Interference Of Electromagnetic Waves Research Articles

Numerical study of mid-infrared broadband perfect absorber based on dielectric/aluminium doped zinc oxide multilayer films

We propose a lithography-free wide-angle polarization-insensitive ultra-broadband absorber by using multilayer films consist of five pairs of aluminium doped zinc oxide (AZO) and a dielectric film which is supposed to be fabricated on glass substrate. The absorption spectrum of the proposed model is calculated by using transfer matrix method.The analytic results show that the absorptivity is larger than 95% with normal incidence light in the wavelength range from 7.5μm to 20μm and having high transmittance at the visible wavelength range from 0.4μm to 0.8μm range. Further, the effect of incident angle and polarization on the absorption spectrum are also investigated. The absorption spectrum of the proposed design is highly tunable on changing the damping constant of the AZO film. The electric field and magnetic distributions at different wavelengths show that the absorption is mainly originated due to the constructive interference of electromagnetic waves in the multilayer films. Such physical mechanism of broadening bandwidth based on increasing the carrier concentration of the highly visible transparent conducting films have pave a new direction for the design of tunable broadband absorber in different frequency band. Meanwhile, this broadband absorber is a good candidate for the potential applications in daytime radiation cooling system in the mid-infrared frequency band and also used as transparent conducting electrode in solar cell applications.

2-битные метаповерхности Патчаратнама-Берри с генерацией, интерференцией и гашением орбитального углового момента для широкополосного снижения ЭПР

The radar cross-section (RCS) reduction using non-absorbing digital Patcharatnam-Berry (PB) metasurfaces (MSs), consisting of 2-bit modules with generation, interference and cancellation of vortex electromagnetic waves with orbital angular momentum (OAM) is studied. Each module has a helical PB-phase profile and possesses vortex scattering. Module unit cells contain a shielded dielectric substrate and meta-particles in the form of triple-coupled split-ring resonators. The modules are distinguished by 2-bit coding of the initial tilt angle of the meta-particles 0º, 45º, 90º and 135º. The purpose of the work is to numerically analyze the generation of antiphase vortex beams (VBs) by OAM-modules and to assess the influence of interference and cancellation of antiphase vortices on the structure and order of OAM in the resulting field and the RCS reduction of three digital MSs in the form of 2´2 lattice of 2-bit OAM-modules of different sizes with different topological charges. The scattering characteristics are studied using HFSS for normally incident circularly polarized waves using of the finite element method. The simulation showed that the interference of phase vortices of four OAM-modules forms the main axial vortex and N additional interference side near and far vortices (N depends on the size of the MS). Interference vortex beams create phase singularities and zero the resulting far field in N side directions over the entire forward hemisphere. The intense OAM modes of the main vortex beams are of the fourth or eighth order. The OAM modes of adjacent interference VBs, as a rule, differ in sign. The proposed 2-bit MSs provide wider-angle phase cancellation of vortex fields (compared to 1-bit MSs) and, as a consequence, wider-angle diffuse scattering of the resulting field of the MS, which is important for RCS reduction.

Hypersonic boost-glide systems: Flight mechanics and plasma parameters evaluation through aero-thermo-chemical computational fluid dynamics

Currently, the conception, design, and development of hypersonic space-borne systems is a central topic of discussion among researchers and industrial stakeholders. In the design phase of a hypersonic manoeuvrable vehicle, it is essential to characterise the thermal heating and manage the problem of the communication blackout, in addition to other challenges concerning guidance, navigation and control, and propulsion. The interference of electromagnetic waves propagating in plasma affects the datalink and the radar detection of hypersonic targets. This work aims to provide valuable information about the aero-thermo-chemical behaviour of the fluid in the region around a hypersonic glider. Launch and re-entry phases of boost-glide systems have been modelled to perform trajectory predictions and assess range and flight paths under the effect of different manoeuvres, defining their possible performances. The resulting flight conditions are used to study the flow field surrounding a glider geometry similar to the Hypersonic Technology Vehicle-2. The thermodynamic and chemical fields around the body have been determined, and plasma parameters for novel electromagnetic interaction studies have been evaluated. Computational fluid dynamics simulations have been carried out to solve the averaged Navier-Stokes equations with the k−ω model for turbulent flows, coupled with the energy equation. Chemical non-equilibrium phenomena involving electronic energy relaxation as well as ionisation reactions have also been included. A gas mixture potentially composed of 11 species has been considered, namely oxygen and nitrogen derivatives. The electron number density is computed to evaluate the electron plasma and collision frequencies, essential parameters to characterise the electromagnetic interference caused by the plasma sheath. Among other results, high temperatures are reached at the nose region of the body in specific conditions of velocity and altitude, and non-negligible dissociation or ionisation of chemical species occurs. Plasma frequencies up to tens of GHz are reached in a region close to the body surface, while lower interference characterises the extended ionised wake.

Assessment of Radio-Frequency Radiation Exposure from Selected Mobile Base Stations in Yenagoa, Bayelsa State, Nigeria

The antennas from mobile base stations radiate non-ionizing radio frequency radiation into space. The human body can experience negative health effects from prolonged exposure to radiofrequency (RF) radiation. Because base station installations and telecommunication networks are growing, there is a growing need to address the health risks connected with exposure to telecommunication masts. Using the Electrosmog Meter Cornet Model, power density from many telecom masts owned by various network operators was measured in this investigation. At 10-meter intervals, the RF radiation in seven (7) settlements in Yenagoa town, located in the Yenagoa Local Government Area of Bayelsa State, was measured within radial distances of 100 meters. With a mean value of 4.0569mWm-2, the measured values vary from 0.650mWm-2 to 9.810mWm-2. Still, values evolved. Nevertheless, additional factors, such as adjacent electromagnetic sources' wave interference or reference base station interference, caused readings to fluctuate. It was discovered that the greatest power density level was 9.810 mWm-2, and it was measured 20 meters away from the base station at site MBS1. As per the International Commission on Non-ionizing Radiation Protection (ICNIRP) and other regulatory authorities, the standard limit of 4.5Wm-2 for the 900 MHz system is not exceeded by the radiation exposure level, as the findings show. This shows that the exposure levels in these areas are low enough to not seriously jeopardize the health of those living in the research area.

New Compounds for Electromagnetic Interference Shielding

The impact of electromagnetic wave interference on electronic devices and the danger that can arise from it has become a problem that is being discussed at the international level. This paper discusses research on important and effective materials and compounds to be used for EMI shielding. In this paper, three basalt samples (A12, A14, and B12) have been selected and analyzed for reflection and absorption for RF and microwave frequencies.

Design and Development of Metamaterial Absorber for IoT Applications

Microwave absorbers are efficient design structures that enhance electromagnetic shielding and reduce electromagnetic wave interference. It dissipates an incident electromagnetic wave by converting it into other forms of energy, thereby preventing the electromagnetic wave's reflection and/or transmission. A novel electromagnetic metamaterial dual-band microwave metamaterial absorber for IoT application is proposed in this manuscript. The proposed absorber has an excellent absorption rate, above 98% and 99% at 2.4 and 5.1 GHz, respectively. The structure, designed over FR-4 material, provides negative permittivity and permeability. The Nicolson Ross Weir (NRW) method investigates metamaterial properties. An array of (3 × 3) unit cell absorbers is designed, developed, and tested; simulated and measured results are in good agreement.

Additive manufacturing of broadband electromagnetic wave absorbing materials: Polymer-derived SiC/Si3N4 composites with triply periodic minimal surface meta-structure

High temperature ceramic-based electromagnetic wave (EMW) absorbing materials has been widely studied as multifunctional materials for the application in various high-speed vehicle. However, current high temperature EMW absorbing materials are limited by narrow absorption bandwidths due to their inferior impedance matching characteristics across a wide frequency range. This study proposes a novel polymer-derived SiC (PDCs-SiC)/Si3N4 triple periodic minimal surface (TPMS) meta-structure inspired by the gyroid bionic structure. The presented design strategy integrates the material and meta-structure properties, which was inspired by the interaction mechanism between these properties on the EMW absorption performance of the prepared composites. The TPMS meta-structure were fabricated through three-dimensional (3D) printing combined with precursor infiltration pyrolysis technology, followed by annealing treatment and Al(H2PO4)3 sol infiltration. The results demonstrated that the dielectric constants of the composites were reduced through annealing treatment and Al(H2PO4)3 sol infiltration process, thereby improving impedance matching and enhancing the EMW absorption performance. The effective absorption bandwidth (EAB) of the prepared PDCs-SiC/Si3N4 composites reached 3.52 GHz at a thickness of 3.3 mm. Furthermore, TPMS meta-structure with DSM unit demonstrated the excellent absorbing properties with a wide absorption bandwidth of 11.12 GHz, as evidenced by simulations and experiments. This can be attributed that the fully connected porous TPMS meta-structure further improved the impedance matching and enhanced the transmission path of electromagnetic waves, while the discontinuous unit in the top layer of DSM induced electromagnetic wave resonance and interference cancellation, thereby enhancing the EMW absorption performance of composites. This study presents an innovative development strategy for designing and preparing high-temperature electromagnetic wave absorbing materials with broad bandwidth.

Materials’ Properties of Lightweight Spiral Hybrid CNT/Epoxy Composites Enhanced Reflection Loss

Recently, various electronic devices have been developed to meet the requirements of higher frequency technology applications. This widely used application without realizing has created more electromagnetic interference pollution that is harmful to human health and other equipment. Therefore, more research interest focuses on fabricating the electromagnetic (EM) wave absorbing materials that can absorb the EM wave interference. In this regard, this research highlights the use of Iron Oxide and Cobalt Oxide as catalyst to synthesize hybrid CNT by using Thermal Vapor Deposition Tube (TVDT) method. The spiral hybrid CNT/epoxy composites were prepared at thickness of 1mm, 2mm and 3mm. The phase formation, microstructural, particle size and structural analysis of the hybrid CNT were analyzed by using X-ray diffractometer (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and RAMAN spectrometer respectively. The microwave characterization of the hybrid CNT/epoxy composite samples was analyzed by using Vector Network Analyzer (VNA) at GHz frequency range. The phase analysis confirmed the existence of Carbon and iron carbide in the sample. The microstructural of CNT formation are mostly in spiral and straight like structure. On the other hand, the structural analysis shows the sample are more towards defective structure with higher and broader D-band peak. This could enhance the EM wave absorption performance. The minimum reflection loss (RL) peak was ̴-23dB (t=3mm) obtained for all hybrid CNT composite samples. The differences of minimum reflection loss peak at different weight percentages are most likely shown by the shift of frequency range. Thus, this lightweight spiral hybrid CNT/epoxy composites results in better EM wave performance at different thin thickness used for different applications.

Finite Element Method study on VLF propagable modes coupling and interference in the anisotropic earth‐ionosphere waveguide

AbstractIn this paper, the coupled‐mode theory is incorporated into the improved frequency‐domain finite element method (FEM) to simulate very low frequency (VLF) propagable modes coupling and interference in the anisotropic Earth‐ionosphere waveguide. The matrix equation of the electric field is solved using parallel lower‐upper factorization technique to speed up the calculation. The method used to determine the propagation constants for different propagable modes is given. After the FEM is validated by comparing simulated results with the measured data, effects of variable geomagnetic information on the attenuation rate, relative phase velocity, mode coupling, and multiple‐mode interference of VLF electromagnetic wave in the anisotropic waveguide are investigated. This work provides an efficient way for improving the prediction accuracy of the VLF communication, positioning, navigation, and timing systems.

Carbon–Ni6Co3Fe1 alloy hybrid foil for electromagnetic wave interference shielding in X-band and extremely low frequencies

A magnetic alloy film/graphite composite is developed for shielding electromagnetic waves in the X-band and extremely low frequency regimes, using a scalable electrodeposition process. Enhanced thermal and mechanical properties are also achieved.

High-performance electromagnetic wave absorption of nitrogen carbon doped composite materials with vanadium based nanowire structure at 2–18 GHz

With the popularization of electronic devices, the interference of electromagnetic waves on people is more and more serious, and the development of excellent EMWA materials has become increasingly urgent. In this paper, carbon and nitrogen-loaded wheat ear shaped nanocomposites (V2O3/Zn)@C were prepared by in-situ polymerization and high-temperature calcination using ZnVO nanowires as the substrate and divinylbenzene and acrylonitrile as the loading materials. The polymeric carbon microspheres were infiltrated into the ZnVO nanowires after high-temperature carbonization, forming a wheat ear shape core-shell structure. The EMWA performance of (V2O3/Zn)@C composites was optimized by adjusting the ratio between the loaded feedstock and ZnVO nanowires. The EMWA results show that (V2O3/Zn)@C exhibits excellent EMWA performance at low thickness, with an RLmin of −56.5 dB and a EABmax of 5.25 GHz. This paper provides new insights into advanced electromagnetic wave absorbing materials through special structural designs.

Optimization of percolation limit of carbon black for electromagnetic interference shielding

Over the past few decades, the excessive use of electronic paraphernalia has increased the interference of electromagnetic waves, which not only disrupts the functionality of electronic appliances but also enhances environmental pollution. To avoid this destruction, an efficient material is required that can provide shielding from electromagnetic interference. Numerous researchers have made significant efforts to enhance EMI shielding using various types of nanofillers. However, a crucial aspect that has been lacking in these studies is an investigation into the optimal material quantity required for effective activation. Therefore, it becomes imperative to establish the percolation limit of the material, as this knowledge is vital in preventing unnecessary wastage and ensuring efficient utilization. Among polymer nanocomposites, Carbon black is the most demanding material for shielding purposes and is frequently used due to its abundance, superconductivity, and chemical stability. This work aims to identify the percolation limit of carbon black, which indicates the point at which the material becomes activated. To achieve this, different loading concentrations of the material have been tested. The thickness of all the samples was kept the same, at 3 mm. A vector network analyzer is used to analyze the EM shielding effectiveness of the composite material. Moreover, absorbance, reflectance, transmittance, skin depth, AC conductivity, and reflection loss have also been studied within the frequency range of 0.1 GHz to 13.6 GHz.

Design and numerical studies of microwave absorption structure based on hybrid weave of fibers with different dielectric properties

Continuous fibers reinforced ceramic matrix composites (CFCMCs) are considered as key thermal structural materials for realizing components electromagnetic wave (EMW) stealth of future aircraft. As the main EMW absorber, design and manufacture fiber woven fabrics with high performance of EMW absorption for CFCMCs attract increasing global attentions. In this study, a thin, broadband-absorption multi-fibers mixed fabric structure was designed by using multi-fibers with different dielectric properties as design units. This as-designed structure can achieve effective absorption of < −10 dB throughout the whole X and Ku bands, while being insensitive to EMW angles. The absorption mechanism of multi-fibers hybrid fabric structure was investigated by numerical simulation. Reflected wave interference, multiple scattering and absorption of incident electromagnetic wave in the fiber fabric, and strong electromagnetic resonance absorption between adjacent fibers cooperation are key factors to realize broadband EMW absorption.

Terahertz 3D point cloud imaging for complex targets.

The reconstruction of complex targets using terahertz technology is often hindered by diffraction and interference of electromagnetic waves, leading to the loss of fine target details. In this research article, we have introduced a terahertz synthetic aperture radar (SAR) imaging method that integrates an iterative closest point (ICP) algorithm, referred to as SAR-ICP, to achieve accurate reconstruction of intricate target structures. To accomplish this, multiple sets of point cloud data are acquired by varying the illumination viewpoint. The ICP algorithm is then employed to align and fuse these datasets, resulting in the generation of high-quality three-dimensional (3D) images. The experimental results validate the effectiveness of the proposed SAR-ICP method. The information entropy of the reconstructed 3D image using the SAR-ICP is approximately 0.05 times that of the conventional SAR method, indicating a superior image quality. In the future, we anticipate the widespread application of this method in areas such as security inspection, non-destructive testing, and other complex scenarios.

Seed-assisted in situ ZIF-8 growth on carbon nanofibers for enhanced microwave absorption

The design and preparation of excellent microwave absorbing materials is of great importance facing increasingly negative effects of electromagnetic (EM) wave radiation and interference. Combining metal-organic frameworks (MOFs) with one-dimensional (1D) carbon nanofibers is a valuable approach to improve microwave absorption performance. Herein, C/zinc oxide (ZnO) nanofiber composites were synthesized using the seed-assisted in situ electrospinning method, with the precursor being a zinc-based zeolitic imidazolate framework (ZIF-8). The unique porous structure and the heterointerfaces formed between C and ZnO facilitated the scattering and multiple reflections of microwaves. On account of the combination of interfacial polarization loss, dipole polarization loss and conduction loss, the C/ZnO nanofiber composites exhibited outstanding microwave absorption performance. The minimum reflection loss (RLmin) of −58 dB at 7.5 GHz as well as an effective absorption bandwidth (EAB) of 6.5 GHz was achieved. This work provides an innovative methodology for developing highly efficient microwave absorbing materials using a combination of carbon materials and MOF nanoparticles.

Electromagnetic response of grading honeycomb composites for broadband microwave absorption

The fundamental challenge for microwave-absorbing honeycomb composites with grading coating thickness is the unsatisfactory absorption bandwidth. In this work, an effective equivalent permittivity prediction model was established based on the homogenization method, also both the result of calculations and simulation exhibit good consistency which indicates the validity of the model. Furthermore, in-depth analysis was done on the impact of structural factors like honeycomb height and coating thickness on single layer microwave absorption. Finally, both the microwave absorption properties and the electromagnetic response of grading honeycomb microwave absorbing composites were investigated which show a bright future in reducing electromagnetic wave irradiation and interference. The present work could provide a powerful theoretical basis for designing advanced grading honeycomb microwave absorbing composites.

Heterogeneous interface engineering of high-density MOFs-derived Co nanoparticles anchored on N-doped RGO toward wide-frequency electromagnetic wave absorption

Facing increasing electromagnetic (EM) wave pollution and interference issues, developing synergy EM wave absorption materials with rich heterogeneous interfaces is s an effective way to solve the above problems. In this work, two-dimensional (2D) cobalt-based metal-organic frameworks (Co-MOFs) nanosheets arrays are firstly growth on the 2D graphene oxide (GO) sheets. After undergoing the pyrolytic treatment in the N2 atmosphere, high-density MOFs-derived 0D Co nanoparticles (NPs) uniformly anchored on the Nitrogen-doped reduced graphene oxide (N-RGO), constructing 0D/2D magnetic-dielectric Co@N-RGO composites. By tuning the size of magnetic Co NPs by controlling the content of Co-MOFs nanosheets, the EM parameters and impedance match of Co@N-RGO sheets can be regulated to tune the EM wave absorption ability. Benefited from the synergy loss and high-density heterogeneous interfaces, obtained Co@N-RGO sheets exhibit excellent EM wave absorption intensity and tuning absorption frequency. The effective absorption bandwidth of the Co@N-RGO sheets ups to 6.0 GHz at 1.9 mm thickness, covering the entire Ku band (12–18 GHz). It can be concluded that constructing magnetic-dielectric system and high-density heterogeneous interfaces provides a new guide to obtain wide-frequency EM wave absorption materials.

Cuttlefish‐Inspired Self‐Adaptive Liquid Metal Network Enabling Electromagnetic Interference Shielding and Thermal Management

AbstractWith the refinement and miniaturization of integrated electronic devices, the requirements for stable operating temperature and antielectromagnetic interference are increasingly high. However, most of the current materials necessitate to develop the intelligent self‐adaptive regulation in response to external field stimuli to gratify the stipulations of different operating environments. Herein, cuttlefish‐inspired smart liquid metal based‐liquid crystal elastomer (LGN‐LCE) dual‐functional material enabling self‐adaptive electromagnetic wave interference shielding and thermal management is presented. Liquid crystal elastomer matrix endows the LGN‐LCE dynamic self‐morphing properties under thermal activation, which leads to the liquid metal network with tunable thermal/electrical conduction. The thermal conductivity of LGN‐LCE can be increased to 10.3 W m−1 K−1 with the rise of surrounding temperature, while the electrical conductivity of LGN‐LCE can be enhanced to 4.3 × 105 S m−1. Such promoted electrical conductivity helps strengthen electromagnetic interference (EMI) shielding performance of LGN‐LCE, and the minimum EMI shielding effectiveness of LGN‐LCE can be improved from 48 to 62 dB within the X‐band. This work may not only pave a new way to rationally design a self‐adaptive EMI shielding and thermal management systems, but also show good prospects for practical applications, including thermal management materials, EMI materials, flexible electronic materials, smart materials, artificial intelligence systems, biomedical, and aerospace applications.

Poly(styrene sulfonic acid)-Grafted Carbon Black Synthesized by Surface-Initiated Atom Transfer Radical Polymerization.

Owing to their excellent electrical conductivity and robust mechanical properties, carbon-based nanocomposites are being used in a wide range of applications and devices, such as electromagnetic wave interference shielding, electronic devices, and fuel cells. While several approaches have been developed for synthesizing carbon nanotubes and carbon-black-based polymer nanocomposites, most studies have focused on the simple blending of the carbon material with a polymer matrix. However, this results in uncontrolled interactions between the carbon filler and the polymer chains, leading to the agglomeration of the carbon filler. Herein, we report a new strategy for synthesizing sulfonated polystyrene (PSS)-grafted carbon black nanoparticles (NPs) via surface-initiated atom-transfer radical polymerization. Treatments with O2 plasma and H2O2 result in the effective attachment of the appropriate initiator to the carbon black NPs, thus allowing for the controlled formation of the PSS brushes. The high polymeric processability and desirable mechanical properties of the PSS-grafted carbon black NPs enable them suitable for use in nonfluorinated-hydrocarbon-based polymer electrolyte membranes for fuel cells, which must exhibit high proton conductivity without interrupting the network of channels consisting of ionic clusters (i.e., sulfonic acid moieties).

A review: Advancement in metamaterial based RF and microwave absorbers

Microwave absorbers (MAs) are specially designed structures which dissipate an incident electromagnetic (EM) wave by converting it into thermal energy and thereby prevents reflection and/ or transmission. The MAs are extensively in demand due to their property to reduce the electromagnetic wave interference (EMI) and to enhance electromagnetic shielding (EMS). MAs are also used in potential military applications as a stealth technology to design stealth aircrafts, warships and army clothing etc. due to the reduction of radar cross section (RCS) of the defense equipment by the absorber coating. In this review work, study of metamaterial-based MAs, their characteristics viz. left-handed material property, permittivity and permeability have been discussed in detail. Metamaterials (MMs) or artificial materials that play a significant role in reducing the size and thickness of MAs depending upon the frequency of operation. In this work, theoretical background of MM-based absorbers detailing the effect of permittivity and permeability on absorber performance has also been discussed. Different applications of absorbers are elaborately covered in this paper. Furthermore, frequency selective surface (FSS) which is a two-dimensional array has the capability to reflect or transmit EM wave completely or partially depending upon the nature of FSS. Therefore, distinct categories of FSS-based absorbers are discussed according to the frequency of operation, bandwidth and material specification where the effect of different design parameters is also critically analyzed. The objective of this review paper is to provide an exhaustive study of the unique attributes of MAs having a diverse range of applications for frequencies ranging from microwave, terahertz upto optical frequency domain. This review paper is certainly a vital tool for researchers to accurately understand, explore and work on MA design and selection as per user defined specific frequency and applications.