A ring-diode capacitive detection circuit based on square-wave modulation was designed for a symmetrically sensitive interface with an arc-shaped differential capacitive electrode，focusing on the dynamic characteristics and electromechanical energy conversion features of a microelectromechanical silicon-based vibrating ring gyroscope. First，a double-layer fully symmetrical arc-shaped differential capacitive electrode interface scheme with the electrode center axis coinciding with the principal axis of the working mode is proposed，and an electrical sensitivity model of the mechanical vibration parameters of the ring-shaped sensitive structure is studied. Next，a ring-diode capacitive detection circuit with a square-wave carrier form is proposed to avoid coupling interference from co-frequency driving signals. It modulates weak capacitive detection signals onto a high-frequency carrier and then demodulates them to obtain the output signal of the microgyroscope. Subsequently，a control model for reading sensitive signals in the detection mode was designed，and its stability was analyzed. Additionally，an electromechanical control model for the signal-sensing system was developed and validated through simulation analysis. Finally，a control circuit for reading sensitive signals was designed based on the aforementioned scheme，and its performance was tested. The experimental results showed that the control scheme of this sensitive interface detection circuit can quickly and effectively read sensitive signals，and the forward scale factor was 0.593 9 mV/［（°）·s-1］，whereas the reverse scale factor was 0.594 6 mV/［（°）·s-1］，resulting in a scale factor asymmetry of merely 0.12%.

Traditional fiber-optic gyroscopes employ classical light as their light source，and the phase detection sensitivity in classical interference is ultimately constrained by shot noise and cannot be improved further. Methods for further improving the accuracy of fiber-optic gyroscopes have been investigated. By utilizing the correlation characteristics of quantum entangled photon pairs through the adoption of the maximally path-entangled state（2002 state），the phase detection sensitivity in optical interferometry can be enhanced by a factor of √2 compared with the shot noise limit，thereby achieving the Heisenberg limit. An integrated two-photon entanglement-enhanced fiber-optic gyroscope system comprising a high-efficiency entangled photon source，an all-fiber Sagnac interferometric optical path，and a coincidence detection system was designed and implemented. Rotation experiments were conducted using this integrated system，with experimental data acquisition and complete interference waveforms determining the relationship between the rotation rate and photon counts. The experimental results demonstrate that this system can be effectively applied to principal verification experiments and functional testing of two-photon entanglement-enhanced fiber-optic gyroscopes.

With the rapid development of microelectromechanical systems（MEMS）technology，small，lightweight，and mass-produced inertial devices have been achieved. In this context，array technology has emerged to achieve high-precision inertial measurements at low costs. This article provides an overview of the development of MEMS inertial measurement unit（IMU）array technology. First，by analyzing the research results over the years，the development process of IMU arrays is summarized. Second，the key technologies and development status of IMU arrays are introduced，including error analysis modeling and calibration，data fusion，fault detection，and isolation technologies. Finally，the characteristics and limitations of previous research results are summarized，future research directions are discussed，and some ideas for further improving the accuracy of IMU arrays are proposed. These provide a reference for the research and engineering practice of IMU array technology in the field of high-precision navigation.

As a critical device for navigation and attitude control，the inertial measurement unit（IMU）in control systems is required to deliver high navigation accuracy and real-time performance. Conventional methods for designing low-pass digital filters in IMUs suffer from significant time delay issues. To this end，this paper proposes a low-latency digital filter design approach. The low-pass infinite impulse response（IIR）filter effectively attenuates high-frequency noise and reduces low-frequency noise interference. The improved IIR notch filter model limits the amplitude of noise at high-energy frequency points. The experimental results show that the proposed low-latency digital filter design not only simplifies the implementation process but also improves filtering accuracy in dynamic scenarios compared to traditional approaches. With a 2.6 ms reduction in time delay，this method demonstrates considerable potential for engineering applications.

In this paper，a synchronous north-finding algorithm based on a relative azimuth constraint is proposed for a single-axis forward and reverse continuous rotation modulation north-finding system. Based on velocity observations，the relative azimuth error in the north-finding process was used as the observation measurement，and the convergence speed of the azimuth error angle was improved. First，the influence of the gyroscope bias error，gyroscope scale factor error，and goniometric mechanism on the north-finding accuracy of uniaxial forward and reverse continuous rotation was analyzed，and a compensation scheme was developed. Subsequently，forward rotation and reversal were used as two north-finding states to construct a systematic error model under the condition of a static base，and a measurement equation was established based on the velocity and relative azimuth error. Finally，the experimental data verified the effectiveness of the algorithm，and the results showed that the algorithm can effectively improve the accuracy and shorten the accuracy of the north search. The accuracy of the north-finding in 5 min is better than 10"（1），which has significant engineering practical value.

The statistical characteristics of noise in integrated micro inertial measurement unit/global navigation satellite systems（MIMU/GNSS）are difficult to obtain in complex environments，and simplified probabilistic assumptions may lead to performance degradation or even failure of the navigation system. To enhance the adaptability of navigation systems in complex environments while maintaining navigation accuracy and real-time performance，a rapid fusion algorithm is proposed for MIMU/GNSS based on the assumption of unknown but bounded noise. Building upon the input-to-state stable ellipsoidal bounding filter，this algorithm optimizes bounding ellipsoid parameters through relaxation of the optimization objective，thereby avoiding solutions to nonlinear equations and reducing computational complexity. The rapid algorithm was applied to MIMU/GNSS-integrated navigation experiments. The experimental results demonstrated that the proposed rapid fusion algorithm effectively improves system navigation accuracy while ensuring real-time navigation performance.

To improve the health status evaluation accuracy of inertial navigation systems，we developed a new characteristic reliability calculation method based on wave distance. It aims to address problems such as a lack of fault data，uncertain knowledge，and complex environmental disturbances. The degree of interference was measured using the wave distance from the historical data. Subsequently，a belief rule-based expert system considering the characteristic reliability was constructed. Health status was evaluated using a combination of unreliable data and uncertain expert knowledge. A case study was conducted based on observation data from the gyroscopes and accelerometers of an inertial navigation system. The accuracy of the developed method is 0.283 8. Compared with the traditional belief rule-based model，its accuracy is higher by 15.28%.

The acoustic characteristics of laterally excited bulk acoustic resonators（XBARs），based on a flexible polyethylene naphthalate（PEN）substrate，including the resonance frequency fr，electromechanical coupling coefficient K2eff，quality factor Qr，and temperature coefficient of frequency（TCF），are analyzed using finite-element method（FEM）. The results indicate that the XBAR performances improve upon introducing the flexible PEN substrate. For instance，for hPEN = 40 nm，an IDT/LiNbO3/PEN structure shows K2eff=35.68%，which is 35% higher than that of the IDT/LiNbO3 structure with the same parameters，while maintaining fr =4.4 GHz and Qr =112. At a special height of PEN，the PEN substrate and IDT/LiNbO3 show synchronized vibrations—coupled resonance，which increases the resonant frequency and quality factor of XBAR. At hPEN=105 nm，the frequency shift f and quality factor shift Qr of XBAR are 1.32 GHz and 75，respectively，owing to coupled resonance. In addition，the temperature stability of the XBAR with the IDT/LiNbO3/PEN structure is enhanced；TCF of the XBAR increases from −107×10−6/°C to −72.9×10−6/°C as hPEN increases from 0 nm to 120 nm. These results indicate that the XBAR with the IDT/LiNbO3/PEN structure shows outstanding acoustic properties，and the different performance parameters of the XBAR can be optimized by modulating the thickness of PEN flexible substrate. In addition，these results provide a theoretical basis for the design and development of XBARs with high frequencies，electromechanical coupling coefficients，and temperature stability.

In this paper，a new method for nondestructive detection of the geometric features of thin films using a portable single-port surface acoustic wave（SAW）resonator based on lithium niobate（LiNbO3）is presented. The measured thin-film structures include single metal，double-layer，and Damascus-structure films. After simulating the S-parameter curve using the finite element method，we obtained the relationship curve between the resonant frequency of the SAW resonator and the corresponding geometric parameters in a certain range through fitting，which was expressed using a third-order polynomial. The results showed that the coefficient of determination R2 of the fitting curve representing the relationship between the geometric features and resonant frequency obtained by fitting the finite element simulation results can exceed 0.999 0，and the fitting polynomial can accurately characterize the relationship between the geometric features and resonant frequency of the resonator. The resonant frequency of a sample with unknown geometric dimensions was measured using the proposed method and substituted into the corresponding formula to calculate the geometric dimensions of the sample. The results showed that the SAW resonator has significant potential for the rapid non-destructive detection of thin-film geometric features.

In this study，a surface acoustic wave（SAW）resonator，based on an X-cut LiNbO3-on-Insulator（LNOI）substrate，is investigated. Pseudofinger length weighting techniques is used to suppress transverse modes while precisely maintaining the resonator’s quality factor（Q factor）. SAW resonators with different weighting electrodes are designed and fabricated. Then，the effects of weighting period and amplitude on the transverse modes are systematically investigated. A comparative analysis reveals the optimal weighted electrode configuration for the X-cut LNOI SAW resonator at a frequency of 2.5 GHz. Experimental results show that the weighted electrode effectively mitigates transverse modes induced by the X-cut LiNbO3 material，thereby enhancing the overall performance of the SAW resonator.

Clutter suppression is a significant challenge for high-performance surface acoustic wave（SAW）resonators. To suppress the clutter occurring in high-frequency broadband resonators，we excited the S0 mode surface acoustic wave on a X-40°Y-LiNbO3（LN）/SiO2/Ta2O5/SiO2/Ta2O5/SiO2/Si substrate structure and obtained a high-frequency broadband resonator. Subsequently，an in-depth analysis of clutter suppression was conducted. Two novel IDT design schemes were proposed，simulated，and fabricated for verification. The simulation and fabrication results showed that the proposed three-busbar IDT structure provided good clutter suppression for high-frequency broadband resonators while maintaining the quality factor（Q）to values comparable to those of normal type resonators. The suppression effect of different finger shapes on clutter in the S0 mode of the resonator was also tested through fabrication.

To enhance the performance of high-frequency filters used in the 5G era，a surface acoustic wave（SAW）resonator，based on the SMR structure，with X-37°Y LiNbO3 as the piezoelectric substrate was studied. The influence of resonator structure parameters on performance was investigated by two- and three-dimensional finite-element simulations，whose results were verified through wafer fabrication. The results show that the resonator performance is optimal when the rotation angle in this structure is 37°，and increasing the tilt angle can enhance the suppression effect on the lateral mode spurious. However，when the tilt angle exceeds 18°，the effect weakens，and new spurious is introduced. The tilted small hammer structure can improve the quality factor（Q）of the resonator to a certain extent for the tilted structure. These results underscore the tilted small hammer structure with a tilt angle of 15°-18° as the best solution. This structure can balance spurious suppression and Q-value maintenance，providing design guidance for high-frequency SAW filters.

To control incident electromagnetic waves and reduce RCS，this study used the PB geometric phase theory to design various semi-circular cross-arm-shaped element structures with different rotation angles and optimized the arrangement of the element array using the GA algorithm. By introducing polarized and circularly polarized waves into different frequency bands，this metasurface can induce phase transitions in electromagnetic waves. Simulations were conducted on the designed metasurface array with an average RCS reduction of 16 dB for linearly polarized incident waves and 10 dB for circularly polarized incident waves in the frequency range of 7.82-18.42 GHz. Compared with traditional metasurfaces，this design has the advantages of a wide bandwidth，high polarization conversion rate，small size，and low cost.

Hemispherical resonator gyros are widely used for spacecraft attitude control. In this study，the noise composition of a hemispherical resonator gyro was analyzed using Allan variance and compared with that of fiber-optic and MEMS gyro. The results of the Allan variance analysis showed that the noise of the hemispherical resonator gyro is primarily quantization noise，and the component of the angle random walk is very small，whereas the noise of the fiber-optic and MEMS gyroscopes is composed of an angle random walk and basically no quantization noise. Therefore，the quantization noise should be reduced to reduce the noise of the hemispherical resonator gyro. By adjusting the circuit parameters，the noise of the gyro was reduced，which proves the effectiveness of the measures and indicates a direction for further reducing the noise of the hemispherical resonator gyro.

This study proposes an attitude solution method based on the fusion of an adaptive extended Kalman filter and a Mahony filter to address the limitations of low-cost inertial measurement units，such as restricted accuracy，high noise，and severe drift. The proposed method employs the Mahony filter to estimate the attitude in real time while using the adaptive extended Kalman filter to adjust the process and measurement noises dynamically，thereby optimizing the attitude estimation results. The effectiveness of the proposed algorithm was validated through static experiments，attitude accuracy tests，and experiments in real-world scenarios. The experimental results indicate that the fusion algorithm outperforms the fusion algorithm based on the extended Kalman and Mahony filters in terms of the pitch，roll，and yaw accuracy，achieving a 52.8% reduction in the closed-loop error in practical applications. This method effectively suppresses noise and drift，improves the attitude estimation accuracy，and provides a reliable solution for high-precision attitude determination in complex environments.

In this study，the efficiency of an energy conversion model for the piezoelectric bimorph cantilever beam generator（PMCBG）was established. The influence of the structural parameters and material properties of the PMCBG on the energy conversion efficiency was studied through numerical simulations and experimental testing. The research results show that the thickness ratio（TR）and Young’s modulus ratio（YMR）parameters affect the energy conversion efficiency of the PMCBG. Optimal TRs exist for the PMCBG to obtain maximal energy conversion efficiency in different metal-plate materials. When copper，aluminum，and molybdenum plates were used for the substrate，the PBCBG achieved optimal TRs of 0.3，0.1，and 0.2，respectively. With the same thickness ratio（0.3）and external excitation conditions，the energy conversion efficiency of the PMCBG using a molybdenum substrate was higher than that using copper or aluminum. When the YMR increased，the energy conversion efficiency of the PMCBG decreased but did not change significantly.

To address the low signal-to-noise ratio in defect detection caused by high noise levels and complex modes of ultrasonic signals of thick-walled austenitic stainless steel welds，a total focusing method based on a one-transmitter，one-receiver longitudinal wave（TRL）dual-matrix array with variable mode decomposition（VMD）noise reduction was proposed. Transverse hole defects with a depth of 10-70 mm and a diameter of 3.2 mm were machined on the austenitic stainless steel weld test block with a thickness of 76 mm，and a TRL probe with a center frequency of 2.25 MHz was selected to collect full matrix capture（FMC）data. The grey wolf optimizer was used to optimize the penalty factor coefficient and decomposition level of the VMD of the FMC signal，and the full data matrix was reconstructed according to the spectral energy distribution and cross-correlation coefficient of the modal components. The superposition rule for the acoustic beam propagation delay in three-dimensional space was established，and the FMC noise reduction signal was imaged using the total focusing method. The results showed that the defect signal-to-noise ratio of the VMD denoising imaging increased by 4.69-6.85 dB compared with the imaging results of the original FMC data，thereby effectively improving the weld detection effect.

In this study，a wafer-level packaging（WLP）process for surface acoustic wave（SAW）filters，based on silicon cap bonding technology，is developed to meet the stringent requirements for hermeticity，mechanical strength，and thermal performance in high-frequency communication systems. A packaging structure with superior hermeticity，thermal dissipation，and reliability is formed by optimizing the deep silicon etching process of through-silicon via（TSV）holes and the LT layer etching process，followed by depositing an SiO2 passivation layer using the low-temperature plasma enhanced chemical vapor deposition method（PECVD）. Reliability tests demonstrate that the silicon-cap-bonded WLP exhibits a frequency drift of only 2M to 2.5M（B40 band）after unbiased highly accelerated stress testing（uHAST），significantly outperforming traditional polyimide-based WLP（5M to 6M）. This process provides robust technical support for high-performance wafer-level packaging of SAW filters.

Silicon carbide（SiC）thin films were successfully deposited on the C-plane of 4H-SiC substrates using plasma-enhanced chemical vapor deposition（PECVD）technology. With the help of field emission scanning electron microscopy（SEM），energy dispersive spectroscopy（EDS），and atomic force microscopy（AFM），the influence of deposition temperature，power and total gas flow rate on film roughness，deposition rate，and carbon-to-silicon ratio was investigated comprehensively. The experimental results show that when the total gas flow rate increases，the deposition rate of the film gradually increases，and carbon-to-silicon atomic ratio also increases accordingly；however，the surface of the film becomes rougher. As power increases，the deposition rate of the film gradually decreases；carbon-to-silicon atomic ratio first increases and then decreases；and film roughness decreases. As temperature increases，the deposition rate of the film gradually decreases，and the atomic ratio of carbon to silicon also gradually decreases，resulting in a decrease in film roughness.

To evaluate the performance and optimize the structure of Love-wave surface acoustic wave（SAW）sensors in liquid-phase biosensing，we propose a bilayer waveguide structure of Au/SiO2，with Cr used as the adhesion layer between SiO2 and Au to improve the adhesion and density of SiO2 deposited on Au. The feasibility of the Love-wave SAW bilayer waveguide structure was theoretically verified from the aspect of mass-loading sensitivity using finite element simulation software. The simulation results showed that the mass sensitivity reached the optimal value of−29.83 kHz·cm2/μg when Au=0.1 μm and SiO2=2 μm. The thickness of Au=0.1 μm was consistent with the electrode thickness，and in subsequent experiments，the Au waveguide and electrode layers were fabricated together. In the experiment，a delay-line SAW device with a single Au waveguide layer on an ST-90°X quartz substrate was prepared using MEMS processes. The second waveguide layer of SiO2 was deposited using PECVD，and aluminum films were grown in the delay line region as mass loads using thermal evaporation. The corrosion effect of the TMAH solution on the aluminum film was utilized，and a real-time detection system for the mass-loading sensitivity of SAW devices suitable for liquid-phase biosensors was employed to monitor the phase changes of the devices in real time，thereby verifying and evaluating the sensitivity of the bilayer waveguide SAW sensors. The results showed that the maximum phase change of the device was 124° when Au=0.1 μm，SiO2=0.15 μm，and Al=0.15 μm. Under optimal parameters，by changing the thickness of the aluminum film，the sensitivity of the bilayer waveguide SAW sensor reached 0.81（°）/nm，demonstrating good linearity and stability.

To meet the requirements of high performance and miniaturization for intermediate frequency（IF）filters in radio frequency（RF）receivers while considering passive intermodulation（PIM）interference from passive components，an LC high-performance filter was designed and implemented based on an eighth-order elliptic function with a nominal frequency of 81 MHz. The filter measured 14 × 5.5 ×5 mm3，achieving a relative bandwidth（BW）of approximately 26.84%，a shape factor（BW40dB/BW3dB）of less than 1.78，a stopband rejection of up to 60 dBc at a far-end frequency of 1 GHz，a voltage standing wave ratio of ≤1.28，a minimum in-band insertion loss of 3.2 dB，an in-band phase consistency within the same batch of ≤ ±6°，and a PIM power level of -77 dBm. The filter design exhibited excellent agreement with the specifications，showing significant practical utility.

This study is focused on the feasibility of using a novel piezoelectric material PMN-PT，with an electromechanical coupling coefficient of approximately 39.2%，as a piezoelectric material for bulk acoustic wave devices. Based on the air-gap thin film bulk acoustic wave resonator（FBAR），a two-dimensional finite element simulation model of the fused structure FBAR is proposed using the finite-element simulation method. The admittance and Q-value curves of the FBAR，with the aforementioned two structures，are compared via finite-element simulation analysis to verify the clutter suppression and Q-value enhancement ability of the fusion structure for S- and C-band devices. A low-clutter，high-Q-value FBAR based on PMN-PT is designed. The simulation results show that the designed fusion structure can effectively suppress the clutter generated by air-gap FBAR，while increasing the Q-values of S- and C-band devices by 101.8% and 350.4%，respectively.

In response to the narrow operating frequency band and low energy harvesting efficiency of traditional single-well piezoelectric harvesters in low-frequency，low-amplitude environments，and the complexity and necessity for external components in conventional bistable piezoelectric harvesters，this paper proposes a novel piezoelectric energy harvester based on a local bistable structure. This structure，inspired by the physical structure of a soybean pod，combines local bistable design with piezoelectric materials，significantly enhancing the capture of low-frequency vibrational energy and broadening the operational frequency band. Experimental results demonstrated that at a wind speed of 2.5 m/s，the proposed harvester achieved a 2 077.78% higher output power density than the single-well structure. Even at a higher wind speed of 5.1 m/s，the output power density remained 66.27% higher than that of the single-well structure. These findings indicated that the local bistable structure outperformed the single-well piezoelectric harvester in most environmental scenarios. Additionally，in experiments combined with the LTC3588 circuit，the piezoelectric energy harvester with a local bistable structure showed a more sensitive response to slight increases in wind speed，and the output signal was significantly improved.

Piezoelectric energy-harvesting technology is a critical solution to the power supply challenges of wireless sensor nodes. To address the limitations of conventional straight-beam piezoelectric energy harvesters，such as their high resonant frequency and low output power，we designed and investigated wedge-shaped beam structures using finite element simulations. A static mechanical comparative analysis was conducted to evaluate the stress distribution on piezoelectric materials in different wedge-shaped beams and traditional straight-beam structures. Modal analysis was performed on the wedge-shaped beam to elucidate the relationship between the structural parameters and resonant frequency. Finally，the power-generation performance of the wedge-shaped piezoelectric energy harvesters was systematically studied. The results indicated that the wedge-shaped structure with a linear increase in thickness from the fixed end to the free end exhibited lower resonant frequencies，which could result in a larger stress distribution within the piezoelectric material. Under a 0.5 g excitation level，the maximum output power of the tapered-beam piezoelectric energy harvester reached 1.6 times that of the corresponding traditional straight-beam structure.

The piezoelectric-driven nanopositioning stage encounters problems such as low damping resonance and phase lag，which significantly affect the positioning stability and trajectory tracking accuracy of the stage. To address these problems，first，this paper designs a high-performance feedback controller that includes a notch filter and PI control to effectively suppress the low damping resonant mode of the platform. Second，based on the above feedback control，a tracking-error estimation feedforward compensation control method is designed，which utilizes the sensitivity function of the feedback system to estimate the tracking error and adds it to the reference signal as feedforward compensation，further reducing the phase lag during trajectory tracking. Finally，various trajectory signal tracking experiments were conducted on the piezoelectric-driven nanopositioning stage using the designed feedback controller and tracking-error estimation feedforward compensation controller to verify the effectiveness of the algorithm. The experimental results showed that after adding the tracking-error estimation feedforward compensation，the root mean square error and maximum error of the stage decreased by more than 50%，which can effectively improve the stability and tracking accuracy of the stage.

A high-precision motion control system for an in-plane longitudinal bending composite mode linear piezoelectric actuator is proposed. This system can realize precise output control with nanometer position error and millimeter velocity error and ensure accurate tracking of the predefined reference trajectory. The control system combines a sliding-mode state observer（SMO）with a disturbance observer（DOB）for real-time observation of the system state and external disturbances. The position sensor and SMO are used to estimate the system state values accurately，and the radial basis function neural network controller is used to adjust the parameters adaptively online to ensure precise control of the piezoelectric actuator based on the error-generating control law. The synergistic effect of the DOB and SMO significantly reduces the observation error and strengthens the resistance of the system to disturbances. In addition，this study derives the stability of the control law based on the Lyapunov stability，and the effectiveness of the method is verified through simulations and experiments. The actual position error is controlled within ±60 nm，and the velocity error is controlled within ±0.025 mm/s.

To address the problem of insufficient preload in screw-rod linear ultrasonic motors（LUMs），we developed a novel screw-rod LUM with an adjustable preload by incorporating a separable stator structure capable of bidirectional preload adjustment. Through theoretical analysis and experimental research，a preload-friction model was established to reveal the relationships among the preload，output torque，and critical speed. The corresponding preload-output torque–speed curves were derived. A prototype of the ultrasonic motor was developed，and an experimental platform was constructed. The relationship between the output force and preload was fitted to a quadratic function. The experimental results demonstrated that the optimized novel structure improved the reverse output force by 20.3%，thereby providing theoretical and practical support for the application of screw-rod ultrasonic motors in high-precision drive fields.

With the increasing demand for imaging in the diagnosis and treatment of musculoskeletal disorders，developing high-performance musculoskeletal ultrasound transducers，featuring higher central frequencies，wider bandwidths，higher sensitivity，and better directivity，is crucial. Traditional lead zirconate titanate（PZT）ceramics，exhibiting narrow bandwidths，complex vibration modes，and low electroacoustic conversion efficiencies，are not suitable for high-performance ultrasound transducer applications. In this study，the finite-element simulation method is used to design a musculoskeletal ultrasound array transducer based on 1-3 piezoelectric composites. The influence of the element’s area on its impedance and that of its aperture on the acoustic pressure distribution of the transducer are investigated. Finally，a physical transducer element based on the 1-3 piezoelectric composite is fabricated and tested. Test results demonstrate that the −6 dB bandwidth and central frequency of the element designed in this study are 18% and approximately 0.8 MHz higher than those for a PZT-5H transducer element having the same specifications，respectively.

Resonant pressure sensors are characterized by high accuracy and strong impact resistance；however，their stability and ability to respond rapidly to external pressure variations remain challenging. This study investigated electrostatic excitation/piezoresistive detection resonant pressure sensors and developed a nonlinear closed-loop self-excitation system model based on automatic gain control（AGC）technology. The open-loop transfer function of the system was derived，and the dominant poles were determined using the resonator parameters and secondary poles governed by the low-pass filter parameters within the AGC loop. To reconcile the conflicting requirements of the low-pass filter design，loop stability，and system startup speed for the secondary poles，we propose a multi-path feedforward compensation technique. This innovation reduces the system stabilization time to 150 ms while eliminating the overshoot in both the excitation waveform and the phase shifter’s output waveform during system startup. The proposed approach significantly enhances system stability，and the experimental results demonstrated a measurement accuracy exceeding 0.03% FS.

In recent years，the widespread use of drones in various fields has introduced new security risks，making the monitoring and detection of drone activities crucial. This paper proposes a UAV acoustic detection and recognition method based on the mel spectrogram and time-frequency attention and soft thresholding convolutional neural network for detecting and classifying UAV audio from various environmental noises. This method converts UAV audio data into mel spectrograms and inputs them into the neural network model. The model automatically learns and identifies important time and frequency regions in the mel spectrogram through the attention mechanisms of time and frequency and assigns higher attention weights to them to improve recognition accuracy. Combined with soft thresholding，it suppresses the influence of environmental noise and outliers on the model and improves its classification and recognition performance under various environmental noise interferences. In this study，we collected an 8-category audio dataset for drones and enhanced it using background noise. We evaluated existing methods using this dataset. The results demonstrated that the proposed method is superior to existing methods in terms of accuracy，precision，recall，and F1-score.