such that an edge of the reflective panel is not exposed outside the frame, and at least a portion of the conductive portion of the frame is covered by a non-conductive protective member or protective coating.

2. The electromagnetic wave reflection device according to claim 1, characterized in that: A conductive opposing surface inside the frame that is opposed to the edge is covered by the protective member or the protective coating.

3. The electromagnetic wave reflection device according to claim 1, characterized in that: The conductive opposing surface inside the frame that is opposite to the edge is not covered by the protective component or the protective coating.

4. The electromagnetic wave reflection device according to claim 1, characterized in that: The frame comprises a conductive body, a slit formed in the body and into which the reflective panel is inserted, and a cavity communicating with the slit. The outer surface of the body and the slit are covered by the protective coating.

5. The electromagnetic wave reflection device according to claim 4, characterized in that: The reflective panel is held in the slit in a state where the edge is in contact with or out of contact with the bottom surface of the cavity.

6. The electromagnetic wave reflection device according to claim 5, characterized in that: The main body has a hollow portion independent of the slit and the cavity.

7. The electromagnetic wave reflection device according to claim 1, characterized in that: The frame comprises a conductive body, a slit formed in the body and into which the reflective panel is inserted, a cavity connected to the slit, and a groove formed in the cavity, wherein the bottom surface of the groove is an opposing surface opposite to the edge, and the outer surface of the body and the slit are covered by the protective coating.

8. The electromagnetic wave reflection device according to claim 7, characterized in that: The reflection panel is held in the slit in a state in which the edge is in contact with or not in contact with the bottom surface of the groove.

9. The electromagnetic wave reflection device according to claim 8, characterized in that: The main body has a hollow portion independent of the cavity and the groove.

10. The electromagnetic wave reflection device according to claim 1, characterized in that: The frame has a conductive body and a non-conductive cover provided on an outer surface of the body.

11. The electromagnetic wave reflection device according to claim 10, characterized in that: The outer surface and a portion of the inner wall of the main body are covered by the protective coating, and the non-conductive cover is bonded to the protective coating covering the outer surface of the main body.

12. An electromagnetic wave reflecting fence, which is formed by connecting a plurality of electromagnetic wave reflecting devices according to any one of claims 1 to 11 in the width direction of the reflecting panel, The electromagnetic wave reflection fence is characterized in that: The two adjacent reflection panels are held by the frame in a state where the edges of the reflection panels are in contact with or not in contact with opposing surfaces facing each other inside the frame.

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