JP7397774B2 - Unpowered relay device - Google Patents

Description

The present invention relates to a parasitic relay device.

Pipes, instruments, etc. are installed inside underground structures (radio wave shielded spaces) such as reinforced concrete manholes buried underground, but it is difficult to inspect them from the ground, so workers It is necessary to periodically enter the interior and inspect the installed equipment or the underground structure itself.
However, there may be toxic gases, stagnant water, etc. inside underground structures, and if there is an underground structure within a roadway, it is necessary to obtain permission to use the roadway. Preparation for holes is complicated. Therefore, in order to eliminate the need for entering holes into underground structures or to reduce the frequency of entering holes, measurement devices such as strain sensors, water level sensors, cameras, etc. are installed inside underground structures. A method of transmitting the obtained data to the outside of the underground structure is being considered (see, for example, Non-Patent Document 1).

When installing a measuring device inside an underground structure and transmitting data to the outside of the underground structure, Wi-Fi (
Transmission of data using high-frequency radio waves, such as those using radio waves (registered trademark), is limited to extremely short distances. In order to transmit high-frequency radio waves over long distances, installing repeaters to amplify signal strength requires power for each measuring device and repeater, so multiple power sources must be installed, or , the configuration becomes complicated, as it is necessary to install power distribution equipment from a single large-capacity power source to these devices.

Fujino et al., “Relay wireless technology that securely accommodates IoT terminals in areas where radio waves are difficult to reach,” NTT Technology Journal, July 2018 issue, pp. 15-18 (2018)

One possible method for performing simple radio wave relay is to turn off the relay device from a power source. However, if the relay device is powered off, radio waves cannot be amplified during relaying, so it is required for long-distance communication to reduce power loss during relaying.

It is an object of the present invention, made in view of the above circumstances, to provide a parasitic relay device that is capable of stably and efficiently performing long-distance wireless communication between a radio wave-shielded space and the outside, although it has a simple configuration. It's about doing.

The parasitic relay device according to one embodiment is a parasitic relay device that relays wireless communication between the inside of a radio wave shielding structure and the outside of the radio wave shielding structure, and is connected to the inside, and connects the internal board and the an internal antenna including a directional conductive pattern provided on an internal substrate; an external antenna connected to the outside and including a non-directional conductive pattern provided on an external substrate and the external substrate; The radio wave shielding structure includes a coaxial cable for connecting to an external antenna, and a connector attached to the coaxial cable and capable of separating the internal antenna and the external antenna , and the radio wave shielding structure is a manhole buried underground. The iron cover of the manhole is provided with a through hole capable of accommodating the parasitic relay device, and the external antenna is impedance matched with the iron cover .
Further, the parasitic relay device according to one embodiment is a parasitic relay device that relays wireless communication between the inside of a radio wave shielding structure and the outside of the radio wave shielding structure, and is connected to the inside and connected to an internal board. and an internal antenna including a directional conductive pattern provided on the internal substrate, an external antenna connected to the outside and including a non-directional conductive pattern provided on the external substrate and the external substrate, and the internal antenna. and a coaxial cable that connects the internal antenna and the external antenna, and a connector that is attached to the coaxial cable and is capable of separating the internal antenna and the external antenna, and the internal board and the external board have a center conductor on the surface. The coaxial cable is connected to the center conductor and the outer conductor on the back side, and the coaxial cable is characterized in that the tip is stripped off in steps and connected to the center conductor and the outer conductor.

According to the present invention, it is an object of the present invention to provide a parasitic relay device that is capable of stably and efficiently performing long-distance wireless communication between a radio wave shielded space and the outside, although it has a simple configuration.

1 is a diagram showing an example of the configuration of a parasitic relay device according to an embodiment of the present invention. 1 is a diagram showing an example of the configuration of a manhole iron cover in which a parasitic relay device according to an embodiment of the present invention is incorporated. 1 is a diagram showing an example of the configuration of an external antenna according to an embodiment of the present invention. It is a figure showing an example of VSWR (Voltage Standing Wave Ratio) in the case where there is no manhole iron cover. It is a figure which shows an example of VSWR when there is a manhole iron cover. It is a figure which shows an example of the structure of the external antenna based on a modification.

Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

<Unpowered relay device>
An example of the configuration of a parasitic relay device 100 according to an embodiment of the present invention will be described with reference to FIGS. 1 to 5.

Parasitic relay device 100 includes an internal antenna 10, an external antenna 20, a connection section 30,
Equipped with The connection section 30 includes a coaxial cable 31 and a connector 32. The parasitic relay device 100 is a device that does not require a power supply system, and relays wireless communication between an internal device 1000 provided inside a radio wave shielding structure and an external device 2000 provided outside the radio wave shielding structure.

The internal device 1000 is, for example, a strain sensor, a water level sensor, a camera, etc. that measures a predetermined location inside the radio wave shielding structure. The external device 2000 is, for example, a server that manages various information inside the radio wave shielding structure. The internal device 1000 and the external device 2000 communicate with each other via the parasitic relay device 100, for example, using LTE (Long Term Evolution).
n), connected by a wide area network such as LoRaWAN (Long Range Wide Area Network).

The radio wave shielding structure is made of a material that shields radio waves. Materials that shield radio waves include:
Examples include metal, concrete, and resin concrete. The inside of the radio wave shielding structure is a radio wave shielding space where radio waves are shielded. The outside of the radio wave shielding structure is a radio wave unshielded space where radio waves are not shielded. In addition, the radio wave shielded space or radio wave non-shielded space in this specification includes not only a space where radio waves are completely shielded or not completely shielded, but also a space where radio waves are substantially shielded or not substantially shielded. shall be included.

As shown in FIGS. 1 and 2, the radio wave shielding structure is, for example, a manhole 200 buried underground A. The interior _S1 of the manhole 200 is a radio wave shielding space. The outside _S2 of the manhole 200 is a radio wave-unshielded space.

The manhole 200 includes a neck 210, a casing 220, and an iron cover 230. Neck 2
10 and the housing 220 are made of reinforced concrete, for example. The neck portion 210 has a substantially cylindrical shape, and has a radio wave shielding space inside. The housing 220 has a substantially rectangular parallelepiped shape,
The interior is a radio wave shielding space. The iron cover 230 has a substantially cylindrical shape, is provided with a through hole (drain hole) C, and is arranged at the entrance and exit of the manhole 200. The parasitic relay device 100 has a shape that can be accommodated in the through hole C.

As _shown in FIG.
A first through-hole C ₁ and a second through-hole C ₂ are provided which communicate with the outside S ₂ . An operator passes the connecting part 30 through the first through hole _C1 and the second through hole _C2 , connects the coaxial cable 31 and the external antenna 20 via the connector 32 near the first through hole _C1 , Second through hole C
By connecting the coaxial cable 31 and the internal antenna 10 through the connector 32 near ₂ , the parasitic relay device 100 is incorporated into the iron lid 230. By incorporating the parasitic relay device 100 into the iron lid 230, the parasitic relay device 100 transmits the radio waves received from the internal device 1000 at the inside _S1 of the manhole 200 to the external device 2000 at the outside _S2 of the manhole 200.
It becomes possible to send to. As a result, the inside _S1 of the manhole 200 and the manhole 2
Long-distance wireless communication with the external _S2 of 00 becomes possible.

It is preferable that the length K of the connecting portion 30 is equal to or greater than the thickness T of the iron lid 230. For example, when the thickness T of the iron lid 230 is 46 mm, the length K of the connecting portion 30 is 46 mm or more, for example, 9 mm.
It is preferably about 2 mm.

The size of the through hole C should be at least large enough to allow the parasitic relay device 100 to be incorporated into the iron lid 230. For example, in the parasitic relay device 100, the width D ₁ of the internal antenna 10 is 50 mm, the width D ₂ of the external antenna 20 is 40 mm, the length K of the connection part 30 is 92 mm, and the width D ₃ of the connection part 30 is 6 mm. In this case, the height L of the first through hole _C1
1 is preferably approximately 17 mm, the distance L ₂ between the bottom surface of the first through hole C ₁ and the external antenna 20 is approximately 13 mm, and the width L ₃ of the second through hole C ₂ is preferably approximately 30 mm.

The internal antenna 10 is connected to the interior S ₁ of the manhole 200 . That is, the internal antenna 10 is a transmitting/receiving antenna that transmits and receives radio waves to and from the internal device 1000. internal antenna 1
0 is provided near one end of the through hole C in the iron lid 230.

Internal antenna 10 is preferably a directional antenna and includes an internal substrate and a directional conductive pattern provided on the internal substrate. Preferably, the internal substrate has a rectangular shape. Examples of the directional antenna include a patch antenna. It is preferable that the connection point of the patch antenna to the connection section 30 is set at a position shifted from the center of the patch. Thereby, the directivity of the patch antenna can be increased, so that the internal antenna 10 with excellent directivity can be realized.

For details on patch antennas, for example, the following documents can be referred to.
Susumu Miwa and Nobuyuki Kaku, co-author, "Antennas and Radio Wave Propagation", Tokyo Denki University Press, p.58,
1999

Since the internal antenna 10 is a directional antenna, the radio wave interference at the inside S ₁ of _the manhole 200 is reduced. It can be received with high efficiency. This allows the parasitic relay device 100 to transmit radio waves received from the internal device 1000 at the inside S ₁ of the manhole 200 to the external device 2000 at the outside S ₂ of the manhole 200 with high efficiency. Therefore, the internal device 1000 provided in the interior _S1 of the manhole 200 and the manhole 20
In wireless communication with the external device 2000 provided in the external S ₂ of 0, since attenuation of radio waves can be suppressed, it is possible to realize the parasitic relay device 100 capable of highly efficient long-distance wireless communication.

The external antenna 20 connects to the outside _S2 of the manhole 200. That is, the external antenna 20 is a transmitting/receiving antenna that transmits and receives radio waves to and from the external device 2000. external antenna 2
0 is provided near the other end side of the through hole C in the iron lid 230.

External antenna 20 is preferably an omnidirectional antenna, and includes an external substrate 21 and an omnidirectional conductive pattern 22 provided on external substrate 21. Examples of the omnidirectional antenna include a dipole antenna. By using a dipole antenna, it is possible to realize a parasitic relay device 100 that is capable of stable and efficient long-distance wireless communication no matter where the external device 2000 is located around the manhole 200.

For details on dipole antennas, for example, the following documents can be referred to.
Hiroaki Kogure, Yoshie Kogure, co-author, "Design and operation of small antennas", Seibundo Shinkosha, p.197, 2
009 Hideyuki Negiya, Maki Ogawa, co-author, "Antenna Design in the Ubiquitous Era", Tokyo Denki University Press, p.72, 2005

In the external antenna 20, as shown in FIG. 3, the external substrate 21 preferably has a circular shape concentric with the through hole C. Further, in the non-directional conductive pattern 22, the main portion 22a preferably has a meander shape, and the outer peripheral portion 22b preferably has an arc shape concentric with the through hole C. Moreover, it is preferable that the non-directional conductive pattern 22 includes a wide portion X at one tip of the outer peripheral portion 22b. In the non-directional conductive pattern 22, the main portion 22a
By having a meander shape, the external antenna 20 can be made smaller. In addition, in the non-directional conductive pattern 22, the outer peripheral part 22b has an arc shape concentric with the through hole C, so that electromagnetic coupling with the iron lid 230 is generated, and the external antenna 20 has an impedance with the iron lid 230. It becomes possible to match. In addition, since the external antenna 20 includes the wide portion X, it becomes possible to adjust the impedance. Therefore, the parasitic relay device 100 reduces power loss during relaying in long-distance communication, and can achieve high power consumption. It becomes possible to realize communication with

It is preferable that the non-directional conductive pattern 22 has a point-symmetrical structure as a whole. Regarding the point-symmetric structure of the non-directional conductive pattern 22, for example, the following literature can be referred to.
Paragraph 0012,0013 of JP2000-049525A
Paragraph 0026,0027 of Japanese Patent Application Publication No. 2000-013131

In the non-directional conductive pattern 22, the distance D between the outer circumferential portion 22b and the contour side of the through hole C is preferably set to approximately 1/4 wavelength of the frequency to which the external antenna 20 corresponds.
For example, the frequency of the external antenna 20 is 2.4 GHz (wavelength: 130 mm, 1/4 wavelength:
32.5 mm), "approximately 1/4 wavelength" refers to approximately 25 mm to 30 mm due to the influence of the wavelength shortening effect, although it depends on the shape of the non-directional conductive pattern 22. The distance D between the outer peripheral part 22b and the contour side of the through hole C is approximately 1 of the frequency that the external antenna 20 corresponds to.
/4 wavelength promotes resonance in the band used by the external antenna 20 due to electromagnetic coupling between the external antenna 20 and the iron cover 230, making it possible to contribute to impedance matching.

Note that in all parts of the outer peripheral part 22b, the distance D between the outer peripheral part 22b and the contour side of the through hole C does not have to be approximately 1/4 wavelength of the frequency that the external antenna 20 corresponds to; Furthermore, the external antenna 20 may deviate from approximately 1/4 wavelength of the corresponding frequency. Through hole C
This is because, as shown in FIG. 3, the shape is not uniformly circular, but has a rectangular cutout in part, so such a shape is allowed. Therefore, in principle, it is preferable that the distance D between the outer periphery 22b and the contour side of the through hole C be approximately 1/4 wavelength of the frequency that the external antenna 20 corresponds to. Specifically, the external antenna 20 may deviate from approximately 1/4 wavelength of the corresponding frequency.

Further, when the non-directional conductive pattern 22 is provided on the external substrate 21, the wavelength shortening effect due to the presence of the dielectric external substrate 21 causes the actual wavelength of the high-frequency signal flowing through the non-directional conductive pattern 22 to be shorter than the wavelength of Therefore, in consideration of the wavelength shortening effect, the distance D between the outer peripheral portion 22b and the contour side of the through hole C may be adjusted to be shorter than 1/4 wavelength.
The distance D between the outer peripheral portion 22b and the contour side of the through hole C set by such adjustment is also
It is treated as approximately 1/4 wavelength.

Here, the VSWR (Voltage St.
anding Wave Ratio (voltage standing wave ratio).

FIG. 4 is a diagram showing an example of VSWR in the case where the iron cover 230 of the manhole 200 is not provided. FIG. 5 is a diagram showing an example of VSWR in the case where the manhole 200 has an iron cover 230.

Comparing FIGS. 4 and 5, it can be seen that the peak of VSWR is shifted to the lower frequency side in the case where the iron cover 230 is present compared to the case where the iron cover 230 is not present. This suggests that appropriate electromagnetic coupling between the external antenna 20 and the iron cover 230 is effective, assuming that the frequency of the external antenna 20 is 2.4 GHz. This impedance matching is due to electromagnetic coupling of the outer peripheral part 22b of the omnidirectional conductive pattern 22 with the iron cover 230, suggesting that necessary and sufficient communication characteristics can be obtained by this impedance matching. .

The connecting portion 30 connects the internal antenna 10 and the external antenna 20. The connecting portion 30 is connected to the internal antenna 10 at one end, for example. The connecting portion 30 is connected to the external antenna 20 at the other end, for example. It is preferable that the connecting portion 30 corresponds to the frequency band of radio waves used in wireless communication between the internal device 1000 provided in the interior S ₁ of the manhole 200 and the external device 2000 provided in the exterior S ₂ of the manhole 200. .

The connecting portion 30 is provided in a through hole C in the iron lid 230. The length of the connecting part 30 is
It is preferable that the thickness is equal to or greater than the thickness of the iron lid 230 (see FIG. 2). Since the length of the connecting portion 30 has at least the thickness of the iron cover 230, the parasitic relay device 100 can efficiently transmit radio waves between the inside _S1 of the manhole 200 and the outside _S2 of the manhole 200. It becomes possible to relay the information.

The coaxial cable 31 is connected to the internal antenna 10 via the connector 32 at one end, and to the external antenna 20 via the connector 32 at the other end. A connector 32 is attached to the coaxial cable 31. The connector 32 separates the internal antenna 10 side from the external antenna 20 side. By attaching the connector 32 to the coaxial cable 31, retrofitting of the parasitic relay device 100 to the iron cover 230 becomes easy.

1 and 2, the connector 32 is attached to the side closer to the external antenna 20 as an example, but the connector 32 may be attached to the side closer to the internal antenna 10. Alternatively, it may be attached to the middle of the coaxial cable 31, or it may be attached to both sides of the side closer to the external antenna 20 and the side closer to the internal antenna 10.

The parasitic relay device 100 according to the present embodiment includes an internal antenna connected to the inside and including a directional conductive pattern provided on an internal board and an internal board, and an internal antenna connected to the outside and provided on an external board and an external board. The antenna includes an external antenna including a non-directional conductive pattern, a coaxial cable connecting the internal antenna and the external antenna, and a connector attached to the coaxial cable and capable of separating the internal antenna and the external antenna. According to this configuration, since a power supply system is not required, the configuration of the parasitic relay device 100 can be simplified. In addition, a bypass with low power loss for radio wave propagation can be formed in the iron cover 230 of the manhole 200, making wireless communication between the radio wave shielding space and the outside stable and highly efficient with a simple configuration that does not require a power source. It can be carried out. In addition, by attaching the connector 32 to the coaxial cable 31,
Since the internal antenna 10 and the external antenna 20 can be separated, the parasitic relay device 100 can be easily installed in the through hole C of the iron cover 230, and the parasitic relay device 100 can be easily installed in the through hole C of the iron cover 230. becomes easier. In addition, impedance matching is performed between the arc-shaped outer peripheral portion 22b of the non-directional conductive pattern 22 and the iron cover 230 of the manhole 200.
It is possible to realize relaying with low power loss due to stable oscillation. In addition, since the external antenna 20 has a structure in which the non-directional conductive pattern 22 is developed in a planar manner on the external substrate, impedance matching can be easily performed, and the overall structure of the external antenna 20 does not need to be enlarged. Antenna characteristics can be adjusted.

Therefore, by applying the parasitic relay device 100 according to the present embodiment to wireless communication between the internal device 1000 provided inside the radio wave shielding structure and the external device 2000 provided outside the radio wave shielding structure, simple Despite the configuration, it is possible to stably and efficiently perform long-distance wireless communication between the radio wave shielded space and the outside.

<Modified example>
In the external antenna 20, for example, as shown in _FIG . The configuration may be such that the conductive pattern (ground) _22S2 is connected to the external conductor 24. In this case, it is preferable that the tip of the coaxial cable 31 be stripped. Coaxial cable 31 is passed through a hole provided in external board 21 and connected to center conductor 23 and external conductor 24 . This makes it possible to realize a flat substrate in which no elements protrude from the substrate surface.

Since the external antenna 20 is installed in a manhole 200 installed outdoors, it is waterproofed during actual use.
Since there are no protrusions on the surface, waterproofing can be easily performed. In addition, the coaxial cable 31
can be connected perpendicularly to the external board 21 without protruding from the surface of the external board 21, so there is no need to provide a space on the external board 21 for routing the coaxial cable 31. This can contribute to miniaturization of the external antenna 20. Furthermore, when installing the external antenna 20 in the manhole 200, the coaxial cable 31 is connected to the manhole 200.
Since the coaxial cable 31 hangs down substantially in a straight line inside the manhole 200, a space can be secured between the coaxial cable 31 and the enclosure that constitutes the manhole 200, contributing to stable antenna resonance.

Note that the configuration shown in FIG. 6 is applicable not only to the external antenna 20 but also to the internal antenna 10.

<Other variations>
In this embodiment, a manhole is used as an example of a radio wave shielding structure, but the radio wave shielding structure is not limited to a manhole, and includes, for example, a handhole, a shield tunnel, a sludge storage It may also be a tank or the like.

In the present embodiment, the distance D between the outer circumferential portion 22b and the contour side of the through hole C is defined as approximately 1/4 wavelength of the frequency to which the external antenna 20 corresponds, but approximately 1/4 What is wavelength?
This does not necessarily mean 1/4 wavelength in a strict sense, and can be changed as appropriate depending on the environment in which the external antenna 20 is used. That is, it also includes errors for obtaining desired communication characteristics.

In this embodiment, a manhole 2 is used as a target structure to which the parasitic relay device 100 is attached.
Although the explanation is given using the iron lid 230 of No. 00 as an example, the target structure is not limited to the iron lid 230, and may be, for example, a door.

In this embodiment, as a component that connects the internal antenna 10 and the external antenna 20,
Although the coaxial cable 31 and connector 32 are described as an example, the internal antenna 10
The components connecting the external antenna 20 and the external antenna 20 are not limited to these.

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 process or as necessary. Other changes may be made as appropriate without departing from the spirit of the present invention.

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

10 Internal antenna 20 External antenna 30 Connection part 31 Coaxial cable 32 Connector 100 Parasitic relay device 200 Manhole (radio wave shielding structure)
210 Neck 220 Housing 230 Iron lid

Claims (5)

A parasitic relay device that relays wireless communication between the inside of a radio wave shielding structure and the outside of the radio wave shielding structure,
an internal antenna connected to the interior and including an internal substrate and a directional conductive pattern provided on the internal substrate;
an external antenna connected to the outside and including an external substrate and a non-directional conductive pattern provided on the external substrate;
a coaxial cable connecting the internal antenna and the external antenna;
a connector attached to the coaxial cable and capable of separating the internal antenna and the external antenna;
Equipped with
The radio wave shielding structure is a manhole buried underground,
The iron cover of the manhole is provided with a through hole that can accommodate the parasitic relay device,
The external antenna is a parasitic relay device that has impedance matching with the iron cover . The internal substrate has a rectangular shape,
The external substrate has a circular shape concentric with the through hole,
The outer periphery of the non-directional conductive pattern has an arc shape concentric with the through hole.
The parasitic relay device according to claim 1 . A parasitic relay device that relays wireless communication between the inside of a radio wave shielding structure and the outside of the radio wave shielding structure,
an internal antenna connected to the interior and including an internal substrate and a directional conductive pattern provided on the internal substrate;
an external antenna connected to the outside and including an external substrate and a non-directional conductive pattern provided on the external substrate;
a coaxial cable connecting the internal antenna and the external antenna;
a connector attached to the coaxial cable and capable of separating the internal antenna and the external antenna;
Equipped with
The internal substrate and the external substrate are connected to the center conductor on the front surface and connected to the external conductor on the back surface,
The coaxial cable is a parasitic relay device in which a tip of the coaxial cable is stripped and connected to the center conductor and the outer conductor. The internal antenna is a patch antenna,
the external antenna is a dipole antenna;
The parasitic relay device according to any one of claims 1 to 3 . The radio wave shielding structure is made of a material including metal and concrete or resin concrete.
The parasitic relay device according to any one of claims 1 to 4 .

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