Methods, systems, and apparatus

Abstract

To provide a method, system and device, which enable estimation of water content below the ground surface using an antenna, and to provide a method, system and device for making effective use of information on radio wave reception intensity of an antenna.SOLUTION: Provided are: a method comprising receiving an electromagnetic wave via an antenna installed on and near a ground surface, and identifying water content below the ground surface according to reception intensity of the received electromagnetic wave; and a method comprising receiving the electromagnetic wave via the antenna installed on and near the ground surface, and detecting that the reception intensity of the received electromagnetic wave satisfies a predetermined condition.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to methods, systems, and apparatus utilizing antennas. [Background technology]

[0002] Conventional measures have been considered to address natural disasters such as river flooding and landslides caused by localized heavy rainfall. As a method for addressing such natural disasters, for example, it has been considered to monitor the underground conditions of levees across the watershed by measuring elastic waves propagating through the ground and the water content of the ground using sensors (Patent Document 1). Furthermore, it is known that the water content of the ground is very important information in projects such as irrigation (for example, Patent Document 2).

[0003] Patent Document 1 describes methods for measuring moisture content, including a method that determines moisture content from the magnitude of pressure in the soil, a method that determines moisture content from the change in impedance between two electrodes that are buried separately in the ground, and a method that determines moisture content from changes in dielectric constant and inductive components in the soil. Patent Document 2 also describes a method for optically measuring soil moisture content. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2000-46597 [Patent Document 2] Japanese Patent Publication No. 2002-65086 [Overview of the project] [Problems that the invention aims to solve]

[0005] The first object of the present invention is to provide a method, system, and apparatus capable of estimating the water content below the ground surface using an antenna.

[0006] A second object of the present invention is to provide a method, system, and apparatus for effectively utilizing information about the radio wave reception strength of an antenna. [Means for solving the problem]

[0007] The problem of the present invention is, [1] A method comprising the steps of receiving electromagnetic waves using an antenna installed on and near the ground surface, and determining the water content below the ground surface according to the received intensity of the electromagnetic waves; [2] A method comprising the steps of receiving electromagnetic waves using an antenna installed on and near the ground surface, and detecting that the received intensity of the received electromagnetic waves satisfies predetermined conditions; [3] The method according to [2], further comprising the step of notifying that a predetermined condition has been met; [4] The method according to any of [1] to [3] above, comprising the steps of transmitting information relating to received electromagnetic waves from a first device and receiving the information relating to said electromagnetic waves in a second device, wherein the second device performs a step of determining the moisture content or detecting that a predetermined condition has been met, based on the received information relating to said electromagnetic waves; [5] The method according to any one of the above [1] to [4], wherein the electromagnetic wave is a radio broadcast wave; [6] The method according to any one of [1] to [5], wherein the received intensity is the ratio of the received power when the antenna receives the electromagnetic wave to the transmitted power for transmitting the electromagnetic wave; [7] A system comprising a first device and a second device, wherein the first device includes transmitting means for transmitting information relating to electromagnetic waves received by an antenna installed on and near the ground surface, and the second device includes receiving means for receiving information relating to electromagnetic waves, and identifying means for determining the water content below the ground surface based on the received information relating to electromagnetic waves; [8] A system comprising a first device and a second device, wherein the first device includes transmitting means for transmitting information relating to electromagnetic waves received by an antenna installed on and near the ground surface, and the second device includes receiving means for receiving information relating to electromagnetic waves and detection means for detecting that the received information relating to electromagnetic waves satisfies predetermined conditions; [9] The system according to [7] or [8], wherein a first device is connected to a reactance circuit connected to an antenna, and a transmitting means is connected to a reactance circuit;

[10] A system according to any one of [7] to [9], wherein the first device comprises a rectifying means for rectifying a current generated by receiving electromagnetic waves with an antenna, and / or an amplifying means for amplifying the current, and a transmitting means transmits a signal based on the rectified and / or amplified current as information relating to electromagnetic waves;

[11] An apparatus comprising an antenna for receiving electromagnetic waves, a transmitting means for transmitting information relating to the received electromagnetic waves, and a device connected to a reactance circuit connected to the antenna, wherein the transmitting means is connected to the reactance circuit; This can be achieved. [Effects of the Invention]

[0008] According to the present invention, a method, system, and apparatus can be provided that can estimate the water content below the ground surface using an antenna. Furthermore, according to the present invention, a method, system, and apparatus can be provided that can effectively utilize information about the radio wave reception strength of an antenna. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of an apparatus according to an embodiment of the present invention. [Figure 2] (a) is a schematic diagram of a reactance circuit according to an embodiment of the present invention, and (b) is a schematic circuit diagram of the reactance circuit shown in Figure 2(a). [Figure 3] This is a schematic diagram showing the configuration of a radio wave receiving circuit element according to an embodiment of the present invention. [Figure 4] It is an example of a graph showing the analysis result of the transmission coefficient S21 with respect to the change in water content. [Figure 5] It is a graph showing the relationship between the input impedance of the reactance circuit and the water content at resonance. [Figure 6] It is a schematic diagram of an apparatus according to an embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the present invention (hereinafter referred to as "embodiments") will be described in detail below. Note that the present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

[0011] (First Embodiment): Method for Estimating Water Content The first embodiment relates to a method of receiving electromagnetic waves by an antenna installed on the ground surface and in the vicinity of the ground surface, and specifying the water content under the ground surface according to the reception intensity of the received electromagnetic waves. The reception intensity is represented by the reception power when the electromagnetic waves are received by the reception antenna.

[0012] FIG. 1 is a schematic diagram of an apparatus according to an embodiment of the present invention, and is an apparatus for implementing the method of the first embodiment. As shown in FIG. 1, the apparatus 1 of the present embodiment includes an antenna 2, a radio wave reception circuit element 3, and a reactance circuit 4.

[0013] The antenna 2 has a function of receiving electromagnetic waves. The electromagnetic waves received by the antenna 2 are preferably those transmitted from a predetermined transmission antenna at a predetermined distance from the antenna 2. By specifying the reception intensity of the electromagnetic waves transmitted from the predetermined transmission antenna at a specific intensity within a specific frequency range by the antenna 2, the water content of the medium such as soil and sand in the ground can be estimated, or it can be detected that the water content of the medium such as soil and sand in the ground is within a predetermined range.

[0014] The electromagnetic waves received by Antenna 2 are not particularly limited as long waves, but from a practical standpoint, radio waves such as long waves (LF) with wavelengths of 10 to 1 km, medium waves (MF) with wavelengths of 1 km to 100 m, short waves (HF) with wavelengths of 100 to 10 m, very high frequency (VHF) with wavelengths of 10 to 1 m, extremely high frequency (UHF) with wavelengths of 1 m to 10 cm, centimeter waves (SHF) with wavelengths of 10 to 1 cm, millimeter waves (EHF) with wavelengths of 1 cm to 1 mm, and submillimeter waves with wavelengths of 1 to 0.1 mm are preferred. Among these, from the viewpoint of electromagnetic waves penetrating deep into water-containing soil, it is preferable that the electromagnetic waves are standard radio waves used for terrestrial television broadcasts, radio broadcasts, and standard frequency time signals. In particular, AM radio broadcasts and standard frequency time signals that use long waves to medium waves, which are mainly propagated by ground waves, are preferred because the reception sensitivity is good when the antenna is installed on or near the ground surface.

[0015] More specifically, the electromagnetic waves received by antenna 2 have a frequency of 30 kHz or higher, and more preferably 500 kHz or higher. Furthermore, the electromagnetic waves received by antenna 2 have a frequency of 3 GHz or lower, more preferably 1000 MHz or lower, and even more preferably 1.6 MHz or lower. A frequency within the above range is preferable because it results in good reception sensitivity when the antenna is installed on or near the ground surface.

[0016] The shape of antenna 2 is not particularly limited as long as it can receive electromagnetic waves, and can be appropriately selected from shapes such as rod-shaped, planar, or spiral depending on the wavelength of the electromagnetic waves to be received. In the case of a rod-shaped antenna, any known type of antenna, such as a monopole or dipole, can be used. In addition, so-called miniaturized antennas such as chip antennas may also be used.

[0017] The materials constituting antenna 2 are not particularly limited as long as they can receive electromagnetic waves; for example, known materials used as receiving antennas, such as copper or aluminum, can be used. Furthermore, the antenna material may be coated with resin or the like, or it may be uncoated. From the viewpoint of versatility, copper or aluminum wire is preferred. Also, from the viewpoint of weather resistance, it is preferred that it be coated with resin or the like.

[0018] Antenna 2 is installed on and near the ground surface. When Antenna 2, which is installed at any location, is installed on and near the ground surface, the electromagnetic wave propagation loss is smaller and the antenna's received power is higher compared to when it is installed underground or in space away from the ground surface.

[0019] The electromagnetic waves received by antenna 2 pass through transmission line 5 as AC signals and are transmitted to radio wave receiving circuit element 3. Transmission line 5 can be a single wire such as copper wire or a known antenna cable such as coaxial cable.

[0020] Here, the electromagnetic waves received by antenna 2 include electromagnetic waves of various wavelengths. From the viewpoint of improving the reception sensitivity of the electromagnetic waves received by antenna 2, it is preferable to provide a filter function for removing noise between antenna 2 and radio wave receiving circuit element 3.

[0021] By using the reactance circuit shown in Figure 2(a) as the filtering function described above, it becomes possible to remove electromagnetic waves in a different frequency band than the electromagnetic waves emitted by the transmitting antenna as noise. By using a reactance circuit whose resonant frequency matches or approximates the frequency of the electromagnetic waves emitted by the transmitting antenna, it is possible to remove electromagnetic waves in a different frequency band than the electromagnetic waves emitted by the transmitting antenna.

[0022] The reactance circuit will be described below. Figure 2(a) is a schematic diagram of a reactance circuit 4 according to an embodiment of the present invention. The reactance circuit 4 has a circuit formed on a sheet-like or film-like insulator, and Figure 2(a) is a schematic diagram showing the reactance circuit 4 when viewed from a direction perpendicular to the plane of the sheet-like or film-like insulator. The reactance circuit 4 is provided with a circuit-shaped coil section 8 and a circuit-shaped coil section 9 on the front and back sides of a sheet-like or film-like insulator 7. The circuit-shaped coil sections 8 and 9 on the front and back sides are electrically connected by connection sections 10 (10a, 10b, 10c) provided in the overlapping portion with the insulator 7 in between. The reactance circuit 4 also includes a conductor 11 and a conductor 12, which are electrically connected at point a to a conductor connected to the antenna 2 and at point b to a transmission line 5 connected to a radio wave receiving circuit element 3, which will be described later.

[0023] The insulator 7 can be made of a resin film such as polyethylene, polypropylene, or polyester. The circuit coil section 8 and the circuit coil section 9 can be formed by arranging metal foil such as aluminum foil or copper foil on the insulator 7. Alternatively, they may be formed by applying a conductive paint containing metal, carbon, etc., or by metal vapor deposition on the insulator 7.

[0024] Figure 2(b) is a schematic circuit diagram of the reactance circuit shown in Figure 2(a). In the reactance circuit 4 shown in Figure 2(a), the portion where the circuit coil section 8 and the circuit coil section 9 overlap on opposite sides with the insulator 7 in between acts as a variable parallel plate capacitor (variable capacitor C in Figure 2(b)), the circuit coil section 8 and the circuit coil section 9 act as inductance L, and the resistance of the metal or conductive material forming the circuit coil section 8 and the circuit coil section 9 acts as resistance R, thus forming a parallel resonant circuit as a whole.

[0025] The reactance circuit 4 can be made into a parallel resonant circuit that resonates at a desired frequency by adjusting the capacitor C and inductance L according to the frequency of the electromagnetic wave to be received by the antenna 2. For example, if the reactance circuit 4 is designed so that the values ​​of capacitor C and inductance L are large, the resonance condition will be satisfied at a lower frequency. The values ​​of capacitor C and inductance L can be adjusted by changing the size and number of turns of the circuit coil section 8 and circuit coil section 9 in the reactance circuit 4 according to the frequency of the electromagnetic wave received from the transmitting antenna.

[0026] (Installation location of reactance circuit 4) The reactance circuit 4 may be installed underground, in contact with the ground surface, or in the air. However, it is preferable to install the entire reactance circuit 4 underground, as this allows the reactance circuit 4 to perform a kind of switching operation depending on the moisture content, enabling more accurate determination of the moisture content. The impedance of the reactance circuit 4 near its resonant frequency is described in detail below.

[0027] First, the impedance Z between points a and b of the reactance circuit 4 shown in Figure 2(b) ab This is expressed by the following equation (1).

[0028]

number

[0029] Rationalize equation (1) and reduce the real part R L and the imaginary part X L When divided into R L and X L These are represented by the following equations (2) and (3), respectively.

[0030]

number

[0031]

number

[0032] Here, in the above formula (3), the parallel resonance state is when the reactance X L is zero, that is, the numerator of formula (3): L - CR 2 - ω 2 L 2 C is zero. Also, since the resonance frequency at which such a resonance state appears is f0 (= ω / 2π), from formula (3) and f0 = ω / 2π, the resonance frequency is represented by the following formula (4).

[0033]

Number

[0034] By the way, in the reactance circuit 4, the capacitance C of the capacitor changes due to the stray capacitance with respect to the change in the moisture content of the soil where the circuit is installed. When the moisture content of the soil where the circuit is installed increases, the relative permittivity of the surroundings increases, and as a result, it becomes easier to accumulate charges, so the stray capacitance increases. Considering this phenomenon in formula (3), when the frequency is the resonance frequency f0, formula (3) becomes X L = 0.

[0035] Also, when considering the real part in the reactance circuit 4 at this time, since 1 ≫ C / L × R 2 in formula (4), the denominator of formula (2) is represented by the following formula (5). And near the resonance frequency, formula (2) is represented by formula (6).

[0036]

Number

[0037]

Number

[0038] As described above, in the reactance circuit 4 buried in the soil, the suspended capacitance C increases as the soil moisture content increases near the resonant frequency. As a result, from equation (6), Z ab The value will decrease.

[0039] Figure 5 is a graph showing the relationship between moisture content and the input impedance of the reactance circuit at resonance. That is, the relationship between moisture content and R in equation (6) above. L (Z ab This shows the relationship with the value of ).

[0040] When the received radio waves satisfy the resonance condition in the reactance circuit 4, the imaginary part above becomes zero (the reactance becomes zero), and R L This results in a circuit consisting only of this component. In this case, current flows through reactance circuit 4. Furthermore, during resonance, as the moisture content increases, the input impedance of the reactance circuit decreases to the order of several hundred ohms, causing current to flow through the circuit and resulting in switching operation.

[0041] On the other hand, if the received radio waves do not satisfy the resonance conditions in the reactance circuit 4, the reactance becomes too large to ignore, and the reactance circuit becomes open (no current flows). Also, even if resonance occurs, if the moisture content is very low, R becomes large, so the reactance circuit becomes equivalent to being open. In this way, the reactance circuit 4 switches depending on the moisture content of the soil, etc., at the antenna 2 installation site, which is the object of measurement.

[0042] Thus, the combined impedance Z ab As the signal strength decreases, the reception intensity increases, allowing for more accurate detection. As a result, it becomes possible to determine the moisture content more accurately.

[0043] The radio wave receiving circuit element 3 has the function of transmitting information about the received electromagnetic waves. Figure 3 is a schematic diagram showing the configuration of a radio wave receiving circuit element according to an embodiment of the present invention. As shown in Figure 3, the radio wave receiving circuit element 3 of this embodiment includes a filter 21, an amplification unit 22, a rectifier unit 23, and a transmission unit 24. The radio wave receiving circuit element 3 may be equipped with a power supply system for operation. As shown in Figure 1, the radio wave receiving circuit element 3 is in a grounded state.

[0044] Furthermore, depending on the installation location, the radio wave receiving circuit element 3 can also be provided supported by an insulating support 6, as shown in Figure 1.

[0045] (Operation of device 1) The following describes a series of operations for transmitting information about the electromagnetic waves received by antenna 2, using Figures 1 and 3. In Figure 1, the electromagnetic waves received by antenna 2 are transmitted as AC electrical signals through transmission line 5 to reactance circuit 4 connected to antenna 2 at point a, then through reactance circuit 4, through transmission line 5 connected to reactance circuit 4 at point b, and finally transmitted to radio wave receiving circuit element 3.

[0046] The transmitted AC electrical signal is filtered by a filter 21, which is composed of a low-pass filter in the radio wave receiving circuit element 3 shown in Figure 3, and the signal is amplified in the amplification unit 22. The amplified AC signal is converted into a DC signal in the rectifier unit 23 and transmitted to the transmitting unit 24, from which it is transmitted as electromagnetic wave information to a computer device via a predetermined network. The filter 21 may be provided as needed depending on the receiving sensitivity.

[0047] (Estimation of moisture content) The signal transmitted from the transmitting unit 24, which contains information about electromagnetic waves received by an antenna installed on and near the ground surface, is received by a computer device. Based on the received signal containing information about electromagnetic waves, the computer device can determine the moisture content of a predetermined location near the ground surface below the antenna installation site. Here, the predetermined location can be set as appropriate. For example, the correspondence between the moisture content of the soil at a depth of 10 cm directly below the antenna installation site and the received electromagnetic wave intensity at that time can be measured in advance, and these multiple correspondences between moisture content and received electromagnetic wave intensity can be set as a data table. Then, by referring to the data table, the corresponding soil moisture content at a depth of 10 cm can be determined based on the actually measured received intensity. For example, if multiple correspondences between the soil moisture content at a depth of 30 cm directly below the antenna installation site and the received electromagnetic wave intensity at that time have been set as a data table, the soil moisture content at a depth of 30 cm directly below the antenna installation site can be estimated from the actually measured received intensity.

[0048] Any computer device that has a receiving means for receiving information about electromagnetic waves and a function for processing the received information can be used, including tablet terminals, smartphones, desktop personal computers, and notebook personal computers.

[0049] The determination of moisture content is carried out as follows: Using the apparatus 1 shown in Figure 1, the received power when electromagnetic waves are received by antenna 2 for a measurement target with a known moisture content is measured in advance, and the relationship between moisture content and the received power of antenna 2 is obtained as a data table or graph from the measured values ​​for various moisture contents. Then, the received power when electromagnetic waves are received by the receiving antenna for a measurement target with an unknown moisture content is measured, and the corresponding moisture content is determined based on the data table or graph of the relationship between moisture content and the received power when electromagnetic waves are received by the receiving antenna.

[0050] The moisture content can be determined using the value of the received power when electromagnetic waves are received by the receiving antenna, or it can be determined using the ratio of the received power when electromagnetic waves are received by the antenna to the transmission power used to transmit electromagnetic waves from the transmitting antenna (hereinafter also referred to as the transmission coefficient S21). In this case, it is preferable to obtain a data table or graph showing the relationship between the moisture content and the received power of antenna 2, as well as the relationship between the transmission coefficient S21 and the received power of antenna 2.

[0051] Figure 4 is an example of a graph showing the analysis results of the permeability coefficient S21 in relation to changes in water content. In the graph shown in Figure 4, the vertical axis represents 20log|S21|(dB), and the horizontal axis represents the soil water content (%).

[0052] The analysis model uses a transmitting antenna installed at a height of 200m above the ground and a receiving antenna installed at a height of 100m above the ground. The transmitting antenna transmits electromagnetic waves at 1MHz, and the receiving antenna is a 5m monopole antenna with its tip pointed towards the ground surface and installed vertically near the ground surface. The straight-line distance between the transmitting and receiving antennas is 1865m.

[0053] In the above analysis model, the moisture content of the soil on which the receiving antenna is installed is varied to 0%, 5%, 10%, 15%, 25%, and 30%, and the received power when electromagnetic waves are received by the receiving antenna is measured. The transmission coefficient S21 is determined from the received power when electromagnetic waves are received by the receiving antenna and the transmission power for transmitting electromagnetic waves, and the data for the graph shown in Figure 4 is obtained. By using the graph shown in Figure 4, for example, if the transmission coefficient S21 obtained from the measured value of the received power when electromagnetic waves are received by the receiving antenna is 0.00316, then 20log|S21| is -50dB, and the moisture content can be determined to be 8%.

[0054] The moisture content can be determined using the received power and transmission coefficient S21 when electromagnetic waves are received by the receiving antenna, as well as the impedance value in the reactance circuit 4. The impedance of the reactance circuit 4 can be determined from the measured values ​​by measuring the current and voltage between points a and b, using a known method.

[0055] When using impedance values, moisture content can be determined in the same way as when using received power values. That is, impedance values ​​are measured for objects with known moisture content, and the relationship between moisture content and impedance values ​​is obtained as a data table or graph from the measured values ​​for various moisture content levels. Then, impedance values ​​are measured for objects with unknown moisture content, and the corresponding moisture content is determined based on the data table or graph of the relationship between moisture content and impedance values.

[0056] (Other configurations of the device) In the first embodiment described above, the case where the reactance circuit 4 is underground was mainly explained as shown in Figure 1. However, even if the reactance circuit 4 is in the air, electromagnetic waves can be received by an antenna installed on or near the ground surface, and the water content below the ground surface can be determined according to the received intensity of the electromagnetic waves.

[0057] Figure 6 is a schematic diagram of an apparatus according to an embodiment of the present invention, and is an example of the apparatus configuration when the reactance circuit 4 is in the air. As shown in Figure 6, the inner conductor of a coaxial cable antenna 14 installed on and near the ground surface is connected to the reactance circuit 4 in the air by a conductor 13, and the reactance circuit 4 and the radio wave receiving circuit element 3 are connected by a transmission line 5. The inner conductor of the coaxial cable antenna 14 on the ground surface side is made to protrude as an electric wire and is positioned facing the ground surface. In this case, the conductor 13, which is the inner conductor, may be open, but as shown in Figure 6, it is more preferable to short-circuit the conductor 13 on the ground surface side to the outer conductor of the coaxial cable antenna 14, as this can improve the reception sensitivity of the received power. In Figure 6, an apparatus configuration including the reactance circuit 4 is shown, but the method of the first embodiment can also be implemented with an apparatus configuration that does not include the reactance circuit 4. As shown in Figure 6, it is preferable to use the reactance circuit 4 because it can further improve the reception sensitivity of the received power.

[0058] Similar to the apparatus 1 shown in Figure 1, the radio wave receiving circuit element 3 can be supported by a support 6 as needed. Alternatively, the radio wave receiving circuit element 3 and the reactance circuit 4 may be connected by a conductor 13.

[0059] (Second Embodiment): Method for Detecting Abnormalities in Moisture Content The second embodiment relates to a method for detecting whether the received electromagnetic wave intensity satisfies predetermined conditions, which is received by an antenna installed on or near the ground surface.

[0060] The second embodiment can be implemented using the same apparatus as the first embodiment. That is, the apparatus shown in Figure 1 or Figure 6 and the reactance circuit shown in Figure 2 in the first embodiment can be used. In the second embodiment, instead of determining the moisture content based on a signal containing information about electromagnetic waves received by a computer device in the first embodiment, the received intensity of the received electromagnetic waves is detected to satisfy predetermined conditions.

[0061] Similar to the first embodiment, the signal transmitted from the transmitting unit 24, which includes information about electromagnetic waves received by an antenna installed on and near the ground surface, is received by the computer device.

[0062] The computer device detects whether the received electromagnetic wave intensity meets predetermined conditions based on a signal containing information about the received electromagnetic wave. These predetermined conditions include, for example, the received intensity being greater than or less than a predetermined value. Detection of whether the received electromagnetic wave intensity meets the predetermined conditions is determined by comparing the received electromagnetic wave intensity with a predetermined value and determining whether the received intensity is at the predetermined value, greater than or less than the predetermined value.

[0063] Alternatively, using the apparatus 1 shown in Figure 1, the received power when electromagnetic waves are received by antenna 2 for a measurement target with a known moisture content can be measured in advance, and the relationship between moisture content and the received power of antenna 2 can be obtained as a data table or graph from the measured values ​​for various moisture contents. In this case, from the relationship between the received intensity and moisture content, if the received intensity is greater than a predetermined value, it can be determined that this corresponds to the moisture content below the ground surface at the measurement site when electromagnetic waves are received by the receiving antenna being greater than a predetermined value. Also, if the received intensity is less than a predetermined value, it can be determined that this corresponds to the moisture content below the ground surface at the measurement site when electromagnetic waves are received by the receiving antenna being less than a predetermined value.

[0064] The detection of whether the received intensity of the electromagnetic waves described above meets the predetermined conditions may be done using the value of the received power when the receiving antenna receives the electromagnetic waves, or it can be determined using the ratio of the received power (transmission coefficient S21) when the antenna receives the electromagnetic waves to the transmission power used to transmit the electromagnetic waves from the transmitting antenna. In this case, it is preferable to obtain a data table or graph of the relationship between the moisture content and the received power of antenna 2, as well as the relationship between the transmission coefficient S21 and the received power of antenna 2.

[0065] In the second embodiment, the system can be configured to notify when it has been detected that the above-mentioned predetermined conditions have been met. As a method of notification, the system can display on the display screen of the computer device used to detect when the predetermined conditions have been met in a manner that makes it clear that the predetermined conditions have been met, or it can emit an audio message in a manner that makes it clear that the predetermined conditions have been met.

[0066] Furthermore, as a method of notification, the system may display information on a separate computer device, such as a display screen, display device, or speaker, in a manner that indicates that a predetermined condition has been met, or it may transmit an audio message in a manner that indicates that a predetermined condition has been met.

[0067] By notifying when the received signal strength is detected to be greater than a predetermined value, it is possible to inform that the moisture content below the ground surface at the measurement site when the receiving antenna receives electromagnetic waves is greater than a predetermined value, indicating a risk of landslides or other hazards. Conversely, by notifying when the received signal strength is detected to be less than a predetermined value, it is possible to inform that the moisture content below the ground surface at the measurement site when the receiving antenna receives electromagnetic waves is less than a predetermined value, indicating that there is no risk of landslides or other hazards, or that the risk has decreased.

[0068] Furthermore, in irrigation projects, by notifying when the received signal strength is detected to be greater than a predetermined value, it is possible to inform that the water content below the ground surface at the measurement site when the receiving antenna receives electromagnetic waves is greater than a predetermined value, and that the water supply is sufficient. Conversely, by notifying when the received signal strength is detected to be less than a predetermined value, it is possible to inform that the water content below the ground surface at the measurement site when the receiving antenna receives electromagnetic waves is less than a predetermined value, and that water supply is necessary.

[0069] In the second embodiment described above, a mode of notification was described in which it is detected that the received electromagnetic wave intensity satisfies predetermined conditions. However, a mode of notification may also be described in which it is detected that the transmission coefficient S21 satisfies predetermined conditions. That is, by notifying when the transmission coefficient S21 is greater than a threshold, or when the transmission coefficient S21 is less than a threshold, information regarding dangers such as landslides or information regarding water supply can be provided.

[0070] According to the method, system, and apparatus of the present invention, the sensitivity of electromagnetic wave reception can be improved, and the water content below the ground surface can be estimated using an antenna. Furthermore, according to the method, system, and apparatus of the present invention, it is possible to detect or identify when the radio wave reception intensity of the antenna satisfies a predetermined relationship with the water content, so the reception intensity of the antenna can be effectively utilized as a source of information for countermeasures against natural disasters such as landslides and for irrigation projects. [Explanation of Symbols]

[0071] 1 device 2 antennas 3. Radio wave receiving circuit elements 4. Reactance Circuits 5. Transmission line 6 Support 7. Insulator 8,9 Circuit-shaped coil section 10 Connection part 11, 12, 13 conductors

Claims

1. The steps include receiving electromagnetic waves transmitted from a transmitting antenna using a receiving antenna installed on or near the ground surface, A step of determining the water content below the ground surface according to the received intensity of electromagnetic waves obtained by removing electromagnetic waves in a different frequency band from the electromagnetic waves transmitted by the transmitting antenna from the electromagnetic waves received by the receiving antenna, using a reactance circuit whose resonant frequency matches or approximates the frequency of the electromagnetic waves transmitted by the transmitting antenna. A method having

2. The method according to claim 1, wherein the entire reactance circuit is located underground.

3. The method according to claim 1, wherein the receiving antenna is a coaxial cable antenna.

4. A step of transmitting information about electromagnetic waves obtained via a reactance circuit from a first device, The steps include receiving the information regarding the electromagnetic waves with a second device, and It has, The method according to any one of claims 1 to 3, wherein the step of determining the moisture content is performed by a second device based on the received information regarding electromagnetic waves.

5. The method according to any one of claims 1 to 4, wherein the electromagnetic wave is a radio broadcast wave.

6. The method according to any one of claims 1 to 5, wherein the received intensity is the ratio of the received power obtained via a reactance circuit to the transmission power for transmitting the electromagnetic waves, when the receiving antenna receives the electromagnetic waves.

7. A system comprising a first device and a second device, The first device is connected to a reactance circuit, The reactance circuit is connected to a receiving antenna installed on and near the ground surface, and has a resonant frequency that matches or approximates the frequency of the electromagnetic waves emitted from the transmitting antenna. The first device is A transmitting means that transmits information about electromagnetic waves obtained by removing electromagnetic waves in a frequency band different from the frequency of the electromagnetic waves transmitted by the transmitting antenna from the electromagnetic waves received by the receiving antenna using a reactance circuit. Equipped with, The second device is A receiving means for receiving information about electromagnetic waves, Based on the information received from electromagnetic waves, a means of identifying the water content below the ground surface and A system that includes these features.

8. The first device is A rectifier means for rectifying a current generated by receiving electromagnetic waves with a receiving antenna and transmitted through a reactance circuit, and / or an amplifying means for amplifying the current. Equipped with, The system according to claim 7, wherein the transmitting means transmits a signal based on a rectified and / or amplified current as information relating to an electromagnetic wave.

9. A receiving antenna that receives electromagnetic waves transmitted from a transmitting antenna, A reactance circuit whose resonant frequency matches or approximates the frequency of the electromagnetic wave emitted from the transmitting antenna, A transmitting means that uses a reactance circuit to transmit information about electromagnetic waves obtained by removing electromagnetic waves in a frequency band different from the frequency of electromagnetic waves transmitted by a transmitting antenna from electromagnetic waves received by a receiving antenna. A device equipped with the following features.

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