Wireless sensing apparatus using relay resonator

Abstract

A wireless sensing device includes a receiving end sensor including a first LC resonant circuit, a transmitting end module including a second LC resonant circuit and a VNA connected to the second LC resonant circuit and applying an RF signal to the second LC resonant circuit, and a relay resonator including a third LC resonant circuit and connected between the transmitting end module and the receiving end sensor. The VNA measures a first coupling impedance when the transmitting end module and the relay resonator are coupled, measures a second coupling impedance when the transmitting end module, the relay resonator, and the receiving end sensor are coupled, and determines the resonant frequency of the receiving end sensor based on the first coupling impedance and the second coupling impedance.

Description

Technology Field

[0001] The disclosed content relates to a wireless sensing device using a relay resonator. Background Technology

[0002] Resonant wireless sensors can measure various indicators such as temperature, humidity, and pressure, and depending on the application, their utility can be diverse, ranging from industrial to medical fields. Resonant wireless sensors consist of an inductor-capacitor resonant circuit (LC resonator circuit), and the resonant frequency can change as the sensor's capacitance changes in response to changes in the external environment.

[0003] To monitor a resonant wireless sensor, using only the transmitting coil, the S of a vector network analyzer (VNA) at the resonant frequency of the receiving sensor 11 A method for measuring the dip can be used. S 11 is an S-parameter (scattering parameter) representing the reflection coefficient. Alternatively, a transmitter resonant circuit is configured by adding a matching capacitor to the transmitter coil, and when the transmitter capacitance is swept and the resonant frequencies of the transmitter and the sensor match, the S of the VNA 11 A method of measuring the point where the dip appears maximally can be used. Alternatively, a relay resonator can be added between the transmitter and the receiver to satisfy the parity time symmetry (PT-symmetry) condition between the transmitter, the relay resonator, and the sensor, thereby controlling the VNA's S 11 A method that maximizes the dip and improves the detection distance can be used.

[0004] However, since all of these methods require the use of expensive and complex VNA systems, they may be difficult to apply in real life. Also, in the case of the first method, S 11Since only the coil must be used without a matching capacitor at the transmitter to measure dips, power transmission efficiency is reduced and a narrow detection range may be observed. In the second method, while the sensor detection range can be improved by utilizing transmitter resonance, accurate measurement is difficult due to distortion of the VNA's S-parameters caused by changes in coil parasitic resistance with frequency, and system operation may become complex as an additional sweep of the transmitter capacitor is required. In the third method, if the distance between the transmitter and the sensor widens, the PT symmetry condition is no longer satisfied, which may limit the maximum measurement range. The problem to be solved

[0005] Some embodiments may provide a wireless sensing device capable of improving the detection distance and measurement accuracy of a resonant wireless sensor and expanding its range of application.

[0006] Some embodiments may provide a miniaturized wireless sensing device that can replace a large vector network analyzer. means of solving the problem

[0007] A wireless sensing device according to some embodiment may include a receiving end sensor comprising a first LC resonant circuit, a transmitting end module comprising a second LC resonant circuit and a vector network analyzer (VNA) connected to the second LC resonant circuit and applying a radio frequency (RF) signal to the second LC resonant circuit, and a relay resonator connected between the transmitting end module and the receiving end sensor. The VNA may measure a first coupling impedance in a state where the transmitting end module and the relay resonator are coupled, measure a second coupling impedance in a state where the transmitting end module, the relay resonator, and the receiving end sensor are coupled, and determine the resonant frequency of the receiving end sensor based on the first coupling impedance and the second coupling impedance.

[0008] A wireless sensing device according to some embodiment may include a receiving sensor including a first LC resonant circuit and a transmitting module. The transmitting module may include an RF source that outputs an RF signal, a second LC resonant circuit that receives the RF signal at an input terminal, a load resistor connected to an output terminal of the second LC resonant circuit, an RF core circuit that converts a first voltage at the input terminal and a second voltage at the output terminal into a gain between the first voltage and the second voltage and a phase difference between the first voltage and the second voltage, and a processor that determines the resonant frequency of the receiving sensor based on the gain and the phase difference. Brief explanation of the drawing

[0009] FIG. 1 is a circuit diagram of a wireless sensing device according to one embodiment. Figure 2 is an equivalent circuit diagram of the wireless sensing device illustrated in Figure 1. Figure 3 is a diagram showing the reflection impedance according to frequency in the wireless sensing device illustrated in Figure 1. Figure 4 is a diagram illustrating a method for measuring reflected impedance in a wireless sensing device illustrated in Figure 1. FIG. 5 is a flowchart illustrating a method for determining the resonant frequency of a wireless sensing device according to one embodiment. FIG. 6 is a circuit diagram of a wireless sensing device according to another embodiment. Figure 7 is an equivalent circuit diagram of the wireless sensing device illustrated in Figure 6. FIG. 8 is a flowchart illustrating a method for determining the resonant frequency of a wireless sensing device according to another embodiment. FIG. 9 is a drawing showing a wireless sensing device according to another embodiment. Specific details for implementing the invention

[0010] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement them. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0011] In addition, to clearly explain the invention in the drawings, parts unrelated to the explanation have been omitted, and similar parts throughout the specification have been given similar reference numerals. In the flowcharts described with reference to the drawings, the order of operations may be changed, multiple operations may be merged or divided, and certain operations may not be performed.

[0012] When it is stated that a component is "connected" to another component, it should be understood that it may be directly connected to that other component, or that there may be other components in between. On the other hand, when it is stated that a component is "directly connected" to another component, it should be understood that there are no other components in between.

[0013] Additionally, expressions written in the singular form may be interpreted as singular or plural unless explicit expressions such as "one" or "singular" are used. Terms including ordinal numbers, such as the first, the second, etc., may be used to describe various components, but the components are not limited by these terms. These terms may be used for the purpose of distinguishing one component from another.

[0014] FIG. 1 is a circuit diagram of a wireless sensing device according to one embodiment, FIG. 2 is an equivalent circuit diagram of the wireless sensing device shown in FIG. 1, FIG. 3 is a diagram showing the reflection impedance according to frequency in the wireless sensing device shown in FIG. 1, FIG. 4 is a diagram explaining a method for measuring the reflection impedance in the wireless sensing device shown in FIG. 1, and FIG. 5 is a flowchart showing a method for determining the resonance frequency of a wireless sensing device according to one embodiment.

[0015] As illustrated in FIG. 1, the resonant wireless sensor (100) may include a transmitting module (110) and a receiving sensor (120). The transmitting module (110) and the receiving sensor (120) may be referred to as a transmitting circuit and a receiving circuit, respectively. The receiving sensor (120) may operate as a sensor, and the transmitting module (110) may operate as a reading device that reads information sensed by the receiving sensor (120).

[0016] The transmitting module (110) includes an LC resonant circuit and a vector network analyzer (VNA) (211) connected to the LC resonant circuit, and the LC resonant circuit has a resistor (R TX1 ), matching capacitor (C TX1 ) and inductor (L TX1 It may include ). Resistance (R TX1 ), capacitor (C TX1 ) and inductor (L TX1) can be connected in series. The receiving sensor (120) includes an LC resonant circuit, and the LC resonant circuit includes an inductor (L RX1 ), resistance (R RX1 ) and capacitor(C RX1 It may include an inductor (L RX1 ), resistance (R RX1 ) and capacitor(C RX1 ) can be connected in series.

[0017] In the receiving sensor (120), the capacitor (C) RX1 ) is a sensing capacitor that changes according to the parameter of interest, which can cause a change in the resonant frequency. The transmitting module (110) is an inductor (L TX1 The VNA (111) of the transmitting module (110) can be wirelessly coupled with the receiving sensor (120) to monitor the impedance or reflection coefficient and detect the resonant frequency of the receiving sensor (120). The VNA (111) of the transmitting module (110) generates a radio frequency (RF) signal (e.g., a sinusoidal signal) while changing the frequency within a variable frequency range, and the generated signal is applied to the circuit to be measured, i.e., the input terminal of the transmitting module (110) (e.g., a resistor (R TX1 Monitoring can be performed by applying it to one terminal of ).

[0018] When wireless coupling occurs between the transmitting module (110) and the receiving sensor (120), the impedance viewed from the transmitting module (110) (i.e., the combined impedance (Z) of the transmitting module (110) and the receiving sensor (120) TXRX1 )) is the self-impedance (Z) of the transmitting module (110). TX1 An additional impedance due to coupling with the receiving sensor (120) may be seen in ). The additional impedance is reflected impedance (Z ref It is called ). If expressed as an equivalent circuit, it can be illustrated as in Fig. 2.

[0019] In the equivalent circuit, the reflection impedance (Z ref ), that is, the combined impedance (Z TXRX1 ) and self-impedance (Z TX1 The difference of ) can be given as in mathematical formula 1.

[0020]

[0021] In mathematical formula 1, M is the mutual inductance of the transmitting module (110) and the receiving sensor (120), and Z RX1 is the self-inductance of the receiving sensor (120).

[0022] Reflection impedance (Z ref The real component of )(Re(Z ref )) can be given as in mathematical formula 2.

[0023]

[0024]

[0025] As illustrated in Equation 3 and Figure 3, the reflected impedance (Z) varies with the frequency of the RF signal. ref The real component of )(Re(Z ref The peak value of )) may vary. In this case, the resonant frequency (f) of the receiving sensor (120) RX1 The real component (Re(Z) in ) ref )) can have a maximum value.

[0026] In this way, the reflection impedance (Z ref Since the frequency characteristics of the receiving sensor (120) are included in ), the reflection impedance (Z ref Measuring ) can facilitate the measurement of the resonance frequency of the receiving sensor (120). The reflection coefficient (S) measured at the VNA (211) 11 Even with ), reflection impedance (Z ref Although it includes ) components, it may be difficult to detect minute changes because it includes unnecessary self-impedance components of the transmitting module (110). At this time, the S parameter (S measured by the VNA (211) 11) can be converted into impedance, and as shown in FIG. 4, the coupled impedance (Z TXRX1 The self-impedance (Z) of the transmitting module (110) in ) TX1 If you subtract ), the self-impedance component (Z TX1 Reflection impedance (Z) with ) removed ref ) can be measured.

[0027] Referring to FIGS. 4 and 5, the VNA (111) of the transmitting module (110) applies a signal generated while changing the frequency, thereby the self-impedance (Z) of the transmitting module (110). TX1 ) can be measured (S510). Self-impedance (Z TX1 ) is resistance (R TX1 ) and inductor(L TX1 It can be the impedance due to the series connection of ).

[0028] The VNA (111) of the transmitting module (110) applies a signal to the coupled impedance (Z) of the transmitting module (110) and the receiving sensor (120). TXRX1 ) can be measured (S520). The VNA (111) can measure the S parameter (S 11 Measure ) and S parameter(S 11 Converting ) into impedance to the coupled impedance (Z TXRX1 ) can be measured (S520).

[0029] The VNA (111) of the transmitting module (110) has a coupled impedance (Z TXRX1 Self-impedance (Z) in ) TX1 Subtract ) to get the reflected impedance (Z ref Calculate ) (S530), and reflection impedance (Z ref The resonant frequency can be measured based on ) (S540). The VNA (111) of the transmitting module (110) has a reflection impedance (Z) at the resonant frequency of the receiving sensor (120). ref Re(Z), the real component of ) ref By utilizing the fact that ) becomes maximum, the resonant frequency can be measured. The VNA (111) measures the reflected impedance (Z) measured while changing the frequency.ref The frequency at which the real component of ) reaches its maximum value can be determined as the resonance frequency.

[0030] As explained above, the transmitting module (110) has a reflection impedance (Z) at the resonant frequency of the receiving sensor (120). ref Re(Z), the real component of ) ref Sensor monitoring can be performed by utilizing the fact that ) becomes maximum, and the existing S parameter (S 11 Compared to the method using ), even weak signals can be detected, so the sensor detection range can be improved.

[0031] FIG. 6 is a circuit diagram of a wireless sensing device according to another embodiment, FIG. 7 is an equivalent circuit diagram of the wireless sensing device illustrated in FIG. 6, and FIG. 8 is a flowchart showing a method for determining the resonant frequency of a wireless sensing device according to another embodiment.

[0032] Referring to FIG. 6, the resonant wireless sensor (600) may include a transmitting module (610), a relay resonator (620), and a receiving sensor (630). The transmitting module (610) and the receiving sensor (630) may be referred to as a transmitting circuit and a receiving circuit, respectively. The receiving sensor (630) may operate as a sensor, the transmitting module (610) may operate as a reading device that reads information sensed by the receiving sensor (630), and the relay resonator (620) may operate as a relay between the receiving sensor (630) and the transmitting module (610).

[0033] The transmitting module (610) includes an LC resonant circuit and a VNA (611) connected to the LC resonant circuit, and the LC resonant circuit has a resistor (R TX2 ), matching capacitor (C TX2 ) and inductor (L TX2 It may include ). VNA (611), resistor (R TX2 ), capacitor (C TX2 ) and inductor (L TX2) can be connected in series. The relay resonator (620) includes an LC resonant circuit, and the LC resonant circuit includes an inductor (L R2 ), resistance (R R2 ) and capacitor(C R2 It may include an inductor (L R2 ), resistance (R R2 ) and capacitor(C R2 ) can be connected in series. The receiving sensor (630) includes an LC resonant circuit, and the LC resonant circuit includes an inductor (L RX2 ), resistance (R RX2 ) and capacitor(C RX2 It may include an inductor (L RX2 ), resistance (R RX2 ) and capacitor(C RX2 ) can be connected in series. In some embodiments, the relay resonator (620) is positioned closer to the receiving sensor (630) than to the transmitting circuit (610), so that the relay resonator (620) and the receiving sensor (630) can operate as a receiving module.

[0034] In the receiving sensor (630), the capacitor (C) RX2 ) is a sensing capacitor that changes according to the parameter of interest, which can cause a change in the resonant frequency. The transmitting module (610) is an inductor (L TX1 The VNA (611) of the transmitting module (610) can be wirelessly coupled with the relay resonator (620) and the receiving sensor (630) to monitor the impedance or reflection coefficient and detect the resonance frequency of the receiving sensor (630). The VNA (611) of the transmitting module (610) generates an RF signal (e.g., a sinusoidal signal) while changing the frequency within a variable frequency range, and the generated signal is applied to the circuit to be measured, i.e., the input terminal of the transmitting module (610) (e.g., a resistor (R TX2 Monitoring can be performed by applying it to one terminal of ).

[0035] When wireless coupling occurs at the transmitting module (610), the relay resonator (620), and the receiving sensor (630), the impedance viewed from the transmitting module (610) is the self-impedance (Z) of the transmitting module (610). TX2 Additional impedance resulting from the combination with the relay resonator (620) and the receiving end sensor (630), i.e., reflection impedance (Z ref1 ) may be seen as added. Also, the impedance viewed from the relay resonator (620) is the self-impedance (Z) of the relay resonator (620). R2 Additional impedance resulting from coupling with the receiving sensor (630) in ), i.e., reflection impedance (Z ref2 ) can be added. If expressed as an equivalent circuit, it can be illustrated as in Fig. 7.

[0036] First, the reflection impedance in the combined state of the transmitting module (610) and the relay resonator (620), that is, the combined impedance (Z) of the transmitting module (610) and the relay resonator (620). TXR2 ) and the self-impedance (Z) of the transmitting module (610) TX2 The difference of ) can be given as in mathematical formula 4.

[0037]

[0038] In mathematical formula 4, M1 is the mutual inductance of the transmitting module (610) and the relay resonator (620), and Z R2 is the self-inductance of the relay resonator (620).

[0039] Reflection impedance (Z) in a combined state of the transmitting end module (610), relay resonator (620), and receiving end sensor (630) ref1 ), that is, the combined impedance (Z) of the transmitting module (610), the relay resonator (620), and the receiving sensor (630). TXRRX2 ) and the self-impedance (Z) of the transmitting module (610) TX2 The difference of ) can be given as in mathematical formula 5.

[0040]

[0041] In mathematical formula 5, M2 is the mutual inductance between the relay resonator (620) and the receiving sensor (630), M3 is the mutual inductance between the transmitting module (610) and the receiving sensor (630), and Z RX2 is the self-inductance of the receiving sensor (630).

[0042] In mathematical formula 5, go Since it is large enough to be ignored, Equation 5 can be approximated as Equation 6.

[0043]

[0044] Mathematical formula 6 can be transformed into mathematical formula 7.

[0045]

[0046] If we transform mathematical formula 4, Since it can be given as Equation 8, Equation 7 can be transformed as Equation 9.

[0047]

[0048]

[0049] Referring to FIG. 8, the VNA (611) of the transmitting module (610) applies a signal generated while changing the frequency to the self-impedance (or first self-impedance) (Z) of the transmitting module (610). TX2 ) can be measured (S810). Self-impedance (Z TX2 ) is resistance (R TX2 ), capacitor (C TX2 ) and inductor (L TX2 It may be an impedance due to the series connection of ). In some embodiments, if the designs of the transmitting module (610) and the relay resonator (620) are not identical (S820: No), the VNA (611) is the self-impedance (or second self-impedance) (Z of the relay resonator (620) R2 ) can be measured (S830). Self-impedance (Z R2 ) is resistance (RR2 ), capacitor (C R2 ) and inductor (L R2 It may be an impedance due to the series connection of ). If the design of the transmitting module (610) and the relay resonator (620) is the same (S820: Yes), the VNA (611) is the self-impedance (Z) of the relay resonator (620). R2 ) is the self-impedance (Z) of the transmitting module (610) TX2 It can be used with the same value as ).

[0050] The VNA (611) applies the generated signal to the impedance (or first coupling impedance) (Z) of the transmitting module (610) and the relay resonator (620) combined. TXR2 ) can be measured (S840). The VNA (611) can measure S parameters (S) when the transmitting module (610) and the relay resonator (620) are combined. 11 Measure ) and the measured S parameter (S 11 Converting ) into impedance to the coupled impedance (Z TXR2 ) can be measured (S840).

[0051] VNA (611) has a coupled impedance (Z TXR2 ) and the self-impedance (Z) of the transmitting module (610) TX2 Reflection impedance (or first reflection impedance) (Z) in a combined state of the transmitting module (610) and the relay resonator (620) based on ) TXR2 -Z TXR2 ) can be calculated (S850).

[0052] The VNA (611) applies the generated signal to the combined impedance (or second combined impedance) (Z) of the transmitting module (610), the relay resonator (620), and the receiving sensor (630). TXRRX2 ) can be measured (S860). The VNA (611) can measure S parameters (S) when the transmitting module (610), the relay resonator (620), and the receiving sensor (630) are combined. 11 Measure ) and the measured S parameter (S 11Converting ) into impedance to the coupled impedance (Z TXRRX2 ) can be measured (S860).

[0053] VNA (611) has a coupled impedance (Z TXRRX2 ) and the self-impedance (Z) of the transmitting module (610) TX2 Reflection impedance (or second reflection impedance) (Z) in a combined state of the transmitting end module (610), relay resonator (620), and receiving end sensor (630) based on ) TXRRX2 -Z TXR2 ) can be calculated (S870).

[0054] The VNA (611) has a reflection impedance (Z) in a state where the transmitting module (610) and the relay resonator (620) are combined. TXR2 -Z TXR2 Reflection impedance (Z) in a combined state of the transmitting module (610), relay resonator (620), and receiving sensor (630). TXRRX2 -Z TXR2 ) and the self-impedance (Z) of the relay resonator (620) R2 The resonant frequency of the receiving sensor (630) can be calculated based on ) (S880). In some embodiments, the VNA (611) changes the frequency of the RF signal and, depending on the applied signal, the reflected impedance (Z TXR2 -Z TXR2 ), reflection impedance (Z TXRRX2 -Z TXR2 ) and impedance (Z R2 The frequency of the RF signal at which the value determined by ) becomes maximum can be calculated as the resonant frequency. For example, the VNA (611) can calculate the frequency at which the value of Equation 9 becomes maximum as the resonant frequency.

[0055] As described above, the wireless sensing device can improve measurement accuracy by measuring impedance to determine the resonant frequency and expand the range of application by providing a miniaturized system that does not perform complex calculations. Additionally, the wireless sensing device can improve the detection distance by adding a relay resonator (620). Accordingly, it can be utilized in fields where long-distance monitoring is required or where the measurement environment is poor.

[0056] FIG. 9 is a drawing showing a wireless sensing device according to another embodiment.

[0057] Referring to FIG. 9, the transmitting module (900) of the wireless sensing device may include an RF source (910), a transmitting unit (930), a load resistor (940), an RF core integrated circuit (IC) (950), and a processor (960). In some embodiments, the transmitting module (900) may be combined with the receiving sensor (120) described with reference to FIG. 1 or the relay resonator (620) and receiving sensor (630) described with reference to FIG. 6. In some embodiments, the transmitting module (900) may further include a battery for supplying power to the components of the transmitting module (900).

[0058] The RF source (910) can output RF signals of various frequencies. In some embodiments, the processor (960) can sweep the frequencies of the RF source (910).

[0059] In some embodiments, the transmitting module (900) may further include a circuit (920) for impedance matching and low-band filtering. The circuit (920) can transmit an RF signal without distortion through impedance matching and remove unnecessary high-frequency noise components through a low-band filter.

[0060] The transmitting unit (930) includes an LC resonant circuit, and the LC resonant circuit includes an inductor (L) connected in series. TX3) and matching capacitor (C TX3 It may include ). The LC resonant circuit can receive an RF signal at the input terminal. In some embodiments, a matching capacitor (C) is controlled by a processor (e.g., a microcontroller unit (MCU)) (960). TX3 By changing the capacitance value of ), it can be matched to a similar resonant frequency of the receiving sensor and the transmission efficiency can be maximized. A load resistor (940) can be connected to the output terminal of the transmitting terminal (930), that is, the LC resonant circuit.

[0061] The RF core circuit (950) is a voltage (V) at both ends (i.e., the input end and the output end) of the transmitting end (930) determined by the input of the RF signal. in , V out ) two voltages (V in , V out Gain (V) between Gain ) and two voltages (V in , V out Phase difference (V) between ) Phase It can be converted into ). The inductor (L) of the transmitting end (930). TX3 The reflection impedance induced when the receiver sensor or relay resonator and receiver sensor are combined causes a change in the impedance of the entire transmitter (930), so the reflection impedance can be measured through the change in impedance of the transmitter (930).

[0062] The processor (960) has a gain (V Gain ) and phase difference (V Phase Based on ), the impedance (Z) in the state where the receiving end sensor or relay resonator and the receiving end sensor are combined at the transmitting end (930) TX3 ) can be calculated as in Equation 10. The processor (960) calculates the impedance (Z) as in Equation 11. TX3 The real component of )(Re(Z TX3 The frequency of the RF signal that maximizes )) can be determined as the resonant frequency.

[0063]

[0064] In mathematical equation 10, |V in / V out | is profit(V Gain ) and, is the phase difference (V Phase ) and, R L is the resistance value of the load resistance (950).

[0065]

[0066] As explained above, since the wireless sensing device can measure impedance without using a complex VNA, it can provide a miniaturized system. Accordingly, the wireless sensing device can be integrated to a portable level, thereby improving weight reduction and portability. Furthermore, by adding a relay resonator, it can be utilized in fields requiring long-distance monitoring or in harsh measurement environments.

[0067] Although embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

Claim 1 A wireless sensing device comprising: a receiving end sensor including a first LC resonant circuit; a transmitting end module including a second LC resonant circuit and a vector network analyzer (VNA) connected to the second LC resonant circuit and applying a radio frequency (RF) signal to the second LC resonant circuit; and a relay resonator including a third LC resonant circuit and connected between the transmitting end module and the receiving end sensor, wherein the VNA measures a first coupling impedance in a state where the transmitting end module and the relay resonator are coupled, measures a second coupling impedance in a state where the transmitting end module, the relay resonator, and the receiving end sensor are coupled, and determines the resonant frequency of the receiving end sensor based on the first coupling impedance and the second coupling impedance. Claim 2 A wireless sensing device according to claim 1, wherein the VNA measures a first self-impedance of the transmitting module, calculates a first reflection impedance in a state where the transmitting module and the relay resonator are coupled based on the first self-impedance and the first coupling impedance, calculates a second reflection impedance in a state where the transmitting module, the relay resonator, and the receiving sensor are coupled based on the first self-impedance and the second coupling impedance, and determines the resonance frequency based on the second self-impedance of the relay resonator, the first reflection impedance, and the second reflection impedance. Claim 3 A wireless sensing device according to paragraph 2, wherein the VNA determines the frequency of the RF signal at which the value determined based on the second self-impedance, the first reflection impedance, and the second reflection impedance becomes maximum as the resonance frequency. Claim 4 A wireless sensing device according to claim 2, wherein the VNA calculates the first reflection impedance by subtracting the first self-impedance from the first coupling impedance, and calculates the second reflection impedance by subtracting the first self-impedance from the second coupling impedance. Claim 5 In paragraph 1, the VNA is in a state where the transmitting end module and the relay resonator are combined, and the first S 11 Measure the parameters, and the first S 11 The parameter is converted into impedance to measure the first coupling impedance, and the VNA is in a state where the transmitting end module, the relay resonator, and the receiving end sensor are coupled, and the second S 11 Measure the parameters, and the second S 11 A wireless sensing device that converts a parameter into an impedance and measures the second coupling impedance. Claim 6 A wireless sensing device according to claim 1, wherein the relay resonator is positioned closer to the receiving sensor than to the transmitting module. Claim 7 A wireless sensing device comprising a receiving end sensor including a first LC resonant circuit and a transmitting end module, wherein the transmitting end module includes an RF source that outputs a radio frequency (RF) signal, a second LC resonant circuit that receives the RF signal at an input end, a load resistor connected to an output end of the second LC resonant circuit, an RF core circuit that converts a first voltage at the input end and a second voltage at the output end into a gain between the first voltage and the second voltage and a phase difference between the first voltage and the second voltage, and a processor that determines the resonant frequency of the receiving end sensor based on the gain and the phase difference. Claim 8 A wireless sensing device according to claim 7, wherein the processor calculates the impedance in the coupled state of the receiving end sensor based on the gain and the phase difference, and determines the resonant frequency based on the impedance. Claim 9 A wireless sensing device according to claim 8, wherein the processor determines the frequency of the RF signal at which the real component of the impedance becomes maximum as the resonance frequency. Claim 10 A wireless sensing device according to claim 7, further comprising a circuit that performs impedance matching and low-band filtering on the RF signal output from the RF source. Claim 11 A wireless sensing device according to claim 7, comprising a third LC resonant circuit and further comprising a relay resonator connected between the transmitting module and the receiving sensor.

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