With the growth of demand for high-rate and high-quality wireless communication services, Unmanned Aerial Vehicle (UAV) communication technology has received a lot of attention. By deploying Reconfigurable Intelligent Surface (RIS) on the UAV, more users can be reached while effectively expanding the signal coverage. The rotational nature of the UAV also provides new degrees of freedom in the design of RIS-assisted millimeter-wave Multiple Input Multiple Output (MIMO) systems. In this paper, using the advantages of UAV and RIS technologies, Aerial Reconfigurable Intelligent Surface (ARIS) is introduced to assist the communication, and the millimeter-wave Vehicle to Infrastructure (V2I) communication scenario based on the ARIS-assisted multi-vehicle beam tracking problem. First, Zero Forcing (ZF) beamforming is employed at the base station to eliminate inter-vehicle interference. On this basis, the vehicle-side beam combining matrix, the RIS-side reflection beamforming matrix, along with the rotation angle of the ARIS, are jointly designed to maximize the number of vehicles and data rates, thereby providing high-quality communication for beam tracking studies. Secondly, an ARIS-assisted multi-vehicle beam tracking model is derived in a MIMO-based 3D communication scenario. Finally, an Extended Kalman Filter (EKF) algorithm based on the angular deviation correction mechanism is proposed to realize the beam tracking of multiple vehicles. Simulation results show that the proposed EKF algorithm can effectively reduce the beam tracking error in multi-vehicle communication scenarios with robust beam tracking capability under the joint design based on beam merging matrix, beamforming matrix and ARIS rotation angle.

This research delves into the intricate functionality of a fully planar double bow-tie antenna with orthogonal feeding and is innovatively constructed on a substrate-integrated cavity inspired by metamaterial designs. The architecture of the antenna includes Complementary Split Ring Resonators (CSRRs) and a double bow-tie patch, intricately etched onto the metal surfaces positioned on both the top and bottom of the substrate. The antenna is meticulously designed and fine-tuned for superior performance specifically in the K and Ka-band frequencies. The incorporation of the double bow-tie patch in this antenna configuration brings forth several advantageous attributes such as improved impedance matching, exceptional high gain and unidirectional radiation pattern. In a notable feature of this design, the antenna supports multiband operation which is achieved through the strategic integration of slots within the Substrate Integrated Waveguide (SIW) cavity, allowing the antenna to resonate at multiple frequencies. The antenna's superior performance and its ability to function effectively across multiple frequency bands have been rigorously validated through extensive simulation studies and thorough experimental testing.

This study proposes a space-efficient ultra-wideband (UWB) monopole antenna engineered for superior gain and performance. The innovative design, modeled and analyzed using HFSS software, involves etching the resonator onto one side of an affordable FR4 substrate. The manufactured antenna features an extended impedance bandwidth, achieved by incorporating ``E'' and ``inverted E'' shaped slots on the patch, an irregular hexagonal substrate structure, and a slotted partial ground plane. Covering a frequency range from 2.5 to 11.1 GHz, the patch achieves a maximum gain exceeding 7.9 dB and an efficiency of 98%. Parametric analyses based on numerical simulations evaluate the impact of design elements, such as slots on the resonator and ground plane, and cuts in the substrate. The excellent match between simulated and measured data verifies the antenna's performance across multi-band environments. The article concludes by introducing a second antenna, designed through the symmetrical integration of four prototypes of the suggested antenna. Mutual coupling between elements is reduced through the use of an orthogonal, four-directional staircase structure, and a defective ground is intentionally left unconnected. This new antenna covers an impedance spectrum from 2.42 to 12 GHz, with a gain of 12.77 dB, an efficiency of up to 98%, and a voltage standing wave ratio (VSWR) ranging between 1 and 2. Overall, the article emphasizes the design, optimization, and application of UWB antennas, highlighting their performance and suitability for various wireless communication scenarios.

This study suggests a coin-sized (10 × 8 × 0.64 mm³) millimetre-wave antenna that simultaneously resonates at 28 GHz and 38 GHz and is supported by a machine-learning surrogate for near-instant impedance evaluation. Realised on Rogers 6010 LM laminate (ε_r = 10.2), the radiator maintains |S₁₁| ≤ -10 dB across 26.5-29.9 GHz and 37.2-39.7 GHz while providing peak gains of 3.8 dBi and 4.1 dBi in the lower and upper bands, respectively. A design-of-experiments sweep, comprising 330 full-wave simulations, generated the training corpus for a random-forest regression model. The surrogate predicts frequency-resolved |S₁₁| with a mean-absolute error below 0.7 dB and coefficients of determination of 0.93 at 28 GHz and 0.84 at 38 GHz. The evaluation time is reduced from approximately 155 s per full-wave electromagnetic simulation to 0.1 s per surrogate query, enabling real-time design exploration. Eight-fold cross-validation confirms model stability, while feature-importance analysis identifies the geometric parameters most influential to dual-band matching. The learning-guided workflow therefore offers a fast and reliable alternative to exhaustive simulation, accelerating the optimisation of compact mmWave antennas for instrumentation, sensing, and future front-end modules.

RF signals are widely used in various applications, including radar systems, wireless communication systems, and telecommunications. Phase shifters allow tuning of the signal's phase, using digital and analog designs. This adjustment is essential for antenna beam steering and shaping, signal cancellation, and frequency synthesis in antenna arrays. Phase control is essential to improve the performance of wireless communication and radar systems by enhancing signal reception and transmission. This study examines different types of phase shifters, including a comparative analysis of different phase shifter topologies and technologies, highlighting advantages and limitations according to applications. In addition, this review includes a specific study on liquid metal phase shifters. Finally, the article outlines future research directions for liquid metal phase shifters: It is emphasized that there is a constant need for innovative design strategies to keep pace with the evolving wireless communications and radar fields. Therefore, this article can be a reference for the next milestones in RF phase shifter research.

This paper introduces a substrate-integrated waveguide (SIW)-fed broadband antenna array employing proximity-coupled radiating elements for automotive radar applications. The design integrates three key innovations: (1) a periodic staggered arrangement of hybrid rectangular-polygonal patches, (2) combined proximity coupling with reflective slot structures enabling simultaneous broadband impedance matching and sidelobe suppression, and (3) an optimized 8 × 28 planar configuration operating at 77-81 GHz. Measurements of the fabricated prototype demonstrate an 8.86% impedance bandwidth (75.2-82.2 GHz) with dual-beam radiation characteristics - achieving a narrow beam (±5.5°) for long-range detection and a wide beam (±30.4°) for medium-range scenarios. The antenna maintains sidelobe levels below -20 dB, peak gain exceeding 19.8 dBi, and gain fluctuation within 1 dB across the operational band. Notably, the hybrid patch geometry and slot-loading technique yield a flattened radiation pattern with suppressed sidelobes, outperforming conventional mmWave arrays in radiation stability. The compact architecture demonstrates strong potential for next-generation automotive radars requiring high-resolution target discrimination.

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.