Search Results (547)

In this paper, we propose a novel high-shielding-effectiveness frequency-selective rasorber (HSE-FSR) that combines the advantages of a frequency-selective rasorber (FSR) and an energy-selective surface (ESS). The proposed HSE-FSR contains two layers—a lossy layer that implements a conventional FSR for stealth performance and an ESS layer for high-power beam shielding effectiveness (SE)—both of which employ PIN diodes as switchable components. However, PIN diodes can be severely damaged by high-power microwave (HPM) beams or experience other electromagnetic compatibility issues causing elevated currents to flow into them. To maintain SE performance after an eventual PIN diode failure, we added shape-memory alloy (SMA) components in the ESS layer as a backup. This characteristic, combined with a 30 dB SE level, is representative of high shielding effectiveness (HSE). As a result, the HSE-FSR contains three working modes: FSR, shielding and absorbing (SA), and HSE. Notably, the proposed HSE–FSR possesses polarization-independent switching capability for the FSR mode. After a careful design process carried out with commercial electromagnetic software, numerical simulations are performed to validate the overall methodology. The obtained results confirm the approach’s effectiveness and show that the proposed HSE–FSR has better stealth and SE performance than the current state-of-the-art. Full article

Satellite solar panel inherently produce strong radar echoes and cause secondary electromagnetic pollution due to their highly reflective nature. To solve this, an optically transparent metamaterial absorber (OTMMA) is constructed using the solar panel as the substrate. The proposed multilayer structure consists of a patterned indium tin oxide (ITO) layer, a transparent polymethyl methacrylate (PMMA) spacer, and the solar panel itself. In the 8–18 GHz range, the design achieves over 90% absorptance while maintaining an average visible transmittance of approximately 73%. More importantly, the reflection shielding effectiveness (SE_R) is reduced from over 15 dB to below 3.01 dB, successfully shifting the shielding mechanism from reflection-dominated to absorption-dominated. Benefiting from this conversion, simulations under normal-incidence and x-polarized conditions demonstrate that the monostatic radar cross section (RCS) of a finite plate is significantly suppressed, achieving a reduction of more than 10 dB across the operating band, with a peak reduction of 20.43 dB at 10.7 GHz. This transforms satellite solar panel from a harmful “electromagnetic pollution source” (strong reflector) into a “functional surface for electromagnetic purification” (optically transparent metamaterial absorber). Full article

Cylindrical shields are worthy of a specific investigation because of their diffusion in practical applications and of the analytical and numerical peculiarities. Main applications are related to cables, electromedical machines, drones, and others. The general case of finite-length, penetrable shields with and without apertures is addressed. The results obtained by means of a frequency-domain integral equation model (solved by means of a Method of Moments procedure) are used to infer general considerations in the absence of apertures and to validate the predictions ensuing from a numerical commercial code. The semi-analytical formulation is also useful for a rapid tuning of shield design. Approximate expressions available in the literature are also used for comparison and validation. In this way, the external field sufficient to impair the functionality of electronic devices protected by complex three-dimensional cylindrical enclosures may be easily estimated under the assumption of linearity of the shielding materials. Full article

Electromagnetic interference (EMI) poses increasing challenges for compact electronic systems and emerging 5G/6G technologies, driving demand for Electromagnetic (EM) absorbers that are lightweight, low-cost, and environmentally sustainable. Conventional absorbers rely on ferrites, magnetic nanomaterials, and multi-step chemical synthesis, all of which consume energy and raw materials, involve hazardous reagents, and generate waste streams of their own. This study shows that two abundant waste streams, recycled tire particles (TP) and crushed glass (CG), can be converted into effective microwave-absorbing composites when combined with activated carbon (AC) in a poly(vinyl acetate) (PVAc) matrix through simple mechanical processing. The microstructure of the composites was examined via scanning electron microscopy (SEM), revealing systematic changes in surface texture, filler dispersion within the polymer matrix, and pore structure with increasing filler content. The complex permittivity, AC conductivity ($\sigma$), and loss tangent (tan $\delta$) of the composites were determined from 0.2 to 20 GHz using an open-ended coaxial probe and correlated with their morphology. Dielectric loss was highest where the filler formed a continuous conductive network and decreased once an open pore structure developed, diluting the effective permittivity. Absorption-dominated EMI shielding was evaluated for metal-backed single layers using transmission-line (TL) theory, validated by full-wave simulations in Ansys HFSS. Pure AC composite absorbed weakly at the $\lambda /4$ condition but reached −13.5 dB at the $3\lambda /4$ resonance. Incorporating waste-derived fillers improved its microwave absorption performance. At a thickness of 6 mm, the AC–TP composite (ACTP3) achieved a minimum reflection loss of −39.07 dB at 15.75 GHz, while the AC–CG composite (ACCG1) reached −29.4 dB at 16.75 GHz. These results demonstrate that strong absorption-dominated EMI shielding can be achieved using waste-derived carbon/polymer composites fabricated through simple mechanical processing. The approach offers a scalable and sustainable route to EMI shielding materials that avoids magnetic metals, nanomaterials, and chemical synthesis, while diverting industrial and post-consumer waste from landfill. Full article

This paper estimates the total electromagnetic load in the passenger compartment. A computational model is proposed based on the numerical solution of Maxwell’s equations and the specular reflection method for near-field emitters, accounting for the shielding properties of the metal body and attenuation through the glazing apertures. Theoretical calculations and field measurements were performed using a spectrum analyzer (Narda NBM-550) and isotropic probes over the frequency range from 10 Hz to 3 GHz during various operating modes of the power plant and auxiliary electrical equipment. The comprehensive measurement campaign utilized two complementary metrological systems to cover the entire spectrum: a dedicated Narda EHP-50F isotropic analyzer was deployed for the low-frequency domain (10 Hz–100 kHz), while high-frequency electromagnetic and radiofrequency components (100 kHz–3 GHz) were acquired using a Narda NBM-550 broadband field meter equipped with isotropic electric (EF-0391) and magnetic (HF-3061) probes. The maximum low-frequency magnetic induction (B max = 2.4 μT) was recorded near the driver’s pedal unit and the engine shield, attributable to generator field leakage and ignition-system transients. In the high-frequency range (2.4 GHz), resonant effects of the metal body caused standing-wave interference nodes, producing electric field strength peaks of 8.5–9.5 V/m. Although the recorded field parameters are within the limits specified by ICNIRP and national sanitary standards, they pose a chronic exposure risk to drivers traveling long distances. Design recommendations are proposed to optimize the wiring topology and local shielding. Full article

Herein, high-entropy ferrites (HEFs) represent a transformative frontier in solid-state chemistry and materials physics, shifting design paradigms from conventional mono- or co-substituted ceramics toward multi-component, single-phase solid solutions. Stabilized by a massive configurational entropy (ΔS_conf > 1.5 R), these systems incorporate five or more principal cations into a single crystalline matrix, such as cubic spinel (Fd$\overline{3}$m), perovskite, or hexagonal structures. This comprehensive review systematically evaluates recent breakthroughs in HEF design, tracing the continuous lineage from advanced synthesis methodologies, including modified Pechini sol–gel and hydrothermal routes, to local coordination environments and macroscopic functional expressions. We detail how intense local lattice distortions and polyhedral buckling alter metal–oxygen ligand bond parameters, disrupting traditional collinear A-O-B superexchange pathways to induce quantum magnetic frustration, low-temperature spin-glass behavior, and spontaneous exchange bias effects. Beyond fundamental physics, this work highlights the multi-cation “cocktail effect” across cutting-edge applications, emphasizing its role in high-frequency electromagnetic interference (EMI) shielding, multi-redox heterogeneous catalysis, and high-capacity electrochemical energy storage. Finally, we address current computational bottlenecks in Density Functional Theory (DFT+U) simulations and propose a roadmap for accelerating phase stability predictions and magnetic footprint tuning through the integration of high-throughput workflows and closed-loop, data-driven machine learning architectures. By bridging the gap between thermodynamic theory and targeted application, this review provides a foundational framework for the next generation of entropy-stabilized functional devices. Full article

Magnetic field ripple in the audible-frequency range can induce magnetostriction in ferromagnetic components, causing vibration and noise even in non-rotating systems such as electric vehicle battery systems. Magnetic shielding can reduce such excitation; however, shielding materials used in this range are generally ferromagnetic and may themselves undergo magnetostriction, potentially degrading NVH performance. Therefore, magnetic shielding materials should provide effective field attenuation while suppressing their own vibration to improve system-level NVH performance. In this study, a magnetic shielding test setup and an electromagnetic finite-element model were developed. The electromagnetic model was compared with experimental plate-shield measurements and subsequently used for comparative investigations of the effects of shielding configuration, open-area ratio, and thickness, while the associated NVH performance was evaluated experimentally. A mesh-type structure with a continuous magnetic flux path achieved shielding performance comparable to that of a plate-type structure. Experiments using a 0.635 mm steel-wire mesh provided a magnetic shielding effectiveness of approximately 3.73 dB at 3 kHz and reduced the target vibration component at 6 kHz by 55.8% and system noise by 5 dB. These results demonstrate that mesh-type magnetic shielding can attenuate audible-frequency magnetic field ripple while improving system-level NVH performance, indicating potential application to electric vehicle battery systems and other electromagnetic systems. Full article

This study presents a compact navigation electronic seal system employing the Iridium SBD9603 radio modem and a specialized antenna for transmitting Short Burst Data (SBD) messages. The primary objective was to integrate a satellite antenna within the constrained space of the device enclosure. Due to the impossibility of the manufacturer-recommended horizontal antenna placement, the antenna was installed at a 70° angle. Experimental results confirmed the feasibility of this configuration. In open-space conditions, a stable signal level sufficient for communication was observed 88.6% of the time, while inside a protective enclosure made of PA12 + GF composite material, this value decreased to 65.3%. The average data packet delivery time ranged from 8 to 14 s. These results are explained by the dielectric properties of the enclosure material and partial signal shielding. At the same time, short-term signal fading (on average up to 43 s) was considered acceptable, since a typical SBD transaction takes less than 10 s, allowing efficient use of message retransmission. An important finding of the study is that when the seal is mounted on a steel container door, the inclined antenna performs more efficiently than the horizontal configuration (65.3% versus 61.1%). This effect is attributed to the metallic surface acting as a reflective screen, optimizing the electromagnetic conditions for the inclined antenna aperture. The obtained results can be applied in remote monitoring and identification systems for cargo transported in containers and trucks, including operation under challenging environmental conditions. Full article

The increasing demand for high-frequency electronic and communication systems has intensified the need for lightweight and efficient electromagnetic interference (EMI) shielding materials. In this study, the conventional oxide mixing method was used to form kaolinite-chopped strand composites. Natural kaolinite powder was calcined at 450 °C for 4 h to remove volatile and organic components before composite fabrication. Kaolinite/chopped-strand epoxy composites were fabricated and evaluated for their microwave shielding effectiveness in the 0–4.4 GHz frequency range. Composites with different kaolinite-to-chopped-strand weight ratios were prepared using a controlled mixing and molding process to obtain thin specimens with a uniform thickness of 1.4 mm. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used primarily to characterize the kaolinite powder. Because composite-level mapping was not performed, the uniformity of filler dispersion is interpreted cautiously. Microwave shielding effectiveness was measured using a two-port vector network analyzer (VNA). The composite containing 80 wt.% kaolinite and 20 wt.% chopped strands showed the highest shielding performance, with a maximum total shielding effectiveness of 21.57 dB at 0.58 GHz. The observed shielding behavior is consistent with absorption-dominated attenuation supported by S-parameter-derived reflection, transmission, and absorption trends. This can arise from polarization losses and interfacial charge accumulation in heterogeneous dielectric composites. The results indicate that kaolinite/chopped-strand epoxy composites are low cost and sustainable materials for broadband microwave shielding applications. Full article

In electrodynamic suspension (EDS) maglev systems, the time-varying magnetic fields experienced by onboard superconducting magnets can induce excessive AC losses and elevate the risk of quench, posing a critical threat to operational reliability. Conventional three-dimensional finite element analysis, though accurate, requires hours per frequency point and cannot support real-time quench assessment or parametric design optimization. This paper proposes an efficient magnetic shielding analysis method based on a reflection–absorption decoupled lumped-parameter framework. The three-dimensional eddy current field is reduced to a low-order coupled system by decomposing the eddy currents into plate-surface modes, a global circulation loop, and side-wall contributions, all coupled through a unified series magnetic circuit, while the field penetration through the cavity wall is captured via a finite impulse response (FIR) diffusion kernel with a high-frequency correction. The proposed method achieves a simulation time of 3–5 s per frequency point, a speedup of approximately ${10}^3$∼${10}^4$ over finite element analysis, with a root-mean-square shielding effectiveness deviation of 2.03 dB over 10–3000 Hz. The efficiency of the proposed method enables co-optimization of the outer dewar and superconducting magnets, offering a practical analysis tool for quench mitigation and electromagnetic compatibility design in EDS maglev systems. Full article

Piezoelectric sensors convert electric charge in response to mechanical loading and are widely studied for their high sensitivity. In particular, ferroelectret sensors provide the flexibility and material system design that enable biocompatibility. Insole-based gait and pressure sensing remain active research topics, yet most published electronics are limited to conceptual diagrams without practical strategies for noise mitigation or robustness against electromagnetic interference (EMI). Therefore, this work presents a compact, four-channel portable measurement system specifically designed for charge-based force sensing with piezoelectric sensors, called ChrisBox. A comprehensive shielding strategy, including both the circuit board and the sensor connection, via cost-effective USB Type-C cables is implemented. Performance was validated by comparing the output of the developed electronics with a calibrated electrometer under defined mechanical loads applied to a shielded ferroelectret sensor. The system measured the charge with a relative deviation of 8.2%, partly attributed to variability in the verification setup, with a high linearity of R² > 0.99. In controlled EMI testing within a transverse electromagnetic (TEM) cell, noise levels remained below 0.1 pC RMS, enabling a signal-to-noise ratio (SNR) of 53 dB for a measured charge of 43 pC RMS during human pulse measurement with a ferroelectret. The results confirm the system’s suitability for portable, high-resolution ferroelectret sensing in EMI-prone environments and provide a foundation for further application-specific development. Full article

Composites based on biodegradable polymers are attractive replacements for metallic electromagnetic interference (EMI) shields, but their performance is limited by nanofiller agglomeration. In poly(lactic acid)/poly(butylene succinate) (PLA/PBS) composites reinforced with carbon fiber (CF), unmodified ZnO nanoparticles agglomerate above 1 wt %, severely embrittling the material. In this study, ZnO nanoparticles were coated with poly(ethylene glycol) (PEG, 8 kDa) by solution adsorption and incorporated at 0.5–2 wt % into PLA/PBS (80/20) containing 20 wt % CF. FTIR showed a +14 cm⁻¹ shift in the ether C–O–C band (1093 → 1107 cm⁻¹), consistent with adsorption of PEG on the ZnO surface. Fracture surfaces showed uniform sub-micron dispersion, in contrast to the dense interfacial clusters formed by unmodified ZnO at the same loading. At 1 wt % PZ, the composites combined 76.3 MPa tensile strength and 2.35% strain with 71 dB X-band shielding effectiveness, more than three times the 20 dB commercial requirement. The highest shielding, 89 dB, was reached at 1.5 wt %, with absorption contributing more than 90% of the total. Unmodified ZnO required about five times this loading to reach comparable shielding. Full article

As a disruptive technology to overcome the bottlenecks of conventional mechanical excavation and blasting, microwave-assisted rock fragmentation demonstrates tremendous potential in deep geo-resource development and extreme-environment engineering. This paper presents a comprehensive review of the latest advances in this field, thoroughly dissecting the electromagnetic–thermal–mechanical–chemical (THMC) multi-field coupling mechanisms governing microwave–rock interactions. Particular emphasis is placed on elucidating the mechanisms of thermal stress fracturing, phase-transition expansion, and thermo-chemical coupling damage triggered by mineral dielectric heterogeneity. The nonlinear effects of microwave radiation parameters, intrinsic rock properties, and complex in-situ stress environments on fracturing efficiency are rigorously analyzed, and precision multi-scale characterization methodologies—from macroscopic mechanical degradation to microscopic fracture networks—are comprehensively summarized. Building upon this foundation, the paper critically evaluates the current engineering application status and electromagnetic safety shielding challenges of this technology in frontier scenarios, including microwave-assisted tunnel boring machines (TBM), intelligent mineral sorting, deep unconventional oil and gas fracturing, and space in-situ resource utilization (ISRU). Finally, the limitations of existing research regarding cross-scale effects, high-temperature and high-pressure in-situ testing, and dynamic intelligent control are identified, and future development pathways oriented toward multi-source data fusion and adaptive power modulation are prospected, aiming to provide robust theoretical support and forward-looking guidance for the cross-scale engineering transformation of microwave rock-breaking technology. Full article

Fiber-reinforced polymer composites are attractive multifunctional material systems for aerospace, defense, and transportation because of their low density, high specific mechanical properties, and tailorable electromagnetic response. This study comparatively evaluated the effects of fiber system, thermoset matrix, and hybridization on the mechanical, thermomechanical, and electromagnetic behavior of Coremat interlayered sandwich composites containing carbon, glass, and aramid fabrics with polyester, vinylester, and epoxy matrices. Eighteen configurations were fabricated by hand lay-up and evaluated by tensile, three-point bending, heat deflection temperature (HDT), Vicat softening temperature (VST), and two-port S-parameter measurements over 4–40 GHz. The carbon/epoxy configuration exhibited the highest tensile strength (231.2 MPa), whereas the glass/vinylester configuration showed the highest flexural strength (160.5 MPa), HDT (128.0 °C), and VST (132.7 °C). The relatively low standard deviations across the tested configurations indicated consistent experimental repeatability and limited within-configuration dispersion. Carbon-containing systems strongly suppressed electromagnetic transmission; however, the single carbon systems were predominantly reflection driven. The carbon/glass polyester hybrid S10 provided the highest total shielding effectiveness (38.45 dB) at an overall laminate thickness of 3.30 mm, corresponding to a normalized shielding effectiveness of 11.65 dB/mm, while the carbon/aramid epoxy hybrid exhibited the highest incident-power absorption ratio (22.4%) together with very low transmission (0.22%). Overall, the results show that fiber system, matrix type, and hybrid architecture should be selected jointly when balancing structural, thermomechanical, and electromagnetic requirements. Full article

In this work, flame-retardant (FR) PLA-based composites exhibiting both good flame retardancy and electromagnetic interference (EMI) shielding were fabricated through combining melt blending with fused deposition modeling (FDM) 3D printing. Intumescent flame-retardant (IFR) fillers and graphene nanoplatelets (GNPs) were incorporated to construct a synergistic system, and the resulting structure–property relationships were systematically investigated. The optimal performance was achieved with 15 wt% IFR fillers and 3 wt% GNPs. The prepared composite exhibited a residual char yield of 14.3% at 700 °C, significantly higher than that of neat PLA. Regarding flame retardancy, the limiting oxygen index (LOI) increased to 32.5%, and the vertical burning level achieved a UL-94 V-0 rating. In the cone calorimetry test, both the peak heat release rate and total heat release were markedly reduced, attributed to the formation of a dense and stable char layer. For EMI shielding, the FR composite achieved a total shielding effectiveness (SE_T) of 20.6 dB in the X-band, with an absorption proportion exceeding 80%, indicating an absorption-dominated mechanism. Meanwhile, a well-established conductive network effectively enhanced the electromagnetic loss. Overall, the synergistic effect of IFR fillers and GNPs enabled simultaneous improvements in flame retardancy and EMI shielding in FR PLA-based composites, providing a feasible strategy for designing functional 3D-printed FR PLA-based materials. Full article