Electromagnetic Field Distribution Research Articles

Improved field uniformity in EMC chamber for 6G communication

<span>This paper shows electromagnetic field uniformity in an electromagnetic compatibility (EMC) chamber that is used as a test facility for measuring electromagnetic interference and radiated immunity of 6G communication systems. While not defined yet, 6G radio frequency will work in the wavelength ranges above 95 GHz. With this reason, this paper designed a schroeder-type quadratic residue diffuser for 95 GHz to generate a uniform electromagnetic field in the EMC chamber and studied the field uniformity characteristics in it. To analyze the distribution of electromagnetic fields inside the EMC chamber, finite-difference time-domain (FDTD) numerical analysis method is used. The simulation results show that the EMC chamber with this diffuser satisfies the requirements of international standards and has improved the field uniformity in the chamber.</span>

Strain and interface engineering of MoS2 nanosheets decorated with Ag nanoparticles and its light-matter coupling in photoexcitation

The interfacial stress and electron transfer of metal decorates transition metal dichalcogenides (TMDs) are very important for the novel two-dimensional (2D) semiconductor optoelectronic device technology in the future. Herein, strain and interface engineering of molybdenum disulfide (MoS2) nanosheets decorated with Ag nanoparticles (Ag/MoS2) for controlled charge transfer and electron excitation-relaxation is presented. The effect of strong random scattering on the transport and electron localization phenomena of MoS2 is experimentally investigated. Exploring the charge fast transfer channel constructed by the plasma structure and the separated excited states of Ag, as well as explains the regulating mechanism of the optical absorption for TMDs in time domain. The finite-difference time-domain near-light field is used to simulate the effect of Ag content on the electromagnetic field distribution of MoS2, and then the modification of MoS2 is determined by controlling Ag content. Whilst, we can reveal the excellent light material interaction effect and ultrafast electron transfer mechanism of heterojunction surface contact sites. The E12g peak undergoes splitting, which originates from the lattice mismatch between Ag particles with plasma structure and MoS2, confirming the strong interfacial stress effect between them. On the basis of interfacial stress as well as the effective charge transfer, the Ag/MoS2 composites exhibit excellent excitation and emission behaviors. The local surface plasmon resonance effect of Ag nanoparticles is expected to adjust of nonlinear optical for TMDs. Specifically, we will regulate the ultrafast laser photon induced nonlinear absorption behavior by adjusting the Ag content and contact mode. The local strain generation on the Ag/TMDs boundary provides a new method for the design of new heterogeneous materials, and will be of great significance to investigate the contact physical behavior and application between metals decorates two-dimensional semiconductors.

Cut-wire metasurface embedded in magnetic mediums for ultra-wideband polarization-insensitive absorber with environmental adaptability

Metamaterials with artificial designability and perfect absorption provide a novel design method for the manipulation and attenuation of microwaves. However, owing to the limitations of meta-atomic resonance effect and the lossless medium, it is difficult to achieve effective microwave absorption in a broadband frequency range. Hence, an ultra-wideband metamaterial absorber (UWMA) composed of two magnetic media and a metasurface was designed, and the absorption bandwidth of 2.9 to 18 GHz for 90% absorptivity under normal incidence was achieved, covering almost the entire S, C, X, and Ku bands. Through detailed investigation of equivalent circuit, equivalent medium theory, electromagnetic field distribution and front-back interface interference, the internal physical working mechanism was clarified essentially. In addition, the multi-environment adaptabilities of the proposed absorber, including polarization sensitivity, large angle incidence, dual-station radar stealth, bearing capacity and corrosion resistance, were analyzed. The proposed metamaterial absorber presents an effective way to achieve ultra-wideband absorption and compatibility with environmental adaptability, and provides a new way of thinking for intelligent full-band stealth technology.

Ultra-broadband solar energy absorber based on Ti and TiN from visible to mid-infrared

In this work, a metamaterial absorber based on titanium (Ti) and titanium nitride (TiN) is proposed. Theoretical calculation by finite-difference time-domain (FDTD) method shows that the absorber could achieve a bandwidth of 3720 nm in the spectrum range of 280 nm − 4000 nm. The average absorptivity of the absorber can reach 96.9%. The physical mechanism of the absorber is analyzed from the impedance matching theory and electromagnetic field distribution. Furthermore, simulation results illustrate that the absorber is polarization-insensitive and allows a wide range of incident angles. The absorption spectrum is basically consistent with that of air mass 1.5 (AM1.5). And it can achieve high thermal conversion efficiencies over a wide range of temperatures. These results indicate that the absorber has a good development prospect in solar energy collection.

Ultrasensitive SERS detection of trace polycyclic aromatic hydrocarbons in seawater using 1-propanethiol modified Fe3O4/Ag@inositol hexaphosphate nanocomposite

Polycyclic aromatic hydrocarbons (PAHs) in seawater even at trace level could continuously cause serious threats via food chain. Herein, we fabricate 1-propanethiol (C3)-modified Ag@inositol hexaphosphate (IP6)-decorated Fe3O4 composite nanomaterials, namely Fe3O4/Ag@IP6-C3. The magnetic and hydrophobic of Fe3O4/Ag@IP6-C3 could greatly enrich PAHs molecules and has giant surface enhanced Raman scattering (SERS) effect due to magnetic inducing increase of SERS “hot spots”. The optimized SERS effect of Fe3O4/Ag@IP6-C3 triggered by the spatial distributions of electromagnetic field were validated by using finite difference time domain (FDTD) calculations, and the enhancement factor (EF) of 1.26 × 107 for 4-mercaptopyridine (4-MPy) as Raman probe. Interestingly, Fe3O4/Ag@IP6-C3-based SERS protocol shows specific response to pyrene owing to the great partitioning to pyrene in the presence of C3, which is also proofed by the simulation of binding energies between PAH molecules and Ag@IP6-C3 by using DFT method. The quantitative linear range for the detection of pyrene is from 1 μg/L to 10 mg/L (R2 =0.989) and the limit of detection (LOD) of 24 ng/L (24 ppt) is reached, which meets the limitation amount (1 ppb) of PAHs in water set by USEPA and WHO. Clearly, as-proposed SERS sensing strategy paves a path to realize seashore monitoring of marine environmental and early warning for PAHs pollution based on the pyrene as an indicator.

A Multiband Millimeter-Wave Rectangular Dielectric Resonator Antenna with Omnidirectional Radiation Using a Planar Feed.

In this study, a millimeter-wave (mmWave) dielectric resonator antenna (DRA) with an omnidirectional pattern is presented for the first time. A key feature of the proposed design is the utilization of a planar feed network to achieve omnidirectional radiation from a rectangular DRA, which has not been reported previously in the open literature. In addition, the proposed antenna offers multiband operation with different types of radiation patterns. The degenerate TE121/TE211 modes were excited at 28.5 GHz with an overall internal electromagnetic field distribution that was similar to that of the HEM21δ mode of a cylindrical DRA. The achieved omnidirectional bandwidth and gain were 1.9% and 4.3 dBi, respectively. Moreover, broadside radiation was achieved by exciting the TE111 fundamental mode at 17.5 GHz together with the resonance of the feeding ring-slot at 23 GHz. The triple-band operation offers a highly versatile antenna that can be utilized in on-body and off-body communications. Furthermore, the proposed design was validated through measurements, demonstrating good agreement with simulations.

Micro- and nano-scale optical focusing for carrier management in silicon solar cell

Well-designed nanostructures enable increased light trapping, reducing the loss of single-pass absorption and providing precise control over the microscale optical field, offering promising opportunities for developing next-generation high-efficiency solar cells. However, whether efficient carrier management in photovoltaic devices can be achieved by controlling electromagnetic field distribution using nanostructures remains elusive. In this study, we conducted simulations to investigate this issue and demonstrated the mechanism of micro- and nano-scale optical focusing in suppressing carrier recombination and enhancing the efficiency of silicon solar cells. By keeping the optical absorption of the silicon solar cell unchanged, under microscale light focusing conditions, we observed a relative 15.3% increase in the short circuit current compared to the Lambert law, resulting in a relative efficiency enhancement of 16.3%. Analysis of energy band, carrier density, recombination current, drift and diffusion current, and carrier mobility were conducted to reveal the recombination suppression mechanism. These findings comprehensively explain previously reported experimental results using wavelength-scale dielectric nanospheres to enhance the silicon solar cell efficiency. Furthermore, the implementation of nano-scale optical focusing offers the potential to significantly reduce the thickness of the device while maintaining high efficiency.

Origin of plasmonic Fano resonance in metal-hole/split-ring-resonator metamaterials disclosed by temporal coupled-mode theory.

In plasmonic Fano resonance, the interaction between a discrete plasmonic mode and a continuum of plasmonic mode gives rise to an asymmetric line shape in the scattering or absorption spectrum, enabling a wide range of applications such as sensing, switching, and slow light devices. Here, we establish a theoretical solution in the framework of temporal coupled-mode theory (TCMT) to study the three-dimensional (3D) and two-dimensional (2D) Fano resonances induced by strong coupling between metal hole (MH) and split ring resonator (SRR) array. We first separately analyze the transmission spectra of the MH array and SRR array under different polarized light excitation. We further investigate the electromagnetic field and charge density distribution corresponding to the resonant modes at the peak or valley wavelength of the transmission spectrum and figure out the electric/magnetic dipole feature of these resonance modes. We then establish a theoretical solution by TCMT for Fano resonances arising from the coupling of these modes. The calculated transmission spectrum is closely matching with the numerically simulated transmission spectrum for these Fano resonances in the MH-SRR array, which effectively elucidates that the asymmetry of the Fano resonances is caused by the coupling between bright and dark plasmonic modes involved in the two structures. Our results can help to understand the profound physics in such coupled plasmonic systems.

Geotechnical Deformation Distributed Measuring Technology Research Based on Parallel Spiral Sensing Line.

The precursors that appear when geological disasters occur are geotechnical deformations. This paper studies the TDR (Time Domain Reflection) measurement technology for the distributed measurement of geotechnical deformation using parallel spiral wire as a sensor, which is used for monitoring and early warning detection of geological disasters. Based on the mechanism of the electromagnetic field distribution parameters of the parallel spiral sensing wire, the relationship between the stretching amount of the parallel spiral wire and the change in its characteristic impedance is analyzed. When the parallel spiral wire is buried in the soil, the geotechnical deformation causes the parallel spiral wire to be stretched, and according to its characteristic impedance change, the stretching position and the stretching degree can be obtained, thus realizing the distributed measurement of geotechnical deformation. Based on this principle, the TDR measurement system is developed, and a local single-point stretching amount and stretching positioning experiment are designed for the parallel spiral sensing line to verify the effectiveness of the sensing technology and the usability of the measurement system.

Enhancing upconversion luminescence of rare earth ions by the activation of the antenna effect in plasmonic cuprous sulfide nanoparticles

To modulate the local electromagnetic field in the upconversion luminescence (UCL) of rare earth ions is one of the most effective ways to improve the luminescence intensity of upconversion nanocrystals (UCNs). Herein, the luminescence intensity of UCNs was increased by 5.8 times by activating the antenna effect of near-infrared plasma in cuprous sulfide nanoparticles. By simulating the local electromagnetic field distribution of the core-shell composites under 980 nm excitation light, the UCL enhancement mechanism of rare earth ions was studied. It showed that the antenna effect of plasmonic cuprous sulfide nanoparticles enhanced the absorption and utilization of excited light by UCNs, and the optical field in the vicinity of the core-shell composites was significantly optimized by inducing the localized surface plasmon resonance coupling between cuprous sulfide nanoparticles. Finally, our results provide a novel way to effectively regulate the local electromagnetic field in the UCL of rare earth ions.

Evaluation of Temporal and Spatial Distribution of Radio Frequency Electromagnetic Fields (RF-EMF) Exposure Levels in Sabzevar, Iran

Objectives: In recent years, investigating the possibility of health risks due to exposure to radio frequency electromagnetic field (RF-EMF) values has become an important research priorities. The main study goal was to evaluate the temporal and spatial exposure levels of power density (S) from BTS antennas in Sabzevar city. In addition, this study investigated the difference in power density between the suburbs and downtown, as well as between different microenvironments. Methods: The power density values were measured at three distances from the BTS antennas and at three different time intervals. S values were measured using a TES 593 electrosmog meter. The General linear model repeated measurement tests and Mann-Whitney U test were used to measure the objectives. The Inverse Distance Weighted method was used to draw the spatial distribution map. Results: Significant differences between the values of S Avg and S max Avg were detected based on distance from the BTS antennas, time measured, and type of location. For hospital, residential, residential-educational, residential-park, and residential-shopping, the average values of S Avg were 0.37, 1.15, 1.80, 1.89, and 1.94 W/m2 , respectively, and the average values of S max Avg were 0.43, 2.64, 2.54, 2.59, and 2.64 W/ m2 , respectively. There was a significant difference between S Avg and S max Avg values by microenvironment. Conclusions: Comparison of the all of the measured values of S in this study with the limits set by multiple organizations indicated that the residents of Sabzevar city are not exposed to levels considered to pose a risk.

An Ultrathin Polarization Free Asterick-Shaped Metamaterial Absorber with Quad-Band Characteristics

In this paper, a quad-band absorber is proposed and developed, which is exhibiting ultrathin and polarization insensitive behaviour. It has been designed to be operated in S, C, and Ku bands with absorptions peaks at more than 95%. The proposed absorber is implemented on a FR4 glass epoxy laminate with an equivalent electrical thickness of 0.0108 λ0, where λ0 is the wavelength corresponding to the lowest frequency of operation. This confirms the ultrathin nature of the structure. The absorption performance of the proposed structure has been characterized under normal and oblique incidences followed by their experimental verification. Presented results demonstrate highly polarization-independent behavior of the proposed absorber due to its symmetric geometry. Also, the electromagnetic field distributions have been studied to acquire better insight of the absorption mechanism corresponding to distinct elements present in the structure. It is characterized in terms of its behavior as metamaterial, which ensures the miniaturization. The proposed absorber is suitable to be used in applications like radar cross section reduction, stealth technology, radio frequency identification, and electromagnetic compatibility.

Estimation of Electromagnetic Radiation Distribution in the Human Heart Rate at Different Frequencies‏‏

The health implications of electromagnetic radiation have been extensively debated due to the sharp increase in the usage of cell phones, Wi-Fi transmitters and other microwave equipment. Electromagnetic radiation affects the autonomic nervous system, heart rate, blood pressure and other cardiovascular functions. This study aims to present a Numerical Simulation of Electromagnetic Radiation (EMR) on the human heart tissue and to explore the effect of different frequencies in the spectral range (900, 1,800 and 2,400 MHz) on Specific Absorption Rate (SAR), power density, the Distribution of Electromagnetic Fields by Matlab program, and Finite-Difference Time-Domain (FDTD) method in One Dimension (1D). A 1-dimensional finite difference method was used to solve Maxwell’s equations in heart tissue. The heart model was subjected to electromagnetic radiation that has dielectric properties according to frequency. Frequency was chosen and the operation of the software program as Matlab and the dielectric attribute has been calculated. Concurring with the Frequency in a private program, are the conductivity, relative permittivity, wavelength and infiltration profundity. The amplitudes of the reflected and transmitted sinusoid waves, relative to the occurrence wave, were portrayed by the reflection coefficient and the transmission coefficient, which relate to the amplitudes of the electric field wave. The electric field, magnetic field and power density were simulated along the line X = Y = 0. The study showed that the impact of electromagnetic radiation depends on the frequency of the wave which hit the heart. It was found that the heart tissue reacts more at 900 MHz compared to 1,800 and 2,400 MHz, and the tissue absorption is higher at the lower frequency. There was a relation between the magnetic field in the y-dimension and the time step the in x-dimension. HIGHLIGHTS The effect of electromagnetic has been theoretically studied where the electromagnetic fields produced from electromagnetic radiation at 900 MHz,1800 MHz, and 2400 MHz on layered biological tissues (heart model) by the finite difference time domain (FDTD) method A one-dimensional finite difference method was used to solve Maxwell's equations in heart tissue The amplitudes of the reflected and transmitted sinusoid waves, relative to the occurrence wave, were portrayed by the reflection coefficient and the transmission coefficient, which relate to the amplitudes of the electric field wave The impact of electromagnetic radiation depends on the frequency of the wave which hit the heart. There was a relation between the magnetic field in the y-dimension and the time step the in x-dimension GRAPHICAL ABSTRACT

GRAPHENE – GOLD GRATING-BASED STRUCTURE TO ACHIEVE ENHANCED ELECTROMAGNETIC FIELD DISTRIBUTION

In this work, the field distribution in structures such as a gold grating, a graphene layer, and a silicon substrate was studied. The conditions for maximum electromagnetic field distribution (absorption) by this structure to use in photonics and electronics devices were established. The magnitude of the electromagnetic field of a gold diffraction grating with a graphene layer increases with decreasing slit width. At the same time, an increase in the period leads to small changes in the electromagnetic field distribution. The maximum value of the distribution of the electromagnetic field is increased significantly, almost twice reducing the thickness of the graphene layer.

Effect of defects and doping on the transmission spectrum enhancement of photonic crystal based on 2D-MoS2

In this paper, we present the structural and photoluminescence (PL) spectra of 2D-MoS2 and we report a theoretical investigation of the influence of Ag- and Au-doping on the transmission in 2D-MoS2 photonic crystal structure (PCS). A finite-difference time-domain (FDTD) technique and plane wave expansion method (PWE) have been introduced and adapted for periodic and aperiodic structures to extract the PC-bandgap and study the behavior of the transmission spectrum. The impact of the size of defects, the Ag- and Au-doping on the 2D-PC band structure and transmission spectrum has been visualized under the inclusion of the distribution of electromagnetic fields and the associated field maps. It has been shown that the Au-doping changes significantly the 2D-MoS2 PCS and as a result the transmission spectrum increases considerably. We can predict that 2D-MoS2 PC doped with Au is more convenient than doped with Ag in most applications involving optical transmission and waveguides for optoelectronics devices.

Directional microwave heating based on time reversal quantified by information theory

Microwave heating has found extensive applications across diverse industries. However, achieving directional heating remains a significant challenge due to the complexities involved in controlling the electromagnetic field distribution. To address this issue, a novel directional heating method based on time reversal is proposed in this paper. A small signal source is placed at the heated medium to radiate electromagnetic waves. The information received by each receiving unit undergoes specialized processing before being transmitted back to the cavity. Consequently, the time reversal electromagnetic field of each receiving unit gathers at the heating material to achieve directional heating. Moreover, methods are being proposed to calculate the amount of information during time reversal using information theory. These approaches also aim to quantify the disparity in electromagnetic field distribution before and after the time reversal process. A comprehensive multi-physics model of microwave heating is established to simulate the directional heating process based on time reversal. An experimental system is also constructed to validate the proposed model, where the heating results are measured by an infrared thermal imager and a thermocouple. Finally, the effects of frequency, power and phase on the performance of directional microwave heating are analyzed.

THE PHYSICO-TOPOLOGICAL SIMULATION OF A TRANSMISSION X-RAY TUBE WITH INDUCTION HEATING OF THE CATHODE

Physico-topological simulation of a transmission X-ray tube (TRT) with inductionally heated thermionic cathode is presented, taking into account physical properties of functional elements and their design. Modeling is based on physical fundamentals for vacuum electronics and electrodynamics using ComSol. The distributions of electromagnetic fields, currents, temperature, and trajectories of thermoelectrons were calculated. The analysis of electron trajectories made it possible to optimize TRT topology and design.

Nonlocal resonances in pedestal high-index-contrast metasurfaces based on a silicon-on-insulator platform

Subwavelength control of the electromagnetic field distribution represents one of the current challenges in photonics research. In this field, diffractive metasurfaces with spatially extended (i.e., nonlocal) resonant modes have recently gained great interest for their versatility in molding the electromagnetic field beyond the approximation of independent resonators. In this framework, we design a high-contrast nonlocal metasurface featuring modes situated in the third operating spectral window of optical communications. The optical properties of the fabricated metasurface are investigated by linear spectroscopy and numerical simulations. Our analysis allows to discern the magnetic and electric nature of the bounded modes by means of polarization-resolved reflectance measurements. Our results represent a step toward integrated nano-photonics in the telecom regime and open promising opportunities for the development of compact nonlinear optical devices.

Using Modeling to Select the Type of Microwave Field Emitter for Dense-Layer Grain Dryers

The microwave field is used for drying and disinfecting grains during the pre-sowing seed treatment. The use of a microwave field in these installations leads to an increase in their productivity and a decrease in the energy consumed by them. In grain dryers, where the grain moves in a dense layer without being loosened, one of the challenges in using microwave fields is ensuring sufficient uniformity of the field distribution. In this article, waveguide design options that introduce microwave radiation into the grain layer are discussed. The objective of this study was to use application software to find the optimum type of transmitter from the three options presented. A mathematical simulation of the electromagnetic field distribution was performed with the use of CST Microwave Studio software 2019 in order to evaluate and compare horn-type, rectangular, and semicircular waveguides. The data on the standing wave ratio and radiation efficiency of these types of waveguides have been reported. The specific features of the microwave electromagnetic field distribution and radiation power in the output of these waveguides have been described. The results of mathematical simulations revealed that semicircular waveguides with slot-type radiators are preferable for processing dense grain layers.

Near-infrared electromagnetic excitations in Si1-xGex alloy semiconductor based permittivity-asymmetric metasurface

As one of the promising and extensively studied alloy semiconductors, the optoelectronic properties of Si1-xGex alloys have been well studied, but fundamental electromagnetic (EM) properties are rarely explored and discussed. In this work, the EM excitations of magnetic multipoles and toroidal dipoles in Si1-xGex based permittivity-asymmetric metasurface at near-infrared spectral region are investigated. Multiple Fano resonances (FRs) occur in the structure, and the formation mechanisms of resonance excitations are analyzed in detail combining theory with EM field distributions. In addition, the proposed metasurface is also investigated for its potential as a refractive index sensor due to its finer spectral property. It is hoped that our work will help to understand the EM properties of Si1-xGex alloys and find its potential applications in optics, such as refractive index sensing. The results obtained here provide fundamental insights into the exploration of EM excitations of Si1-xGex alloys.