JP7616970B2 - Antenna Device - Google Patents

Description

The present invention relates to an antenna device and a method for manufacturing an antenna device.

In the field of IoT (Internet of Things), where market expansion is expected, it is known that the LPWA (Low Power Wide Area) communication method is used (Non-Patent Document 1). In addition, radio waves such as LPWA, Wi-Fi (registered trademark), 5G, and 6G have high directivity and short communication distances, so it is desirable to install a large number of antennas.

In order to install a large number of antennas, it is desirable to attach antennas to existing structures, whether indoors or outdoors. When doing so, it is required that the aesthetic appearance of the structure is not marred by attaching the antennas to the structure. For this reason, glass antennas that have an inconspicuous appearance and can be retrofitted have been provided (Non-Patent Document 2).

In addition, a technology has been developed that embeds an antenna in a specially made iron manhole cover, preventing the antenna from being damaged by external forces and attaching it to the road surface so as not to impede vehicles (Non-Patent Document 3).

NTT West Japan, "Commercialization of LoRaWAN (registered trademark) for IoT business expansion," NTT Technical Journal, October 2018, pp.44-47 AGC, "AGC's 'glass antenna that turns windows into base stations' 5G compatible development completed", [online], [searched on July 5, 2021], Internet <URL: https://www.agc.com/news/detail/1200821_2148.html> Meidensha, "Manhole antenna for real-time monitoring of pipes", [online], [searched on July 5, 2021], Internet <URL: https://www.meidensha.co.jp/catalog/bb/BB524-3291.pdf>

However, when an antenna made of a brittle material such as the above-mentioned glass antenna is attached to a structure made of metal or reinforced concrete, the antenna cannot withstand an external force equivalent to that which the structure can withstand. For this reason, the antenna may be susceptible to damage even in a situation where the structure is not damaged by the external force. Therefore, when an antenna is attached to a structure, the antenna is required to have the same toughness as the structure to which it is attached. In addition, in order for the antenna to have the same toughness as the structure, the above-mentioned method of incorporating an antenna into a structure requires a high workload and is expensive.

In light of these circumstances, the objective of the present invention is to provide an antenna device and a method for manufacturing the antenna device that can have the same toughness as a structure while minimizing the high workload and high costs.

The antenna device according to one embodiment includes a first antenna section that is disposed at the entrance of a structure and is made of a metal plate with a slit hole formed therein, and a connection section that is a conductive member and has one end that is thinner than the side of the slit hole or other areas of the metal plate and is connected to an area that includes the slit hole.

A method for manufacturing an antenna device according to one embodiment includes the steps of forming a slit hole in a metal plate to be disposed in a structure, attaching one end of a cable to a conductive plate, and attaching the conductive plate to a side of the slit hole or to an area of the metal plate that is thinner than other areas and includes the slit hole.

The present invention aims to provide an antenna device and a method for manufacturing an antenna device that can reduce the workload while having the same toughness as a structure.

1 is a schematic diagram illustrating an example of an antenna device according to a first embodiment. FIG. 2 is a detailed view of the iron cover shown in FIG. 1 . FIG. 3 is a top view of the iron cover shown in FIG. 2 . FIG. 3 is a bottom view of the iron cover shown in FIG. 2 . FIG. 2 is a diagram showing a VSWR of the antenna device shown in FIG. 5 is a flowchart showing an example of a manufacturing method of the antenna device according to the first embodiment. FIG. 3 is a diagram showing a first modified example of a portion of the iron cover shown in FIG. 2 . FIG. 3 is a diagram showing a second modified example of a portion of the iron cover shown in FIG. 2 . FIG. 11 is a schematic diagram illustrating an example of an antenna device according to a second embodiment. 10 is a flowchart showing an example of a manufacturing method of the antenna device according to the second embodiment.

First Embodiment
Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

<Configuration of Antenna Device>
An example of the configuration of the antenna device 100 according to the first embodiment of the present invention will be described.

As shown in FIG. 1, the antenna device 100 transmits and receives electrical signals to and from the internal device 200. In this example, the antenna device 100 may transmit and receive electrical signals to and from the internal device 200 via wired communication.

The antenna device 100 also transmits and receives electrical signals to and from the external device 300 via wireless communication. In this example, the antenna device 100 transmits and receives electrical signals to and from the external device 300 via a wide area network such as LTE (Long Term Evolution) or LoRaWAN (Long Range Wide Area Network).

The internal device 200 is a communication device (first communication device) that includes a transceiver unit that receives an electrical signal transmitted from the antenna device 100 and transmits an electrical signal to the antenna device 100, a control unit that controls the electrical signal, a power source, etc. The internal device 200 is disposed on the interior S1 side of the structure.

The external device 300 is, for example, a communication device (second communication device) such as a server that manages various information acquired by the internal device 200. The external device 300 is disposed on the outside S2 side of the structure.

The structure in this embodiment is a structure for defining a space underground. The structure is, for example, a manhole 400 buried underground A. The structure is made of metal, concrete, resin concrete, or the like.

The manhole 400 comprises a neck 41, a housing 42, and an iron cover 43. The neck 41 and the housing 42 are formed, for example, from reinforced concrete. The neck 41 may be substantially cylindrical in shape, and the space defined by the neck 41 is in communication with the outside S2 of the structure. The housing 42 may be substantially rectangular in shape. Furthermore, the space defined by the neck 41 and the space defined by the housing 42 are in communication with each other.

The iron cover 43 is a member that covers the boundary (the entrance/exit of the manhole 400) between the space on the interior S1 side defined by the structure and the space on the exterior S2 side. In the example shown in FIG. 1, the iron cover 43 is disposed on the exterior S2 side of the neck 41. In one example, as shown in FIG. 2, the iron cover 43 includes a plate surface portion 431 having a plate surface shape. Also, as shown in FIGS. 3A and 3B, the surface of the plate surface portion 431 can be circular.

2, 3A, and 3B, the iron cover 43 may further include a protrusion 432 that is sufficiently smaller than the plate surface portion 431. The protrusion 432 is disposed on the surface of the plate surface portion 431, and may be disposed on both sides of the surface, or may be disposed on one side of the surface. Note that in FIGS. 3A and 3B, only some of the protrusions 432 are labeled with reference numerals, and the reference numerals of the other protrusions 432 are omitted.

For example, as shown in FIG. 3A, the iron cover 43 may have a plurality of substantially square protrusions 432a when viewed from the outside S2 side. The iron cover 43 may also have a substantially circular protrusion 432b when viewed from the outside S2 side. The iron cover 43 may also have a hole HL that penetrates the iron cover 43 and is sufficiently smaller than the iron cover 43.

Also, as shown in FIG. 3B, the iron lid 43 may have a protrusion 432 on the surface facing the interior S1. Specifically, the iron lid 43 may have two protrusions 432c extending in one direction (y-axis direction) and two protrusions 432d in a direction perpendicular to the one direction (x-axis direction) on the surface facing the interior S1. A lattice pattern may be formed by the two protrusions 432c extending in the x-axis direction and the two protrusions 432d extending in the y-axis direction. The lattice pattern is a member that supports the weight loaded on the iron lid 43 arranged in a structure.

The iron cover 43 has a slit hole SHL, which is a rectangular hole that penetrates the iron cover 43. When the current flowing around the slit hole SHL in the iron cover 43 changes, the magnetic field around the iron cover 43 changes, and the iron cover 43 transmits radio waves and functions as an antenna (corresponding to the antenna unit 11 described below).

The slit hole SHL has a rectangular shape when viewed from the normal direction (z-axis direction) of the surface of the iron cover 43. The slit hole SHL may be formed by cutting a metal plate in which the slit hole SHL is not formed, or the metal plate may be molded so that the slit hole SHL is formed.

The slit hole SHL may be formed in the deck portion of the iron cover 43. The deck portion is a portion that does not come into contact with other members when the iron cover 43 is placed on a structure. Since the impact on the strength of the deck portion is small, damage to the periphery of the slit hole SHL in the antenna portion 11 can be suppressed. In the example shown in Figures 2 and 3B, the deck portion is a portion where the protruding portions 432c and 432d that form the lattice structure of the iron cover 43 are not provided.

3A and 3B, the slit hole SHL may be formed at a position 5 mm or more away from the convex portion 432. Specifically, the slit hole SHL may be formed at a position 5 mm or more away from the convex portion 432 in the direction in which the long side of the slit hole SHL extends (y-axis direction) (5 mm in FIG. 3A, 7 mm in FIG. 3B), and may be formed at a position 5 mm or more away from the convex portion 432 in the direction in which the short side of the slit hole SHL extends (x-axis direction) (5 mm in FIG. 3A and FIG. 3B). The effect of the slit hole SHL being 5 mm or more away from the convex portion 432 will be described later with reference to FIG. 4.

Similarly, the slit hole SHL may be formed so as to be 5 mm or more away from the hole HL.

The size of the slit hole SHL can be a value according to the wavelength λ of the radio wave based on the electrical signal transmitted and received between the internal device 200 and the external device 300. For example, the length y_shl of the long side of the slit hole SHL can be 0.7λ or more and 0.8λ or less. The length x_shl of the short side of the slit hole SHL can be 0.02λ or more and 0.05λ or less. The height z1 of the slit hole SHL (see FIG. 2) can be 9 mm, for example, regardless of the wavelength λ. By forming the slit hole SHL sufficiently smaller than the iron cover 43, the strength of the iron cover 43 is little affected by the slit hole SHL.

The slits SHL may also be filled with an insulating material such as resin. This allows the antenna device 100 to prevent air, water, and the like from passing through the slits SHL. This allows the antenna device 100 to prevent rusting of the surface of the iron cover 43 that defines the slits SHL.

Furthermore, the slit hole SHL does not have to be filled with an insulating material such as resin. In such a configuration, the surface that defines the slit hole SHL in the iron cover 43 may be subjected to an anti-rust treatment. This allows the antenna device 100 to maintain breathability while preventing rust on the surface that defines the slit hole SHL in the iron cover 43.

The iron cover 43 may have multiple slit holes SHL formed. As a result, the periphery of each of the multiple slit holes SHL transmits multiple radio waves, and the iron cover 43 functions as an antenna that transmits multiple radio waves. This allows more radio waves to be transmitted per unit time than when only one slit hole SHL is formed, improving communication speed. Furthermore, by appropriately designing the positions and directions of the multiple slit holes SHL, the antenna device 100 can better control the directionality of radio waves based on the electrical signal transmitted from the iron cover 43. As a result, radio wave attenuation, which occurs significantly especially when relaying without power supply, can be suppressed.

The antenna device 100 includes an antenna section (first antenna section) 11 and a connection section 12.

The antenna unit 11 is constructed from a metal plate with a slit hole SHL formed therein, which is disposed at the entrance/exit of a structure. The metal plate can be, for example, the plate surface portion 431 of the iron cover 43 provided on the manhole 400 described above. When the current flowing around the slit hole SHL in the antenna unit 11 changes, the magnetic field around the antenna unit 11 changes, causing the antenna unit 11 to transmit radio waves. The antenna unit 11 can function as both an active antenna and a passive antenna.

In addition, a convex portion may be formed on the surface of the metal plate constituting the antenna unit 11. In the example described above in which the metal plate is the plate surface portion 431 of the iron lid 43, the convex portion formed on the surface of the metal plate is the convex portion 432 of the iron lid 43. Therefore, as explained with reference to the example of the iron lid 43, the slit hole SHL formed in the antenna unit 11 may be formed at a position 5 mm or more away from the convex portion on the surface of the metal plate constituting the antenna unit 11.

The connection part 12 is a conductive member, and one end of the connection part 12 is connected to the periphery of the slit hole SHL in the metal plate constituting the antenna part 11. In this example, the periphery of the slit hole SHL is the side surface of the slit hole SHL. The other end of the connection part 12 is connected to an internal device 200 that transmits and receives electrical signals. The connection part 12 includes a cable, which may be, for example, a coaxial cable 121. The connection part 12 may further include a conductive plate 122 to which one end of the cable is connected.

One end of the cable is connected to the periphery of a slit hole SHL in the metal plate that constitutes the antenna unit 11. In a configuration in which the cable is a coaxial cable 121, the coaxial cable 121 includes an inner conductor 121a and an outer conductor 121b that surrounds the periphery of the inner conductor 121a.

As shown in FIG. 2, one end of each of the internal conductor 121a and the external conductor 121b of the coaxial cable 121 is connected to the periphery of the slit hole SHL in the metal plate constituting the antenna section 11. Specifically, one end of the internal conductor 121a of the coaxial cable 121 is connected to one inner surface of the metal plate that defines the slit hole SHL. Also, one end of the external conductor 121b of the coaxial cable 121 is connected to the other inner surface of the metal plate that faces the one inner surface that defines the slit hole SHL. In the example shown in FIG. 2, as will be described in detail later, one end of each of the internal conductor 121a and the external conductor 121b is connected to the metal plate via a conductive plate 122 attached to the inner surface.

The coaxial cable 121 may be connected to the antenna section 11 by being bound by a binding member, or may be connected to the antenna section 11 by a crimping piece. This allows the connection section 12 to be firmly connected to the antenna section 11.

The length of the metal plate from the surface facing the outside S2 of the structure to the power supply point may be 1/2 or less of the thickness of the metal plate constituting the antenna unit 11. Here, the power supply point is the portion of the metal plate constituting the antenna unit 11 to which one end of the connection portion 12 is connected. Also, the "thickness" is the length in the direction perpendicular to the surface of the metal plate (z-axis direction). In the example shown in FIG. 2, the length of the metal plate from the surface facing the outside S2 of the structure to the power supply point corresponds to the length z2 of the iron cover 43 from the surface facing the outside S2 of the structure to the power supply point. The thickness of the metal plate constituting the antenna unit 11 corresponds to the thickness z1 of the iron cover 43.

The conductive plate 122 is a conductive member. One end of the coaxial cable 121 is attached to the conductive plate 122, and the conductive plate 122 is fixed to the antenna section 11. Specifically, the connection section 12 includes two conductive plates 122, and the inner conductor 121a of the coaxial cable 121 is attached to one conductive plate 122, and the outer conductor 121b of the coaxial cable 121 is attached to the other conductive plate 122. The conductive plate 122 is smaller than the antenna section 11, and therefore the difference in heat capacity between the conductive plate 122 and the coaxial cable is smaller than the difference in heat capacity between the antenna section 11 and the coaxial cable. Therefore, the coaxial cable 121 can be soldered to the conductive plate 122 more stably than when the coaxial cable 121 is directly soldered to the antenna section 11.

In one example, the conductive plate 122 may be fixed to the antenna unit 11 by a conductive adhesive. The conductive adhesive may be, for example, a conductive tape or a conductive adhesive. In this case, the conductive plate 122 may be attached to the antenna unit 11 by soldering, and then fixed to the antenna unit 11 by the conductive adhesive. In another example, the conductive plate 122 may be fixed by a crimp piece and then attached to the power supply point by soldering.

Here, the VSWR (Voltage Standing Wave Ratio) of the antenna device 100 described with reference to Figures 1 to 3B will be described with reference to Figure 4.

In FIG. 4, the VSWR (see solid line) is shown when the slit hole SHL is formed so that the distance to the convex portion 432 is 0 mm. Also, the VSWR (see dashed line) is shown when the slit hole SHL is formed so that the distance to the convex portion 432 is 1 mm. Also, the VSWR (see dashed line) is shown when the slit hole SHL is formed so that the distance to the convex portion 432 is 5 mm.

When the slit hole SHL is formed so that the distance to the convex portion 432 is 0 mm or 1 mm, the VSWR is greater than 2 in all frequency bands. In contrast, when the slit hole SHL is formed so that the distance to the convex portion 432 is 5 mm, the VSWR is less than 2 in the frequency band of 2.30 GHz or more and less than 2.58 GHz. In other words, when the slit hole SHL is formed so that the distance to the convex portion 432 is 5 mm, impedance matching is achieved in the frequency band of 2.30 GHz or more and less than 2.58 GHz. It was also found that when the slit hole SHL is formed so that the distance to the convex portion 432 is greater than 5 mm, the VSWR is less than 2 in the frequency band. Furthermore, it was also found that when the slit hole SHL is formed so that the distance to the hole HL is 5 mm or more, the VSWR is less than 2 in the frequency band. In this way, by forming the slit hole SHL so that the distance from the convex portion to the hole HL is 5 mm or more, the antenna device 100 can stably radiate radio waves and obtain necessary and sufficient communication characteristics.

<Method of manufacturing antenna device>
Here, a process for manufacturing the antenna device 100 according to the first embodiment will be described with reference to Fig. 5. Fig. 5 is a flowchart showing an example of a process for manufacturing the antenna device 100 according to the first embodiment. The process for manufacturing the antenna device 100 described with reference to Fig. 5 corresponds to an example of a method for manufacturing the antenna device 100 according to the first embodiment.

In step S1, slit holes SHL are formed in a metal plate to be disposed in a structure. Here, the slit holes SHL may be formed by cutting a metal plate in which no slit holes SHL are formed, or the metal plate may be shaped so that the slit holes SHL are formed. In this step, the cut portions of the metal plate that define the slit holes SHL may be polished.

In step S2, one end of the cable is attached to the conductive plate 122. As described above, in an example in which the cable is a coaxial cable 121, one end of the coaxial cable 121 is attached to the conductive plate 122. Specifically, the inner conductor 121a of the coaxial cable 121 is attached to one conductive plate 122, and the outer conductor 121b is attached to the other conductive plate 122.

In step S3, a conductive plate 122 is attached to the periphery of the slit hole SHL in the metal plate. The periphery of the slit hole SHL may be the side of the slit hole SHL. Specifically, one conductive plate 122 is attached to one power feed point in the antenna unit 11, and another conductive plate 122 is attached to another power feed point in the antenna unit 11. At this time, for example, the conductive plate 122 may be attached to the power feed point by soldering.

In step S4, the conductive plate 122 is fixed to the antenna unit 11. At this time, the conductive plate 122 may be fixed to the antenna unit 11 using, for example, a conductive adhesive.

The antenna device 100 manufactured in this manner can transmit and receive electrical signals to and from the internal device 200 by connecting the other end of the coaxial cable 121 to the internal device 200. The coaxial cable 121 may be connected to the internal device 200 via a connector, another cable, or the like. It can also transmit radio waves based on electrical signals received from the internal device 200 to the external device 300, or receive radio waves from the external device 300 and transmit electrical signals based on the radio waves to the internal device 200.

As described above, the antenna device 100 may not include the conductive plate 122. In such a configuration, in step S3, one end of the coaxial cable 121 may be connected to the antenna unit 11 instead of the conductive plate 122.

In addition, in the above-mentioned step S3, the conductive plate 122 is attached to the power supply point of the antenna unit 11 by soldering, and in step S4, the conductive plate 122 is fixed with a conductive adhesive, but this is not limited to the above. For example, in step S3, the conductive plate 122 may be fixed with a crimping piece, and in step S4, the conductive plate 122 may be attached to the power supply point by soldering.

As described above, the antenna device 100 according to the first embodiment includes an antenna section 11 that is configured from a metal plate with a slit hole SHL formed therein and that is disposed on a structure, and a connection section 12 that is a conductive member and has one end connected to the periphery of the slit hole SHL in the metal plate. This allows the antenna device 100 to have the same toughness as the structure while suppressing the workload.

In addition, in the antenna device 100 according to the first embodiment, the slit hole SHL is formed in the deck portion of the metal plate, which is a portion that does not contact the structure. This allows the antenna device 100 to have the same toughness as the structure.

In addition, in the antenna device 100 according to the first embodiment, the other end of the connection portion 12 is connected to an internal device 200 that transmits and receives electrical signals. This allows power to be directly supplied from the internal device 200 to the antenna portion 11, achieving high radio wave radiation characteristics.

In addition, in the antenna device 100 according to the first embodiment, a convex portion 432 is formed on the surface of the metal plate, and the slit hole SHL is formed at a position 5 mm or more away from the convex portion 432. This allows the antenna device 100 to achieve impedance matching.

In addition, in the antenna device 100 according to the first embodiment, the length of the metal plate from the surface facing the exterior S2 of the structure to the power supply point where one end of the connection portion 12 is connected to the metal plate is equal to or less than 1/2 the thickness z1 of the metal plate. This allows the antenna device 100 to reduce the effect of the metal plate on radio waves transmitted to the external device 300 disposed outside S2 of the structure.

The manufacturing method of the antenna device 100 according to the first embodiment includes the steps of forming a slit hole SHL in a metal plate to be disposed in the structure, attaching one end of the coaxial cable 121 to the conductive plate 122, and attaching the conductive plate 122 to the periphery of the slit hole SHL in the metal plate. This makes it possible to manufacture an antenna device 100 that has the same toughness as the structure while suppressing changes in the external shape of the metal plate used in the structure and without compromising strength.

(First Modification)
The metal plate constituting the antenna unit 11 may not have a constant thickness, unlike the metal plate of the above-mentioned embodiment. Here, the thickness is the length in the normal direction of the surface of the metal plate. Here, referring to FIG. 6A, the thickness in an example in which the metal plate is the plate surface portion 431-1 of the iron cover 43 will be described. The plate surface portion 431-1 shown in FIG. 6A is an example of a metal plate. For example, in the plate surface portion 431-1, the thickness z1 of the second region 431-1B can be 9 mm as an example. The thickness z2 of the first region 431-1A may be less than 1/2 the thickness z1 of the second region 431-1B. Furthermore, when the thickness z2 is in the range of 0.5 to 2.0 mm, the most stable transmission and reception is possible. The first region 431-1A is a region in which the slit hole SHL is formed. The second region 431-1B is a region located adjacent to the first region 431-1A in the direction of the short side of the slit hole SHL (x-axis direction). In this configuration, the connection portion 12 is a conductive member, and one end of the connection portion 12 is connected to the periphery of the slit hole SHL in the metal plate constituting the antenna unit 11. In this example, the periphery of the slit hole SHL is a region (first region 431-1A) that is thinner than other regions (second region 431-1B) in the metal plate and includes the slit hole SHL. Specifically, the conductive plate 122 is attached to the surface on the inside S1 side in the first region 431-1A, and one end of the coaxial cable 121 is attached to the conductive plate 122. At this time, the conductive plate 122 may be attached so that the distance from the surface on the outside S2 side of the antenna unit 11 to the power supply point is 1/2 or less of the thickness z1 of the second region 431-1B. In this modified example, in the above-mentioned step S3 in the process of manufacturing the antenna device 100, when attaching the conductive plate 122 around the slit hole SHL in the metal plate, the area around the slit hole SHL may be thinner than other areas (second area 431-1B) and may be an area (first area 431-1A) that includes the slit hole SHL.

(Second Modification)
The metal plate constituting the antenna unit 11 may not have a constant thickness, unlike the metal plate of the above-mentioned embodiment. Here, referring to FIG. 6B, the thickness in an example in which the metal plate is the plate surface portion 431-2 of the iron cover 43 will be described. The plate surface portion 431-2 shown in FIG. 6B is an example of a metal plate. For example, in the plate surface portion 431-2, the first region 431-2A has a tapered shape in which the thickness increases as it moves away from the slit hole SHL. Here, the first region 431-2A is a region in which the slit hole SHL with a thickness z2 is formed. The thickness z1 of the second region 431-2B is constant, and can be, for example, 9 mm. In addition, the thickness z2 may be less than 1/2 of the thickness z1. Furthermore, when the thickness z2 is in the range of 0.5 to 2.0 mm, the most stable transmission and reception is possible. Here, the second region 431-2B is a region located adjacent to the first region 431-2A in the direction of the short side of the slit hole SHL (x-axis direction). In this configuration, the connection portion 12 is a conductive member, and one end of the connection portion 12 is thinner than the other region (second region 431-2B) in the metal plate constituting the antenna unit 11, and is connected to the region (first region 431-2A) including the slit hole SHL. Specifically, the conductive plate 122 is attached to the tapered portion of the first region 431-2A, and one end of the coaxial cable 121 is attached to the conductive plate 122. At this time, the conductive plate 122 may be attached so that the distance from the surface on the outside S2 side of the antenna unit 11 to the power supply point is 1/2 or less of the thickness z1 of the second region 431-2B. In this modified example, in the above-mentioned step S3 in the process of manufacturing the antenna device 100, when attaching the conductive plate 122 around the slit hole SHL in the metal plate, the area around the slit hole SHL may be thinner than other areas (second area 431-1B) and may be an area (first area 431-1A) that includes the slit hole SHL.

<<Second embodiment>>
Hereinafter, a second embodiment of the present invention will be described in detail with reference to the drawings.

<Configuration of Antenna Device>
An example of the configuration of an antenna device 100-1 according to a second embodiment of the present invention will be described below. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 7, similar to the antenna device 100 of the first embodiment, the antenna device 100-1 transmits and receives electrical signals to and from the internal device 200, and transmits and receives electrical signals to and from the external device 300 via wireless communication. In this example, the antenna device 100-1 transmits and receives electrical signals to and from the internal device 200 via wireless communication. Also, similar to the antenna device 100 of the first embodiment, the antenna device 100-1 transmits and receives electrical signals to and from the external device 300 via a wide area network such as LTE or LoRaWAN.

The antenna device 100-1 comprises an antenna section (first antenna section) 11, a connection section 12-1, and a second antenna section 13.

The second antenna unit 13 is connected to the other end of the connection unit 12-1. The second antenna unit 13 is a member having an antenna function and can be a directional antenna. The second antenna unit 13 can include an internal substrate and a directional conductive pattern provided on the internal substrate. The internal substrate can be rectangular. The directional antenna can be, for example, a patch antenna.

The connection part 12-1 is a conductive member, and one end of the connection part 12-1 is connected to the periphery of the slit hole SHL in the metal plate that constitutes the antenna part 11. The other end of the connection part 12-1 is connected to the second antenna part 13. The connection part 12-1 includes a cable, which may be, for example, a coaxial cable 121. The connection part 12-1 may further include a conductive plate 122.

The second antenna unit 13 transmits radio waves to the internal device 200 based on the electrical signal received from the antenna unit 11 via the connection unit 12-1. The second antenna unit 13 also receives radio waves transmitted from the internal device 200, and transmits an electrical signal based on the radio waves to the antenna unit 11 via the connection unit 12-1.

<Method of manufacturing antenna device>
Here, a process for manufacturing the antenna device 100-1 according to the second embodiment will be described with reference to Fig. 8. Fig. 8 is a flowchart showing an example of a process for manufacturing the antenna device 100-1 according to the second embodiment. The process for manufacturing the antenna device 100-1 described with reference to Fig. 8 corresponds to an example of a method for manufacturing the antenna device 100-1 according to the second embodiment. Note that the same steps in the second embodiment as those in the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

First, as in the first embodiment, steps S1 to S4 are executed.

In step S5, the other end of the coaxial cable 121 is attached to the second antenna unit 13.

As described above, the antenna device 100-1 according to the second embodiment further includes a second antenna section 13, and the other end of the connection section 12-1 is connected to the second antenna section 13. This allows the antenna device 100-1 to transmit and receive electrical signals via wireless communication with the internal device 200, which is a radiation source disposed within the manhole 400.

<Other Modifications>
In this embodiment, a manhole 400 has been used as an example of a structure, but the structure is not limited to the manhole 400 and may be, for example, a handhole, a shield tunnel, a sludge storage tank, etc.

In this embodiment, an example has been described in which the metal plate is the plate surface portion 431 of the iron cover 43, but the metal plate is not limited to the plate surface portion 431 of the iron cover 43, and may be, for example, a member on a plate surface formed by a door or the like.

The present invention is not limited to the above-described embodiments and modifications. For example, the various processes described above may not only be executed in chronological order as described, but may also be executed in parallel or individually depending on the processing capacity of the device executing the processes or as necessary. In addition, appropriate modifications are possible without departing from the spirit of the present invention.

The above-described embodiments have been described as representative examples, but it will be apparent to those skilled in the art that many modifications and substitutions are possible within the spirit and scope of the present disclosure. Therefore, the present invention should not be construed as being limited by the above-described embodiments, and various modifications and changes are possible without departing from the scope of the claims.

11 Antenna section (first antenna section)
12, 12-1 Connection portion 13 Second antenna portion 41 Neck portion 42 Housing 43 Iron cover 100, 100-1 Antenna device 121 Coaxial cable 121a Inner conductor 121b Outer conductor 122 Conductive plate 200 Internal device 300 External device 400 Manhole 431, 431-1, 431-2 Plate surface portion 431-1A, 431-2A First region 431-1B, 431-2B Second region 432, 432a, 432b, 432c, 432d Convex portion

Claims (6)

a first antenna unit configured of a metal plate having a slit hole formed therein and disposed at an entrance of the structure;
a connection portion which is a conductive member and has one end which is thinner than a side surface of the slit hole or other areas of the metal plate and is connected to an area including the slit hole;
Equipped with
An antenna device, wherein the length of the metal plate from the surface facing the exterior of the structure to a feed point where one end of the connection portion is connected to the metal plate is equal to or less than 1/2 the thickness of the metal plate . The antenna device according to claim 1, wherein the slit hole is formed in a floor plate portion that is a portion that does not come into contact with other members when the metal plate is disposed in the structure. The antenna device according to claim 1 or 2, wherein the other end of the connection part is connected to an internal device that transmits and receives electrical signals. The antenna device according to claim 1 or 2, further comprising a second antenna part connected to the other end of the connection part. A protrusion is formed on a surface of the metal plate,
The antenna device according to claim 1 , wherein the slit hole is formed at a position 5 mm or more away from the protruding portion. The connection portion is
Cables and
a conductive plate to which one end of the cable is connected;
The antenna device according to claim 1 , wherein the conductive plate is fixed to the first antenna portion by a conductive adhesive.

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