A method and system for fast query of a surface acoustic wave sensor

Abstract

The application provides a surface acoustic wave sensor rapid query method and system. The method comprises: generating a query signal covering a preset query frequency band; sending the query signal to a surface acoustic wave sensor and receiving a primary echo output by the surface acoustic wave sensor after being excited by the linear frequency modulation query signal; performing time reversal processing on the primary echo to construct a secondary transmission signal; sending the secondary transmission signal to the surface acoustic wave sensor and receiving a secondary echo output by the surface acoustic wave sensor after being excited by the secondary transmission signal; and performing frequency domain processing on the secondary echo to obtain a resonance frequency estimation value of the surface acoustic wave sensor. The application effectively solves the technical problems of frequency mismatch, echo weakening and the need for multi-frequency point repeated scanning when the resonance frequency is unknown or drifts in the prior art, realizes wideband rapid query, and still maintains full-band effective coverage under the condition of uncertain resonance frequency.

Description

Technical Field

[0001] This application belongs to the field of sensor technology, and in particular relates to the field of surface acoustic wave resonant passive wireless sensor technology. Background Technology

[0002] Surface acoustic wave (SAW) resonant passive wireless sensors require no built-in battery, are heat-resistant, and can be read and written over long distances, making them well-suited for industrial monitoring and extreme environment sensing. As application scenarios expand, some measured parameters exhibit dynamic changes on the order of milliseconds or even faster, such as rapidly changing pressure, vibration response, and dynamic strain. In such scenarios, if the sensor's resonant frequency cannot be obtained promptly and stably, it becomes difficult to effectively reflect the instantaneous changes in the measured quantity. Therefore, achieving rapid and accurate frequency lookup under conditions of unknown resonant frequency shift has become a critical issue that resonant SAW sensors must address for dynamic monitoring applications.

[0003] Existing SAW resonant sensors primarily acquire resonant frequencies using a point-by-point frequency sweep method. This involves sequentially transmitting query signals at multiple center frequencies within a range of potentially varying resonant frequencies, following a preset frequency step. If the query frequency mismatches with the actual resonant frequency, the effective energy received by the sensor will significantly decrease, resulting in a weakened echo response. Only excitation components with frequencies close to the actual resonant frequency can achieve strong energy accumulation in the resonator, leading to larger echo amplitudes and longer durations. The echoes at each frequency point are then received, subjected to Fourier transforms, and peak value determination in the frequency domain. When the resonant frequency is unknown, the query frequency often results in a mismatch between the query frequency and the true resonant point, leading to weakened echo amplitudes, indistinct spectral peaks, and a large variance in frequency estimation. To reduce the estimation variance, repeated queries at multiple frequency points near the initially determined resonant frequency are typically required. Considering that each Fast Fourier Transform (FFT) takes hundreds of microseconds or more, conventional frequency sweep reading devices are unsuitable for detecting rapidly changing quantities. Summary of the Invention

[0004] This application provides a method and system for rapid frequency readout of surface acoustic wave (SAW) sensors, which solves the technical problem that existing SAW resonant sensors cannot simultaneously achieve wide-band coverage and fast, stable frequency readout in dynamic monitoring scenarios where the resonant frequency has an unknown offset.

[0005] In a first aspect, embodiments of this application provide a fast query method for a surface acoustic wave (SAW) sensor, comprising: generating a query signal covering a preset query frequency band; sending the query signal to the SAW sensor and receiving a primary echo output by the SAW sensor after being excited by the linear frequency modulated query signal; performing time-reversal processing on the primary echo to construct a secondary transmission signal; sending the secondary transmission signal to the SAW sensor and receiving a secondary echo output by the SAW sensor after being excited by the secondary transmission signal; and performing frequency domain processing on the secondary echo to obtain an estimated value of the resonant frequency of the SAW sensor.

[0006] In one implementation of the first aspect, the range of the preset query frequency band matches the resonant frequency range of the surface acoustic wave sensor, covering all possible frequency ranges after the resonant frequency of the surface acoustic wave sensor is unknown or has drifted.

[0007] In one implementation of the first aspect, the instantaneous frequency of the query signal changes continuously with time within a preset pulse width.

[0008] In one implementation of the first aspect, the query signal is a linear frequency modulation query signal.

[0009] In one implementation of the first aspect, the primary echo is output in the form of a damped oscillation after the surface acoustic wave sensor is excited; the primary echo contains frequency structure information related to the actual resonant frequency of the surface acoustic wave sensor.

[0010] In one implementation of the first aspect, the step of performing time reversal processing on the primary echo to construct a secondary transmission signal includes: truncating the primary echo within an effective time window and performing conjugate inversion processing on the truncated primary echo; and performing energy normalization processing on the signal after conjugate inversion processing to obtain the secondary transmission signal.

[0011] In one implementation of the first aspect, the conjugate inversion process involves flipping the first echo on the time axis and taking its conjugate; the energy normalization process ensures that the secondary transmission signal and the first echo remain comparable in transmission energy.

[0012] In one implementation of the first aspect, the step of performing frequency domain processing on the secondary echo to obtain the resonant frequency estimate of the surface acoustic wave sensor includes: sampling the secondary echo to form a discrete time series; performing a fast Fourier transform on the discrete time series to obtain the spectral distribution of the secondary echo within a preset query bandwidth; performing a spectral peak search on the spectral distribution within the preset query bandwidth, and using the frequency corresponding to the searched spectral peak as the resonant frequency estimate of the surface acoustic wave sensor.

[0013] In one implementation of the first aspect, the spectral peak search method is FFT peak search, interpolation peak search, or local spectrum fitting search.

[0014] Secondly, embodiments of this application provide a rapid query system for a surface acoustic wave (SAW) sensor, applied to a SAW sensor, comprising: a signal processing and control module, a signal generation module, a signal receiving module, and a transceiver switching unit; the signal processing and control module is configured to send control commands to the signal generation module to generate a query signal covering a preset query frequency band; the signal generation module is configured to generate the query signal under the control of the signal processing and control module, and output the query signal to the transceiver switching unit; the transceiver switching unit is configured to radiate the query signal to the SAW sensor, receive the first echo output by the SAW sensor after being excited by the query signal, and output the first echo to the signal receiving module; the signal receiving module is configured to perform radio frequency conditioning and demodulation processing on the first echo, and transmit the processed first echo to the signal processing and control module; the signal... The signal processing and control module is further configured to perform time-reversal processing on the primary echo to construct a secondary transmission signal, and to issue a secondary transmission control command to the signal generation module to control the signal generation module to generate the secondary transmission signal; the signal generation module is further configured to generate the secondary transmission signal under the control of the signal processing and control module, and output the secondary transmission signal to the transceiver switching unit; the transceiver switching unit is further configured to radiate the secondary transmission signal to the surface acoustic wave sensor, and receive the secondary echo output by the surface acoustic wave sensor after being excited by the secondary transmission signal, and output the secondary echo to the signal receiving module; the signal receiving module is further configured to perform radio frequency conditioning and demodulation processing on the secondary echo, and transmit the processed secondary echo to the signal processing and control module; the signal processing and control module is further configured to perform frequency domain processing on the secondary echo to obtain the estimated value of the resonant frequency of the surface acoustic wave sensor.

[0015] The surface acoustic wave sensor fast query method and system provided in this application have the following beneficial effects:

[0016] 1. This application uses linear frequency modulation (LFM) signals to achieve single-shot broadband coverage query, eliminating the need for repeated transmission and detection at each frequency point within the target frequency band. It can cover the range of possible resonant frequencies within a single pulse duration, effectively solving the technical problem that existing surface acoustic wave resonant sensors cannot achieve both broadband coverage and fast, stable frequency readout in dynamic monitoring scenarios where the resonant frequency has unknown shifts. It also effectively solves the technical problems of frequency mismatch, weakened echo, and the need for repeated scanning at multiple frequency points when the resonant frequency is unknown or drifting in the prior art. It achieves broadband fast query and can still maintain effective coverage of the entire frequency band under the condition of uncertain resonant frequency, providing a stable foundation of resonant-related information for subsequent frequency readout, avoiding detection failure or unstable estimation. Within the frequency drift range of 433–435 MHz, it effectively reduces the root mean square error of frequency estimation and has good adaptability to frequency shifts.

[0017] 2. This application employs a time-reversal (TR) processing method, performing conjugate inversion and energy normalization on the first received echo before retransmission. The secondary transmitted signal is adaptively constructed by the system based on the actual echo from the first transmission. This solves the technical problems in the prior art where the effective resonant components of the echo are weak, the spectral peaks are not prominent, and the frequency estimation accuracy and stability decrease when there is low signal-to-noise ratio, frequency mismatch, or changes in coupling state. It achieves weighted enhancement of resonant-related frequency components, increases the effective response ratio and signal-to-noise ratio, and improves the frequency estimation accuracy and stability. In the signal-to-noise ratio range of 0–20 dB and the frequency drift range of 433–435 MHz, compared with the five-point frequency sweep method, the RMSE is reduced by approximately 60% and 36%, respectively, and the overall RMSE is approximately 64% of that of the five-point frequency sweep method.

[0018] 3. This application can complete the resonant frequency readout by performing only one frequency domain transformation and peak search on the secondary echo, without having to perform FFT and decision-making on multiple echoes at multiple frequency points separately. This solves the technical problems of existing point-by-point frequency scanning methods, such as high processing overhead, long measurement cycle, and difficulty in meeting the rapid readout requirements of dynamic scenarios. It significantly reduces the number of frequency domain processing operations, shortens the single measurement cycle, and improves the system update rate. Compared with the five-point frequency scanning method, it significantly shortens the query time and has engineering application feasibility in dynamic measurement scenarios.

[0019] 4. This application can be implemented through a software radio platform or dedicated hardware (such as FPGA or DSP). The frequency estimation calculation has low complexity and is easy for embedded systems to process in real time. If the FFT processing is moved to the hardware side, the measurement cycle can be further compressed to the sub-millisecond to millisecond level and the update rate can be increased to the kHz level, which is easy to promote and apply in engineering. Attached Figure Description

[0020] Figure 1 The diagram shown is an overall flowchart of a fast query method for surface acoustic wave sensors according to an embodiment of this application.

[0021] Figure 2 The flowchart shown is a process for obtaining a secondary emission signal in a fast query method for a surface acoustic wave sensor according to an embodiment of this application.

[0022] Figure 3 The graph shown is a comparison of the curves of two query signals in a fast query method for a surface acoustic wave sensor according to an embodiment of this application.

[0023] Figure 4 The flowchart shown is a process for obtaining the estimated resonant frequency of a surface acoustic wave (SAW) sensor in a fast query method according to an embodiment of this application.

[0024] Figure 5 The diagram shown illustrates the principle architecture of a fast query method for surface acoustic wave sensors according to an embodiment of this application.

[0025] Figure 6 The diagram shows an implementation process of a fast query method for surface acoustic wave sensors according to an embodiment of this application.

[0026] Figure 7 The diagram shown is a schematic diagram of the principle structure of a surface acoustic wave sensor fast query system in one embodiment of this application.

[0027] Component designation explanation

[0028] 100 Surface acoustic wave sensor rapid query system 110 Signal processing and control module 120 Signal generation module 130 Signal receiving module 140 Transceiver switching unit 150 Surface acoustic wave sensor S100~S500 step S310~S320 step S510~S530 step Detailed Implementation

[0029] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. This application can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, unless otherwise specified, the following embodiments and features in the embodiments can be combined with each other.

[0030] Before providing a detailed description of this embodiment, the nouns and terms used in this embodiment are explained, and the nouns and terms used in this embodiment are subject to the following interpretations:

[0031] SAW stands for Surface Acoustic Wave.

[0032] LFM stands for Linear Frequency Modulation.

[0033] TR stands for Time Reversal.

[0034] FFT stands for Fast Fourier Transform.

[0035] RMSE stands for Root Mean Square Error.

[0036] To address the problems of long measurement cycles, sensitivity to frequency mismatch, and poor frequency estimation stability of traditional point-by-point frequency scanning query methods for existing SAW resonant sensors when the resonant frequency has an unknown offset, this embodiment provides a fast query method based on a combination of linear frequency modulation and time inversion. The aim is to achieve a balance between wideband coverage and fast readout characteristics, meeting the requirements of dynamic monitoring scenarios for fast and stable sensor readout.

[0037] Specifically, this embodiment provides a rapid query method and system for surface acoustic wave (SAW) sensors, which is a rapid query method and implementation system for SAW resonant sensors based on a combination of linear frequency modulation and time inversion. The technical problem this embodiment aims to solve is that in wireless passive SAW resonant sensor applications, the sensor's resonant frequency shifts with changes in temperature, pressure, strain, or coupling state. Existing point-by-point frequency sweeping or single-frequency trial-and-error query methods suffer from long measurement cycles, sensitivity to frequency mismatch, and insufficient readout speed and stability in dynamic scenarios. To address this, this embodiment proposes a technical solution centered on broadband single-pass coverage, echo adaptive re-excitation, and single-pass frequency domain readout. Its key difference from existing technologies lies in that it does not employ the traditional multi-frequency point trial-and-error method to find the resonant point. Instead, it first uses a linear frequency modulated signal to cover the target frequency band once, then uses the resonance-related information retained in the first echo to construct a secondary query signal, further enhancing the resonance-related components in the secondary echo. Finally, frequency estimation is completed through only one frequency domain transformation and peak search.

[0038] The following will refer to the appendices in the embodiments of this application. Figure 1 To be continued Figure 7 This application provides a detailed description of the technical solutions for the rapid query method and system for surface acoustic wave sensors in the embodiments of this application. This allows those skilled in the art to understand and implement the rapid query method and system for surface acoustic wave sensors in this embodiment without inventive effort.

[0039] This embodiment provides a fast query method for surface acoustic wave (SAW) sensors, applicable to wireless passive SAW resonant sensors. Figure 1 The flowchart shown is a fast query method for surface acoustic wave sensors in an embodiment of this application. For example... Figure 1 As shown, the fast query method for surface acoustic wave sensors provided in this application includes the following steps S100 to S500.

[0040] Step S100: Generate a query signal covering a preset query frequency band;

[0041] Step S200: Send the query signal to the surface acoustic wave sensor and receive the first echo output by the surface acoustic wave sensor after being excited by the linear frequency modulation query signal;

[0042] Step S300: Perform time reversal processing on the primary echo to construct a secondary transmission signal;

[0043] Step S400: Send the secondary transmission signal to the surface acoustic wave sensor and receive the secondary echo output by the surface acoustic wave sensor after being excited by the secondary transmission signal.

[0044] Step S500: Perform frequency domain processing on the secondary echo to obtain the estimated resonant frequency of the surface acoustic wave sensor.

[0045] The method in this embodiment can balance query speed, estimation accuracy, and stability even when the resonant frequency has an unknown shift. First, a linear frequency-modulated query signal covering a preset query frequency band is generated. A single broadband excitation is sufficient to adapt to scenarios where the resonant frequency of the surface acoustic wave sensor is unknown or drifting, eliminating the need for point-by-point frequency sweeping. After transmitting the query signal to the sensor and receiving the first echo, time-reversal processing is performed on the first echo to construct an adaptive secondary transmission signal. This coherently enhances the resonant-related frequency components, effectively improving the echo signal-to-noise ratio and frequency component contrast. The secondary transmission signal is then transmitted to the sensor to acquire the second echo. Finally, frequency domain transformation and peak search are performed on the second echo, allowing the sensor resonant frequency estimate to be obtained with only one frequency domain processing step. The entire process eliminates the need for multiple transmissions and repetitive frequency domain calculations, achieving fast broadband querying while significantly improving frequency estimation accuracy and stability, shortening the measurement cycle, and making it more suitable for dynamic measurement scenarios.

[0046] The following combination Figures 2 to 6 The above steps S100 to S500 of the fast query method for surface acoustic wave sensors in this embodiment will be described in detail.

[0047] Step S100: Generate a query signal covering the preset query frequency band.

[0048] In this embodiment, the query signal is configured such that its instantaneous frequency continuously changes over time within a preset pulse width duration, thereby enabling complete coverage of the pre-defined query frequency band during a single signal transmission. By employing the aforementioned broadband excitation method, even when the actual resonant frequency of the surface acoustic wave sensor drifts due to environmental factors or changes in operating conditions, or when the initial value of the resonant frequency is unknown, a single query operation can still achieve overall coverage of the entire range of possible resonant frequencies of the sensor. This eliminates the need to know the precise location of the resonant point in advance, effectively avoiding the strong dependence of traditional single-frequency excitation methods on prior information about the resonant frequency, and improving the system's adaptability and detection reliability under complex operating conditions and unknown initial conditions.

[0049] In one implementation of this embodiment, the range of the preset query frequency band is matched with the resonant frequency range of the surface acoustic wave sensor. That is, the range of the preset query frequency band is set according to the nominal resonant frequency and expected drift range of the surface acoustic wave sensor, so that it matches the actual operating frequency range of the sensor. This can completely cover all possible frequency ranges after the sensor resonant frequency is unknown, temperature drift, or stress shift, ensuring effective excitation and reliable detection can be achieved throughout the entire operating range.

[0050] In one implementation of this embodiment, the instantaneous frequency of the query signal changes linearly and continuously with time within a preset pulse width to form a linear frequency modulated signal, which facilitates signal generation, transmission and subsequent echo processing.

[0051] In another implementation of this embodiment, the query signal is not limited to a linear frequency modulated signal, but can also be a broadband coded signal with broadband coverage characteristics. As long as it can cover the target query frequency band in a single transmission, it can be applied to this embodiment to meet the signal design requirements of different application scenarios.

[0052] Compared to traditional point-by-point frequency scanning or single-frequency probing methods, this step eliminates the need for repeated transmission and detection at each frequency point within the target frequency band. Wideband coverage can be achieved with a single pulse, fundamentally solving the technical problems in existing technologies where single-frequency queries are prone to frequency mismatch, weakened echo signals, and the need for repeated scanning at multiple frequency points to cover the target frequency band when the resonant frequency drifts. This enables rapid wideband querying under the condition of prior unknown resonant frequency, providing a stable foundation of resonant-related information for subsequent frequency readouts. It avoids detection failures or unstable estimations caused by deviations between the query frequency and the true resonant frequency. Within the frequency drift range of 433–435 MHz, the root mean square error (RMSE) of frequency estimation using this method can be stabilized at approximately 26 Hz, demonstrating excellent adaptability to frequency shifts.

[0053] Step S200: Send the query signal to the surface acoustic wave sensor and receive the first echo output by the surface acoustic wave sensor after being excited by the linear frequency modulation query signal.

[0054] In one implementation of this embodiment, the primary echo is output in the form of a damped oscillation after the surface acoustic wave sensor is excited; the primary echo contains frequency structure information related to the actual resonant frequency of the surface acoustic wave sensor.

[0055] In this embodiment, the generated linear frequency modulated query signal is transmitted to the transceiver antenna via a radio frequency link. The transceiver antenna then radiates this radio frequency signal as electromagnetic waves to the wireless passive surface acoustic wave (SAW) resonant sensor under test. Upon receiving the broadband excitation signal, the interdigital transducers on the piezoelectric substrate inside the wireless passive SAW resonant sensor are excited, generating a resonant response related to its own resonant characteristics. After the excitation signal ends, the sensor radiates an echo signal outward in the form of damped oscillation. This echo signal is received by the same transceiver antenna, undergoes down-conversion, filtering, and analog-to-digital conversion, and is converted into a baseband digital signal before being uploaded, thereby obtaining the echo information of the sensor in its current operating state.

[0056] Because SAW resonators have frequency selectivity, they respond more significantly to frequency components in the excitation signal that are close to their actual resonant frequency. Therefore, the received echo signal already carries characteristic structural information related to the sensor's resonant frequency, providing a data basis for subsequent signal processing and frequency estimation.

[0057] Therefore, step S200 completes the acquisition of one echo information under the actual state of the sensor. Since the SAW resonator responds more strongly to frequency components close to its actual resonant frequency, the echo naturally contains frequency structure information related to the current resonant state of the sensor, providing the original data basis for subsequent time inversion processing. Effective excitation and echo acquisition can be completed without additional prior resonant frequency information.

[0058] Step S300: Perform time reversal processing on the primary echo to construct a secondary transmission signal.

[0059] This embodiment utilizes the resonance-related information retained in the first echo to construct a second query signal (second transmission signal) that matches the current state of the surface acoustic wave sensor, instead of retransmitting a pre-designed, irrelevant excitation.

[0060] In practical applications, changes in temperature, pressure, strain, or coupling conditions can cause shifts in the sensor's resonant frequency. Therefore, although the first echo contains resonance-related information, its effective resonant component may not be prominent enough under conditions of low signal-to-noise ratio or large mismatch. To address this, this embodiment further performs time-reversal processing on the first echo.

[0061] like Figure 2 As shown, in one implementation of this embodiment, the step of performing time reversal processing on the primary echo to construct the secondary transmission signal includes the following steps S310 and S320.

[0062] Step S310: Extract an effective time window from the first echo and perform conjugate inversion processing on the extracted first echo.

[0063] In one implementation of this embodiment, the conjugate inversion process involves flipping the first echo on the time axis and taking its conjugate.

[0064] Step S320: Perform energy normalization processing on the signal after conjugate inversion processing to obtain the secondary transmission signal.

[0065] In one implementation of this embodiment, the energy normalization process ensures that the secondary transmission signal and the primary echo remain comparable in transmission energy.

[0066] In this embodiment, after receiving the down-converted first-echo baseband digital signal, a series of baseband digital processes are performed on it to construct a secondary transmission signal adapted to the current sensor state. The baseband digital processing includes effective time window truncation, conjugate inversion processing, and energy normalization processing.

[0067] Specifically, firstly, an effective time window is extracted from the echo signal. Based on the time-domain characteristics of the sensor echo and the system preset parameters, the signal period containing the effective resonant response is selected. Invalid data segments dominated by excitation tail, spatial reflection interference, and noise are removed, and only the effective signal part that can reflect the sensor's resonant characteristics is retained.

[0068] Subsequently, the windowed echo signal undergoes conjugate inversion processing, which involves reversing the order of the complex baseband echo signal along the time axis and taking the complex conjugate of the complex signal value at each moment. This ensures that the processed signal possesses time-domain structural characteristics that match the propagation channel and sensor response. Following this, the conjugate-inverted signal undergoes energy normalization processing. Amplitude scaling is used to adjust the overall energy level of the signal, ensuring that the final secondary transmission signal and the initial linear frequency modulation query signal are at a comparable level in transmission energy. This guarantees the rationality of the secondary excitation power and link compatibility, avoiding insufficient excitation or signal saturation due to energy differences.

[0069] Through the above processing procedure, such as Figure 3 As shown, the secondary transmission signal can be finally constructed. This signal is not a pre-set fixed excitation waveform, but is adaptively generated based on the resonance-related information carried in the primary echo. It can match the current resonance state of the sensor and the channel transmission characteristics, thereby achieving targeted enhancement of the sensor's resonance frequency components and laying the foundation for subsequent acquisition of the secondary echo and high-precision frequency estimation.

[0070] Step S300 uses time-reversal processing to ensure that the secondary transmitted signal is no longer a pre-designed external excitation, but is adaptively generated by the system based on the actual echo. The signal already contains the resonance-related structure information retained after the first propagation, solving the technical problems in the prior art where the effective resonance component in the echo is weak, the spectral peak is not prominent, and the frequency estimation accuracy and stability decrease when there is low signal-to-noise ratio, frequency mismatch, or changes in coupling state. The useful signal term corresponding to the actual resonance frequency of the sensor in the secondary echo is further coherently enhanced with the sensor frequency response, while the two received noises are only incoherent superpositions and do not form coherent enhancement. Therefore, the effective response ratio and signal-to-noise ratio at the resonance-related frequency are significantly improved, greatly improving the accuracy and stability of frequency estimation. In the 0-20dB signal-to-noise ratio range, the RMSE of the method in this embodiment is controlled in the order of hundreds of Hertz, which is about 60% lower than the traditional five-point frequency sweep method. In the 433-435 MHz frequency drift range, the RMSE is further reduced by about 36%. In the experiment, the overall RMSE was only 64% of that of the five-point frequency sweep method.

[0071] Step S400: Send the secondary transmission signal to the surface acoustic wave sensor and receive the secondary echo output by the surface acoustic wave sensor after being excited by the secondary transmission signal.

[0072] In this embodiment, after completing the baseband digital processing of the first echo and constructing the secondary transmission signal, a transmission control command is immediately issued to call the previously generated secondary transmission signal. This secondary transmission signal is then conditioned and amplified via the RF link before being transmitted to the transceiver antenna. Upon receiving the secondary transmission signal, the transceiver antenna converts it into RF electromagnetic waves and radiates them directionally to the passive SAW resonant sensor under test, ensuring that the secondary excitation signal effectively reaches the sensor and forms a stable excitation.

[0073] In this embodiment, after receiving the secondary transmission signal, the passive SAW resonant sensor adaptively constructs the signal based on the resonance-related information in the primary echo. Its signal structure is highly matched with the sensor's current resonance state and signal propagation channel characteristics. Therefore, the sensor is effectively excited by this targeted excitation signal, generating a secondary resonance response strongly correlated with its actual resonance frequency. After the secondary excitation signal ends, the sensor radiates a secondary echo signal outward in the form of damped oscillation. The frequency component corresponding to the sensor's actual resonance frequency in this secondary echo signal has its amplitude and distinguishability further enhanced due to the targeted enhancement effect of the secondary transmission signal, while non-resonant frequency components and noise interference are relatively suppressed.

[0074] The secondary echo signal is received through a transceiver antenna. The received secondary echo radio frequency signal is transmitted to a software radio transceiver device, which sequentially performs signal conditioning processing such as radio frequency filtering, down-conversion, and analog-to-digital conversion to convert it into a baseband digital signal that can be processed by electronic devices. The baseband digital signal is then uploaded to complete the acquisition and transmission of the secondary echo.

[0075] This embodiment utilizes the sensor resonance-related characteristic components carried in the secondary transmission signal and retained after the first propagation to achieve a secondary enhancement of the sensor's resonance response. This makes the frequency components corresponding to the actual resonant frequency of the sensor more prominent in the secondary echo, effectively improving the distinction between the resonant signal and noise or interference signals. Consequently, it provides a high-quality signal foundation for subsequent frequency domain processing, peak search, and resonant frequency estimation of the secondary echo, significantly improving the accuracy, stability, and reliability of subsequent frequency decision-making, and avoiding frequency estimation deviations or decision failures caused by weak resonant signals or significant interference.

[0076] Through step S400, since the secondary transmission signal has completed adaptive matching for the current resonance state of the sensor, the resonance-related frequency components in the secondary echo are specifically enhanced, effectively suppressing noise and non-resonant interference, providing a high-quality signal foundation for subsequent high-precision frequency estimation, further strengthening the spectral peak characteristics corresponding to the resonance frequency, and improving the reliability of frequency decision.

[0077] Step S500: Perform frequency domain processing on the secondary echo to obtain the estimated resonant frequency of the surface acoustic wave sensor.

[0078] In this embodiment, after receiving the processed secondary echo baseband digital signal, the resonant frequency of the surface acoustic wave (SAW) resonant sensor is estimated through a series of sampling and frequency domain processing operations. Specifically, this is achieved through the following sub-steps, which work together to ensure the accuracy and efficiency of frequency estimation.

[0079] like Figure 4 As shown, in one implementation of this embodiment, the step of performing frequency domain processing on the secondary echo to obtain the estimated resonant frequency of the surface acoustic wave sensor includes the following steps S510 and S530.

[0080] Step S510: Sample the secondary echo to form a discrete time series.

[0081] The secondary echo baseband digital signal is sampled according to a preset sampling frequency, converting the continuous-time domain secondary echo signal into a discrete-time sequence. The sampling frequency setting must satisfy the Nyquist sampling theorem to ensure that the resonant correlation frequency information in the secondary echo is not lost during the sampling process. Simultaneously, it balances signal processing efficiency with system resource consumption. The sampled discrete-time sequence fully preserves the resonant correlation characteristics of the secondary echo after being enhanced by linear frequency modulation (LFM) broadband coverage and time reversal (TR) retransmission, providing a high-quality discrete signal foundation for subsequent frequency domain processing.

[0082] Step S520: Perform a Fast Fourier Transform on the discrete time series to obtain the spectral distribution of the second echo within a preset query bandwidth.

[0083] The preset Fast Fourier Transform (FFT) algorithm is invoked to perform frequency domain transformation on the discrete-time sequence obtained in step S510, mapping the discrete-time domain signal to the frequency domain to obtain the spectral distribution of the secondary echo signal. This spectral distribution clearly presents the amplitude characteristics of different frequency components in the secondary echo. Among them, the frequency component corresponding to the actual resonant frequency of the SAW resonant sensor has a more prominent amplitude compared to other frequency components due to the TR retransmission enhancement processing, and the identification of the spectral peak is significantly improved. At the same time, the frequency domain transformation process is strictly limited to a preset query bandwidth, which is consistent with the query frequency band set in step S100, which can effectively eliminate noise and interference signals outside the bandwidth, further improving the effectiveness of the spectral distribution.

[0084] Step S530: Perform a spectrum peak search on the spectrum distribution within the preset query bandwidth, and use the frequency corresponding to the searched spectrum peak as the estimated value of the resonant frequency of the surface acoustic wave sensor.

[0085] In one implementation of this embodiment, the method of searching the spectral peak is, but is not limited to, FFT peak search, interpolation peak search, or local spectrum fitting search.

[0086] After obtaining the spectral distribution of the secondary echo, a spectral peak search algorithm is executed. Within a preset query bandwidth, the spectral amplitude is traversed and detected to identify the peak point with the largest amplitude in the spectrum. The frequency corresponding to this peak point is the estimated resonant frequency of the SAW resonant sensor. In one implementation of this embodiment, the spectral peak search method is, but is not limited to, FFT peak search, interpolation peak search, or local spectrum fitting search. Among these, the FFT peak search method is simple to operate and has high computational efficiency, making it suitable for scenarios with high real-time requirements. The interpolation peak search method can improve the accuracy of peak location through interpolation algorithms, making it suitable for scenarios with high frequency estimation accuracy requirements. The local spectrum fitting search method can effectively suppress the influence of noise interference on peak location by fitting the spectrum near the peak, further improving the stability of frequency estimation. Those skilled in the art can flexibly choose a suitable peak search method according to the accuracy and real-time requirements of the actual application scenario.

[0087] This embodiment transforms the resonance-related response after achieving wideband effective excitation via LFM broadband coverage and enhancing the prominent resonant frequency component via TR retransmission into a directly decisionable, accurate, and reliable resonant frequency estimation result through the coordinated processing of sampling, frequency domain transformation, and peak search. This achieves the core objective of the entire query process. Compared to traditional point-by-point frequency scanning techniques, this embodiment eliminates the need for multiple echo acquisitions, frequency domain transformations, and frequency domain comparisons for multiple discrete query frequency points. Only one complete LFM+TR query process is required, through the aforementioned single sampling, single fast Fourier transform, and single peak search frequency domain analysis operations, to complete the readout of the SAW resonant sensor's resonant frequency. This significantly reduces the number of signal processing steps and system overhead, shortens the single measurement cycle, and ensures the accuracy and reliability of frequency estimation. It effectively solves the technical problems of low measurement efficiency, high processing complexity, and difficulty in meeting the rapid readout requirements of dynamic scenarios inherent in traditional point-by-point frequency scanning methods.

[0088] like Figure 5 The diagram shown is a schematic representation of the principle of the wireless passive surface acoustic wave (SAW) resonant sensor resonant frequency lookup method described in this embodiment. Figure 5 As shown, the system architecture of this embodiment can be simplified into two parts: a fixed end and a measured location. The fixed end includes a reading device (baseband digital processing equipment (computer / host computer), software radio transceiver) and a transceiver antenna. The reading device is used to generate excitation signals, receive echo signals, and perform signal processing. The measured location includes a SAW resonant sensor and a matching transceiver antenna, which is used to receive excitation signals and feed back resonant echoes.

[0089] The workflow of this embodiment is as follows:

[0090] 1) Transmitting a linear frequency modulation (LFM) excitation signal: The fixed-end reading device generates a linear frequency modulation (LFM) query signal. Within a preset transmission duration T, the instantaneous frequency of this signal changes linearly and continuously from the starting frequency f1 to the ending frequency f2. A single transmission can completely cover the preset query frequency band f1~f2. The LFM query signal is radiated to the SAW resonant sensor at the measured location via the fixed-end transceiver antenna, achieving one-time broadband coverage of the sensor's possible resonant frequency range. This eliminates the need for point-by-point frequency scanning and can adapt to application scenarios where the resonant frequency is unknown or drifting.

[0091] 2) Obtaining a primary echo: The SAW resonant sensor generates a resonant response under the action of the linear frequency modulation excitation signal. After the excitation ends, it outputs a primary echo in the form of damped oscillation. The primary echo is radiated by the transceiver antenna at the measured position and then received by the fixed-end transceiver antenna and sent to the reading device. The primary echo carries characteristic information related to the actual resonant frequency of the sensor, providing a data basis for subsequent signal processing.

[0092] 3) Constructing a secondary transmission signal: The fixed-end reading device performs baseband digital processing on the primary echo. The baseband digital processing includes at least effective time window truncation, conjugate inversion processing, and energy normalization processing, thereby constructing a secondary transmission signal. The secondary transmission signal is adaptively generated based on the resonance-related information in the primary echo, and matches the current resonance state of the sensor and the channel transmission characteristics, thereby achieving targeted enhancement of the resonance frequency components.

[0093] 4) Obtaining the secondary echo and resonant frequency estimate: The fixed end retransmits the secondary transmission signal to the SAW resonant sensor. Under the action of the adaptive excitation signal, the sensor generates a secondary echo and feeds it back to the fixed end. The component in the secondary echo corresponding to the actual resonant frequency of the sensor is coherently enhanced by the two excitations, and the amplitude and recognition are significantly improved. The fixed end performs sampling, fast Fourier transform and spectral peak search on the secondary echo to obtain the resonant frequency estimate of the SAW resonant sensor and complete the resonant frequency readout.

[0094] like Figure 6 The diagram shown is a system flowchart of the wireless passive SAW resonant sensor resonant frequency query method described in this embodiment. The diagram illustrates the complete signal flow and processing from initial excitation signal generation to final frequency estimation, as detailed below:

[0095] The query process in this embodiment is mainly divided into six stages: initial signal transmission, first echo reception, time reversal processing, second signal transmission, second echo reception, and frequency estimation. The signal interaction and processing logic of each stage is as follows:

[0096] First, the initial linear frequency modulation (LFM) signal transmission phase is performed: a software radio is used as the signal transmission source to generate and transmit a linear frequency modulation (LFM) query signal. The LFM query signal is used to cover a preset query frequency band and provide an initial broadband signal source for the resonant excitation of subsequent sensors.

[0097] Subsequently, the first echo reception stage begins: After receiving the linear frequency modulation query signal, the SAW resonant sensor generates a resonant response based on its own resonant characteristics and outputs a first echo signal in the form of damped oscillation; the first echo signal is transmitted through space and then received by software radio to obtain the initial echo data of the sensor in its current state.

[0098] Next, the process enters the host computer time inversion processing stage, which is a key step in achieving resonance-related response enhancement: the host computer (i.e., the computer) performs time inversion processing on the primary echo baseband signal transmitted by software radio, specifically including time-domain signal inversion processing on the primary echo signal and energy normalization processing; through the above processing, the host computer generates a secondary transmission pulse signal that matches the current resonance state of the SAW sensor. This signal is no longer a pre-set fixed excitation, but is adaptively generated based on the actual echo, which can achieve targeted enhancement of the resonant frequency components.

[0099] Next, the secondary transmission signal transmission stage is performed: the reading device (integrated into the RF transmission module controlled by software radio or host computer) retransmits the secondary transmission pulse signal generated by the host computer to the SAW resonant sensor, completing the secondary excitation of the sensor.

[0100] Then, in the secondary echo reception stage: the SAW resonant sensor generates a secondary resonant response under the excitation of the secondary transmitted pulse signal and outputs a secondary echo signal; after spatial transmission, the secondary echo signal is received again by software radio. At this time, the frequency component corresponding to the actual resonant frequency of the sensor in the secondary echo signal has been coherently enhanced by time inversion processing, and the signal identification is significantly improved.

[0101] Finally, the frequency estimation and analysis stage is carried out: the host computer performs frequency estimation and analysis processing on the secondary echo signal received by the software radio, such as sampling, frequency domain transformation and peak search, and converts the resonance correlation response enhanced by LFM broadband coverage and time reversal (TR) retransmission into a frequency estimation result that can be directly decided, thereby completing the reading of the resonant frequency of the SAW resonant sensor.

[0102] In one non-limiting specific implementation of this embodiment, the following exemplary parameter configuration can be adopted: the query center frequency is set near the operating frequency band of the surface acoustic wave (SAW) sensor, the query bandwidth is set to 2 MHz, the frequency range of a single linear frequency modulation query is 433 MHz to 435 MHz, the pulse width is set to 140 μs, the working distance between the reader and the sensor is about 50 cm, and the baseband digital processing is completed by the host computer in conjunction with the software radio platform.

[0103] Simulation results based on the above parameter configuration show that, within a signal-to-noise ratio range of 0–20 dB, the root mean square error (RMSE) of frequency estimation using the method in this embodiment can be controlled within the 100 Hz range, which is about 60% lower than the traditional five-point sweep frequency method. Within a frequency drift range of 433 MHz–435 MHz, the root mean square error of frequency estimation using the method in this embodiment is basically stable at about 26 Hz, which is about 36% lower than the traditional five-point sweep frequency method, demonstrating excellent frequency estimation accuracy and anti-frequency drift performance.

[0104] The corresponding physical experiment results further verify that within the above-mentioned query bandwidth range, the method of this embodiment can obtain stable and reliable frequency estimation results, with a single measurement cycle of about 10 ms, which is about an order of magnitude shorter than the traditional point-by-point frequency scanning query method. This significantly improves the system's measurement efficiency and real-time performance, and can meet the application requirements of dynamic measurement scenarios.

[0105] The fast query method for surface acoustic wave sensors described in this application has the following beneficial effects:

[0106] 1. This embodiment uses a linear frequency modulated signal to perform a single broadband coverage query of the target frequency band. Compared with the traditional point-by-point frequency scanning or single-frequency probing query method, it eliminates the need for repeated transmission and detection at each frequency point within the target frequency band. It can complete the full coverage of the possible resonant frequency range of the SAW sensor within a single pulse duration, achieving rapid broadband query even when the resonant frequency is a priori unknown or drifting. This effectively solves the technical problems in existing technologies where traditional single-frequency queries easily lead to frequency mismatch, weakened echo signals, and the need for repeated scanning at multiple frequency points to cover the target frequency band when the resonant frequency changes. This technical feature allows this embodiment to maintain effective coverage of the entire frequency band even under conditions of uncertain resonant frequency, providing a stable foundation of resonant-related information for subsequent frequency readouts. It avoids detection failures or unstable estimations caused by deviations between the query frequency and the true resonant frequency. Simulation verification shows that within the frequency drift range of 433MHz to 435MHz, the root mean square error (RMSE) of frequency estimation in this embodiment remains relatively stable at approximately 26Hz, demonstrating excellent adaptability to frequency shift changes.

[0107] 2. This embodiment employs time-reversal (TR) processing, which involves conjugate inversion and energy normalization of the first received echo before retransmission. This ensures that the secondary transmitted signal is no longer a pre-set external excitation, but rather is adaptively constructed by the system based on the actual first echo. The secondary transmitted signal carries the resonance-related structural information retained after the first propagation, achieving reweighting and enhancement of the resonance-related frequency components. This increases the proportion of resonance-related response and solves the technical problems in the prior art where, under conditions of low signal-to-noise ratio, frequency mismatch, or changes in coupling state, the effective resonance components in the echo are weak, the spectral peaks are not prominent, and the frequency estimation accuracy and stability decrease. This technical feature enables the useful signal term in the secondary echo to be further coherently enhanced with the sensor frequency response, while the two received noises are only incoherently superimposed and do not form coherent enhancement. Therefore, the effective response ratio and signal-to-noise ratio at the resonant correlation frequency are significantly improved, greatly enhancing the accuracy and stability of frequency estimation. Simulation verification shows that within the 0-20dB signal-to-noise ratio range, the RMSE of the LFM+TR method in this embodiment is controlled in the order of hundreds of Hertz, which is about 60% lower than the traditional five-point frequency sweep method. Within the frequency drift range of 433MHz-435MHz, the RMSE is further reduced by about 36%. Experimental results show that within the test frequency band, the overall RMSE of the method in this embodiment is about 64% of that of the five-point frequency sweep method, and the frequency estimation accuracy is significantly improved.

[0108] It should be noted that this embodiment uses a five-point frequency sweep as the simulation comparison benchmark. In actual application scenarios, for a frequency band of 2MHz, traditional frequency sweeping usually uses a 10-point coarse sweep with a step of 0.2MHz. After determining the maximum echo frequency point through FFT transformation, a secondary fine sweep of about 5 points is required near that frequency point to obtain an accurate frequency estimate. The main time consumption comes from multiple FFT frequency estimates, with each estimate taking about 9ms. In contrast, the LFM+TR method in this embodiment can save about 150ms compared to traditional frequency sweeping in practical applications, with a total time consumption of only about 10ms, which is more significant.

[0109] 3. This embodiment employs a technical solution that performs only one frequency domain transformation and peak search on the secondary echo within a preset query bandwidth to complete the resonant frequency readout. Unlike traditional frequency sweeping methods, it eliminates the need for separate FFT and decision-making for multiple echoes at multiple frequency points. This reduces the number of frequency domain processing operations, shortens the single measurement cycle, and improves the system update rate. It solves the technical problem of existing point-by-point frequency sweeping methods, which require multiple independent transmissions and receptions and multiple frequency domain processings, resulting in high system processing overhead, long measurement cycles, and difficulty in meeting the rapid readout requirements of dynamic scenarios. With similar single transmission and reception times, this embodiment significantly shortens the query time by drastically reducing the number of FFT processing operations. Verification in the paper shows that compared to the five-point frequency sweeping method, the query time of this embodiment is reduced by approximately 80%, and the total query time is only 20% of that of the five-point frequency sweeping method. In the experiment, the single measurement cycle was approximately 10ms, which is about an order of magnitude shorter than the traditional frequency sweeping query. The corresponding system update rate is approximately 100Hz, demonstrating engineering application feasibility for dynamic measurement scenarios.

[0110] 4. The algorithm based on LFM excitation and time inversion processing in this embodiment can be implemented through software radio platforms or dedicated hardware such as FPGA and DSP. The frequency estimation step only requires one FFT and one peak search, with low computational complexity, which is convenient for real-time processing in embedded systems. If the FFT processing is migrated from the host computer to the hardware side, the single measurement cycle can be further compressed to the sub-millisecond to millisecond level, and the system update rate can be increased to the kHz level, which has excellent potential for engineering promotion and performance upgrade.

[0111] The scope of protection of the fast query method for surface acoustic wave sensors described in this application is not limited to the execution order of the steps listed in this embodiment. Any solution implemented by adding, subtracting, or replacing steps in the prior art based on the principles of this application is included within the scope of protection of this application.

[0112] like Figure 7 As shown, this application embodiment provides a surface acoustic wave (SAW) sensor rapid query system 100, applied to a SAW sensor 150, including: a signal processing and control module, a signal generation module, a signal receiving module, and a transceiver switching unit; the SAW sensor rapid query system 100 includes: a signal processing and control module 110, a signal generation module 120, a signal receiving module 130, and a transceiver switching unit 140, with each module working together to achieve rapid and high-precision query of the resonant frequency of the wireless passive SAW resonant sensor.

[0113] The signal processing and control module 110 is configured to send control commands to the signal generation module 120 to generate a query signal covering a preset query frequency band. The signal generation module 120 is configured to generate the query signal under the control of the signal processing and control module 110 and output the query signal to the transceiver switching unit 140. The transceiver switching unit 140 is configured to radiate the query signal to the surface acoustic wave sensor 150, receive the first echo output by the surface acoustic wave sensor 150 after being excited by the query signal, and output the first echo to the signal receiving module 130. The signal receiving module 130 is configured to perform radio frequency conditioning and demodulation processing on the first echo and transmit the processed first echo to the signal processing and control module 110. The signal processing and control module 110 is also configured to perform time reversal processing on the first echo to construct a secondary transmission signal. The system sends a secondary transmission control command to the signal generation module 120 to control the signal generation module 120 to generate the secondary transmission signal. The signal generation module 120 is also configured to generate the secondary transmission signal under the control of the signal processing and control module 110, and output the secondary transmission signal to the transceiver switching unit 140. The transceiver switching unit 140 is also configured to radiate the secondary transmission signal to the surface acoustic wave sensor 150, and receive the secondary echo output by the surface acoustic wave sensor 150 after being excited by the secondary transmission signal, and output the secondary echo to the signal receiving module 130. The signal receiving module 130 is also configured to perform radio frequency conditioning and demodulation processing on the secondary echo, and transmit the processed secondary echo to the signal processing and control module 110. The signal processing and control module 110 is also configured to perform frequency domain processing on the secondary echo to obtain the estimated value of the resonant frequency of the surface acoustic wave sensor 150.

[0114] In this embodiment, the signal processing and control module 110 is the core control and computing unit of the system, used to implement the entire process of command issuance, echo signal processing and frequency estimation; the signal generation module 120 is used to generate the excitation signal and RF conditioning under the control command; the signal receiving module 130 is used to receive, condition and demodulate the echo signal; the transceiver switching unit 140 is used to realize the switching of RF signal transmission and reception and wireless transmission; the surface acoustic wave sensor 150 is a wireless passive SAW resonant sensor, deployed at the measured location, used to receive the excitation signal and feed back the resonant echo, and the modules realize signal interaction through wired / wireless links.

[0115] In this embodiment, the signal processing and control module 110 first sends an initial query control command to the signal generation module 120, controlling the signal generation module 120 to generate a query signal covering a preset query frequency band. In one specific implementation of this embodiment, the query signal is a linear frequency modulated (LFM) signal, whose instantaneous frequency changes continuously and linearly with time within a preset pulse width. This signal can completely cover the preset query frequency band during a single transmission, adapting to application scenarios where the resonant frequency of the SAW sensor is unknown or drifting without point-by-point frequency scanning.

[0116] In this embodiment, after receiving the control command, the signal generation module 120 sequentially performs waveform generation, DA conversion, and radio frequency modulation and amplification processing: First, the waveform generation unit generates the baseband digital waveform of the linear frequency modulation query signal. Then, the DA conversion unit converts the digital waveform into an analog baseband signal. Next, the radio frequency modulation and amplification unit completes up-conversion modulation and power amplification, outputting a linear frequency modulation query signal that meets the requirements of radio frequency transmission, and outputting the signal to the transceiver switching unit 140.

[0117] Upon receiving the query signal, the transceiver switching unit 140 switches to the transmit link via an internal high-speed PIN switch. The reader antenna then radiates the linear frequency modulated query signal as electromagnetic waves to the surface acoustic wave (SAW) sensor 150, completing the initial broadband excitation of the SAW sensor. The reader has the capability to time-reverse and moderately amplify the received signal before retransmitting it as a baseband signal.

[0118] After receiving a linear frequency modulated query signal, the surface acoustic wave sensor 150 generates a resonant response based on its piezoelectric resonant characteristics and outputs a primary echo signal in a damped oscillation form after excitation ends. This primary echo signal is radiated by the sensor's antenna and transmitted wirelessly to the transceiver switching unit 140, where it is received by the reader antenna. Subsequently, a high-speed PIN switch switches to the receiving link, outputting the primary echo signal to the signal receiving module 130.

[0119] The signal receiving module 130 sequentially performs radio frequency filtering and amplification, AD conversion, and signal demodulation on the received primary echo signal: First, the radio frequency filtering and amplification unit performs bandpass filtering and low-noise amplification on the echo signal to eliminate out-of-band interference and increase the signal amplitude; then, the AD conversion unit converts the analog echo signal into a digital signal; then, the signal demodulation unit completes down-conversion demodulation and outputs a primary echo baseband digital signal containing sensor resonance-related information, and transmits this signal to the signal processing and control module 110 to complete the acquisition and transmission of the primary echo.

[0120] In this embodiment, the time inversion process includes at least: truncating an effective time window for a single echo, performing conjugate inversion processing on the truncated echo signal, and performing energy normalization processing on the conjugate inverted signal.

[0121] Specifically, after receiving the primary echo baseband digital signal, the signal processing and control module 110 performs time-reversal (TR) processing on it to construct a secondary transmission signal that adaptively matches the current state of the SAW sensor. The time-reversal processing includes at least: truncating the primary echo within an effective time window, eliminating invalid interference segments such as excitation tails and environmental reflections, and retaining only the effective signal segment of the sensor's resonant response; performing conjugate inversion processing on the truncated echo signal, i.e., reversing the complex baseband echo signal along the time axis and taking its complex conjugate; and performing energy normalization processing on the conjugate-inverted signal, using amplitude scaling to ensure that the transmission energy of the secondary transmission signal is comparable to that of the initial linear frequency modulation query signal, avoiding insufficient excitation or signal saturation due to energy differences.

[0122] Through the above processing, the signal processing and control module 110 constructs a secondary transmission signal. This signal is not a pre-designed standard excitation waveform, but is adaptively generated based on resonance-related information in an actual echo. The signal carries resonance-related structural information that highly matches the current resonance state of the sensor and the channel transmission characteristics. Subsequently, the signal processing and control module 110 sends a secondary transmission control command to the signal generation module 120, which then generates the secondary transmission signal.

[0123] The signal generation module 120 performs waveform generation, DA conversion, RF modulation and amplification processing on the secondary transmission signal according to the same process as the initial signal generation, converts it into an RF signal that meets the transmission requirements, and outputs it to the transceiver switching unit 140.

[0124] The transceiver switching unit 140 switches back to the transmit link and radiates the secondary transmit signal to the surface acoustic wave sensor 150 through the reader antenna. Since the secondary transmit signal has completed adaptive matching for the current resonant state of the sensor, the SAW sensor generates a secondary resonant response under the excitation of this signal. After the excitation ends, it outputs a secondary echo signal. The component in the secondary echo corresponding to the actual resonant frequency of the sensor is further enhanced by the coherent effect of the two excitations, while the non-resonant components and noise interference are relatively suppressed.

[0125] After being transmitted via the wireless channel, the secondary echo signal is received by the reader antenna of the transceiver switching unit 140. The high-speed PIN switch switches to the receiving link, and the secondary echo signal is output to the signal receiving module 130. The signal receiving module 130 performs RF filtering and amplification, AD conversion, and signal demodulation on the secondary echo according to the same process as the primary echo processing, converting it into a secondary echo baseband digital signal, and transmitting it to the signal processing and control module 110 to complete the acquisition of the secondary echo.

[0126] The signal processing and control module 110 performs frequency domain processing on the received secondary echo baseband digital signal to obtain an estimate of the resonant frequency of the SAW sensor. Specifically, the frequency domain processing includes: sampling the secondary echo to form a discrete-time series; performing a Fast Fourier Transform (FFT) on the discrete-time series to obtain the spectral distribution of the secondary echo within a preset query bandwidth; and performing a peak search within the preset query bandwidth, using the frequency corresponding to the peak with the largest amplitude in the spectrum as the estimated resonant frequency of the surface acoustic wave sensor 150, thus completing the entire fast query process. In this embodiment, only one Fast Fourier Transform is needed to obtain the sensor's resonant frequency.

[0127] In one implementation of this embodiment, the method of searching the spectral peaks can be, but is not limited to, FFT peak search, interpolation peak search, or local spectrum fitting search. Those skilled in the art can flexibly choose the appropriate method based on the accuracy and real-time requirements of the actual application scenario.

[0128] In one implementation, the signal processing and control module 110, the signal generation module 120, and the signal receiving module 130 can be integrated into a software, and their functions can be implemented by running the software through an electronic device (computer or server, etc.).

[0129] In other embodiments, the signal processing and control module 110, the signal generation module 120, and the signal receiving module 130 may implement their specific functions through baseband digital processing equipment and software radio transceivers.

[0130] Wherein: the baseband digital processing device controls the software radio transceiver to generate a query signal covering a preset query frequency band; the baseband digital processing device controls the software radio transceiver to transmit the query signal to the surface acoustic wave sensor 150 through the transceiver antenna, and receives the primary echo output by the surface acoustic wave sensor 150 after being excited by the linear frequency modulated query signal; the baseband digital processing device performs time-reversal processing on the primary echo to construct a secondary transmission signal; the baseband digital processing device controls the software radio transceiver to transmit the secondary transmission signal to the surface acoustic wave sensor 150 through the transceiver antenna, and receives the secondary echo output by the surface acoustic wave sensor 150 after being excited by the secondary transmission signal; the baseband digital processing device performs frequency domain processing on the secondary echo to obtain an estimated value of the resonant frequency of the surface acoustic wave sensor 150.

[0131] The software-defined radio transceiver described in this embodiment is configured to generate and transmit linear frequency modulation query signals and secondary transmission signals, as well as receive, down-convert, and transmit primary and secondary echoes, under the command and control of the control unit, providing radio frequency transceiver link support for the entire query system.

[0132] In one specific implementation of this embodiment, the software-defined radio transceiver can adopt the USRP-B200 software-defined radio platform. This platform has wideband transceiver capability, high sampling rate and flexible programmability, which can meet the requirements of linear frequency modulation signal generation and echo reception in this embodiment. At the same time, this embodiment is not limited to this specific model of equipment. Any software-defined radio platform with integrated transceiver capability, capable of radio frequency signal transmission and reception and down-conversion processing, can be configured as the technical solution of this embodiment to achieve the same functional effect.

[0133] The transceiver antenna described in this embodiment is configured to perform spatial radiation of radio frequency signals and reception of echo signals, realizing wireless communication between the query system and the wireless passive SAW resonant sensor. In one specific implementation of this embodiment, the transceiver antenna can adopt a single-antenna time-division multiplexing structure, that is, the same antenna is used to perform time-division multiplexing of query signal transmission and echo signal reception, simplifying the system structure and reducing hardware costs. At the same time, this embodiment can also adopt a separate transmit and receive antenna structure, with the transmit antenna dedicated to radiating the query signal and the receive antenna dedicated to collecting the echo signal, avoiding co-channel interference between transmit and receive, and further improving the system's receiving sensitivity and signal-to-noise ratio. Those skilled in the art can select a suitable antenna structure to implement the technical solution of this embodiment according to the needs of the actual application scenario.

[0134] The baseband digital processing described in this embodiment includes effective time window truncation of the first echo, conjugate inversion processing, energy normalization processing, and algorithmic steps such as sampling of the second echo, fast Fourier transform, and spectral peak search. The implementation entity can be flexibly selected according to the system deployment scenario and performance requirements. In one specific implementation of this embodiment, the baseband digital processing can be performed by a computer, utilizing the computer's general computing power to achieve rapid algorithm development and debugging. Simultaneously, the core algorithm of this embodiment possesses low complexity and high parallelism characteristics, and can also be implemented by dedicated hardware such as field-programmable gate arrays (FPGAs), digital signal processors (DSPs), or system-on-a-chip (SoCs). Hardware acceleration further improves signal processing speed, shortens the single measurement cycle, and meets the application requirements of embedded, portable, or high real-time dynamic measurement scenarios, achieving the functional effects of this embodiment.

[0135] The surface acoustic wave sensor 150 fast query system of this embodiment realizes the technical solution of linear frequency modulation broadband coverage → single echo acquisition → time inversion adaptive enhancement → secondary excitation → single frequency domain readout. Compared with the traditional point-by-point frequency scanning query system, it achieves the following significant technical effects:

[0136] This application achieves single-shot broadband coverage lookup by employing a linear frequency modulated signal, enabling coverage of a range of possible resonant frequencies within a single pulse duration. This solves the problems of frequency mismatch, echo attenuation, and repetitive scanning at multiple frequency points when the resonant frequency is unknown or drifting. It achieves fast broadband lookup and exhibits good adaptability to frequency shifts. Combined with time-reversal processing technology, the system adaptively constructs a secondary transmission signal based on a single actual echo, enhancing the resonant-related frequency components, increasing the effective response ratio and signal-to-noise ratio, and significantly improving the accuracy and stability of frequency estimation. The resonant frequency readout can be completed with only one frequency domain transformation and peak search on the secondary echo, greatly reducing the number of frequency domain processing steps, shortening the measurement cycle, and increasing the system update rate, meeting the rapid readout requirements of dynamic scenarios. Simultaneously, the core algorithm has low computational complexity and can be implemented through a software radio platform or dedicated hardware, facilitating real-time processing in embedded systems and engineering application. Further migration to hardware processing can also improve system performance. Therefore, this application effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0137] The above embodiments are merely illustrative of the principles and effects of this application and are not intended to limit this application. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this application. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this application should still be covered by the claims of this application.

Claims

1. A fast query method for surface acoustic wave sensors, characterized in that, include: Generate a query signal covering the preset query frequency band; The query signal is sent to the surface acoustic wave sensor, and the first echo output by the surface acoustic wave sensor after being excited by the linear frequency modulation query signal is received. The first echo is subjected to time reversal processing to construct a second transmission signal; The secondary transmission signal is sent to the surface acoustic wave sensor, and the secondary echo output by the surface acoustic wave sensor after being excited by the secondary transmission signal is received. The secondary echo is processed in the frequency domain to obtain the estimated resonant frequency of the surface acoustic wave sensor.

2. The rapid query method for surface acoustic wave sensors according to claim 1, characterized in that, The range of the preset query frequency band matches the resonant frequency range of the surface acoustic wave sensor, covering all possible frequency ranges after the resonant frequency of the surface acoustic wave sensor is unknown or has drifted.

3. The rapid query method for surface acoustic wave sensors according to claim 1 or 2, characterized in that, Within a preset pulse width, the instantaneous frequency of the query signal changes continuously with time.

4. The rapid query method for surface acoustic wave sensors according to claim 1, characterized in that, The query signal is a linear frequency modulated query signal.

5. The rapid query method for surface acoustic wave sensors according to claim 1, characterized in that, The first echo is output in the form of a damped oscillation after the surface acoustic wave sensor is excited; the first echo contains frequency structure information related to the actual resonant frequency of the surface acoustic wave sensor.

6. The rapid query method for surface acoustic wave sensors according to claim 1, characterized in that, The step of performing time reversal processing on the primary echo to construct the secondary transmission signal includes: The first echo is truncated within an effective time window, and the truncated first echo is subjected to conjugate inversion processing. The signal after conjugate inversion is normalized by energy to obtain the secondary transmission signal.

7. The rapid query method for surface acoustic wave sensors according to claim 5, characterized in that, The conjugate inversion process involves flipping the first echo on the time axis and taking its conjugate; the energy normalization process ensures that the second transmitted signal and the first echo remain comparable in transmitted energy.

8. The rapid query method for surface acoustic wave sensors according to claim 1, characterized in that, The step of performing frequency domain processing on the secondary echo to obtain the estimated resonant frequency of the surface acoustic wave sensor includes: The secondary echoes are sampled to form a discrete time series; Perform a Fast Fourier Transform on the discrete time series to obtain the spectral distribution of the second echo within a preset query bandwidth; A spectral peak search is performed on the spectral distribution within the preset query bandwidth, and the frequency corresponding to the searched spectral peak is used as the estimated resonant frequency of the surface acoustic wave sensor.

9. The rapid query method for surface acoustic wave sensors according to claim 8, characterized in that, The spectral peak search method is FFT peak search, interpolation peak search, or local spectrum fitting search.

10. A rapid query system for surface acoustic wave sensors, characterized in that, Applied to surface acoustic wave sensors, it includes: a signal processing and control module, a signal generation module, a signal receiving module, and a transceiver switching unit; The signal processing and control module is configured to send control commands to the signal generation module to control the signal generation module to generate a query signal covering a preset query frequency band; The signal generation module is configured to generate the query signal under the control of the signal processing and control module, and output the query signal to the transceiver switching unit. The transceiver switching unit is configured to radiate the query signal to the surface acoustic wave sensor, receive the first echo output by the surface acoustic wave sensor after being excited by the query signal, and output the first echo to the signal receiving module. The signal receiving module is configured to perform radio frequency conditioning and demodulation processing on the first echo, and transmit the processed first echo to the signal processing and control module. The signal processing and control module is also configured to perform time reversal processing on the primary echo to construct a secondary transmission signal, and to send a secondary transmission control command to the signal generation module to control the signal generation module to generate the secondary transmission signal. The signal generation module is further configured to generate the secondary transmission signal under the control of the signal processing and control module, and output the secondary transmission signal to the transceiver switching unit; The transceiver switching unit is further configured to radiate the secondary transmission signal to the surface acoustic wave sensor, receive the secondary echo output by the surface acoustic wave sensor after being excited by the secondary transmission signal, and output the secondary echo to the signal receiving module. The signal receiving module is also configured to perform radio frequency conditioning and demodulation on the secondary echo and transmit the processed secondary echo to the signal processing and control module. The signal processing and control module is further configured to perform frequency domain processing on the secondary echo to obtain an estimated value of the resonant frequency of the surface acoustic wave sensor.

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