Microsecond short-duration pulse wireless acoustic wave sensing system

Abstract

The invention discloses a microsecond level short-time pulse wireless excitation acoustic wave sensing system, comprising: an excitation and impedance matching circuit, comprising an impedance matching network and an excitation coil; a microsecond level short-time pulse driving signal generated by a signal generator is sent to the excitation coil through the impedance matching network; the impedance matching network can adjust the impedance of the excitation coil; an energy conversion circuit, comprising an energy conversion coil connected in series through a wire and a quartz crystal oscillator with electrodes attached to the surface; the energy conversion coil and the excitation coil form a wireless inductive coupling; the short-time pulse excitation signal is transmitted to the energy conversion coil through the excitation coil, and the induced voltage formed by the energy conversion coil is directly added to the quartz crystal oscillator, and the quartz crystal oscillator is excited by the inverse piezoelectric effect; a signal receiving and detection processing unit, comprising a receiving coil, a filtering amplification circuit and an oscilloscope connected in sequence; a wire with an energy conversion circuit is passed through the receiving coil, and the wireless coupling between the receiving coil and the energy conversion circuit can be realized.

Description

Technical Field

[0001] The invention relates to the technical field of sound wave sensing, and in particular to a sound wave sensing system with microsecond-level short-time pulse wireless excitation. Background Art

[0002] The measurement principle of the quartz crystal microbalance (QCM) is based on the piezoelectric effect. When the electrodes of the QCM come into contact with the substance to be measured, the properties of the substance to be measured (such as mass, viscosity, density, etc.) will change the resonant frequency of the QCM. The change in the resonant frequency of the QCM is linearly related to the mass of the substance to be measured, so the change in the substance to be measured can be measured by the change in the resonant frequency.

[0003] The quartz crystal microbalance may be one of the most studied quartz resonant microbalance sensors. This type of sensor uses the mass-sensitive characteristics of the quartz crystal resonator. In 1995, GZ Sauerbrey first derived the Sauerbrey equation, using a simple formula to describe the relationship between the quartz crystal resonant frequency f and the surface mass change m, laying the theoretical foundation for the application of quartz crystal microbalance in sensor technology, making it widely used.

[0004]

[0005] where f 0 is the resonant frequency of the quartz crystal, A is the speed of mechanical wave propagation in the quartz crystal, ρ q is the density of the quartz crystal, μ q is the piezoelectric shear modulus of the quartz crystal, Δf is the change in frequency over the effective piezoelectric area of ​​the quartz crystal, and Δm is the change in the surface mass of the quartz crystal.

[0006] The quartz crystal microbalance technology converts mass changes into frequency change outputs. The detection equipment has a simple structure, the experimental process is simple to operate, the detection accuracy is high, and the detection of the dissipation coefficient D can obtain changes in the mass, shape, and viscoelasticity of the substance to be tested.

[0007] The so-called vibration excitation is the process of converting electrical energy into mechanical energy by using appropriate circuits and mechanical structures. Electromagnetic excitation uses the Lorentz force on the current conductor in the magnetic field to generate forced vibration. It works stably and reliably. It is the most commonly used excitation method in traditional resonance sensors. However, since this detection method must use the magnetic field, it is more difficult to miniaturize the sensor.

[0008] At present, there are two main excitation methods for QCM sensors: continuous excitation and pulse excitation. Among them, the pulse excitation type greatly reduces the complexity requirements of the excitation source and signal processing unit, which is conducive to the miniaturization of the entire analysis system.

[0009] The excitation duration of the existing pulse excitation QCM is generally in the millisecond level, which cannot match the special new excitation source, such as the electrostatic friction self-powered technology (Triboelectric nanogenerator, TENG). TENG uses the electrostatic friction imagination that is ubiquitous in nature to achieve energy collection. It is a new strategy to solve the current energy problem and has been used in the application of low-energy consumption sensing systems. The combination of QCM and TENG will be conducive to the realization of more energy-saving and environmentally friendly, high-sensitivity real-time on-site measurement of environmental / physiological biochemical parameters. However, the excitation pulse duration that TENG can provide is relatively short, only at the microsecond level, which cannot meet the functional requirements of the existing pulse-type QCM. To this end, the present invention breaks through the limitation of the QCM excitation duration and provides the possibility for the realization of a self-powered QCM system. Summary of the invention

[0010] The present invention mainly aims at the problem that the existing pulse excitation type QCM has a long excitation time requirement (millisecond level), and provides a QCM sensing system with microsecond level short-time pulse wireless excitation, which can meet the high sensitivity and fast measurement under the short-time excitation signal source.

[0011] A microsecond-level short-time pulse wireless excitation acoustic wave sensing system, comprising:

[0012] The excitation and impedance matching circuit includes an impedance matching network and an excitation coil; a short-time pulse driving signal of microsecond level generated by a signal generator is sent to the excitation coil through the impedance matching network; the impedance matching network can adjust the impedance of the excitation coil to achieve an optimal state of energy transmission; the short-time pulse driving signal can form an alternating electromagnetic field through the excitation coil, thereby wirelessly driving the transducer circuit;

[0013] The transducer circuit includes a transducer coil connected in series by a wire and a quartz crystal oscillator with electrodes attached to the surface; the transducer coil forms a wireless inductive coupling with the excitation coil, so that the short-time pulse drive signal is transmitted to the transducer coil through the excitation coil, and the induced voltage formed by the transducer coil is directly applied to the quartz crystal oscillator, and the quartz crystal oscillator is excited by the inverse piezoelectric effect to maximize the energy transmission efficiency;

[0014] The signal receiving and detection processing unit comprises a receiving coil, a filtering and amplifying circuit and an oscilloscope connected in sequence; a conductor of the transducer circuit is passed through the receiving coil, so that wireless coupling between the receiving coil and the transducer circuit can be realized, and while completing signal reception, the signal generator and other electromagnetic wave noise interference can be filtered out as much as possible, and the input impedance influence of the detection circuit can be reduced.

[0015] The driving signal of tens of microseconds forms an alternating magnetic field through the excitation coil, which is first converted into an alternating voltage at both ends of the transducer coil through the transducer coil, thereby forming an alternating potential difference on the surface of the quartz crystal oscillator, and exciting the quartz crystal to oscillate through the inverse piezoelectric effect; the receiving coil receives the magnetic field generated by the alternating current in the loop and measures the current signal in the transducer circuit, thereby realizing the electromagnetic excitation and detection of the QCM.

[0016] The impedance matching network can adjust the impedance of the excitation coil to match the internal impedance of the signal generator, so that the trigger system works in the maximum power output state and achieves the optimal energy transmission state. During the specific adjustment process, it can be judged whether the maximum vibration amplitude is reached based on the oscilloscope display graph, thereby achieving maximum energy utilization efficiency, improving the signal-to-noise ratio, and facilitating the analysis of the vibration signal of the transducer circuit.

[0017] The excitation coil adjusts the driving signal in the excitation and impedance matching circuit by connecting to the impedance matching network, and matches the resonant frequency of the crystal oscillator by adjusting the frequency of the excitation signal, thereby realizing the oscillation and resonance of the transducer circuit; the receiving coil receives the alternating current signal of the transducer circuit and transmits it to the signal processing unit.

[0018] The short-time pulse driving signal of the present invention can form an alternating electromagnetic field through the excitation coil, thereby wirelessly driving the transducer circuit, and suppressing the influence of the excitation and impedance matching circuit parameters through wireless excitation.

[0019] The present invention uses near-field coupling between an antenna formed by electrodes and an excitation electromagnetic field, and the crystal oscillator converts electrical energy into a tangential body wave acoustic wave signal in the crystal oscillator body, and prolongs the attenuation time of the electromagnetic signal, thereby improving the accuracy of subsequent signal analysis.

[0020] The receiving coil receives the alternating electrical signal generated by the piezoelectric effect when the crystal oscillator is in free oscillation through electromagnetic induction, and transfers it to the signal receiving and detection processing unit. This design can suppress the transmission of noise in other frequency bands, increase signal quality, and isolate the subsequent circuit from the transducer circuit to reduce the noise interference caused by the source signal.

[0021] The signal receiving and detection processing unit is used to receive the alternating electric field generated by the piezoelectric effect on the quartz crystal oscillator, and filter, amplify and sample the electrical signal; the signal processing unit performs digital sampling and data fitting analysis on the signal output by the detection circuit.

[0022] The signal generator may be a high-frequency pulse excitation generator.

[0023] In a preferred example, the short-time pulse driving signal is sinusoidal alternating electrical information, and its pulse time width is not less than 10 microseconds and less than 100 microseconds.

[0024] In a preferred embodiment, the excitation coil and the transducer coil are planar spiral structure coils. The transducer coil and the excitation coil are coupled to maximize the transmission efficiency of the excitation signal to the transducer circuit.

[0025] In a preferred example, the receiving coil is a solenoid coil with a magnetic ring.

[0026] In a preferred example, a gold electrode is attached to the center of the surface of the quartz crystal oscillator.

[0027] Further preferably, the diameter of the gold electrode is 3 mm, and the outer diameter of the electrode is led out from the microstrip electrode to the outer diameter of the quartz crystal oscillator.

[0028] In a preferred example, the input end of the filter amplifier circuit is connected to the receiving coil, and the output end is connected to the oscilloscope;

[0029] The filter amplifier circuit is a narrowband amplifier with an amplification factor of 47dB and an amplification bandwidth of 5.5-6.5MHz. It is equipped with a baseband adjustment circuit board connected to a voltage-stabilized power supply. The working voltage of the baseband adjustment circuit board is 12V. The electric signal sent from the receiving coil is filtered, and the useful crystal oscillator attenuation vibration signal is extracted to filter out noise interference.

[0030] The oscilloscope is connected to a PC, and the quartz crystal vibration waveform displayed on the oscilloscope is transmitted to the PC terminal, and is analyzed and processed by an experimental real-time data processing system based on LabVIEW to realize the calculation of characteristic parameters including frequency response and dissipation coefficient.

[0031] The system of the present invention uses microsecond pulse signal trigger detection to excite the quartz crystal signal. First, the signal generator is set to generate a sinusoidal gate trigger signal with a certain amplitude and frequency close to the resonant frequency of the quartz crystal to excite the quartz crystal. After the excitation signal is terminated, the damped oscillation response of the crystal is measured.

[0032] The substantial effect brought about by the present invention is that it provides an acoustic wave sensing system with microsecond-level short-time pulse wireless excitation. By optimizing the transducer circuit, the excitation circuit and the processing circuit, it is possible to use the acoustic wave sensing technology when the excitation duration is in the microsecond level, which helps to combine the self-powered technology with the acoustic wave sensing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the circuit structure of the acoustic wave sensing system with microsecond short-time pulse wireless excitation of the embodiment, wherein the receiving coil is used as a spiral coil and is passed through by the wire of the transducer circuit to form a coupling between the loop and the spiral coil, thereby realizing the function of the receiving coil;

[0034] Figure 2When measuring a circuit, the time domain signal output by the acoustic wave sensing system of the embodiment with microsecond short-time pulse wireless excitation, wherein the left part less than 0.1V is noise, the middle part greater than 0.75V is the output when the excitation signal exists, and the rest is the output of the system when the excitation signal is removed, and this part of the output is the signal actually used for measurement;

[0035] Figure 3 It is the frequency drift measured when the acoustic wave sensing system with microsecond level short-time pulse wireless excitation of the embodiment is unloaded. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0037] like Figure 1 As shown, the acoustic wave sensing system of microsecond short-time pulse wireless excitation of this embodiment includes an excitation and impedance matching circuit, a transducer circuit and a signal receiving and detection processing unit. The excitation and impedance matching circuit includes a signal generator, an impedance matching network and an excitation coil. The signal generator is a high-frequency pulse excitation generator. The transducer circuit includes a transducer coil connected in series by a wire and a quartz crystal oscillator with electrodes attached to the surface. The signal receiving and detection processing unit includes a receiving coil, a filter amplifier circuit, an oscilloscope and a PC connected in sequence. The input end of the filter amplifier circuit is connected to the receiving coil, and the output end is connected to the oscilloscope. The filter amplifier circuit is a narrowband amplifier with an amplification factor of 47dB and an amplification bandwidth of 5.5 to 6.5MHz. It is equipped with a baseband adjustment circuit board connected to a voltage-stabilized power supply. The operating voltage of the baseband adjustment circuit board is 12V. The electrical signal sent by the receiving coil is filtered, and the useful crystal oscillator attenuation vibration signal is extracted to filter out noise interference. The oscilloscope is connected to a PC, and the quartz crystal vibration waveform displayed on the oscilloscope is transmitted to the PC terminal, and is analyzed and processed by an experimental real-time data processing system based on LabVIEW to realize the calculation of characteristic parameters including frequency response and dissipation coefficient.

[0038] The signal generator is connected to the excitation coil through an impedance matching network. The excitation coil drives the transducer circuit through mutual coupling with the transducer coil. The receiving coil receives the current signal in the transducer circuit and then sends it to the signal processing unit. The signal processing unit includes a filtering and amplifying circuit, an oscilloscope and a PC.

[0039] The signal generator can generate a short-time pulse drive signal of microsecond level, and send the short-time pulse drive signal to the excitation coil through the impedance matching network. The short-time pulse drive signal is a sinusoidal alternating electrical information, and its pulse time width is not less than 10 microseconds and less than 100 microseconds. The impedance matching network can adjust the impedance of the excitation coil to achieve the optimal state of energy transmission. The short-time pulse drive signal can form an alternating electromagnetic field through the excitation coil, thereby wirelessly driving the transducer circuit.

[0040] The transducer coil is coupled with the excitation coil to form wireless inductive coupling, so that the short-time pulse drive signal is transmitted to the transducer coil through the excitation coil. The induced voltage formed by the transducer coil is directly added to the quartz crystal oscillator, and the inverse piezoelectric effect is used to excite the quartz crystal oscillator to maximize the energy transmission efficiency.

[0041] The receiving coil is provided with a conductor of the transducer circuit, so that wireless coupling between the receiving coil and the transducer circuit can be realized, and while completing signal reception, interference from the signal generator and other electromagnetic wave noise can be filtered out as much as possible, and the input impedance influence of the detection circuit can be reduced.

[0042] The excitation coil and the transducer coil are planar spiral coils of the same structure, the innermost coil diameter is 8-12 mm, the outermost coil diameter is 16-24 mm, the number of turns of the planar spiral coil is 10-14; the capacitance value of the planar spiral coil is 6.074 nF, and the admittance is 1.144 mS.

[0043] The receiving coil is a spiral coil with a magnetic ring, with a thickness of 6 to 8 mm, a diameter of 16 to 20 mm, 20 to 30 coil turns, and an admittance of 1.389 mS.

[0044] The quartz crystal oscillator is an AT-cut quartz bare chip with a gold electrode in the center of the surface. The base frequency is 6.0MHz, the diameter is 12-13mm, and the electrode thickness is 0.3mm. The diameter of the gold electrode in the center of the surface is 3mm, and the outer diameter of the electrode is led from the microstrip electrode to the outer diameter of the wafer. The quartz crystal oscillator vibrates and deforms under the drive of the alternating electromagnetic field.

[0045] The pulse drive signal is sent to the excitation coil by the excitation and impedance matching circuit. The drive signal forms an alternating magnetic field through the excitation coil, causing the transducer circuit to vibrate; the receiving coil receives the alternating magnetic field signal generated by the alternating current after the transducer circuit is excited, thereby realizing the microsecond pulse electromagnetic excitation and detection of the acoustic wave sensor.

[0046] The specific detection process is as follows:

[0047] Turn on the power supply, adjust the signal generator, adjust the trigger signal to a sinusoidal excitation pulse signal, adjust the length of the pulse signal to 100 cycles, and adjust the amplitude and frequency of the pulse signal.

[0048] By using an antenna tuner (impedance matching network) to match the signal frequency and the resonant frequency of the quartz crystal oscillator, the quartz crystal oscillator is stimulated to oscillate; through the display image of the oscilloscope, the electrical signal obtained by the received signal is observed, and the amplitude of the displayed attenuated oscillation signal is used to determine whether the crystal oscillator has reached the resonant state, and then the frequency of the trigger signal is adjusted. When the oscilloscope waveform display is not obvious or exceeds the waveform recording range, the amplitude of the drive excitation signal is adjusted.

[0049] The oscilloscope used in the system is produced by Tektronix, model TDS5054B, with a sampling frequency of up to 5GS / S, which can meet the sampling requirements of the quartz crystal oscillator with a resonant frequency of about 6MHz during the experiment, and supports the storage and output of waveform signals. The oscilloscope displays the transmitted electrical signals, such as Figure 2 By adjusting the oscilloscope, the attenuation oscillation process of the signal during the experiment can be better observed. At the same time, the oscilloscope is set to intercept some units of the attenuated signal, which is convenient for later analysis and processing of the waveform using a PC.

[0050] The PC terminal uses LABVIEW programming to control the coordinated work of the driving signal generator, impedance matching network, filter amplifier circuit, and oscilloscope during the entire experiment. The effective data transmitted by the oscilloscope is analyzed, and the attenuation signal is Fourier transformed to obtain the equation of the instantaneous resonant frequency attenuation curve corresponding to the peak value of the spectrum curve:

[0051]

[0052] At the same time, the dissipation factor is calculated according to the formula:

[0053]

[0054] The amplitude A and frequency response Δf (Δf = ff) during the entire experiment 0 ), dissipation factor D, through MATLAB processing, real-time plotting of the change curve, to facilitate further understanding of the experimental change process. Frequency response curve, for example Figure 3 ,The curve shows that the frequency fluctuation range is within 20Hz, which is sufficient to complete the measurement when used alone.

[0055] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A microsecond short-time pulse wireless excitation acoustic wave sensing system, characterized in that: include: An excitation and impedance matching circuit, including an impedance matching network and an excitation coil; A short-time pulse driving signal of microsecond level generated by a signal generator is sent to the excitation coil through the impedance matching network. The signal generator is a high-frequency pulse excitation generator. The short-time pulse driving signal is a sinusoidal alternating electrical information, and its pulse time width is not less than 10 microseconds and less than 100 microseconds. The impedance matching network can adjust the impedance of the excitation coil to achieve the optimal state of energy transmission. The short-time pulse driving signal can form an alternating electromagnetic field through the excitation coil, thereby wirelessly driving the transducer circuit. The transducer circuit comprises a transducer coil connected in series by a wire and a quartz crystal oscillator with electrodes attached to the surface; a gold electrode is attached to the center of the surface of the quartz crystal oscillator, the diameter of the gold electrode is 3 mm, and the outer diameter of the electrode is led out from the microstrip electrode to the outer diameter of the quartz crystal oscillator; the transducer coil forms a wireless inductive coupling with the excitation coil, so that the short-time pulse drive signal is transmitted to the transducer coil through the excitation coil, and the induced voltage formed by the transducer coil is directly applied to the quartz crystal oscillator, and the quartz crystal oscillator is excited by the inverse piezoelectric effect to maximize the energy transmission efficiency; The signal receiving and detection processing unit comprises a receiving coil, a filtering and amplifying circuit and an oscilloscope connected in sequence; a conductor of the transducer circuit is passed through the receiving coil, so that wireless coupling between the receiving coil and the transducer circuit can be realized, and while completing signal reception, the signal generator and other electromagnetic wave noise interference can be filtered out as much as possible, and the input impedance influence of the detection circuit can be reduced.

2. The microsecond level short-time pulse wireless excitation acoustic wave sensing system according to claim 1 is characterized in that: The excitation coil and the transducer coil are planar spiral structure coils.

3. The microsecond level short-time pulse wireless excitation acoustic wave sensing system according to claim 1 is characterized in that: The receiving coil is a solenoid coil with a magnetic ring.

4. The microsecond level short-time pulse wireless excitation acoustic wave sensing system according to claim 1 is characterized in that: The input end of the filter amplifier circuit is connected to the receiving coil, and the output end is connected to the oscilloscope; The filter amplifier circuit is a narrowband amplifier with an amplification factor of 47dB and an amplification bandwidth of 5.5-6.5MHz. It is equipped with a baseband adjustment circuit board connected to a voltage-stabilized power supply. The working voltage of the baseband adjustment circuit board is 12V. The electric signal sent from the receiving coil is filtered, and the useful crystal oscillator attenuation vibration signal is extracted to filter out noise interference. The oscilloscope is connected to a PC, and the quartz crystal vibration waveform displayed on the oscilloscope is transmitted to the PC terminal, and is analyzed and processed by an experimental real-time data processing system based on LabVIEW to realize the calculation of characteristic parameters including frequency response and dissipation coefficient.

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