High frequency communication systems are critical for 5G networks, particularly in the millimeter-wave bands, where ultra-wideband (5G-UWB) performance is essential for high data rates and low latency. In this work, we propose, for the first time to the best of our knowledge, an ultra-wideband 5G MIMO beamforming module covering both the 28 and 60 GHz bands. The proposed design is based on a low-cost, low-profile Rotman Lens (RL) implemented on an FR4 substrate with a thickness of 1.6 mm and a dielectric constant of 4.3. The RL features five beam ports and seven array ports, with additional dummy ports introduced to minimize reflections and enhance adjacent beam port isolation across the full 5G-UWB range. Simulation results demonstrate excellent performance, with isolation and mutual coupling maintained below -25 dB between input beam ports and below -15 dB between array ports across the entire bandwidth. The VSWR remains below 2 for all ports. Although this work presents a single RL-based beamformer, it is envisioned as a building block within a larger hybrid MIMO architecture, where multiple lenses can be interconnected to support parallel data streams and spatial multiplexing. This modular approach enables flexible scaling to full MIMO operation while maintaining low cost and compactness. The proposed design is a strong candidate for 5G and mmWave applications, including hybrid beamforming systems, MIMO architectures, radar, and satellite communications. Comparative analysis with recent literature demonstrates its superior bandwidth and isolation performance.

Circularly polarized (CP) antennas minimize polarization losses and improve signal reliability in ultra-reliable and low-latency satellite communication. Compact design, wide impedance and axial ratio bandwidth (ARBW) are key requirements for circularly polarized antennas utilized for modern automotive wireless applications. In this work, a miniaturized slotted antenna for C-band automotive-oriented wireless applications is proposed. The antenna achieves a wide measured impedance bandwidth of 69.5% (4.0-8.26 GHz, 4.26 GHz) and exhibits an ARBW of 51% (4.96-8.33 GHz, 3.37 GHz). The overall compact size of 25 × 30 × 1.6 mm³ (0.33λ × 0.40λ × 0.02λ at 4 GHz) further underscores its suitability for integration in space-constrained C-band communication systems. The anticipated design is optimized using rigorous parametric analysis to achieve a wide ARBW from θ = -27˚ to +33˚ which is very beneficial for satellite applications. The fabricated prototype demonstrates a measured peak gain of 4.8 dBi and radiation efficiency ranging from 82% to 92% across the radiating band. Measurement results obtained from the fabricated antenna are validated with simulations and show satisfactory agreement. The anticipated design, when compared with existing literature, is found to outperform other designs in terms of size, ARBW, and impedance bandwidth. The achieved resonance in the proposed design can be utilized for satellite communication, medical and automotive applications (tele-operated driving support, high-definition map collecting and sharing, infrastructure-based teleoperated driving), and other applications in C-band.

The increasing deployment of 5G wireless technologies has raised the need for accurate, tissue equivalent phantoms to explore electromagnetic (EM) wave interactions with human body organs. This paper investigates stability and homogeneity of a low-cost, easy-to-fabricate human muscle phantom exposed to radiation exposure from 5G signals at frequencies of 700 MHz, 2.4 GHz, 3.5 GHz and 20 GHz. The phantom was formulated using agar, polyethylene powder, sodium chloride, xanthan gum, sodium dehydro-acetate, and deionized water. Its permittivity and conductivity were measured using a vector network analyzer (VNA) over a 45-day period under low (2-5°C) and room temperature (27°C) storage. The results showed that the phantom was most homogenous at 20 GHz with the standard deviation (SD) of 0.51033 and the relative standard deviation (RSD) of 1.67%. For conductivity, the phantom demonstrated good homogeneity. However, it was not aligning to the corresponding real human muscle conductivity. The most homogenous conductivity was observed at 2.4 GHz with the SD and RSD of 0.06194 and 2.31% respectively. In terms of stability, relative permittivity was most stable at 20 GHz under room temperature conditions, with a maximum deviation of 21%. Stability of conductivity performance, on the other hand, was best maintained at 2.4 GHz under room temperature, where the highest observed deviation was 53%. The findings highlight the potential of using low-cost materials to fabricate phantoms with stable electromagnetic properties suitable for wireless exposure studies, although further optimization is needed for accurate conductivity matching.

This paper presents a passive, structure-based approach for selective signal transmission and crosstalk suppression in dense radio frequency identification (RFID) tag environments. The proposed method employs a mechanically reconfigurable double-layer tag design based on the mirror-antenna principle, which enables dynamic switching between transmission and shielding modes by adjusting the interlayer spacing. Simulation results demonstrate pronounced differences in the reflection characteristics and radiation intensity of the tag under the two operating modes at 915 MHz. Experimental validation further confirms the effectiveness of the system in mitigating interference and ensuring reliable tag identification in multi-tag scenarios. The design is compact, energy-efficient, and cost-effective, supporting scalable applications in smart retail and automated inventory management.

Based on the current trends in wireless communication systems, a novel high-isolation dual-notch ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna is proposed, measuring 46 mm × 46 mm × 0.8 mm. The antenna is printed on an RO4350 substrate and consists of two identical antennas placed orthogonally. The antenna unit features a third-order stepped rectangular structure and employs microstrip feeding, incorporating inverted U-shaped and M-shaped grooves etched onto the antenna unit to achieve dual-notch functionality, thereby addressing electromagnetic interference issues in wireless local area networks (WLAN) operating at 5.15-5.85 GHz and 7.25-7.75 GHz. To address the issue of mutual coupling in MIMO antennas, this paper presents an innovative decoupling method known as the RMS-ZINC approach. This technique involves excavating a T-shaped groove on the rear of the dielectric substrate, symmetrically aligned with the diagonal, and filling it with a dielectric material primarily composed of zinc. This material substitution effectively manipulates the coupling current paths, achieving a high isolation level of -20 dB. The experimental results show that the operating bandwidth of the antenna ranges from 2.89 to 10.19 GHz, with a peak gain of approximately 5 dB (7.15 dBi) and a maximum radiation efficiency of up to 92%. The measured results are essentially consistent with the simulated ones, indicating the practical application value of the proposed MIMO antenna with notch functionality.

This paper presents the design, fabrication, and analysis of a wideband circularly polarized wearable antenna operating in the frequency range of 2.6 GHz to 4.7 GHz. The antenna is designed on a jeans substrate with dimensions of 25 × 30 × 1.4 mm³, having a dielectric constant of 1.7 and a loss tangent of 0.085. The proposed antenna demonstrates a gain of 2.8-3.4 dB across the operating frequency band and exhibits circular polarization in the frequency range of 3.2 GHz to 3.9 GHz. To achieve wideband performance and circular polarization, the antenna design incorporates an octagonal ring patch with a hybrid slot and stub in the partial ground plane, along with four slots in the ring patch. The antenna is fabricated and its performance is validated through Vector Network Analyzer and anechoic chamber measurements, showing good correlation with simulated results. Specific Absorption Rate (SAR) analysis and on-body simulations are conducted to evaluate its suitability for wearable applications.

To address the engineering challenges of conformal frequency diverse array (FDA) on complex curved surfaces and beamforming optimization, and leveraging the fact that the surface of a streamlined platform can be approximated by an elliptical arc, an elliptical-arc conformal FDA is taken as a representative example, and a conformal frequency diverse array method based on joint parameter optimization (JO-CFDA) is proposed. First, a polygonal approximation model is employed to achieve conformity between the array and the curved surface; then, the parameter α is introduced to control the non-uniform distribution of inter-element spacing along each edge; finally, the parameter β is used to allocate the frequency-offset exponent in a slope-normalized manner. These two parameters work in concert to jointly optimize beam characteristics in both the spatial layout and frequency-domain distribution. Simulation results demonstrate that the proposed method can significantly reduce sidelobe levels and enhance beam directivity while maintaining mainlobe width and peak gain, thereby validating its effectiveness and superiority.

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.