Effective Electromagnetic Research Articles

Assessing the electromagnetic shielding effectiveness of coconut coir composites with varying iron particle concentrations

This study investigates the electromagnetic shielding effectiveness of Coconut Coir-based Porous Carbon (CCPC) composites with varying iron (Fe) particle concentrations, specifically focusing on four different weight ratios of CCPC/Fe-80, CCPC/Fe-60, CCPC/Fe-40, and CCPC/Fe-20. The novelty of this work lies in the use of sustainable coconut coir as a base material, emphasizing its eco-friendly and cost-effective attributes for Electromagnetic interference (EMI) shielding applications. The significance of varying iron particle concentrations is highlighted to optimize electromagnetic shielding effectiveness. Comprehensive analyses were conducted on these composites. X-Ray Diffraction (XRD) analysis confirmed the presence of crystalline Fe particles and amorphous carbon, with crystalline sizes determined via Williamson-Hall (W-H) plot, Scherrer Equation, and Strain Size Plot (SSP) ranging from 17.33 nm to 18.01 nm for the former. Raman spectroscopy revealed distinctive D and G bands, with intensity ratios indicating a slight increase in structural disorder with higher Fe content. UV-Visualization spectroscopy demonstrated distinct absorption peaks, with higher Fe content resulting in more pronounced absorbance and lower band gap energies. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDS) analyses provided detailed insights into the material's microstructure and elemental composition, confirming the successful integration of Fe particles within the porous carbon matrix. Vector Network Analyzer (VNA) testing measured the reflection loss (RL), showing values in the range of −26.4 dB to −20.2 dB, for 2 mm thick samples, corresponding to electromagnetic wave attenuation of over 99%. These results underscore the potential of CCPC/Fe composites, particularly in applications requiring effective Electromagnetic (EM) wave attenuation. This research offers a sustainable and cost-effective solution, contributing significantly to the field of materials science by enhancing electromagnetic compatibility in various technological applications.

Investigation on high EMI shielding effectiveness and shielding mechanism of spherical Ti3C2Tx microfilm prepared by spray-freezing

Due to the explosive growth of the number of miniature electronic devices in the 5 G era, higher requirements have been raised for electromagnetic pollution protection materials. The production of effective electromagnetic (EM) interference (EMI) shielding materials is still challenging. In this research, Ti3C2Tx microspheres were successfully synthesized by the self-developed spray freezing technology and 43 µm-thick spherical Ti3C2Tx microfilm was prepared by vacuum filtration. The spherical film can block 5 G communication signals and its EMI shielding effectiveness (SE) is 51 dB, which is 50% higher than that of the 2D Ti3C2Tx film of approximately the same thickness. Additionally, the effects of transmitting X-band EM waves through a 43 µm-thick spherical Ti3C2Tx sheet were simulated employing Comsol Multiphsics. It is found that an annular current traveling perpendicular to the direction of electromagnetic wave propagation will be induced in the spherical Ti3C2Tx, which leads an extra larger EM loss. This discovery provides a novel avenue for the structural design of EMI shielding materials.

Frequency tunable Ni–Ti‐substituted Ba–M hexaferrite for efficient electromagnetic wave absorption in 8.2–75 GHz range

The development of 5G telecommunication technology has seen a high demand for effective electromagnetic (EM) wave absorbers in the millimeter wave (mmWave) band. Because hexagonal M‐type ferrite is known to have high ferromagnetic resonance (FMR) in the 5G band frequency, it has attracted significant attention as a mmWave absorber. However, study of the relationship between magnetocrystalline anisotropy, FMR frequency, and EM wave absorption performance in the mmWave band remains insufficient. In this study, Ni–Ti‐substituted M‐type barium ferrite (Ba–M ferrite) was synthesized using the citrate sol–gel method, and the change in the magnetic properties caused by Ni–Ti substitution was analyzed. The complex permittivity, permeability, and reflection loss (RL) of the Ni–Ti‐substituted Ba–M ferrite composites in the 8.2–75 GHz broadband frequency range were also studied. The EM wave absorption frequency, which is governed by the FMR frequency, could be tuned by controlling the amount of substituted Ni–Ti ions in the Ba–M ferrite. The prepared EM wave absorber exhibited excellent EM wave absorption properties with an RL of −52 dB at 29.5 GHz and a matching thickness of 0.95 mm. This study provides insights into a frequency‐tunable EM wave absorber with enhanced absorption properties, attained by changing the magnetic properties of Ni–Ti‐substituted M‐type hexaferrites in the mmWave frequency band.

Radar absorption characteristics of ceramic oxide fiber/aluminosilicate-sendust composite structure at ultrahigh temperatures

This study proposes a novel radar-absorption structure (RAS) composed of Nextel 601 fiber and a geopolymer-based aluminosilicate matrix for withstanding high temperatures and providing effective electromagnetic (EM) absorption performance. To measure its complex permittivity and permeability in the X-band frequency range, we dispersed flake-type sendust particles with different sizes and contents in the matrix. The complex permittivity increased with increasing size and content of the sendust particles, which was attributed to the increase in dielectric polarizations and electrical conductivity of the composites. Furthermore, the simulation studies of the designed RAS showed excellent EM absorption performance, with a thickness of 4.25 mm, revealed a maximum return loss (RLmax) of −24 dB with a broad absorption bandwidth (BW @ −10 dB) of 8.3 GHz at room temperature (RT). Similarly, the measurement of fabricated RAS exhibited a RLmax of −19.2 dB and a broad absorption BW of 5.45 GHz at RT in the S- and X-band frequency range (6.95–12.4 GHz). However, in X-band measurements conducted at elevated temperatures, the RLmax values declined, reaching −8.04 dB at 9.87 GHz and −10.97 dB at 9.45 GHz observed at 900 °C and 1200 °C, respectively. This decrease in EM absorption performance can be ascribed to variations in impedance matching conditions arising from factors such as dielectric and magnetic losses, as well as shifts in frequency. In addition, the significant RCS reduction of the proposed RAS indicates its applicability to hypersonic aircraft.

Regulated electron migration in sandwich-like m-Ti3C2/Fe3O4 composites derived from electrostatic assembly boosted electromagnetic wave absorption

Sandwich-like m-Ti3C2/Fe3O4 composites derived from electrostatic assembly exhibit highly effective electromagnetic (EM) wave absorption capacity. We demonstrate the influence of regulating electron hopping behaviors on EM characteristics and absorption performance.

Activated Carbon Derived from Carbonization of Kevlar Waste Materials: A Novel Single Stage Method.

The augmented demands of textile materials over time have brought challenges in the disposal of substantial volumes of waste generated during the processing and end of life of such materials. Taking into consideration environmental safety due to discarding of textile waste, it becomes critical to recuperate useful products from such waste for economic reasons. The present work deals with the preparation of porous and electrically conductive activated carbon fabric by a novel single stage method of simultaneous carbonization and physical activation of Kevlar feedstock material procured from local industries, for effective electromagnetic (EM) shielding applications. The Kevlar fabric waste was directly carbonized under a layer of charcoal without any intermediate stabilization step at 800 °C, 1000 °C, and 1200 °C, with a heating rate of 300 °C/h and without any holding time. The physical and morphological properties of the activated carbon, influenced by carbonization process parameters, were characterized from EDX, X-ray diffraction, SEM analysis, and BET analysis. Furthermore, the electrical conductivity was analyzed. Finally, the potential application of the activated material for EM shielding effectiveness was analyzed at low (below 1.5 GHz) and high (2.45 GHz) frequencies. The phenomena of multiple internal reflections and absorption of electromagnetic radiations was found dominant in the case of activated carbon fabric produced at higher carbonization temperatures.

A review on efficient electromagnetic interference shielding materials by recycling waste-a trio of land to lab to land concept.

The materials used in electrical and electronic applications have great importance and broader applications, but they have severe electromagnetic interference (EMI). These materials have extensive applications in broadcasting, medical industries, research, defence sectors, communication and similar fields. The EMI can be addressed by using effective EMI shielding materials. This review presents a detailed, comprehensive description for making electromagnetic interference shielding material by recycling various wastes. It starts with highlighting the overview of electromagnetic interference shielding (EMI) and its theoretical aspects. It provides a comprehensive and detailed understanding of recent trends in the novel approaches towards fabricating EMI shielding from industrial waste, agricultural waste and other miscellaneous wastes. This paper critically reviews the works related to the recycling of wastes like red mud (waste from the aluminium refining industry), ground tyre rubber, tea waste (biowaste) from tea industries, bagasse (waste from sugar cane industry), peanut and hazelnut shells (agricultural waste), waste tissue paper and polyethylene and other miscellaneous wastes like hydrocarbon carbon black and ash for the fabrication of highly effective electromagnetic (EM) interference shielding materials. Highly effective results have been reported using red mud showing maximum efficiency of 51.4 dB in X-band range, various agricultural waste displaying reflection loss of up to - 87.117 dB (in the range 0.01 to 20 GHz) and miscellaneous waste giving EMI SE of 80 dB in X-band frequency. A separate section is dedicated to emphasizing future work and recommendations.

Phase Compensation Technique for Effective Heat Focusing in Microwave Hyperthermia Systems

In this paper, effective electromagnetic (EM) focusing achieved with a phase compensation technique for microwave hyperthermia systems is proposed. To treat tumor cells positioned deep inside a human female breast, EM energy must be properly focused on the target area. A circular antenna array for microwave hyperthermia allows EM energy to concentrate on a specific target inside the breast tumor. Depending on the cancerous cell conditions in the breast, the input phases of each antenna are calculated for single and multiple tumor cell locations. In the case of multifocal breast cancer, sub-array beam focusing via the phase compensation technique is presented to enhance the ability of EM energy to concentrate on multiple targets while minimizing damage to normal cells. To demonstrate the thermal treatment effects on single and multiple tumor locations, the accumulation of the specific absorption rate (SAR) parameter and temperature changes were verified using both simulated and experimental results.

A compact wideband metamaterial absorber for Ku band applications

A compact wideband metamaterial absorber (MA) for Ku band applications is presented in this paper. Ku band is a part of a microwave frequency spectrum ranging from 12 to 18 GHz. The proposed MA absorbs incident wave from 11.39 to 20.15 GHz with a bandwidth of 8.76 GHz which fully covers the Ku band. The proposed structure is compact having an overall dimension of 10 mm $$\times$$ 10 mm. The structure is fabricated on the $$FR_{4}$$ substrate and the simulated result is carried using ANSYS HFSS 19.1. The absorption mechanism is illustrated by calculating effective electro magnetic (EM) parameters ( $$\epsilon _{eff}$$ & $$\mu _{eff}$$ ). Current distribution is also plotted in support of absorption mechanism. The structure is also examined at different angles ( $$0^0$$ – $$90^0$$ ) for the oblique and normal incident. The proposed MA is tested inside the Anechoic Chamber and it was found that simulated and measured result is close to each other with variation within the tolerance limit. At last comparison of the proposed MA is done with already reported MA. MA presented in this paper finds applications for satellite communication radar surveillance and other defense applications.

Computational Study and Experimental Verification of the Effective EM Properties of a Particle-Matrix Composite

We present a simulation of the effective electromagnetic (EM) parameters of a carbonyl iron (CI) powder - polyurethane (PU) composite based on a realistic micrometer-level 3-dimensional model by fractions. CI particles, 10 × 10 × 10, were randomly modeled in a PU matrix, and the optimized meshing condition was adapted to simulation. The calculated effective complex permittivity and permeability were compared with the classical mixing formulas and measurements of prepared CI-PU samples to verify the simulation results. Studies of the local EM field distribution and a parametric analysis of the composite revealed how the randomly distributed particles behaved differently than periodic particles. This study shows the possibility of designing a composite material based on a full-wave simulation.

Preparation of cobalt sulfide nanoparticles wrapped into reduced graphene oxide with tunable microwave absorption performance

Great improvements for wireless techniques and electronic devices require effective electromagnetic (EM) absorbing materials to solve EM radiation and interference problems. Herein, cobalt sulfide/reduced graphene oxide (CoS/rGO) nanocomposites were prepared through a simple one-pot hydrothermal method. The microwave absorption performance of CoS/rGO nanocomposites with different rGO proportions was systematically investigated. The CoS/rGO 1:1 nanocomposite achieves the reflection loss (RL) value of −37.3 dB at 8.6 GHz. The effective RL values (<−10 dB) of the CoS/rGO 1:1 nanocomposite are obtained in the frequency of 3.4–18 GHz while the thickness varies from 2.0 mm to 5.0 mm. Additionally, the simulated radar cross section results indicate that the CoS/rGO nanocomposites can efficiently suppress the strong EM scattering of metal plate in different incident degrees. These achievements demonstrate that the CoS/rGO nanocomposites can be used as high-performance microwave absorbing materials.

Multi-band terahertz chiral metasurface with giant optical activities and negative refractive index based on T-shaped resonators

A novel chiral metasurface (CMS) based on T-shaped resonators is proposed and investigated numerically. The CMS is composed of a periodic array of bi-layered conjugated fourfold T-shaped structure. The retrieved effective electromagnetic (EM) parameters indicate that the multi-band negative refractive index associated with strong optical activity and circular dichroism (CD) effect is realized in terahertz (THz) region. The physical mechanism is illustrated by analyzing the current density distributions. Due to its exotic chiral optical properties, the proposed CMS is useful for the development of THz devices.

Millimeter-wave half-waveplate based on field transformation

Over the last decades, manipulating polarization has received much attention due to its wide applications in science and technology. In this paper, a half-waveplate based on a field transformation (FT) method is proposed and investigated in order to convert polarization, which works at millimeter-wave band with a wide incident angle and broad working bandwidth.Inspired by the FT method, we confine our attention to a two-dimensional (2D) case of in-plane wave propagation on the x-y plane, with both material properties and fields unchanged in the z direction. The fields are denoted with a subscript “(0)” in the virtual space. Then a series of theoretical calculations is analyzed in detail. Under the guidance of theoretical analysis, it is shown that the main job for realizing this half-wavepalate is to obtain a material with specific permittivity and permeability. The proposed waveplate is composed of periodically arranged two dielectric layers each with sub-wavelength in height. By using the effective medium theory, the effective electromagnetic (EM) parameters of the waveplate can be tuned by manipulating the heights of the two dielectric layers. Among them one layer is a material with a permittivity of 10 and height of 0.68 mm, and another layer material has a permittivity of 1, and height of 5 mm. We alternately arrange the two materials along one direction periodically to obtain a waveplate for realizing the TE-to-TM and LCP-to-RCP conversion. The thickness of whole waveplate is 5.5 mm. A broadband EM half-waveplate is achieved in millimeter-wave region, which possesses a nearly 90% conversion efficiency across the frequency band from 24 GHz to 37 GHz. At the same time, we also find that when the incident angle gradually increases from 0° to 60°, the performances of polarization conversion efficiency and working bandwidth are still good. For the incident angle of 60°, a 3-dB bandwidth over 26-33 GHz is still achieved. The performance of the waveplate is verified through both full-wave simulation and experimental measurement, which are in good agreement with each other. Meanwhile, three-dimensional (3D) printing technology makes the sample fabricated more easily. Another advantage of our design is that the 3D printing technology can be used to carry out the experimental fabrication, which may pave a new way to manufacturing more microwave devices.

Modelling and Simulation of Rectangular Bundle of Single-Walled Carbon Nanotubes for Antenna Applications

This paper aims to present an effective electromagnetic (EM) modelling approach for rectangular bundle of single-walled carbon nanotubes (RB-SWCNTs), based on the electrical conductivity, relative complex permittivity and linear distribution impedance by applying General Ohm’s law for this bundle. The equivalent single conductor material (ESCM) model for personification the RB-SWCNTs is present in this paper. The main target of this modeling approach is to estimate and investigate the EM properties of RB-SWCNTs using common EM engineering tool solver CST (MWS). For this purpose, the RB-SWCNTs and ESCM dipole antennas will be designed and implemented using CST (MWS). The equivalent conductivity model, relative complex permittivity and other parameters of the RB-SWCNTs will be derived in this paper and considered as an equivalent material parameters for the ESCM. This modeling technique is expected to provide new avenues for designing different antenna structures.

Numerical study on a three-dimensional broadband isotropic left-handed metamaterial based on closed rings

In this paper, a three-dimensional (3D) broadband isotropic left-handed metamaterial (LHM) is proposed and investigated numerically. The 3D unit cell is composed of a dielectric cube with metallic closed rings (CRs) printed on all its six sides. Simulations of the electric field and surface current distributions, the effective electromagnetic (EM) parameter retrieval and a refraction phenomenon based on a wedge-shaped model were carried out to further verify the LH properties of the proposed 3D CRs structure model. The results show that the relative bandwidth is more than 6 GHz, and the LH band is polarization independent and almost unchanged for different incident angles. Moreover, the EM parameters of the unit cell with different geometrical parameters are also explored in order to obtain an optimized design for 3D LHM.

A Comparison of Active and Passive Metamaterials from Equivalent Lumped Elements Modes

With ever-increasing operating frequencies and complicated artificial structures, loss effects become more and more important in applications of metamaterials. Based on circuit theory and transmission line principle, the design equations for effective electromagnetic (EM) parameters (attenuation constant α, phase constant β, characteristic impedance Z0) of general active and passive metamaterial are compared and derived from the equivalent lumped circuit parameters (R, G, LL, CL, LR, CR). To verify the design equations, theα, βand Z0 indifferent cases, including balanced, unbalanced, lossless, passive and active, are shown by numerical simulations. The results show that using the active method can diminish the loss effects. Meantime, it also has influence on phase constant and real part of characteristic impedance.

Numerical studies on the collective vortex flow and RF responses of the intrinsic Josephson junction with periodic potentials

In-phase collective motion of Josephson vortices (JVs) over the junctions stack as well as the strong interaction between the vortices and the electromagnetic modes are needed to realize effective electromagnetic (EM) wave radiations from the intrinsic Josephson junction stacks. We have been studied the interaction from the RF responses of the intrinsic Josephson junctions in the flux-flow states. So far, the Shapiro-step-like responses were found in the flux-flow state with a cooperation of pancake vortices introduced by tilting the magnetic field direction out from the ab plane. The Shapiro-step-like responses suggest that the JVs collectively move keeping the rectangular lattice. We have proposed that the pancake vortices develop a periodic pinning potential that stabilizes the in-phase collective motion of JVs. We have carried out numerical simulations based on the coupled sine-Gordon equation considering the effect of the periodic pinning potential on the vortex dynamics. Current-voltage (I-V) properties of the inductively-coupled Josephson junction stack, which represent the intrinsic Josephson junction stack, were numerically obtained for both static and flux-flow states. It is shown that the periodic pinning potentials of appropriate strengths revealed Shapiro-step-like responses on the I-V properties of flux-flow states. It is also shown that the periodic pinning potentials stabilize the in-phase collective motion of the JVs over the junction stacks.

Effective electromagnetic shielding of plastic packaging in low-cost optical transceiver modules

A low-cost plastic package of the standard 1 /spl times/ 9 type with effective electromagnetic (EM) shielding ability is developed. Optical transceiver modules with transmission rates of 155 Mb/s and 1.25 Gb/s are tested to evaluate the EM shielding against emitted radiation from the plastic packaging. The results show that the packaged optical transceiver modules exhibit shielding effectiveness (SE) of over 20 dB. The EM shielding properties of plastic materials consisting of nylon66 and liquid crystal polymer (LCP) with carbon fiber reinforced are investigated. The effects of weight percentage of fibers, carbon fiber length, and material thickness on the SE of the plastic composites are studied both from the plane-wave and near-field sources approaches. The packaged plastic optical transceiver modules with their good SE are suitable for use in low-cost and low electromagnetic interference (EMI) Gigabit Ethernet lightwave transmission systems.

Clothing procedure in relativistic quantum field theory and its applications to description of electromagnetic interactions with nuclei (bound systems)

A growing interest in the method of unitary transformations (UT's) in the quantum theory of particles and nuclei has been seen during the last years. We express the total Hamiltonian H of interacting fields through new operators for particle creation and destruction and show that this can be understood as a UT of H. The respective particles may be called “cothed”. They are identified with the physical particles. The Hamiltonian in the new form turns out to be dependent on the renormalized particle masses and not the “bare” ones. Forms of the same kind are derived for all the Poincaré group generators. By using this new form of the Hamiltonian we suggest an approach to the bound state problem in relativistic quantum field theories (RQFT's). We also discuss applications of the developed formalism for constructing effective electromagnetic (EM) currents in the theory of photonuclear reactions.