Wired network system, environment state output device, and wired information transmission method

Abstract

To provide a wired network system capable of suppressing power consumption when environmental information is collected.SOLUTION: A wired network system includes: an environmental state output device 2A having a first transmission / reception unit 21A; an environmental state collection device 3 having a second transmission / reception units 31 and a system clocking unit 32; and a coaxial cable 4 to which the environmental state collection device 3 and an environmental state output device 2A are connected. The first transmission / reception unit transmits an environmental state signal based on environmental information detected by an environmental sensor to the environmental state collection device 3 via the coaxial cable 4 on a first carrier wave of a wireless frequency band. The system clocking unit 32 transmits a reference timing signal serving as a reference of a wired network system 1 to the environmental state output device 2A via the coaxial cable 4 on a second carrier wave of the wireless frequency band. The first transmission / reception unit 21A and the second transmission / reception unit 31 are configured to generate time of an active state and time of a sleep state based on the reference timing signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention mainly relates to a wired network system, an environmental condition output device, and a wired information transmission method that are installed and operated outdoors.

Background Art

[0002] Network systems that transmit environmental information acquired by sensors installed outdoors via a wired network to, for example, a cloud computer, which processes the information in an easy-to-view manner and provides it to users, are used in various applications. Examples of environmental information include rainfall, soil moisture, wind direction and speed, etc.

[0003] FIG. 14 shows the entire system 60 including the wired network system 6. In this system 60, environmental information obtained by environmental sensors (rainfall sensor 910A, soil moisture sensor 910B, wind direction and speed sensor 910C) is collected by the wired network system 6 and transmitted to, for example, a cloud computer 92 by a transmission device 91 such as an Internet device and a communication system device (for example, a modem for a mobile phone line). Users such as businesses, government agencies, and individuals who use environmental information view or print the environmental information collected, for example, on a smartphone 93.

[0004] As shown in the figure, the wired network system 6 that constitutes a part of the system 60 is composed of, for example, two terminal resistors 40A and 40B, four MCUs 41 (A to D), four RS485 standard drivers 42 (A to D), and a twisted pair cable 43. The twisted pair cable 43 twists two signal lines and covers the surroundings with a network cable (ground) to prevent noise. The two terminal resistors 40 (A, B) are resistors that prevent signal reflection at both ends of the twisted pair cable 43. The MCUs 41 (A to D) are microcontrollers (MCUs, Micro Controller Units) that perform various controls.

[0005] In relation to such a conventional system, for example, there are technologies disclosed in Patent Documents 1 and 2. Patent Documents 1 and 2 disclose a data transmission method using a coaxial cable. The data transmission method using a coaxial cable is excellent in terms of high-speed data transmission and the like.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, environmental information may need to be collected over a long period (for example, several years to several decades). For example, environmental information may generate value by being collected over a long period and capturing changes over that long period. There are also cases where it is collected over a long period to detect sudden abnormalities and prepare for disasters, etc. Furthermore, in many cases, there is no commercial power supply (electrical outlet) outdoors where the device for collecting environmental information is installed. Therefore, it is desirable to suppress power consumption so that it can continue to operate with, for example, a solar cell or the like. Therefore, an object of the present invention is to provide a wired network system, an environmental condition output device, and a wired information transmission method capable of suppressing power consumption when collecting environmental information.

Means for Solving the Problems

[0008] 〔1〕 A wired network system according to one aspect of the present invention is a wired network system used for collecting environmental information, an environmental condition output device having a first transmission / reception unit, an environmental condition collection device having a second transmission / reception unit and a system clock unit, and a coaxial cable connecting the environmental condition collection device and the environmental condition output device. The first transceiver loads an environmental status signal based on environmental information detected by an environmental sensor onto a first carrier wave in a radio frequency band and transmits it to the environmental status collection device via the coaxial cable. The system timing unit loads a reference timing signal that serves as a reference for the wired network system onto a second carrier wave in a radio frequency band and transmits it to the environmental status output device via the coaxial cable. The first transceiver and the second transceiver have times when they are in an active state and times when they are in a sleep state based on the reference timing signal. It is configured as described above. Note that "used for collecting environmental information" includes not only cases where it is exclusively used for collecting environmental information but also cases where it is used for other purposes.

[0009] According to such a wired network system, in the first transceiver of the environmental status output device that transmits an environmental status signal to the environmental status collection device via a coaxial cable and the second transceiver of the environmental status collection device that transmits a reference timing signal serving as a reference for the wired network system to the environmental status output device, times when they are in an active state and times when they are in a sleep state occur based on the reference timing signal, and power consumption is suppressed in the sleep state. Therefore, when collecting environmental information, it is possible to provide a wired network system capable of suppressing power consumption.

[0010] 〔8〕Moreover, an environmental status output device according to one aspect of the present invention is an environmental status output device used in a wired network system for collecting environmental information, the environmental status output device has a first transceiver, the wired network system in which the environmental status output device is used is the environmental status output device, an environmental status collection device having a second transceiver and a system timing unit, and a coaxial cable connecting the environmental status collection device and the environmental status output device. The first transceiver unit places an environmental state signal based on the environmental information detected by the environmental sensor on a first carrier wave in a radio frequency band and transmits it to the environmental state collection device via the coaxial cable. The system timing unit places a reference timing signal that serves as a reference for the wired network system on a second carrier wave in a radio frequency band and transmits it to the environmental state output device via the coaxial cable. The first transceiver unit and the second transceiver unit are configured such that there are time periods of being in an active state and a sleep state based on the reference timing signal. It is an environmental state output device.

[0011] According to such an environmental state output device, for the same reason as the above-mentioned wired network system, it is possible to provide an environmental state output device capable of suppressing power consumption when collecting environmental information.

[0012] 〔14〕 Further, a wired information transmission method according to an aspect of the present invention is A wired information transmission method of a wired network system used for collecting environmental information, The wired network system includes An environmental state output device having a first transceiver unit, An environmental state collection device having a second transceiver unit and a system timing unit, And a coaxial cable connecting the environmental state collection device and the environmental state output device. The step in which the first transceiver unit places an environmental state signal based on the environmental information detected by the environmental sensor on a first carrier wave in a radio frequency band and transmits it to the environmental state collection device via the coaxial cable, The step in which the system timing unit places a reference timing signal that serves as a reference for the wired network system on a second carrier wave in a radio frequency band and transmits it to the environmental state output device via the coaxial cable, The step in which the first transceiver unit has time periods of being in an active state or a sleep state based on the reference timing signal. The step in which the second transmission / reception unit enters an active state or a sleep state for a time based on the reference timing signal; It is a wired information transmission method including this.

[0013] According to such a wired information transmission method, for the same reason as the above-described wired network system, it is possible to provide a wired information transmission method capable of suppressing power consumption when collecting environmental information.

Brief Description of Drawings

[0014]

Figure 1

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Figure 13

Figure 14

Best Mode for Carrying Out the Invention

[0015] Hereinafter, a wired network system, an environmental state output device, and a wired information transmission method according to one aspect of the present invention will be described with reference to the drawings. Each drawing is a schematic diagram and does not necessarily strictly reflect an actual system, circuit, step (process), etc. Each embodiment does not limit the scope of the claims. Not all of the elements and their combinations described in each embodiment are essential to the present invention. For components that can be regarded as substantially equivalent, the same reference numerals may be used across embodiments, and repeated description may be omitted (in some cases, some descriptions may overlap).

[0016] 〔Embodiment 1〕 FIG. 1 is a diagram shown to explain the configuration example of the wired network system 1 according to Embodiment 1. FIG. 2 is a diagram shown to explain the configuration of the environmental state output device 2A (environmental information output device, sensor terminal) and the first transmission / reception unit 21A according to Embodiment 1. FIG. 3 is a diagram shown to explain the configuration of the environmental state collection device 3 (environmental information collection device, terminal aggregation device) and the second transmission / reception unit 31 according to Embodiment 1. FIG. 4(a) is a diagram shown to explain the configuration of the high-frequency burst signal TB used in Embodiment 1, and FIG. 4(b) is a diagram shown to explain the configuration of the high-frequency modulation signal.

[0017] FIG. 5 is a time chart showing the operation of the wired network system 1 according to Embodiment 1. FIG. 6 is a flowchart showing the operation of the environmental state collection device 3 according to Embodiment 1. FIG. 7 is a flowchart showing the operation of the environmental state output device 2A according to Embodiment 1. FIG. 13 is a diagram (5D-FB standard and 10D-FB standard) showing the attenuation characteristics of the coaxial cable 4 used in Embodiments 1 to 3 for explanation.

[0018] 〔Wired Network System 1〕 As shown in FIG. 1, the wired network system 1 according to Embodiment 1 is a wired network system 1 used for collecting environmental information, and includes environmental state output devices 2A, 2B, 2C (environmental information output devices, sensor terminals) having first transmission / reception units 21A, 21B, 21C, an environmental state collection device 3 (environmental information collection device, terminal aggregation device) having a second transmission / reception unit 31 and a system timing unit 32, and a coaxial cable 4 connecting the environmental state collection device 3 and the environmental state output devices 2A, 2B, 2C. The first transmission / reception unit places an environmental state signal based on environmental information detected by an environmental sensor on a first carrier wave in a radio frequency band and transmits it to the environmental state collection device 3 via the coaxial cable 4. The system timing unit 32 places a reference timing signal serving as a reference for the wired network system 1 on a second carrier wave in a radio frequency band and transmits it to the environmental state output devices 2A, 2B, 2C via the coaxial cable 4. The first transmission / reception units 21A, 21B, 21C and the second transmission / reception unit 31 are configured such that a time for becoming an active state and a time for becoming a sleep state occur based on the reference timing signal. Note that "transmission" and "reception" mean sending and receiving signals via a coaxial cable.

[0019] In the wired network system 1, the environmental state output devices 2A, 2B, 2C further include a first timing unit. The first timing unit generates a timing signal based on the reference timing signal, and the first transmission / reception units 21A, 21B, 21C are configured such that a time for becoming an active state and a time for becoming a sleep state occur based on the timing signal.

[0020] Also, in the wired network system 1, the first timing unit is configured to transmit the environmental state signal to the environmental state collection device 3 via the coaxial cable 4 within the time when it is in the active state.

[0021] Also, in the wired network system 1, the first carrier wave and the second carrier wave are configured to be carrier waves with frequencies in the sub-gigahertz band.

[0022] Also, in the wired network system 1, the first carrier wave and the second carrier wave are configured to be carrier waves with the same frequency.

[0023] Also, in the wired network system 1, it is configured such that there are a plurality of environmental state output devices 2A, 2B, and 2C.

[0024] 〔Environmental state output devices 2A, 2B, 2C〕 Also, as shown in FIG. 1, the environmental condition output devices 2A, 2B, 2C (environmental information output devices, sensor terminals) according to Embodiment 1 are environmental condition output devices 2A, 2B, 2C used in the wired network system 1 for collecting environmental information. The environmental condition output devices 2A, 2B, 2C have first transmission / reception units 21A, 21B, 21C. The wired network system 1 in which the environmental condition output devices 2A, 2B, 2C are used includes the environmental condition output devices 2A, 2B, 2C, an environmental condition collection device 3 (environmental information collection device, terminal aggregation device) having a second transmission / reception unit 31 and a system timing unit 32, and a coaxial cable 4 connecting the environmental condition collection device 3 and the environmental condition output devices 2A, 2B, 2C. The first transmission / reception units 21A, 21B, 21C place an environmental condition signal based on environmental information detected by an environmental sensor on a first carrier wave in a radio frequency band and transmit it to the environmental condition collection device 3 via the coaxial cable 4. The system timing unit 32 places a reference timing signal serving as a reference for the wired network system 1 on a second carrier wave in a radio frequency band and transmits it to the environmental condition output devices 2A, 2B, 2C via the coaxial cable 4. The first transmission / reception units 21A, 21B, 21C and the second transmission / reception unit 31 are configured such that times for being in an active state and a sleep state occur based on the reference timing signal. The environmental condition output devices 2A, 2B, 2C are as described above.

[0025] Also, in the environmental condition output devices 2A, 2B, 2C, the environmental condition output devices 2A, 2B, 2C further include a first timing unit. The first timing unit generates a timing signal based on the reference timing signal, and the first transmission / reception units 21A, 21B, 21C are configured such that times for being in an active state and a sleep state occur based on the timing signal.

[0026] Also, in the environmental condition output devices 2A, 2B, 2C, the first timing unit is configured to transmit the environmental condition signal to the environmental condition collection device 3 via the coaxial cable 4 within the time for being in an active state.

[0027] In addition, the environmental condition output devices 2A, 2B, and 2C are configured such that the first carrier wave is a carrier wave having a frequency in the sub-gigahertz band.

[0028] In addition, the environmental condition output devices 2A, 2B, and 2C are configured such that the first carrier wave and the second carrier wave have the same frequency.

[0029] 〔Wired Information Transmission Method〕 Also, as shown in FIGS. 1, 5 to 7, etc., the wired information transmission method according to Embodiment 1 is a wired information transmission method of the wired network system 1 used for collecting environmental information. The wired network system 1 includes environmental condition output devices 2A, 2B, 2C (environmental information output devices, sensor terminals) having first transmission / reception units 21A, 21B, 21C, an environmental condition collection device 3 (environmental information collection device, terminal aggregation device) having a second transmission / reception unit 31 and a system timing unit 32, and a coaxial cable 4 connecting the environmental condition collection device 3 and the environmental condition output devices 2A, 2B, 2C. The first transmission / reception units 21A, 21B, 21C transmit an environmental condition signal based on environmental information detected by an environmental sensor by loading it onto a first carrier wave in a radio frequency band via the coaxial cable 4 to the environmental condition collection device 3; the system timing unit 32 transmits a reference timing signal serving as a reference for the wired network system 1 by loading it onto a second carrier wave in a radio frequency band via the coaxial cable 4 to the environmental condition output devices 2A, 2B, 2C; the first transmission / reception units 21A, 21B, 21C enter an active state or a sleep state based on the reference timing signal; and the second transmission / reception unit 31 enters an active state or a sleep state based on the reference timing signal.

[0030] In this wired information transmission method, the environmental condition output devices 2A, 2B, and 2C are further configured to have a first timing unit, and the first timing unit generates a timing signal based on the reference timing signal, and the first transmission / reception units 21A, 21B, 21C enter an active state or a sleep state based on the timing signal.

[0031] In addition, in this wired information transmission method, the first timing unit includes a step of transmitting an environmental state signal to the environmental state collection device 3 via the coaxial cable 4 within the time when it is in an active state.

[0032] In addition, in this wired information transmission method, the first carrier wave and the second carrier wave are carrier waves having frequencies in the sub-gigahertz band.

[0033] In addition, in this wired information transmission method, the first carrier wave and the second carrier wave are carrier waves having the same frequency.

[0034] [Wired Network System 1 (Explanation Using FIG. 1)] Using FIG. 1, the wired network system 1 will be described in more detail. In the wired network system 1, as shown in FIG. 1, environmental state signals based on environmental information detected by the environmental sensor 10A (rainfall sensor), the environmental sensor 10B (soil moisture sensor), and the environmental sensor 10C (wind direction and wind speed sensor) are collected (aggregated) by the wired network system 1 and transmitted to the cloud computer 92 by the transmission device 91, and a user (such as a business operator, a government agency, an individual, etc.) views, prints, etc. the processing result with the smartphone 93.

[0035] [Environmental Sensor] Examples of the environmental sensor include the following. The environmental sensor 10A (rainfall sensor) is composed of a tipping bucket, and for example, every time there is a rainfall of 0.5 mm, the tipping bucket flips and outputs a pulse. The environmental sensor 10B (soil moisture sensor) outputs, for example, an electrical signal corresponding to the amount of moisture contained in the soil according to the electrical conductivity of the soil. The environmental sensor 10C (wind direction and wind speed sensor) is composed of, for example, a wind vane and a cup anemometer, and outputs an electrical signal corresponding to the wind direction (0 degrees to 360 degrees) and the wind speed. The environmental sensor is not limited to these, and for example, there are a seismic sensor (detects shaking and outputs), an air temperature sensor (detects air temperature and outputs), a humidity sensor (detects humidity and outputs), a water surface sensor (detects the height of the water surface of the sea, lake, etc. and outputs), etc.

[0036] This wired network system 1 includes environmental condition output devices 2A to 2C (environmental information output devices, sensor terminals), a coaxial cable 4, and an environmental condition collection device 3 (environmental information collection device, terminal aggregation device). Note that the coaxial connector 45 is a connector that connects the environmental condition output devices 2A to 2C and the environmental condition collection device 3 to the coaxial cable 4. There may be at least one environmental condition output device. The control units (MCU20A, 20B, 20C) are composed of microprocessor units and control the respective environmental condition output devices 2A, 2B, and 2C. Also, they receive the environmental signals (A to C) detected by the respective environmental sensors 10A, 10B, and 10C, and based on these, generate environmental condition signals used in the wired network system 1 (when the environmental signal can be used as it is, it is used directly as the environmental condition signal, and when conversion is required, it is converted into the environmental condition signal). For example, the MCU20A (control unit) counts the environmental signal (output pulse) detected by the rainfall sensor 10A for a certain period of time and converts it into rainfall amount, and adds sensor ID information, sensor type information, measurement interval information, etc. to it to form an environmental condition signal for the wired network system and outputs it to the first transceiver 21A. Similarly, the MCU20B (control unit) adds sensor ID information, etc. to the soil moisture amount (environmental signal) detected by the environmental sensor 10B (soil moisture sensor) to form an environmental condition signal B for the wired network system and outputs it to the first transceiver 21B. Similarly, the MCU20C (control unit) adds sensor ID information, etc. to the information on wind direction and wind speed (environmental signal) detected by the environmental sensor 10C (wind direction and wind speed sensor) to form an environmental condition signal C for the wired network system and outputs it to the first transceiver 21C.

[0037] Since the three environmental condition output devices 2A, 2B, and 2C have the same configuration, the environmental condition output device 2A will be described as a representative. As shown in FIGS. 1 and 2, the environmental condition output device 2A includes an MCU 20A (control unit), a first transmission / reception unit 21A, and a first timing unit 22A. The first timing unit 22A is composed of, for example, a 32 kHz crystal oscillator. It is a so-called Real Time Clock (RTC) that operates continuously for a long time using, for example, a coin cell as a power source, and measures time even when the MCU 20A (control unit) and / or the first transmission / reception unit 21A is in a sleep state.

[0038] 〔Environmental Condition Output Device 2A〕 This will be described with reference to FIG. 2. FIG. 2 shows a detailed circuit configuration example of the environmental condition output device 2A (environmental information output device, sensor terminal). In the figure, the first transmission / reception unit 21A has an upper circuit line and a lower circuit line.

[0039] In the upper circuit line, from the left, a low-noise amplifier 210, a mixer 211, a band-pass filter 212, a decoding circuit 213, and an error correction circuit 214 are connected in series and connected to the MCU 20A. The "reception function" is realized by the low-noise amplifier 210 to the error correction circuit 214. This is the same as the reception function in wireless communication technology. However, in this application, the signal is transmitted by wire instead of wirelessly. The low-noise amplifier 210 amplifies the minute signal attenuated by the transmission of the coaxial cable 4, and the mixer 211 removes the carrier wave. The band-pass filter 212 removes the frequency components that become noise, the decoding circuit 213 decodes the data, and the error correction circuit 214 removes errors and further performs a cyclic redundancy check to confirm that the data is correct.

[0040] In the lower circuit line, starting from the right, the error correction code addition circuit 220, modulation circuit 219, mixer 218, and linear amplifier 217 are connected in series and connected to the coaxial cable 4 via the coaxial connector 45. The error correction code addition circuit 220 to the linear amplifier 217 realize the "transmission function". This is similar to the transmission function in wireless communication technology. However, in this application, the signal is transmitted by wire instead of wirelessly. The error correction code addition circuit 220 adds a code for correcting errors in the transmission path (e.g., convolutional code) and a code for detecting errors (e.g., cyclic redundancy check code). The modulation circuit 219 adds a preamble signal indicating the start of the transmission signal, and further adds modulation (e.g., frequency modulation) so that the signal can be easily decoded even if it fluctuates due to the transmission of the coaxial cable 4. The local oscillator 216 generates a carrier wave in the sub-gigahertz band (e.g., 200 MHz). The mixer 218 creates a high-frequency modulated signal by multiplying the modulation signal by the carrier wave. The linear amplifier 217 amplifies the high-frequency modulated signal and transmits it to the coaxial cable 4 via the coaxial connector 45.

[0041] The first transceiver 21A receives the high-frequency burst signal TB transmitted to the coaxial cable 4, extracts the time information contained in this signal in the upper circuit line of FIG. 2, and supplies it to the MCU 20A. The MCU 20A corrects the time of the first timing unit 22A (sensor clock). By this correction, the time of the first timing unit 22A is made to match (coincide) with the system timing unit 32 (stem clock) 32. Here, the high-frequency burst signal TB contains the time information (reference timing signal, reference timing information) of the system timing unit 32 as shown in FIG. 4(b) and is a signal modulated to a high frequency. The first transceiver 21A creates a high-frequency modulated signal shown in FIG. 4(a) by high-frequency modulating the carrier wave according to the environmental information A, and transmits it to the coaxial cable 4 at a predetermined time of the first timing unit 22A.

[0042] [Environmental condition collection device 3] The environmental condition collection device 3 (environmental information collection device, terminal aggregation device) includes an MCU 30 (control unit), a second transceiver 31, a system timing unit 32 (system clock), a GNSS antenna 33, and a GNSS receiver 34 (see FIGS. 1 and 3). The MCU 30 controls the operation of the environmental condition collection device 3 and generates various signals. The system timing unit 32 outputs a reference timing signal that serves as a reference for the wired network system 1 (a clock serving as a time reference). It may be composed of a crystal oscillator (real-time clock) similar to the first timing unit 22A. The GNSS receiver 34 uses the GNSS antenna 33 to receive radio waves from GNSS (Global Navigation Satellite System) satellites and aligns the timing (time) of the system timing unit 32 with Coordinated Universal Time (UTC).

[0043] Based on the reference timing signal output from the system timing unit 32, the second transceiver 31 generates a high-frequency burst signal TB at a predetermined time (every predetermined time, every predetermined time interval) and transmits it to the coaxial cable 4 via the coaxial connector 45. The second transceiver 31 also decodes the environmental condition signal from the high-frequency modulation signals transmitted from the three environmental condition output devices 2A, 2B, and 2C to the coaxial cable 4 and supplies it to the transmission device 91 via the MCU 30.

[0044] 〔Coaxial Cable 4〕 FIG. 13 shows the attenuation characteristic of the coaxial cable. It is the attenuation characteristic of the coaxial cable at a length of 1200 m. This is for the purpose of explanation assuming the length of the coaxial cable is 1200 m corresponding to the fact that the maximum distance of the twisted pair cable 43 is 1200 m in the RS485 standard shown in FIG. 14 (conventional example).

[0045] In FIG. 13, coaxial cables of the 5D-FB standard with a diameter of approximately 8 mm and the 10D-FB standard with a diameter of 13 mm were exemplified. Comparing the characteristics of the two cables, it can be understood that signal attenuation can be reduced by thickening the cable. However, in both standards, as the frequency increases, the signal attenuation amount rises steeply. For example, observing the curve of the 10D-FB standard, the attenuation that was 140 dB at a frequency of 1 GHz increases sharply to 230 dB at a frequency of 2.4 GHz. Thus, as the frequency increases, the attenuation amount increases non-linearly, the signal level drops significantly, and it becomes buried in noise and undetectable.

[0046] In Embodiment 1, a wired network system 1 is constructed using the coaxial cable 4 having such characteristics as a transmission line. As transmission methods to be used at this time, the following two methods can be considered.

[0047] The first transmission method is a method of modulating transmission data and riding it on a carrier wave (carrier) and transmitting it in the coaxial cable 4 as if it were wireless communication. In wireless communication, signal processing technologies that can detect even low-level signals have been developed and used. Such circuits are available as semiconductor devices for wireless communication. Here, the semiconductor device for wireless communication means a semiconductor device (semiconductor device, semiconductor chip) manufactured for the purpose of performing data communication using an antenna. By using such a semiconductor device for wireless communication, data transmission becomes possible even when the signal level attenuates in the coaxial cable 4.

[0048] In wireless communication, the lower the carrier frequency, the longer the wavelength, and the larger the antenna and electronic circuit components (capacitors, coils, etc.). Therefore, carrier frequencies lower than 100 MHz have limited applications, and most of the commercially available semiconductor devices for wireless communication are those with a carrier frequency of 100 MHz or higher. Thus, in Embodiment 1, it is preferable to use a frequency band of 100 MHz to 1 GHz, which is called the "sub-gigahertz band". Semiconductor devices for wireless communication in the sub-gigahertz band are manufactured and sold by multiple semiconductor manufacturers, are available, and can also be used in Embodiment 1. Also, as shown below, if the carrier frequency is 1 GHz or less, the attenuation amount by a coaxial cable is also within the allowable range of the semiconductor device for wireless communication (also within the allowable range in Embodiment 1).

[0049] Commercially available semiconductor devices for wireless communication in the sub-gigahertz band (for example, EFR32FG23 of Silicon Laboratories) exhibit performance of a transmission power of +20 dBm and a reception sensitivity of -120 dBm. Since a signal attenuation of 140 dB (= 20 dB + 120 dB) is allowed for both transmission and reception, by using the above-mentioned 10D-FB standard coaxial cable, transmission over a distance of 1200 m is possible at a carrier frequency of 1 GHz (also within the usable range in Embodiment 1).

[0050] The second transmission method does not rely on wireless communication technology and is a method of lowering the frequency of the signal transmitted through the coaxial cable 4. In FIG. 13, when the frequency becomes 1 MHz or less, the attenuation amounts of both the 10D-FB standard and the 5D-FB standard become 6 dB or less. That is, since there is almost no amplitude decrease, the transmitted signal can be decoded by a simple circuit. Also, a transmission signal with a frequency of 1 MHz or less can be generated by a general-purpose digital circuit.

[0051] Here, if the frequency of the transmission signal is lowered too much, it becomes difficult to remove the influence of surge voltage due to lightning strikes, etc. Therefore, in the present invention, by using a frequency range of 100 kHz or higher and 1 MHz or lower (sub-megahertz band), data transmission is realized by a general-purpose digital circuit while avoiding the influence of surge voltage.

[0052] To summarize the above, the transmission methods using the coaxial cable 4 include a first method of transmitting in the sub-gigahertz band using a highly sensitive semiconductor device for wireless communication, and a second method of transmitting using a simple transceiver circuit in the sub-megahertz band where attenuation by the coaxial cable 4 does not occur. In the present invention, the sub-gigahertz band is described as a high frequency, and the sub-megahertz band is described as a low frequency.

[0053] 〔Transmission of signal〕 To transmit the environmental information detected and output by the environmental sensor as an environmental state signal based on the environmental information onto the first carrier wave in the radio frequency band, or to transmit the reference timing signal onto the second carrier wave in the radio frequency band, for example, a high frequency with a constant amplitude and / or frequency may be modulated by the signal and transmitted. The high frequency carrying the signal at this time is the carrier wave. As the modulation method, basically any of analog modulation (amplitude modulation, frequency modulation, pulse width modulation, etc.), digital modulation, pulse modulation, etc. may be used according to the input signal.

[0054] 〔High-frequency burst signal TB〕 Fig. 4(a) shows the configuration of the high-frequency burst signal TB. The high-frequency burst signal TB is composed of a preamble signal indicating the start timing of the transmission signal, network registration information listing the registered terminals of the wired network system 1, and an error detection code for confirming that no error has occurred. The network registration information is composed of the number of registered environmental state output devices and the ID information of each environmental state output device 2A, 2B, 2C.

[0055] 〔High-frequency modulation signal〕 Fig. 4(b) shows the configuration of the high-frequency modulation signal transmitted by the environmental state output device 2A. The high-frequency modulation signal is composed of a preamble signal indicating the transmission start timing, time information of the system timing unit 32, environmental information A, and an error detection code. The environmental state signal A is composed of the ID information of the rainfall sensor, the type information of the sensor, the measurement interval, and the rainfall amount.

[0056] 〔Operation of the wired network system 1〕 FIG. 5 is a time chart showing the operation of the wired network system 1 in a simplified manner. As shown in FIG. 5(f), one second of the system time is divided into 10 slots (time frames, time zones), and roles are assigned to each slot. This is the case when one cycle is set to 1 second, and one cycle can be set to any time such as 1 minute, 10 minutes, 1 hour, 24 hours, etc.

[0057] In FIG. 5, (a) to (c) show the time charts of the power supplies supplied to the first transceivers 21A to 21C, and (d) shows the time chart of the power supply supplied to the second transceiver 31. Power on indicates the time when those power supplies are turned on and become active states. Otherwise, it is the time of the sleep state. (e) shows the time chart of the signal flowing through the coaxial cable 4. (f) is a time chart for explaining each slot when one cycle is set to 1 second and divided into 10 parts.

[0058] Explanation will be made with the case where one cycle is set to 1 second and divided into 10 parts, and the time of each slot is 0.1 second. As shown in FIG. 5, the first 0.1 second is slot T0, which is the time zone when the environmental state collection device 3 transmits a high-frequency burst signal TB for time synchronization. The second slot (0.1 second to 0.2 second) is slot AR, which is the slot when the environmental state output device 26D that desires a new connection performs a new registration procedure to the network. The following six slots of T1 to T6 are the slots when the environmental state output devices 2A, 2B, 2C that have already received an assignment transmit to the environmental state collection device 3. For example, slot T1 is used by the environmental state output device 2A that detects the rainfall amount, slot T2 is used by the environmental state output device 2B that detects the soil moisture content, and slot T3 is used by the environmental state output device 2C that detects the wind direction and wind speed. The slot R after the time of 0.8 second is the slot for retransmission in case of an error and is not normally used.

[0059] The following operations are also possible. In slot T0, the first transceivers 21A to 21C become active and detect the states of the environmental sensors 10A to 10C. Then, at the timing (slot) when an environmental state signal based on the environmental information is sent out, each becomes active again (slots T1 to T3). During that time, the second transceiver 31 is in an active state. The time zones other than the active state shift to the sleep state.

[0060] The retransmission process is a process of retransmitting when there is an error or the like in the information to be transmitted. For example, it is performed when there is an error in the data, when the error cannot be corrected, or when there is data estimated to be abnormal based on the data so far. For example, if there is an error in the transmission by the first transceiver 21A made in slot T1, the power of the first transceiver 21A becomes on (active state) again in slot R (0.8 seconds to 0.9 seconds) and the data is transmitted again. The number of slots R may be less than or equal to the number of the registered first transceivers 21A to 21C. For example, when three of the first transceivers 21A to 21C are registered, it may be 3 or less. Since errors rarely occur, a smaller number, for example, 2 may also be acceptable. The times of slots T0 to R may be equal, but they do not necessarily have to be equal. Also, when there are almost no errors, slot R does not necessarily have to be provided. Also, in order to further reduce the power consumption during one cycle, a time zone of only the sleep state may be provided. For example, slots T4 to T6 may be such time zones.

[0061] 〔Operation of environmental state collection device 3〕 Fig. 6 shows the operation of the environmental condition collection device 3 (environmental information collection device, terminal aggregation device) as a flowchart. In step SP1, it waits for the second digit of the system time indicated by the system timer unit 32 to become (0.0 seconds) and detects slot T0. In step SP2, the power of the second transmission / reception unit 31 is turned on. In step SP3, a high-frequency burst signal TB is transmitted to the coaxial cable 4. In step SP4, it waits for the second digit of the system time to become (0.1 seconds) and detects slot AR. In step SP5, it checks whether a connection request is issued from the new environmental condition output device 26D (environmental information output device, sensor terminal) to the coaxial cable 4. If there is a connection request, the ID information of the environmental condition output device is registered in the system and a slot is allocated.

[0062] In steps SP6 and SP7, the high-frequency modulation signal transmitted by the environmental condition output device 2A is received at the timing when the second digit of the system time becomes (0.2 seconds) (slot T1). Similarly, in steps SP8 and SP9, the environmental condition output device 2B is received at the timing when the second digit becomes (0.3 seconds) (slot T2), and in steps SP10 and SP11, the signal from the environmental condition output device 2C is received at the timing when the second digit becomes (0.4 seconds) (slot T3).

[0063] In step SP12, since the reception processing from the three environmental condition output devices 2A, 2B, and 2C is completed, the second transmission / reception unit 31 is set to the power-saving sleep mode. As a result, as shown in Fig. 5(d), the power of the second transmission / reception unit 31 is "On" only in the time period when the second digit is (0.0 seconds to 0.5 seconds), suppressing unnecessary power consumption. In steps SP13 and SP14, retransmission processing is performed when there is an error.

[0064] 〔Operation of the environmental condition output device 2A〕 Fig. 7 shows the operation of the environmental condition output device 2A (environmental information output device, sensor terminal) as a flowchart. Here, it is assumed that the environmental condition output device 2A has already been registered in the wired network system 1, and the time of the first timer unit 22A generally matches that of the system timer unit 32. In step SP20, it waits for the timing (slot T0) when the seconds digit of the first timer unit 22A reaches (0.0 seconds), and in step SP21, it turns on the power of the first transceiver unit 21A. In step SP22, it receives the high-frequency burst signal TB, and in step SP23, it finely corrects the time of the first timer unit 22A so that it matches the system timer unit 32. In step SP24, it sets the first transceiver unit 21A to the sleep mode.

[0065] In step SP25, it waits for the seconds digit of the first timer unit 22A to reach (0.2 seconds) (slot T1). In step SP26, it turns on the power of the first transceiver unit 21A, and in step SP27, it transmits an environmental condition signal based on environmental information A. Next, in step SP28, by setting the first transceiver unit 21A to the sleep mode, it prevents power consumption in the sleep state (idle time) of the environmental condition output device 2A. It determines in step SP29 whether the data transmission described above has been successful. If it has ended in failure, in steps SP30 and SP31, it performs a retransmission process at the time when the seconds digit of the first timer unit 22A reaches (0.8 seconds) (slot R).

[0066] Note that in order to perform such processing, the MCU 30 (control unit) may always detect the reference timing signal issued from the system timer unit 32, and based on the reference timing signal, cause the second transceiver unit 31 to issue the TB signal according to the slot shown in Fig. 5(f). Also, even during the sleep state, it is preferable to keep the first transceiver units 21A, 21B, 21C in a receivable state (a state where it can detect whether the TB signal has arrived) so that they can receive the TB signal from the second transceiver unit 31.

[0067] With the configuration and processing described above, the transmission from the environmental condition output device 2A to the environmental condition collection device 3 is performed in slot T1 synchronized with the system time. Similarly, for the environmental condition output device 2B and the environmental condition output device 2C, the transmission is performed in slots T2 and T3 synchronized with the system time. As a result, as shown in FIG. 5(e), multiple terminals can transmit without collision using the coaxial cable 4. Also, as shown in FIGS. 5(a to c), each environmental condition output device turns on the power of the first transmission / reception units 21A, 21B, 21C only during slot T0 and the assigned slots (T1 to T3), and shifts the first transmission / reception units 21A, 21B, 21C to the sleep mode (sleep state) at other times to suppress the power consumption in the sleep state (idle time).

[0068] 〔Effects of Embodiment 1〕 As described above, according to the wired network system 1 of Embodiment 1, in the first transmission / reception units 21A, 21B, 21C of the environmental condition output devices 2A, 2B, 2C (environmental information output devices, sensor terminals) that transmit environmental condition signals to the environmental condition collection device 3 (environmental information collection device, terminal aggregation device) via the coaxial cable 4, and the second transmission / reception unit 31 that transmits the reference timing signal serving as the reference of the wired network system 1 to the environmental condition output devices 2A, 2B, 2C, there are times when they are in the active state and times when they are in the sleep state based on the reference timing signal, and the power consumption is suppressed in the sleep state. Therefore, it is possible to provide a wired network system 1 capable of suppressing power consumption when collecting environmental information.

[0069] For the same reason, the environmental condition output devices 2A, 2B, 2C used in the wired network system 1 can also provide an environmental condition output device capable of suppressing power consumption when collecting environmental information.

[0070] In the wired information transmission method of the wired network system 1, the first transceivers 21A, 21B, 21C place an environmental state signal based on environmental information detected by an environmental sensor on a first carrier wave in a radio frequency band and transmit it to an environmental state collection device 3 (environmental information collection device, terminal aggregation device) via a coaxial cable 4; a system timing unit 32 places a reference timing signal that is a reference for the wired network system 1 on a second carrier wave in a radio frequency band and transmits it to environmental state output devices 2A, 2B, 2C (environmental information output devices, sensor terminals) via the coaxial cable 4; the first transceivers 21A, 21B, 21C enter an active state or a sleep state based on the reference timing signal; and a second transceiver 31 enters an active state or a sleep state based on the reference timing signal. For the same reasons as described above, it is possible to provide a wired information transmission method capable of suppressing power consumption when collecting environmental information.

[0071] Further, if the environmental state output devices 2A, 2B, 2C further include a first timing unit that generates a timing signal based on the reference timing signal, and the first transceivers 21A, 21B, 21C are configured to enter an active state and a sleep state based on the timing signal, it becomes easier to perform timing management (time management) at the location where the environmental state output devices 2A, 2B, 2C are installed near the environmental sensor.

[0072] Also, if the first timing unit is configured to transmit the environmental state signal to the environmental state collection device 3 via the coaxial cable 4 within the active time, it is possible to distinguish that the signal within the active time is the environmental state signal and the signals at other times are not the environmental state signal, thus improving the reception reliability of the environmental state signal.

[0073] Also, if the first carrier wave and the second carrier wave are configured to be carrier waves with frequencies in the sub-gigahertz band, it is possible to suppress signal attenuation while using the coaxial cable 4.

[0074] Further, if the first carrier wave and the second carrier wave are configured to be carrier waves of the same frequency, the main circuits of the first transmission / reception units 21A, 21B, 21C of the environmental state output devices 2A, 2B, 2C and the second transmission / reception unit 31 of the environmental state collection device 3 can be configured with a common circuit, facilitating the configuration of the wired network system 1 or the like.

[0075] Also, when a plurality of environmental state output devices are installed, it becomes possible to collect a plurality of types of environmental information, collect environmental information at a plurality of remote locations separated from each other, and the like.

[0076] 〔Embodiment 2〕 FIG. 8 is a diagram shown to explain a configuration example of the wired network system 11 according to Embodiment 2. FIG. 9 is a diagram shown to explain the low-frequency signal generation unit 24 and the like used in Embodiment 2. FIG. 10 is a flowchart shown to explain the operation of the environmental state output device 26D (environmental information output device, sensor terminal) according to Embodiment 2.

[0077] The wired network system 11 and the environmental state output device according to Embodiment 2 are basically the same as the wired network system 1 or the like according to Embodiment 1. However, the environmental state output device 26D (environmental information output device, sensor terminal) further has a low-frequency signal generation unit 24 that generates a burst signal having a frequency lower than the first carrier frequency. When the burst signal is transmitted to the environmental state collection device 36 via the coaxial cable 4, the second transmission / reception unit 31 is configured to be in an active state, which is different.

[0078] Further, the wired information transmission method according to Embodiment 2 is basically the same as the wired information transmission method according to Embodiment 1, but the environmental condition output device 26D (environmental information output device, sensor terminal) of the wired network system 11 is configured to further include a low-frequency signal generation unit 24 that generates a burst signal having a frequency lower than the first carrier frequency. When the burst signal is transmitted to the environmental condition collection device 36 (environmental information collection device, terminal aggregation device 2) via the coaxial cable 4, the second transmission / reception unit 31 enters an active state, which is a different configuration point.

[0079] Assume a case where the environmental condition output devices 2A to 2C connected to the wired network system 1 perform data transmission only once every 30 minutes (low-frequency data transmission), and the problem when newly adding and connecting an environmental condition output device 26D will be described. Since the transmission frequency of the high-frequency burst signal TB is once every 30 minutes, the newly connected environmental condition output device 26D to the coaxial cable 4 cannot start the connection operation until the high-frequency burst signal TB is transmitted, waiting for up to 30 minutes at most. In the construction work of adding environmental condition output devices, waiting time will occur until the connection is confirmed.

[0080] Therefore, as Embodiment 2, FIG. 8 shows a wired network system 11 that can complete connection confirmation in a short time even when data transmission is low-frequency. In the figure, the newly connected environmental condition output device 26D is shown, and the already connected environmental condition output devices 2A to 2C are omitted.

[0081] Compared with the environmental condition output device 2A of Embodiment 1, a low-frequency signal generation unit 24 (low-frequency signal generation means) is added to the environmental condition output device 26D (see FIG. 8). Also, with respect to the environmental condition collection device 3 (environmental information collection device, terminal aggregation device) of Embodiment 1, a low-frequency signal detection unit 35 (low-frequency signal detection means) is added to the environmental condition collection device 36 (environmental information collection device, terminal aggregation device) of Embodiment 2. The low-frequency signal generation unit 24 receives a command from the MCU 20D and outputs a low-frequency signal to the coaxial cable 4 via the coaxial connector 45. The low-frequency signal detection unit 35 detects the low-frequency signal that has come via the coaxial cable 4 and outputs (notifies) it to the MCU 30.

[0082] The second transmission / reception unit 31 that has entered the sleep mode (sleep state) to suppress power consumption during the sleep state (idle state) cannot receive the high-frequency modulation signal. Therefore, in Embodiment 2, the MCU 20D sets the LBon signal to "logical 1", so that the low-frequency signal generation unit 24 transmits a low-frequency burst LB with a frequency of 1 MHz to the coaxial cable 4. The low-frequency burst LB transmitted through the coaxial cable 4 is detected by the low-frequency signal detection unit 35 and supplied to the MCU 30 as a trigger signal. The MCU 30 that has received the trigger signal releases the sleep mode (sleep state) of the second transmission / reception unit 31.

[0083] 〔Low-frequency signal generation unit 24〕 FIG. 9(a) shows the configuration of the low-frequency signal generation unit 24 according to Embodiment 2. The low-frequency signal generation unit 24 includes an oscillation circuit 240, a frequency division circuit 241 that inputs and divides the output thereof, an AND gate 242 that inputs the output of the frequency division circuit 241 and the command of the MCU 20D and outputs or stops the output of the frequency division circuit 241 based on the command, a driver amplifier 243 that inputs and amplifies the output thereof, a band-pass filter 244 that selects the output by frequency, and a coupling capacitor 245 that extracts an AC component from the output.

[0084] The oscillation circuit 240 outputs a constant frequency signal of 8 MHz by means of a crystal oscillator. The frequency division circuit 241 is realized by cascading D flip-flops, which reduces the frequency by a factor of 8 to generate a signal with a frequency of 1 MHz. The AND gate 242 performs a logical AND operation on the LBon signal instructed by the MCU20D and the signal with a frequency of 1 MHz, and allows the signal with a frequency of 1 MHz to pass only when the LBon signal is "logical 1". The driver amplifier 243 amplifies the signal with a frequency of 1 MHz. The band-pass filter 244 is a filter with a center frequency of 1 MHz, which removes unnecessary frequency components such as harmonics to create a sine wave signal with a frequency of 1 MHz. This sine wave signal passes through the coupling capacitor 25 to become the low-frequency burst LB. Here, the coupling capacitor 245 is, for example, a capacitor with a capacitance of 1 microfarad.

[0085] 〔Low-frequency signal detection unit 35〕 Fig. 9(b) shows the configuration of the low-frequency signal detection unit 35. The low-frequency signal detection unit 35 includes a coupling capacitor 350 connected to the coaxial cable 4, a band-pass filter 351 that inputs its output and passes a predetermined frequency signal, a diode 352 that inputs its output and performs so-called detection, a resistor 353 connected to its output terminal, a capacitor 354 with one terminal connected to the resistor and the other terminal grounded, and an analog comparator 355. The low-frequency burst LB transmitted through the coaxial cable 4 passes through the coupling capacitor 350, only the component with a frequency of 1 MHz is extracted by the band-pass filter 351, detected by the diode 352, and smoothed by the resistor 353 and the capacitor 354. The analog comparator 355 compares with a predetermined voltage Vth to generate a trigger signal when the low-frequency burst LB is transmitted to the coaxial cable 4.

[0086] The low-frequency signal detection unit 35 that always operates (is in an active state) without entering the sleep mode (sleep state) does not require power and consists of passive components (coupling capacitor 350, band-pass filter 351, diode 352, resistor 353, capacitor 354) and an analog comparator 355 with low power consumption (e.g., several milliwatts). Its power consumption can be extremely low, and it is possible to suppress the power consumption of the environmental condition collection device 36.

[0087] When a trigger signal is issued from the analog comparator 355, the MCU 30 enters the sleep mode and activates the second transmission / reception unit 31 that was suppressing power consumption, and the environmental condition output device 2D is registered as a new terminal.

[0088] 〔Environmental condition output device 26D〕 FIG. 10 shows the operation of the environmental condition output device 26D in Embodiment 2 as a flowchart. In step SP00, it is determined whether the environmental condition output device 2D is already registered in the wired network system 11. If it is already registered, the steps SP20 to SP31 described in FIG. 7 are performed to correct the time of the first timing unit 22D and transmit the environmental condition signal based on the environmental information D. If the environmental condition output device 2D is not registered, the environmental condition output device 2D is registered in the wired network system 11 through the steps from step SP32 to step SP38.

[0089] That is, in step SP32, the power of the first transmission / reception unit 21D is turned on, and in step SP33, the high-frequency burst signal TB is received. If the high-frequency burst signal TB can be received, the process proceeds to step SP34 to correct the time of the first timing unit 22D. In step SP35, it waits until the time when the second digit of the first timing unit 22D becomes (0.1 second), that is, the time of the slot AR. Next, in step SP36, the information of the environmental condition output device 26D is transmitted to register the environmental condition output device 2D in the wired network system 11. In step SP37, the first transmission / reception unit 21D is shifted to the sleep mode, and the registration operation of the new environmental condition output device is completed.

[0090] If the high frequency burst signal TB cannot be received even after a certain period of time has elapsed in step SP33, the second transceiver 31 mounted on the environmental condition collecting device 36 is in sleep mode. The process then proceeds to step 38, where the MCU 20D sets the LBon signal to logic 1, transmits a low frequency burst LB to the coaxial cable 4, and starts up the second transceiver 31 in sleep mode. As a result, a new environmental condition output device 26D can be registered without having to wait a long time for the high frequency burst signal TB.

[0091] In order to perform such processing, the MCU 30 (control unit) may constantly detect the reference timing signal output from the system timer unit 32 and the detection signal from the low-frequency signal detection unit 35, and cause the second transceiver unit 31 to output a TB signal based on the slot shown in Figure 5(f) based on the reference timing signal.

[0092] 8 can be used not only when adding a new environmental condition output device 26D, but also when adding a low-frequency signal generating unit 24 (a circuit similar to 26D) to the already registered environmental condition output devices 2A to 2C and when there is an abnormality in the environmental information from the environmental sensors 10A to 10C (for example, when the amount of rain is abnormally large and there is a risk of a disaster, or when the information itself is an abnormal value and a failure of the environmental sensor is suspected). This is when an emergency transmission is required. In this case, it is preferable that the functional part is functioning so that the MCU 20D (controller) can always detect environmental information from the environmental sensor even in the sleep state.

[0093] [Effects of the second embodiment] In this way, the environmental condition output device 26D further includes a low-frequency signal generation unit 24 that generates a burst signal having a frequency lower than the first carrier frequency. When the burst signal is transmitted to the environmental condition collection device 36 via the coaxial cable, the second transmission / reception unit 31 becomes active. Even when the second transmission / reception unit 31 is in the sleep state, it is possible to shift to the active state without waiting for the next cycle. As a result, it becomes possible to easily add a new environmental condition output device 26D. Also, when it is necessary to urgently send an environmental condition signal based on environmental information from an environmental sensor, it is also possible to quickly shift the second transmission / reception unit 31 to the active state.

[0094] 〔Embodiment 3〕 FIG. 11 is a diagram showing a configuration example of the wired network system 12 according to Embodiment 3. FIG. 12 is a diagram showing the configuration of the branch unit 5 used in Embodiment 3.

[0095] The wired network system 12 according to Embodiment 3 is basically the same as the wired network system 1 according to Embodiment 1 (or Embodiment 2), except that the environmental condition output devices 2A, 2B, and 2C are connected to different coaxial cables 4A, 4B, and 4C, respectively.

[0096] In Embodiment 1 (or Embodiment 2), one coaxial cable 4 was branched to connect a plurality of environmental condition output devices 2A, 2B, and 2C. However, at the installation site of the wired network system, in order to facilitate maintenance, it may be preferable to run a coaxial cable 4 for each of the environmental condition output devices 2A, 2B, and 2C.

[0097] Therefore, in the wired network system 12 of Embodiment 3 shown in FIG. 11, the coaxial cable 4 is branched into three by two branch units 5, and the environmental condition output devices 2A, 2B, and 2C are connected to the branched coaxial cables 4 (A to C), respectively.

[0098] 〔Branch Unit 5〕 The configuration of the branching section 5 is shown in Fig. 12. The input terminals Y and Z are connected to both ends of the input side of the tapped transformer 51. One side of the output side of the tapped transformer 51 to which the balance resistor 52 is connected in parallel is connected to the output terminal X, and the other side is grounded. The branching section 5 includes a tapped transformer 51 and a balance resistor 52. It evenly distributes the high-frequency signal input to the terminal X to the terminals Y and Z.

[0099] 〔Effects of Embodiment 3〕 Coaxial cables 4 can be pulled for each of the environmental condition output devices 2A, 2B, and 2C, facilitating construction and maintenance at the installation site of the wired network system.

[0100] As described above, the present invention has been explained based on the above embodiments, but the present invention is not limited to the above embodiments. It can be implemented in various forms without departing from the gist thereof. For example, the following modifications are possible.

[0101] (1) In Embodiment 2, it has been described that the environmental condition output device 2D generates a low-frequency burst LB to activate the environmental condition collection device 36 in the sleep mode. The present invention is not limited to this. For example, the environmental condition collection device 36 can also generate a low-frequency burst LB to activate the environmental condition output device 26D in the sleep mode (sleep state).

[0102] (2) Many commercially available semiconductor devices for wireless communication incorporate an MCU function, a real-time clock function, and a pulse generation function. By using a semiconductor device for wireless communication incorporating these functions, it is also possible to implement the environmental condition output devices 2A, 2B, and 2C with a single-chip semiconductor.

[0103] (3) Commercially available semiconductor devices for wireless communication also have a function of detecting the signal level (RSSI: Radio Signal Strength Indicator) of a high-frequency modulation signal. Therefore, in the environmental condition collection device 3, the RSSI of the high-frequency modulation signal can be detected and transmitted to the cloud computer 92 via the transmission device 91. With such a configuration, an abnormal situation such as a disconnection in the coaxial cable 4 can be detected as a decrease in RSSI and displayed on the smartphone 93.

[0104] (4) Fig. 13 shows the attenuation characteristics of the 5D-FB standard and 10D-FB standard of the coaxial cable, and it is exemplified that data transmission over a distance of 1200 m is possible even at a carrier frequency of 1 GHz. Needless to say, by using a coaxial cable with less attenuation than 10D-FB (for example, a coaxial cable of the 10D-SFA standard) or by using a carrier frequency lower than 1 GHz, data transmission over a distance exceeding 1200 m can be realized.

Explanation of symbols

[0105] 1... Wired network system (Embodiment 1), 2A, 2B, 2C... Environmental condition output device (environmental information output device, sensor terminal), 3... Environmental condition collection device (environmental information collection device, terminal aggregation device), 4... Coaxial cable, 5... Branch section, 6... Wired network system (conventional example), 10A... Environmental sensor (rainfall sensor), 10B... Environmental sensor (soil moisture sensor), 10C... Environmental sensor (wind direction and speed sensor), 11... Wired network system (Embodiment 2), 12... Wired network system (Embodiment 3), 20A, 20B, 20C, 20D... MCU (control unit), 21A, 21B, 21C, 21D... First transceiver, 22A, 22B, 22C, 22D... First timing unit (terminal clock), 24…Low-frequency signal generation unit (low-frequency signal generation means), 26D…Environmental condition output device (environmental information output device, sensor terminal), 30…MCU (control unit), 31…Second transceiver unit, 32…System timing unit (system clock), 33…GNSS antenna, 34…GNSS receiver, 35…Low-frequency signal detection unit (low-frequency signal detection means), 36…Environmental condition collection device (environmental information collection device, terminal aggregation device, Embodiment 2), 91…Transmission device, 92…Cloud computer, 93…Smartphone, 40A, 40B…Terminal resistors, 41A, 41B, 41C, 41D…MCU (Central Processing Unit, microcontroller unit, control unit), 42A, 42B, 42C, 42D…RS458 standard driver, 43…Twisted pair cable, 45…Coaxial connector, 51…Transformer with taps, 52…Balanced resistor, 210…Low-noise amplifier, 211…Mixer, 212…Band-pass filter, 213…Decoder circuit, 214…Error correction circuit, 216…Local oscillator, 217…Linear amplifier, 218…Mixer, 219…Modulation circuit, 220…Error correction addition circuit, 240…Oscillation circuit, 241…Frequency division circuit, 242…AND gate, 243…Driver amplifier, 244…Band-pass filter, 245…Coupling capacitor, 350... Coupling capacitor, 351... Band - pass filter, 352... Diode, 353... Resistor, 354... Capacitor, 355... Analog comparator 910A, 910B, 910C... Environmental sensor

Claims

1. A wired network system used for collecting environmental information, an environmental condition output device having a first transceiver, an environmental condition collection device having a second transceiver and a system timing unit, and a coaxial cable connecting the environmental condition collection device and the environmental condition output device, wherein the first transceiver places an environmental condition signal based on environmental information detected by an environmental sensor on a first carrier wave in a radio frequency band and transmits it to the environmental condition collection device via the coaxial cable, the system timing unit places a reference timing signal serving as a reference for the wired network system on a second carrier wave in a radio frequency band and transmits it to the environmental condition output device via the coaxial cable, and the first transceiver and the second transceiver have a time when they become active and a time when they become sleep states based on the reference timing signal, A wired network system configured as described above.

2. In the wired network system according to Claim 1, the environmental condition output device further has a first timing unit, the first timing unit generates a timing signal based on the reference timing signal, and the first transceiver has a time when it becomes active and a time when it becomes a sleep state based on the timing signal, A wired network system configured as described above.

3. In the wired network system according to Claim 1, the first timing unit transmits the environmental condition signal to the environmental condition collection device via the coaxial cable within the time when it is in the active state, A wired network system configured as described above.

4. In the wired network system according to Claim 1, the first carrier wave and the second carrier wave are carrier waves with frequencies in the sub-gigahertz band, A wired network system configured as described above.

5. In the wired network system according to Claim 1, the first carrier wave and the second carrier wave are carrier waves with the same frequency, A wired network system configured as described above.

6. In the wired network system according to Claim 1, there are a plurality of the environmental condition output devices, A wired network system configured as described above.

7. In the wired network system according to Claim 1, the environmental condition output device further has a low-frequency signal generation unit that generates a burst signal with a frequency lower than the first carrier frequency, When the burst signal is transmitted to the environmental condition collection device via the coaxial cable, the second transmission / reception unit becomes active. A wired network system configured as described above. **Claim 8** An environmental condition output device used in a wired network system for collecting environmental information, wherein the environmental condition output device has a first transmission / reception unit, the wired network system in which the environmental condition output device is used, the environmental condition output device, an environmental condition collection device having a second transmission / reception unit and a system timing unit, and a coaxial cable connecting the environmental condition collection device and the environmental condition output device. The first transmission / reception unit transmits an environmental condition signal based on environmental information detected by an environmental sensor by loading it onto a first carrier wave in a radio frequency band via the coaxial cable to the environmental condition collection device. The system timing unit transmits a reference timing signal serving as a reference for the wired network system by loading it onto a second carrier wave in a radio frequency band via the coaxial cable to the environmental condition output device. The first transmission / reception unit and the second transmission / reception unit are configured such that times for becoming active and times for becoming sleep states occur based on the reference timing signal. Environmental condition output device. **Claim 9** In the environmental condition output device according to claim 8, the environmental condition output device further has a first timing unit, the first timing unit generates a timing signal based on the reference timing signal, and the first transmission / reception unit has times for becoming active and times for becoming sleep states based on the timing signal. An environmental condition output device configured as described above. **Claim 10** In the environmental condition output device according to claim 8, the first timing unit transmits the environmental condition signal to the environmental condition collection device via the coaxial cable within the time for becoming active. An environmental condition output device configured as described above. **Claim 11** In the environmental condition output device according to claim 8, the first carrier wave is a carrier wave with a frequency in the sub-gigahertz band. An environmental condition output device configured as described above. **Claim 12** In the environmental condition output device according to claim 8, the first carrier wave and the second carrier wave are carrier waves with the same frequency. An environmental condition output device configured as described above. **Claim 13** In the environmental condition output device according to claim 8, The environmental condition output device further includes a low-frequency signal generator that generates a burst signal having a frequency lower than the first carrier frequency. When the burst signal is transmitted to the environmental condition collection device via the coaxial cable, the second transceiver becomes active. The environmental condition output device is configured as described above. **Claim 14** A wired information transmission method for a wired network system used for collecting environmental information, the method comprising: The wired network system includes: An environmental condition output device having a first transceiver; An environmental condition collection device having a second transceiver and a system timer; A coaxial cable connecting the environmental condition collection device and the environmental condition output device; A step in which the first transceiver loads an environmental condition signal based on environmental information detected by an environmental sensor onto a first carrier wave in a radio frequency band and transmits the signal to the environmental condition collection device via the coaxial cable; A step in which the system timer loads a reference timing signal serving as a reference for the wired network system onto a second carrier wave in a radio frequency band and transmits the signal to the environmental condition output device via the coaxial cable; A step in which the first transceiver enters an active state or a sleep state based on the reference timing signal; A step in which the second transceiver enters an active state or a sleep state based on the reference timing signal; The wired information transmission method including the above steps. **Claim 15** In the wired information transmission method according to claim 14, the environmental condition output device is further configured to include a first timer, a step in which the first timer generates a timing signal based on the reference timing signal; a step in which the first transceiver enters an active state or a sleep state based on the timing signal; The wired information transmission method including the above steps. **Claim 16** In the wired information transmission method according to claim 14, a step in which the first timer transmits the environmental condition signal to the environmental condition collection device via the coaxial cable during the active state; The wired information transmission method including the above step. **Claim 17** In the wired information transmission method according to claim 14, the first carrier wave and the second carrier wave are carrier waves having frequencies in the sub-gigahertz band. The wired information transmission method. **Claim 18** In the wired information transmission method according to claim 14, the first carrier wave and the second carrier wave are carrier waves having the same frequency. Wired information transmission method.

19. In the wired information transmission method according to claim 14, the environmental condition output device is configured to further include a low-frequency signal generation unit that generates a burst signal having a frequency lower than the first carrier frequency, and when the burst signal is transmitted to the environmental condition collection device via the coaxial cable, the second transmission / reception unit becomes active. Wired information transmission method.

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