Quartz crystal microbalance resonant frequency detection system, control method and terminal

Abstract

The invention provides a quartz crystal microbalance resonant frequency detection system, a control method and a terminal, a direct digital frequency synthesis excitation unit is adopted to generate a frequency sweep excitation signal with a preset frequency range and stepping, and the frequency sweep excitation signal is conditioned by a signal injection and conditioning unit and then injected into a QCM sensor. And then the pure amplitude response detection unit measures and quantifies voltage response amplitudes of the QCM sensor under different excitation frequencies, and the resonant frequency intelligent determination unit determines the resonant frequency of the QCM sensor according to the voltage response amplitudes. According to the invention, a QCM self-oscillation circuit does not need to be designed and debugged, a precise phase detection assembly does not need to be configured, the circuit board layout is simpler, and components are greatly reduced. The QCM resonant frequency can be accurately measured only through efficient amplitude detection, a complex algorithm is avoided, the operational capability requirement and the software development difficulty are reduced, the QCM resonant frequency measuring device has the advantages of being simple in structure, low in cost, easy to integrate and the like, miniaturization and low-power-consumption design can be easily achieved, and the QCM resonant frequency measuring device is suitable for portable and wearable application.

Description

Technical Field

[0001] The present invention relates to the technical field of quartz crystal microbalance, and in particular to a quartz crystal microbalance resonant frequency detection system, a control method and a terminal. Background Art

[0002] Quartz crystal microbalances (QCMs), as a highly sensitive mass sensing technology, have been widely used in fields such as chemistry, biology, and environmental monitoring. Existing QCM detection systems typically require the design and debugging of a QCM self-oscillation circuit to achieve self-oscillation. However, the design of an external oscillation circuit is not only complex but also lacks stability. Furthermore, to achieve accurate phase detection, precise phase detection components such as a phase comparator, phase detector, phase-locked loop, or I / Q demodulator are also required. These additional components significantly complicate the printed circuit board (PCB) layout and increase the number of components, leading to a bulky and complex system structure, significantly increasing cost and power consumption. Furthermore, the need to simultaneously measure phase information necessitates the design of complex algorithms such as phase data processing, phase unwrapping, and combined amplitude and phase judgment. This not only places high demands on the computing power of the microcontroller (MCU) or digital signal processor (DSP) but also significantly increases the complexity of software development. These drawbacks severely limit the system's applicability in today's increasingly miniaturized and intelligent applications. In actual application, these defects not only greatly limit the application scenarios and scope of use of the system, but also significantly increase the maintenance cost and difficulty of use of the system, bringing many inconveniences to users. Summary of the Invention

[0003] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a quartz crystal microbalance resonant frequency detection system, control method and terminal, which are used to solve the technical problems of the prior art such as complex circuits, high cost and power consumption due to the design of external oscillation circuits and precision components, complex phase data processing algorithms, high requirements for computing power and software development, difficulty in meeting small-scale intelligent needs, limited application scenarios, and increased maintenance and use costs.

[0004] To achieve the above-mentioned and other related objectives, the present invention provides a quartz crystal microbalance resonant frequency detection system, comprising: a direct digital frequency synthesis excitation unit, configured to generate a swept frequency excitation signal with a preset frequency range and step; a signal injection and conditioning unit, connected to the direct digital frequency synthesis excitation unit, configured to condition the swept frequency excitation signal generated by the direct digital frequency synthesis excitation unit and then inject it into a QCM sensor; a pure amplitude response detection unit, configured to measure and quantify the voltage response amplitude of the QCM sensor at different excitation frequencies; and a resonant frequency intelligent determination unit, connected to the pure amplitude response detection unit, configured to determine the resonant frequency of the QCM sensor based on the measured voltage response amplitudes of the QCM sensor at different excitation frequencies.

[0005] In one embodiment of the present invention, the direct digital frequency synthesis excitation unit adopts a direct digital frequency synthesizer, which is used to generate a swept frequency excitation signal that scans at a preset step within a preset frequency range under the control of a control device; wherein the preset frequency range covers the expected resonant frequency of the QCM sensor.

[0006] In one embodiment of the present invention, the signal injection and conditioning unit is used to filter and perform impedance matching processing on the swept frequency excitation signal output by the direct digital frequency synthesis excitation unit, and then directly inject the signal into the QCM sensor.

[0007] In one embodiment of the present invention, the signal injection and conditioning unit is configured to filter and impedance-match the swept frequency excitation signal through an LC filter network and then input the signal to the QCM sensor.

[0008] In one embodiment of the present invention, the pure amplitude response detection unit uses a radio frequency detector to measure and quantify the voltage response amplitude of the QCM sensor at different excitation frequencies in real time based on the input voltage signal across the QCM sensor.

[0009] In one embodiment of the present invention, the pure amplitude response detection unit uses a logarithmic detector to detect the amplitude of the voltage signal across the input QCM sensor and output a DC voltage signal that is linearly related to the logarithmic amplitude ratio of the signals across the QCM sensor, thereby quantifying the voltage amplitude response of the QCM sensor at the current excitation frequency.

[0010] In one embodiment of the present invention, the resonant frequency intelligent determination unit is configured to construct an amplitude-frequency characteristic curve based on the measured voltage response amplitude of the QCM sensor at different excitation frequencies, and determine the resonant frequency of the QCM sensor based on the amplitude-frequency characteristic curve.

[0011] In one embodiment of the present invention, determining the resonant frequency of the QCM sensor based on the amplitude-frequency characteristic curve includes: identifying, from the amplitude-frequency characteristic curve, an excitation frequency corresponding to a point where the voltage response amplitude reaches an extreme value, and determining the excitation frequency as the resonant frequency of the QCM sensor.

[0012] To achieve the above-mentioned and other related objectives, the present invention provides a quartz crystal microbalance resonant frequency detection and control method, which is applied to the quartz crystal microbalance resonant frequency detection system, and includes: a direct digital frequency synthesis excitation unit, a signal injection and conditioning unit, and a pure amplitude response detection unit. The method includes: controlling the direct digital frequency synthesis excitation unit to generate a swept frequency excitation signal with a preset frequency range and step, so that the signal injection and conditioning unit can condition the swept frequency excitation signal and then inject it into a QCM sensor; and determining the resonant frequency of the QCM sensor based on the voltage response amplitude of the QCM sensor at different excitation frequencies measured and quantified by the pure amplitude response detection unit.

[0013] To achieve the above-mentioned and other related objectives, the present invention provides an electronic terminal comprising: one or more memories and one or more processors; the one or more memories being used to store computer programs; and the one or more processors being connected to the memories and being used to run the computer programs to execute the quartz crystal microbalance resonant frequency detection system.

[0014] As described above, the present invention provides a quartz crystal microbalance resonant frequency detection system, control method, and terminal, which have the following beneficial effects: A direct digital frequency synthesis excitation unit is used to generate a swept frequency excitation signal with a preset frequency range and step, which is then conditioned by a signal injection and conditioning unit and injected into a QCM sensor. A pure amplitude response detection unit then measures and quantifies the voltage response amplitude of the QCM sensor at different excitation frequencies, and an intelligent resonant frequency determination unit determines the resonant frequency of the QCM sensor from the voltage response amplitude. The present invention eliminates the need to design and debug a QCM self-oscillation circuit or configure a precision phase detection component, simplifying circuit board layout and significantly reducing component count. Furthermore, the QCM resonant frequency can be accurately measured solely through efficient amplitude detection, avoiding complex algorithms, reducing computing power requirements, and lowering software development complexity. The system has the advantages of simple structure, low cost, and ease of integration, making it easy to implement miniaturization and low-power designs, making it suitable for portable and wearable applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Shown is a structural schematic diagram of a quartz crystal microbalance resonant frequency detection system in one embodiment of the present invention.

[0016] Figure 2 Shown is a structural schematic diagram of a quartz crystal microbalance resonant frequency detection system in one embodiment of the present invention.

[0017] Figure 3 Shown is a flow chart of a method for detecting and controlling the resonant frequency of a quartz crystal microbalance in one embodiment of the present invention.

[0018] Figure 4 Shown is a schematic structural diagram of an electronic terminal in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. The details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other unless they conflict.

[0020] It should be noted that in the following description, reference is made to the accompanying drawings, which describe several embodiments of the present invention. It should be understood that other embodiments may be used and that mechanical, structural, electrical and operational changes may be made without departing from the spirit and scope of the present invention. The following detailed description should not be considered restrictive, and the scope of the embodiments of the present invention is limited only by the claims of the published patents. The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. Spatially related terms, such as "upper", "lower", "left", "right", "below", "below", "lower", "above", "upper", etc., may be used in the text to facilitate the description of the relationship between one element or feature shown in the figure and another element or feature.

[0021] Throughout this specification, when a part is said to be "connected" to another part, this includes not only "direct connection" but also "indirect connection" with other elements interposed therebetween. Furthermore, when a part is said to "include" a certain component, unless otherwise stated, this does not exclude the other component but rather implies that the other component may be included.

[0022] The terms "first," "second," and "third" are used to describe various parts, components, regions, layers, and / or segments, but are not intended to be limiting. These terms are used solely to distinguish one part, component, region, layer, or segment from another. Therefore, a reference to a first part, component, region, layer, or segment below may also refer to a second part, component, region, layer, or segment without departing from the scope of the present invention.

[0023] Furthermore, as used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms "comprise", "include" indicate the presence of the described features, operations, elements, components, items, kinds, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, operations, elements, components, items, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Thus, "A, B, or C" or "A, B, and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B, and C". Exceptions to this definition occur only when the combination of elements, functions, or operations is inherently mutually exclusive in some way.

[0024] The present invention provides a quartz crystal microbalance resonant frequency detection system, which uses a direct digital frequency synthesis excitation unit to generate a swept frequency excitation signal with a preset frequency range and step, and injects it into a QCM sensor after conditioning by a signal injection and conditioning unit. Subsequently, a pure amplitude response detection unit measures and quantifies the voltage response amplitude of the QCM sensor at different excitation frequencies, and a resonant frequency intelligent determination unit determines the resonant frequency of the QCM sensor from the voltage response amplitude. The present invention does not require the design and debugging of a QCM self-excited oscillation circuit, nor does it require the configuration of a precise phase detection component, making the circuit board layout simpler and significantly reducing the number of components. Furthermore, the QCM resonant frequency can be accurately measured solely by efficient amplitude detection, avoiding complex algorithms, reducing computing power requirements and software development difficulty, and has the advantages of simple structure, low cost, and easy integration. It is easy to achieve miniaturization and low power consumption design, and is suitable for portable and wearable applications.

[0025] The following is a detailed description of the embodiments of the present invention with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. The present invention can be embodied in many different forms and is not limited to the embodiments described herein.

[0026] like Figure 1 A schematic structural diagram of a quartz crystal microbalance resonant frequency detection system in an embodiment of the present invention is shown.

[0027] The system comprises:

[0028] The direct digital frequency synthesis excitation unit 1 utilizes a DDS chip, controlled by a control device to generate a swept-frequency excitation signal with a preset frequency range and step size as required. This unit can sequentially change the frequency of the output signal according to the set frequency range and step size to generate a high-resolution, high-stability swept-frequency signal, thus achieving swept-frequency excitation for the QCM sensor. The DDS is capable of performing frequency synthesis with extremely small frequency step sizes, accurately scanning near the resonant frequency of the QCM, thereby more accurately locating the resonant frequency. This unit replaces traditional solutions that rely on the QCM itself to form an oscillation circuit (such as Pierce oscillators and Colpitts oscillators), avoiding the design complexity and instability of external oscillation circuits.

[0029] The signal injection and conditioning unit 2 is connected to the direct digital frequency synthesis excitation unit 1 and is used to condition the swept frequency excitation signal generated by the direct digital frequency synthesis excitation unit 1 and then inject it into the QCM sensor; through conditioning means such as filtering, possible noise and interference components are removed, making the signal injected into the QCM sensor purer, thereby improving the signal-to-noise ratio of the measurement.

[0030] The pure amplitude response detection unit 3 measures and quantifies the voltage response amplitude of the QCM sensor at different excitation frequencies. This solution relies solely on detecting the voltage signal amplitude across the QCM sensor, eliminating the need for simultaneous phase measurement. This avoids the use of complex phase detection circuits (such as phase-locked loops, vector network analyzers, or I / Q demodulators), significantly simplifying circuit design and signal processing. By eliminating the complex phase detection step, the system's hardware cost and implementation difficulty are reduced, while also reducing system power consumption.

[0031] Intelligent resonant frequency determination unit 4, connected to the pure amplitude response detection unit 3, is used to determine the resonant frequency of the QCM sensor based on the measured voltage response amplitude of the QCM sensor at different excitation frequencies. This solution determines the resonant frequency of the QCM sensor based solely on amplitude data, avoiding complex phase data processing, phase unwrapping, and combined amplitude and phase criteria, significantly reducing computing power requirements and software development difficulty.

[0032] In one embodiment, the direct digital frequency synthesis excitation unit 1 uses a direct digital frequency synthesizer (DDS), and under the control of a control device, the scanning excitation signal output by it is scanned at a preset step within a preset frequency range. The preset frequency range refers to the frequency interval covered by the direct digital frequency synthesis excitation unit 1 when performing a frequency scan. This frequency interval is set based on the expected resonant frequency of the QCM sensor and needs to cover the expected resonant frequency of the QCM sensor. The preset step refers to the incremental value of each frequency change during the frequency scan. The setting of the step value needs to be determined based on the measurement accuracy requirements and actual application needs. The size of the step value directly affects the accuracy and speed of the frequency scan. A smaller step value can improve the accuracy of the scan and more accurately locate the resonant frequency, but it will increase the scan time; a larger step value can speed up the scan, but may miss some detailed information.

[0033] The sweeping excitation signal is the signal output by the DDS excitation unit 1 that drives the QCM sensor. During the frequency sweep, the frequency of the sweeping excitation signal varies according to a preset frequency range and step size. By varying the sweeping excitation signal frequency, the QCM sensor's response at different frequencies can be stimulated, thereby finding its resonant frequency.

[0034] In one embodiment, the control device uses a microcontroller (MCU) or a digital signal processor (DSP) to send a series of frequency control words to the direct digital frequency synthesis excitation unit 1, thereby accurately directing the direct digital frequency synthesis excitation unit 1 to perform frequency sweeps within a preset frequency range and at preset step values. This process ensures that the sweeping excitation signal can systematically cover the resonant frequency range of the QCM sensor, providing a basis for accurately detecting its resonant characteristics. In this way, the control device can flexibly adjust the sweep parameters to adapt to different measurement requirements and application scenarios, thereby improving the adaptability and measurement accuracy of the entire measurement system. The control device not only controls the frequency of the sweeping excitation signal output by the direct digital frequency synthesis excitation unit 1, but also controls its phase and waveform. Although the present invention focuses primarily on frequency sweeping, this versatility of the control device provides additional flexibility and accuracy to the system. At the same time, the microcontroller can also control the output waveform, typically a sine wave, to ensure the purity and consistency of the excitation signal, which is crucial for accurate measurement of the QCM sensor.

[0035] In one embodiment, although the direct digital frequency synthesis excitation unit 1 can generate a high-precision frequency signal, its actual output may contain some spurious signals and harmonic components. These spurious signals and harmonics may interfere with the normal operation of the QCM sensor, affecting measurement accuracy and sensitivity. Filtering can remove these unnecessary frequency components, improving signal purity. Therefore, the signal injection and conditioning unit 2 needs to perform necessary filtering on the swept frequency excitation signal output by the direct digital frequency synthesis excitation unit. Furthermore, the output impedance of the direct digital frequency synthesis excitation unit 1 and the input impedance of the QCM sensor may not match, which can cause signal reflections during transmission and reduce signal transmission efficiency. Therefore, impedance matching of the swept frequency excitation signal is also required. Therefore, after filtering and impedance matching the swept frequency excitation signal output by the direct digital frequency synthesis excitation unit, the signal injection and conditioning unit 2 injects it into the two ends of the QCM sensor in the form of a small AC voltage or current to actively detect the frequency response of the QCM sensor.

[0036] In one embodiment, the signal injection and conditioning unit 2 is configured to filter and impedance-match the swept frequency excitation signal through an LC filter network before inputting it into the QCM sensor. The LC filter network is a filtering circuit composed of an inductor (L) and a capacitor (C) that effectively removes high-frequency spurious signals and harmonics. The LC filter has excellent frequency selectivity, accurately selecting the desired frequency range while suppressing signals at other frequencies. The LC filter removes spurious signals and harmonics from the output of the direct digital frequency synthesis excitation unit 1, ensuring a pure signal injected into the QCM sensor. This is crucial for improving the measurement accuracy and sensitivity of the QCM sensor. The LC filter network not only filters but also achieves impedance matching through appropriate design. By selecting appropriate inductor and capacitor values, the filter's input and output impedances can be adjusted to match the output impedance of the direct digital frequency synthesis excitation unit and the input impedance of the QCM sensor. This ensures that the swept frequency excitation signal is efficiently transmitted to the QCM sensor, reducing signal reflections and losses. Impedance matching improves signal transmission efficiency and ensures that the QCM sensor receives sufficient excitation signals.

[0037] In one embodiment, the signal injection and conditioning unit 2 applies a filtered and impedance-matched swept frequency excitation signal to the QCM sensor. The QCM sensor's response signal changes with the excitation frequency. When the excitation frequency sweeps across the QCM's resonance point, the QCM's impedance characteristics change significantly, resulting in a measurable change in the amplitude of the QCM sensor's response signal (relative to the swept frequency excitation signal). When the frequency of the swept frequency excitation signal approaches the QCM sensor's resonant frequency, the QCM sensor produces a significant resonant response, with the voltage signal amplitude across it peaking. This amplitude change can be monitored in real time by the signal injection and conditioning unit 3.

[0038] The pure amplitude response detection unit 3 is used to measure and quantify the voltage response amplitude of the QCM sensor at different excitation frequencies in real time based on the input voltage signal across the QCM sensor. This unit relies solely on detecting the amplitude of the voltage signal across the QCM (or the current signal through the QCM) to determine the resonant state. This approach eliminates traditional phase detection methods (such as phase-locked loops, vector network analyzers, or I / Q demodulators), simplifying the detection circuitry and subsequent signal processing.

[0039] The pure amplitude response detection unit 3 uses a radio frequency detector. Through operations such as rectification and filtering, it converts the high-frequency voltage signal across the QCM sensor into a quantifiable DC voltage signal, thereby detecting the signal amplitude. The high sensitivity of the radio frequency detector ensures accurate measurement of amplitude changes even at low signal levels, improving measurement accuracy and reliability. This enables real-time monitoring of the QCM sensor's response signal amplitude, recording amplitude changes as the frequency of the swept excitation signal changes.

[0040] In one embodiment, the pure amplitude response detection unit 3 employs a logarithmic detector. When the QCM sensor resonates, its impedance is minimum (series resonance) or maximum (parallel resonance), and the output will accordingly exhibit a peak or valley. The logarithmic detector outputs a DC voltage signal whose voltage value is linearly related to the logarithmic amplitude ratio between the excitation signal and the response signal of the QCM sensor. The DC voltage output by the logarithmic detector reflects the amplitude response of the QCM's transmission characteristics or impedance characteristics at a specific excitation frequency. By detecting changes in this DC voltage, the amplitude response of the QCM sensor at different current excitation frequencies can be obtained, thereby measuring the resonant frequency of the QCM sensor. The logarithmic amplitude ratio refers to the logarithmic ratio of the QCM sensor's response signal amplitude to the excitation signal amplitude. By measuring this logarithmic ratio, the logarithmic detector converts nonlinear amplitude changes into a linear voltage output.

[0041] In one embodiment, the voltage response amplitude of the QCM sensor at the corresponding excitation frequency can be obtained based on the DC voltage signal output by the pure amplitude response detection unit 3. The resonant frequency intelligent determination unit 4 records the voltage response amplitude at each excitation frequency as a data point and plots these data points into an amplitude-frequency characteristic curve based on the corresponding relationship between the excitation frequency and the voltage response amplitude.

[0042] In a preferred embodiment, determining the resonant frequency of the QCM sensor based on the amplitude-frequency characteristic curve includes: identifying the excitation frequency corresponding to the extreme point of the voltage response amplitude in the amplitude-frequency characteristic curve, and determining the excitation frequency as the resonant frequency of the QCM sensor; specifically, traversing the data points on the amplitude-frequency characteristic curve, comparing the amplitudes of adjacent points, and finding the local maximum (peak) or local minimum (valley). Once the extreme point is found, the excitation frequency corresponding to the extreme point is recorded, and this frequency is the resonant frequency of the QCM sensor. Whether the extreme point is a peak or a valley depends on the QCM equivalent circuit model, the detection configuration, the resonant mode of the QCM, and the measurement configuration of the pure amplitude response detection unit.

[0043] In one embodiment, the control device and the resonant frequency intelligent determination unit 4 can be implemented by two independent devices or by the same device, for example, by a microcontroller (MCU) or a digital signal processor (DSP).

[0044] In order to better describe the above-mentioned quartz crystal microbalance resonant frequency detection system, it is now described in conjunction with the following specific embodiments.

[0045] Example 1: A quartz crystal microbalance resonant frequency detection system. Figure 2 Schematic diagram of the structure of the quartz crystal microbalance resonant frequency detection system described in this embodiment.

[0046] The system includes a microcontroller unit U1, a direct digital frequency synthesizer U2 and a logarithmic detector U3.

[0047] Among them, the microcontroller unit U1 is the core controller of the entire system. In practical applications, a microcontroller with integrated SPI (serial peripheral interface) and ADC (analog-to-digital converter) functions can be selected. This unit undertakes several key tasks: Excitation signal control: Programming the direct digital frequency synthesizer U2 through the SPI interface, precisely controlling the frequency, phase, and waveform of its output excitation signal to meet the needs of different detection scenarios. Amplitude signal acquisition: The amplitude signal VMAG output by the logarithmic detector is acquired using the ADC channel to provide data support for subsequent frequency analysis. Resonant frequency determination: Executing the frequency scanning algorithm, based on the acquired amplitude signal, accurately determines the resonant frequency of the QCM sensor. Host computer communication: Establishing a communication connection with the host computer through the USART interface enables parameter setting, data display, and system debugging, making it convenient for users to monitor and operate the system.

[0048] The direct digital frequency synthesizer (DDS) U2 can utilize the AD9834 chip. The AD9834 is a low-power, programmable waveform generator capable of producing high-precision sine, triangle, or square wave outputs. In this system, it is used to generate a swept sinusoidal excitation signal. DDS U2 uses an external high-frequency crystal oscillator as the master clock signal, ensuring the accuracy and stability of frequency synthesis. DDS U2 receives the frequency control word and control register data written by the microcontroller unit (U1) to precisely set the output frequency. DDS U2's differential current outputs, IOUT and IOUTB, require conditioning via external resistors and a subsequent LC filter network. This LC filter network effectively filters out high-frequency spurious signals from the DDS output and DAC images, ultimately producing a relatively clean single-ended sinusoidal excitation signal, labeled INPA. This INPA signal is applied to one end of the QCM sensor. The output signal at the other end of the QCM sensor is labeled INPB. As the excitation frequency sweeps across the resonant point of the QCM sensor, its impedance characteristics change significantly. This change will cause a measurable change in the amplitude of the INPB signal (relative to INPA), providing a basis for subsequent logarithmic detector detection and analysis.

[0049] Logarithmic detector U3 uses the AD8302 chip. The AD8302 is a logarithmic amplifier and phase detector designed for RF / IF applications. In this system, its logarithmic amplitude detection function is primarily utilized. The two inputs of logarithmic detector U3 are connected to the two-terminal signals INPA and INPB of the QCM sensor via AC coupling capacitors. Matching resistors to AGND are typically configured at the inputs to provide appropriate input impedance and ensure accurate signal input. Logarithmic detector U3 outputs a DC voltage that is linearly related to the logarithmic amplitude ratio of the input signals INPA and INPB. In certain configurations, it can also measure the absolute power of a single input. In this application scenario, this output voltage reflects the amplitude response of the QCM's transmission characteristics or impedance characteristics at a specific excitation frequency. When a QCM resonates, its impedance characteristics change, reaching a minimum at series resonance and a maximum at parallel resonance. This impedance change causes a corresponding peak or valley in U3's output. By detecting these peaks or valleys, the QCM's resonant frequency can be determined.

[0050] The quartz crystal microbalance resonant frequency detection process includes:

[0051] 1. After powering on the microcontroller unit U1, quickly start the initialization routine. Set the communication parameters for the SPI interface to ensure accurate communication with the direct digital frequency synthesizer U2. Initialize the ADC and configure sampling and other parameters. Configure the direct digital frequency synthesizer U2 to output a sine wave to establish a stable operating environment for subsequent testing.

[0052] 2. The microcontroller unit U1 sends a frequency control word to the direct digital frequency synthesizer U2 via the SPI interface, so that the excitation signal INPA output by the direct digital frequency synthesizer U2 is scanned at an appropriate step within the preset range that covers the expected resonant frequency of the QCM, taking into account both accuracy and efficiency without missing any resonant points.

[0053] 3. Direct digital frequency synthesizer U2 generates a sweep frequency signal, INPA, based on the control word and applies it to the QCM sensor. The sensor's impedance and other characteristics change with the excitation frequency, generating a response signal, INPB. This variation reflects the sensor's electrical characteristics at different frequencies, providing key information.

[0054] 4. Signals INPA and INPB are simultaneously input to logarithmic detector U3. Logarithmic detector U3 performs logarithmic amplitude detection and outputs a DC voltage proportional to the amplitude response (e.g., the logarithmic value of the transmission coefficient) at the current excitation frequency of the QCM for subsequent data collection and analysis.

[0055] 5. Microcontroller unit U1 uses the ADC channel to collect the amplitude signal VMAG output by logarithmic detector U3 in real time. The ADC continuously samples at a preset sampling frequency, converting the analog voltage into a digital signal. Regular calibration is performed to ensure the accuracy of the collected data, providing a basis for subsequent processing.

[0056] 6. The microcontroller unit U1 associates the collected voltage value with the excitation frequency to form an amplitude-frequency response curve, finds the extreme point (peak or valley) on the curve, and then determines the resonant frequency of the QCM.

[0057] 7. After determining the resonant frequency, microcontroller unit U1 transmits it to a PC for display or recording, allowing the user to understand the sensor status. This value can also be used for subsequent mass change calculations, aiding research in applications such as trace substance detection and thin film growth monitoring.

[0058] In this embodiment, the AD9834 is selected as the DDS excitation source. It has the significant advantages of high frequency resolution and excellent stability, and can easily and accurately control the frequency sweep process with the help of the MCU, without the need to build a complex analog oscillation circuit. At the same time, the AD8302 is used to carry out logarithmic amplitude detection, mainly relying on the amplitude information it outputs to determine the resonant frequency. This solution does not require the complex phase-locked loop (PLL) or vector network analyzer (VNA) circuits required for precise phase detection and processing in traditional solutions, greatly reducing the complexity of the system and hardware costs. Moreover, the core components (MCU, DDS, logarithmic detector) are all highly integrated chips, and only a small number of peripheral components are needed to build a complete detection system, which is conducive to miniaturization and low-power design, and is very suitable for application in portable and wearable devices. The entire detection process is uniformly controlled by the MCU, and data acquisition and processing are both digitized, providing convenient conditions for the implementation of intelligent algorithms, automatic calibration, and data management.

[0059] It should be noted that this embodiment is presented merely as an example, and the specific solution is subject to numerous modifications and variations. For example, the specific model of the microcontroller unit U1, the specific model of the DDS chip (if other suitable options exist), the specific filter parameters, and the specific configuration of the AD8302 (for example, whether to measure absolute power or ratio) can all be flexibly adjusted based on the actual application requirements. Furthermore, the specific connection method of the QCM sensor, whether series or parallel testing, will affect the shape of the VMAG response curve and requires appropriate selection based on the actual situation.

[0060] Similar in principle to the above embodiment, the present invention provides a method for detecting and controlling the resonant frequency of a quartz crystal microbalance.

[0061] The following provides specific embodiments in conjunction with the accompanying drawings:

[0062] like Figure 3 A flow chart showing a method for detecting and controlling the resonant frequency of a quartz crystal microbalance according to an embodiment of the present invention is provided. The method is applied to the quartz crystal microbalance resonant frequency detection system in the above embodiment, and includes:

[0063] Step S1: controlling the direct digital frequency synthesis excitation unit to generate a swept frequency excitation signal with a preset frequency range and step, so that the signal injection and conditioning unit can condition the swept frequency excitation signal and then inject it into the QCM sensor;

[0064] Step S2: determining the resonant frequency of the QCM sensor based on the voltage response amplitude of the QCM sensor at different excitation frequencies measured and quantified by the pure amplitude response detection unit.

[0065] Since the implementation principle of the quartz crystal microbalance resonant frequency detection and control method has been described in the above embodiments, it will not be repeated here.

[0066] The quartz crystal microbalance resonant frequency detection and control method provided in the embodiment of the present invention can be implemented on the terminal side or the server side. As for the hardware structure of the electronic terminal, please refer to Figure 4 , is an optional hardware structure diagram of the electronic terminal 1000 provided in an embodiment of the present invention. The terminal 1000 can be a mobile phone, a computer device, a tablet device, a personal digital processing device, a factory background processing device, etc. The terminal 1000 includes: at least one processor 1001, a memory 1002, at least one network interface 10010 and a user interface 1009. The various components in the device are coupled together through a bus system 1005. It can be understood that the bus system 1005 is used to realize the connection and communication between these components. In addition to the data bus, the bus system 1005 also includes a power bus, a control bus and a status signal bus. However, for the sake of clarity, Figure 4 Various buses are labeled as bus systems.

[0067] The user interface 1009 may include a display, a keyboard, a mouse, a trackball, a click gun, keys, buttons, a touch pad or a touch screen.

[0068] It will be appreciated that the memory 1002 may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM) or a programmable read-only memory (PROM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM) and synchronous static random access memory (SSRAM). The memory described in the embodiments of the present invention is intended to include, but is not limited to, these and any other suitable types of memory.

[0069] The memory 1002 in the embodiment of the present invention is used to store various categories of data to support the operation of the terminal 1000. Examples of such data include: any executable program for operating on the terminal 1000, such as an operating system 10021 and an application 10022; the operating system 10021 includes various system programs, such as a framework layer, a core library layer, a driver layer, etc., for implementing various basic services and processing hardware-based tasks. The application 10022 can include various applications, such as a media player (MediaPlayer), a browser (Browser), etc., for implementing various application services. The quartz crystal microbalance resonant frequency detection system provided in the embodiment of the present invention can be included in the application 10022.

[0070] The methods disclosed in the above embodiments of the present invention can be applied to or implemented by processor 1001. Processor 1001 may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method can be completed by hardware integrated logic circuits in processor 1001 or by software instructions. The above processor 1001 may be a general-purpose processor, a digital signal processor (DSP), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. Processor 1001 can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present invention. The general-purpose processor 1001 may be a microprocessor or any conventional processor. The steps of the accessory optimization method provided in the embodiments of the present invention can be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software module can be located in a storage medium located in a memory. The processor reads the information in the memory and, in conjunction with its hardware, completes the steps of the above method.

[0071] In an exemplary embodiment, the terminal 1000 may be used by one or more application-specific integrated circuits (ASICs), DSPs, programmable logic devices (PLDs), and complex programmable logic devices (CPLDs) to execute the aforementioned method.

[0072] Those skilled in the art will appreciate that all or part of the steps in the above-described method embodiments can be implemented using hardware associated with a computer program. The aforementioned computer program can be stored in a computer-readable storage medium. When executed, the program performs the steps in the above-described method embodiments. The aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0073] In the embodiments provided herein, the computer readable and writable storage medium may include a read-only memory, a random access memory, an EEPROM, a CD-ROM or other optical disk storage device, a magnetic disk storage device or other magnetic storage device, a flash memory, a USB flash drive, a mobile hard disk, or any other medium that can be used to store desired program code in the form of instructions or data structures and can be accessed by a computer. In addition, any connection can be appropriately referred to as a computer readable medium. For example, if the instruction is sent from a website, a server or other remote source using a coaxial cable, a fiber optic cable, a twisted pair, a digital subscriber line (DSL) or wireless technologies such as infrared, radio and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL or wireless technologies such as infrared, radio and microwaves are included in the definition of the medium. However, it should be understood that computer readable and writable storage media and data storage media do not include connections, carriers, signals or other temporary media, but are intended to be non-temporary, tangible storage media. Disk and disc, as used in this application, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers.

[0074] Compared with existing technologies, it has the following advantages:

[0075] 1. This invention eliminates the need to design and debug a QCM self-oscillator circuit, nor does it require sophisticated phase comparators, phase detectors, phase-locked loops, or I / Q demodulators. This simplifies printed circuit board (PCB) layout and significantly reduces the number of components.

[0076] 2. The determination of the resonant frequency of the present invention is based only on the search for extreme points of the amplitude data, avoiding complex phase data processing, phase unwrap, and amplitude-phase joint judgment algorithms, significantly reducing the computing power requirements and software development difficulty of the microcontroller (MCU) or digital signal processor (DSP).

[0077] 3. Compared to existing technologies, the present invention significantly reduces manufacturing and material costs by reducing the number of components and simplifying the circuit. Furthermore, fewer components and a simpler signal chain make it easier to achieve high-level integration and miniaturization of the system, making it ideal for cost- and size-sensitive applications.

[0078] 4. The simplified system architecture of the present invention means fewer potential failure points and easier debugging and maintenance. Compared with systems that rely heavily on precise phase measurement, the sensitivity to environmental interference, such as the effect of temperature drift on phase, may be reduced.

[0079] 5. Although the present invention simplifies the detection principle, by selecting a high-resolution DDS and a high-sensitivity logarithmic amplifier, the present invention can still provide resonant frequency detection accuracy and fast sweep frequency response that meet the requirements in many application scenarios.

[0080] 6. The use of fewer active devices and simpler signal processing logic in the present invention helps to achieve lower overall system power consumption, and is particularly suitable for battery-powered portable and wearable devices.

[0081] In summary, the quartz crystal microbalance resonant frequency detection system, control method, and terminal of the present invention utilize a direct digital frequency synthesis excitation unit to generate a swept frequency excitation signal with a preset frequency range and step. This signal is then conditioned by a signal injection and conditioning unit and injected into a QCM sensor. A pure amplitude response detection unit then measures and quantifies the voltage response amplitude of the QCM sensor at different excitation frequencies, and an intelligent resonant frequency determination unit determines the resonant frequency of the QCM sensor from this voltage response amplitude. The present invention eliminates the need for designing and debugging a QCM self-oscillation circuit or configuring a precision phase detection component, resulting in a simpler circuit board layout and a significant reduction in components. Furthermore, the QCM resonant frequency can be accurately measured solely through efficient amplitude detection, avoiding complex algorithms, reducing computing power requirements and software development difficulties. The system has the advantages of a simple structure, low cost, and ease of integration, making it easy to implement miniaturization and low-power designs, making it suitable for portable and wearable applications. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and possesses high industrial value.

[0082] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, any equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed herein are intended to be covered by the claims of the present invention.

Claims

1. A quartz crystal microbalance resonant frequency detection system, characterized in that: The system comprises: Direct digital frequency synthesis excitation unit, used to generate a swept frequency excitation signal with a preset frequency range and step; A signal injection and conditioning unit, connected to the direct digital frequency synthesis excitation unit, for conditioning the swept frequency excitation signal generated by the direct digital frequency synthesis excitation unit and then injecting it into the QCM sensor; Pure amplitude response detection unit, used to measure and quantify the voltage response amplitude of the QCM sensor at different excitation frequencies; The resonant frequency intelligent determination unit is connected to the pure amplitude response detection unit and is used to determine the resonant frequency of the QCM sensor according to the measured voltage response amplitude of the QCM sensor at different excitation frequencies.

2. The quartz crystal microbalance resonant frequency detection system according to claim 1, characterized in that: The direct digital frequency synthesis excitation unit adopts a direct digital frequency synthesizer, which is used to generate a swept frequency excitation signal that scans at a preset step within a preset frequency range under the control of a control device; wherein the preset frequency range covers the expected resonant frequency of the QCM sensor.

3. The quartz crystal microbalance resonant frequency detection system according to claim 1, characterized in that: The signal injection and conditioning unit is used to filter and perform impedance matching on the swept frequency excitation signal output by the direct digital frequency synthesis excitation unit, and then directly inject the signal into the QCM sensor.

4. The quartz crystal microbalance resonant frequency detection system according to claim 3, characterized in that: The signal injection and conditioning unit is used to filter and impedance match the sweep frequency excitation signal through a set LC filter network and then input the signal into the QCM sensor.

5. The quartz crystal microbalance resonant frequency detection system according to claim 1, characterized in that: The pure amplitude response detection unit adopts a radio frequency detector, which is used to measure and quantify the voltage response amplitude of the QCM sensor at different excitation frequencies in real time according to the input voltage signal across the QCM sensor.

6. The quartz crystal microbalance resonant frequency detection system according to claim 6, characterized in that: The pure amplitude response detection unit uses a logarithmic detector to detect the amplitude of the voltage signal across the input QCM sensor and output a DC voltage signal that is linearly related to the logarithmic amplitude ratio between the signals across the QCM sensor to quantify the voltage amplitude response of the QCM sensor at the current excitation frequency.

7. The quartz crystal microbalance resonant frequency detection system according to claim 1, characterized in that: The resonant frequency intelligent determination unit is used to construct an amplitude-frequency characteristic curve according to the measured voltage response amplitude of the QCM sensor at different excitation frequencies, and determine the resonant frequency of the QCM sensor based on the amplitude-frequency characteristic curve.

8. The quartz crystal microbalance resonant frequency detection system according to claim 7, characterized in that: Determining the resonant frequency of the QCM sensor based on the amplitude-frequency characteristic curve includes: identifying an excitation frequency corresponding to a point where the voltage response amplitude reaches an extreme value from the amplitude-frequency characteristic curve, and determining the excitation frequency as the resonant frequency of the QCM sensor.

9. A quartz crystal microbalance resonant frequency detection and control method, characterized in that: The method is applied to the quartz crystal microbalance resonant frequency detection system, comprising: a direct digital frequency synthesis excitation unit, a signal injection and conditioning unit, and a pure amplitude response detection unit, and includes: Controlling the direct digital frequency synthesis excitation unit to generate a swept frequency excitation signal with a preset frequency range and step, so that the signal injection and conditioning unit can condition the swept frequency excitation signal and then inject it into the QCM sensor; The resonant frequency of the QCM sensor is determined based on the voltage response amplitude of the QCM sensor at different excitation frequencies measured and quantified by the pure amplitude response detection unit.

10. An electronic terminal, characterized in that: include: one or more memories and one or more processors; The one or more memories are used to store computer programs; The one or more processors, connected to the memory, are configured to run the computer program to perform the method as claimed in claim 9.

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