Wireless transmission system

Abstract

The present invention provides a wireless transmission system that improves a communication environment by an electromagnetic wave reflecting device. The wireless transmission system includes a transmission antenna that transmits an electric wave of a prescribed frequency band selected from among frequencies of 1 GHz or more and 300 GHz or less, a reception antenna that receives an electric wave of the prescribed frequency band, and an electromagnetic wave reflecting device that forms a reflecting surface that reflects an electric wave of the prescribed frequency band. The electromagnetic wave reflecting device has a reflecting surface formed by one or more reflecting panels, and the reflecting surface is formed in such a manner that, when a distance from the transmission antenna to a reflection point on the reflecting surface is set as d1 [m], a distance from the reflection point to the reception antenna is set as d2 [m], and a wavelength of the prescribed frequency band is set as λ [m], a length L [m] of one side or a short side of the reflecting surface satisfies the following equation: L ≥ 2 × [λ • d1 • d2 / (d1 + d2)] 1／2 .

Description

Technical Field

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

[0002] The deployment of wireless base stations for both indoor and outdoor use is progressing, aiming to automate manufacturing processes and office work, enable remote operation, facilitate AI-based control and management, and enable autonomous driving. Beyond indoor locations such as factories, workshops, offices, and commercial facilities, and outdoor locations such as highways and railway lines, the deployment of wireless base stations is also underway or in the research phase in places where there is no clear distinction between indoor and outdoor environments, such as medical facilities and event venues.

[0003] The fifth-generation mobile communication standard (hereinafter referred to as "5G") provides a frequency band below 6 GHz, known as "sub-6", and a 28 GHz frequency band classified as millimeter wave. In the next-generation 6G mobile communication standard, it is expected to extend to the Asia-Pacific Hertz band. By using such high-frequency bands, the communication bandwidth will be significantly expanded, enabling large-scale data communication with low latency. A structure is proposed that configures an electromagnetic reflection device along at least a portion of the production line (e.g., see Patent Document 1).

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

[0005] The wireless communication environment of local area networks (LANs) in factories, workshops, and commercial facilities differs from that of public mobile communication networks. Within these facilities, mechanical structures and other obstacles hinder the propagation of communication waves, making it difficult to achieve high communication quality. Electromagnetic wave reflection devices are used as a method to improve the wireless communication environment within these facilities. Summary of the Invention

[0006] One of the objectives of this invention is to provide a wireless transmission system that improves the communication environment through an electromagnetic wave reflection device.

[0007] In one embodiment, the wireless transmission system includes: a transmitting antenna for transmitting radio waves in a predetermined frequency band selected from frequencies above 1 GHz and below 300 GHz; a receiving antenna for receiving radio waves in the frequency band; and an electromagnetic wave reflecting device for forming a reflecting surface that reflects the radio waves in the frequency band. The electromagnetic wave reflecting device has a reflecting surface formed by one or more reflecting panels. The distance from the transmitting antenna to a reflection point on the reflecting surface is denoted as d1 [m], the distance from the reflection point to the receiving antenna is denoted as d2 [m], and the wavelength of the frequency band is denoted as λ [m]. The reflecting surface is formed such that the length L [m] of one or the shorter side of the reflecting surface satisfies the following formula: L ≥ 2 × [λ•d1•d2 / (d1+d2)] 1／2 .

[0008] A wireless transmission system that improves the communication environment through electromagnetic wave reflection devices. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of an electromagnetic wave reflection device used in a wireless transmission system according to an embodiment.

[0010] Figure 2 This is a horizontal cross-sectional view of the frame that holds the reflective panel of the electromagnetic wave reflector.

[0011] Figure 3 This is a schematic diagram illustrating reflection at a reflective surface containing a metasurface.

[0012] Figure 4 This is a schematic diagram illustrating reflection at a specular reflective surface. Detailed Implementation

[0013] In this implementation, an electromagnetic wave reflecting device with a reflective surface of appropriate size is installed at an appropriate location or angle to improve the communication environment or radio wave environment of the wireless transmission system. Generally, electromagnetic waves below 3 THz are referred to as "radio waves," but in this specification, communication waves transmitted from a base station are sometimes referred to as "radio waves."

[0014] Hereinafter, the structure of the wireless transmission system according to the embodiments will be described with reference to the accompanying drawings. The following description is an example for embodying the technical concept of the present invention and does not limit the present invention. The size, positional relationship, etc. of the various components shown in the drawings are sometimes exaggerated for ease of understanding of the invention. In the following description, the same components or functions are labeled with the same names or reference numerals, and repeated descriptions are sometimes omitted.

[0015] <Wireless Transmission System>

[0016] Figure 1This is a schematic diagram of a wireless transmission system 1 according to an embodiment. The wireless transmission system 1 includes: a transmitting antenna 31 for transmitting electromagnetic waves in a predetermined frequency band selected from frequencies above 1 GHz and below 300 GHz; a receiving antenna 41 for receiving the electromagnetic waves transmitted from the transmitting antenna 31; and an electromagnetic wave reflecting device 60 for forming a reflecting surface 20 that reflects the electromagnetic waves of the aforementioned frequency band. When the distance from the transmitting antenna 31 to the reflection point on the reflecting surface 20 is defined as d1 [m], the distance from the reflection point to the receiving antenna 41 is defined as d2 [m], and the wavelength of the electromagnetic waves in the aforementioned frequency band is defined as λ [m],

[0017]

[0018] The reflective surface 20 is formed in such a way that the length L of one or the shorter side of the reflective surface 20 satisfies the above formula.

[0019] exist Figure 1 In the coordinate system, the surface on which the electromagnetic wave reflecting device 60 is set is designated as the XZ plane, and the height direction orthogonal to the XZ plane is designated as the Y direction. The X direction is the transverse or horizontal direction of the reflecting surface 20 of the electromagnetic wave reflecting device 60, and the Y direction is the longitudinal or vertical direction of the reflecting surface 20. The transmitting antenna 31 is, for example, the antenna of a transmitting station (Tx) such as a base station, and the receiving antenna 41 is the antenna of a receiving station (Rx) such as a mobile terminal. The radius R of the Fresnel band 5 of the electromagnetic wave radiated from the transmitting antenna 31 in the reflecting surface 20 is expressed by the following formula.

[0020]

[0021] Therefore, if the length L of one or the short side of the reflecting surface 20 is greater than or equal to the diameter (2R) of the Fresnel band 5, the electromagnetic wave reflecting device 60 will function.

[0022] The Fresnel zone refers to the range where the phase difference caused by the optical path length difference of electromagnetic waves is less than π. Electromagnetic waves passing through the Fresnel zone 5 reinforce and combine with each other. Even if there are obstacles within the line of sight (LOS) of the transmitting antenna 31 and the receiving antenna 41 connected by a straight line, wireless communication can be carried out between the transmitting antenna 31 and the receiving antenna 41 as long as there are no obstacles affecting the propagation of radio waves between the transmitting antenna 31 and the reflecting surface 20 of the electromagnetic wave reflecting device 60, and between the reflecting surface 20 and the receiving antenna 41.

[0023] The reflecting surface 20 of the electromagnetic wave reflecting device 60 does not necessarily have to be formed by a single reflecting panel; it can be formed by multiple reflecting panels. For example, by connecting reflecting panels 10-1, 10-2, and 10-3 (hereinafter, sometimes collectively referred to as "reflecting panels 10") with a frame 50, an electromagnetic wave reflecting device 60 with an expanded reflecting area can be obtained. As long as equation (1) is satisfied, multiple reflecting panels 10 can be connected to form the electromagnetic wave reflecting device 60, and a single reflecting panel 10 can also be used to form the electromagnetic wave reflecting device 60. The number of connected reflecting panels 10 is not limited to 3; it can be 2, or even 4 or more. The connection direction of the reflecting panels 10 is not limited to the horizontal or X-direction; multiple reflecting panels 10 can be connected along the longitudinal or Y-direction at a wall surface or the like. In the case of connecting the reflecting panels along the Y-direction, frames with the same structure as frame 50 can be used as the top frame 57 and the bottom frame 58. By enabling the reflective panel 10 to be connected with the frame 50, the size of the reflective surface 20 can be adjusted according to the environment in which the wireless transmission system 1 is introduced and the position of the transmitting antenna 31.

[0024] The transmitting antenna 31 has directivity and gain determined by the size, shape, and purpose of the space into which the base station is located. As an example, the maximum gain of the transmitting antenna 31 in the embodiment is 5 dBi or more, or 30 dBi. Electromagnetic waves radiated from the transmitting antenna 31 are reflected by the reflecting surface 20 of the electromagnetic wave reflecting device 60 and received by the receiving antenna 41. Even when the transmitting antenna 31 and the receiving antenna 41 are not present in the LOS, wireless communication between the transmitting antenna 31 and the receiving antenna 41 can be achieved by setting the electromagnetic wave reflecting device 60 in a manner that satisfies equation (1).

[0025] The electromagnetic wave reflecting device 60 has at least one reflecting panel 10 and a frame 50 for holding the reflecting panel 10. For example... Figure 1 As shown, when a reflective surface 20 of the required size is formed by multiple reflective panels 10-1, 10-2, and 10-3, the reflective panels 10-1, 10-2, and 10-3 can be connected by a frame 50. Each of the reflective panels 10 is capable of reflecting electromagnetic waves in the frequency band used in the wireless transmission system 1.

[0026] The reflecting surface 20 formed by one or more reflecting panels 10 includes at least one of a specular reflecting surface and a non-spectral reflecting surface. The specular reflecting surface reflects the incident electromagnetic wave at an angle equal to the angle of incidence. The non-spectral reflecting surface reflects the incident electromagnetic wave in a manner different from specular reflection. As a non-spectral reflecting surface, it may also be an artificial reflecting surface, i.e., a metasurface, whose reflection characteristics are controlled. The metasurface is formed by periodic structures or patterns finer than the wavelength, reflecting or diffusing the incident electromagnetic wave at an angle different from the angle of incidence. The metasurface can be designed to reflect electromagnetic waves in a specific direction or to reflect them in different diffusion modes.

[0027] The electromagnetic wave reflector 60 may also have legs 56 to stand independently on the mounting surface. The legs 56 may also be detachably connected to the frame 50. Lockable casters may be provided on the legs 56, allowing the electromagnetic wave reflector 60 to be moved and installed in a desired location. It may also be configured so that the legs 56 can be fixed to the mounting surface using screws or similar fasteners. Alternatively, the legs 56 may be omitted, and the electromagnetic wave reflector 60A may be mounted on a wall or ceiling. Figure 1 As shown, the upper and lower ends of the reflective panel 10 can also be held by a top frame 57 and a bottom frame 58 having the same structure as the frame 50, and connected in the Y direction, i.e., longitudinally.

[0028] When multiple reflective panels 10 are connected to form a reflective surface 20, the frame 50, top frame 57, and bottom frame 58 are formed of conductive or dielectric materials that do not significantly affect the reflective characteristics of the electromagnetic wave reflecting device 60. For example, they can be formed of conductive materials having electrical properties close to the reflective characteristics of the reflective panels 10. When the reflective panels 10 have a mirror-like reflective surface, from the viewpoint of ensuring continuity of the reflection potential between adjacent reflective panels 10, it is preferable that at least a portion of the frame 50 is formed of a conductive material; however, in the case of a metasurface, continuity of the reflection potential is not necessary. In this case, the frame 50 may also be made of a dielectric material capable of allowing electromagnetic waves of the used frequency to pass through.

[0029] Figure 2 It is along Figure 1 Example of a frame 50 with a horizontal cross-section cut along line A-A. This horizontal cross-section is a section in a plane parallel to the XZ plane. The frame 50 has a main body 500, for example, made of a conductor such as aluminum, slits 55-1 and 55-2 formed in the main body 500, and spaces 52-1 and 52-2 communicating with slits 55-1 and 55-2. Reflective panels 10-1 and 10-2 are inserted into and held in the slits 55-1 and 55-2 opposite each other in the X direction of the frame 50.

[0030] The reflective panel 10 has, for example, a conductive layer 11 serving as a reflective functional layer between two dielectric plates 12 and 13. The dielectric plates 12 and 13 are, for example, dielectric resin plates with a thickness of 1 mm or more and 8 mm or less. The conductive layer 11 is the surface of the reflective panel 10 that forms the reflective surface 20, and can be formed from a metal mesh, a periodic pattern, a geometric pattern, or a transparent conductive film. As an example, the conductive layer 11 comprises a metal mesh formed from good conductors such as Cu, Ni, SUS, and Ag. If a portion of the reflective panel 10 includes a metasurface, the conductive layer 11 may also include a pattern comprising a periodic arrangement of multiple metal elements. The conductive layer 11 has a thickness of 10 μm or more and 200 μm or less, preferably 50 μm or more and 150 μm or less, to fully function as a reflective surface that reflects electromagnetic waves of a target frequency in the designed direction.

[0031] Reflective panels 10-1 and 10-2 are inserted into slits 55-1 and 55-2 on both sides of the frame 50 in the X direction, and are held inside spaces 52-1 and 52-2, respectively. Although spaces 52-1 and 52-2 are not necessary, by setting spaces 52-1 and 52-2, the main body 500 of the frame 50 can be made lighter, and the holding angle of reflective panels 10-1 and 10-2 can be accommodating.

[0032] By inserting reflective panels 10-1 and 10-2 into slits 51-1 and 51-2 respectively, adjacent reflective panels 10-1 and 10-2 can be stably maintained. A portion of the main body 500 may also be formed of a non-conductive material. A non-conductive covering such as resin may also be provided on the outer surface of the main body 500.

[0033] Figure 3 This is a schematic diagram illustrating reflection at the reflective surface 20A, which includes a metasurface. Let d1 be the distance from the transmitting antenna 31 to the reflection point P on the reflective surface 20A, and d2 be the distance from the reflection point P to the receiving antenna 41. The reflective surface 20A, including the metasurface, constitutes a non-mirror reflective surface. If the incident angle is θi and the reflection angle is θr, then θi ≠ θr. Let θabn be the difference between the reflection angle during specular reflection and the reflection angle θr during non-mirror reflection.

[0034] exist Figure 3 In this example, for the sake of simplicity, the transmitting antenna 31 and the receiving antenna 41 are located on the same line parallel to the reflecting surface 20A on the XZ plane, but this is not limited to this example. The distance d1 from the transmitting antenna 31 to the reflection point P is represented by equation (2).

[0035]

[0036] Here, x is the distance between the transmitting antenna 31 and the normal at the reflection point P, and Wr is the length of the perpendicular line from the transmitting antenna 31 to the reflecting surface 20A.

[0037] On the other hand, the distance d2 from the reflection point P to the receiving antenna 41 is expressed by the reflection angle θr and by equation (3).

[0038]

[0039] Using the distances d1 and d2 obtained from equations (2) and (3) and the wavelength λ of the electromagnetic wave, the placement position of the electromagnetic wave reflecting device 60 and the size L of one or the shorter side are determined in a manner that satisfies equation (1). When the length Wr' of the perpendicular line from the receiving antenna 41 to the reflecting surface 20A differs from the length Wr of the perpendicular line from the transmitting antenna 31 to the reflecting surface 20A, d2 can be calculated using Wr' / cosθr. The length Wr' of the perpendicular line from the receiving antenna 41 to the reflecting surface 20A can be easily measured, and the reflection angle θr is predetermined based on the design of the metasurface. Alternatively, the distance d2 between the reflection point P and the receiving antenna 41 can be directly set within a specified range, such that the reflection point P is located at or near the center of the reflecting surface 20A.

[0040] Figure 4 This is a schematic diagram illustrating reflection at the reflecting surface 20B, which acts as a specular reflector. In the case of specular reflection, the incident angle θi and the reflection angle θr are the same (θi = θr). Figure 4 In the illustration, for ease of understanding, the transmitting antenna 31 and the receiving antenna 41 are arranged on the XZ plane on a line parallel to the reflecting surface 20B, but this is not limited to this example.

[0041] Regardless of Figure 3 In the case of non-specular reflection, or in Figure 4In the case of specular reflection, considering antenna gain and attenuation, the position and orientation of the electromagnetic wave reflecting device 60 can be determined such that the distance d1 from the transmitting antenna 31 to the reflection point P is longer than the distance d2 from the reflection point P to the receiving antenna 41 (d1 > d2). In this case, the electromagnetic wave reflecting device 60 is also assembled such that one side or the short side L of the reflecting surface 20 is 2R or more. When a wireless transmission system 1 using the electromagnetic wave reflecting device 60 is introduced into the facility, a reasonable range for the communication distance d1 + d2 between the transmitting antenna 31 and the receiving antenna 41 via the electromagnetic wave reflecting device 60 is, for example, longer than 0.3m and within 500.0m (0.3 < d1 + d2 ≤ 500.0m), preferably 0.5m or more and within 500m. When d1 + d2 is less than 0.3m, the possibility of obstacles between the transmitting antenna 31 and the receiving antenna 41 is low, and there is no necessity or significance for wireless communication via the electromagnetic wave reflecting device 60. When d1 + d2 exceeds 500.0m, although it still depends on the antenna gain, even with the electromagnetic wave reflecting device 60, the reflected wave is unlikely to reach the receiving antenna 41. From the viewpoint of improving reception quality, the dimension L (i.e., 2R) of one or the shorter side of the reflecting surface 20A or 20B of the electromagnetic wave reflecting device 60 is greater than 0.3m, preferably greater than 0.5m.

[0042] <Design Example of Wireless Transmission System>

[0043] The following is a design example of a wireless transmission system 1 using an electromagnetic wave reflecting device 60. In this design example, it is assumed that the receiving station Rx is in a blind zone where it is difficult to directly receive radio waves from the transmitting station Tx. The electromagnetic wave reflecting device is set up such that the reflection point of the radio waves radiated from the transmitting station Tx is located approximately at the center of the reflecting surface.

[0044] (Example 1)

[0045] Example 1 is Example 1. In the wireless transmission system 1, a frequency band of 28.0 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 10.7 mm. An electromagnetic wave reflecting device 60 is formed using a reflective panel 10 with specular reflection characteristics, measuring 1.0 m in width and 2.0 m in length. The dimensions of the reflective surface 20B are 1.0 m × 2.0 m. Based on the location of the transmitting station Tx, the electromagnetic wave reflecting device 60 is arranged such that the diameter 2R of the Fresnel band 5 is less than 1.0 m of the shorter side of the reflective surface 20B. The distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 50.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 25.0 m. The diameter 2R of the Fresnel band 5 is 0.84 m, which is less than 1.0 m of the shorter side of the reflective surface 20B of the electromagnetic wave reflecting device 60. Before and after the installation of the electromagnetic wave reflecting device 60, the received power in the receiving antenna 41 changed by +25dB, confirming that the reception quality was improved.

[0046] (Example 2)

[0047] Example 2 is Example 2. In the wireless transmission system 1, a frequency band of 28.0 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 10.7 mm. Five reflective panels 10 with specular reflection characteristics, each 1.0 m wide and 2.0 m long, are connected laterally (x-direction) to form a 5.0 m × 2.0 m reflective surface 20B. Based on the position of the transmitting station Tx, the electromagnetic wave reflecting device 60 is arranged such that the diameter 2R of the Fresnel band 5 is less than 2.0 m of the shorter side of the reflective surface 20B. The distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 75.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 25.0 m. The diameter 2R of the Fresnel band 5 is 0.90 m, which is smaller than the shorter side 2.0 m of the reflective surface 20B of the electromagnetic wave reflecting device 60. Before and after the installation of the electromagnetic wave reflecting device 60, the change in the received power in the receiving antenna 41 was +20dB, confirming that the reception quality was improved.

[0048] (Example 3)

[0049] Example 3 is Example 3. In the wireless transmission system 1, a frequency band of 28.0 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 10.7 mm. Fifty reflective panels 10 with specular reflection characteristics, each 1.0 m wide and 2.0 m long, are connected laterally (x-direction) to form a 50.0 m × 2.0 m reflective surface 20B. Based on the position of the transmitting station Tx, the electromagnetic wave reflecting device 60 is arranged such that the diameter 2R of the Fresnel band 5 is less than 2.0 m of the shorter side of the reflective surface 20B. The distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 400.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 100.0 m. The diameter 2R of the Fresnel band 5 is 1.85 m, which is smaller than the shorter side 2.0 m of the reflective surface 20B of the electromagnetic wave reflecting device 60. Before and after the installation of the electromagnetic wave reflecting device 60, the received power in the receiving antenna 41 changed by +10dB, confirming that the reception quality was improved.

[0050] (Example 4)

[0051] Example 4 is Example 4. In the wireless transmission system 1, a frequency band of 4.8 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 62.5 mm. Ten reflective panels 10 with specular reflection characteristics, each 1.0 m wide and 2.0 m long, are connected laterally (x-direction) to form a 10.0 m × 2.0 m reflective surface 20B. Based on the position of the transmitting station Tx, the electromagnetic wave reflecting device 60 is arranged such that the diameter 2R of the Fresnel band 5 is less than 10.0 m of the long side of the reflective surface 20B. The distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 300.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 200.0 m. The diameter 2R of the Fresnel band 5 is 5.48m, exceeding the short side (2.0m) of the reflector surface 20B of the electromagnetic wave reflector 60, but less than the long side (10.0m). Before and after the installation of the electromagnetic wave reflector 60, the received power in the receiving antenna 41 changes by +15dB, confirming an improvement in reception quality. If the diameter 2R of the Fresnel band is less than the long side of the reflector surface 20B, and the short side L of the reflector surface 20B covers an area radially from the center of the Fresnel band to more than 1 / 3 of its length, then the reception quality is further improved.

[0052] (Example 5)

[0053] Example 5 is Example 5. In the wireless transmission system 1, a 4.8 GHz frequency band is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 62.5 mm. Five reflective panels 10 with specular reflection characteristics, each 1.0 m wide and 2.0 m long, are connected laterally (x-direction) to form a 5.0 m × 2.0 m reflective surface 20B. Based on the position of the transmitting station Tx, the electromagnetic wave reflecting device 60 is arranged such that the diameter 2R of the Fresnel band 5 is less than or equal to the length of the long side of the reflective surface 20B (5.0 m). The distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 450.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 50.0 m. The diameter 2R of the Fresnel band 5 is 3.35 m, which exceeds the short side 2.0 m of the reflective surface 20B of the electromagnetic wave reflecting device 60 but is less than the long side 5.0 m. Before and after the installation of the electromagnetic wave reflecting device 60, the received power in the receiving antenna 41 changed by +7 dB, confirming an improvement in reception quality. This improvement is due to the fact that the diameter 2R of the Fresnel band is smaller than the long side of the reflecting surface 20B, and the short side L of the reflecting surface 20B covers approximately 60% of the area radially from the center of the Fresnel band.

[0054] (Example 6)

[0055] Example 6 is Example 6. In the wireless transmission system 1, a 4.8 GHz frequency band is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 62.5 mm. One hundred reflective panels 10 with specular reflection characteristics, each 1.0 m wide and 2.0 m long, are connected laterally (x-direction) to form a 100.0 m × 2.0 m reflective surface 20B. Based on the position of the transmitting station Tx, the electromagnetic wave reflecting device 60 is arranged such that the diameter 2R of the Fresnel band 5 is less than the length of the long side of the reflective surface 20B. The distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 450.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 50.0 m. The diameter 2R of the Fresnel band 5 is 3.35 m, which exceeds the short side 2.0 m of the reflective surface 20B of the electromagnetic wave reflecting device 60, but is less than the long side 100.0 m. Before and after the installation of the electromagnetic wave reflecting device 60, the received power in the receiving antenna 41 changed by +9 dB, confirming an improvement in reception quality. This improvement is due to the fact that the diameter 2R of the Fresnel band is smaller than the long side of the reflecting surface 20B, and the short side L of the reflecting surface 20B covers approximately 60% of the radial area from the center of the Fresnel band.

[0056] (Example 7)

[0057] Example 7 is Embodiment 7. In the wireless transmission system 1, a frequency band of 28.0 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 10.7 mm. An electromagnetic wave reflecting device 60 forms a reflecting surface 20A using a reflective panel 10 with a metasurface of 0.7 m in width and 0.7 m in height. The dimensions of the reflecting surface 20A are 0.7 m × 0.7 m. Based on the position of the transmitting station Tx, the electromagnetic wave reflecting device 60 is arranged such that the diameter 2R of the Fresnel band 5 is less than 0.7 m on one side of the reflecting surface 20A. The distance d1 from the transmitting antenna 31 to the reflection point on the reflecting surface 20A is 30.0 m, and the distance d2 from the reflection point to the receiving antenna 41, which is in a direction different from normal reflection, is 10.0 m. The diameter 2R of the Fresnel band 5 is 0.56 m, which is less than the length of one side of the reflecting surface 20A of the electromagnetic wave reflecting device 60, which is 0.7 m. Before and after the installation of the electromagnetic wave reflecting device 60, the change in the received power in the receiving antenna 41 was +12dB, confirming that the reception quality was improved.

[0058] (Example 8)

[0059] Example 8 is Example 8. In the wireless transmission system 1, a frequency band of 28.0 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 10.7 mm. Three metasurface reflective panels 10 with a horizontal dimension of 0.7 m and a vertical dimension of 0.7 m are connected along the X direction (lateral) and Y direction (longitudinal), forming a total of nine reflective panels 10 to form a 2.1 m × 2.1 m metasurface reflective surface 20A. Based on the position of the transmitting station Tx, the electromagnetic wave reflecting device 60 is set up in such a way that the diameter 2R of the Fresnel band 5 is less than 2.1 m, which is one side of the reflective surface 20A. The distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20A is 50.0 m, and the distance d2 from the reflection point to the receiving antenna 41, which is in a direction different from normal reflection, is 30.0 m. The diameter 2R of the Fresnel band 5 is 0.90m, which is smaller than the length of one side of the reflector surface 20A of the electromagnetic wave reflector 60, which is 2.1m. Before and after the installation of the electromagnetic wave reflector 60, the received power in the receiving antenna 41 changes by +10dB, confirming that the reception quality has been improved.

[0060] (Example 9)

[0061] Example 9 is a comparative example 1. In wireless transmission system 1, a 4.8 GHz frequency band is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 62.5 mm. Ten mirror-reflective panels 10, each 1.0 m wide and 2.0 m long, are connected along the X direction (lateral) to form a 10.0 m × 2.0 m reflective surface 20B. The electromagnetic wave reflecting device 60 is configured such that the distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 500.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 50.0 m. The diameter 2R of the Fresnel band 5 is 3.37 m, which is less than the length of the long side of the reflective surface 20B (10.0 m) but exceeds the length of the short side (2.0 m). Before and after the installation of the electromagnetic wave reflecting device 60, there was no significant change in the received power in the receiving antenna 41, and no improvement in reception quality was confirmed. Because the communication distance (d1+d2) via the electromagnetic wave reflecting device 60 is long, at 550m, especially the distance from the transmitting antenna 31 to the reflecting surface 20B, it is difficult to improve the reception quality even when using the electromagnetic wave reflecting device 60.

[0062] (Example 10)

[0063] Example 10 is a comparative example 2. In wireless transmission system 1, a frequency band of 28.0 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 10.7 mm. A 0.15 m × 0.15 m reflective surface 20B is formed using a mirror-reflective panel 10 with a width of 0.15 m and a height of 0.15 m. The electromagnetic wave reflecting device 60 is configured such that the distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 50.0 m, and the distance d2 from the reflection point to the receiving antenna 41 is 25.0 m. Before and after the installation of the electromagnetic wave reflecting device 60, there is no significant change in the received power in the receiving antenna 41, and no improvement in reception quality is confirmed. At this time, the diameter 2R of the Fresnel band 5 is 0.84 m, which is more than three times the size of one side of the reflective surface 20B of the electromagnetic wave reflecting device 60 (0.15 m), resulting in significant loss.

[0064] (Example 11)

[0065] Example 11 is a comparative example 3. In the wireless transmission system 1, a frequency band of 28.0 GHz is used. The maximum gain of the transmitting antenna 31 is 20 dBi, and the wavelength λ of the electromagnetic wave transmitted from the transmitting antenna 31 is 10.7 mm. A 0.3 m × 0.3 m reflective surface 20B is formed using a mirror-reflective panel 10 with a width of 0.3 m and a height of 0.3 m. The electromagnetic wave reflecting device 60 is configured such that the distance d1 from the transmitting antenna 31 to the reflection point on the reflective surface 20B is 0.2 m, and the distance d2 from the reflection point to the receiving antenna 41 is 0.1 m. Before and after the installation of the electromagnetic wave reflecting device 60, there was no significant change in the received power in the receiving antenna 41, and no improvement in reception quality was confirmed. The diameter 2R of the Fresnel band 5 is 0.05 m, which is smaller than the dimension of one side of the reflective surface 20B of the electromagnetic wave reflecting device 60 (0.3 m), but the distances d1 and d2 are too small. It is argued that the positions of the transmitting antenna 31 and the receiving antenna 41 are too close to the reflector 20B, leaving no room for obstructions to enter, thus resulting in no change in reception quality. Conversely, when the communication distance (d1+d2) is too small, there is no need to install the electromagnetic wave reflecting device 60. In addition, the diameter 2R of the Fresnel band on the reflector 20B is too small, making it difficult to effectively improve reception quality.

[0066] Based on the results of Examples 1 to 11, the following can be derived.

[0067] (1) As the actual configuration of the wireless transmission system 1 introduced into the facility, the distance d1 from the transmitting antenna 31 to the reflection point on the reflecting surface 20 is the same as or greater than the distance d2 from the reflection point to the receiving antenna 41, and the communication distance (d1+d2) via the electromagnetic wave reflection device 60 is preferably longer than 0.3m and less than 500.0m (0.3m<d1+d2≦500.0m).

[0068] (2) In the wireless transmission system 1 described above, the diameter 2R of the Fresnel band is preferably less than or equal to the length of one or the shorter side of the reflective surface 20.

[0069] (3) When the diameter 2R of the Fresnel band is smaller than the length of the long side of the reflector but exceeds the length of the short side, the reception quality is improved when the short side covers more than 1 / 3 of the area radially from the center of the Fresnel band. Conversely, the reception quality can be improved when the length of the long side of the reflector 20 is greater than or equal to the diameter of the Fresnel band, and the length of the short side of the reflector 20 is more than 1 / 3 of the diameter of the Fresnel band.

[0070] (4) As a dimension of the reflective surface 20 which helps to improve the reception quality, one side or the short side is preferably greater than 0.3m.

[0071] (5) The structures (1) to (4) above are applicable whether the reflective surface 20 is a metasurface or a specular reflective surface.

[0072] The wireless transmission system 1 of this embodiment can be applied not only to production lines in factories, but also to designated facilities or buildings such as commercial facilities, offices, and tunnels. The size of the reflective surface 20A or 20B of the electromagnetic wave reflecting device 60 can be appropriately adjusted using one or more reflective panels 10.

[0073] While the embodiments of this disclosure have been described above, this disclosure may include the following structures.

[0074] (Item 1) A wireless transmission system, wherein,

[0075] include:

[0076] A transmitting antenna that transmits radio waves in a specified frequency band selected from frequencies above 1 GHz and below 300 GHz;

[0077] A receiving antenna for receiving radio waves in the aforementioned frequency band; and

[0078] An electromagnetic wave reflecting device forms a reflecting surface that reflects electromagnetic waves in the aforementioned frequency band.

[0079] The aforementioned electromagnetic wave reflecting device has a reflecting surface formed by one or more reflecting panels.

[0080] When the distance from the transmitting antenna to the reflection point on the reflecting surface is set as d1 [m], the distance from the reflection point to the receiving antenna is set as d2 [m], and the wavelength of the frequency band is set as λ [m], the reflecting surface is formed such that the length L [m] of one or the shorter side of the reflecting surface satisfies the following formula:

[0081] L≥2×[λ·d1·d2 / (d1+d2)】 1／2 .

[0082] (Item 2) A wireless transmission system, wherein,

[0083] include:

[0084] A transmitting antenna that transmits radio waves in a specified frequency band selected from frequencies above 1 GHz and below 300 GHz;

[0085] A receiving antenna for receiving radio waves in the aforementioned frequency band; and

[0086] An electromagnetic wave reflecting device forms a reflecting surface that reflects electromagnetic waves in the aforementioned frequency band.

[0087] The aforementioned electromagnetic wave reflecting device has a reflecting surface formed by one or more reflecting panels.

[0088] When the distance from the transmitting antenna to the reflection point on the reflecting surface is denoted as d1 [m], the distance from the reflection point to the receiving antenna is denoted as d2 [m], and the wavelength of the frequency band is denoted as λ [m], the length of the long side of the reflecting surface is 2 × [λ•d1•d2 / (d1+d2)]. 1／2 The diameter of the Fresnel zone is greater than or equal to the diameter of the Fresnel zone, and the length of the short side of the aforementioned reflecting surface is more than 1 / 3 of the diameter of the Fresnel zone.

[0089] (Item 3) The wireless transmission system according to item 1 or 2, wherein,

[0090] The electromagnetic wave reflecting device described above has a frame that connects two or more reflecting panels along a first direction or a second direction different from the first direction, and the size of the reflecting surface can be adjusted.

[0091] (Item 4) The wireless transmission system according to Item 3, wherein,

[0092] The frame has a slit that connects the two or more reflective panels in the transverse or longitudinal direction.

[0093] (Item 5) The wireless transmission system according to any one of items 1 to 4, wherein,

[0094] The distance d1 from the transmitting antenna to the reflection point is the same as or greater than the distance d2 from the reflection point to the receiving antenna, and the sum of d1 and d2 exceeds 0.3m and is less than 500.0m.

[0095] (Item 6) The wireless transmission system according to any one of items 1 to 5, wherein,

[0096] The aforementioned reflective surface is a metasurface or a specular reflective surface.

[0097] Furthermore, this international application claims priority based on Japanese Patent Application No. 2023-193053, filed on November 13, 2023, the entire contents of which are incorporated herein by reference.

[0098] Explanation of reference numerals in the attached figures

[0099] 1... Wireless transmission system; 10, 10-1, 10-2, 10-3... Reflective panels; 20, 20A, 20B... Reflective surfaces; 31... Transmitting antenna; 41... Receiving antenna; 50... Frame; 57... Top frame; 58... Bottom frame; 60... Electromagnetic wave reflecting device; P... Reflection point; Tx... Transmitting station; Rx... Receiving station.

Claims

1. A wireless transmission system, in, include: A transmitting antenna that transmits radio waves in a specified frequency band selected from frequencies above 1 GHz and below 300 GHz; A receiving antenna for receiving radio waves in the stated frequency band; and An electromagnetic wave reflecting device that forms a reflecting surface that reflects electromagnetic waves in the stated frequency band. The electromagnetic wave reflecting device has a reflecting surface formed by one or more reflecting panels. When the distance from the transmitting antenna to the reflection point on the reflecting surface is d1, the distance from the reflection point to the receiving antenna is d2, and the wavelength of the frequency band is λ, the reflecting surface is formed such that the length L of one or the shorter side of the reflecting surface satisfies the following formula: L≥2×[λ•d1•d2 / (d1•d2)] 1／2 , The units of d1, d2, λ, and L are all in meters.

2. A wireless transmission system, in, include: A transmitting antenna that transmits radio waves in a specified frequency band selected from frequencies above 1 GHz and below 300 GHz; A receiving antenna for receiving radio waves in the stated frequency band; and An electromagnetic wave reflecting device that forms a reflecting surface that reflects electromagnetic waves in the stated frequency band. The electromagnetic wave reflecting device has a reflecting surface formed by one or more reflecting panels. When the distance from the transmitting antenna to the reflection point on the reflecting surface is denoted as d1, the distance from the reflection point to the receiving antenna is denoted as d2, and the wavelength of the frequency band is denoted as λ, the length of the long side of the reflecting surface is 2 × [λ•d1•d2 / (d1+d2)]. 1／2 The diameter of the Fresnel zone is greater than or equal to the diameter of the reflective surface, and the length of the short side of the reflective surface is greater than or equal to 1 / 3 of the diameter of the Fresnel zone, wherein the units of d1, d2, λ, and L are all meters.

3. The wireless transmission system according to claim 1 or 2, wherein, The electromagnetic wave reflecting device has a frame that connects two or more reflecting panels along a first direction or a second direction different from the first direction, and the size of the reflecting surface can be adjusted.

4. The wireless transmission system according to claim 3, wherein, The frame has a slit that connects the two or more reflective panels laterally or longitudinally along the reflective panels.

5. The wireless transmission system according to claim 1 or 2, wherein, The distance d1 from the transmitting antenna to the reflection point is the same as or greater than the distance d2 from the reflection point to the receiving antenna, and the sum of d1 and d2 exceeds 0.3m and is less than 500.0m.

6. The wireless transmission system according to claim 1 or 2, wherein, The reflecting surface is a metasurface or a specular reflecting surface.

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