Characteristics Of Electromagnetic Waves Research Articles

Analysis of electromagnetic wave characteristics of heterogeneous plasma sheath based on the ZT-DGTD

Analysis of electromagnetic wave characteristics of heterogeneous plasma sheath based on the ZT-DGTD

Recent Advances in Terahertz Manipulations Using C‐Shape‐Split‐Ring‐Resonator Metasurfaces (Review)

AbstractMetasurfaces have garnered significant interest owing to their inherent advantages over traditional optical components in manipulating electromagnetic waves unconventionally. Among the fundamental building blocks of metasurfaces, C‐shaped‐split‐ring resonators (CSRRs) have emerged as a highly promising option, enabling strong resonances and precise control over various characteristics of electromagnetic waves, such as phase, amplitude, and polarization. This review aims to showcase recent advancements in CSRR metasurfaces for manipulating THz waves, particularly focusing on both passive and active methods employed for controlling THz waves using single‐layer and multi‐layer CSRR metasurfaces. Moreover, this review will provide valuable insights into potential research directions in this rapidly evolving field.

Influence factors and mechanism of backscattering characteristics of electromagnetic waves in a single layer plasma tube array

A single-row plasma tube array (PTA) experimental system is established to improve the backscattering attenuation of a metal plate covered by a plasma tube array. The backscattering test system is utilized in a microwave anechoic chamber to examine the effects of gas composition, pressure, tube diameter, and discharge power on the backscattering attenuation of a metal plate using a plasma tube array. The electron density is obtained via microwave diagnosis. The backscattering attenuation mechanism in different frequency bands is revealed via numerical simulation. The results show that the reasonable selection of PTA parameters achieves strong attenuation in different frequency bands. The strong attenuation frequency bands of Ar–Hg PTA are in low frequency (1.5–3.5 GHz) and high frequency (13–17 GHz), while that of Ne–Hg discharge is in medium frequency (6.4–11.7 GHz). When the pressure is 0.5 and 1 Torr, the PTA shows a low, medium, and high multi-band distribution for the backscattering strong attenuation region. The backscattering strong attenuation region shows a low and high dual-band distribution, while the pressure is 2–4 Torr. As the tube diameter increases, the strong attenuation region maintains the dual-band, but it changes from low and high frequency bands to medium frequency (6-12 GHz), where the backscattering attenuation mechanism is collisional absorption when the frequency of plasma electron oscillation is close to that of electro-magnetic waves. The backscattering attenuation mechanism in the low frequency band involves the periodic structure of PTA generating local surface plasmon to absorb electromagnetic waves.

Application and testing technology of new road materials in highways

Abstract In the face of annual highway construction and highway maintenance projects, traditional road materials and road testing technology are difficult to meet the current highway construction needs. Based on this research background, the article first discusses the three-dimensional ground-penetrating radar nondestructive testing technology, analyzes the detection principle from the fluctuation equation of electromagnetic wave, the propagation characteristics of electromagnetic wave, and the propagation speed in the medium, and specifically analyzes its detection performance and application in the detection of the thickness of the structural layer. Finally, some sections of the Shanzhan Expressway are chosen as test objects and test experiments are designed and implemented. The test results show that the strength of the road material with water water-reducing agent increases compared to the material without water water-reducing agent. By using red mud instead of cement, road materials can have a relatively high strength. Therefore, using red mud as a substitute for conventional materials is entirely feasible and can save costs. The cracking rate of the highway was reduced by using the “leaching recycled” material, and the small cracks of less than 2mm were basically sealed, while the cracks of more than 2mm were alleviated. There is no water seepage on the pavement at 28 points of the 7 sections tested, so the “leaching regeneration” material has a better waterproof effect on the highway pavement.

Special Issue on the Progress and Application of Electromagnetic Materials

Electromagnetic materials refer to materials that can manipulate electromagnetic waves, which can control the amplitude, phase, polarization, spectrum, and other characteristics of electromagnetic waves [...]

Analysis of electromagnetic wave applications and development

With the continuous advancement of science and technology, the variety of technological products around our lives has also increased, and many of them use the characteristics of electromagnetic waves. In order to make people better understand the relevant characteristics of electromagnetic waves, this article will systematically introduce the basic theory, classification, application and related safety issues of electromagnetic waves. Electromagnetic waves not only have a wide range of applications in daily life, such as communications, remote sensing and other fields, but also play an important role in military and medical fields. Although electromagnetic waves bring many conveniences, there are also certain safety risks. Therefore,understanding the nature and application of electromagnetic waves to better protect our health and promote scientific and technological progress is important. In addition, for the limitations and shortcomings of electromagnetic wave applications, It is also crucial to explore potential development directions, in order to achieve comprehensive and efficient electromagnetic wave applications in the future.

Observation of photonic Peierls transition for manipulating microwave in metallic diaphragm-array periodic structures

Peierls transition that modifies electronic band structure has attracted intensive attention in solid state physics. In the present work, we report that a photonic analog of Peierls transition has been observed in a 1-D triangular metal diaphragm array, where the photonic bandgap structures have been designed at will by adjusting periodically metal diaphragm positions. It is shown by the numerical analysis that the transmission and radiation effect of the present periodic metal structure designed through the Peierls transition rule exhibits the behavior significantly different from an original periodic structure with each unit cell containing a metal diaphragm. The near- and far-field measurement results are in good agreement with our theoretical simulation. The present effect of photonic Peierls transition can serve as a working mechanism for designing new types of guided wave devices. It can be seen that the photonic Peierls transition would be one of the simplest ways for modifying the transport characteristics of electromagnetic waves in periodic structures.

IQ-Impaired Wireless-Powered Modify-and-Forward Relaying for IoT Networks: An In-Depth Physical-Layer Security Analysis

With the large-scale commercialization of 5G networks, the era of Internet-of-Things (IoT), which is oriented towards the internet-of-everything (IoE), is coming. Under the circumstance, reliable and secure communication are the great challenges for future wireless network because of the broadcasting characteristics of electromagnetic wave. Physical layer security (PLS) is an effective way to ensure secure communication by exploiting random nature of fading channels. Motivated by this, we investigate PLS of the wireless-powered cooperative multi-relaying for IoT networks in the presence of eavesdropper with the estimation errors of channel (EEC) and imbalance between in-phase and quadrature-phase (IIQ). Specifically, the relays can be charged by the source with the aid of energy harvesters, and a novel more secure modify-and-forward (MF) relay protocol is proposed. For further improving energy efficiency and reducing extra interference, the K-th superior relay selection scheme is proposed since some best ones are not available due to some scheduling or failure. Based on the system under study, we derive the analytical expressions for the outage probability (OP), intercept probability (IP) and secrecy outage probability (SOP) to evaluate the reliable and secure performance of this consideration system. Particularly, we then analyze the asymptotic behaviors of the OP, IP and SOP, respectively. Through computer simulation, we show that: i) With EEC, the error floors of the OP and SOP are of presence; ii) Multiple relays lead to better OP and SOP performance; and iii) IIQ improves the security and is detrimental to the system reliability.

Analysis of electromagnetic waves reflected by re-entry plasma sheath based on CSO-FDTD

A transmission model of terahertz waves in the plasma sheath is established based on a cascaded finite time domain difference method and analyzed the transmission characteristics of electromagnetic waves under the action of an external magnetic field and collision frequency. The flow field around the hypersonic aircraft is simulated and the characteristics of the flow field as the altitude changes of the aircraft are analyzed based on the flow field distribution of the RAM-C (Rapid Attenuation Measurement) vehicle. The results show the transmission characteristics of terahertz waves in plasma that will be affected by flight height, plasma parameters, external magnetic field, and collision frequency. In addition, under the action of an external magnetic field and the different collision frequency, the transmission characteristics of the left-handed terahertz wave will be improved. The application of the magnetic field will introduce an absorption peak in the right-handed terahertz wave, and it will move to the high frequency direction with the increase of the magnetic induction intensity.

Tunable chiral photonic cavity based on multiferroic layers.

Realization of externally tunable chiral photonic sources and resonators is essential for studying and functionalizing chiral matter. Here, oxide-based stacks of helical multiferroic layers are shown to provide a suitable, electrically-controllable medium to efficiently trap and filter purely chiral photonic fields. Using analytical and rigorous coupled wave numerical methods we simulate the dispersion and scattering characteristics of electromagnetic waves in multiferroic heterostructures. The results evidence that due to scattering from the spin helix texture, only the modes with a particular transverse wavenumber form standing chiral waves in the cavity, whereas all other modes leak out from the resonator. An external static electric field enables a nonvolatile and energy-efficient control of the vector spin chirality associated with the oxide multilayers, which tunes the photonic chirality density in the resonator.

Ultra‐broadband electromagnetic wave absorption of ceramic composite coating by atmospheric plasma spraying

AbstractDy doped ceramic material of Ba4Fe2.6Dy1.4Nb8O30 with the tetragonal black bronze structure was synthesized by solid‐state reaction at 1300°C. The composite powders of Ba4Fe2.6Dy1.4Nb8O30/FeSiAl with good flowing were prepared by spray drying using the powders slurry. The obtained composite powders were then plasma sprayed to fabricate coating. The microstructure and absorption characteristics of electromagnetic wave (EMW) of the coating materials are investigated. Results show that the composite powders significantly remain the phase stability during atmospheric plasma spraying and adsorbing heredity of EMW for the coating. The coating powders have excellent EMW absorption with the minimum reflection loss of −48.20 dB at the thickness of 3.5 mm. Also, the coating powders display the maximum effective absorption bandwidth of 6.24 GHz at the thickness of 1.5 mm, which covers the X‐band. Moreover, the coating was found to have a certain EMW absorption performance at high temperature of 700°C. The Ba4Fe2.6Dy1.4Nb8O30 ceramic material with low thermal conductivity ensured the electromagnetic absorption capacity of the coating at high temperature. The Ba4Fe2.6Dy1.4Nb8O30/FeSiAl ceramic composite materials could have the potential applications as the high temperature EMW absorber.

Specific Features of the Angular Distribution of Electromagnetic Radiation of the Kerr Black Hole

By analyzing algebraically special solutions of the Maxwell equations in the Kerr space-time, we obtain the exact expressions for the polarization characteristics of electromagnetic waves emitted from the vicinity of a black hole. We revealed the asymmetry of dependence of the ellipticity angle on the polar angle for the fundamental mode and the first harmonics of polarized radiation. This creates a basis for the new method of evaluation of the intrinsic angular momentum of the Kerr black hole. It is shown that the existence of singular points of the solution in a local orthonormal frame is a consequence of the Poincaré–Brouwer theorem.

Effects of High-collision Plasma on Radiation Protection of Human Brain

Objective: The purpose of this paper is to find a reasonable composite structure of electromagnetic protection device, especially the distribution characteristics of plasma parameters and operation conditions. Methods: Due to its high collision frequency, the high-pressure discharge plasma can be usedas a filling medium to take the electromagnetic protection effect. The strategies and algorithmsare presented to solve the propagation characteristics of electromagnetic wave (EMW) in plasma with complex dielectric constant. When the real and imaginary part of permittivity are of the same order of magnitude, the imaginary part value will impact on the feature of plasma dielectric constant, also affect the behavior of propagation of EMW. The propagation process of EMW in virtual human brain (VHB) model is investigated by finite difference time domain method. By optimizing the layout of plasma layer and air layer, an effective phase regulator is constructed, and the reflected wave amplitude is greatly reduced. Results: The simulation results show that plasma makes the amplitude of the electromagnetic fields in VHB decrease to different degrees. their maximum average decrease is about 25% and the corresponding reduction of SAR value is more than 40% in the frequency range of 1.8-3.6GHz. Conclusion: The existence of plasma can make the scalp and muscle possess the excellent performance in resisting the incident of EMW, so that the amplitude of the electromagnetic field inside the brain body is small, so as to effectively protect the brain tissue. These research results have good reference value and engineering applicability for the structure design of protection equipment with high frequency of EMW.

Study on The Scattering Characteristics of Electromagnetic Wave with Dielectric Band

When electromagnetic signal penetrates medium, its signal intensity will decrease and even change the polarity of electromagnetic wave due to the scattering of electromagnetic wave. Electromagnetic wave signal propagation in rainy days, fog days, dust and another medium electromagnetic signal attenuation phenomenon. Since raindrops, haze particles, dust particles and other media have different degrees of electric quantity, in order to measure the effect of charge itself on electromagnetic wave attenuation, this paper involves the attenuation experiment of electromagnetic wave with dielectric plates. PP board, PVC board and PMMA board are selected to conduct experimental research on the influence of electromagnetic signal attenuation.

Theoretical Study on the Collective Scattering Properties of Charged Particles to Electromagnetic Waves

The rapid development of electromagnetic technology has been widely used in many fields. For example, the transmission of electromagnetic waves in extreme environments (such as sandstorms and haze) and the monitoring of particle composition in the atmosphere by using electromagnetic wave technology. The properties of particles, such as particle electrification, will affect electromagnetic wave scattering and directly affect the signal transmission quality and monitoring results. Based on the scattering characteristics of electromagnetic waves of charged particles, the effects of different particle composition, different electric quantity, different humidity and different particle numbers on electromagnetic wave propagation are studied in this paper. The multiple scattering of electromagnetic waves by the random distribution of multiple particles is studied, and the Maxwell equation is converted into the Foldy–Lax multiple scattering equation, and the numerical solution is carried out. The influence of charged particle clusters on the electromagnetic scattering is analyzed. The simulation and experiment show that the charge of particles has a great influence on the electromagnetic scattering near some frequencies.

Design of the Polarization-Independent Wavelength Multiplexing Holographic Metasurface

Metasurface regulates the polarization, phase, amplitude, frequency, and other characteristics of electromagnetic waves through the subwavelength microstructure. By using its polarization characteristics, it can realize the functions of optical rotation and vector beam generation. It is the most widely used method of regulation. However, parallel optical manipulation, imaging, and communication usually require polarization-insensitive focused (or vortex) arrays of beams, so polarization-independent wavelength multiplexing optical systems need to be considered. In this paper, the genetic algorithm combined with the computer-generated hologram (CGH) is used to control the transmission phase of the structure itself, and on the basis of wavelength multiplexing, the corresponding array of focused or vortex beams without the polarization selection property is realized. The simulation software results show that the method has a huge application prospect in optical communication and optical manipulation.

Study on weak signal enhancement method in wireless communication under electromagnetic interference environment

In order to overcome the problems of high bit error rate and high signal enhancement time in weak signal enhancement methods, this paper proposes a weak signal enhancement method in wireless communication under electromagnetic interference environment. Firstly, the transmission characteristics of electromagnetic wave are analysed and the attenuation results of electromagnetic wave signal transmission are determined. Then, the bandwidth of weak signal is determined by band-pass sampling theorem, and the key characteristics of weak signal are determined by time-domain characteristic analysis. Finally, the amplitude modulation coefficient is used to adjust the frequency offset and initial phase through a low-pass filter to enhance the weak signal in wireless communication. The experimental results show that the lowest bit error rate of this method is about 1%, the weak signal enhancement time is no more than 2.6 s, and the weak signal enhancement effect is good.

Effects of Uniaxial Bianisotropic Media on Full-Polarimetric GPR Signatures

The polarimetric response of full-polarimetric ground penetrating radar (FP-GPR) from anisotropic media is a pressing issue to be investigated. It can improve the detection accuracy of the targets in the anisotropic media and can also provide effective ways to detect anisotropic targets. In this paper, we focus on the FP-GPR signals from uniaxial bi-anisotropic media, i.e. the complete case that both the permittivity and the conductivity of the background media are anisotropic. Based on the propagation characteristics of electromagnetic waves in the anisotropic media and the transmission coefficients on the surface of the media, we construct a mathematical relation between the measured scattering matrix affected by anisotropies and the real scattering matrix, derive a coefficient to characterize the polarization rotation(PR) effects, and proposed a diagonal matrix for target decomposition analyses. The computation results indicate that ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>z</i></sub> /ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> , σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>z</i></sub> /σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> , and antenna interval have complex effects on the PR coefficient and the H-Alpha decomposition results of three types of typical targets. Multiple 3D FP-GPR simulations on a series of uniaxial bi-anisotropic models verified the results.

Enhanced plasmonic waveguide sensing performance with a semicircular-ring resonator

In this study, a plasmonic refractive index sensor composed of a semicircular ring resonator embedded with silver nanorods (AgNDs) and a metal-insulator-metal (MIM) bus waveguide was developed. The designed system has the advantage of a shorter optical path than a regular circular resonator. Consequently, its size is half that of a typical one. In addition, the basement of the resonator can offer a more extended coupling interface facing the bus waveguide, increasing the gap plasmon resonance between the incident light and AgNDs. The finite element method (FEM) comprehensively simulated the transmittance and electromagnetic wave characteristics. The size of the AgNDs was found to be the main factor influencing the gap plasmon mode in the resonator and contributed to the increased sensitivity of the structure. Compared with its standard counterpart, the designed structure can increase the sensitivity of the device by 223.07%. The calculated maximum sensitivity was 2900 nm/RIU. This work paves the way for designing sensitive plasmonic sensors and could be rival candidates for sensing applications.

Efficacious GPR Implementations of Z-Transform-Based Hybrid LOD-FDTD with Subgridding Scheme: Theoretical Formalism and Numerical Study

Ground penetrating radar (GPR) forward modeling is one of the core geophysical research topics and also the primary task of simulating ground penetrating radar system. It is a process of simulating the propagation laws and characteristics of electromagnetic waves in simulated space when the distribution of internal parameters in the exploration region is known. And the finite-difference-time-domain (FDTD) method has the characteristics of simulating the space-time transient evolution of electromagnetic wave, whose numerical method is simple and easy to program, so it has become one of the most extensively utilized methods in GPR forward modeling. It is generally known that the conventional FDTD approach requires finer uniform Yee cell all the time to produce satisfactory accuracies from numerical simulations of the GPR. However, the smaller temporal incremental has to be adopted due to the lower spatial incremental, which would dramatically weaken the advantage of the FDTD method. To solve this issue, the subgridding-technique-based hybrid local-one-dimensional FDTD (LOD-FDTD) is applied in this work to modeling the classical GPR scenarios. In this method, the unconditional-stable LOD-FDTD is employed in the fine-grid domain, while the traditional FDTD is used in the coarse-grid domain, which could avoid the oversampling problem in the local domain if the uniform fine-grid scheme is adopted. Meanwhile due to the unconditional stability of the LOD-FDTD, the larger time step, derived from the coarse grid which satisfies the Courant-Friedrichs-Lewy (CFL) stability condition, could be utilized in the whole domain so that the long-time interpolation process could be circumvented. Additionally, the proposed approach could be arbitrarily adjusted by means of different ratio of both coarse- and fine-grid, and hence it holds much higher generality. As compared with the auxiliary differential equation (ADE) technique, the Z-transform method is integrated into FDTD methods for modeling multi-pole Debye-based dispersive media in this method, resulting in more direct numerical implementations and fewer computing steps. Finally, three different classical GPR problems are carried out to validate accuracies and efficiencies of the proposed method.