Wireless transmission system

Abstract

The present application provides a wireless transmission system that takes into account both improvement of a radio wave propagation environment and suppression of leakage of radio waves to unnecessary spaces. The wireless transmission system includes: a plurality of electromagnetic wave reflection devices provided on both sides of a passage in a traveling direction of the passage and reflecting radio waves of a prescribed frequency band selected from a range of 1 MHz or more and 300 GHz or less; and a leaky coaxial cable disposed in an area surrounded by the plurality of electromagnetic wave reflection devices provided on both sides of the passage and a ground surface of the passage and connected to a base station.

Description

Technical Field

[0001] This disclosure relates to wireless transmission systems. Background Technology

[0002] Conventionally, there exists a wireless transmission system comprising: a base station for transmitting and receiving radio waves in a desired frequency band selected from 1 GHz to 300 GHz; and an electromagnetic wave reflecting device disposed along at least a portion of a production line equipped with production equipment for transmitting and receiving the radio waves, and having a reflective surface for reflecting the radio waves (for example, see Patent Document 1).

[0003] Patent Document 1: International Publication No. 2021 / 199504

[0004] However, depending on the environment in which the wireless transmission system is set up, sometimes the location for configuring the base station is limited, making it impossible to ensure a good positional relationship between the base station and the electromagnetic wave reflecting device. In such cases, blind spots cannot be reduced, and improvements in radio wave propagation may be insufficient. Furthermore, to avoid interference with other commercial radio waves, it is necessary to suppress radio wave leakage beyond the desired area. Summary of the Invention

[0005] Therefore, the purpose of this disclosure is to provide a wireless transmission system that takes into account both the improvement of the radio wave propagation environment and the suppression of radio wave leakage outside the necessary space.

[0006] The wireless transmission system of this disclosure includes: a plurality of electromagnetic wave reflecting devices disposed on both sides of the passage along the direction of travel of the passage, and reflecting radio waves of a predetermined frequency band selected from a range of 1 MHz to 300 GHz; and a leaky coaxial cable disposed in an area surrounded by the plurality of electromagnetic wave reflecting devices disposed on both sides of the passage and the ground of the passage, and connected to a base station.

[0007] This disclosure provides a wireless transmission system that balances improvements in the radio wave propagation environment with suppression of radio wave leakage outside the necessary space. Attached Figure Description

[0008] Figure 1A This is a diagram illustrating an example of a path 32 of a wireless transmission system 1 configured with an embodiment.

[0009] Figure 1B This is a diagram illustrating an example of the structure of a leaky coaxial cable 80.

[0010] Figure 2A This is a diagram illustrating an example of the structure of an electromagnetic wave reflecting fence 100A.

[0011] Figure 2BThis is a diagram illustrating an example of a production line 35 in a factory equipped with a wireless transmission system 1 according to an embodiment.

[0012] Figure 3 This is a diagram showing an example of the layer structure of the reflective panel 10.

[0013] Figure 4 This is a diagram illustrating an example of the structure of a unit cell 20 of a conductive pattern 15 composed of a hollow pattern 151. Detailed Implementation

[0014] The following describes embodiments of the wireless transmission system using the present disclosure. Hereinafter, the same reference numerals will be used to refer to the same elements, and repeated descriptions will sometimes be omitted.

[0015] The following explanation uses the XYZ coordinate system. The direction parallel to the X-axis (X direction), the direction parallel to the Y-axis (Y direction), and the direction parallel to the Z-axis (Z direction) are orthogonal to each other. For ease of explanation, the -Z direction side will sometimes be referred to as the lower side or down, and the +Z direction side as the upper side or up. Top view refers to observation from the XY plane. Furthermore, to facilitate understanding of the structure, the length, thickness, etc., of each part will sometimes be exaggerated. The use of terms such as parallel, right angle, orthogonal, horizontal, vertical, and up / down allows for slight deviations without impairing the effectiveness of the implementation.

[0016] In the implementation, electromagnetic wave reflecting devices and leaky coaxial cables are used in wireless transmission systems used indoors and outdoors to reduce blind spots. In this specification, a "blind spot" refers to an area where the received power is reduced by more than 10 dB compared to the surrounding unobstructed receiving environment due to the influence of obstructions. Generally, electromagnetic waves below 3 THz are called radio waves, but in this specification, the communication waves transmitted from the base station are referred to as "radio waves," and electromagnetic waves are generally referred to as "electromagnetic waves."

[0017] Dead zones encompass not only two-dimensional areas but also three-dimensional space. If production equipment, sensors, or mobile communication terminals with wireless communication capabilities are located in dead zones, it becomes difficult for them to transmit and receive signals with the base station. Therefore, dead zones can be reduced and the electromagnetic environment improved by incorporating electromagnetic wave reflection devices and leaky coaxial cables.

[0018] <Implementation Method>

[0019] <Outdoor Wireless Transmission System 1>

[0020] Figure 1A This is a diagram illustrating an example of a path 32 of a wireless transmission system 1 configured with an embodiment. As an example, in... Figure 1AThe wireless transmission system 1 is shown as being configured outdoors. Road 32 is an example of a passageway, such as a highway. Here, the configuration of the wireless transmission system 1 on road 32 is described as an example, but the wireless transmission system 1 can also be configured in outdoor facilities such as medical sites, event venues, and railway lines, or indoor facilities such as factories, workshops, offices, and commercial facilities, in addition to road 32.

[0021] The wireless transmission system 1 includes a base station 33, an electromagnetic wave reflector 60, and a leaky coaxial cable 80. As an example, the base station 33 performs wireless communication at a frequency included in a frequency band of 1 MHz to 300 GHz. As an example, the electromagnetic wave reflector 60 has a reflective panel that reflects radio waves of the frequency of the base station 33. As an example, the leaky coaxial cable 80 is connected to the antenna terminal of the base station 33, is arranged along a road 32, and performs wireless communication at a frequency included in a frequency band of 1 MHz to 300 GHz.

[0022] exist Figure 1A The image shows a wireless environment with road 32 as the communication area, as an example of an outdoor environment. Figure 1A In the coordinate system, the length direction of road 32 is defined as the X direction, the width direction as the Y direction, and the direction perpendicular to the road surface as the Z direction. Multiple vehicles 31 travel on road 32. Vehicles 31 can be vehicles with autonomous driving or semi-autonomous driving functions, or vehicles without autonomous driving functions. In either case, they not only have mobile terminals held by the driver or passengers, but also wireless communication functions mounted on the vehicle 31 itself, transmitting and receiving large amounts of data between the vehicle 31 and the control and management system.

[0023] To enable wireless communication between a mobile entity like vehicle 31 and the network, a base station 33 and a leaky coaxial cable 80 are arranged along road 32. The leaky coaxial cable 80 is connected to the base station 33 and radiates radio waves supplied from the base station 33. Here, it is described that the base station 33 radiates radio waves directly from its antenna and supplies radio waves to the leaky coaxial cable 80, and the leaky coaxial cable 80 also radiates radio waves. However, it is also possible for the base station 33 to only output radio waves to the leaky coaxial cable 80, without radiating radio waves itself.

[0024] As an example, base station 33 and leaky coaxial cable 80 transmit and receive signals or data with vehicle 31 at a specified frequency in a frequency band of 1 MHz to 300 GHz. Furthermore, due to the terrain of road 32, the surrounding environment, and the presence of multiple vehicles 31, in order to ensure that high-frequency radio waves lacking straight-line travel reach each vehicle 31 more reliably from base station 33 and leaky coaxial cable 80, multiple electromagnetic wave reflecting devices 60 are arranged on both sides of road 32 (both sides in the width direction of road 32) along the travel direction of the vehicles 31 in road 32. Multiple electromagnetic wave reflecting devices 60 can also be connected and installed as an electromagnetic wave reflecting fence on the shoulder of road 32. The electromagnetic wave reflecting fence will be used in the following text. Figure 2A Please provide an explanation.

[0025] As an example, the radio waves transmitted and received by base station 33 and leaky coaxial cable 80 are preferably radio waves in the Sub-6 GHz band and the 1 GHz to 300 GHz band of the millimeter wave band, including fifth-generation mobile communication systems (5G). Currently, the next-generation 6G mobile communication standard is expected to expand to the Asia-Pacific Hertz band, utilizing the Sub-6 GHz band and the 28 GHz band included in the millimeter wave band. By using such high-frequency bands, the communication bandwidth is significantly expanded, enabling large-volume data communication with low latency.

[0026] In addition, the radio waves transmitted and received by base station 33 and leaky coaxial cable 80 can also be LTE (Long Term Evolution), LTE-A (LTE-Advanced), UMB (Ultra Mobile Broadband), or CBRS (Citizens Broadband Radio Service). Furthermore, the radio waves transmitted and received by base station 33 and leaky coaxial cable 80 can also be IEEE 802.11 (Wi-Fi, registered trademark), IEEE 802.16 (WiMAX, registered trademark), IEEE 802.20, UWB (Ultra-Wideband), Bluetooth, or LPWA (Low Power Wide Area), etc.

[0027] As an example, the uppermost part (upper end) of the electromagnetic wave reflecting device 60 is positioned higher than the base station 33. The base station 33 preferably has a directional antenna that forms a beam towards the road 32 from a position sandwiched between the electromagnetic wave reflecting devices 60 on both sides of the road 32. Additionally, the leaky coaxial cable 80, together with the electromagnetic wave reflecting devices 60, is arranged on both sides of the road 32 along the direction of travel of the vehicles 31 within the road 32.

[0028] Compared to conventional coaxial cables, leaky coaxial cables 80 have less freedom of bending and coiling. Therefore, it is impractical to lay cables while bending them along the ground or floor. For this reason, it is advantageous to place the leaky coaxial cable 80 along an electromagnetic wave reflector 60 arranged in a straight line for wiring purposes. Furthermore, if the leaky coaxial cable 80 is placed too high, it is difficult to obtain sufficient intensity of the downward-radiated electromagnetic waves. Therefore, from the viewpoint of constructing a wireless communication area, it is advantageous to install the electromagnetic wave reflector 60 at a height of 2m to 3m or less.

[0029] The leaky coaxial cable 80 is positioned at the center of the width of the electromagnetic wave reflecting devices 60 on both sides of the road 32. That is, the leaky coaxial cable 80 is positioned within the area surrounded by the plurality of electromagnetic wave reflecting devices 60 and the road surface (ground) of the road 32, and connects to the antenna terminal of the base station 33. Furthermore, as an example, the leaky coaxial cable 80 is positioned within this area lower than the uppermost part (top end) of the electromagnetic wave reflecting device 60.

[0030] The area surrounded by the multiple electromagnetic wave reflectors 60 installed on both sides of the road 32 and the road surface (ground) of the road 32 is located at a position higher than the uppermost part (top end) of the electromagnetic wave reflectors 60 in the vertical direction. Since the leaky coaxial cable 80 only needs to be installed within this area, it can also be installed at a position higher than the uppermost part (top end) of the electromagnetic wave reflectors 60.

[0031] Furthermore, the area surrounded by the multiple electromagnetic wave reflecting devices 60 installed on both sides of the road 32 and the road surface (ground) of the road 32 also includes the area directly above the electromagnetic wave reflecting devices 60. That is, the leaky coaxial cable 80 can also be located directly above the electromagnetic wave reflecting device 60. For example, the leaky coaxial cable 80 can be installed along the uppermost part (upper end) of the electromagnetic wave reflecting device 60, or it can be installed directly above the electromagnetic wave reflecting device 60 via a fixing member installed at the uppermost part (upper end) of the electromagnetic wave reflecting device 60. The leaky coaxial cable 80 being located directly above the electromagnetic wave reflecting device 60 means that when viewed from directly above, there is a portion where the leaky coaxial cable 80 and the electromagnetic wave reflecting device 60 overlap in the width direction of the road 32. In addition, when the leaky coaxial cable 80 is located directly above the electromagnetic wave reflecting device 60, the gap 83A is preferably oriented towards the central side in the width direction of the road 32. This is because the electromagnetic waves emitted from the gap 83A can be emitted towards the road 32.

[0032] In addition to the directional antenna of base station 33, electromagnetic wave reflectors 60 and leaky coaxial cables 80 are also arranged on both sides of road 32. This allows the electromagnetic waves emitted from base station 33 and leaky coaxial cables 80 to be efficiently concentrated on road 32 and suppresses electromagnetic waves that leak out of road 32. As a result, the received power is lower in the area outside the electromagnetic wave reflectors 60 on both sides of road 32 compared to the average or central value of the received power on road 32 sandwiched between the electromagnetic wave reflectors 60.

[0033] Even if the beam shape is controlled by the base station 33, there may be situations where other vehicles 31 obstruct the line of sight (LOS). In such cases, radio waves emitted from the leaky coaxial cable 80, which is installed along both sides of the road 32, can reach the vehicle 31. Furthermore, the electromagnetic wave reflecting device 60 can reflect the radio waves emitted from the base station 33 and the leaky coaxial cable 80 and deliver them to the vehicle 31.

[0034] The size of the reflecting surface of the electromagnetic wave reflecting device 60 is sufficient to cover at least the area determined by the radius R of the first Fresnel region. The radius R of the first Fresnel region when the electromagnetic waves radiated from the antenna of the base station 33 and reflected by the electromagnetic wave reflecting device 60 arrive at the vehicle 31 in phase is defined by the following formula.

[0035] R=[λd1d2 / (d1+d2)】 1 / 2

[0036] Here, λ is the wavelength used, d1 is the distance from the antenna of the base station 33 to the electromagnetic wave reflecting device 60, and d2 is the distance from the electromagnetic wave reflecting device 60 to the antenna of the vehicle 31.

[0037] If, in the 28GHz band (wavelength approximately 10.7mm), the distance d1 from the antenna of base station 33 to electromagnetic wave reflector 60 is 20.0mm, and the distance d2 from electromagnetic wave reflector 60 to vehicle 31 is 10.0m, then the size of the reflective surface of electromagnetic wave reflector 60 only needs to be a few tens of centimeters on one side. On the other hand, from the viewpoint of forming an electromagnetic wave reflective fence that covers a wide reflective area with a small number of electromagnetic wave reflectors 60, the width × length of the reflective surface of electromagnetic wave reflector 60 can also be approximately 2.0m × 4.0m. In this embodiment, electromagnetic wave reflectors 60 are arranged along road 32 such that the received power in the area outside road 32 (the area behind the reflective surface of electromagnetic wave reflector 60) is lower than the average or central value of the received power on road 32.

[0038] <Structure of Leaky Coaxial Cable 80>

[0039] Figure 1BThis is a diagram illustrating an example of the structure of a leaky coaxial cable 80. The leaky coaxial cable 80 has an inner conductor 81, an insulation layer 82, an outer conductor 83, and an insulating film 84. The inner conductor 81 is a core wire, which, as an example, is made of a metal such as copper or aluminum. As an example, the insulation layer 82 is an insulation system made of foamed polyethylene or the like, which covers the inner conductor 81 and insulates the inner conductor 81 from the outer conductor 83.

[0040] The outer conductor 83 is a cylindrical conductor disposed along the outer surface of the insulation layer 82. As an example, it is made by winding a strip of metal such as copper or aluminum around the outer surface of the insulation layer 82. The outer conductor 83 has a plurality of slits 83A disposed along the extension direction (X direction) of the leaky coaxial cable 80. Figure 1B The diagram shows a structure in which straight slots 83A are arranged in a wavy pattern along the extension direction of the leaky coaxial cable 80, but slots 83A are not limited to being straight and can also be of various shapes. Furthermore, the arrangement of multiple slots is not limited to a wavy pattern. An insulating film 84 covers the outer surface of the outer conductor 83; as an example, it is made of a resin such as heat-resistant and flame-retardant polyethylene.

[0041] If one end of the inner conductor 81 of such a leaky coaxial cable 80 is connected to the signal terminal (power supply terminal) in the antenna terminal of the base station 33, and one end of the outer conductor 83 is connected to the ground terminal in the antenna terminal of the base station 33, then when the base station 33 transmits radio waves, a signal is supplied from the antenna terminal of the base station 33 to the leaky coaxial cable 80, and radio waves are transmitted from the gap 83A to the surrounding area of ​​the leaky coaxial cable 80. Furthermore, when the base station 33 receives radio waves, the radio waves around the leaky coaxial cable 80 are received by the gap 83A and transmitted by the leaky coaxial cable 80 to the base station 33.

[0042] Therefore, by connecting the leaky coaxial cable 80 to the antenna terminal of the base station 33, a wireless communication area can be constructed around the leaky coaxial cable 80 along the road 32. The leaky coaxial cable 80 serves as both a transmission path and an antenna.

[0043] <Installation structure of electromagnetic wave reflecting device 60, electromagnetic wave reflecting fence 100A and leaky coaxial cable 80>

[0044] Figure 2AThis is a diagram illustrating an example of the structure of an electromagnetic wave reflecting fence 100A. The electromagnetic wave reflecting fence 100A is formed by connecting electromagnetic wave reflecting devices 60-1, 60-2, and 60-3 (hereinafter, sometimes appropriately referred to collectively as "reflecting panels 10") having reflecting panels 10-1, 10-2, and 10-3 (hereinafter, sometimes appropriately referred to collectively as "reflecting panels 10") via a frame 50A. That is, the electromagnetic wave reflecting fence 100A includes multiple electromagnetic wave reflecting devices 60. The structure of each electromagnetic wave reflecting device 60 is similar to... Figure 1A The electromagnetic wave reflecting devices 60 shown have the same structure.

[0045] Figure 2A coordinate system and Figure 1A The coordinate system is consistent, with the width or horizontal direction of the reflective panel 10 set as the X direction, the thickness direction as the Y direction, and the height direction as the Z direction. Figure 2A In this process, three electromagnetic wave reflecting devices 60 are connected to form an electromagnetic wave reflecting fence 100A, but the number of multiple electromagnetic wave reflecting devices 60 connected is appropriately determined according to the conditions of the road 32.

[0046] As an example Figure 2A The electromagnetic wave reflecting fence 100A shown has a reflective surface on the +Y direction side and is positioned on the right side of the road 32 relative to the travel direction (+X direction). A leaky coaxial cable 80 is disposed on the reflective surface of the electromagnetic wave reflecting fence 100A. The reflective surface of the electromagnetic wave reflecting fence 100A, positioned on the left side of the road 32 relative to the travel direction (+X direction), is located on the -Y direction side; therefore, the leaky coaxial cable 80 is located on the -Y direction side of the electromagnetic wave reflecting fence 100A. Thus, by providing leaky coaxial cables 80 on the reflective surfaces of the electromagnetic wave reflecting fence 100A on both sides of the road 32, a wireless communication area can be established along the road 32 even at locations far from the base station 33 in the travel direction of the road 32.

[0047] The reflective panel 10 used in the electromagnetic wave reflecting device 60 reflects electromagnetic waves of 1 MHz or higher and 300 GHz or lower, preferably 1 GHz or higher and 100 GHz or lower, and more preferably 1 GHz or higher and 80 GHz or lower. The reflective panel 10, as a reflective film, has a layer containing a conductive film. The conductive film has a predetermined conductive pattern designed according to the reflection angle, frequency band, etc., of the target. The conductive pattern includes periodic patterns, grid patterns, geometric patterns, etc., and may also be formed from a transparent conductive film. The reflective panel 10 has a protective layer with ultraviolet protection function on its outermost layer.

[0048] At least a portion of the reflective panel 10 can also be a non-mirror reflective surface where the incident angle and reflection angle of the electromagnetic wave are different. In addition to diffusers and scatterers, non-mirror reflective surfaces also include artificial reflective surfaces, i.e., metasurfaces, designed to reflect electromagnetic waves in a desired direction. Reflective panels 10-1, 10-2, and 10-3 are sometimes preferably electrically connected to each other from the viewpoint of maintaining the continuity of the reflected potential; however, in the case of metasurfaces, adjacent reflective panels 10 may not be electrically connected. By holding adjacent reflective panels 10 together with a frame 50A, an electromagnetic wave reflective enclosure 100A connected in the X direction can be obtained.

[0049] In addition to the reflective panel 10 and the frame 50A, the electromagnetic wave reflecting device 60 may also have legs 56 supporting the frame 50A. The legs 56 can also allow the electromagnetic wave reflecting device 60 or the electromagnetic wave reflecting fence 100A to stand independently on the ground. Alternatively, the legs 56 can be fixed to the ground using screws or similar fasteners. Conversely, the electromagnetic wave reflecting device 60 or the electromagnetic wave reflecting fence 100A can be made to stand independently on the ground and also include casters or similar components for mobility. Besides the frame 50A, a top frame 57 holding the upper end of the reflective panel 10 and a bottom frame 58 holding the lower end can also be used. In this case, the frame 50A, top frame 57, and bottom frame 58 constitute a frame that holds the entire circumference of the reflective panel 10. The frame 50A may also be referred to as a "side frame" depending on its positional relationship relative to the top frame 57 and bottom frame 58. By providing the top frame 57 and bottom frame 58, the mechanical strength and safety of the reflective panel 10 during handling and assembly are ensured. The top frame 57 can also be configured to connect other reflective panels or electromagnetic wave absorbing panels, or other components, to the upper end of the reflective panel 10. This increases the flexibility in the size and function of the electromagnetic wave reflective fence 100A.

[0050] Additionally, as an example, the leaky coaxial cable 80 is fixed to the frame 50A by a fastener 85. The fastener 85 can be any component capable of fixing the leaky coaxial cable 80 relative to the electromagnetic wave reflector 100A. As an example, the fastener 85 may be a component with mounting holes formed in the frame 50A, into which the leaky coaxial cable 80 is inserted and fixed using bolts or the like while held in place. Such a fastener 85 can be made of metal or resin.

[0051] As an example, when fixing the leaky coaxial cable 80 to the electromagnetic wave reflecting fence 100A, the following can also be done: The height of the leaky coaxial cable 80 above the ground can be below the height of the upper ends of the multiple electromagnetic wave reflecting devices 60 above the ground. By making the height of the leaky coaxial cable 80 above the ground below the height of the upper ends of the multiple electromagnetic wave reflecting devices 60 above the ground, the electromagnetic waves emitted from the gap 83A can be reflected by the electromagnetic wave reflecting devices 60 towards the center side of the road 32 in the width direction, and leakage of electromagnetic waves to the outer side of the electromagnetic wave reflecting devices 60 on both sides of the road 32 can be suppressed. Alternatively, the height of the leaky coaxial cable 80 above the ground can also be higher than the height of the upper ends of the multiple electromagnetic wave reflecting devices 60 above the ground.

[0052] Furthermore, the multiple slits 83A of the leaky coaxial cable 80 can also be oriented towards the center side in the width direction of the road 32. By oriented the slits 83A towards the center side in the width direction of the road 32, the radio waves radiated from the slits 83A can easily reach the vehicle 31. In addition, although the multiple slits 83A of the leaky coaxial cable 80 can also be oriented in directions other than the center side in the width direction of the road 32, from the point of view of communication efficiency, it is not preferable to only oriented them upwards.

[0053] Furthermore, when the wavelength of the radio wave in free space is set as λ, and any natural number is set as N, the distance D between the multiple electromagnetic wave reflecting devices 60 and the leaky coaxial cable 80 in the width direction (Y direction) of the road 32 can also be set to satisfy D ≠ (1 / 4 + N) × λ. Although the distance D is in... Figure 2A Not shown, but specifically the distance in the Y direction between the reflective surface of the electromagnetic wave reflecting device 60 and the gap 83A of the leaky coaxial cable 80 located on the center side in the width direction of the road 32.

[0054] By ensuring that the distance D satisfies the following relationship, it is possible to suppress the electromagnetic waves radiated from the gap 83A of the leaky coaxial cable 80 to the central side of the road 32 in the width direction from becoming out of phase with the electromagnetic waves reflected by the electromagnetic wave reflecting device 60 to the central side of the road 32 in the width direction, thereby suppressing the electromagnetic waves from canceling each other out.

[0055] Furthermore, the distance D between the multiple electromagnetic wave reflecting devices 60 and the leaky coaxial cable 80 can be less than 0.3m. If the distance D is long, the intensity of the reflected wave that propagates from the leaky coaxial cable 80 to the center side of the road 32 in the width direction after being reflected by the electromagnetic wave reflecting devices 60 will be lower. Therefore, it is preferable that the leaky coaxial cable 80 is appropriately close to the electromagnetic wave reflecting devices 60.

[0056] Furthermore, the width of road 32 can be 5m to 20m. Although it depends on the intensity of the radio waves, as an example, it is around 10dBi to 30dBi at most. This is a realistic distance at which vehicle 31 can receive radio waves emitted from the gaps 83A of the leaky coaxial cables 80 arranged on both sides of road 32 and obtain data.

[0057] <Indoor Wireless Transmission System 1>

[0058] Figure 2B This is a diagram illustrating an example of a production line 35 in a factory equipped with the wireless transmission system 1 implemented in this manner. Figure 2B In this system, the wireless transmission system 1 is installed indoors. Production line 35 is a strip-shaped production station that integrates machinery and equipment used for assembly and production as a series of processes. In Industrial IoT (Internet of Things), production efficiency is improved and on-site safety is ensured by connecting the industrial devices, equipment, management systems, etc., used in production line 35 to the network.

[0059] In order to connect the equipment on production line 35 to the network, and Figure 1A The road 32 shown is similarly equipped with a base station 33, an electromagnetic wave reflector 60, and a leaky coaxial cable 80. Figure 2B In this example, multiple AGVs (Automatic Guided Vehicles) are configured as equipment used in production line 35, each connected to the network via a base station 33 and a leaky coaxial cable 80. Figure 2B As an example, production line 35 shown manufactures automobiles.

[0060] To enable wireless connectivity between the equipment on production line 35 and the network, base station 33, electromagnetic wave reflector 60, and leaky coaxial cable 80 provide a long wireless communication area in the horizontal direction. In the technical specification (TS22.104) of the mobile communications standardization organization 3GPP (registered trademark), a system requirement specifies a wireless communication area with an aspect ratio of 3 to 5 times in a rectangular area in a horizontal plane. For example, the area size for the use case referred to as "Motion Control" is specified as 50m × 10m × 10m (length × width × height).

[0061] To enable network connectivity for devices within the production line 35 by covering the wireless communication area provided by the base station 33, electromagnetic wave reflectors 60, and leaky coaxial cables 80, multiple electromagnetic wave reflectors 60 are arranged on both sides of the production line 35 along its direction of travel (+X direction), and leaky coaxial cables 80 are arranged along the electromagnetic wave reflectors 60. This is effective in terms of coverage. This is consistent with... Figure 1A The same applies to road 32 shown.

[0062] exist Figure 2B In the coordinate system, the length direction (travel direction) of production line 35 is set as the X direction, the width direction as the Y direction, and the direction perpendicular to the ground as the Z direction. Multiple car bodies are transported on production line 35. Although in Figure 2B The diagram shows a production line 35 for vehicle bodies as an example, but it could also be a production line for products other than vehicles. AGVs and other equipment configured around production line 35 have wireless communication capabilities, enabling the transmission and reception of large amounts of data between the AGVs / equipment and the control and management system.

[0063] exist Figure 2B In the production line 35 shown, a leaky coaxial cable 80 is fixed to the electromagnetic wave reflecting device 60 on the +Y direction side. As an example, the leaky coaxial cable 80 is fixed to the electromagnetic wave reflecting device 60 using... Figure 2A The fastener 85 shown is sufficient. As an example, the height of the electromagnetic wave reflecting device 60 on the +Y direction side is lower than the height of the upper end of the electromagnetic wave reflecting device 60. In addition, as an example, the height of the base station 33 connected to the leaky coaxial cable 80 on the +Y direction side is lower than the height of the uppermost part (upper end) of the electromagnetic wave reflecting device 60 on the +Y direction side.

[0064] Furthermore, the leaky coaxial cable 80 on the -Y direction side is suspended from the ceiling by a support member 90. As an example, the height of the leaky coaxial cable 80 on the -Y direction side is higher than the height of the upper end of the electromagnetic wave reflecting device 60 on the -Y direction side. Also, as an example, the leaky coaxial cable 80 on the -Y direction side is positioned in the Y direction closer to the +Y direction side than the electromagnetic wave reflecting device 60 on the -Y direction side. This is to allow reflected waves to propagate towards the +Y direction side and to suppress leakage of electromagnetic waves towards the electromagnetic wave reflecting device 60 closer to the -Y direction side than the -Y direction side.

[0065] Additionally, as an example, the height of the base station 33 connected to the leaky coaxial cable 80 on the -Y direction side is higher than the height of the uppermost part (upper end) of the electromagnetic wave reflecting device 60. However, for example, by further lengthening the support 90 suspending the leaky coaxial cable 80 and lowering the position of the retaining member (not shown) holding the base station 33, the height of the leaky coaxial cable 80 and the base station 33 on the -Y direction side can also be made lower than the height of the uppermost part (upper end) of the electromagnetic wave reflecting device 60. This method is advantageous for illuminating the beam from the directional antenna of the base station 33 toward the production line 35.

[0066] like Figure 2B As shown, the wireless transmission system 1 can also be configured indoors, and a long wireless communication area in the direction of travel of the production line 35 can be achieved using a leaky coaxial cable 80.

[0067] <Layer Structure of Reflective Panel 10>

[0068] Figure 3 This is a diagram showing an example of the layer structure of the reflective panel 10. Figure 3 The layered structure shown is the layered structure on the XY section of the reflective panel 10, with the stacking direction being the thickness direction (Y direction) of the reflective panel 10. Figure 3 As an example, a cross-section of the reflective panel 10 of the electromagnetic wave reflective device 60, which is configured on the -Y direction side of the road 32 or the production line 35, is shown when viewed from the top (+Z direction side).

[0069] The reflective panel 10 includes a dielectric layer 11, a periodic conductive pattern 15 disposed on one surface 111 of the dielectric layer 11, and a ground layer 12 disposed on the other surface 112 of the dielectric layer 11. The conductive pattern 15 forms the reflective surface of the reflective panel 10, reflecting electromagnetic waves of 1 MHz or higher and 300 GHz or lower in a predetermined direction.

[0070] The conductive pattern 15 comprises a periodic arrangement of a plurality of hollow patterns 151. The specific shape of the hollow patterns 151 will be described later. Figure 4 The following explanation is provided. As an example, the hollow pattern is formed from good conductors such as Ag, Cu, Ni, and Al, and as an example, its thickness is 0.01 mm or more and 0.05 mm or less. If it is less than 0.01 mm, the surface resistivity becomes high, making it difficult to maintain high reflection efficiency. If it is thicker than 0.05 mm, it is difficult to maintain the flatness of the reflective surface. Alternatively, a transparent thin film with the same dielectric constant and dielectric loss tangent as the dielectric layer 11 can be used to protect the surface of the conductive pattern 15.

[0071] As an example, the hollow pattern 151 is bonded to the dielectric layer 11 via an adhesive layer 13. As an example, the adhesive layer 13 is not coated across the entire surface of the dielectric layer 11, but rather used in an amount necessary to stably hold the hollow pattern 151. This is to minimize the influence of the adhesive layer 13 on the dielectric constant of the dielectric layer 11. The area occupied by the adhesive layer 13 does not need to be exactly the same as the area occupied by the conductive pattern 15; some deviation is permissible within a range that allows the hollow pattern 151 to be stably bonded to the dielectric layer 11. For example, if the area occupancy of the conductive pattern 15 relative to the dielectric layer 11 is 10.0% or more and 45.0% or less, then the area occupancy of the adhesive layer 13 relative to the dielectric layer 11 is 9.0% or more and 50.0% or less.

[0072] If the area occupancy of the conductive pattern 15 is less than 10.0%, it is difficult to achieve the desired reflective characteristics and reflective efficiency. If the area occupancy of the conductive pattern 15 exceeds 45.0%, it is difficult to maintain the transparency of the reflective panel 10. However, in applications where transparency is not required, the area occupancy of the conductive pattern 15 can be greater than 45.0% to prioritize reflective efficiency.

[0073] The adhesive layer 13 is made of a material capable of bonding the conductive pattern 15 to the dielectric layer 11. For example, thermoplastic resins such as vinyl acetate resin, acrylic resin, cellulose resin, and silicone resin can also be used. The thickness of the adhesive layer 13 is such that the conductive pattern 15 can be stably bonded to the dielectric layer 11, for example, it is 0.002 mm or more and 0.050 mm or less. From the viewpoint of ensuring adhesion, it is preferable to be 0.010 mm or more and 0.050 mm or less.

[0074] The dielectric layer 11 is an insulating polymer film such as polycarbonate, cyclic olefin polymer (COP), polyethylene terephthalate (PET), or fluoropolymer, with a thickness of approximately 0.3 mm to 1.0 mm. The dielectric layer 11 only needs to be made of a material with a relative permittivity and dielectric loss tangent suitable for achieving the target reflection characteristics.

[0075] The ground layer 12 can be formed of the same material as the conductive pattern 15, or it can be formed of a different conductive material. A predetermined parasitic capacitance is formed between the ground layer 12 and the conductive pattern 15. The amount of phase delay is determined by the parasitic capacitance formed between the conductive pattern 15 and the ground layer 12.

[0076] Furthermore, as an example, the reflective panel 10 can also be sandwiched between two dielectric substrates. Such dielectric substrates can be transparent to electromagnetic waves in the gigahertz to terahertz bands, specifically between 1 MHz and 3 THz, for example, electromagnetic waves between 1 MHz and 300 GHz. The dielectric substrate, as the outermost layer of the reflective panel 10, is preferably formed of a material with excellent impact resistance, durability, and transparency. Polycarbonate, acrylic resin, PET, etc., can be used as the dielectric substrate. The thickness of one dielectric substrate can be appropriately selected, for example, between 1.0 mm and 10.0 mm, depending on the installation location. The two dielectric substrates can have the same or different thicknesses.

[0077] <Example of a hollow pattern structure>

[0078] Figure 4 This is a diagram illustrating an example of the structure of a unit cell 20 of a conductive pattern 15 composed of hollow patterns 151. Figure 4 As an example, the structure of the reflective panel 10 of the electromagnetic wave reflective device 60, which is disposed on the -Y side of the road 32 or the production line 35, is shown when viewed from the +Y side.

[0079] exist Figure 4 In the example shown, unit cell 20 has six hollow patterns 151a, 151b, 151c, 151d, 151e, and 151f. The directions of the width W1 and length L of the hollow patterns 151a to 151f are respectively perpendicular to... Figure 2A The width (X) and height (Z) directions of the reflective panel 10 are aligned. The hollow patterns 151a to 151f have equal widths W1 and different lengths L, but their central axes are aligned (the Y-coordinate position of the central axis is constant). The spacing or interval G in the X direction is constant. The phase of the reflection is controlled by the shape and size of the hollow patterns 151a to 151f, and a reflected beam is formed in the desired direction by the overlap of the reflected waves. In this example, the unit cell 20 is designed to reflect the beam of the reflected wave of a vertically incident (incident angle 0°) electromagnetic wave in a direction 50° from the vertical.

[0080] Hollow patterns 151a, 151b, 151c, 151d, 151e, and 151f (hereinafter, sometimes collectively referred to as "hollow pattern 151") are hollowed out with a width W2. The hollow patterns have a rectangular ring shape when viewed from the XZ plane. Half the difference between the outer circumference width W1 and the inner circumference width W2 of each hollow pattern 151 is the width of the longitudinal line segment. Similarly, the thickness of the transverse line segments of the hollow pattern 151 is determined by the area of ​​the hollowed-out area. Both vertically polarized and horizontally polarized waves can be reflected through the longitudinal and transverse line segments of the hollow pattern 151.

[0081] The corners of the outer edge of the hollow pattern 151 can be right angles without curvature, or they can be curved with a radius of curvature R1. In the case of right angles, the radius of curvature R1 = 0.0 mm. The corners of the inner periphery of the hollow pattern 151 are curved with a radius of curvature R2. The radius of curvature R1 is the same as or less than R2. By rounding the corners of the hollow pattern 151, especially the corners on the inner edge side, with a specified radius of curvature, current concentration is prevented and reflection efficiency is maintained. Specifically, by giving the corners on the inner edge side of the hollow pattern 151 a rounded corner with a radius of curvature R2 that is more than 1 / 10 and less than 1 / 2 of the width W1, current concentration can be suppressed, and it is responsive to both vertically polarized waves and horizontally polarized waves.

[0082] The conductive pattern 15 is a periodic pattern formed by repeatedly arranging unit cells 20 in the X and Z directions. By providing a reflective surface formed by the conductive pattern 15 on at least a portion of the reflective panel 10, it is possible to reflect both incident horizontally polarized waves and vertically polarized waves in a controlled direction.

[0083] <Experimental Results>

[0084] An experiment was conducted in an indoor facility with a length of 100.0m, a width of 50.0m, and a ceiling height of 10.0m. A production line for assembling automotive parts was located in the central area, and an experiment was conducted in the space surrounding it containing multiple structures such as metal frames, AGVs (Automated Guided Vehicles), and robotic arms. Without the electromagnetic wave reflector 60 and the leaky coaxial cable 80, a blind spot existed on the back side of the structures. Hereinafter, the width of the electromagnetic wave reflector 60 refers to… Figure 2B The width in the X direction refers to the width of the electromagnetic wave reflecting device 60, while the height in the Z direction refers to the height of the electromagnetic wave reflecting device 60.

[0085] <Example 1>

[0086] Example 1 is Example 1. A base station with an antenna having a maximum output of 20dBm, a vertical angle of 15°, a horizontal angle of 30°, and a half-width is configured at a position 7.5m away from the end of the connected electromagnetic wave reflecting device 60 in the X direction and at a height of 5.0m, and transmits and receives radio waves in the 28.2GHz band.

[0087] Thirty electromagnetic wave reflecting devices 60, each 1.0m wide and 2.0m high, are installed on both sides of the production line in the width direction, and a 30.0m electromagnetic wave reflecting fence 100A is installed along the production line. The electromagnetic wave reflecting fences 100A on both sides of the production line are spaced 10.0m apart and are arranged parallel to the production line.

[0088] A leaky coaxial cable 80 is installed on the reflective surface of the electromagnetic wave reflecting device 60 of the electromagnetic wave reflecting fence 100A and connected to the antenna terminal of the base station. The orientation of the gap 83A is set so that the electromagnetic waves emitted from the gap 83A of the leaky coaxial cable 80 propagate towards multiple structures such as production lines, metal frames, AGVs, automated guided vehicles, and robotic arms. Before and after the installation of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the electromagnetic wave intensity in the blind zone changes from -110.0 dBm to -85.0 dBm, confirming an improvement of +25.0 dB. In addition, before and after the installation of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the electromagnetic wave intensity on the outer side of the electromagnetic wave reflecting device 60 (the back side when viewed from the production line) remains unchanged at -125.0 dBm.

[0089] Thus, in Example 1, it can be confirmed that by setting up the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the blind spots in the production line can be reduced, and the leakage of electromagnetic waves to the outside of the area where the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80 are set up can be suppressed.

[0090] <Example 2>

[0091] Example 2 is Example 2. A base station with an antenna having a maximum output of 20dBm, a vertical angle of 15°, a horizontal angle of 30°, and a half-width is configured at a position 5.0m away from the end of the connected electromagnetic wave reflecting device 60 in the X direction and at a height of 10.0m, and transmits and receives radio waves in the 28.2GHz band.

[0092] Thirty electromagnetic wave reflecting devices 60, each 1.0m wide and 2.0m high, are installed on both sides of the production line in the width direction, and a 30.0m electromagnetic wave reflecting fence 100A is installed along the production line to connect them. The electromagnetic wave reflecting fences 100A on both sides of the production line are spaced 10.0m apart and are arranged parallel to the production line.

[0093] The leaky coaxial cable 80 is suspended from the ceiling and positioned 30cm above the electromagnetic wave reflecting device 60, which is located above the electromagnetic wave reflecting fence 100A, and connected to the antenna terminal of the base station. The orientation of the gap 83A is set so that the electromagnetic waves emitted from the gap 83A of the leaky coaxial cable 80 propagate towards multiple structures such as production lines, metal frames, AGVs, automated guided vehicles, and robotic arms. Before and after the installation of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the electromagnetic wave intensity in the blind zone changed from -110.0dBm to -92.0dBm, confirming an improvement of +18.0dB. Furthermore, before and after the installation of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the electromagnetic wave intensity on the outer side of the electromagnetic wave reflecting device 60 (the back side when viewed from the production line) remained unchanged at -125.0dBm.

[0094] Thus, in Example 2, it can be confirmed that by installing the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, blind spots in the production line can be reduced, and leakage of electromagnetic waves to the outside of the area where the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80 are installed can be suppressed. Compared with Example 1, since the improvement in electromagnetic wave intensity is small, it can be seen that the improvement effect on electromagnetic wave intensity is high when the leaky coaxial cable 80 is placed on the reflecting surface of the electromagnetic wave reflecting device 60.

[0095] <Example 3>

[0096] Example 3 is Example 3. A base station with an antenna having a maximum output of 20dBm, a vertical angle of 15°, a horizontal angle of 30°, and a half-width is configured at a position 10.0m away from the end of the connected electromagnetic wave reflecting device 60 in the X direction and at a height of 10.0m, and transmits and receives radio waves in the 28.2GHz band.

[0097] Thirty electromagnetic wave reflecting devices 60, each 1.0m wide and 2.0m high, are installed on both sides of the production line in the width direction, and a 30.0m electromagnetic wave reflecting fence 100A is installed along the production line to connect them. The electromagnetic wave reflecting fences 100A on both sides of the production line are spaced 20.0m apart and are arranged parallel to the production line.

[0098] The leaky coaxial cable 80 is suspended from the ceiling and positioned 50 cm above the upper end of the electromagnetic wave reflecting device 60, which is located above the electromagnetic wave reflecting fence 100A, and connected to the antenna terminal of the base station. The orientation of the gap 83A is set so that the electromagnetic waves emitted from the gap 83A of the leaky coaxial cable 80 propagate towards multiple structures such as production lines, metal frames, AGVs, automated guided vehicles, and robotic arms. Before and after the installation of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the electromagnetic wave intensity in the blind zone changes from -110.0 dBm to -100.0 dBm, confirming an improvement of +10.0 dB. Furthermore, before and after the installation of the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the electromagnetic wave intensity on the outer side of the electromagnetic wave reflecting device 60 (the back side when viewed from the production line) remains unchanged at -125.0 dBm.

[0099] Thus, in Example 3, it can be confirmed that by installing the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the blind zone in the production line can be reduced, and leakage of electromagnetic waves to the outside of the area where the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80 are installed can be suppressed. Compared with Example 1, since the improvement in electromagnetic wave intensity is small, it can be seen that the improvement effect on electromagnetic wave intensity is high when the leaky coaxial cable 80 is placed on the reflecting surface of the electromagnetic wave reflecting device 60. In addition, compared with Example 2, since the height of the leaky coaxial cable 80 is increased, the effect of reducing the blind zone is small.

[0100] <Example 4>

[0101] Example 4 is a comparative example of Example 1. In Example 4, the experiment was conducted without a leaky coaxial cable 80, and only an electromagnetic wave reflecting device 60 was used. The experimental conditions of Example 4 were the same as those in Example 2, except that the leaky coaxial cable 80 was omitted.

[0102] A base station with an antenna having a maximum output of 20dBm, a vertical angle of 15°, and a horizontal angle of 30° and a half-width is configured at a position 5.0m away from the end of the connected electromagnetic wave reflector 60 in the X direction and at a height of 10.0m, and transmits and receives radio waves in the 28.2GHz band.

[0103] Thirty electromagnetic wave reflecting devices 60, each 1.0m wide and 2.0m high, are installed on both sides of the production line in the width direction, and a 30.0m electromagnetic wave reflecting fence 100A is installed along the production line to connect them. The electromagnetic wave reflecting fences 100A on both sides of the production line are spaced 10.0m apart and are arranged parallel to the production line.

[0104] When radio waves are emitted from the base station's antenna, the radio wave intensity in the dead zone changes from -110.0 dBm to -108.0 dBm, confirming an improvement of only +2.0 dB. Furthermore, the radio wave intensity on the outer side of the electromagnetic wave reflecting device 60 (the back side when viewed from the production line) remains unchanged at -85.0 dBm.

[0105] <Example 5>

[0106] Example 5 is a comparative example of Example 2. In Example 5, the electromagnetic wave reflecting device 60 was not used; instead, only a leaky coaxial cable 80 was used for the experiment. The experimental conditions in Example 5 were the same as in Example 2, except that the leaky coaxial cable 80 was omitted.

[0107] A base station with an antenna having a maximum output of 20dBm, a vertical angle of 15°, and a horizontal angle of 30° and a half-width is configured at a position 25.0m away from the end of the connected electromagnetic wave reflector 60 in the X direction and at a height of 10.0m, and transmits and receives radio waves in the 28.2GHz frequency band.

[0108] The leaky coaxial cable 80 is arranged at the same position as the leaky coaxial cable 80 in Example 2 on both sides of the width direction of the production line, and connected to the antenna terminal of the base station. The orientation of the gap 83A is set so that the radio waves emitted from the gap 83A of the leaky coaxial cable 80 propagate toward multiple structures such as the production line, metal frame, AGV and other automated driving robots, and robotic arms.

[0109] When electromagnetic waves are emitted from the gap 83A of the leaky coaxial cable 80, the wave intensity in the dead zone changes from -110.0 dBm to -108.0 dBm, confirming an improvement of only +2.0 dB. Furthermore, the wave intensity outside the production line remains unchanged at -115.0 dBm. The location outside the production line is the same as the location on the back side of the electromagnetic wave reflecting device 60 in Examples 1-4.

[0110] Based on the experimental results of Examples 1 to 5, it can be confirmed that by installing both the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80, the blind zone in the production line can be reduced, and leakage of electromagnetic waves to the outside of the area where the electromagnetic wave reflecting device 60 and the leaky coaxial cable 80 are installed can be suppressed. Furthermore, it can be confirmed that when the leaky coaxial cable 80 is positioned on the reflecting surface of the electromagnetic wave reflecting device 60, the improvement in the electromagnetic wave intensity of the blind zone is greater compared to a position slightly above the upper end of the electromagnetic wave reflecting device 60.

[0111] <Effect>

[0112] The wireless transmission system 1 includes: a plurality of electromagnetic wave reflectors 60 disposed on both sides of the path along the direction of travel of the path, reflecting radio waves in a predetermined frequency band selected from a range of 1 MHz to 300 GHz; and a leaky coaxial cable 80 disposed in the area surrounded by the plurality of electromagnetic wave reflectors 60 disposed on both sides of the path and the ground of the path, and connected to the base station 33. Therefore, radio waves can be radiated along the path using the leaky coaxial cable 80. Furthermore, radio waves can be reflected by the electromagnetic wave reflectors 60 within the area surrounded by the plurality of electromagnetic wave reflectors 60 disposed on both sides of the path and the ground of the path, and leakage of radio waves outside the area can be suppressed.

[0113] Therefore, a wireless transmission system 1 is provided that can both improve the radio wave propagation environment and suppress radio wave leakage outside the necessary space.

[0114] Alternatively, the leaky coaxial cable 80 can be fixed to multiple electromagnetic wave reflecting devices 60. The leaky coaxial cable 80 can be easily arranged along the path using multiple electromagnetic wave reflecting devices 60. Furthermore, since electromagnetic waves can be radiated more reliably from the leaky coaxial cable 80 into the path, dead zones can be effectively reduced.

[0115] Alternatively, a canopy can be present in the area, from which the leaky coaxial cable 80 can be suspended. The leaky coaxial cable 80 can be easily arranged along the passage using the canopy. Furthermore, since radio waves can be radiated more reliably from the leaky coaxial cable 80 into the passage, dead zones can be effectively reduced.

[0116] Furthermore, the height of the leaky coaxial cable 80 can also be below the height of the upper ends of the multiple electromagnetic wave reflecting devices 60. Since more electromagnetic waves emitted from the leaky coaxial cable 80 are reflected within the area surrounded by the multiple electromagnetic wave reflecting devices 60 installed on both sides of the passage and the ground of the passage, the blind zone can be reduced more effectively, and the leakage of electromagnetic waves to areas outside the area can be suppressed.

[0117] In addition, the leaky coaxial cable 80 has multiple slits 83A for radiating electromagnetic waves, and these slits 83A can also be oriented towards the central side in the width direction of the passage. By propagating the electromagnetic waves radiated from the slits 83A within the area surrounded by multiple electromagnetic wave reflecting devices 60 disposed on both sides of the passage and the ground of the passage, the dead zone can be effectively reduced.

[0118] Furthermore, when the wavelength of the radio wave in free space is set as λ, and any natural number is set as N, the distance D between the multiple electromagnetic wave reflecting devices 60 and the leaky coaxial cable 80 can also be a distance that satisfies D≠(1 / 4+N)×λ. This can suppress the radio waves radiated from the gap 83A of the leaky coaxial cable 80 to the central side of the road 32 in the width direction from becoming out of phase with the radio waves reflected by the electromagnetic wave reflecting devices 60 to the central side of the road 32 in the width direction, thereby preventing the radio waves from canceling each other out.

[0119] Furthermore, the distance D between the multiple electromagnetic wave reflecting devices 60 and the leaky coaxial cable 80 can also be less than 0.3m. When the distance D is long, the intensity of the reflected wave that propagates from the leaky coaxial cable 80 to the center side of the road 32 in the width direction after being reflected by the electromagnetic wave reflecting devices 60 becomes lower. Therefore, by bringing the leaky coaxial cable 80 appropriately close to the electromagnetic wave reflecting devices 60, the intensity of the reflected wave becomes stronger, and the blind spot can be reduced.

[0120] In addition, the width of the passage can be 5m to 20m. In a passage with such a practical width, it is possible to both improve the radio wave propagation environment and suppress radio wave leakage outside the necessary space.

[0121] The above describes an exemplary wireless transmission system of this disclosure. However, this disclosure is not limited to the specific implementation method disclosed, and various modifications and alterations can be made without departing from the technical solution.

[0122] The following notes further disclose the above implementation methods.

[0123] (Note 1) A wireless transmission system, wherein,

[0124] include:

[0125] Multiple electromagnetic wave reflecting devices are arranged on both sides of the passage along its direction of travel, reflecting radio waves in a specified frequency band selected from a range of 1 MHz to 300 GHz; and

[0126] A leaky coaxial cable is configured in an area surrounded by multiple electromagnetic wave reflectors located on both sides of the aforementioned path and the ground surrounding the aforementioned path, and is connected to a base station.

[0127] (Appendix 2) According to the wireless transmission system described in Appendix 1, wherein,

[0128] The aforementioned leaky coaxial cable is fixed to the aforementioned multiple electromagnetic wave reflecting devices.

[0129] (Appendix 3) According to the wireless transmission system described in Appendix 1, wherein,

[0130] A canopy exists in the aforementioned area.

[0131] The aforementioned leaky coaxial cable is suspended from the aforementioned ceiling.

[0132] (Note 4) The wireless transmission system according to any one of Notes 1 to 3, wherein,

[0133] The height of the aforementioned leaky coaxial cable is below the height of the upper end of the aforementioned plurality of electromagnetic wave reflecting devices.

[0134] (Appendix 5) The wireless transmission system according to any one of Appendices 1 to 4, wherein,

[0135] The aforementioned leaky coaxial cable has multiple gaps that radiate electromagnetic waves.

[0136] The aforementioned multiple gaps are oriented toward the central side in the width direction of the aforementioned passage.

[0137] (Note 6) The wireless transmission system according to any one of Notes 1 to 5, wherein,

[0138] When the wavelength of the aforementioned electromagnetic wave in free space is set as λ, and any natural number is set as N, the distance D between the aforementioned multiple electromagnetic wave reflecting devices and the aforementioned leaky coaxial cable satisfies D≠(1 / 4+N)×λ.

[0139] (Note 7) The wireless transmission system according to any one of Notes 1 to 6, wherein,

[0140] The distance D between the aforementioned electromagnetic wave reflecting devices and the aforementioned leaky coaxial cable is less than 0.3m.

[0141] (Note 8) The wireless transmission system according to any one of Notes 1 to 7, wherein,

[0142] The width of the aforementioned passage is 5m to 20m.

[0143] Furthermore, this international application claims priority based on Japanese Patent Application No. 2023-194312, filed on November 15, 2023, the entire contents of which are incorporated herein by reference.

[0144] Explanation of reference numerals in the attached figures

[0145] 1... Wireless transmission system; 32... Road (an example of a pathway); 33... Base station; 35... Production line (an example of a pathway); 60... Electromagnetic wave reflector; 80... Leaky coaxial cable; 83A... Gap; 85... Fixture; 90... Support.

Claims

1. A wireless transmission system, in, include: Multiple electromagnetic wave reflecting devices are arranged on both sides of the passage along the direction of travel of the passage, and reflect electromagnetic waves in a specified frequency band selected from the range of 1MHz to 300GHz. and A leaky coaxial cable is configured within an area surrounded by multiple electromagnetic wave reflectors located on both sides of the passage and the ground of the passage, and is connected to a base station.

2. The wireless transmission system according to claim 1, wherein, The leaky coaxial cable is fixed to the plurality of electromagnetic wave reflecting devices.

3. The wireless transmission system according to claim 1, wherein, A canopy exists in the area. The leaky coaxial cable is suspended from the ceiling.

4. The wireless transmission system according to any one of claims 1 to 3, wherein, The height of the leaky coaxial cable is below the height of the upper end of the plurality of electromagnetic wave reflecting devices.

5. The wireless transmission system according to claim 1, wherein, The leaky coaxial cable has multiple slits that radiate electromagnetic waves. The plurality of slits are oriented toward the central side in the width direction of the passage.

6. The wireless transmission system according to claim 1, wherein, When the wavelength of the electromagnetic wave in free space is set as λ, and any natural number is set as N, the distance D between the plurality of electromagnetic wave reflecting devices and the leaky coaxial cable satisfies D≠(1 / 4+N)×λ.

7. The wireless transmission system according to claim 1, wherein, The distance D between the plurality of electromagnetic wave reflecting devices and the leaky coaxial cable is less than 0.3m.

8. The wireless transmission system according to claim 1, wherein, The width of the passage is 5m to 20m.

Images