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, we developed a multilevel multiple scattering theory (ML-MST) for the numerical solutions of multiple scattering equations. We formulated multiple scattering theory using vector cylindrical waves (VCW) in the MST-VCW formulation and the translational addition theorem with exciting fields in VCW. A problem with this formulation is that neighboring scatterers can have overlapping circles. In this study, multiple scattering theory is formulated using the method of moments (MoM) in the MST-MoM formulation, with the exciting field in terms of MoM unknowns. The ML-MST is developed by separating the scattering from other scatterers into neighbor and non-neighbor contributions, resulting in 2-level interactions. We then replace the MST-VCW neighbor scattering with the corresponding MST-MoM neighbor scattering. The ML-MST eliminates the issues of overlapping circles of neighbors. We apply the ML-MST formulations to the problem of band diagrams of photonic crystals by summing the scattering from non-neighbors using broadband Green's functions (BBGF). The result is the multilevel Korringa-Kohn-Rostoker (KKR) equation. Numerical illustrations were performed for the 2D case. The accuracy of the solutions was validated by comparing {them} with COMSOL simulations. The CPU time of the ML-MST was more than two orders of magnitude lower than that of COMSOL.

A two-port multiple-input multiple-output (MIMO) antenna that pairs a slotted annular-ring radiator with a single front-side parasitic strip is reported for X- and Ku-band service. Three features distinguish the design. A set of eight arc slots elongates the ring-current path by 9.1% and drags the lower band edge down to 8.00 GHz on a board only 0.40λ₀ tall, so the aperture keeps a narrow strip outline suited to edge mounting. The front-side strip works as a three-quarter-wave trap on the shared substrate and lifts worst-case in-band isolation by 8.4 dB with no defected ground and no via. Every element of the accompanying circuit model maps to a named piece of metal, which lets the model track S₂₁ as well as S₁₁, whearea most published models fit the reflection coefficient alone. The radiator occupies 40 × 15 × 0.8 mm³ on Rogers RT/Duroid 5880 (ε_r = 2.2, tanδ = 0.0009). Measurement gives a -10 dB band of 8.00-13.96 GHz, a fractional bandwidth of 54.3%, isolation better than 21.1 dB across the band with a 33.4 dB peak, gain of 4.0-6.5 dBi and radiation efficiency of 77-84%. Diversity metrics stay within useful limits: envelope correlation coefficient below 0.0038, diversity gain above 9.981 dB, mean effective gain between -3.05 and -3.52 dB, channel capacity loss under 0.331 b/s/Hz and ergodic capacity of 13.01-13.28 b/s/Hz. Characteristic mode analysis at 8.85 and 11 GHz identifies modes carried by the ring. A quarter-wave counterpoise argument predicts the lower edge to within 1.11% of measurement, and two independent routes to the ring resonance differ by only 4.14%. The circuit model reproduces the full-wave response with 0.352 dB RMS error on S₁₁ and 0.611 dB on S₂₁, matching the upper band edge to 0.07%.

Current research on cable current-carrying capacity mostly focuses on a single laying form and lacks a systematic comparison of temperature-load characteristics under three mainstream laying conditions: direct burial, pipe duct laying, and cable trench laying. This paper takes the YJLW03-64/110\,kV single-core high-voltage cable as the research object, develops a two-dimensional electromagnetic-thermal-fluid multi-physics field-coupling model, and determines the carrying capacity by constraining the conductor's maximum allowable temperature to 90 ℃. The finite element software COMSOL is used to complete the simulation analysis of multiple conditions under the three laying methods. For direct burial laying, the improvement effect of high thermal conductivity sandy soil backfill thickness of 100 mm and 200 mm on heat dissipation is explored; for pipe duct laying, the temperature distribution and carrying capacity differences between air gap and cement-based thermally conductive grout filling are compared; for cable trench laying, the convective heat transfer effect of solid supports and different support opening rates is analyzed. The results show that the improvement measures under the three laying methods can respectively increase the cable current-carrying capacity by varying degrees. The results can provide support and technical reference for selecting high-voltage cable laying methods, as well as expanding and renovating carrying capacity.

Near-field SGP (Slotted Ground Plane)-based systems, also known as DGS (Defected Ground Structure), are attractive for applications because they are easy to conceive, have low losses, and reduce circuit size to achieve a compact resonator. In this paper, we design a slim profile resonator at 13.56 MHz for HF (High Frequency) applications, such as HF RFID (High Frequency Radio-Frequency IDentification) or NFC (Near-Field Communication), and couple it to a resonant loop. The PTE (Power Transfer Energy) with 30 mm between transmitting and receiving coils is enhanced from 0.88% up to 14.6% in HF with adding a compact resonator between the loops.

In electrostatic shielding, previous studies have focused on shielding external electric fields using electrically neutral shielding shells. Here, we consider a new situation in which the electric field generated by the charge on the shielding shell penetrates the shield's interior through the shell's apertures. As a preliminary exploration of this situation, we started with relatively simple yet analytically solvable configurations. Specifically, we focus on configuring a thin-walled conducting spherical shell that is charged and has a circular aperture. For this configuration, we derive a series-form analytical solution for the potential distribution using the method of variable separation and present simplified solutions for the potential and electric-field strength along the central axis. Based on this analytical solution, we analyzed the characteristics of the potential and electric field distributions inside the spherical shell for different aperture sizes and found that, compared with a single aperture, placing two apertures at diametrically opposite positions on the spherical shell can significantly reduce the electric field strength in the region near the center of the sphere.

This study presents an electromagnetic-bandgap (EBG)-integrated rectangular microstrip antenna fabricated on a 0.5-mm-thick polyester Mylar substrate for screening controlled nominal water-addition and nominal iron-powder addition conditions in Andrographis paniculata powder. The sensing structure comprises a rectangular microstrip patch, a rectangular ring stub, and a 7 × 1 transverse-electric (TE)-polarized woodpile EBG array designed for operation at 2.50 GHz. The antenna-to-EBG separation was 10 mm. The fabricated prototype had a measured S₁₁ of -13.94 dB at 2.50 GHz, a 10-dB impedance bandwidth of 2.488-2.512 GHz (0.96%), and a measured gain of 5.16 dBi. Compared with the baseline antenna, the EBG-integrated configuration increased the measured gain by 1.35 dBi. Powder samples were prepared at controlled nominal water-addition and nominal iron-powder addition levels and evaluated using a one-port microwave reflection measurement. At 2.50 GHz, the mean reflected-power response of the EBG-integrated antenna decreased from 0.02667 mW at the nominal 0% water-addition condition to 0.00063 mW at the nominal 100% condition. For the nominal iron-powder addition experiment, the corresponding mean reflected-power response decreased from 0.01954 mW at 0% to 0.00061 mW at 100%. The results are reported as mean±standard deviation from repeated measurements under the controlled setup. The proposed system shows potential as a compact and nondestructive screening platform for controlled herbal-powder conditions. Because water-addition levels were not verified by reference moisture analysis and the iron-powder addition levels were not verified by independent elemental analysis, the results should not be interpreted as quantitative moisture measurements or quantitative iron-concentration measurements. The proposed system is intended for screening controlled nominal iron-powder addition conditions. Future work should establish calibration against reference analytical methods and evaluate independently prepared sample batches measured on different days.

To address the problem of increased electromagnetic mutual coupling caused by multi-antenna integration in compact wireless communication terminals, this study presents a compact four-element, high-isolation, ultra-wideband (UWB), multiple-input multiple-output (MIMO) antenna operating in the 6.5-14 GHz frequency band. The proposed antenna is compact measuring 36 mm×36 mm×1.6 mm. The radiating elements adopt an orthogonally symmetric configuration, with chamfered corners and slot-loading techniques used to enhance impedance matching and broaden impedance bandwidth. To effectively reduce mutual coupling between adjacent elements, a composite decoupling structure is developed, which integrates a non-through isolation slot, embedded metallic patches, and a cross-shaped defected ground structure (cross-DGS). The proposed structure effectively enhances in-band isolation by altering coupling current paths and redistributing surface currents on the ground plane. The results demonstrate that, in the 6.5-14 GHz operating band, the antenna achieves S₁₁ < -10 dB, the adjacent-port isolation (S₂₁) exceeding 20 dB, an envelope correlation coefficient (ECC) below 0.0035, and a diversity gain (DG) close to 10 dB. The proposed antenna combines a compact size, wide operating bandwidth, enhanced isolation, and good diversity performance, providing a potential candidate for compact UWB-MIMO terminals requiring low mutual coupling.

Minkowski's theory is regarded as the classical approach to describing the electromagnetism of uniformly moving objects by elegantly utilizing the format-invariance of Maxwell's equations in inertial reference frames under Lorentz transformations. However, in practice, we often encounter medium with boundaries that accelerate, such as a rotating dielectric disc or a magnetic object. To fully describe the electromagnetic behavior of such a system, we developed Maxwell's equations for a mechano-driven medium system (MEs-f-MDMS). This study expands Minkowski's approach to derive the constitutive equations and boundary conditions for MEs-f-MDMS under the low-speed approximation (v << c), based on which the equations can be properly solved to describe engineering electromagnetism, by considering the coupling among the electric field, magnetic field, and mechanical force field. In practice, mechanical action is not merely passive motion through space but an active source of electromagnetic generation and modulation of electromagnetic fields. Our theory makes it possible to treat electrodynamics by including medium deformation, strain gradients, rotational dynamics, and interfacial contact processes in the full calculation.

This paper proposes a novel algorithm to calculate the ground-loss resistance of a very low-frequency (VLF) T-type antenna array with a ground screen. The near-ground region of the T-type antenna is divided into three zones: ground screen zone, ground screen outer-end zone, and ground screen outer lateral zone. Magnetic-field loss resistance and electric-field loss resistance generated by horizontal top wires and vertical down leads are calculated in all three zones to obtain the antenna's total ground loss resistance. Example calculations show that the results obtained by the proposed method are closer to the measured values than those calculated by the classical Wait-Pope method. The variation law of ground-loss resistance generated in different zones of the antenna site with earth conductivity is analyzed, and valuable conclusions are drawn.

The proposed antenna is a flexible, wearable antenna designed for smart clothing applications, operating in the 2.4 GHz band. To make it truly wearable, we used jeans (denim) fabric as the substrate, with a compact size of 50 × 36 mm² and a thickness of 1 mm. We focused on how the antenna performs when placed on the human body. We tested it using hand and leg phantom models, and the results were excellent. The Specific Absorption Rate (SAR) remained well below the safety limit of 1.6 W/kg - measuring 0-0.345 W/kg on the hand and 0-0.245 W/kg on the leg. We also achieved strong 3D radiation gains of 4.95 and 4.81 dBi. Because clothes naturally fold and move, we also analyzed the antenna's performance under vertical and horizontal bending with 0°, 30°, 45°, and 60°. Graphical analysis confirmed that the antenna remained stable and efficient even when bent, proving that it is a reliable and safe choice for real-world wearable technology.

Waveguide transmission lines are known for their low insertion losses, particularly at higher GHz frequencies. However, they tend to be larger and bulkier than other transmission lines. This study investigates using dielectric-loaded waveguides to reduce the overall size and volume of waveguide-routed systems with the dielectric properties of 3D-printed plastics. Compared to other studies that use dielectric loading for size reduction, this study aims to reduce size, volume, and weight while maintaining relatively low losses. The approach is to use low-loss tangent dielectrics with a suitable dielectric constant responsible for reducing size, volume, and weight. Among 3D-printed plastics, Cyclic Olefin Copolymer (COC) is the most suitable based on its dielectric constant and loss tangent in the order of conventional dielectrics such as PTFE. The measured insertion loss of the 3D-printed dielectric-loaded waveguide was 0.22 dB, comparable to that of air-loaded WR90 waveguides of the same length (0.10 dB), while reducing the cross-sectional area by 46.35% and the weight by 26%. The advantage of 3D printing, dielectric-loaded waveguides is the ability to design less constrained waveguide profiles and intricate routing of waveguide transmission lines due to more flexible fabrication capabilities of 3D printing. Combining the benefits of 3D printing and the dielectric properties of COC, this study demonstrates the use of smaller waveguides in a higher frequency band that would be out of band in their air-loaded medium. By loading the smaller out-of-band waveguide with dielectric, the result shows that longer-wavelength signals, which would not be able to propagate without dielectric loading, can now propagate with low insertion loss. The waveguide chain is also miniaturized with a reduced size and overall volume, which would not have been possible with conventional air-loaded waveguides for a given frequency band, as it propagates below the cutoff frequency.

This paper proposes a high-gain ultra-wideband (UWB) dual-polarized Vivaldi antenna. The proposed antenna consists of two identical Vivaldi elements orthogonally crossed to achieve dual polarization. A tapered stepped-impedance feed matching line combined with a petal-shaped open-slot structure is deployed for every Vivaldi element to enhance impedance matching efficiently and extend operational bandwidth. Furthermore, gradient-tapered curved slots, periodic tapered rectangular slots, and bent extended stubs are arranged on both sides of the radiating patch, which effectively improves the antenna's gain and directivity at mid and low frequencies within its operating bandwidth. The overall dimensions of the proposed antenna are 0.57λ_L × 0.8λ_L, where λ_L refers to the free-space wavelength at the lowest operating frequency. Experimental measurements demonstrate that the proposed antenna achieves an impedance bandwidth of 1.5-9.5 GHz for S₁₁ ≤ -10 dB. The dual-polarization port isolation is higher than 21 dB throughout the operating band, with a peak gain of 11.38 dBi. The antenna can be deployed for wideband communication and radar detection applications.

This paper presents a compact dual-band bandpass filter, based on substrate integrated waveguide (SIW) technology, highlighting independent tuning abilities over center frequencies. Rectangular mushroom resonators (RMRs) are inserted inside an SIW cavity to realize the filtering structure, where two transmission bands are generated, which are centered at 2.4 GHz and 4.35 GHz, respectively by simultaneous employment of TE₁₀₁ and TE₂₀₁ resonant modes. Unlike conventional tunable dual-band filters, which generally exhibit interdependent frequency shifting between the operating bands, the proposed design employs an independent modal-tuning mechanism via selective perturbation of the resonant current paths. In the proposed methodology, radial and linear perturbation slots are strategically introduced at locations derived from modal electric field and surface current analyses to selectively modify the effective electrical length of separate resonant modes. One mode can be shifted without producing noticeable influence on the other by properly orienting these perturbation elements and thereby enabling isolated control of each passband while preserving the original cavity geometry. To obtain practical dual-band bandpass filtering performance cascaded RMR-loaded SIW resonators are configured into a highly selective filter topology. Metallic radial perturbation shafts are incorporated into the resonator structure to facilitate dynamic adjustment of slot exposure for real-time and post-fabrication tuning. Experimental verification confirms independent tuning of the lower passband from 2.0 GHz to 2.2 GHz, corresponding to around 9.5% frequency shift, while maintaining the upper band unchanged. Similarly, the upper passband is independently shifted from 4.0 GHz to 4.1 GHz, yielding close to 2.5% tuning range without affecting the lower band. The filter retains insertion loss under 2 dB over the full tuning range while exhibiting negligible compromise in passband selectivity. With its compact structure, low-loss characteristics, and independently reconfigurable capability, the proposed design is well suited for adaptive multiband microwave and wireless front-end implementations.

This paper describes various aspects of the analysis of a technique for measuring the dielectric constant and loss tangent using a cylindrical dielectric resonator in a closed metal cavity. The resonator's TE_01δ resonant mode mode was selected as the measurement target. The clear electric and magnetic field patterns inside the dielectric resonator are provided from a theory derived by improving a very simple field model. Resonant frequencies under different dielectric constants are studied. All the possible sources of the conducting dissipation are investigated to improve the accuracy of the loss tangent measurement. The influence of the energy storage factor on the calculation of loss tangent measurement is investigated, too. This cavity is also used for measuring complex permittivity over a sweeping frequency range, and the accuracy as well as the limitations of its swept-frequency capability are discussed. The improved field model is compared with the primitive one through experimental measurements.

To overcome the limitations of displacement sensors in six-pole radial active magnetic bearing (AMB) systems, such as large installation space and low reliability, this paper proposes a physics-enhanced long short-term memory (PhyLSTM) method for rotor displacement self-sensing. Firstly, a mathematical model is derived, and system feasibility is demonstrated. Then, the PhyLSTM network is developed to learn the dynamic mapping from three-phase control currents to rotor displacement. Multiple physical mechanisms, including rotor dynamics, gyroscopic coupling, and eddy-current effects, are incorporated into the loss function, thereby unifying data-driven learning with physical laws. As a result, high-accuracy prediction through the whole rotor motion process is achieved with reduced computational cost. Thirdly, a simulation system is established to evaluate the proposed method under startup, disturbance, and uncertain initial-position conditions, and the results verify the strong generalization capability of PhyLSTM. Finally, experiments of startup, steady-state suspension, acceleration, and anti-disturbance are conducted. Compared with the baseline method, PhyLSTM limits the maximum prediction error to 9 µm and reduces the error by 55.0%, demonstrating accurate rotor displacement prediction and enhanced robustness and reliability of the AMB system.

Bidirectional wavefront control requires metasurfaces that encode distinct responses in opposite propagation directions. Ferrite films possessing nonreciprocity at terahertz frequencies are crucial for bidirectional control; however, they are difficult to pattern. We address this materials-fabrication mismatch by one-step, resist-free femtosecond direct laser writing (DLW), which directly transforms continuous low-loss lanthanum-doped yttrium iron garnet (La:YIG) films into freeform nonreciprocal metasurfaces. This approach sculpts complete nonreciprocal metasurfaces (NRMs) with meta-atoms in a wide variety of prism geometries, including hexagonal, oval, rectangular, and pentagonal forms, directly in the film. By reconfiguring gyrotropic resonances of each element, we demonstrate precise nonreciprocal control of THz beams through unidirectional transmission, bidirectional beam focusing, and holographic imaging. This streamlined fabrication strategy dramatically lowers the barrier to NRM research and broadens its applicability across several scientific fields.

This research develops an innovative, compact, and efficient antenna for IoT devices that guarantees reliable wireless communication across various frequency bands. We propose a new three-element, fork-shaped multiband antenna design for multiband operation and higher isolation between the radiating elements. Split-Ring Resonators (SRRs) are implemented to enhance the antenna's electromagnetic performance and isolation between the radiating elements. The antenna design is realized using an FR-4 substrate with dimensions of 40×35×1.6 mm³. Simulation results show the presence of five resonance frequencies: 3.17 (3.13-3.20), 3.74 (3.62-4.2), 4.90 (4.4-5.91), 5.39, and 6.84 (6.11-7.23), 7.91 (7.76-8.06) GHz with reflection coefficients -10.78, -20.21, -18.04, -16.49, and -26.27 dB, respectively. Using resonating elements enhances electromagnetic field confinement and provides isolation between the radiating elements. The fabricated prototype shows good agreement between simulated and measured results. The maximum gain of the proposed antenna is 3.79 dB, and the radiation efficiency ranges from 66% to 94%. These findings confirm that the proposed antenna, owing to its compact dimensions, multiband characteristics, and favorable electromagnetic performance, is a promising candidate for IoT-based wireless communication applications.

Magnetically Coupled Resonant (MCR) Wireless Power Transfer (WPT) systems suffer power-transfer efficiency (PTE) degradation due to misalignment of the transmitter/receiver coil pair across multiple degrees of freedom (DOF) simultaneously. Previous methods track lateral offset or rotational drift individually; none have reported correcting combined lateral, vertical, and angular misalignment in real time. The proposed hybrid physics-machine learning model combines an analytical model for a mutual-inductance circuit with a trained feedforward-network (FFN) residual-correction layer to estimate the state of the matching network that produces a maximum PTE when there is simultaneous 3-DOF misalignment. The method is evaluated for a representative 6.78 MHz, 3-turn, 40 mm-diameter coil pair, using a numerical electromagnetic model (Neumann-integral mutual inductance evaluation), and an exact model of a series-series (S-S) resonant circuit. The value of the nonlinear cross coupling term between lateral and tilt that is neglected by a separable analytical model increases by ~18% to 79% of the true value of the mutual inductance as misalignment increases, and the value of a learned correction increases strongly with the size of the disturbance. Similarly, the single axis baseline has an average efficiency gap from the optimal (1.30 percentage points), which is only 49% closed by using the extended analytical model, and 89% closed with the trained residual layer. The shallow FFN is shown to be better for this correction than the degree-2 polynomial ridge regressor in an ablation. It is also observed that the carrier-frequency retuning has a very small impact on the efficiency in this topology, with the state of the matching network being the major lever. A warning, however, is that the correction may sometimes make the worst-case deficit worse at the corners of the envelope where there are fewer samples, meaning that the samples have to be denser, or an extrapolation safeguard needs to be included before deployment.