Wireless passive sensing system based on complex coupling and humidity measuring method

Abstract

The invention discloses a wireless passive sensing system based on complex coupling and a humidity measurement method, a coupling mode of complex coupling is realized by adding a loss end in an APT symmetric system and using disturbance applied to an adjustable capacitor C3, so that the system is always in a broken area, the working frequency can generate higher sensitivity on both sides of an EP point, and the humidity measurement accuracy is improved. Bidirectional detection of the APT symmetric system at the EP point is realized; meanwhile, a relay component is added in the PT symmetric system, and bidirectional detection of the PT symmetric system at an EP point is realized through disturbance applied to an adjustable resistor R2; besides, by realizing a high-sensitivity sensing mode on the two sides of the EP point, the application capability of the wireless sensing system in various detection situations is greatly improved, and a foundation is laid for wider application of the wireless sensing system in the fields of environmental monitoring, biomedical detection and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of wireless sensors, and in particular relates to a wireless passive sensor system based on complex coupling and a humidity measurement method. Background Art

[0002] The non-Hermitian Hamiltonian that describes open physical systems has gradually attracted attention, and its typical representatives are the parity-time (PT) symmetric system and the anti-parity-time (APT) symmetric system. Although the eigenvalues ​​of these systems exist in the non-real eigenvalue spectrum, they are still observable. As a result, the application and research of symmetric systems in many fields, such as sensing technology, are becoming increasingly important. Especially at the EP point, due to the simultaneous degeneration of its eigenvalues ​​and eigenvectors, the eigenvalues ​​of the symmetric system are extremely sensitive to perturbations. In the fields of optics, acoustics, and electronics, research around the EP point has achieved remarkable results. Usually, the response of the system eigenvalue to the applied disturbance ε is proportional to the 1 / nth power of the disturbance (ε n ), where n is the order of the system. Although studies have shown that classical and quantum noise may expand the characteristic spectrum at these points, thereby affecting the signal-to-noise ratio, the latest research on nonlinear structures has proposed a different view.

[0003] In the field of electronics, the current anti-parity-time (APT) symmetric structure exists through dimers with coupling in the form of imaginary numbers. However, this form of symmetric structure can only be achieved through the connection of wired resistors in the circuit, which greatly limits the application of symmetric systems in wireless sensing environments. Later, some people proposed to use two gain ends and one loss end to construct an APT symmetric structure. In this structure, the coupling is real coupling, and a wireless structure in the circuit is constructed. However, in this wireless APT symmetric structure, when the loss end resistor is used as a sensing device, only one-way sensing is achieved. In this article, the bidirectional sensing system constructed using the symmetric structure of the combination of PT and APT has the disadvantages of many devices and difficult adjustment. Most of the existing PT symmetric structures and APT symmetric structures have the following problems:

[0004] 1. In the past, single Anti-PT symmetrical circuit structures and PT symmetrical structures could only perform unidirectional sensing at the EP point. Specifically, when a certain component is used as a sensor, it can only detect positive or negative disturbances when affected by disturbances. This limits their effectiveness and practicality in certain application scenarios that have high requirements for comprehensive disturbance detection. 2. In the coupling system, the coupling coefficients in previous structures are all pure real numbers or pure imaginary numbers in the system Hamiltonian, and complex coupling is not achieved, which limits the diversity of multi-coil coupling. Summary of the invention

[0005] The object of the present invention is to provide a wireless passive sensing system and a humidity measurement method based on complex coupling.

[0006] In the first aspect, the present invention provides a wireless passive sensing system based on complex coupling, which includes a gain component, a relay component and a loss component; the gain component includes a capacitor C1, an inductor L1 and a negative resistor R1; the relay component includes a capacitor C2, an inductor L2 and a resistor R2; the loss component includes a capacitor C3, an inductor L3 and a resistor R3; the inductance values ​​of the inductor L1, the inductor L2 and the inductor L3 are equal; the coupling rate κ between the gain component and the loss component 13 , and the coupling rate between the relay component and the loss component κ 23 equal, and as the inherent coupling rate κ0; the natural frequency of the gain component ω 11 , the natural frequency of the relay component ω 12 and the natural frequency ω of the lossy component 13 are equal and serve as the reference natural frequency ω0; During operation, the inherent coupling rate κ0=2 -0.5 γ3; wherein γ3 is the loss rate of the loss component; and the measured parameter is measured according to the change in the operating frequency caused by applying a disturbance ε to the resistor R2 based on the measured parameter.

[0007] Preferably, the gain rate of the gain component is greater than the loss rate of the loss component.

[0008] Preferably, the negative resistor adopts one of a current-type or voltage-type feedback operational amplifier, a half-bridge inverter, and a full-bridge inverter.

[0009] Preferably, the expression of the operating frequency ω is: Among them, g 11 is the gain ratio of the gain component.

[0010] In a second aspect, the present invention provides another wireless passive sensing system based on complex coupling, which includes a source end, a source end and a loss end; the source end includes a capacitor C1, an inductor L1 and a negative resistor R1; the source end includes a capacitor C2, an inductor L2 and a negative resistor R2; the loss end includes a capacitor C3 and an inductor L3; the inductance values ​​of the inductor L1, the inductor L2 and the inductor L3 are equal; the gain rate g of the source end 21 The gain ratio g with the source end 22 equal, and as the intrinsic gain rate g0; the coupling rate between the source and loss ends κ 13 , and the coupling rate between the source and loss ends κ23 are equal and serve as the intrinsic coupling rate κ0; During operation, the inherent coupling rate κ0 2 =δγ3; where γ3 is the loss rate at the loss end; δ is the natural frequency difference, δ=(ω 21 –ω 22 ) / 2;ω 21 and ω 22 are the natural frequencies of the source end and the source end respectively; according to the change of the operating frequency caused by the disturbance ε applied to the capacitor C3 by the measured parameter, the measured parameter is measured.

[0011] Preferably, the gain rate of the source end and the source end is greater than the loss rate of the loss end.

[0012] Preferably, the expression of the operating frequency ω is: Wherein, γ3 is the loss rate of the loss component.

[0013] Preferably, the expression of the inherent gain rate g0 is: .

[0014] Preferably, the negative resistor adopts one of a current-type or voltage-type feedback operational amplifier, a half-bridge inverter, and a full-bridge inverter.

[0015] In a third aspect, the present invention provides a humidity measurement method, which uses the above-mentioned wireless passive sensing system, and the humidity measurement is specifically as follows: A wireless passive sensing system is used to detect the humidity of the measured area. According to the change of the resistance R2 of the relay component or the capacitance C3 of the loss end caused by the humidity change, the working frequency of the wireless passive sensing system is detected to obtain the corresponding humidity.

[0016] The present invention has the following beneficial effects: 1. The present invention adds a loss end in the APT symmetrical system and uses the disturbance applied to the adjustable capacitor C3 to realize the coupling mode of complex coupling, so that the system is always in the broken area, and the operating frequency can produce high sensitivity on both sides of the EP point, thereby realizing the bidirectional detection of the APT symmetrical system at the EP point; at the same time, the present invention adds a relay component in the PT symmetrical system, and realizes the bidirectional detection of the PT symmetrical system at the EP point by applying the disturbance to the adjustable resistor R2.

[0017] 2. The present invention greatly improves the application capability of wireless sensing systems in various detection scenarios by realizing high-sensitivity sensing on both sides of the EP point. In a complex electromagnetic environment, the traditional symmetrical system can only perform limited sensing on a specific direction or a specific type of disturbance, while the present invention can simultaneously realize high-sensitivity detection on both sides of the EP point, and can accurately capture small changes in both positive and negative directions, thus laying the foundation for the wider application of wireless sensing systems in fields such as environmental monitoring and biomedical testing.

[0018] 3. The present invention realizes complex coupling by adding disturbances, making the information transmission between coils more efficient and flexible, and can adapt to different application scenarios and needs, further expanding the application potential of these two symmetrical systems in the fields of communication, electronic circuit design, etc., and providing strong theoretical support for the innovation and development of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a circuit model diagram of Example 1 of the present invention.

[0020] Figure 2 This is a schematic diagram of the change of the system's operating frequency with disturbance when different disturbances are added to the traditional PT system.

[0021] Figure 3 Schematic diagram of the change state of the operating frequency following disturbance in Example 1 of the present invention.

[0022] Figure 4 Schematic diagram of the transformation state of the operating frequency under different disturbances in Example 1 of the present invention; wherein (a) is the real part of the operating frequency; and (b) is the imaginary part of the operating frequency.

[0023] Figure 5 Schematic diagram of the transformation state of the gain rate with disturbance under different disturbances in Example 1 of the present invention; wherein (a) is the real part of the inherent gain rate; and (b) is the imaginary part of the inherent gain rate.

[0024] Figure 6 This is a circuit model diagram of Example 1 of the present invention.

[0025] Figure 7 This is a schematic diagram of the change of the system operating frequency with disturbance when different disturbances are added to the traditional APT system.

[0026] Figure 8 Schematic diagram of the change state of the operating frequency following disturbance in Embodiment 2 of the present invention.

[0027] Fig. 9Schematic diagram of the transformation state of the operating frequency under different disturbances in Example 2 of the present invention; wherein (a) is the real part of the operating frequency; and (b) is the imaginary part of the operating frequency.

[0028] Fig.10 Schematic diagram of the transformation state of the inherent gain rate under different disturbances in Example 2 of the present invention; wherein (a) is the real part of the inherent gain rate; and (b) is the imaginary part of the inherent gain rate.

[0029] Fig.11 Schematic diagram of the experimental system of Example 2 of the present invention. DETAILED DESCRIPTION

[0030] The present invention will be further described below in conjunction with the accompanying drawings.

[0031] Example 1 like Figure 1 As shown, a wireless passive sensing system based on complex coupling realizes high-sensitivity detection on both sides of the EP point based on the PT symmetric system. The wireless passive sensing system includes a gain component, a relay component and a loss component; the gain component, the relay component and the loss component are all resonators; the gain component includes a capacitor C1, an inductor L1 and a negative resistor R1 connected in series in sequence; the relay component includes a capacitor C2, an inductor L2 and a resistor R2 connected in series in sequence; the loss component includes a capacitor C3, an inductor L3 and a resistor R3 connected in series in sequence. The inductance values ​​of the inductors L1, L2 and L3 are equal; the coupling rate κ between the gain component and the loss component 13 , and the coupling rate between the relay component and the loss component κ 23 equal, and as the inherent coupling rate κ0; the coupling rate between the gain component and the relay component is negligible; the inherent frequency ω of the gain component 11 , the natural frequency of the relay component ω 12 and the natural frequency ω of the lossy component 13 are equal and serve as the reference natural frequency ω0; the gain rate of the gain component is greater than the loss rate of the loss component, so that the system can oscillate more easily.

[0032] In this embodiment, the circuit structure of the negative resistance source adopts one of a current-type or voltage-type feedback operational amplifier, a half-bridge inverter, and a full-bridge inverter.

[0033] like Figure 2 As shown in the figure, in the existing PT symmetric system, the coupling coefficient is a real number. If the same real number perturbation ε is added to the coupling coefficient κ , then in the PT-breaking region, the operating frequency of the symmetric system is degenerate, which means that under this disturbance, the symmetric system can only achieve one-way detection at the EP point. If the same imaginary perturbation ε' is added to the coupling coefficient κ, a complex coupling is formed between the two resonators, and the operating frequency of the PT symmetric system is split on both sides of the EP point. Since there is a real coupling between the two resonators in the dimer form of the existing PT symmetric system, it is difficult to directly add imaginary coupling.

[0034] like Figure 3 As shown in Figure 1, complex coupling is achieved by adding a relay component to the existing PT symmetric system and mapping the expression of the relay component into the expressions of the remaining two resonators. Hamiltonian of the wireless passive sensing system consisting of three resonators The corresponding solution The expression is:

[0035] Among them, g 11 is the gain rate of the gain component; γ3 is the loss rate of the loss component.

[0036] Gain ratio g of the gain component 11 The expression is: In some embodiments, the gain component includes a capacitor C1, an inductor L1, and a negative resistor R1 connected in parallel, and the gain ratio g of the gain component is 11 The expression is: From the eigenvalues ​​solved for the Hamiltonian, we can get the EP point condition of the PT symmetric system as κ0=2 -0.5 γ3.

[0037] If a loss disturbance ε is applied to the relay component, the Schrödinger-like equation of the sensing system is obtained based on the coupled mode theory as follows: Among them, a1, a2, a3 are the energy modes of the gain component, relay component, and loss component respectively; is the Hamiltonian after the perturbation ε is applied, and its expression is: The Schrödinger equation for the relay component is redefined as a2= (κ0a1+ κ0a3) / (ω-ω0-iε). The energy mode a2 of the relay component is integrated into the coupled mode equation of the gain component and the loss component; m Apply a rotation transformation －iωt , and get a' m = a m e －iωt; Where m = 1, 2, 3. When the disturbance is small, that is (ω-ω0) 2 +ε 2 ≈(ω-ω0) 2 , obtain the Hamiltonian H' of the sensing system SPT( ε ) The expression is:

[0038] Comparison of Hamiltonian and , it can be seen that the added disturbance mainly affects the equivalent gain and loss of the system and gives a complex disturbance component to the coupling coefficient. For the gain and loss of the symmetrical system, due to the adaptability of the negative resistance, this small disturbance has almost no effect on the system operating frequency, but the complex coupling coefficient will bring different changes. Let x = ω-ω0, and the expression of the characteristic equation of the system under disturbance is obtained as:

[0039] After expanding equation (9) and separating the real and imaginary, the expression of the system's operating frequency ω is obtained as follows: like Figure 4 and 5 As shown in the figure, there are five solutions for the working frequency ω; since the actual working frequency is a pure real number, only the solution with an imaginary number of 0 is taken. For the case of disturbance ε<0, solutions ω3 and ω4 do not meet the requirements of pure real numbers, as shown in the red dashed line in the figure, so they cannot be obtained when taking values. At the same time, the gains corresponding to all solutions should also be pure real numbers. Since the PT symmetric system has only one independent source coil, the PT symmetric system will only choose one of these solutions in the actual circuit. For solutions with the same gain such as ω1 and ω2, a detuning amount that far exceeds the disturbance amount can be used to offset it to another solution. In the actual circuit, the system will still choose a gain with lower energy to work.

[0040] Example 2 like Figure 6As shown, a wireless passive sensing system based on complex coupling realizes high-sensitivity detection on both sides of the EP point based on the APT symmetric system. The wireless passive sensing system includes a source end, a source end and a loss end; the source end, the source end and the loss end are all resonators; the source end includes a capacitor C1, an inductor L1 and a negative resistor R1 connected in series in sequence; the source end includes a capacitor C2, an inductor L2 and a negative resistor R2 connected in series in sequence; the loss end includes a capacitor C3 and an inductor L3 connected in series in sequence. The inductance values ​​of the inductors L1, L2 and L3 are equal; the gain rate g of the source end 21 The gain ratio g with the source end 22 equal, and as the intrinsic gain rate g0; the coupling rate between the source and loss ends κ 13 , and the coupling rate between the source and loss ends κ 23 are equal and serve as the inherent coupling rate κ0; the gain rate of the source end and the source end is greater than the loss rate of the loss end, so that the system is easier to oscillate.

[0041] like Figure 7 As shown in the figure, in the existing APT symmetric system, the coupling coefficient is a pure imaginary number. If the same imaginary number ε is added to the coupling coefficient κ , then in the APT symmetric region, the operating frequency of the symmetric system is degenerate, and the symmetric system can only achieve one-way detection at the EP point. If the same real number ε' is added to the coupling coefficient κ , a complex coupling is formed between the two resonators, and the operating frequency of the APT symmetric system is split on both sides of the EP point. Since there is an imaginary coupling between the two resonators in the dimer form of the existing APT symmetric system, it is difficult to directly add real coupling.

[0042] like Figure 8 As shown in the figure, by adding a lossy resonator to the existing APT symmetric system and using the real coupling between the lossy resonator and the source end to equivalently couple the imaginary coupling between the two source ends; by directly operating the lossy resonator, the coupling coefficient in the APT symmetric system is equivalently affected. Hamiltonian of a wireless passive sensing system consisting of three resonators The corresponding solution The expression is:

[0043] Among them, δ is the natural frequency difference, δ=(ω 21 –ω 22 ) / 2;ω 21 and ω 22 are the natural frequencies of the source end and the source end respectively; γ3 is the loss rate of the loss end; ω0 is the reference natural frequency, ω0=(ω 21 +ω 22) / 2; ω is the operating frequency of the sensor system.

[0044] If a disturbance ε is applied to the natural resonant frequency of the loss end, the Schrödinger-like equation of the sensing system is obtained based on the coupled mode theory as follows: Among them, a1, a2, and a3 are the energy modes of the source, source, and loss ends respectively; is the Hamiltonian after the perturbation ε is applied, and its expression is: Among them, ω 23 is the natural frequency of the loss end.

[0045] When the sensing system operates at the EP point, κ0 2 =δγ3, the operating frequency is centered on the reference natural frequency ω0; assuming the operating frequency is close to the reference natural frequency ω0, the difference (ω - ω0) will be much smaller than the natural frequency difference δ of the system. Since the energy mode a3 at the loss end can be defined as a3=κ 13 a1 / (ω-ω0-δ+ iγ3), then the energy mode a3 at the loss end is simplified to a3=-κ0a1 / (δ-iγ3). The energy mode a3 at the loss end is integrated into the coupled mode equation between the source end and the source end; m Apply a rotation transformation －iωt , and get a' m = a m e －iωt ; Where m = 1, 2, 3; Get the Hamiltonian H' of the sensor system SAPT( ε ) The expression is:

[0046] Assuming that the perturbation ε is very small, that is, the perturbation ε <5%, then ε 2 +γ3 2 ≈γ3 2 ; Let ε' = ε / γ3 2 , Hamiltonian H' SAPT ( ε ) Simplified to: Comparison of Hamiltonian and , it can be seen that the added disturbance mainly affects the offset of the overall center frequency of the system and gives a complex disturbance component to the coupling coefficient. For the operating frequency of the symmetrical system, the overall offset of the center frequency may not seem sensitive, but the complex coupling coefficient will bring different changes. Let x = ω-ω0, and the expression of the characteristic equation of the system under disturbance is obtained as:

[0047] After expanding equation (20) and separating the real and imaginary, the expression of the system's operating frequency ω is obtained as follows: from Fig. 9 From (a) and (b) in Figure 2, we can see that The two radicals contained in it form a conjugate complex number, namely The solutions ω3 and ω4 generated by taking the negative sign in the equation are the same in real part and have opposite non-zero imaginary parts. Since the actual operating frequency is a pure real number, only The solutions ω1 and ω2 generated by taking the positive sign are used as the operating frequency of the system.

[0048] According to equations (20) and (21), the expression of the inherent gain rate g0 is obtained as follows: The real and imaginary parts of the inherent gain rate change with the disturbance as shown in Fig.10 As shown in (a) and (b) in , since ω3 and ω4 do not hold, the inherent gain ratio is taken as g1 and g2.

[0049] When ε = 0, the system is in a symmetrical state; when ε ≠ 0, the system is in the broken region regardless of whether the disturbance is positive or negative. In the broken region, the two operating frequencies correspond to the working states of the two high-frequency and low-frequency resonant inductors. In the actual circuit, these two states are superimposed. The inconsistent working frequencies of the high-frequency and low-frequency resonant coils also lead to inconsistent corresponding feedback gains.

[0050] In order to evaluate the sensitivity of the anti-parity-time (APT) symmetric system, the frequency difference Δω between the offset frequency and the frequency at the outlier point (EP) ω0 is obtained. SAPT(ε) According to the critical coupling condition δ=κ0 2 / γ3 Get the sensitivity of disturbance in different regions The expression is:

[0051] Different coefficients are observed for the cases of ε>0 and ε<0, but the sensitivity order is |ε| in both cases. 0.5 It is shown that the APT symmetric system can realize the sensing function of bidirectional same-order sensitivity through the complex perturbation in the coupling coefficient.

[0052] like Fig.11 As shown in the figure, an RLC resonant circuit is used to realize the bidirectional detection function under complex coupling. In this model, the loss is realized by the positive resistance, while the gain is realized by the negative resistance composed of the amplifier and the resistor. The negative resistance value is defined as R = -(R f2 R 0) / R f1 ; Among them, R f1 and R f2 The resistance values ​​of the two resistors in the negative resistance network. For each resonator m, its natural resonant frequency is defined as ω m = 1 / √(L m C m ), and the natural frequency difference δ=(ω 21 –ω 22 ) / 2, reference natural frequency ω0=(ω 21 +ω 22 ) / 2. The gain rate or loss rate is quantified as γ m = 0.5ω m G m , among which, Г m is the gain or loss of each resonator. At the gain end, the gain is calculated as |R m |√(C m / L m ), the different coupling coefficients are defined as κ 13 = 0.5ω0k 13 , κ 23 = 0.5ω0k 23 . k 13 and k 23 The values ​​of L 13 / (L1 L3) and L 23 / (L2L3);L 13 and L 23 Indicates mutual induction.

[0053] The two gain terminals and loss terminals are in series. The two gain modules and loss modules are integrated into two PCB boards respectively. The two PCB boards are fixed with plastic screws, and the spacing between them is precisely controlled by plastic spacers with a minimum error of 0.1mm. This arrangement ensures that the boards remain parallel, which is important for maintaining k 13 and k 24The uniformity between them is crucial. The inductance values ​​of inductors L1, L2, and L3 are all set to 10uH. The capacitance values ​​of capacitors C1 and C2 are set to 205.5pF and 236.7pF, respectively, and are compensated using fine-tuning capacitors. This configuration produces the inherent resonant frequencies ω1=22.06-Mrad / s and ω2=20.55-Mrad / s. C3 is used as a variable element and is adjusted by an adjustable capacitor. The initial setting is 220pF, then ω3=21.3-Mrad / s to position the system at the EP point of the system. The operational amplifier (THS3001, TI) is configured into a negative resistance network with resistors Rf1=5Ω, Rf2=47Ω, and Rf3=200Ω. Inductor L3 is used as a load coil, in which no additional resistance is added, and its own parasitic resistance is used as the load value to improve the system quality factor. In actual measurements, the parasitic resistance at the load end is measured to be 2Ω. Precision resistors with 0.1% tolerance are used to optimize the matching of the gain elements. In the process of locating the EP point, the natural frequency and gain / loss level of each resonator are first fine-tuned, and then the distance between the two boards is calibrated based on the distance through the shim. Finally, the operating frequency of the system is determined by monitoring a coil on the loss side with a spectrum analyzer.

[0054] When the disturbance ε appears in the case of capacitor C2, the experimental results are as follows Fig.11 The experimental results shown in the figure are obtained by summarizing the average values ​​of multiple sets of data. Fig.11 It can be seen that there is a system operating frequency jump in a very small part near the EP point. This is due to the choice of energy levels between the gain values ​​of the two gain ends in practice, and the gain will find the minimum energy between the two solutions.

[0055] In the actual circuit, the operating frequency of the system shows a small range of locking phenomenon near the EP point. When ε<0, the system is locked to the low-frequency solution ω2; when ε>0, the system is locked to the low-frequency solution ω1. This is because when ε<0, g1>g2; and when ε>0, g1<g2. The gain of the system will always choose the eigenstate with lower energy level in the locked state. In the case of excessive disturbance, the system will generate two operating frequencies because the locked state is destroyed. These two frequencies exist simultaneously in the actual circuit, making the system waveform appear in the state of envelope wave.

[0056] The humidity of the measured area is measured by a wireless passive sensing system; the humidity sensing is simulated by sliding a variable capacitor device, which is equivalent to changing the capacitor at the loss end into a variable capacitor device that changes with humidity, so as to determine a precise environmental humidity value. The wireless passive sensing system uses different parameter values ​​to set the required humidity value and determines the humidity of the environment in the measured area by measuring the operating frequency. Since the APT symmetrical system has two operating frequencies in the broken area, when the inherent resonant frequency of the loss end is changed, the symmetrical system is in the broken area regardless of whether the disturbance is positive or negative. This also causes the system to have obvious frequency splitting as long as it is not near the EP point, which provides favorable conditions for accurately finding the humidity range. At the same time, the two-to-one APT symmetrical system also realizes the function of wireless sensing, which makes the APT symmetrical system suitable for more environments that require wireless sensing.

[0057] The implementation cases described above are only preferred implementation methods of the present invention, but the implementation methods of the present invention are not limited to the above implementation cases. Therefore, the changes, substitutions, combinations, and simplifications made under the principles of the present invention should all be equivalent replacement forms and are included in the protection scope of the present invention.

Claims

1. A wireless passive sensing system based on complex coupling, comprising a gain component, a relay component and a loss component; the gain component comprises a capacitor C1, an inductor L1 and a negative resistor R1; the relay component comprises a capacitor C2, an inductor L2 and a resistor R2; the loss component comprises a capacitor C3, an inductor L3 and a resistor R3; characterized in that: The inductance values ​​of the inductors L1, L2 and L3 are equal; the coupling rate κ between the gain component and the loss component 13 , and the coupling rate between the relay component and the loss component κ 23 equal, and as the inherent coupling rate κ0; the natural frequency of the gain component ω 11 , the natural frequency of the relay component ω 12 and the natural frequency ω of the lossy component 13 are equal and serve as the reference natural frequency ω0; During operation, the inherent coupling rate κ0=2 -0.5 γ3; wherein γ3 is the loss rate of the loss component; and the measured parameter is measured according to the change in the operating frequency caused by applying a disturbance ε to the resistor R2 based on the measured parameter.

2. A wireless passive sensing system based on complex coupling according to claim 1, characterized in that: The gain rate of the gain component is greater than the loss rate of the loss component.

3. The complex coupling-based wireless passive sensing system according to claim 1, characterized in that: The negative resistor adopts one of a current-type or voltage-type feedback operational amplifier, a half-bridge inverter, and a full-bridge inverter.

4. The wireless passive sensing system based on complex coupling according to claim 1, characterized in that: The expression of the operating frequency ω is: Among them, g 11 is the gain ratio of the gain component.

5. A wireless passive sensing system based on complex coupling, comprising a source end, a source end and a loss end; the source end comprises a capacitor C1, an inductor L1 and a negative resistor R1; the source end comprises a capacitor C2, an inductor L2 and a negative resistor R2; the loss end comprises a capacitor C3 and an inductor L3; characterized in that: The inductance values ​​of the inductors L1, L2 and L3 are equal; the gain rate g at the source end is 21 The gain ratio g with the source end 22 equal, and as the intrinsic gain rate g0; the coupling rate between the source and loss ends κ 13 , and the coupling rate between the source and loss ends κ 23 are equal and serve as the intrinsic coupling rate κ0; During operation, the inherent coupling rate κ0 2 =δγ3; where γ3 is the loss rate at the loss end; δ is the natural frequency difference, δ=(ω 21 –ω 22 ) / 2;ω 21 and ω 22 are the natural frequencies of the source end and the source end respectively; according to the change of the operating frequency caused by the disturbance ε applied to the capacitor C3 by the measured parameter, the measured parameter is measured.

6. A wireless passive sensing system based on complex coupling according to claim 5, characterized in that: The gain rate of the source end and the source end is greater than the loss rate of the loss end.

7. The wireless passive sensing system based on complex coupling according to claim 5, characterized in that: The expression of the operating frequency ω is: Where γ3 is the loss rate of the loss component; ω0 is the reference natural frequency, ω0=(ω 21 +ω 22 ) / 2.

8. The wireless passive sensing system based on complex coupling according to claim 7, characterized in that: The expression of the inherent gain rate g0 is: 。 9. The wireless passive sensing system based on complex coupling according to claim 5, characterized in that: The natural frequency difference δ < 3.5% ω0; ω0 is the reference natural frequency, ω0 = (ω 21 +ω 22 ) / 2.

10. A humidity measurement method, characterized in that: Using the wireless passive sensing system based on complex coupling as described in claim 1 or 5, the humidity measurement is specifically as follows: A wireless passive sensing system is used to detect the humidity of the measured area. According to the change of the adjustable resistor R2 in the relay component or the adjustable capacitor C3 in the loss end caused by the humidity change, the working frequency of the wireless passive sensing system is detected to obtain the corresponding humidity.

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