A passive wireless sensor based on piezoelectric resonator

Abstract

The present invention relates to the technical field of microwave resonators, and discloses a passive wireless sensor based on a piezoelectric resonator, including an input matching network, a resonant network and an output matching network, wherein the resonant network includes a piezoelectric resonator, an inductor and a nonlinear device, wherein the inductor is connected in series or in parallel with the nonlinear device, and the input end of the inductor is electrically connected to the input matching network, and the output end of the nonlinear device is respectively connected to the piezoelectric resonator and the output matching network. Since the natural frequency of the piezoelectric vibrator in the piezoelectric resonator is in an expressible relationship with the change of the physical quantity, the change of the physical quantity will cause the natural frequency of the piezoelectric vibrator to shift, resulting in a change in the resonant frequency, thereby realizing the collection and transmission of the physical quantity through the change in the resonant frequency. The present invention can realize that the piezoelectric resonator can generate a signal without relying on the change of external mechanical force, and has the characteristics of good frequency stability, high equivalent quality factor, high precision, strong anti-interference ability, etc.

Description

Technical Field

[0001] The invention relates to the technical field of microwave resonators, and in particular to a passive wireless sensor based on a piezoelectric resonator. Background Art

[0002] With the rapid development of the Internet of Things (IoT) and smart sensor technology, passive wireless sensors have been widely used in environmental monitoring, industrial automation, medical health, smart home and other fields. Passive wireless sensors have attracted more and more attention because they do not require external power supply and can work for a long time in harsh environments.

[0003] A piezoelectric resonator is a component that utilizes the properties of piezoelectric materials. When an external electric field acts on a piezoelectric material, the material will produce mechanical deformation. Conversely, when the material is subjected to mechanical force, an electric potential will be generated at both ends. This effect is called the piezoelectric effect. Piezoelectric resonators use this effect to convert electrical signals into mechanical vibration signals. Its natural vibration frequency is related to the material and structure. The energy exchange efficiency is highest at a specific frequency, so it has the advantages of good frequency stability and high quality factor.

[0004] In the prior art, passive wireless sensors based on piezoelectric resonators have made some research progress. For example, some sensors are based on quartz crystal resonators, which detect temperature by changing the vibration frequency of the quartz crystal caused by temperature changes; other sensors use surface acoustic wave resonators, which measure pressure by changing the vibration frequency of the surface acoustic wave resonator caused by pressure changes.

[0005] However, the working principle of these sensors mainly depends on the change of external mechanical force or physical quantity such as temperature, which requires that the sensor can only generate signals when there is an external change. This characteristic of relying on the change of external mechanical force limits the application scope and flexibility of the sensor, especially in certain environments where no external mechanical force changes, the performance of the sensor will be greatly affected. In addition, these sensors also have certain limitations in terms of frequency stability, anti-interference ability and energy loss. Summary of the invention

[0006] In order to solve the above problems, the present invention proposes a passive wireless sensor based on a piezoelectric resonator, which can realize that the piezoelectric resonator can generate a signal without relying on changes in external mechanical force, thereby solving the application limitations of the above background technology.

[0007] The technical solution adopted by the present invention is as follows:

[0008] A passive wireless sensor based on a piezoelectric resonator comprises an input matching network, a resonance network and an output matching network, wherein the resonance network comprises a piezoelectric resonator, an inductor and a nonlinear device, wherein the inductor is connected in series or in parallel with the nonlinear device, and the input end of the inductor is electrically connected to the input matching network, and the output end of the nonlinear device is respectively connected to the piezoelectric resonator and the output matching network; wherein the input matching network is configured to The alternating signal is impedance matched, and a tuning wave is generated through the inductor and nonlinear devices; when the tuning wave frequency is the same as the natural vibration frequency of the piezoelectric vibrator in the piezoelectric resonator, the piezoelectric vibrator resonates, and based on the piezoelectric effect, the mechanical vibration in the piezoelectric vibrator will be converted into a frequency of The electrical signal of The signal will generate a corresponding mixing signal due to the nonlinear characteristics of the nonlinear device, and finally be output after being filtered through the output matching network.

[0009] Furthermore, the natural frequency of the piezoelectric vibrator in the piezoelectric resonator is in an expressible relationship with the change of the physical quantity. The change of the physical quantity will cause the natural frequency of the piezoelectric vibrator to shift, resulting in the resonant frequency changes, thereby passing the resonant frequency The changes in the physical quantity are used to realize the collection and transmission of physical quantities.

[0010] Furthermore, physical quantities that have an expressible relationship with the natural frequency of the piezoelectric vibrator in the piezoelectric resonator include, but are not limited to, temperature and pressure.

[0011] Furthermore, due to the nonlinear characteristics of nonlinear devices, the frequency is The signal will generate a corresponding mixed signal, and the mixed signal includes an up-converted signal, i.e. a sum frequency signal, a down-converted signal, i.e. a difference frequency signal, and a multiplied signal of the sum and difference frequencies.

[0012] Furthermore, the frequency of the mixing signal complies with the Menley-Lowe formula:

[0013]

[0014]

[0015] in, is the frequency The signal power of , m, n are integers, and and and The following relations are satisfied:

[0016] .

[0017] Furthermore, the frequency of the alternating signal The frequency of the tuning wave generated in the circuit with the same natural frequency as the piezoelectric resonator is higher than the preset frequency, so that the excitation frequency of the piezoelectric resonator is higher than the second preset frequency, and finally a stable Frequency signal.

[0018] Furthermore, the material of the piezoelectric vibrator in the piezoelectric resonator includes but is not limited to ceramics and quartz crystal.

[0019] Furthermore, the nonlinear device includes but is not limited to a conventional diode, a varactor diode, a transistor and a field effect transistor.

[0020] Furthermore, the inductor can be replaced by a parasitic inductance in the circuit.

[0021] Furthermore, the feeding method of the alternating signal includes: directly feeding it through a signal source, or feeding it after receiving it through an antenna.

[0022] The beneficial effects of the present invention are:

[0023] 1. Good frequency stability: Piezoelectric resonator has extremely high frequency stability. By designing a reasonable circuit structure, the stability and reliability of the sensor output signal can be ensured.

[0024] 2. High quality factor: The high quality factor (Q value) of the piezoelectric resonator reduces energy loss and improves the sensitivity and detection accuracy of the sensor.

[0025] 3. Strong anti-interference ability: Through the optimized design of input matching network and output matching network, the influence of external electromagnetic interference on the sensor is effectively reduced to ensure the purity of the signal.

[0026] 4. High precision: The natural frequency of the piezoelectric resonator has an expressible relationship with the change of physical quantity. By accurately measuring the slight change of frequency, high-precision physical quantity detection can be achieved.

[0027] 5. No need for external mechanical force changes: The sensor design of the present invention utilizes the nonlinear characteristics of the varactor diode. Through the resonance effect caused when the frequency of the tuning wave is consistent with the natural frequency of the piezoelectric resonator, the signal can be generated without relying on external mechanical force changes, which expands the application range and flexibility of the sensor. At the same time, when external physical quantities such as temperature and pressure change, the change of physical quantities can be accurately measured through the frequency drift.

[0028] 6. Passive design: No external power supply is required, and the energy of the external input signal is used to realize the operation of the sensor, which simplifies the structure and use environment of the sensor and is particularly suitable for use in harsh environments.

[0029] In summary, the passive wireless sensor based on piezoelectric resonator of the present invention makes full use of the excellent properties of piezoelectric materials and the nonlinear characteristics of nonlinear devices, realizes high-precision detection of physical quantities through frequency resonance effect, and has significant advantages in frequency stability, high quality factor, anti-interference ability, accuracy, etc. At the same time, it can generate signals without relying on changes in external mechanical force, which makes up for the shortcomings of the existing technology and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic diagram of a passive wireless sensor based on a piezoelectric resonator in Example 1.

[0031] Figure 2 This is the simulated spectrum diagram after the input signal passes through the inductor and varactor diode.

[0032] Figure 3 This is the measured spectrum diagram after the input signal passes through the inductor and varactor diode.

[0033] Figure 4 This is a schematic diagram of a passive wireless sensor based on a piezoelectric resonator in Example 2.

[0034] Figure 5 This is the measured spectrum diagram after mixing the input frequency and the piezoelectric resonator frequency based on transistor.

[0035] Reference numerals: - Inductors, - Varactor diode, -Piezoelectric resonator, Q-transistor. DETAILED DESCRIPTION

[0036] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, the specific implementation methods of the present invention are now described. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0037] Example 1

[0038] This embodiment provides a passive wireless sensor based on a piezoelectric resonator, and uses a varactor diode as a nonlinear device for illustration. Figure 1 As shown, the passive wireless sensor of this embodiment includes an input matching network, an inductor , Varactor diode , Piezoelectric Resonator , output matching network and other necessary circuit components. The input frequency is The alternating signal is impedance matched through the input matching network, and the inductor is connected in series or in parallel with the varactor diode. , generating rich tuning waves. When the tuning wave frequency is equal to the piezoelectric resonator When the natural vibration frequency of the piezoelectric vibrator is the same, the piezoelectric vibrator resonates, and based on the piezoelectric effect, the extremely weak mechanical vibration in the piezoelectric vibrator is converted into a frequency of At the same time, the frequency signal in the circuit Since the varactor diode The nonlinear characteristics of the mixed signal will produce a series of mixing signals, the frequency of which conforms to the law of the Manley-Rowe formula, and finally is output after being filtered by the output matching network.

[0039] It should be noted that piezoelectric resonators The natural frequency of the piezoelectric vibrator in the system is expressibly related to the change of physical quantities (such as temperature, pressure, etc.). The change of physical quantities will cause the natural frequency of the piezoelectric vibrator to shift, thus causing the resonant frequency to Therefore, the physical quantity can be collected and transmitted by analyzing the frequency change.

[0040] When an alternating signal is input, due to the varactor diode Due to the nonlinear characteristics, a variety of harmonic waves will be generated in the circuit, such as Figure 2 The following is the harmonic wave generated in the simulation circuit. Figure 3 Shown is the tuned wave observed in the actual circuit.

[0041] when When two signals pass through the varactor diode, due to the nonlinear characteristics of the diode, the output signal contains the sum and difference frequencies of the original signal frequencies as well as their multiples and divisions, and satisfies the Menrerow relationship:

[0042]

[0043]

[0044] in, is the frequency The signal power of , m, n are integers, and and and The following relations are satisfied:

[0045] .

[0046] Preferably, within a certain input frequency range, the input alternating signal frequency The higher the piezoelectric resonator generated in the circuit The frequency of the occurrence of the tuning wave with the same natural frequency is also faster, which has an impact on the piezoelectric resonator. The faster the excitation frequency, the more stable the In addition, the input alternating signal can be fed directly through the signal source or fed after being received by the antenna.

[0047] Preferably, the piezoelectric resonator The piezoelectric vibrator material can be ceramic or dielectric materials such as quartz crystal materials.

[0048] Preferably, the inductor It can be a direct electronic component or a parasitic inductor in the circuit. Due to different related parameters, the circuit performance will also be different.

[0049] Example 2

[0050] This embodiment provides a passive wireless sensor based on a piezoelectric resonator, and uses a transistor as a nonlinear device for illustration. Figure 4 As shown, the passive wireless sensor of this embodiment includes an input matching network, an inductor , transistor Q, piezoelectric resonator , output matching network and other necessary circuit components. Among them, the drain terminal of transistor Q is connected to the input matching network and connected in series with the inductor , the source terminal is connected to the output matching network and grounding components, and the gate terminal is connected to the voltage-controlled resonator The input matching network is designed to achieve impedance matching between the input signal and the circuit. The input signal passes through the inductor and the internal junction capacitance of transistor Q generate rich tuning waves, which excite the gate voltage-controlled resonator resonance; at the same time, according to the nonlinear characteristics of transistor Q, the input signal and the voltage-controlled resonator The frequency will generate the mixing signal. The output matching network connected to the source terminal of transistor Q is used to match the relevant parameters in the circuit.

[0051] Preferably, the voltage-controlled resonator of this embodiment is a ceramic resonator with a natural frequency of 16 MHz. Within a certain temperature range, the frequency changes linearly with the temperature. Figure 5 As shown in the figure, the input signal frequency is 800MHz, and the mixing frequencies generated in the circuit are 784MHz and 816MHz. When the temperature changes, it will cause the ceramic resonator frequency to drift, and the mixing signal frequency will also change accordingly, so the temperature can be collected and transmitted.

[0052] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A passive wireless sensor based on a piezoelectric resonator, characterized in that: It includes an input matching network, a resonance network and an output matching network, wherein the resonance network includes a piezoelectric resonator, an inductor and a nonlinear device, the inductor is connected in series or in parallel with the nonlinear device, and the input end of the inductor is electrically connected to the input matching network, and the output end of the nonlinear device is respectively connected to the piezoelectric resonator and the output matching network; The input matching network is configured to The alternating signal is impedance matched, and a tuning wave is generated through the inductor and nonlinear devices; when the tuning wave frequency is the same as the natural vibration frequency of the piezoelectric vibrator in the piezoelectric resonator, the piezoelectric vibrator resonates, and based on the piezoelectric effect, the mechanical vibration in the piezoelectric vibrator will be converted into a frequency of The electrical signal of The signal will generate a corresponding mixing signal due to the nonlinear characteristics of the nonlinear device, and finally be output after being filtered by the output matching network; The natural frequency of the piezoelectric vibrator in the piezoelectric resonator is in an expressible relationship with the change of the physical quantity. The change of the physical quantity will cause the natural frequency of the piezoelectric vibrator to shift, resulting in the resonance frequency changes, thereby passing the resonant frequency The changes in the physical quantity can realize the collection and transmission of physical quantity; The nonlinear device includes a varactor diode, and the inductor is connected in series or in parallel with the varactor diode; The frequency of the mixing signal conforms to the Menley-Lowe formula: in, is the frequency The signal power of , m, n are integers, and and and The following relations are satisfied: ； The frequency of the alternating signal The frequency of the tuning wave generated in the circuit with the same natural frequency as the piezoelectric resonator is higher than the preset frequency, so that the excitation frequency of the piezoelectric resonator is higher than the second preset frequency, and finally a stable Frequency signal.

2. A passive wireless sensor based on a piezoelectric resonator according to claim 1, characterized in that: Physical quantities that have an expressible relationship with the natural frequency of the piezoelectric vibrator in the piezoelectric resonator include, but are not limited to, temperature and pressure.

3. A passive wireless sensor based on a piezoelectric resonator according to claim 1, characterized in that: Due to the nonlinear characteristics of nonlinear devices, the frequency is The signal will generate a corresponding mixed signal, and the mixed signal includes an up-converted signal, i.e. a sum frequency signal, a down-converted signal, i.e. a difference frequency signal, and a multiplied signal of the sum and difference frequencies.

4. A passive wireless sensor based on a piezoelectric resonator according to claim 1, characterized in that: The material of the piezoelectric vibrator in the piezoelectric resonator includes but is not limited to ceramics and quartz crystal.

5. A passive wireless sensor based on a piezoelectric resonator according to claim 1, characterized in that: The inductor can be replaced by a parasitic inductance in the circuit.

6. A passive wireless sensor based on a piezoelectric resonator according to claim 1, characterized in that: The feeding method of the alternating signal includes: directly feeding it through a signal source, or feeding it after receiving it through an antenna.

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