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.

Accurate modeling of millimeter-wave (mmWave) and terahertz (THz) electromagnetic wave propagation is crucial for analyzing and designing emerging high-frequency wireless systems at an early stage. Conventional parabolic equation (PE)-based models offer high computational efficiency but suffer from reduced accuracy at mmWave/THz frequencies owing to material losses, fine-scale scattering, and complex non-line-of-sight (NLOS) interactions. Although purely data-driven approaches are flexible, they often lack physical consistency and generalization capability. This study proposes an AI-enhanced parabolic equation (AI-PE) framework that integrates a wide-angle PE solver with a neural-network-based residual correction model. The AI component learns systematic PE prediction errors associated with frequency-dependent attenuation, diffraction, and scattering while preserving the underlying physical structure of the wave model. Validation was performed against full-wave and ray-tracing reference solutions in representative indoor corridor and urban microcell scenarios. The numerical results at 28, 60, and 140 GHz demonstrate a 25-40% reduction in the path-loss prediction error, improved statistical agreement of the RMS delay-spread estimates, and over 50% reduction in the computational cost compared with deterministic ray tracing. The energy conservation and phase continuity of the corrected fields were explicitly verified. The framework was primarily validated for interpolation within the trained frequency range and demonstrated robust performance across structured propagation environments.

Photovoltaic (PV) power sequences are highly susceptible to high-frequency stochastic noise under complex micro-meteorological conditions. Furthermore, existing forecasting models struggle with isolated multi-scale physical features and insufficient nonlinear mapping capabilities. To address these limitations, this paper proposes an improved TimeMixer-based PV power forecasting method. First, the macroscopic trend and microscopic seasonal components are extracted via a past-decomposable-mixing architecture. Second, an adaptive gated feature fusion mechanism is introduced as a physically motivated feature-level filter to attenuate high-frequency noise channels through dynamic attention masks, effectively blocking the cross-scale propagation of invalid meteorological interference. Finally, a cross-scale joint nonlinear network is constructed to capture nonlinear interactions among multi-band components through state matrix aggregation and activation operators. Case studies utilizing operational data from a 50 MW PV power plant, in Xinjiang, China, demonstrate that the proposed architecture effectively overcomes smoothing degradation and phase lag under complex scenarios, such as abrupt cloud cover. Compared with the original baseline, the proposed method reduces the forecasting mean squared error by 10.80%, significantly enhancing both global fitting accuracy and dynamic extreme-value tracking capability.

This study details the design and analysis of a tri-arm-shaped microstrip patch antenna with a partial ground plane, intended for wearable applications. The proposed antenna is designed on a flexible jeans substrate and operates within the Industrial, Scientific, and Medical (ISM) band (2.40-2.48 GHz). It features a low-profile structure with overall dimensions of 40×20×1.2 mm³, impedance bandwidth of 580 MHz, and radiation efficiency of 82%. Impedance matching and miniaturization were achieved in the design through the use of the stub loading technique. Furthermore, on-body measurements, such as bending and crumpling analyses, demonstrated its robust performance with good return loss values. The Specific Absorption Rate complies with the safety limits, and the proposed conformal antenna is reliable for wearable applications.

This paper presents a wideband four-port microstrip antenna operating from 2.75 GHz to 6.75 GHz with frequency reconfigurability and controllable notch characteristics. The antenna employs an asymmetric radiating structure to realize circular polarization around 5.5 GHz, while multilayer graphene(MLG) pads are introduced to enable bias-controlled frequency tuning and adjustable band rejection. The four-port configuration, implemented on an RT/Duroid 5880 substrate (ε_r = 2.2, thickness = 1.6 mm), achieves inter-element isolation better than 20 dB without additional decoupling structures. The proposed design also exhibits strong diversity performance with an envelope correlation coefficient below 0.02 and diversity gain above 9.97 dB. The results demonstrate that the proposed antenna provides a compact and low-complexity solution for wideband and reconfigurable sub-6 GHz wireless communication applications.

An innovative analysis of a negative group delay (NGD) circuit exhibiting a dual bandpass (BP) characteristic is presented. The passive BP-NGD topology consists, essentially, of parallel RLC resonant networks. The BP-NGD topology is characterized by the NGD value, the NGD center frequency, and the attenuation, as functions of the constituent RLC resonant networks. The dual BP-NGD topology is designed using series impedances, which are composed of two distinct parallel RLC networks. After considering the reduced-order model of the passive cell within the NGD frequency range, which enables the determination of component values for the dual BP-NGD circuit, the circuit is formulated as a function of the desired NGD values and center frequencies. The feasibility of the design theory is verified through a proof-of-concept (PoC), designed to operate with the following specifications (1 MHz, -20 μs, -8 dB) and (2 MHz, -20 μs, -8 dB). First, a frequency-domain analysis of the PoC demonstrates the dual BP-NGD behavior, exhibiting an attenuation of approximately 8 dB. Subsequently, time-domain analyses were conducted using input signals with amplitude modulation on sinusoidal carriers at frequencies of 1 MHz, 1.5 MHz, and 2 MHz. The obtained results highlight the possibility of generating output signal envelopes that exhibit a temporal advancement relative to the input ones, provided that the input signal spectrum falls within the NGD bandwidth. However, the output envelope exhibits a positive delay when the input signal spectrum lies outside the NGD frequency band. A potential application principle for the dual BP-NGD circuit is discussed, specifically for the compensation of delay dispersion in electronic and communication systems.

This paper presents a compact, low-profile, single-layer filtering antenna. The antenna features a simple structure, consisting of a substrate, two pairs of U-shaped defected ground structures, a symmetric dumbbell-shaped radiating patch, and a microstrip cross-feed line with asymmetric branches. The symmetric dumbbell-shaped patch and the asymmetric branch feedline collaboratively introduce additional high-frequency resonances, thereby broadening the impedance bandwidth. Furthermore, two pairs of U-shaped slots are etched into the bottom layer to introduce two radiation nulls on both sides of the passband, enhancing the frequency selectivity at the band edges and optimizing the antenna's radiation and filtering performance. To validate the proposed design, a prototype of the antenna was fabricated and measured. The measured and simulated results are in good agreement. The design achieves a wide impedance bandwidth of 48.6% from 3.7 to 6.18 GHz (centered at 5 GHz), a peak realized gain of 4.5 dBi, and a compact overall size of 35 mm × 29 mm × 0.8 mm. Moreover, the antenna structure is simple and easy to fabricate. Benefiting from its superior radiation performance and filtering characteristics, the proposed antenna is well-suited for wireless communication applications in the 5G Sub-6 GHz and WiFi-6E bands.