JP2009147610A - Radio repeating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio repeating apparatus ensuring easier handling of a man-hole cover, not requiring complicated processes such as drilling of holes to the man-hole cover, and also ensuring easier design and installation work. <P>SOLUTION: The radio repeating apparatus is installed to an underground passage just under the man-hole cover 1 in order to intermediate transmission and reception of radio signals between the underground passage and area on the ground through reflection of the radio wave propagated in the underground passage. This radio repeating apparatus 1 is characterized in including a reflector 5 for reflecting the radio waves propagated through the underground passage to a radio wave transmitting structural material 2 around the man-hole cover 1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a wireless relay device useful for monitoring the state of underground communication equipment, power equipment, sewerage equipment, and the like. The manhole cover that is the subject of the present invention refers to a cover that directly covers the manhole that is a pit for workers to enter the underground or underground passage, but the present invention does not include workers. Since the present invention can also be applied to a cover placed on a hole, the manhole cover referred to in the present invention includes a handhole cover. Further, in this example, the underground buried object is described as a communication cable, but any of water and sewage pipes, gas pipes, and power cables may be used, and in these cases, the measurement items are water flow state, water quality, water leakage, gas leakage, Leakage, disconnection, etc.

  In order to provide high-speed and large-capacity communication information such as video distribution on the Internet to each home, an optical communication system using an optical fiber cable network buried in the ground has been put into practical use. The optical fiber cable buried in the ground is drawn out to the ground via a utility pole, and is drawn into an optical line terminator installed in each home via an aerial closure installed in the electric wire. Furthermore, it is used for transmission / reception of communication on the Internet network using an information terminal such as a personal computer connected to an optical line terminator.

  For inspection of communication equipment installed in the basement of such an optical communication system, workers regularly enter the manhole and carry out patrol inspections, but such inspection work is difficult and dangerous. Work. For this reason, in order to remotely monitor the state of underground communication facilities, etc., temperature sensors and inundation sensors are installed in the underground communication facilities, etc. A method for exchanging sensor information with the underground has been proposed. The following various methods have been proposed so far as radio relay apparatuses used for such applications.

(1) A wireless relay device that operates as a manhole cover itself as an antenna and is used for wireless connection with the ground (for example, “Transmission device used for monitoring device in human hole” in Patent Document 1).

  FIG. 11 is a detailed view of a lid structure having a conventional manhole cover itself as an antenna (this conventional example is intended to be applied to a manhole for underground transmission line monitoring. The ground opening of the hole has a double structure of a strong metal outer lid 34 and a metal inner lid 35 for preventing submersion).

  The reception relay antenna 31 is connected to the input end of the impedance matching circuit 32 and is installed on the lower surface side of the manhole cover 35. The length of the relay antenna 31 is set to a half wavelength of the radio signal.

  The impedance matching circuit 32 includes a capacitor C and an inductance L. The relay antenna fixed insulator 33 containing the impedance matching circuit 32 is fitted into a window 35a formed in the manhole inner cover 35 and penetrates the manhole inner cover 35 up and down, and its input end is the lower surface of the manhole inner cover 35. The output end protrudes to the upper surface side of the manhole inner lid 35. A capacitance forming electrode 36 is connected to the output end of the impedance matching circuit 32 protruding to the upper surface side of the manhole cover 35. The electrode 36 has a surface area of an appropriate size so as to form a capacitance 37 between the manhole outer lid 34 and the manhole outer lid 34 functions as an antenna by this capacitive coupling.

  The radio signal transmitted from the radio transmitter 38 installed in the manhole extracts the radio signal transmission power by the reception relay antenna 31, and the impedance matching circuit 32, the electrode 36 connected thereto, and the manhole outer cover Maximum power is supplied to the manhole outer lid 34 through the capacitance C between the lower surface of the manhole 34. Thereby, the manhole outer lid 34 functions as an antenna, and a radio signal is radiated to the ground.

  In this conventional example, the reception relay antenna 31 and the impedance matching circuit 32 are only installed in the manhole cover, and when the operator enters and exits the manhole, the manhole cover may be opened and closed. There is no. However, in this conventional example, since the manhole cover itself is used as an antenna, there is a problem that it is difficult to design such as impedance matching of the antenna. In addition, there is a problem that it is necessary to perform complicated processing such as making a hole in the manhole inner lid.

(2) A wireless relay device (for example, “slot antenna” in Patent Document 2) that is used for wireless connection with the ground by inserting a slot antenna into a hole such as a keyhole opened in a manhole cover and operating as a antenna.

  FIG. 12 shows the configuration of a slot antenna used in a conventional wireless relay device. The main body 41 is mounted in the keyhole 42 a provided in the manhole cover 42, and the slot 44 is filled in the conductor 43 forming the main body 41. Power is supplied to the slot antenna 45 from the manhole on the back surface of the main body 41. Since an existing hole such as a keyhole is used, a manhole or the like is not processed and an antenna that does not protrude from the manhole or the like can be formed. However, it is necessary to attach a feeding point and a feeding cable near the back of the manhole cover, and it is necessary to carefully open and close the lid so that the feeding cable is not damaged or disconnected in some cases. There is a problem that there is.

(3) A wireless relay device (for example, “manhole remote monitoring device” of Patent Document 3) that is used for wireless connection by installing an antenna near the hole on the back surface of the lid of an existing manhole to radiate electromagnetic waves to the ground.

  As shown in FIG. 13, an antenna that radiates electromagnetic waves from the back side of the manhole cover and a communication unit are installed in the vicinity of an existing manhole cover hole (for example, within 30 cm) to exchange electromagnetic waves with the mobile phone network on the ground. A wireless relay device in a sewer manhole is proposed. However, since the antenna is attached in the vicinity of the hole of the manhole cover, the operation of opening and closing the manhole cover becomes complicated and requires caution. In addition, since the signal from the communication unit is transmitted to the antenna provided on the manhole cover via the connection cable, there is a risk of corrosion or poor contact due to rain or muddy water entering the manhole. Furthermore, the metal thickness of the hole of the manhole cover is as thick as about several centimeters, and when the inner diameter of the hole is several centimeters or less, it can be electrically considered as a kind of circular metal waveguide. The waveguide has a characteristic of blocking an electromagnetic wave component below a specific frequency (referred to as a cutoff frequency Fc) determined by its inner diameter. For example, in the case of a cylindrical waveguide having an inner diameter of 25 cm, the cutoff frequency Fc is about 0.7 GHz, and the attenuation amount of the waveguide becomes infinite at a frequency lower than this (for example, “Gas Insulating Equipment” in Patent Document 4). (See Internal Abnormality Detection Device).

  Note that the cut-off frequency Fc increases as the inner diameter decreases. Therefore, although depending on the radio frequency to be used, it is desirable that the diameter of the hole of the manhole is several tens of centimeters or more, and if the inner diameter of the hole is several centimeters or less, the attenuation due to electromagnetic wave blocking is extremely large and the efficiency is low Has a point.

(4) A wireless relay that is installed in a manhole with an antenna that transmits and receives ground radio waves and an antenna that transmits and receives radio waves in the manhole, and a reflector is installed at a branch point in the manhole for wireless connection to the ground Device (for example, “Mobile communication system and wireless repeater” in Patent Document 5).

Referring to FIG. 14, a mobile station (MS) 61 is connected to a radio repeater (RPT) 62 by an antenna 79 via a radio line, and the radio repeater 62 is the same as the above in a sewer 73 by an antenna 70. A radio base station (BS) received by an antenna 70 via a frequency radio link
63 and a public telephone network 66 through a base station controller (BSC) 64 and a mobile communication switching center (MSC) 65.

  The radio repeater (RPT) 62 includes a radio transceiver and antenna for underground sewers, a radio transceiver and antenna for the mobile station 61 on the ground, a control unit, and the like. Since the radio frequency is transmitted and received at the same frequency to the mobile station 61 on the ground and the radio base station (BS) 63 in the sewer, it operates as a booster or a repeater.

  The wireless repeater 62 is incorporated in the manhole cover 75, performs wireless transmission / reception with the wireless base station by the transmission / reception antenna 70 in the sewer, and propagates in the sewer using the reflection plates 68 and 69 in the sewer. The vertical and horizontal dimensions of each of the reflection plates 68 and 69 in the sewer are configured by a length corresponding to one wavelength of the radio frequency propagating in the sewer 73.

  Even when the sewer 73 is a cylindrical drainage pipe and is bent at a right angle in a horizontal plane, or provided with a shunt or a synthetic path, the radio waves are sequentially reflected in one direction by the reflectors 68 and 69. Wireless transmission can be realized according to the piping.

  Conventionally, not so much propagation loss occurs in the sewer in the straight part, but when it is accompanied by branching or bending, the radio propagation loss becomes large and cannot be used. In this conventional example, in order to solve such problems, it is possible to secure the electric field strength in the bent sewer by placing a reflector at the branch point in the sewer. However, this conventional example has a problem that it is necessary to perform complicated processing such as making a hole in the manhole cover in order to attach the repeater.

(5) A wireless relay device that transmits radio waves from asphalt pavement or concrete pavement provided around the manhole and is used for wireless connection with the ground (for example, Non-Patent Document 1).

  FIG. 15 is a schematic view of a typical water supply manhole in which a conventional wireless relay device is installed, and an enlarged cross-sectional view showing a part of its structure. A water pipe 87 is buried in the soil (soil layer) 84, and a manhole is installed in association with the water pipe 87. The manhole secures a space inside by a concrete wall 83, and a manhole cover 81 is provided at the top. The asphalt layer or concrete layer 82 has a receiving ring 81b embedded and fixed, and the lid body 81a is held by the receiving ring 81b so as to be detachable or openable. Further, a water pipe air valve 86 is projected from the bottom of the concrete wall 83 into the internal space. The pressure, speed, and other data of the water to be distributed are acquired by a sensor (not shown) provided in connection with the piping. These data are transmitted to the ground via the underground wireless device 85, and information on the ground wireless device (not shown) is also transmitted to the underground wireless device 85. The radio device antenna 85a placed in the manhole is a rod-like λ / 4 (λ: wavelength) antenna with a reflector, and is arranged on the central axis of the manhole cover. The metal reflector 85b is attached for the purpose of suppressing the power absorbed by the soil by suppressing the primary radiation downward from the antenna and increasing the radiation power to the sky. The underground radio device 85 includes a λ / 4 antenna 85a, a metal reflector 85b, a radio case 85c, and a processing device 85d. The processing device 85d has a function of processing a signal from the above-described sensor or the like or sending a control signal or the like to other circuits, and is connected to a high-frequency transmission / reception circuit included in the wireless device case 85c. The position of the λ / 4 antenna 85a in the manhole is appropriately adjusted and set to a position where the efficiency of the radiated power to the ground space increases.

The radio wave emission characteristics depend on the following points.
1. 1. Geometric structure of underground structures such as manholes 2. Antenna structure, position and orientation Frequency (wavelength) of radio wave used
4). Dielectric properties of soil, concrete, asphalt, etc.

In this conventional example, it is possible to wirelessly connect an electronic device placed in an embedded structure and an electronic device placed on the ground by actively using radio waves that ooze out on the ground surface. However, the radio wave radiated from the antenna is reflected by the manhole cover, and a complicated electromagnetic field distribution is created in the manhole space. Therefore, there is a problem that it is necessary to predict radiation characteristics with high accuracy using complicated three-dimensional electromagnetic field numerical analysis.
Japanese Patent No. 2790975 Japanese Patent No. 3926677 Registered Utility Model No. 3061715 Japanese Patent No. 3302482 JP 2000-68912 A Mizuna Shizuo, Adachi Minoru, Watanabe Takashi, "Radiation from 430MHz antenna in manhole", 2007 General Conference Proceedings BS-5-4, IEICE, March 7, 2007, p. S-33 to S-34

In the conventional example (1), since the manhole cover itself is used as an antenna, there is a problem that it is difficult to design such as impedance matching of the antenna. In addition, there is a problem that it is necessary to perform complicated processing such as making a hole in the manhole inner lid.
In the conventional example (2), it is necessary to attach a feeding point and a feeding cable near the back of the manhole cover, and carefully open and close the lid so that the feeding cable is not damaged or disconnected in some cases. There is a problem that needs to be done.
In the conventional example (3), since the antenna is attached in the vicinity of the hole of the manhole cover, the opening / closing operation of the manhole cover becomes complicated and requires attention. Further, since the signal from the communication unit is transmitted to the antenna provided on the manhole cover via the connection cable, there is a possibility that it may be corroded by rain or muddy water entering the manhole or cause a connection failure. Furthermore, when the inner diameter of the manhole cover hole is several centimeters or less, there is a problem that the amount of attenuation due to blocking of electromagnetic waves is extremely large and the efficiency is poor.
In the conventional example (4), there is a problem that it is necessary to perform complicated processing such as making a hole in the manhole cover in order to attach the repeater.
In the conventional example (5), the radio wave radiated from the antenna is reflected by the manhole cover to create a complicated electromagnetic field distribution in the manhole space. Therefore, there is a problem that it is necessary to predict radiation characteristics with high accuracy using complicated three-dimensional electromagnetic field numerical analysis.

  In order to solve the above-described problems, the present invention provides a radio relay device that is easy to handle and manhole covers, and does not require complicated processing such as making holes in the manhole covers, and is easy to design and install. This is the issue.

  In order to solve the above-described problems, a wireless relay device of the present invention is installed in an underpass directly under a manhole cover, reflects a radio wave propagating through the underpass, and mediates transmission / reception of a radio signal between the basement and the ground The relay apparatus includes a reflector that reflects radio waves propagating through the underpass toward a radio wave transmitting structural material around the manhole cover. According to this configuration, the radio wave propagating in the manhole is reflected by the radio wave transmitting structural material by the reflector provided on the back side of the manhole cover and transmitted to the ground surface. Therefore, radio waves can be efficiently transmitted to the ground without forming a complicated electromagnetic field distribution in the manhole space. Further, since it is not necessary to provide an electric wiring such as a signal line between the manhole cover and the wireless communication device, there is no failure due to disconnection, and the manhole cover can be easily handled. Furthermore, since it is not necessary to provide a hole or the like for allowing radio waves to pass through the manhole cover, the design and construction are easy and the robustness of the manhole cover is not reduced.

  In the present invention, the reflector may be provided with a reflective surface having a triangular cross section or a trapezoidal cross section whose apex is directed toward the manhole cover. It is desirable that the inclination angle of the reflection surface (inclination angle with respect to the bottom surface of the reflector) is larger at the top than at the bottom of the reflector. The angle of inclination of the reflecting surface may change stepwise from the bottom to the top of the reflector (bent shape), or may change continuously from the bottom to the top of the reflector. Good (curved shape). Moreover, the shape provided with both the bending shape and the curve shape may be sufficient. When the inclination angle of the reflecting surface is changed in this way, the radio waves incident on the reflector are collected in a predetermined range around the manhole cover. Therefore, the transmission loss of radio waves can be minimized by setting the position where radio waves are concentrated to the thinnest part of the radio wave transmitting structural material around the manhole cover, for example.

  The shape of the reflector includes a cone, a pyramid, a triangular prism, and the like. In addition, a truncated cone, a truncated pyramid, a trapezoidal column, and the like obtained by cutting these tops are included. “Cone” includes an elliptical cone shape whose section cut by a plane parallel to the bottom surface is an ellipse, and “Pyramid” and “Triangular prism” include shapes whose corners and vertices are rounded. . The “cone” and “pyramid” include those in which the cone or pyramid bus is inclined at a constant angle with respect to the bottom surface, and the cone or pyramid bus is bent or curved (hereinafter referred to as “ Or “substantially cone” or “substantially pyramid”). Similarly, the “triangular prism” includes a shape in which two surfaces sandwiching the ridge line are bent or curved (hereinafter sometimes referred to as “substantially triangular prism”). Further, these shapes include a shape in which the inside is hollow and a shape in which the bottom is opened. In the present specification, a plate-like reflector may be referred to as a “reflecting plate”.

  In the present invention, it is preferable that the reflector has a conical or pyramidal reflecting surface whose apex is directed toward the manhole cover. According to this configuration, radio waves incident from all directions with respect to the reflector can be reflected in a desired direction.

  In the present invention, the reflector includes a substantially conical or substantially pyramidal reflective surface whose apex is directed to the manhole cover side, and an inclination angle of a generatrix with respect to a bottom surface of the reflective surface is a bottom portion of the reflective surface It is desirable that the reflecting surface be bent or curved so as to be larger at the top. In this case, the reflecting surface of the reflector is formed in a shape capable of collecting the radio waves reflected by the reflecting surface at a position where the radio wave transmitting structural material in the periphery of the manhole cover is thinnest. desirable. According to this configuration, radio waves incident from all directions with respect to the reflector can be efficiently transmitted to the ground.

  In the present invention, it is desirable that the center of the circumscribed circle of the manhole cover is disposed on the central axis of the reflecting surface. According to this configuration, radio waves can be radiated with a uniform distribution around the manhole cover. The radio wave radiation distribution is circular or polygonal around the manhole cover. For this reason, if the radius of the circle or polygon is approximately the same as the radius of the circumscribed circle of the manhole cover, the distance that the wave reflected by the reflector passes through before reaching the ground (the wave of asphalt, concrete, etc.) The distance that the radio wave propagates through the transmissive structural material is shortened, and the radio wave transmission loss is reduced.

  In the present invention, it is preferable that the reflector includes a triangular prism-like reflecting surface with a ridge line as a top portion directed toward the manhole cover. According to this configuration, a reflecting surface having an arbitrary size can be formed by changing the length of the triangular prism. In the case of a conical or pyramidal reflector, if the size of the underground passage is large, it is necessary to install a plurality of reflectors according to the width of the underground passage. Since the size of the reflecting surface is changed depending on the length, all the radio waves propagating in the underground passage can be reflected by one reflector.

  In the present invention, the reflector includes a substantially triangular prismatic reflecting surface with a ridge line at the top facing the manhole cover side, and an inclination angle of a side surface with respect to a bottom surface of the reflecting surface is lower than a bottom portion of the reflecting surface. It is desirable that the reflecting surface be bent or curved so as to be larger at the top. In this case, the reflecting surface of the reflector is formed in a shape capable of collecting the radio waves reflected by the reflecting surface at a position where the radio wave transmitting structural material in the periphery of the manhole cover is thinnest. desirable. According to this configuration, radio waves incident from all directions with respect to the reflector can be efficiently transmitted to the ground.

  In the present invention, it is desirable that the reflector is obtained by vapor-depositing or pasting a metal foil on the surface of a shape molded with a resin. Alternatively, the reflector is preferably constituted by a grid of metal wires or metal bars. Alternatively, it is desirable that the reflector has a mesh structure in which a large number of through holes are provided in a metal plate. According to these structures, a reflector can be reduced in weight and construction becomes simple.

  According to the present invention, it is possible to provide a wireless relay device that is easy to design and construct, which is easy to handle the manhole cover, does not require complicated processing such as making a hole in the manhole cover, and does not reduce robustness. can do. In addition, there is an effect that the radio wave can be transmitted over a wide range on the ground while reducing the transmission loss of the radio wave.

Embodiments according to the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram illustrating a configuration example of a wireless relay device that transmits radio waves from asphalt pavement or concrete pavement provided around a manhole according to the present invention and is used for wireless connection with the ground. An asphalt layer or a concrete layer 2 is laid on the upper surface of the soil (soil layer) 4 and a manhole is installed. The manhole secures a space inside by a concrete wall 3, and a manhole cover 1 is provided at the top. A conical or pyramid-shaped metal reflector 5 is provided in the underpass directly under the manhole cover 1 and is directed toward the manhole cover (or a wireless repeater incorporated therein) as in the conventional example of FIG. Instead of reflecting the radio wave, the radio wave is reflected toward the end of the manhole cover so that the radio wave can be diffused from the end of the manhole cover and put out on the ground. The state data such as the temperature of the communication equipment in the basement and the flooding are acquired by a temperature sensor, a flooding sensor, etc. (not shown). These data are transmitted as radio signals through the underground radio device 6 through the manhole, reflected by the reflecting plate 5, and transmitted through the asphalt layer or concrete layer 2 to the ground surface.

  The radio wave absorptivity of asphalt and concrete in the frequency band of several hundred MHz to several GHz is lower than that of soil. In other words, in the range of 300 MHz to 3 GHz, the dielectric loss is roughly in the order of soil, concrete, and asphalt. In particular, asphalt has a small dielectric loss and can be expected to transmit electromagnetic waves with practical strength if the thickness is about 10 cm to 30 cm (for example, Non-Patent Document 1). Therefore, it is possible to establish a wireless connection inside and outside the manhole by using radio waves that penetrate the asphalt or concrete pavement layer and ooze out to the ground surface. Even if there is no asphalt pavement or concrete pavement, radio waves ooze from the soil layer close to the ground surface. In this way, radio waves that ooze out on the ground surface can be actively used to wirelessly connect an underground radio device placed in a manhole and a radio device placed on the ground.

  The reflecting plate 5 includes a reflecting surface 5a having a triangular cross section whose apex is directed to the manhole cover 1 side. In the case of this configuration example, the reflection surface 5a is formed in a conical shape or a pyramid shape, and the generatrix of the reflection surface 5a is inclined at a constant angle with respect to the bottom surface of the cone or the pyramid. The reflecting plate 5 is disposed at a position overlapping the manhole cover 1 in a plane (position overlapping when viewed from the vertical direction). It is desirable that the inclination angle of the bus bar of the reflecting surface 5a is set to such a magnitude that all the radio waves propagating through the underground passage are reflected to the outside of the manhole cover 1. For example, when the radio wave propagates horizontally in the underground passage, the inclination angle of the bus is set to a value larger than 45 ° so that the radio wave incident near the apex of the reflecting surface 5a is reflected outside the manhole cover 1. It is desirable.

  In FIG. 1, a plurality of reflectors 5 having different heights are provided in the propagation direction of radio waves. The reflector 5 with a low height reflects the radio wave propagating through a low height, and the reflector 5 with a high height reflects the radio wave propagating through a high height.

  As shown in FIG. 2A, the central axis of the reflecting surface 5a (the axis that includes the apex of the cone or pyramid and is perpendicular to the bottom surface of the cone or pyramid) passes through the center of the circumscribed circle of the manhole cover 1. It is desirable. According to this configuration, the radio wave E <b> 1 can be emitted with a uniform distribution around the manhole cover 1. Further, as shown in FIG. 2B, when the cross section of the reflecting plate 5 taken along a plane passing through the central axis C of the reflecting surface 5a is viewed, the angle formed between the generatrix of the reflecting surface 5a and the central axis C is Desirably, it is less than 45 °. According to this configuration, the radio wave E1 incident perpendicularly to the manhole cover 1 is transmitted to the ground surface through the outer peripheral portion of the manhole cover 1.

  FIG. 3 is a diagram showing a variation of the reflecting plate 5. In the example of FIG. 3, the reflector having the same height as the reflector of FIG. 2 is arranged at a position shifted to the left from the center of the circumscribed circle of the manhole cover 1. In this example, in order to prevent the radio wave E2 reflected on the right side in the figure from being shielded by the manhole cover 1, the apex angle of the cone is sharper than that in the example of FIG. For this reason, the surface area of the reflecting plate 5 is reduced, and the intensity of the radio wave reflected by the reflecting plate 5 is weakened when installed in an underground passage.

  FIG. 4 is a diagram showing another variation of the reflecting plate 5. In the example of FIG. 4, the reflector having the same bottom area as the reflector of FIG. 2 is arranged at a position shifted to the left from the center of the circumcircle of the manhole cover 1. In this example, in order to prevent the radio wave E2 reflected on the right side in the figure from being shielded by the manhole cover 1, the apex angle of the cone is sharper than that in the example of FIG. For this reason, the height of the reflecting plate 5 increases, and there is a possibility that it cannot be accommodated in the manhole.

  In both examples of FIGS. 3 and 4, the radio wave E2 reflected on the left side of the drawing has a longer distance to propagate through a radio wave permeable structural material such as asphalt or concrete, and transmission loss increases. Therefore, in order to perform good wireless relay, it is desirable to match the central axis C of the reflector 5 with the center of the circumscribed circle of the manhole cover 1.

  Note that the size of the reflector 5 greatly depends on the wavelength of the radio wave used. That is, it is desirable that the length of the side surface of the reflecting plate 5 is at least ½ wavelength of the propagating radio wave, and preferably about 3 to 5 wavelengths so that a sufficient reflection effect is obtained with respect to the wavelength of the radio wave to be used. It is preferable (for example, refer to Japanese Patent No. 3395405 “Reflection Antenna”). In addition, when the length of the side surface of the reflecting plate 5 is set to an integral multiple of one wavelength of the propagation radio wave, the reflection efficiency can be improved by resonance (see, for example, Patent Document 5). As described above, the frequency of the radio wave that can be reflected is limited by the size of the reflector, and it is necessary to consider the actual size of the manhole cover when selecting the frequency of the radio wave to be used.

  In the conventional example shown in FIG. 14, the radio wave propagated in the sewer is reflected by the reflector toward the other reflector or the transmission / reception antenna in the sewer. Therefore, the radio wave reflected toward the transmitting / receiving antenna in the sewer is reflected by the manhole cover, and a complicated electromagnetic field distribution is created in the manhole space. In the conventional example shown in FIG. 15, the radio wave radiated from the antenna is reflected by the manhole cover, and similarly, a complicated electromagnetic field distribution is created in the manhole space. For this reason, there is a problem that it is necessary to predict radiation characteristics with high accuracy using complicated three-dimensional electromagnetic field numerical analysis. On the other hand, in the present invention, since the radio wave propagating in the manhole is directly reflected on the asphalt layer or the concrete layer 2 by the reflector 5 provided on the back surface of the manhole cover, it is transmitted to the ground surface. This has the effect of being able to communicate efficiently without using numerical analysis. Further, it is not necessary to provide an electric wiring such as a signal line between the manhole cover and the wireless communication device. For this reason, there is no need to worry about disconnection compared to the case where the wires are connected by electrical wiring, and the handling of the lid is facilitated. Further, the robustness of the manhole cover is not reduced.

  FIG. 5 is a diagram showing another configuration example of a wireless relay device that transmits radio waves from asphalt pavement or concrete pavement provided around a manhole according to the present invention and is used for wireless connection with the ground. An asphalt layer or a concrete layer 8 is laid on the upper surface of the soil (soil layer) 10 and a manhole is installed. The manhole secures a space inside by a concrete wall 9, and a manhole cover 7 is provided at the top. In the underpass directly under the manhole cover 7, a triangular prism-shaped metal reflector 11 is provided, and radio waves are directed toward the manhole cover (or a wireless repeater incorporated therein) as in the conventional example of FIG. Instead of reflecting, the radio wave is reflected toward the end of the manhole cover so that the radio wave can be diffused from the end of the manhole cover and put out on the ground. The state data such as the temperature of the communication equipment in the basement and the inundation are acquired by a temperature sensor, an inundation sensor, etc. (not shown). These data are transmitted as radio signals through the underground radio device 12 through the manhole, reflected by the reflecting plate 11, and transmitted to the ground surface through the asphalt layer or the concrete layer 8.

  The radio wave absorptivity of asphalt and concrete in the frequency band of several hundred MHz to several GHz is lower than that of soil. In other words, in the range of 300 MHz to 3 GHz, the dielectric loss is roughly in the order of soil, concrete, and asphalt. In particular, asphalt has a small dielectric loss and can be expected to transmit electromagnetic waves with practical strength if the thickness is about 10 cm to 30 cm (for example, Non-Patent Document 1). Therefore, it is possible to establish a wireless connection inside and outside the manhole by using radio waves that penetrate the asphalt or concrete pavement layer and ooze out to the ground surface. Even if there is no asphalt pavement or concrete pavement, radio waves ooze from the soil layer close to the ground surface. In this way, radio waves that ooze out on the ground surface can be actively used to wirelessly connect an underground radio device placed in a manhole and a radio device placed on the ground.

  The reflection plate 11 includes a reflection surface 11a having a triangular cross section in which a ridge line as a vertex is directed to the manhole cover 7 side. In the case of this configuration example, the reflecting surface 11a is formed in a triangular prism shape. The reflecting surface 11a includes two reflecting surfaces (side surfaces of the reflecting plate 11) intersecting via a ridge line portion serving as a vertex. The two reflecting surfaces sandwiching the ridge portion are inclined at a constant angle with respect to the bottom surface of the triangular prism. The reflection plate 11 is disposed at a position overlapping the manhole cover 7 in a plan view (position overlapping when viewed from the vertical direction).

  The center of the circumscribed circle of the manhole cover 7 is desirably arranged in a plane perpendicular to the bottom surface of the triangular prism including the top (ridge line) of the reflecting surface 11a. Thereby, a uniform radio wave distribution can be formed around the manhole cover 7. Further, it is desirable that the inclination angle of the side surface of the reflecting plate 11 is set to such a size that all the radio waves propagating in the underground passage are reflected to the outside of the manhole cover 7. For example, when the radio wave propagates horizontally in the underground passage, the side surface inclination angle is set to a value larger than 45 ° so that the radio wave incident near the apex of the reflecting surface 11a is reflected outside the manhole cover 7. It is desirable.

  In FIG. 5, a plurality of reflectors 11 having different heights are provided in the propagation direction of radio waves. The reflector 11 with a low height reflects a radio wave that propagates at a low position, and the reflector 11 with a high height reflects a radio wave that propagates at a high position.

  FIG. 6 is a plan view showing an example of installation of the reflector. FIG. 6A shows an example using a conical reflector, and FIG. 6B shows an example using a triangular prism-like reflector. 6 (a) and 6 (b), the reflector is viewed from the vertical direction, and concrete walls of the underground passage are provided on the left and right of the reflector.

  In the example of FIG. 6A, a plurality of reflectors 5A and 5B are provided in the width direction of the underpass. The radio wave E propagating on the left side of the underground passage is reflected by the reflector 5A provided on the left side of the underground passage, and the radio wave E propagating on the right side of the underground passage is reflected by the reflector 5B provided on the right side of the underground passage. Is done. In this configuration, by providing a plurality of reflectors in the width direction of the underpass, all the radio waves E propagating through the underpass can be reflected. However, for each of the reflectors, the center axis of the reflector and the center of the manhole cover do not coincide with each other, so the problem described with reference to FIGS. 3 and 4 occurs. Although it is conceivable to provide a single reflecting plate having a large bottom surface, if the bottom surface is enlarged, the height of the reflecting plate also increases. Therefore, in some cases, the reflecting plate may not be accommodated in the underground passage.

  On the other hand, in the example of FIG. 6B, a long reflector 11 is provided in the width direction of the underpass. The radio wave E propagating through the underpass is reflected by a single reflector 11. In this configuration, the center of the circumscribed circle of the manhole cover (not shown) is arranged in a plane perpendicular to the bottom surface of the triangular prism including the top (ridge line) of the reflecting surface 11a. Therefore, the problem as shown in FIGS. 3 and 4 does not occur. Further, in the case of a triangular prism-shaped reflector, the height of the top does not change even if the length of the triangular prism is increased, so that the problem that the reflector cannot be accommodated in the underground passage does not occur.

  Note that the size of the reflector 11 greatly depends on the wavelength of the radio wave used. That is, it is desirable that the length of the side surface of the reflecting plate 11 should be ½ wavelength or more of the propagation radio wave, and preferably about 3 to 5 wavelengths so that a sufficient reflection effect can be obtained with respect to the wavelength of the radio wave used. It is preferable (for example, refer to Japanese Patent No. 3395405 “Reflection Antenna”). In addition, when the length of the side surface of the reflecting plate 11 is set to an integral multiple of one wavelength of the propagation radio wave, the reflection efficiency can be improved by resonance (see, for example, Patent Document 5). As described above, the frequency of the radio wave that can be reflected is limited by the size of the reflector, and it is necessary to consider the actual size of the manhole cover when selecting the frequency of the radio wave to be used.

  In the conventional example shown in FIG. 14, the radio wave propagated in the sewer is reflected by the reflector toward the other reflector or the transmission / reception antenna in the sewer. Therefore, the radio wave reflected toward the transmitting / receiving antenna in the sewer is reflected by the manhole cover, and a complicated electromagnetic field distribution is created in the manhole space. In the conventional example shown in FIG. 15, the radio wave radiated from the antenna is reflected by the manhole cover, and similarly, a complicated electromagnetic field distribution is created in the manhole space. For this reason, there is a problem that it is necessary to predict radiation characteristics with high accuracy using complicated three-dimensional electromagnetic field numerical analysis. On the other hand, in the present invention, the radio wave propagating in the manhole is directly reflected on the asphalt layer or the concrete layer 8 by the reflector 11 provided on the back surface of the manhole cover and transmitted to the ground surface. This has the effect of being able to communicate efficiently without using numerical analysis. Further, it is not necessary to provide an electric wiring such as a signal line between the manhole cover and the wireless communication device. For this reason, there is no need to worry about disconnection compared to the case where the wires are connected by electrical wiring, and the handling of the lid is facilitated. Further, the robustness of the manhole cover is not reduced. Moreover, since the shape of the reflecting plate 11 is simplified as compared with the configuration of FIG. 1, there is an effect that processing and construction are facilitated.

  FIG. 7 is a diagram showing another configuration example of a wireless relay device that transmits radio waves from asphalt pavement or concrete pavement provided around a manhole according to the present invention and is used for wireless connection with the ground. An asphalt layer or a concrete layer 14 is laid on the upper surface of the soil (soil layer) 16 and a manhole is installed. The manhole secures a space inside by a concrete wall 15, and a manhole cover 13 is provided at the top. A conical or pyramid-shaped metal reflector 17 is provided in the underpass directly below the manhole cover 13 and is directed toward the manhole cover (or a wireless repeater incorporated therein) as in the conventional example of FIG. Instead of reflecting the radio wave, the radio wave is reflected toward the end of the manhole cover, and the shape of the side surface of the reflecting plate 17 is curved so that the radio wave can be diffused from the end of the manhole cover and put out on the ground. The state data such as the temperature of the communication equipment in the basement and the inundation are acquired by a temperature sensor, an inundation sensor, etc. (not shown). These data are transmitted as radio signals through the underground radio device 18 and propagate in the manhole, reflected by the reflector 17, and transmitted to the ground surface through the asphalt layer or the concrete layer 14.

  The radio wave absorptivity of asphalt and concrete in the frequency band of several hundred MHz to several GHz is lower than that of soil. In other words, in the range of 300 MHz to 3 GHz, the dielectric loss is roughly in the order of soil, concrete, and asphalt. In particular, asphalt has a small dielectric loss and can be expected to transmit electromagnetic waves with practical strength if the thickness is about 10 cm to 30 cm (for example, Non-Patent Document 1). Therefore, it is possible to establish a wireless connection inside and outside the manhole by using radio waves that penetrate the asphalt or concrete pavement layer and ooze out to the ground surface. Even if there is no asphalt pavement or concrete pavement, radio waves ooze from the soil layer close to the ground surface. In this way, radio waves that ooze out on the ground surface can be actively used to wirelessly connect an underground radio device placed in a manhole and a radio device placed on the ground. Further, in this configuration, the radio wave incident on the reflecting surface is concentrated once in a region near the manhole cover with a small transmission loss, and then expanded and reflected radially, so that the radio wave transmission loss can be reduced.

  The reflecting plate 17 includes a reflecting surface 17a having a triangular cross section whose apex is directed to the manhole cover 13 side. In the case of this configuration example, the reflecting surface 17a is formed in a substantially conical shape or a substantially pyramid shape. The reflecting surface 17a is curved so that the inclination angle of the generatrix (inclination angle with respect to the bottom of the cone or pyramid) is larger at the top than at the bottom of the reflecting plate. That is, as compared with a conical or pyramidal shape in which the bus bar is arranged at a fixed angle with respect to the bottom surface, the bus bar is curved toward the inside of the reflecting plate, and the radio wave incident on the bottom of the reflecting plate 17 is A radio wave reflected at an angle close to vertical and incident on the top of the reflector 17 is reflected at an angle close to horizontal. It is desirable that the central axis of the reflecting surface 17a (the axis that includes the apex of the cone or pyramid and is perpendicular to the bottom surface of the cone or pyramid) pass through the center of the circumscribed circle of the manhole cover 13. In FIG. 7, the generatrix of the reflecting surface 17a draws a smooth curve from the bottom to the top, but the inclination angle of the generatrix may change stepwise from the bottom to the top of the reflector 17 ( (Bending shape), and may change continuously from the bottom to the top of the reflector 17 (curved shape). Moreover, the shape provided with both the bending shape and the curve shape may be sufficient. In the case of this configuration example, the shape of the reflecting surface 17a is such that the radio waves reflected by the reflecting surface 17a can be concentrated at the position where the asphalt or concrete (radio wave transmitting structural material) around the manhole cover is the thinnest. In addition, the inclination angle of the bus is continuously increased from the bottom to the top of the reflecting plate 17.

  In FIG. 7, a plurality of reflectors 17 having different heights are provided in the propagation direction of radio waves. The reflector 17 having a low height reflects radio waves propagating at a low position, and the reflector 17 having a high height reflects radio waves propagating through a high position.

  Note that the size of the reflector 17 greatly depends on the wavelength of the radio wave used. That is, it is desirable that the length of the side surface of the reflecting plate 17 is not less than ½ wavelength of the propagating radio wave, and preferably about 3 to 5 wavelengths so that a sufficient reflection effect can be obtained with respect to the wavelength of the radio wave used. It is preferable (for example, refer to Japanese Patent No. 3395405 “Reflection Antenna”). In addition, when the length of the side surface of the reflecting plate 17 is set to an integral multiple of one wavelength of the propagation radio wave, the reflection efficiency can be improved by resonance (see, for example, Patent Document 5). As described above, the frequency of the radio wave that can be reflected is limited by the size of the reflector, and it is necessary to consider the actual size of the manhole cover when selecting the frequency of the radio wave to be used.

  In the conventional example shown in FIG. 14, the radio wave propagated in the sewer is reflected by the reflector toward the other reflector or the transmission / reception antenna in the sewer. Therefore, the radio wave reflected toward the transmitting / receiving antenna in the sewer is reflected by the manhole cover, and a complicated electromagnetic field distribution is created in the manhole space. In the conventional example shown in FIG. 15, the radio wave radiated from the antenna is reflected by the manhole cover to create a complicated electromagnetic field distribution in the manhole space. For this reason, there is a problem that it is necessary to predict radiation characteristics with high accuracy using complicated three-dimensional electromagnetic field numerical analysis. On the other hand, in the present invention, the radio wave propagating in the manhole is directly reflected on the asphalt layer or the concrete layer 14 by the reflector 17 provided on the back surface of the manhole cover and transmitted to the ground surface. This has the effect of being able to communicate efficiently without using numerical analysis. Further, it is not necessary to provide an electric wiring such as a signal line between the manhole cover and the wireless communication device. For this reason, there is no need to worry about disconnection compared to the case where the wires are connected by electrical wiring, and the handling of the lid is facilitated. Further, the robustness of the manhole cover is not reduced. In addition, since the shape of the side surface of the reflector 17 is curved as compared with the configuration of FIG. 1, a portion through which radio waves reach the ground (a concrete wall or soil (soil layer) of a manhole, an asphalt layer or a concrete layer) ) Has the effect of being able to transmit radio waves over a wide area on the ground, once the radio waves are concentrated near the end of the manhole cover where it becomes the smallest.

  FIG. 8 is a diagram showing another configuration example of a wireless relay device that transmits radio waves from asphalt pavement or concrete pavement provided around the manhole according to the present invention and is used for wireless connection with the ground. An asphalt layer or a concrete layer 22 is laid on the upper surface of the soil (soil layer) 24, and a manhole is installed. The manhole secures a space inside by a concrete wall 23, and a manhole cover 21 is provided at the top. An underpass directly below the manhole cover 21 is provided with a triangular prism-shaped metal reflector 25 having a curved side surface, and a manhole cover (or a wireless relay incorporated therein) as in the conventional example of FIG. Rather than reflecting the radio wave toward the device, the radio wave is reflected toward the end of the manhole cover, and the radio wave is diffused from the end of the manhole cover so that it can be emitted to the ground. The state data such as the temperature of the communication equipment in the basement and the inundation are acquired by a temperature sensor, an inundation sensor, etc. (not shown). These data are transmitted as radio signals through the underground radio device 26, propagated in the manhole, reflected by the reflector 25, and transmitted to the ground surface through the asphalt layer or concrete layer 22.

  The radio wave absorptivity of asphalt and concrete in the frequency band of several hundred MHz to several GHz is lower than that of soil. In other words, in the range of 300 MHz to 3 GHz, the dielectric loss is roughly in the order of soil, concrete, and asphalt. In particular, asphalt has a small dielectric loss and can be expected to transmit electromagnetic waves with practical strength if the thickness is about 10 cm to 30 cm (for example, Non-Patent Document 1). Therefore, it is possible to establish a wireless connection inside and outside the manhole by using radio waves that penetrate the asphalt or concrete pavement layer and ooze out to the ground surface. Even if there is no asphalt pavement or concrete pavement, radio waves ooze from the soil layer close to the ground surface. In this way, radio waves that ooze out on the ground surface can be actively used to wirelessly connect an underground radio device placed in a manhole and a radio device placed on the ground. Further, in this configuration, the radio wave incident on the reflecting surface is concentrated once in a region near the manhole cover with a small transmission loss, and then expanded and reflected radially, so that the radio wave transmission loss can be reduced.

  The reflecting plate 25 includes a reflecting surface 25a having a triangular cross section in which a ridge line serving as a vertex is directed to the manhole cover 21 side. In the case of this configuration example, the reflecting surface 25a is formed in a substantially triangular prism shape. The reflection surface 25a includes two reflection surfaces (side surfaces of the reflection plate 25) intersecting via a ridge line portion serving as a vertex. The two reflection surfaces sandwiching the ridge portion are curved so that the inclination angle of the reflection surface (inclination angle with respect to the bottom surface of the triangular prism) is larger at the top than at the bottom of the reflection plate. That is, the reflecting surface is bent or curved inside the reflecting plate as compared with the triangular prism shape in which the two reflecting surfaces (side surfaces of the triangular prism) are arranged at a fixed angle with respect to the bottom surface. The radio wave incident on the bottom is reflected at an angle close to vertical, and the radio wave incident on the top of the reflector 25 is reflected at an angle close to horizontal. The center of the circumscribed circle of the manhole cover 21 is desirably arranged in a plane perpendicular to the bottom surface of the triangular prism including the top (ridge line) of the reflecting surface 25a. In FIG. 8, the shape of the reflection surface 25 a is a smooth curve from the bottom to the top, but the inclination angle of the reflection surface 25 a may change stepwise from the bottom to the top of the reflection plate 25. It may be well (bent shape), and may change continuously from the bottom to the top of the reflector 25 (curved shape). Moreover, the shape provided with both the bending shape and the curve shape may be sufficient. In the case of this configuration example, the shape of the reflecting surface 25a is such that the radio waves reflected by the reflecting surface 25a can be concentrated at the position where the asphalt or concrete (radio wave transmitting structural material) around the manhole cover is the thinnest. In addition, the inclination angle of the reflecting surface continuously increases from the bottom to the top of the reflecting plate 25.

  In FIG. 8, a plurality of reflectors 25 having different heights are provided in the propagation direction of the radio wave. The reflector 25 with a low height reflects radio waves propagating at a low position, and the reflector 25 with a high height reflects radio waves propagating at a high position.

  Note that the size of the reflector 25 greatly depends on the wavelength of the radio wave used. That is, it is desirable that the length of the side surface of the reflecting plate 25 is not less than ½ wavelength of the propagating radio wave, and preferably about 3 to 5 wavelengths so that a sufficient reflection effect can be obtained with respect to the wavelength of the radio wave used. It is preferable (for example, refer to Japanese Patent No. 3395405 “Reflection Antenna”). In addition, when the length of the side surface of the reflecting plate 25 is set to an integral multiple of one wavelength of the propagation radio wave, the reflection efficiency can be improved by resonance (see, for example, Patent Document 5). As described above, the frequency of the radio wave that can be reflected is limited by the size of the reflector, and it is necessary to consider the actual size of the manhole cover when selecting the frequency of the radio wave to be used.

  In the conventional example shown in FIG. 14, the radio wave propagated in the sewer is reflected by the reflector toward the other reflector or the transmission / reception antenna in the sewer. Therefore, the radio wave reflected toward the transmitting / receiving antenna in the sewer is reflected by the manhole cover, and a complicated electromagnetic field distribution is created in the manhole space. In the conventional example shown in FIG. 15, the radio wave radiated from the antenna is reflected by the manhole cover to create a complicated electromagnetic field distribution in the manhole space. For this reason, there is a problem that it is necessary to predict radiation characteristics with high accuracy using complicated three-dimensional electromagnetic field numerical analysis. On the other hand, in the present invention, the radio wave propagating in the manhole is directly reflected on the asphalt layer or the concrete layer 22 by the reflector 25 provided on the back surface of the manhole cover and transmitted to the ground surface. This has the effect of being able to communicate efficiently without using numerical analysis. Further, it is not necessary to provide an electric wiring such as a signal line between the manhole cover and the wireless communication device. For this reason, there is no need to worry about disconnection compared to the case where the wires are connected by electrical wiring, and the handling of the lid is facilitated. Further, the robustness of the manhole cover is not reduced. Compared to the configuration of FIG. 5, the shape of the side surface of the reflector is curved, so that it passes through before the radio wave reaches the ground (manhole concrete wall, soil (soil layer), asphalt layer or concrete layer) The radio wave can be transmitted to the ground after being concentrated near the end of the manhole cover where the thickness is the thinnest, and the radio wave can be transmitted over a wide area on the ground.

  In the present embodiment, the case where soil (soil layer), asphalt layer or concrete layer is used as the radio wave transmitting structural material has been described. However, other dielectric materials such as rubber and plastic (synthetic resin) are used. It may be used. For example, by covering the rubber around the manhole cover with a buffer material, radio waves can be efficiently transmitted from the rubber.

  In this embodiment, the case where a metal plate is used as the reflector is described. However, for example, a metal foil is vapor-deposited or pasted on the surface of a shape molded with a resin such as rubber or plastic (synthetic resin). It may be a thing. In this case, the effect that the reflector can be reduced in weight, construction is simple, and cost reduction can be achieved.

  The shape of the reflector is not limited to a plate-like shape (reflecting plate), and may be a block-like shape. The reflector is not limited to a triangular cross section, and may be a trapezoidal cross section. In the present embodiment, the shape of the reflector is a cone, a pyramid, a triangular prism, or the like. However, a truncated cone, a truncated pyramid, a trapezoidal column, or the like having a truncated top in these shapes may be employed. Here, the “cone” includes an elliptical cone shape whose section cut by a plane parallel to the bottom surface is an ellipse, and the “pyramid” and “triangular prism” have rounded corners and apexes. Is included. In addition to “cones” and “pyramids”, the cones and pyramid buses are inclined at a fixed angle with respect to the bottom, and the cones and pyramid buses are pointed so that the apexes of the cones and pyramids are sharp. , Inwardly bent or curved ("substantially conical" or "substantially pyramid"). Similarly, the “triangular prism” includes a shape (“substantially triangular prism”) in which two surfaces sandwiching the ridge line are bent or curved inward so that the ridge line portion serving as the apex is sharply pointed. Further, these shapes include a shape in which the inside is hollow and a shape in which the bottom is opened.

  Moreover, although the case where the metal plate was used as a reflector was described in this embodiment, you may be comprised by the grid of a metal wire or a metal bar. The grid may be one in which metal wires or metal bars are arranged in a stripe shape, or may be arranged in a lattice shape. For example, in FIG. 9, the conical reflector 105 is formed by a plurality of metal wires 106, and in FIG. 10, the triangular prism-shaped reflector 107 is formed by a plurality of metal bars 108. In these examples, a reflective surface that reflects radio waves is formed by a plurality of metal wires or metal bars knitted in a lattice shape. In this case, the effect that the reflector can be reduced in weight, construction is simple, and cost reduction can be achieved. If the grid pitch (interval between metal wires or metal rods) is set to about 1/10 or less of the wavelength of the radio wave used, reflection loss can be prevented. Or you may be comprised by the mesh structure which provided many through-holes in the metal board as a reflector. Also in this case, the effect that the reflector can be reduced in weight and the construction is simple is obtained. The through-hole that is a mesh may be triangular, square, or circular. If one side of the mesh is set to about one-tenth or less of the wavelength of the used radio wave, reflection loss can be prevented (see, for example, “radio wave reflector” in Japanese Patent Laid-Open No. 8-37417).

  In the present embodiment, the wireless relay device is configured by the reflector. However, in addition to the reflector, a configuration such as a signal amplifier that amplifies the signal intensity may be added as necessary.

It is a schematic block diagram of the radio relay apparatus concerning one Embodiment of this invention. It is a figure which shows the example of installation of a reflecting plate. It is explanatory drawing of the other example of installation of a reflecting plate. It is explanatory drawing of the other example of installation of a reflecting plate. It is a schematic block diagram of the radio relay apparatus which concerns on the other structural example of this invention. It is explanatory drawing of the other example of installation of a reflecting plate. It is a schematic block diagram of the radio relay apparatus which concerns on the other structural example of this invention. It is a schematic block diagram of the radio relay apparatus which concerns on the other structural example of this invention. It is explanatory drawing of the modification of the radio relay apparatus of this invention. It is explanatory drawing of the modification of the radio relay apparatus of this invention. It is a schematic block diagram of the wireless relay apparatus of a prior art example (1). It is a schematic block diagram of the radio relay apparatus of a prior art example (2). It is a schematic block diagram of the radio relay apparatus of a prior art example (3). It is a schematic block diagram of the wireless relay apparatus of a prior art example (4). It is a schematic block diagram of the radio relay apparatus of a prior art example (5).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Manhole cover, 2 ... Asphalt layer or concrete layer (radio wave permeable structural material), 3 ... Concrete wall (radio wave permeable structural material), 4 ... Soil layer (radio wave permeable structural material), 5 ... Reflector (Reflection) Body), 5a ... reflecting surface, 7 ... manhole cover, 8 ... asphalt layer or concrete layer (radio wave permeable structural material), 9 ... concrete wall (radio wave permeable structural material), 10 ... soil layer (radio wave permeable structural material) ), 11 ... Reflector (reflector), 11a ... Reflecting surface, 13 ... Manhole cover, 14 ... Asphalt layer or concrete layer (radio wave permeable structural material), 15 ... Concrete wall (radio wave permeable structural material), 16 ... Soil layer (radio wave permeable structural material), 17 ... reflector (reflector), 17a ... reflecting surface, 21 ... manhole cover, 22 ... asphalt layer or concrete layer (radio wave permeable structural material), 2 ... concrete wall (radio wave permeable structural material), 24 ... soil layer (radio wave permeable structural material), 25 ... reflector (reflector), 25a ... reflective surface, 105 ... reflector, 106 ... metal wire, 107 ... reflective Body, 108 ... Metal rod

Claims (10)

A wireless relay device that is installed in an underpass directly under a manhole cover and reflects radio waves propagating through the underpass to mediate transmission and reception of radio signals between the basement and the ground,
A wireless relay device comprising a reflector that reflects radio waves propagating through the underpass toward a radio wave transmitting structural material around the manhole cover.   The wireless relay device according to claim 1, wherein the reflector includes a conical or pyramidal reflecting surface whose apex is directed toward the manhole cover.   The reflector includes a substantially conical or substantially pyramidal reflecting surface whose apex is directed to the manhole cover side, and an inclination angle of a generatrix with respect to a bottom surface of the reflecting surface is larger at a top portion than a bottom portion of the reflecting surface. The wireless relay device according to claim 1, wherein the reflection surface is bent or curved.   The wireless relay device according to claim 2 or 3, wherein a center of a circumscribed circle of the manhole cover is disposed on a central axis of the reflecting surface.   The wireless relay device according to claim 1, wherein the reflector includes a triangular prism-shaped reflecting surface with a ridge line serving as a top portion directed toward the manhole cover.   The reflector has a substantially triangular prismatic reflecting surface with a ridge line at the top facing the manhole cover side, and the inclination angle of the side surface with respect to the bottom surface of the reflecting surface is larger at the top than at the bottom of the reflecting surface. The wireless relay device according to claim 1, wherein the reflecting surface is bent or curved.   The reflecting surface of the reflector is formed in a shape capable of concentrating radio waves reflected by the reflecting surface at a position where the radio wave transmitting structural material around the manhole cover is thinnest. The wireless relay device according to claim 3 or 6.   The wireless relay device according to any one of claims 1 to 7, wherein the reflector is obtained by vapor-depositing or pasting a metal foil on a surface of a shape molded with a resin.   The wireless relay device according to claim 1, wherein the reflector is configured by a grid of metal wires or metal bars.   The wireless relay device according to any one of claims 1 to 7, wherein the reflector has a mesh structure in which a large number of through holes are provided in a metal plate.

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