Electromagnetic Wave Propagation Research Articles

Absorption‐Dominant Electromagnetic Interference (EMI) Shielding across Multiple mmWave Bands Using Conductive Patterned Magnetic Composite and Double‐Walled Carbon Nanotube Film

AbstractThe revolution of millimeter‐wave (mmWave) technologies is prompting a need for absorption‐dominant EMI shielding materials. While conventional shielding materials struggle in the mmWave spectrum due to their reflective nature, this study introduces a novel EMI shielding film with ultralow reflection (<0.05 dB or 1.5%), ultrahigh absorption (>70 dB or 98.5%), and superior shielding (>70 dB or 99.99999%) across triple mmWave frequency bands with a thickness of 400 µm. By integrating a magnetic composite layer (MCL), a conductive patterned grid (CPG), and a double‐walled carbon nanotube film (DWCNTF), specific resonant frequencies of electromagnetic waves are transmitted into the film with minimized reflection, and trapped and dissipated between the CPG and the DWCNTF. The design factors for resonant frequencies, such as the CPG geometry and the MCL refractive index, are systematically investigated based on electromagnetic wave propagation theories. This innovative approach presents a promising solution for effective mmWave EMI shielding materials, with implications for mobile communication, radar systems, and wireless gigabit communication.

Parameter Extraction of Accelerated Moving Targets under Non-Quasi-Axial Incidence Conditions Based on Vortex Electromagnetic Wave Radar

Vortex electromagnetic wave radar carrying orbital angular momentum can compensate for the deficiency of planar electromagnetic wave radar in detecting motion parameters perpendicular to the direction of electromagnetic wave propagation, thus providing more information for target recognition, which has become a hot research field in recent years. However, existing research makes it difficult to obtain the acceleration and rotation centers of targets under non-quasi-axial incidence conditions of vortex electromagnetic waves. Based on this, this article proposes a variable speed motion target parameter extraction method that combines single element and total element echoes. This method can achieve three-dimensional information extraction of radar targets based on a uniform circular array (UCA). Firstly, we establish a non-quasi-axis detection echo model for variable-speed moving targets and extract echoes from different array elements. Then, a single element echo is used to extract the target’s range slow time profile and obtain the target’s rotation center z coordinate. We further utilize the target linear, angular Doppler frequency shift extremum, and median information to extract parameters such as target acceleration, tilt angle, rotation radius, and rotation center x and y coordinates. We analyzed the impact of different signal-to-noise ratios and motion states on parameter extraction. The simulation results have verified the effectiveness of the proposed algorithm.

Mitigation of reentry blackout via gas injection in arc-heating facility

Communication blackouts during atmospheric reentry pose significant challenges to the safety and adaptability of spacecraft missions. This phenomenon, caused by the attenuation of electromagnetic waves by the plasma surrounding the spacecraft, disrupts communication with ground stations or orbiting satellites. Therefore, it is crucial to decrease the plasma density in the vicinity of the spacecraft to ensure an unobstructed electromagnetic wave communication path. This study proposes a methodology that involves the injection of gas from the vehicle’s wall to create an insulating layer near the surface. This thin layer maintains lower temperatures and reduced plasma density, enabling electromagnetic wave propagation without attenuation. Practical experiments were conducted in an arc-heating facility to simulate atmospheric reentry conditions. The results of the experiments provided empirical evidence of the effectiveness of the technique in mitigating communication blackout phenomena. Numerical fluid analysis within the wind tunnel chamber validated the formation of an air film layer near the experimental model owing to the injected gas. Schlieren imaging revealed distinctive jet shapes, which corroborated the findings of the numerical analysis. The wind tunnel tests that simulated atmospheric reentry environments confirmed the formation of an air film layer through gas injection, which substantiates the reduction in communication blackout. These results have the potential to improve communication reliability in space transport.

Recent Advances in Electromagnetic Metamaterials and Metasurfaces for Polarization Manipulation

Abstract Polarization is an important characteristic of electromagnetic waves that has been exploited in many areas of wave manipulations. While effective control of polarization is highly demanded in various applications, traditional polarization converters have drawbacks such as large volume, narrow operating frequency band, low efficiency, and high losses, hindering themselves from practical applications. Metamaterials and metasurfaces are recently developed artificially structured electromagnetic materials constructed by three- or two-dimensional arrays of meta-atoms with tailored electromagnetic responses, exhibit great potential in controlling the propagation of electromagnetic waves and are highly suitable for flexible control of polarization. Here, we review the recent developments in the field of electromagnetic metamaterials and metasurface for polarization manipulation, focusing on their operation principles and practical applications. We discussed the research progress of chiral metamaterials and anisotropic metasurfaces, and also summarized the achievements of metasurfaces for comprehensive manipulation polarization and phase in recent years. We further summarize the recent achievements on the diversified polarization manipulation functions of metasurfaces. Finally, we discuss reconfigurable metasurfaces that can dynamically control the polarizaiton and wavefronts of electromagnetic waves, including not only electrically reconfigurable metasurfaces with constitutional meta-atoms locally tuned by external stimuli, but also time-modulated metasurfaces exploiting the temporal dimension by applying dynamic switching of the coding sequences. Finally, we look forward to the possible future directions and existing challenges in this rapidly developing field.

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.

Loss Analysis of the Electromagnetic Metamaterial Applied to Antenna Size Reductions

The research of transformation electromagnetics uses spatial coordinate transformation method to transform Maxwell’s equations for the propagations of electromagnetic waves in space, thereby achieving the goal of designing the path of electromagnetic waves, which eventually leads to a more complex tensor design of its constitutive parameters of metamaterials. This demand for artificial design of material parameters has been combined with the rapid development of micro-scale, molecular-scale, and atomic-scale experimental engineering techniques in recent years, enabling metamaterials to be developed, fabricated, and applied in various frontier fields. In this paper, the metamaterial electromagnetic wave concentrator used to reduce the antenna size is mainly discussed and detailed simulations and researches on the electromagnetic lossy conditions of the metamaterial parameters are given, which can better verify the electromagnetic scattering performance under actual engineering conditions. Solutions and quantitative simulations for the attenuation characteristics are also provided, which can deepen the research on the engineering performance of the metamaterial electromagnetic transformation devices.

Circular dichroism in nonlinear topological Weyl semimetals

In recent years, the field of topological photonics has emerged as a promising area of research due to its potential for the development of new photonic devices with unique properties. Topological Weyl semimetals (TWSs), which are characterized by the presence of Weyl points in their electronic band structure, are one such example of a material with interesting topological properties. In this study, Kerr and Faraday rotations were used to determine the nonlinear characteristics of TWSs. We focused on surfaces where no Fermi arcs are involved, so that Maxwell’s equations would contain some peculiar topological terms. In Weyl semimetals with a specific topology, the distance between Weyl nodes aligned along the z-direction functions as a magnet. This results in a significant polar Kerr/Faraday rotation effect that is proportional to the separation distance, when light is directed onto the surface of the TWS that lacks Fermi arc states. Conversely, when the light is directed onto a surface with Fermi arc states, the Voigt effect is quadratically proportional to the separation distance. We considered electromagnetic wave propagation in a nonlinear Kerr-type medium. We have derived and solved the linear and nonlinear Helmholtz equations for TWSs using the tanh method. Our findings reveal that wave solutions could have some potentially significant implications for the design and optimization of photonic devices based on TWSs.

Spatiotemporal energy‐density distribution of time‐reversed electromagnetic fields

AbstractTime reversal exploits the invariance of electromagnetic wave propagation in reciprocal and lossless media to localize radiating sources. Time‐reversed measurements are back‐propagated in a simulated domain and converge to the unknown source location. The focusing time (i.e. the simulation instant at which the fields converge to the source location) and the source location can be identified using field maxima, entropy, time kurtosis, and space kurtosis. This paper analyses the spatial energy‐density distribution of time‐reversed electromagnetic fields by introducing a convergence metric based on the spatial average and variance of the energy density. It is analytically proven that the proposed metric identifies the focusing time and the source location, with direct links to the source frequency content. The analytical results are verified in a free‐space numerical simulation and the proposed metric is then compared to existing ones in a simulated inhomogeneous medium. Next, this metric is applied and compared in an experimental case study to localize electromagnetic interference sources. The proposed metric outperforms existing ones to identify the focusing time and can also be used to locate the source. Finally, because of its tensorial nature, it can handle anisotropic media, opening the door to quantitative analyses of time‐reversal focusing in metamaterials.

Langmuir wave dynamics and plasma instabilities: Insights from generalized coupled nonlinear Schrödinger equations

This study aims to tackle the generalized coupled nonlinear Schrödinger ([Formula: see text] – [Formula: see text]) equations, with a focus on understanding their physical significance and stability, especially in the realm of plasma physics. These equations are crucial for grasping the complex dynamics of wave interactions within plasma systems, which are fundamental for phenomena like wave-particle interactions, turbulence, and magnetic confinement. We employ analytical methods such as the generalized rational ([Formula: see text]at) and Khater II ([Formula: see text]hat.II) techniques, along with characterizing the system using Hamiltonian principles, to carefully examine the stability of solutions. The relevance of this model extends across various plasma phenomena, including electromagnetic wave propagation, Langmuir wave dynamics, and plasma instabilities. By applying these analytical techniques, we derive solutions and investigate their stability using Hamiltonian dynamics, providing valuable insights into the fundamental behavior of nonlinear plasma waves. Our findings reveal the existence of stable solutions under specific conditions, thus advancing our understanding of plasma dynamics significantly. This research carries significant implications for fields such as plasma physics, astrophysics, and fusion research, where a deep understanding of plasma wave stability and dynamics is crucial. Essentially, our study represents a scholarly effort to offer fresh perspectives on the behavior of [Formula: see text] – [Formula: see text] equations within plasma systems, contributing to the academic discourse on plasma wave phenomena.

Sandwich-Structured Mxene/Waste Polyurethane Foam Composites For Highly Efficient Electromagnetic Interference, Infrared Shielding and Joule Heating.

Electromagnetic interference (EMI) shielding and infrared (IR) stealth materials have attracted increasing attention owing to the rapid development of modern communication and military surveillance technologies. However, to realize excellent EMI shielding and IR stealth performance simultaneously remains a great challenge. Herein, a facile strategy is demonstrated to prepare high-efficiency EMI shielding and IR stealth materials of sandwich-structured MXene-based thin foam composites (M-W-M) via filtration and hot-pressing. In this composite, the conductive Ti3C2Tx MXene/cellulose nanofiber (MXene/CNF) film serves as the outer layer, which reflects electromagnetic waves and reduces the IR emissivity. Meanwhile, the middle layer is composed of a porous waste polyurethane foam (WPUF), which not only improves thermal insulation capacity but also extends electromagnetic wave propagation paths. Owing to the unique sandwich structure of "film-foam-film", the M-W-M composite exhibits a high EMI shielding effectiveness of 83.37dB, and in the meantime extremely low emissivity (22.17%) in the wavelength range of 7-14µm and thermal conductivity (0.19W m-1 K-1), giving rise to impressive IR stealth performance at various surrounding temperatures. Remarkably, the M-W-M composite also shows excellent Joule heating properties, capable of maintaining the IR stealth function during Joule heating.

Research on high-power and high-efficiency emission of cross-well electromagnetic logging

Cross-well electromagnetic (EM) logging has useful implications in oil, gas, and water monitoring, as well as carbon sequestration estimation. Difficulties in the efficient propagation of EM waves through a steel casing inhibit cross-well EM logging at distances greater than 300 m. This study investigates whether high-power transmission and high-efficiency transmitting antennas can resolve the challenges of long-distance cross-well EM logging through steel casings. Theoretical analysis shows that the emission moment should be at least 12 000 A·m2. By calculating the equivalent relative permeability and selecting appropriate coil materials and magnetic cores, the maximum emission magnetic moment can realize a high-power transmission. Based on series and parallel resonant circuits and the AC/DC cable core multiplexing power supply method, the effective transmission bandwidth is broadened and transmission efficiency is increased three-fold. The emission unit is fabricated and tested with a single, fiberglass, and double casing. We observed that the cross-well EM technology performs better for nonmetal casing wells than for metal casing wells. The amplitude and phase curves between two fiberglass casing wells in the range of 425 m are quite smooth. However, the receiving signals in the double-layer steel casing drop to only a few tenths of the value in the fiberglass casing wells, highlighting the difficulty of long-distance EM-wave transmission when using steel casings. Thus, studies on EM transmission through four or more layers of steel casings should be conducted in the future.

Numerical investigation of a plasma-dielectric-plasma waveguide with tunable Fano resonances

Resonance and interference phenomena in waveguide systems are remarkable for control of electromagnetic wave propagations, with extensive applications in many areas. This paper introduces a plasma-dielectric-plasma (PDP) waveguide supporting multiple Fano resonances, made of a tooth cavity directly connected to a straight waveguide and a rectangle cavity with plasma holes. Different from metal-insulator-metal (MIM) waveguides at the near-infrared band with nanoscales, the PDP works in the microwave regime and with centimetre dimension. Furthermore, it has a prominent advantage in tunability due to inherent properties of gaseous discharge plasmas. A finite element method is adopted to study transmission responses and field distributions in details. Also, coupled mode and standing wave theories are applied to confirm the validity of numerical results and theoretically analyze Fano spectra, respectively. Results indicate that the number and position of Fano resonances can be modulated by adjusting the number of plasma holes and altering the plasma frequency, respectively. Also, the independent tunability of multiple Fano resonances can be verified by the additional structure. The numerical simulations provide a reference for plasma to modulate electromagnetic waves and may open up a new path for developing tunable microwave devices, especially in the parallel processing of microwave signals.

Attenuation of electromagnetic wave propagation in Martian dust storms

Attenuation of electromagnetic wave propagation in Martian dust storms

Modelling of electromagnetic wave propagation at free space-human skin interface

The proliferation of the ambient environment with many wireless communication infrastructures has constituted a source of concern, at least from health point of view. Hence, there is a need for the investigation of electromagnetic wave interaction with human tissue. This paper models electromagnetic wave propagation at the free-space-human tissue interface, in an attempt to understand how electromagnetic waves interact with the human skin. Maxwell’s equations were used to derive the governing equations of propagating electromagnetic waves in free space while the solution of the boundary-value problem arising from the incident electromagnetic wave at the free space-human tissue interface was found through the use of appropriate boundary conditions. The solution led to the emergence of four Fresnel equations, a pair each for perpendicular and parallel polarizations of the incident wave, at the boundary. Through the use of the Fresnel equations obtained, components of the incident electromagnetic wave power at the boundary can be quantified. Typical profiles of the normalized reflected and absorbed powers at the free space-human skin interface at 28, 60, and 73 GHz were computed, using measured values of permittivity of human tissue. It is found that the total absorption of the power of the incident wave by the human skin occurs when the angle of incidence is between 690 and 770 for the three frequencies used. This is irrespective of the polarization of the incident wave. Information on such distinct angles of incidence for total absorption of power does not appear to exist in the literature as they represent new, previously unreported facts in the existing body of research. Furthermore, computed profiles of reflected power versus incidence angle displayed here, for perpendicular polarization, demonstrate strong alignments with established literature, thus reinforcing the credibility of the results presented in this paper.

Nonlinearity in the Medium for Electromagnetic Wave Propagation Induced by Quantum Mechanical Interaction of the Field With Finite-State Atoms

We consider the interaction between a classical time varying electric field with the atomic electrical dipole moment operator of a finite state atom and calculate approximately the mixed state evolution of the atom with such an interaction Hamiltonian upto quadratic orders in the external classical electric field using Schrodinger’s equation for mixed state evolution. From this approximate expression for the state evolution, we evaluate the average atomic electric dipole moment as a linear-quadratic function of the electric field. Later one we also take into account Brownian motion bath noise that couples to the atomic dynamics, so that the Schrodinger equation dynamics gets modified to the Lindblad dynamics of an open quantum system, ie the master equation. From the average atomic dipole moment, we obtain an expression for the average polarization field of atoms constituting the medium through which the classical electromagnetic wave propagates. This average polarization is a linear-quadratic causal functional of the electric field. The resulting Maxwell equations for wave propagation, taking into account this polarization current density, thus acquire a quadratic nonlinearity which can be used to explain higher harmonic frequencies at the output of an optical fiber when the input is excited by the electric field coming from a mono-chromatic laser. We are then also able to calculate the mean square fluctuations in the polarization field using the evolving atomic state and hence the electric field propagating through the medium of atoms, acquires quantum fluctuations which can be used to explain time-varying random shifts in the spectral lines. As mentioned above, we include in this article an extension of this problem to the case when there is white Gaussian noise corrupting the state evolution dynamics of the atom and also the case when there is a pairwise interaction between the spin dipoles of atoms at two different locations. In the former case, we derive an approximate formula for the polarization field as well as its temporal statistical correlations and we show how this computation can be extended to the latter case too. When there is pairwise interaction between the atomic spins, we use a version of the approximate quantum Boltzmann equation to calculate the first and second order marginals of the atomic states which is then used to compute the average polarization as well as its spatio-temporal correlations. Temporal correlations using second marginals of the atomic states cannot be computed using classical probabilistic methods owing to Heisenberg uncertainty, so we propose a sequential measurement based strategy involving computation of the joint probabilities of the atomic spin components at two different times by first measuring one component of the spin, allowing for state collapse and then following it up with nonlinear time evolution from the collapsed two particle state using the quantum Boltzmann equation, followed further by measurement of another component of the spin at the second time.

An empirical modeling of the D region ionosphere based on [formula omitted]

The electron density (Ne) in the D region, although its value is much smaller than that in the F region, has a highly important effect on electromagnetic wave propagation by energy absorption due to high-frequency collisions between electron-molecular, electron-ionic, molecular-ionic and so on. Solar activity is the main source of ionization in the D region of the ionosphere. The observed Ne during 2008–2015 by the Kunming station (25.6°N, 103.8°E) medium radar (MF radar) is utilized to analyze its strong relationship with solar activity. Then, the relationship between them is employed to establish an empirical model in this study. The Ne in the D region is enhanced with increasing height and time towards noon, and the solar zenith angle is increasingly smaller towards noon. The averages of Ne at several heights below and above 76 km show that the D region ionosphere up to 76 km is more strongly controlled by solar radiation and less strongly controlled below 76 km. According to the above, an empirical model is established based on the relationship between the D-region ionosphere and solar activity index F107.

The Janus layered metamaterial modulated by liquid crystal with multitasking of different logic gates and mode-switching biosensing

A Janus layered metamaterial (JLM) operating in the terahertz (THz) region is proposed, which increases the direction dimension to manipulate the propagation of electromagnetic waves (EWs) through the introduction of nonlinear Kerr media. It achieves multi-scale multitasking with different logic gates and mode-switching biosensing, making a breakthrough on traditional single-function and single-scale THz devices. Due to the electro-optical effect, the liquid crystal (LC) is adjusted by the electric field, and the sharp transmission peak generated by the located defect mode resonance can be used to realize the forward scale logic product gate and the backward scale exclusive NOR gate. In addition, by locking the sharp transmission peak, the biosensing can have different detection ranges under the LC modulation. Therefore, when EWs propagate forward and backward, the mode switching of different biosensing categories with a glucose concentration of 300–550 g/l, creatinine concentration of 80.9–85.28 μmol/l, and the blood component in refractive index of 1.33–1.38 can be realized. The JLM proposed provides a possibility for the design of the chip-level compact optical integrated circuit and offers a new idea for multi-purpose biomedical detection, owning certain research value.

Reciprocal action of natural bianisotropy and artificial chirality on electromagnetic propagation in medium

Background. The present article investigates the reciprocal action of specific medium effects on electromagnetic waves propagation. The object of study is a moving dielectric, which at rest already demonstrate bianisotropic properties, i. e., it is a synthetic material, e. g., chiral media with Ω-particles. Bianisotropic material equations are the most general for describing the effects of electromagnetic waves interaction with complex medium. Studying and analyzing them is proving to be a notable scientific problem. Natural bianisotropy is a property of simple media under special conditions (state of motion, internal currents and diffusion processes), whereas artificial bianisotropy is an inherent property of the synthetic material itself (composite material, material with different metaparticles).
 Aim. The main goal of the work is to generalize the already available data. On it basis, then, obtain analytical expressions, which can be effectively used for the experiments designing, creating new computational techniques for solving direct and inverse electromagnetic diffraction problems.
 Methods. In this paper, analytical methods are applied to obtain the resulting close-form expressions.
 Results. Three classes of effects have been identified that have a significant reciprocal effect on each other: gyrotropy, spatial dispersion, and temporal dispersion. In this article it was shown that the gyrotropy of the medium has not only a simple additive effect, but under some, specific conditions, can be related to the system emergence.
 Conclusion. The reciprocal action of the spatial dispersion of the moving chiral medium, generally has different scales in range. Temporal dispersion was investigated, which does not have a simple additive property, because even an isotropic medium acquires fundamentally new material properties of bianisotropy when it moves.

Elucidating the coherent and incoherent reflection of plane-waves in finite thickness media: a practical pedagogical application

The propagation of light through a thin film interfaced between two semi-infinite media serves as a compelling illustration for elucidating electromagnetic wave interactions with matter at the undergraduate level. Despite its pedagogical significance and diverse technological applications, this model often receives inadequate attention in foundational electromagnetism literature, limiting early student exposure to this emblematic concept. In this pedagogical initiative, we present a comprehensive analysis of electromagnetic wave propagation through a dielectric medium positioned between semi-infinite media. We examine interference phenomena arising from back-and-forth reflected waves within the dielectric, focusing on the coherent and incoherent reflection regimes as limiting cases. Employing rigorous analytical treatment, we delineate transmittance and reflectance profiles, offering students a lucid understanding of how the refractive index’s real and imaginary components compete and manifest under specific conditions. This analytical approach enhances students’ comprehension of electromagnetic wave behavior within diverse mediums. Furthermore, we extend this theoretical foundation to practical applications, emphasizing renewable energy contexts. By calculating absorptance, we estimate the maximum photo-generated current and power conversion efficiency of a prototype solar cell, establishing a tangible link between theoretical knowledge and real-world solar energy utilization.

An exact in time Fourier pseudospectral method with multiple conservation laws for three-dimensional Maxwell’s equations

Maxwell’s equations describe the propagation of electromagnetic waves and are therefore fundamental to understanding many problems encountered in the study of antennas and electromagnetics. The aim of this paper is to propose and analyse an efficient fully discrete scheme for solving three-dimensional Maxwell’s equations. This is accomplished by combining Fourier pseudospectral methods in space and exact formulation in time. Fast computation is efficiently implemented in the scheme by using the matrix diagonalisation method and fast Fourier transform algorithm which are well known in scientific computations. An optimal error estimate which is not encumbered by the CFL condition is established and the resulting scheme is proved to be of spectral accuracy in space and exact in time. Furthermore, the scheme is shown to have multiple conservation laws including discrete energy, helicity, momentum, symplecticity, and divergence-free field conservations. All the theoretical results of the accuracy and conservations are numerically illustrated by two numerical tests.