Surface acoustic wave filters with extremely narrow bandwidth are urgently needed for use in security communication systems. The working frequency of the surface acoustic wave filter will drift significantly at extremely high or low ambient temperatures, which makes it hard for the filter to effectively extract useful signals and suppress noise in the near-passband. This study simulated and analyzed the frequency-temperature characteristics of extremely narrow bandwidth surface acoustic wave filter based on a quartz substrate and studied the effects of metal thickness and the metallization ratio of electrodes on the inflection point of the secondorder temperature characteristic of the device. An extremely narrow bandwidth surface acoustic wave filter with low frequency drift was finally manufactured by optimizing the structural parameters.

A one-dimensional Mason model was used to study the effect of the piezoelectric layer and electrode thickness ratio on the effective electromechanical coupling coefficients of FBAR resonators. As the proportion of piezoelectric layer thickness increases, the effective electromechanical coupling coefficient of the resonator gradually increases. A high-frequency FBAR resonator was developed via film thickness optimization and chip fabrication. Based on adopting trapezoidal circuit structures, the effects of the stages of the filter, ratio of static capacitance in series and parallel resonators, and series inductance of parallel resonators on the suppression of filter stopband were studied. Through chip fabrication, an FBAR filter chip with a center frequency of 4.4 GHz, minimum passband loss of 2.3 dB, -1 dB bandwidth of 112 MHz, and near end out of band suppression of better than 50 dBc on both sides of the passband was prepared, thus providing a reference for the development of high-frequency and high-suppression FBAR filters.

To enhance the sensitivity in the low-frequency range, a slotted low-frequency high-sensitivity microelectromechanical systems (MEMS) acoustic sensor structure was designed based on scandium aluminum nitride (ScAlN) piezoelectric films. The influence of the number of slots on the resonant frequency and voltage output was analyzed. A MEMS acoustic receiver with a resonant frequency of 29.3 kHz was fabricated. The highest sensitivity measured within the frequency range of 20-30 kHz exceeded -60 dB, indicating that the slotted structure proposed in this paper could achieve high sensitivity in the low-frequency range.

A dual-passband filter with a notch is proposed. The transmission characteristics of the filter are also analyzed using the odd-even mode theory. The filter is composed of an inverted resonator, a T-resonator, and an input and output parallel feeder. A step impedance (SIR) is loaded on the branches of the inverted resonator to suppress the second harmonic of the first passband. Through the overall simulation of the filter and the optimization of its notch frequency and depth, the final notch is located at 1.8 and 6.7 GHz, and the depth can reach less than-19 dB. Finally, the dual-passband filter was processed and tested. The two passbands are 1.44-2.4 and 5.4-7.4 GHz. The insertion loss in the passband is -1.16 and -1.6 dB, and the maximum isolation between the passbands is 50 dB. The measured results agreed well with the simulated results, thus verifying the feasibility of the structure and design method proposed in this study.

In response to miniaturization, low-cost, and integrated transmit/receive (T/R) module demands, a millimeter-wave frontend module operating in the frequency range of 30-40 GHz was studied. A high-temperature co-fired ceramic (HTCC) substrate and ball grid array (BGA) packaging were adopted to achieve high-density integration of four transceiver channels for functions such as signal amplification, power distribution, and amplitude-phase control. Through the simulation and optimization of the vertical interconnection structure of the millimeter-wave signal in this module, low-loss signal transmission of this structure in the millimeter-wave frequency band was realized. Moreover, a printed circuit board (PCB) was designed and fabricated to test and verify this vertical interconnection structure. After calculations, the maximum insertion loss of the vertical interconnection structure was 0.78 dB. Using this vertical interconnection structure for millimeter-wave signals, a Ka-band four-channel millimeter-wave frontend module was fabricated. The test results show that in the frequency range of 30-40 GHz, the single-channel transmission power of this module was greater than 20 dBm; the receiving gain was greater than 21.33 dB; and the voltage standing wave ratio was better than 1.51, fulfilling the application requirements of the radio-frequency system.

To address the broadband coverage challenges in the mid-band of 5G in China and to enable future applications of 6G systems in the sub-7 GHz frequency range, this paper presents the design of a coplanar waveguide (CPW)-fed ultra-wideband, high-isolation multiple-input multiple-output (MIMO) antenna that covers the 5G frequency bands. The antenna element is based on a single elliptical patch, and ultra-wideband performance is achieved by incorporating a trident-shaped structure and cornercutting techniques. The antenna consists of two slot antenna elements, suitable for a 2×2 MIMO antenna array configuration, with overall dimensions of 118×66×0.8 mm. The two antenna elements are arranged in a parallel configuration, with their ground planes interconnected. Additionally, an “H”-shaped fence structure is introduced between the elements to improve isolation. Experimental results showed that the antenna can operate across a bandwidth of 1.15-7.80 GHz, with isolation greater than 20 dB across the operating band. The envelope correlation coefficient (ECC) was below 0.03, and the diversity gain (DG) exceeded 9.98 dB. The designed MIMO antenna features high isolation and ultra-wideband coverage, and the CPW feeding structure facilitates its integration into integrated circuits and various ultra-wideband systems. This antenna showed promising application potential in both current 5G and future 6G systems.

Within a context of commercialization of 5G communication technology and rapid development of satellite communication and technological innovation, this paper presents a three-band binary MIMO antenna based on an “X”-shaped isolation structure. The antenna consists of two inverted, parallel unit radiating patches, with isolation enhanced by loading isolation branches on both the front and back sides. A slotting technique was applied on the back of the antenna to improve bandwidth. The overall dimensions of the antenna are 37 mm×25 mm×0.8 mm, and its measured operating bands are 4.3-5.8 GHz, 8.02-9.3 GHz, and 12.2-14.8 GHz. The port isolation exceeds 23 dB within the operating range, while the full-band envelope correlation coefficient (ECC) remains below 0.03, and the diversity gain (DG) exceeds 9.99 dB, indicating excellent diversity performance. These results demonstrate that the antenna meets MIMO-antenna transmission performance requirements and is well-suited for 5G and satellite communication systems.

This study examined the influence of the chlorine-based inductively-coupled plasma (ICP) dry etch system on Mo sidewall profile and etch rate. A sidewall angle of 14.8° to 85.0° was achieved by changing the radiofrequency (RF) and ICP power, chamber pressure, and mixed gas flow ratio during the ICP dry etching process. The experiment results show that the Mo sidewall profile can be controlled over a wide range, and the etching rate can be adjusted between 148 and 232 nm/min. Therefore, this study provides a helpful process guideline for fabricating thin-film bulk acoustic resonator (FBAR) devices.

With the miniaturization and increasing frequency of pressure sensors, it has become critical to develop low-cost manufacturing processes. By studying the effect of different concentrations of TMAH on wafer corrosion, the optimal process conditions were determined to be 80 ℃ with 25 wt% TMAH, achieving a low roughness surface of 0.121 m. Finite element simulations indicate that the sensitivity under 25 wt% wet etching conditions (103.276 mV/MPa) is closer to the design value of sensitivity (100 mV/MPa) than that under 5 wt% TMAH wet etching (109.162 mV/MPa). An efficient wet etching process is summarized, based on which a pressure sensor manufacturing process was designed. This approach is expected to produce sensors that more closely meet design requirements at a lower cost.

To ensure the effective detection of metal conductive objects, the end face of the transducer was machined mechanically to remove part of the shell and form a 0.10 mm insulating step. Finite element simulation using ANSYS/LS-DYNA revealed that the stress on the ceramic plate during radial cutting was 56.35 MPa, significantly lower than that encountered during axial cutting, which reached 216.25 MPa. Furthermore, both stress and deformation of the ceramic plate in the piecewise superimposed cutting process were markedly reduced. By combining theoretical analysis and cutting experiments, a three-time superimposed radial feed process was developed, and the removal method of metal residual burrs was optimized, addressing the frequent damage to the matching and transmitting end face of the transducer and delamination with piezoelectric ceramics during the cutting process. The results of this study have great significance for the application and promotion of piezoelectric ultrasonic transducers.

To address the challenge of focusing small-diameter microorganisms, such as bacteria and yeast, in flow cytometry, we conducted a study on microfluidic chips for microorganism focusing. A novel square channel was developed based on traditional straight-channel designs. A finite element model of the square-channel microfluidic chip was established to enable the optimization of structural parameters, including the channel width and length, through finite element simulations of fluid flow and particle trajectories. The simulation showed that when the channel width was 20 m, and the unit length was 80 m, particles were focused within 63% of the channel. A silicon-based substrate was used to fabricate the square-channel microfluidic chip, and a prototype flow cytometer was constructed to test it. The experimental results indicate that with a total channel length of approximately 2.16 cm, the actual focusing range for yeast cells reached 70%, thus satisfying the design requirements for yeast focusing.

Nd-doped BiScO3-PbTiO3 (BSPT) high-temperature piezoelectric ceramics were prepared using a conventional solid-phase reaction method. Regarding the determination of the morphotropic phase boundary of BSPT, the effects of Nd doping on its structure and properties were systematically investigated. The results show that the phase structure and domain structure of BSPT ceramics can be regulated by Nd doping, which can effectively improve its piezoelectric properties and temperature stability. When the doped BS content is 37 mol%, and the Nd doping concentration is 3.0 mol%, it has the best piezoelectric properties, with a piezoelectric constant d33 of 620 pC/N, Curie temperature of approximately 405 ℃, and good temperature stability.

To prepare high-performance SiO2 thermal compensation layers for temperature-compensated surface acoustic wave (TC-SAW), SiO2 thin films were prepared using electron beam evaporation coating and reactive magnetron sputtering. The effects of the two preparation processes on the density, surface roughness, and elastic modulus of SiO2 thin films were studied. The morphology and crystal structure of SiO2 films were analyzed using scanning electron microscopy, atomic force microscopy, and X-ray diffraction. The refractive index and thickness changes of the thin film after corrosion were measured using an ellipsometer and the hardness and elastic modulus of the thin film were calculated using a nano-tracer. The results show that SiO2 prepared by reactive magnetron sputtering has a denser film, lower surface roughness, and higher elastic modulus. A TC-SAW device with a frequency temperature coefficient of -8.6×10-6/℃ was obtained using a SiO2 thin film prepared by reactive magnetron sputtering.

As communication devices continue to advance toward greater portability and slimmer designs, the demand for smaller, high-performance surface acoustic wave (SAW) chips has consistently increased. To ensure product quality, implementing effective quality control and reliability testing throughout the chip development and manufacturing processes is essential. An analysis of the failure modes and effects of SAW chips identifies potential risks during both the design and production stages. Based on these findings, appropriate quality control measures were established, and reliability testing methods were developed to improve the chip yield. The effectiveness of these quality control and reliability testing methods has been validated, offering valuable insights for the industry.

In this paper, we propose a high-robustness, temperature-pressure integrated flexible sensor based on heat conduction and analyze its underlying mechanism. A three-dimensional model was established using COMSOL, and the temperature field in the structure was calculated. The results show that the input pressure is inversely proportional to the output voltage of the proposed sensor. The sensitivity is -0.205 mV/kPa in the range of 0-500 kPa with a nonlinearity of 6.161%. Likewise, the sensitivity is -4.937 mV/kPa in the range of 525-740 kPa with a nonlinearity of 9.628%. We describe the underlying mechanism of the sensor, providing a theoretical foundation for optimizing its parameters and structure.

Ce:GAGG scintillation crystal samples were irradiated using a 60Co radiation source at a dose rate of 3×105 Rad/h, and the total irradiation doses delivered to the samples were 106, 107, and 108 Rad. The effects of irradiation were investigated by measuring the transmittance, relative light output, energy resolution, and decay time of the Ce:GAGG scintillation crystal samples before and after irradiation. The experimental results showed that after irradiation at a dose of 108 Rad, the transmittance of the crystal remained unchanged in the 450-900 nm, and the lowest transmittance (8.9%) was detected at 320 nm. The light output of the crystal decreased by 1.47%, whereas the energy resolution deteriorated only slightly. The relative light output, energy resolution, and decay time of the crystal did not change significantly. These results confirm the high resistance of the crystal to -ray irradiation and demonstrate its broad application prospects in high-dose nuclear radiation detection.

To tackle the issues of long design cycles, high costs, and poor compatibility in radiofrequency (RF) system-in-package (SiP) modules, this paper presents a fast verification method for RF SiP module links. RF devices in the module are separately packed into different building blocks. These blocks are then assembled to form a verification link with the desired circuit functions. By testing this link, we can quickly check if the RF SiP module design meets the requirements. A high-frequency connection bridge crimping structure is designed for good inter-block connection. Test results, after de-embedding calculation, showed that within 18 GHz, the maximum insertion loss value was 1.34 dB. Building and testing the verification link of a dual-conversion RF SiP module demonstrated that the proposed method had low loss along with reconfigurable and reusable features. The rapid design of RF SiP modules is of great engineering importance.

The piezoelectric micro-machined ultrasonic transducer (PMUT) is an important sensor in the field of ultrasonic ranging. Moreover, enhancing the ranging performance of PMUT is significant for promoting its engineering applications. This study is based on the sound absorption and amplification characteristics of the Helmholtz resonant cavity and describes the design of a cavity structure that reduces sound wave absorption at the back of the PMUT, as well as a horn structure for forward sound amplification. Experimental results show that at a distance of 2 m, the PMUT integrated with the Helmholtz resonant cavity exhibits a significant increase in ultrasonic signal amplitude, reaching 321.13 mV, which is an increase of 90.5 mV (39.2%), compared with the conventional patch film cavity structure. Furthermore, the PMUT equipped with a horn featuring Helmholtz resonance characteristics measured a signal amplitude of 540.72 mV at the same distance, representing an increase of 162.41 mV (42.9%) compared with the PMUT without the horn. These results indicate that combining the PMUT with the acoustic characteristics of the Helmholtz resonant cavity is of great significance for enhancing the application of PMUT in the field of ultrasonic ranging.

As the core component of piezoelectric actuators, the piezoelectric performance of multilayer PZT ceramics is affected by the self-heating temperature. In addition, multilayer PZT ceramics are prone to failure under strong alternating voltage. This study investigates the factors affecting the self-heating temperature from the perspective of alternating voltage characteristics and multilayer structure of PZT ceramics. First, based on the scanning electron microscope cross-sectional structure morphology, a fine-structure simulation model of multilayer PZT ceramics was established. Then, a temperature measurement experimental platform was set up to conduct self-heating temperature measurements on the ceramic surface for validation. Finally, the effects of alternating voltage amplitude, frequency characteristics, piezoelectric layer thickness, and dead layer thickness on the self-heating temperature of the ceramic surface were analyzed. The results indicate that 1) the self-heating temperature of the ceramic surface increases linearly with the alternating voltage amplitude and frequency; 2) the extreme value of the self-heating temperature is distributed in the center and edge regions of the ceramic surface, and the difference in temperature is less than 3 ℃; 3) the thicker the piezoelectric layer is, the lower the self-heating temperature of the ceramic surface is; and 4) the self-heating temperature of the surface decreases with the thickness of the dead layer and reaches its minimum when the thickness of the dead layer is approximately 300 m. This study provides a theoretical basis and experimental foundation for regulating the self-heating temperature in multilayer PZT ceramics and supporting engineering applications.

The displacement output characteristics of a piezoelectric stack micropositioner under high-stiffness load were measured, revealing that the output displacement is notably lower than expected. This displacement initially increases and then decreases as preload increases. It was found that under high-stiffness load and low preload, the mechanical contact stiffness between the piezoelectric stack and the load is of the same order of magnitude as the stack stiffness. This reduces the effective stiffness of the driving end, leading to displacement loss. As preload increases, non-180° domain reorientation within the piezoelectric stack enhances the piezoelectric effect, and mechanical contact stiffness increases until it reaches its limit. However, at higher loads, the piezoelectric coefficient of the stack decreases rapidly owing to depolarization. Overall, the micropositioner exhibits significant displacement loss, with displacement reaching its peak at a specific preload owing to the combined influence of these two factors.

A novel 6-DOF parallel platform based on piezoelectric actuation is proposed. The mechanical structure of the platform is examined to analyze its kinematic problems, and the degrees of freedom of the platform are verified using a modified Grbler-Kutzbach formula. Based on the structural and motion characteristics of the platform, the kinematic analytical model is derived using the homogeneous transformation method. The specific motion results obtained from the kinematic model are compared with those derived using Adams simulation software to validate the accuracy of the kinematic model. This research provides a theoretical foundation for the design and future practical applications of similar piezoelectric parallel platforms.

To address the nonlinear modeling of piezoelectric bimorph actuators, a method is proposed based on the Hammerstein structure. This approach connects the linear dynamic and nonlinear static modules of the system in series, and a modeling and parameter identification method for piezoelectric bimorphs is introduced based on the Jiles-Atherton model. To verify the accuracy of the model, finite element simulations and experimental tests were conducted and compared. The static/dynamic comparison results indicated hysteresis nonlinearities of 18.1%, 17.9%, and 19.3% for the theoretical model, simulation, and experiments, respectively. Additionally, the average relative errors in the step response of simulations and experimental tests with respect to the theoretical model were 5.2% and 4.1%, highlighting the accuracy and effectiveness of the proposed modeling approach.

Lamb waves have potential applications in structural health monitoring; however, most studies on delamination damage are limited to delamination localization and accuracy improvement, and few studies on delamination size measurement exist. This study investigates the effects of the delamination defect size on Lamb waves of different wavelengths in carbon fiber composite panels. The interaction between the A0 mode of linear FM Lamb waves and different delamination sizes is investigated via finite element simulation, and the degree of perturbation is found to increase monotonically with the delamination size when the wavelength is larger than the delamination size and that the degree of perturbation is in an oscillatory state when the wavelength is smaller than the delamination size. Facilitated by this phenomenon, a method is proposed to detect delamination defects in carbon fiber boards. A signal with a larger wavelength is selected as the excitation, and the damage index is used to portray the degree of disturbance. Moreover, the damage index is integrated into the imaging algorithm so that the imaging results can reflect the delamination size information.

To improve the trajectory tracking performance of piezoelectric actuators (PEAs), this study proposes a Kolmogorov-Arnold network feedforward model predictive control (MPC-KAN) based on a gated recurrent unit (GRU) neural network (NN) prediction model. Unlike neural network inverse model control, this method uses GRU-NN forward modeling and adjusts the model predictive control (MPC) output based on the model prediction results. First, this study selects the training input features of GRU-NN based on a linearized model and trains the network. Then, to improve optimization performance and shorten optimization time, the sparrow search algorithm (SSA) was used as the MPC optimizer, and a Kolmogorov-Arnold network (KAN) was established to replace the SSA optimization. The effectiveness of this method has been verified on the PEA platform. Compared with traditional methods, the control accuracy has been improved by approximately 30%.

A differential ranging-based extended Kalman filter algorithm (DREKF) is proposed to address the limitations in positioning accuracy and weak stability of UWB systems caused by various errors in indoor environments. The algorithm improves the communication protocol of the UWB positioning system by introducing differential ranging, thus allowing the error model of each base station to be updated during each positioning instance to reduce ranging errors. The improved extended Kalman filter algorithm is applied to locate the tag and thereby enhance both positioning accuracy and stability. Experimental results show that the DREKF algorithm achieves a horizontal positioning accuracy of 3 cm in line-of-sight conditions and 4 cm in non-line-of-sight conditions. Compared with a traditional positioning algorithm, the proposed algorithm significantly improves positioning accuracy and stability, thus satisfying the requirements for high-precision indoor positioning.

Transfer alignment is the key technology for the low-cost micro-inertial navigation system implemented in precision-guided weapons, which relates to the combat effectiveness of the weapon system. This study investigated the transfer alignment method of a low-cost micro-inertial navigation system based on flight tests of an unmanned aerial vehicle (UAV) from TENGDUN Technology. First, an improved adaptive Kalman filter was proposed based on an analysis of the velocity and attitude matching method, whereby the lever effect and data delay were compensated online and estimated in real-time. Subsequently, the algorithm was flight-tested on the TENGDUN UAV platform. Compared with the traditional Kalman filter method, the improved algorithm effectively improved the performance of transfer alignment and aligned the accuracy of the heading angle to meet the requirements of 0.65° (1). Selective analysis was conducted to determine the reason for the reduction in course misalignment angle estimation precision under the transfer alignment mode of the S-shaped turning maneuver-assisted wing of the UAV. Finally, the low-cost micro-inertial navigation system transfer alignment method and performance were analyzed and evaluated comprehensively, based on which a practical solution suitable for actual combat was provided.

With the rapid advancement of the Internet of Things (IoT) and intelligent systems, the demand for energy-harvesting technologies in sensor networks is escalating. To address the challenges of significant feature divergence in multi-channel broadband piezoelectric energy signals and low energy extraction efficiency under weakly coupled conditions, this paper proposes a multi-channel parallel synchronized switch harvesting on inductor (MCP-SSHI) interface circuit. The circuit retains high modular scalability and structural simplicity while enabling the processing of multi-channel input voltages with arbitrary phase relationships (0-2). In test results on processing signals from six piezoelectric energy harvesters (PEH), the MCP-SSHI circuit efficiently extracted multi-channel electrical energy, with an energy extraction efficiency of as high as 79.96%, which was 3.24 times the power gain of traditional interface circuits.

Quartz crystal microbalance (QCM), a nanogram-level sensor, offers the advantages of high detection accuracy, wide humidity detection range, low cost, and simple fabrication method via the addition of humidity-sensitive materials in sensitive areas to detect humidity under gas phase conditions. To enhance the performance of hygroscopic materials and expand the applications of QCM-based humidity sensors, a QCM humidity sensor based on a chitosan (CS) substrate and polyvinylpyrrolidone (PVP) film-forming mechanism was constructed. The experimental results show that the response/recovery time of the sensor is 13 s/14 s, the sensitivity reaches 57.84 Hz/%RH in the detection range of 11%RH-97%RH, and the maximum frequency fluctuation is less than 10 Hz within 30 days in repeated experiments.

Existing distributed fiber-optic sensing systems often target only a single parameter, whereas in practice, when operating in complex environments, multiple sensing systems and technologies need to be integrated to monitor various parameters. Using the characteristics of phase-sensitive optical time-domain reflectometer (-OTDR) and Brillouin optical time-domain reflectometer (BOTDR), which are sensitive to different physical parameters, an integrated distributed fiber-optic sensing system was designed. By employing the concurrent detection of Rayleigh and Brillouin scattering signals, various parameters such as vibration, temperature, and strain can be effectively monitored using a singular sensing fiber under a unified modulation pulse. The system relies on the concurrent detection of Rayleigh and Brillouin scattering signals to enhance the spatial resolution of BOTDR while upholding the unaltered modulation of the integrated system pulse. The Brillouin scattering signal was analyzed based on the principle of pulse subdivision superposition, which breaks through the limitations of phonon lifetime and improves spatial resolution without changing the pulse width. The system was experimentally verified to achieve vibration localization with a spatial resolution of 10 m based on Rayleigh scattering at a sensing distance of 50 km. Introducing pulse subdivision superposition based on Brillouin scattering increased the spatial resolution to 1 m for detecting temperature and strain. The Brillouin frequency shifts displayed a highly linear correlation with the changes in temperature and strain, thereby realizing the monitoring of multiple covariates.