This paper describes the design methodology of a compact multiband microstrip patch antenna intended for next-generation wireless communication applications. The proposed antenna operates over seven distinct frequency bands: 1.25-1.32 GHz, 2.30-2.44 GHz, 2.50-2.75 GHz, 2.92-3.25 GHz, 3.40-3.65 GHz, 3.70-4.23 GHz, and 4.70-6.0 GHz. These operating bands support a wide range of wireless services, including LTE, 5G communications, Wi-MAX, ISM applications, radar systems, and broadband wireless communications. Multiband performance is achieved through the incorporation of three strategically placed slits in the radiating patch along with a square split-ring resonator (SSRR). By adjusting the dimensions of the slits and the position of the SSRR, the operating frequency bands can be effectively tuned. The proposed antenna occupies a compact footprint of 40 × 40 mm² and consists of a radiating patch, a partial ground plane, and an SSRR structure. Simulation results demonstrate resonant frequencies at 1.3, 2.38, 2.66, 3.0, 3.5, 4.2, 4.9, and 5.7 GHz. Owing to its compact size, multiband capability, and simple structure, the proposed antenna offers advantages in terms of reduced cost, lower system complexity, and miniaturization, making it suitable for modern wireless communication systems.

Due to the high electrical conductivity, relative permittivity, and magnetic permeability of seawater, the propagation behavior of electromagnetic fields differs significantly from that in air. The conductive nature of seawater causes strong eddy current loss and magnetic field attenuation, thereby reducing the effective coupling coefficient and resulting in frequency detuning between the transmitter and receiver coils. Moreover, the marine environment introduces parasitic impedance paths and additional energy dissipation due to the conductive medium, which further decreases transmission efficiency. These unique electromagnetic characteristics make the design and optimization of wireless power transfer (WPT) systems in seawater more complex and challenging than in air, motivating this study to develop and analyze a dual-receiver WPT architecture that improves midrange transmission efficiency under underwater conditions. To address this issue, a single-transmitter dual-receiver (1TX-2RX) WPT system operating in the 300-550 kHz frequency range is designed and implemented. Experimental results demonstrate that, under midrange transmission in seawater, the efficiency of the proposed 2RX architecture improves markedly from 12% in the 1RX system to 25%, while maintaining stable output performance under various receiver coil misalignment conditions. In addition, compared with operation in air, the optimal operating frequency of the 2RX system in seawater shifts leftward from approximately 460 kHz to 410 kHz. To better characterize the impact of seawater on transmission performance, complex impedance and mutual inductance parameters are incorporated into the conventional circuit model, enabling effective representation of the additional losses and coupling attenuation induced by the conductive medium. The predicted load voltage is consistent largely with the experimental measurements, validating the accuracy and applicability of the proposed modeling approach. Overall, this study not only verifies experimentally the feasibility of improving midrange transmission efficiency through a dual-receiver architecture but also establishes theoretically a circuit modeling method suited better for seawater environments, providing useful insights for the design and optimization of marine WPT systems.

In this study, a miniaturized long-read-range anti-metal ultra-high frequency (UHF) RFID tag patch antenna for bank cash transport boxes is presented. Short-circuit inductors were loaded on the side of the antenna, and double H-shaped slots were etched on the patch surface. These structures extend the current path and increase the electrical length, which lowers the resonant frequency and enables antenna miniaturization. The antenna impedance can be flexibly tuned by adjusting the position and width of the short-circuit inductors and the length of the double H-shaped slots. Conjugate matching with the RFID chip is therefore achieved to ensure maximum power transfer. In addition, the short-circuit inductors reduce the influence of the metal plate and improve the current distribution. Consequently, the radiation efficiency is enhanced, and a long reading distance is obtained. The proposed antenna was fabricated and measured, and good agreement between the simulation and measurement results was observed. The measured results show that the antenna occupied an area of 615 mm² and achieved a maximum reading distance of 12.4 m when mounted on a metal cash-in-transit box. The presented antenna is suitable for the full-process management of bank cash transport boxes in different application scenarios.

Polynomial Chaos Expansion (PCE) is widely utilized in uncertainty quantification (UQ) for electromagnetic compatibility (EMC) due to its robust global predictive capabilities. However, its computational overhead increases exponentially with stochastic dimensionality, leading to the notorious curse of dimensionality. To address this bottleneck, this paper proposes a generalized preprocessing dimensionality reduction framework designed to enhance the performance of PCE. By decoupling dimensional screening from predictive modeling, the proposed framework first employs low-cost estimators to identify significant random variables. Subsequently, an improved PCE model is constructed within the reduced feature space. Given the prohibitively high computational cost of acquiring EMC simulation samples, this study instantiates a screening module within the framework that integrates Least Squares Support Vector Regression (LSSVR) with Sobol indices. Finally, the proposed framework-based method is applied to a cable crosstalk case study to validate its effectiveness and engineering applicability.

This paper examines approaches to improving metamaterial antennas using the Theory of Characteristic Modes (TCM). We investigate the electromagnetic resonant modes of antenna elements, with a focus on how their material properties interact with their geometric configurations. The main goal is to enhance key features, such as bandwidth and radiation efficiency, in the electromagnetic modes of metamaterials. The study also examines how structural features, such as slots and metamaterial shapes, affect antenna performance. Splitring resonators (SRRs) and complementary split-ring resonators (CSRRs) are considered to analyze how electric and magnetic modes can contribute to radiation efficiency using the approaches proposed in this paper. Important parameters, including characteristic angles, current distribution, bandwidth, and radiation patterns, are compared across different designs to identify the most efficient configurations. Notably, the analysis shows that when the SRR and CSRR structures are optimized, they can achieve similar radiation efficiency for electric and magnetic modes, respectively. Consequently, the TCM predictions are strongly corroborated by the S-parameter results. Overall, this paper provides practical insights into the design of compact and efficient metamaterial antennas and offers useful guidance for future wireless communication systems.

This paper presents a compact printed ultra-wideband (UWB) monopole antenna employing a coupling structure and a short stub for broadband impedance matching and antenna miniaturization. The proposed antenna is fabricated on an FR-4 substrate with dimensions of 24 × 14 × 1.6 mm³ and fully covers the FCC-defined UWB from 3.1 to 10.6 GHz, achieving a VSWR of ≤ 2. The coupling structure introduces additional capacitive loading, while the short stub provides effective inductive compensation. This enables stable, broadband operation despite significant size reduction. Experimental results demonstrate quasi-omnidirectional radiation characteristics over the entire operating band. In addition to frequency-domain evaluation, time-domain performance is investigated using two identical antennas arranged in face-to-face and side-by-side configurations. The measured correlation coefficients exceed 0.94 in both configurations, and the group delay remains nearly constant at approximately 0.3 ns across the UWB. This indicates high waveform fidelity. These results confirm that the proposed antenna is well-suited for compact UWB communication systems requiring both broadband and time-domain stability.

This paper proposes an analytical method for arbitrary spatial orientations that eliminates systematic errors arising from neglecting rounded corners in planar rectangular coils in wireless power transfer systems. The rounded rectangular coil is decomposed into straight and quarter-arc segments. Using Neumann's formula, mutual inductance expressions for straight-straight, straight-arc, and arc-arc interactions are derived. We establish a unified spatial model using Z-Y-X Euler angle transformations to describe arbitrary translations and rotations in 3D space. We obtain the total mutual inductance by superposition. Results show that neglecting rounded corners increases error as the corner radius grows. Under various conditions, including lateral and axial displacements and composite rotations, the method achieves average relative errors below 1.5% compared with finite element simulations (validated for corner radii up to 12 mm) and below 2.5% compared with experiments (validated for a corner radius of 5 mm), demonstrating high accuracy and robustness.

In this paper, a dual-band-notched ultra-wideband MIMO antenna fed by a microstrip line is designed. The ultra-wideband characteristics are obtained by etching a semi-elliptical notch on a circular radiation patch. For the achievement of dual-band-notched features, a U-shaped slot and an inverted U-shaped slot are employed. Additionally, the Characteristic Mode Analysis (CMA) is used to verify and analyze the notch-band and broadband characteristics. Each ground plate is connected by adding a cross-shaped branch, and a circular ring is loaded to further improve antenna isolation (|S₂₁|). This antenna is implemented on an FR4 substrate, and its whole size is 60 mm × 60 mm × 0.8 mm. The measured findings verify that the antenna functions within a broad bandwidth ranging 3.12-21.2 GHz (relative bandwidth 148.6%) and two frequency band rejections of 5.94-7.17 GHz and 12.49-13.92 GHz, effectively suppressing the 6G band, which belongs to the international satellite mobile communication system and the Ku band downlink. The port isolation exceeds 20 dB, the ECC is below 0.04, and the diversity gain (DG) is in excess of 9.97, all of which demonstrate the antenna's excellent diversity performance and superior radiation characteristics. The antenna is a frontrunner for next-generation wireless communication applications.

This work introduces an innovative fractal microstrip sensor, shaped like a Māra cross enclosed within a square, designed and fabricated on a Rogers RT5880 substrate for high-precision detection and characterization of edible oils. The proposed resonant shape enhances electric-field concentration and improves the interaction between the material under test and the electromagnetic field, resulting in improved sensitivity and resonant response. The sensor operates at a frequency of approximately 4 GHz within the S-band, with an area of 50 × 50 mm², making it suitable for portable and low-cost applications. The results demonstrated clear frequency shifts for various oil types, including coconut oil, olive oil, sunflower oil, and sesame oil. A mathematical model was also developed to extract the complex electrical permittivity with a high coefficient of determination of 0.99, showing excellent agreement between the experimental and theoretical results. The fractal sensor exhibits a remarkable normalized sensitivity of 0.86% and 3.56% per unit dielectric variation and error of 0.03% and 0.13%, with frequency shifts of 163 MHz and 103 MHz for water and ethanol detection, respectively. Maximum sensitivities reached 15.23% for olive oil and 11.32% for sunflower oil, surpassing many previously published studies.

Accurate simulation of partially coherent imaging is crucial for computational lithography, with Abbe and Hopkins as the two main formulations being used. Although the two methods are equivalent in theory, practical simulators making independent choices between Abbe and Hopkins could hardly produce consistent results that match the desired accuracy owing to the inherently different ways of numerically representing, discretizing, and truncating the illumination source and lens pupil function, etc. Moreover, classical Hopkins models require prior construction and/or eigen decomposition of the high-dimensional transmission cross coefficient (TCC), the prohibitive costs of which hinder timely model verification. To address these challenges, we developed a unified Abbe-Hopkins formulation in conjunction with a TCC-free Hopkins pointwise sampler for efficient cross-model validation. Our formulation supports both Abbe and Hopkins modeling in a single unified framework, with the two simulation modes using exactly the same numerical representations of the illumination source and projection lens. Cross-model verification for randomly sampled points is performed efficiently by evaluating the Hopkins quadratic form through a fast Fourier transform of an image and a few pointwise multiplications between images, without ever explicitly constructing a TCC and eigen-analyzing it. Numerical tests show that the Abbe and Hopkins results agree up to the machine precision level.

In modern wireless communication systems, it is essential to use a bandpass filter at the front end of the radio receiver to limit the bandwidth of the signal before it is passed to the rest of the receiver. This study presents the design, fabrication, and analysis of a compact dual-band metamaterial bandpass filter (BPF) for modern wireless communication systems. The proposed structure evolves from an initial open-loop resonator design and integrates metamaterial unit cells to significantly enhance frequency selectivity, reduce inser-tion loss, and improve impedance matching. To further enhance the performance, defected ground structures were incorporated, resulting in refined bandwidth control and supe-rior return-loss characteristics. The final filter operates at center frequencies of 2.4 and 3.95 GHz, achieving low insertion losses of 0.6 and 0.9 dB, along with return losses of 27.6 and 32.9 dB, respectively. Its compact size of 20 × 18.46 mm² corresponds to an electrical size of (0.33 × 0.25)λ_g². Owing to its excellent electrical performance and miniaturized form, the proposed filter is suitable for wireless communication applications, including GPS, Blue-tooth, Wi-Fi, WiMAX, 5G, and sub-6 GHz bands, making it ideal for modern systems, such as the Internet of Things (IoT).

Analyzing the electromagnetic scattering of electrically large targets with complex coatings presents significant computational challenges. This paper proposes a highly efficient hybrid acceleration method within the Electric Field Integral Equation (EFIE) framework, combining the Thin Dielectric Sheet (TDS) approximation, Characteristic Mode Analysis (CMA), and Adaptive Cross Approximation (ACA). First, a generalized TDS formulation maps dual-layer equivalent currents onto a single-surface model, substantially reducing the initial unknowns while preserving physical consistency. Next, domain decomposition and CMA are utilized to construct a reduced-order matrix, enabling a direct, non-iterative solution that fundamentally bypasses traditional convergence bottlenecks. Finally, the ACA algorithm compresses well-separated far-field interactions to further minimize computational and memory costs. Comprehensive numerical experiments calculating the Radar Cross Section (RCS) of electrically large coated targets demonstrate that the proposed hybrid scheme offers superior accuracy and drastically reduces matrix storage and computation time compared to conventional full-wave direct solvers and traditional TDS-EFIE (electric and magnetic) formulations.

This paper presents a novel tunable reflection-type phase shifter (RTPS) employing an impedance-transforming transdirectional (IT TRD) coupler terminated by varactor-based reflective loads. The coupler is based on double-shielded coupled lines (DSCLs) and is implemented as a distributed surface-mount component, providing inherent impedance transformation for increasing the relative phase shift for given varactors. Fabricated using standard PCB technology, the prototype features intrinsic DC isolation between the RF path and control circuits, requiring only a single control voltage. Measured results show that the RTPS operates over a wide frequency band from 2.2 to 2.8 GHz (24%), achieving a tunable phase shift of up to 180˚ with an insertion loss of 1.3±0.7 dB and a return loss better than 11 dB. The proposed design is characterized by compact physical dimensions of 0.1 × 0.21λ at the center frequency.

Conventional model predictive flux control (C-MPFC) generates large steady-state ripples, and the system reference values are heavily dependent on the permanent magnet (PM) flux This paper proposes a discrete space vector modulation model predictive flux control with a reformulated incremental cost function and efficient search strategy (RDSVM-MPFC) for surface-mounted permanent magnet synchronous motors (SPMSMs). First, a unified cost function based on flux increments is reconstructed by redefining the d-axis reference flux. Second, the candidate set is expanded via discrete space vector modulation (DSVM) in the spatial flux increment plane to generate a set of virtual flux increment vectors (VFIVs), thereby significantly suppressing steady-state errors. Furthermore, to manage the heavy computation burden associated with the expanded VFIVs, a three-stage hierarchical optimization strategy is designed. This approach achieves rapid identification of the optimal control vector, which preserves the high steady-state precision while largely reducing the computational complexity of the system. Finally, experimental studies demonstrate that the proposed RDSVM-MPFC strategy eliminates sensitivity to PM flux variations and markedly suppresses steady-state pulsations.

This study focuses on a Short-Primary Single-Sided Linear Induction Motor (SSLIM), which is widely used in the rail transit sector due to its low operating noise and small turning radius. Therefore, designing linear induction motors with better performance is of great significance. This study aims to enhance electromagnetic thrust and reduce fluctuations in electromagnetic force by optimizing the motor's structural design. First, a motor model is established based on its operating principles, and a brief analysis of its electromagnetic characteristics is conducted. Second, two design schemes were selected for both the primary and secondary components. For the primary components, one scheme employs a chamfered structure to suppress fluctuations in electromagnetic force, while the other modifies the tooth tip shape from rectangle to trapezoid to increase thrust. For the secondary components, one scheme involves incorporating a material with higher electrical conductivity into specific areas of the aluminum plate, and the other involves slotting to optimize the magnetic field distribution and increase thrust. Finally, the performance of the optimized model was compared with that of the initial model. The results showed that the average thrust increased by 5.3%, while the fluctuations in thrust and normal force decreased by 13.6% and 30%, respectively, validating the effectiveness of the optimization approach.

In this study, a novel miniaturized multiband flowerpot-shaped patch-based cylindrical dielectric resonator antenna (FPSDRA) is proposed for 5G-enabled GNSS (GPS), UMTS, PCS, Wi-Fi5, WiMAX, and NR 77/78 sub-6 GHz 5G applications. The proposed antenna prototype operates at 1.54 GHz, 2.01 GHz, 3.23 GHz, 3.95 GHz, and 5.54 GHz for the mentioned applications. It employs a novel low-cost flowerpot-shaped radiating patch underneath a cylindrical dielectric resonator (CDR) made of alumina ceramic (Al₂O₃, ∈_DR = 9.8) material and is fed by a combined microstrip-line-tapered trapezoidal feedline. Later, a reduced ground plane is used as a reflector on the rear side of the substrate to reduce antenna size. It is made up of a low cost 1.6 mm FR4 laminate sheet (∈_r = 4.4, tanδ = 0.02) and miniaturized to a physical size of 65 × 45 mm². The parametric analysis was carried out for reflection coefficients (S₁₁-dB) by changing the ground plane width, CDRA radius, and flower petal radius to achieve adequate results. Likewise, this prototype has measured reflection coefficient of < -20 dB for 1.54 GHz (L1-band), < -25 dB for 2.01/3.23 GHz (S-band), < -20 dB for 3.95 GHz (S-band), and 5.54 GHz (C-band), peak gains of 2.01 dBi, 2.05 dBi, 3.02 dBi, 4.85 dBi, and 2.24 dBi for the respective bands along with adequate -10 dB impedance matching bandwidths and stable radiation features in a convincing agreement compared to earlier designs. The proposed prototype is simulated in CST software, assembled, and tested by VNA and an anechoic chamber setup for L1/S/C band applications.

This paper proposes a flexible four-element super-wideband (SWB) multiple-input multiple-output (MIMO) antenna based on characteristic mode analysis (CMA) for wearable wireless communication, broadband sensing, and wireless body area network (WBAN) applications. The antenna employs a spiral mesh radiator combined with a defected ground plane incorporating triangular and T-shaped slots to form a multi-slot-coupled current path, enabling the cooperative excitation of multiple characteristic modes. The proposed antenna achieves an impedance bandwidth of 3.23-44.68 GHz, satisfying the SWB criterion. A four-port MIMO configuration is adopted to enhance diversity and isolation performance. Measured results agree well with simulations, with port isolation better than 20 dB across the operating band. In addition, the envelope correlation coefficient (ECC) is below 0.0015; the diversity gain (DG) is close to 10 dB; the total active reflection coefficient (TARC) is below -10 dB; and the channel capacity loss (CCL) is less than 0.12 bit/s/Hz. The antenna also maintains stable SWB impedance matching and radiation performance under bending conditions, making it suitable for flexible SWB wearable and WBAN systems.

An improved scattering (S-)parameters extraction method, based on the forward and backward propagating waves under oblique incidence on metamaterials (MMs), is proposed to accurately extract electromagnetic parameters for asymmetric uniaxial MMs in a broad frequency range. The proposed approach equivalently models asymmetric MMs as two isotropic media (distinct from the 3 × 3 matrix-form anisotropic medium). To validate the effectiveness of the proposed method, a low-thickness asymmetric absorptive frequency-selective surface (AFSS) and a high-thickness 7-layer absorber were designed, simulated, and analyzed.

This paper presents a compact dual-band reconfigurable MIMO antenna array that simultaneously addresses the challenges of frequency agility and strong inter-element coupling in densely integrated antennas. The proposed antenna element employs a slit-loaded microstrip patch combined with a varactor diode to achieve continuous tuning of the high-frequency band while maintaining a stable low-frequency resonance. To suppress the severe mutual coupling typically induced by reconfigurable structures, an optimized etched ground-plane topology featuring branched Π-shaped slots is introduced. This isolation structure effectively alters surface-wave propagation paths and attenuates coupling fields, resulting in a significant improvement in port-to-port isolation across both operating bands. Comprehensive parametric studies validate the effectiveness of the slot configuration in enhancing decoupling performance under various tuning states. A 1×4 MIMO array prototype was fabricated and experimentally evaluated, showing good agreement with simulations. Measurements demonstrate wide-range high-band tuning from 3.6 to 4.2 GHz, stable low-band operation near 2.3 GHz, improved radiation efficiency, and low envelope correlation coefficients, confirming strong diversity performance. Owing to its compact structure, stable dual-band characteristics, and robust reconfigurability, the proposed design offers a promising solution for adaptive and space-constrained modern wireless communication systems.

The Plasmonic nanoantennas operating in the optical frequency range often experience reduced radiation efficiency due to substrate-induced nonradiative losses and insufficient electromagnetic field confinement. This work aims to systematically examine the influence of substrate material properties on plasmonic resonance behavior, surface current distribution, and radiation efficiency of a gold nanostrip patch antenna. A fixed-geometry plasmonic nanoantenna is designed and numerically investigated on five substrates, namely SiO₂, GaN, GaAs, AlAs, and AlGaAs. Full-wave electromagnetic simulations are performed using frequency-dependent material dispersion modelled through established Drude-Lorentz formulations. The antenna implemented on the Au-SiO₂ combination provides the most favourable plasmonic performance, yielding the best impedance matching (-51.27 dB), maximum radiation efficiency of 83%, wide impedance bandwidth (118 THz), and highly stable radiation patterns. GaN also exhibits strong performance with a high radiation efficiency (71%) and wide bandwidth (97 THz), making it a viable choice for high-power optical systems. GaAs, AlAs, and AlGaAs substrates show reduced efficiency due to higher dielectric losses and weaker plasmonic confinement. The study confirms that substrate permittivity and loss characteristics play a crucial role in determining plasmonic nanoantenna performance.