Aiming at the problems of weak distinctiveness and low diagnostic accuracy of permanent magnet synchronous motor (PMSM) demagnetization faults, a local demagnetization fault diagnosis method for PMSM based on Improved Empirical Wavelet Transform (IEWT) combined with Sparrow Search Algorithm (SSA) optimized Extreme Learning Machine (ELM) is proposed. Taking the radial leakage magnetic signal on the motor surface as the research object, the leakage magnetic experimental data under 15 different demagnetization states are extracted. To solve the problem of unreasonable spectrum segmentation in the EWT method, an adaptive decomposition with improved frequency band division is performed according to the special spectrum trend of PMSM leakage magnetic signals. Then, the normalized energy values of each intrinsic mode function (IMF) are calculated to form the corresponding feature vectors, which are input into the ELM model optimized by the SSA algorithm for demagnetization state identification. Experimental results show that the method based on IEWT-SSA-ELM has a significant improvement in fault identification effect compared with the unimproved and unoptimized methods.

This paper presents a compact substrate-integrated waveguide (SIW) bandpass filter featuring a simple structure and transmission zeros. The proposed filter utilizes a quarter-wavelength transmission line in conjunction with a short-circuited and open-circuited via structure to achieve a third-order bandpass filter response. The filter achieves a passband from 14.15 GHz to 15.86 GHz with a return loss (|S₁₁|) better than -10 dB, indicating good impedance matching. To enhance out-of-band rejection, single- and double-slot structures are introduced along the quarter-wavelength transmission line of the SIW filter without increasing the overall circuit area. The SIW filter using the single-slot structure generates a transmission zero at 16.5 GHz, albeit with limited suppression. In contrast, the SIW filter using the double-slot structure introduces a deeper transmission zero at the same frequency, substantially improving stopband attenuation while maintaining excellent passband performance. The proposed filter offers high selectivity, compact size, and structural simplicity, making it a strong candidate for high-frequency communication and radar system applications. To validate the design, prototypes of the SIW bandpass filter, including the prototype version, single-slot version, and double-slot version, were fabricated and measured. The measurement results show good agreement with the simulation results.

In this investigation, a broad circularly polarized high-gain SADEA-tuned quasi-TM30-mode excited metasurface antenna at sub-6 GHz 5G band is shown. A linearly polarized (LP) monopole antenna in stage-1 with conventional partial ground is proposed. Then, in stage-2, a stair-cased partial ground plane is transformed to witness circular polarization (CP), an expanded part of stage-1. In stage-3 for next-generation wireless applications, the main objective is to improve the CP gain, impedance (10-dB BW), and axial bandwidths (3-dB BW), which will make it a good candidate for RF energy harvesting systems, a potential feature for next-generation wireless application. In this case, the application of a metasurface layer is an important step, significantly optimized by using AI-tuned SADEA method. The SADEA-tuned metasurface layer at 45 mm right above the λ/4 monopole radiator is integrated as a multi-layered structure. Finally, it is fabricated on a low-cost FR-4 substrate with thickness of 1.6 mm and offers a measured 116.3% 10-dB BW, 20.98% 3-dB BW, CP gain peak > 7.5 dBic, and antenna efficiency > 85% in the desired band of operation. With the introduction of SADEA optimization method not only the complexity was reduced while designing the metasurface layer, but simultaneously to the best of author’s knowledge, this is the first time such type of approach is followed towards the design of circularly polarized metasurface antenna for next-generation wireless applications.

This study addresses the challenge of detecting Autism Spectrum Disorder (ASD) in children, where clinical diagnostic scales used in practice suffer from subjectivity and high costs. Eye tracking (ET), as a non-contact sensing technology, offers the potential for objective ASD recognition. However, existing studies often use specially crafted visual stimuli, making them less reproducible, or rely on the construction of handcrafted features. Deep learning methods allow us to build more efficient models, but only a few studies simultaneously focused on visual behaviors of ASD in both temporal and spatial dimensions, and many studies compressed the temporal dimension, potentially losing valuable information. To address these limitations, this study employed a relatively lenient visual stimulus selection criterion to collect ET data of ASD in social scenes, enabling analyses to be conducted both temporally and spatially. Findings indicate that the spatial attention distribution of ASD is more dispersed, and gaze trajectories are more unstable in the temporal dimension. We also observed that children with ASD exhibit slower responses in gaze-following scenarios. Additionally, data loss emerges as an effective feature for ASD identification. We proposed an SP-Inception-Transformer network based on CNN and Transformer encoder architecture, which can simultaneously learn temporal and spatial features. It utilized raw eye-tracking data to prevent information loss, and employed Inception and Embedding to enhance the performance. Compared to benchmark methods, our model demonstrated superior results in accuracy (0.886), AUC (0.8972), recall (0.82), precision (0.95), and F1 score (0.8719).

In this paper, a novel compact dual open-sleeve multiband monopole omnidirectional antenna specifically designed for coal mine communication is proposed. Its core innovation lies in the structural optimization that enables multiband operation across a wide frequency range. To adapt to the confined mine tunnel environment, the antenna employs an ultra-small diameter design, which poses significant challenges for impedance matching below 1 GHz. Additionally, the substantial electrical size disparity between the sub-1 GHz and above-5 GHz bands further complicates multiband matching. The proposed open-sleeve monopole antenna consists of top and bottom dual open-sleeve structures along with resistive loads. Four length-adjustable thin copper columns replace the conventional sleeve, forming an open-sleeve structure. Through coordinated tuning of the two longest columns in the bottom open-sleeve structure together with the resistor loads, the antenna achieves favorable impedance matching in the low-frequency band (0.515-0.845 GHz). Furthermore, by adjusting the dimensions of the second-longest and shortest columns in the bottom open-sleeve, the antenna covers the 1.370-1.485 GHz and 4.660-6.000 GHz bands, respectively, while tuning the central monopole enables matching in the 2.210-2.525 GHz band. Ultimately, through independent adjustment of the four bottom column lengths and coordinated optimization of the resistor loads, the antenna effectively operates in four bands: 0.515-0.845 GHz, 1.370-1.485 GHz, 2.210-2.525 GHz, and 4.660-6.000 GHz, with the ratio between the lowest and highest operating frequencies reaching 10:1. Simultaneously, the top open-sleeve structure enhances the antenna's gain in the low-frequency band. Measured results show good agreement with simulation, demonstrating a gain of 1.21-4.59 dBi and radiation efficiency of 44%-77.7%. Moreover, the antenna exhibits omnidirectional radiation characteristics. This antenna shows potential for coal mine communication applications and also supports WLAN (2.4/5.2/5.8 GHz), WiMAX (2.3/5.8 GHz), and 5G NR (n5/n12/n28/n71/n79).

During the vehicle parking process, misalignment between transmitting and receiving coils caused by different parking positions results in variations in the system's mutual inductance. These variations compromise system performance and stability. To address this challenge, this study proposes a control strategy for a wireless power transfer system utilizing switched inductors. First, an efficiency optimization method based on tunable inductors is introduced in detail. This method eliminates the need for bilateral communication or additional hardware. By dynamically adjusting the switched inductor values, the system maintains optimal load conditions across various topologies. Furthermore, switched capacitors are employed to achieve system resonance tuning. Second, a phase-shift control strategy is implemented to ensure efficient system operation while maintaining constant voltage output. Finally, an experimental prototype is constructed to validate the proposed approach. Experimental results demonstrate that the proposed control method achieves a constant output voltage of 24 V with system efficiency exceeding 81%.

This article proposes a novel polarization-reconfigurable metasurface converter with multi-functional operation capabilities for flexible polarization manipulation of electromagnetic waves. By integrating PIN diodes into a strategically designed unit cell, the converter achieves dynamic switching among all fundamental polarization conversion modes, including linear-to-linear (co- and cross-polarization), circular-to-circular (co- and cross-polarization), linear to circular polarization (LP-CP), and circular to linear polarization (CP-LP) conversions under both linearly and circularly polarized incidence. When the diodes are switched ON, the structure performs linear-to-cross-linear polarization conversion in the 9.5-16.4 GHz band and circular-to-co-circular polarization conversion in the 9.3-16.6 GHz band. Dual-band LP-CP and CP-LP conversions are attained in the 8.0-9.3/16.6-17.7 GHz and 8.1-9.4/16.8-17.9 GHz bands, respectively. When the diodes are OFF, the converter maintains co-polarized reflection under linearly polarized (LP) wave incidence, while reversing the handedness of the incident circularly polarized (CP) wave. Both full-wave simulations and experimental measurements demonstrate consistent performance across a broad bandwidth. This work provides a versatile and efficient solution for modern wireless communication and radar systems requiring adaptive polarization control.

To enhance the disturbance rejection capability and robust stability of PMSM under time-varying disturbances, an improved super-twisting higher-order sliding mode active disturbance rejection cascade control strategy is proposed. Firstly, a second-order mathematical model of the PMSM speed-current dual-loop system is established. Secondly, to address the oscillation issues caused by differentiation of the reference speed in conventional linear error feedback control, a composite sliding mode error feedback control law is designed by integrating the fast super-twisting (FST) algorithm and the fast non-singular terminal sliding mode control (FNFTSMC) method. The control law effectively suppresses system chattering and improves dynamic response. Meanwhile, an improved extended state observer (IESO) is constructed based on deviation control theory, which enhances real-time compensation of the cascade controller by optimizing convergence speed and disturbance estimation accuracy. Finally, hardware-in-the-loop (HIL) simulation results on an RT-LAB platform demonstrate that the proposed method outperforms traditional strategies in both dynamic performance and disturbance rejection, providing a viable solution for high-performance PMSM drive applications.

The prospective applications of a rectangular microstrip patch antenna (MPA) in energy harvesting at radio frequencies (EH). The study aims to develop a rectenna that can detect and connect low power wireless devices to long-term evolution (LTE) networks by capturing low-power radio frequency (RF) signals radiated by cell towers, since the Kappa 438 antenna substrate with relative permittivity 4.25 has high 9 dB gain and 83% of measured efficiency. For the 2.5 GHz LTE band, stubs technology is being used for impedance matching and to decrease the overall rectenna size. The captured RF signals were altered into a usable DC voltage via a rectifier circuit in the manufactured rectenna, having the option of storing the voltage in a battery or utilizing it to power wearable, portable Internet of Things (IoT) systems and wireless sensors. The rectifier circuit is reduced in size by utilizing the SMD-Schottky diode type SMS7630 segments approach, further reducing the complexity and bulk of the rectenna. The rectenna obtains an efficiency of 88% when the RF input power is tuned to 0 dBm, while the maximum output DC voltage generated is 1.7 V when the radio waves power supply is 10 dBm. The rectenna with high gain and directivity has the capability to operate in low power environments, capturing weak radio frequency signals and working across -10 to 10 dBm power dynamic range. power dynamic range. These outcomes represent new contribution to our work which is relevant to other studies listed in Table 6 and demonstrated notable improvements.

In this paper, a miniaturized balanced bandpass filter characterized by biaxial symmetry is designed and implemented using four C-section parallel-coupled microstrip lines. As two orthogonal symmetric axes are inherently embedded across the filter layout, a natural geometric constraint is imposed and therefore furnishes two independent input/output port states. Owing to its symmetric topology, the developed filter replicates the same differential- and common-mode responses at each of its two independent input/output port pairs. To further enhance the common-mode suppression without compromising the differential-mode performance, a quarter-wavelength open-circuited stub is introduced onto the junction of one of the C-section parallel-coupled microstrip lines. By utilizing this stub, the common-mode suppression bandwidth is effectively broadened. Moreover, highly compact circuit sizes are achieved for the developed balanced filters, which is regarded as essential for their integration into modern miniaturized microwave communication systems. Finally, the feasibility of the proposed concept is verified through the design and fabrication of two prototypes, and good agreement is observed between the simulated and measured results.

The advancement of wireless communication has led to continuous innovation in antenna technology to satisfy the growing requirement for wireless communication. However, in wireless communication, antennas still face problems and challenges such as high power consumption and low adaptability. To address these issues, this study introduces magneto electric dipoles to optimize broadband millimeter wave patch antennas and uses metasurface optimization patches to ultimately design broadband dual-polarized millimeter wave metasurface antennas. In comparative tests at different temperatures, the gain of the broadband dual-polarization millimeter-wave meta-surface antenna reached a peak of 10.7 dBi at around 35 GHz at -50 ℃. At 0 ℃ and 50 ℃, the gain reached a peak of 10.2 dBi and 8.5 dBi, respectively. The result shows that the designed antenna has high accuracy, gain, and strong stability in wireless communication, and also has certain anti-interference ability in different environments.

This paper presents a design method for circularly polarized metasurface antennas by integrating waveguide-fed metasurfaces with optical holography principles. Two interleaved linear slot elements on the metasurface top layer are excited by a reference wave from the feed, generating a circularly polarized beam. Simply adjusting the position of each slot element steers the beam in the desired direction. To enhance gain, metal vias are added around the antenna perimeter, reducing reference wave leakage. To validate this method, two 24 GHz circularly polarized holographic metasurfaces were simulated and experimentally characterized. Measurements show a 1.23 dB gain enhancement in the metasurface antenna with metal vias. Simulated and measured results validate the antenna's performance. This approach yields compact, low-profile antennas without requiring a separate feed network. Furthermore, the structure can be extended to create reconfigurable circularly polarized antennas, demonstrating significant potential in this field.

This research introduces a compact and highly selective tri-coupled line microstrip bandpass filter. The design features a narrow capacitive gap positioned at the midline to disrupt symmetry and facilitate bandpass functionality, as predicted through an even- and odd-mode image impedance framework. The split at the midline generates two modal capacitances (C_gg, C_gb), which influence Re (Z_i) and, in conjunction with geometric coupling, determine the passband and roll-off characteristics. Closed-form relationships for microstrip design are utilized to compute line widths and electrical lengths. A systematic parametric analysis demonstrates how the gap and interline spacing impact the fractional bandwidth and the steepness of the transition. Additionally, a substrate survey across dielectric constants ranging from 2 to 12.2 quantifies the trade-off between footprint and selectivity, indicating an area reduction of up to approximately 86% at higher dielectric constants. The selectivity is further enhanced by incorporating auxiliary shunt open stubs that introduce transmission zeros near the edges without necessitating additional resonator sections. A prototype fabricated on an FR-4 substrate operating at 2.4 GHz confirms the theoretical model: the measured |S₂₁| exhibits an insertion loss of approximately 0.58 dB, a fractional bandwidth at 3 dB of approximately 37.3%, a shape factor of 1.3, and two prominent TZs near 1.7 GHz and 3.1 GHz with rejection levels of 48-52 dB. Furthermore, the upper stopband maintains |S₂₁| < -35 dB within the frequency range of 3.10 to 3.20 GHz. These findings substantiate that a single TCL section, featuring a central gap and open stubs, can achieve sharp roll-off and low insertion loss while maintaining minimal layout complexity and enabling straightforward tuning on low-cost printed circuit board materials.

As wireless communication technologies evolve, the demand for more efficient and compact antennas has escalated. Fractal antennas, with their unique self-similar design, offer a promising solution to meet these needs. Traditional antenna designs often face limitations in bandwidth and efficiency, especially in complex environments like urban areas, where high-performance antennas are crucial. This paper proposed a novel star-fractal patch integrated with a Sierpinski triangle fractal defective ground structure. This combination creates a double fractal design, which is further enhanced by adding a rectangular split ring resonator (R-SRR) array as a metasurface superstrate to achieve a reasonable bandwidth with improved gain for C-band wireless applications. This novel antenna structure results in improved impedance matching within the 5.22 GHz to 5.78 GHz operating frequency range. Electromagnetic simulations and anechoic chamber measurements validate the performance parameters of the proposed antenna. A proposed compact fabricated antenna achieved a bandwidth of 10.24% with noteworthy improvements in directivity across the operating frequency range compared to a full ground structure. The measured results align closely with the simulated data, demonstrating the reliability of the design approach. The fractal antenna design demonstrated substantial enhancements in performance parameters, confirming its viability as a superior alternative to conventional antenna designs in enhancing wireless network capabilities. These advancements could enable next-gen wireless and IoT applications by solving challenges in miniaturization, integration, and multi-band operation. Future research aims to enhance capabilities with dynamic reconfigurability, wider and selective frequency coverage of metamaterial inspired fractal antennas.

A compact wideband circularly polarized radio frequency identification (RFID) reader antenna with a coupling inner ring is proposed. The antenna consists of a radiating patch, a feeding network, and vertical fences along the sidewalls. The radiating patch incorporates both an outer ring and a coupling inner ring, which significantly broadens the gain bandwidth. Meanwhile, the sidewall-loaded vertical fences effectively extend the surface current path, enabling directional radiation. The overall antenna size is 100 mm × 100 mm × 24.6 mm. Measured results show a -10 dB impedance bandwidth of 663-1191 MHz, a 3 dB axial ratio bandwidth of 710-1085 MHz, a 4.5 dBic gain bandwidth of 885-1150 MHz and a maximum gain of 6.36 dBic. Featuring a compact structure, wide impedance bandwidth, broad axial ratio bandwidth, and enhanced gain performance, the proposed antenna is well suited for ultra high frequency (UHF) RFID applications, particularly in space-constrained environments or in scenarios where tag antennas are susceptible to frequency deviations.

A four-port cross-shaped RDRA multiple-input-multiple-output antenna is proposed for 5G millimeter-wave applications. The present investigation targeted the 5G n257 band (26.5-29.5 GHz) with resonance exactly at 28.5 GHz. The proposed DR MIMO antenna is constructed over roger RT duroid 5880 laminates with the floor area 10.4×10.4×0.254 mm³ with the compact DRA of dimension 7.6×7.6×1.5 mm³. Each element of the DRA is fed by conformal fed microstrip line that generates TE_21∂, TE_41∂, TE_11∂, TM_14∂ and TM_41∂ modes. The symmetricity of the structure is maintained by locating four arms of the DRA at a separation of 90°, that generates omnidirectional radiation pattern and offers good radiation diversity. The proposed antenna offers 14% impedance bandwidth with below -15 dB isolation. Following the thorough simulation procedure, it has been verified that the compact MIMO DRA operates exactly at 28.5 GHz. To validate design, a four-port single element DRA operating at 28.5 GHz was simulated in CST studio suite, fabricated via ceramic material and then measured in anechoic chamber. The proposed antenna shows the peak gain of 8.4 dBi with 74% radiation efficiency. Both simulation and measurement observations are used to examine the MIMO parameters. The Envelope correlation coefficient is reported as 0.0125 and Diversity gain is reported as 9.8 in approximately all the cases. The Total Active Reflection Coefficient is found to be 18% at 28.5 GHz in measurement and 18.5% at 28.5 GHz in simulation.

Ultrashort pulse semiconductor lasers represent a groundbreaking advancement in photonics by simultaneously overcoming the fundamental constraints of temporal duration, spatial confinement, and energy efficiency. These triple breakthroughs enable unprecedented applications in ultrafast spectroscopy, high-density optical storage, optical atomic clocks, photonic computing, and minimally invasive biomedicine, establishing a new paradigm for precision light-matter interaction in both scientific and industrial domains. This paper analyzes the principle and cutting-edge research progress of ultrashort pulse semiconductor lasers, discusses the implementation difficulties and optimization methods in integrated design, and looks forward to the challenges and future development trends.

This paper presents a reconfigurable multilayer graphene antenna for terahertz sensing, machine learning-based frequency and bandwidth estimation. The antenna utilizes the tunable electromagnetic properties of graphene, enabling dynamic reconfiguration of the resonant frequency and bandwidth. By adjusting key physical parameters including chemical potential, relaxation time, and temperatur, the antenna achieves frequency tuning from 1.542 THz to 1.562 THz, with an improved return loss reaching -30.8 dB and a bandwidth range from 91 GHz to 96 GHz. Furthermore, the resonance frequency and bandwidth are predicted using machine learning algorithms, including Random Forest and XGBoost, with results that closely match simulation data. These results highlight the potential of the proposed structure not only for adaptive communication systems but also for terahertz sensing platforms requiring frequency agility and environmental responsiveness.

The annular micro receiving coil (RC) holds promise in the wireless power supply for capsule endoscopy (CE). The equivalent series resistance (R_SR) of the RC plays a critical role in energy transmission efficiency. Calculating the R_SR is challenging because RC typically incorporates an embedded magnetic core. To overcome this challenge, this paper employs Dowell's method and the Bessel's method respectively to calculate R_SR. The analyzed RC consists of an annular core with two grooves and dual windings positioned within the grooves. The influence of the magnetic core on the R_SR is equivalently considered through the winding skin effect and core losses. We compared the simulated, calculated, and measured values of the R_SR, and found that: the error of Dowell's method becomes smaller when the groove spacing D_g > 4 mm, but fails to capture the influence of D_g on the R_SR. Conversely, Bessel's method effectively captures the influence of D_g but exhibits larger errors (2.09%~26.52%). Based on this finding, we propose a novel Bessel-modified Dowell's (BMD) method by integrating the framework of Dowell's method with a proximity-effect correction term from Bessel's method, which reduces the maximum calculation error to within 13.72%, facilitating rapid optimization of annular coils with embedded magnetic cores.

This paper proposes a fast voltage regulation control method based on direct power calculation. To suppress the issues of long bus voltage recovery time and large voltage fluctuation in dual three-phase permanent magnet generator, firstly, in the voltage outer loop, the fast adjusting component of the inner loop power reference is derived through a direct power calculation method. This approach enhances the dynamic response of the bus voltage. Secondly, to mitigate control errors induced by system losses, a capacitor power compensation method is introduced to generate an error compensation component for the power reference, thereby improving the voltage control accuracy. Finally, the feasibility and effectiveness of the proposed control strategy are validated through both software simulations and experimental tests. In comparison with conventional methods, the proposed strategy provides stronger disturbance rejection and a faster dynamic response, enabling high-performance DC bus voltage control for dual three-phase permanent magnet generator systems.