Electromagnetic Wave Propagation Research Articles

An Efficient and Accurate Algorithm for Electromagnetic Wave Propagation Modeling Based on Wavelet Transforms

An Efficient and Accurate Algorithm for Electromagnetic Wave Propagation Modeling Based on Wavelet Transforms

Ultra‐wideband imaging with an improved backward projection algorithm for far‐field applications

AbstractUltra‐wideband (UWB) radar imaging is widely used in penetration detection, target location and detection, and vital monitoring because of its high interference immunity and excellent target recognition with high resolution. In this paper, we report the design of a UWB stepper radar imaging system by using a vector network analyzer and a specially designed novel Vivaldi antenna for far‐field imaging applications. An anti‐attenuation backward projection (AA‐BP) algorithm is proposed to alleviate the attenuation impact of electromagnetic wave propagation. The AA‐BP algorithm and the specially designed Vivaldi antenna are jointly applied in our experiments on multiple targets through wall imaging in both free space and multiple‐path propagation environments. The experimental results show that our reported imaging system achieves desirable performances of far‐field imaging.

Transient Simulation of Electromagnetic Wave Propagation in Plasma Based on Dynamic Drude Model

Transient Simulation of Electromagnetic Wave Propagation in Plasma Based on Dynamic Drude Model

Evaluation of Antenna Pattern Measurement of HF Radar using Drone

The High-Frequency Radar (HFR) is an equipment designed to measure real-time surface ocean currents in broad maritime areas.It emits radio waves at a specific frequency (HF) towards the sea surface and analyzes the backscattered waves to measure surface current vectors (Crombie, 1955; Barrick, 1972).The Seasonde HF Radar from Codar, utilized in this study, determines the speed and location of radial currents by analyzing the Bragg peak intensity of transmitted and received waves from an omnidirectional antenna and employing the Multiple Signal Classification (MUSIC) algorithm. The generated currents are initially considered ideal patterns without taking into account the characteristics of the observed electromagnetic wave propagation environment. To correct this, Antenna Pattern Measurement (APM) is performed, measuring the strength of signals at various positions received by the antenna and calculating the corrected measured vector to radial currents.The APM principle involves modifying the position and phase information of the currents based on the measured signal strength at each location. Typically, experiments are conducted by installing an antenna on a ship (Kim et al., 2022). However, using a ship introduces various environmental constraints, such as weather conditions and maritime situations. To reduce dependence on maritime conditions and enhance economic efficiency, this study explores the possibility of using unmanned aerial vehicles (drones) for APM. The research conducted APM experiments using a high-frequency radar installed at Dangsa Lighthouse in Dangsa-ri, Wando County, Jeollanam-do. The study compared and analyzed the results of APM experiments using ships and drones, utilizing the calculated radial currents and surface current fields obtained from each experiment.

Classical radiation fields for scalar, electromagnetic, and gravitational waves with spacetime-symmetry breaking

An effective field theory framework is used to investigate some Lorentz-violating effects on the generation of electromagnetic and gravitational waves, complementing previous work on propagation. Specifically we find solutions to a modified, anisotropic wave equation, sourced by charge or fluid matter. We derive the radiation fields for scalars, classical electromagnetic radiation, and partial results for gravitational radiation. For gravitational waves, the results show longitudinal and breathing polarizations proportional to coefficients for spacetime-symmetry breaking.

Экспериментальные исследования распространения электромагнитных волн в контуре заземления подстанции

Experimental investigations of the propagation of electromagnetic waves in the grounding wire were carried out at the operating 150 kV substation. The wave propagation velocities obtained during the experiment are in the range of 50–100·106 m/s. Thus, the obtained wave propagation velocity along the grounding grid of the substation is several times less than the speed of light, which can radically change the design approaches of the grounding in term of lightning protection.

Design Simulation of Circular Photonic Crystal Structures for the Development of Biomedical Sensor Based on Finite Difference Method

Optical analysis of a circular photonic crystal structure consisting of a metal-dielectric layer and a defect layer sandwiched between two dielectric layers has been carried out using the Finite Difference Frequency Domain (FDFD) method and the Finite Difference Time Domain (FDTD) method. The FDTD method can describe the propagation of electromagnetic waves on the structure at any time, while the FDFD method can describe the characteristics of the wave interaction with the structure in a steady state. We observed strong resonances at certain wavelengths when using three different dielectric materials: , , and . The simulation results show a change in the resonance peak in the sensing material in the form of normal blood and blood-containing glucose in the defect layer for concentration: . The use of three different dielectric materials produces different sensitivity values. The highest sensitivity value when using material that produces a sensitivity value of at the refractive index intervals . The simulation results can be used to build biomedical sensors that measure blood sugar levels.

Design Simulation of Multilayer Structures for the Development of Biosensor Based on Transverse Matrix Method

Simulation of electromagnetic wave propagation on layered metal-dielectric structures using analytical methods is a study that continues to be developed because it involves strict mathematical equations with exact results. In this study, the transfer matrix method was developed to analyze the dielectric-metal-metal-dielectric structure through the reflection profile. The emergence of the Surface Plasmons Resonance (SPR) phenomenon causes a minimum reflectance whose changes are analyzed through variations in optical and physical parameters. The simulation shows that the minimum reflectance angle occurs at an angle , indicating the existence of the SPR phenomenon in the condition . The choice of metal materials, namely gold and silver, resulted in a shift in the reflectance curve, and an increase in the thickness of the adhesive layer caused a shift in the reflectance curve towards a smaller angle. Changes in the refractive index of the upper dielectric material are important for biosensor development, namely a shift in the reflectance curve with a linear response at the interval of refractive index .

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

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

Graviton to Photon Conversion in Curved Space-Time and External Magnetic Field

The suppression of relic gravitational waves due to their conversion into electromagnetic radiation in a cosmological magnetic field is studied. The coupled system of equations describing gravitational and electromagnetic wave propagation in an arbitrary curved space-time and in external magnetic field is derived. The subsequent elimination of photons from the beam due to their interaction with the primary plasma is taken into account. The resulting system of equations is solved numerically in the Friedman–LeMaitre–Robertson–Walker metric for the upper limit of the intergalactic magnetic field strength of 1 nGs. We conclude that the gravitational wave conversion into photons in the intergalactic magnetic field cannot significantly change the amplitude of the relic gravitational wave and their frequency spectrum.

An Optical-Electronic-Catalytic Coupled Multi-Physical Simulation for Sunlight-Driven CO2 Reduction Device Based on Light Absorbers Patterned with Island Electrocatalysts

Photoelectrochemical (PEC) reduction of CO2 to value-added chemicals is a promising approach to convert solar energy but it is often suffered from sluggish kinetics and photocorrosion at the semiconductor-electrolyte interface.1, 2 In general, there are two requirements for a good performing solar-driven CO2 reduction: i) effective catalysts for a fast surface redox reaction and ii) an effective semiconductor/catalyst interface for rapid charge transfer across interfaces.3 The deposit of a continuous electrocatalyst layer on the photoabsorber surface can reduce kinetic overpotentials for CO evolution reaction (COER) and can enhance the photoelectrode stability. However, the optical obscuration significantly attenuates the magnitude of the incident illumination. Reducing the coverage (f c) of the catalyst on the photoabsorber surface can reduce the optical obscuration but worsen the reaction kinetics. Moreover, the pinch-off effect occurs as the size of the catalyst is small enough to provide a facile path for carriers to transport across interfaces. The PEC CO2 reduction with the utilization of the pinch-off effects could potentially be advantageous to balance the kinetics and the optical absorption. Understanding the trade-offs between the reduction in photocurrent density due to optical obscuration and the decrease in kinetic overpotentials due to improved active area is important in optimizing PEC CO2 reduction devices.To elucidate the effects of the optical performance, interfacial carrier transport, and electrochemical activity for the PEC CO2 reduction, three possible interfacial configurations in PEC were considered in this study: i) Bare p-Si photocathode case. The bare p-Si photocathode immersed in aqueous electrolyte and CO2R occurs at the semiconductor-electrolyte (SC/E) interface; ii) Layered catalyst case. The continuous layer catalyst is deposited on the surface of p-Si photocathode and forms a semiconductor-metal (SC/M) interface; iii) Patterned catalyst case. Producing a patterned catalyst with a low geometric coverage fraction on the surface of p-Si photocathode. The Schottky junctions with a low barrier height formed by the SC/M are surrounded by the Schottky junctions with a high barrier height formed by the SC/E. We developed a multiphysics model based on the finite element method, including electromagnetic wave propagation, charge transport in bulk semiconductor, species transport in the electrolyte, and charge-transfer kinetics of surface redox reactions.The optical performance and electrochemical performance of CO2R reduction were compared in the three cases. Under the bare p-Si case, the saturation photocurrent densities (J sa) and the onset potential (V on) were -13.40 mA/cm2 and -0.80 V vs. RHE at -1 mA/cm2, respectively. Under the layered catalyst case, the J sa and the V on were -0.84 mA/cm2 and -0.50 V vs. RHE at -0.10 mA/cm2, respectively. Under the patterned catalysts case (f c is 0.1 in this case), the J sa is -12.30 mA/cm2 and V on is -0.69 V vs. RHE at -1 mA/cm2. The magnitude of J sa is influenced by the extent of light obscuration and the magnitude of V on is influenced by the photoelectrode activity and the pinch-off effects. The V on for the patterned case is higher than that of the bare p-Si case due to the improved electrode activity combined with the pinch-off effects. In the bare p-Si case and the patterned catalyst case, the CO2 mass transfer limits the CO partial current density (J CO) to further increase due to high J sa while CO2 mass transfer is not the limitation for COER at high overpotentials for the layered catalyst case due to significant light obscuration. The pinch-off effect also increased the applied voltage corresponding to the maximum J CO for the patterned case (-1.21 V vs. RHE) compared to that for the bare p-Si case (-1.35 V vs. RHE) due to the deceased transport resistance of electrons.The influence of different interfacial configurations, solar concentration ratio, different coverage of catalysts, and different sizes of catalysts for optical loss, pinch-off effect, CO2 mass transfer, current distribution at interfaces, and electrochemical performance are discussed in detail for the optimal design photoelectrode. This framework allows us to provide design guidelines for PEC CO2 reduction devices.

Experimental and theoretical study on the electromagnetic shielding performance of polymer nanocomposites consisting of basalt fiber and CNTs

In this paper, we substantiated the mechanism behind the absorption and multiple reflection shielding in the nanocomposites (2 mm in thickness) consisting of basalt fiber loaded with carbon nanotubes and polydimethylsiloxane when exposed to an electromagnetic wave of the X-band frequency (8.2–12.4 GHz). The experimental results confirmed that the interface polarization, capacitor-like structure, together with internal conducting networks contributed to the electromagnetic shielding effect in the material. Furthermore, calculation and simulation were employed to analyze the propagation of electromagnetic wave within the nanocomposites, giving direct evidence that the electromagnetic irradiation could be efficiently absorbed while the reflection loss played a marginal role in this process. The findings of this study shed light on the structural design and optimization of the nanocomposites for high-efficiency electromagnetic shielding.

Electromagnetic property selection for GPR modelling in corrosive concrete environments

Understanding the mechanisms that alter the ground penetrating radar (GPR) electromagnetic wave propagation as a result of reinforcement corrosion is pivotal for accurate assessment of the corrosion of reinforced concrete (RC) structures. Nevertheless, the behaviour of the GPR signal during the complex corrosion process is not thoroughly understood. In this study, finite-difference time-domain (FDTD) modelling was used to analyse the effects of corrosion-related parameters, i.e., moisture, chlorides, and corrosion products, on the electric field strength. This study aims to expand the database on numerical simulations of GPR signal behaviour in corrosive environments. It also addresses the knowledge gap in modelling the frequency-dependent properties of concrete and iron oxides. Modelling approach adopted in the study was validated with experimental data obtained on laboratory specimens that correspond to the numerical models in terms of geometry and condition.

Microwave Structural Health Monitoring of the Grouted Connection of a Monopile-Based Offshore Wind Turbine: Fatigue Testing Using a Scaled Laboratory Demonstrator

Offshore wind turbines play a significant role in the expansion of clean and renewable energy. However, their exposure to harsh marine environments and dynamic loading conditions poses significant challenges to their structural integrity. In particular, the grouted connection, serving as the crucial interface between the monopile and the transition piece, is susceptible to cracking and particle washout that can lead to destabilizing grout erosion over time. In this paper, we propose a microwave structural health monitoring (SHM) approach for damage detection in grouted connections based on a stepped-frequency continuous wave radar. The methodology exploits ultra-wideband (UWB) electromagnetic wave propagation in the frequency range from 100 MHz to 2 GHz, where the microwaves propagate along the concrete-type dielectric material guided by the surrounding steel cylinders. For the proof of concept, a scaled laboratory demonstrator was built that realistically models the dynamic loading experienced by a full-scale monopile. The structure was equipped with an UWB radar system using two transmitting and three receiving antennas directly coupled to the grout. For validation, a large number of other sensors, i.e., accelerometers, strain gauges, and acoustic emission sensors have also been installed and measured synchronously during the fatigue test. It is demonstrated here that the proposed SHM methodology offers a nondestructive and real-time method for assessing the structural integrity of the grouted connection directly, actively, and automatically. This has the potential to support predictive maintenance activities in the future.

Coupled hydrogeophysical inversion of an artificial infiltration experiment monitored with ground-penetrating radar: synthetic demonstration

Abstract. In this study, we investigate the use of ground-penetrating radar (GPR) time-lapse monitoring of artificial soil infiltration experiments. The aim is to evaluate this protocol in the context of estimating the hydrodynamic unsaturated soil parameter values and their associated uncertainties. The originality of this work is to suggest a statistical parameter estimation approach using Markov chain Monte Carlo (MCMC) methods to have direct estimates of the parameter uncertainties. Using the GPR time data from the moving wetting front only does not provide reliable results. Thus, we propose to use additional information from other types of reflectors to optimize the quality of the parameter estimation. Water movement and electromagnetic wave propagation in the unsaturated zone are modeled using a one-dimensional hydrogeophysical model. The GPR travel time data are analyzed for different reflectors: a moving reflector (the infiltration wetting front) and three fixed reflectors located at different depths in the soil. Global sensitivity analysis (GSA) is employed to assess the influence of the saturated hydraulic conductivity Ks, the saturated and residual water contents θs and θr, and the Mualem–van Genuchten shape parameters α and n of the soil on the GPR travel time data of the reflectors. Statistical calibration of the soil parameters is then performed using the MCMC method. The impact of the type of reflector (moving or fixed) is then evaluated by analyzing the calibrated model parameters and their confidence intervals for different scenarios. GSA results show that the sensitivities of the GPR data to the hydrodynamic soil parameters are different between moving and fixed reflectors, whereas fixed reflectors at various depths have similar sensitivities. Ks has a similar and strong influence on the data of both types of reflectors. Concerning the other parameters, for the wetting front, only θs and α have an influence, and only at long time steps since the total variance is zero at the very beginning of the experiment. On the other hand, for the fixed reflectors, the total variance is not zero at the very start and the parameters θs, θr, α and n can have an influence from the very beginning of the infiltration. Results of parameter estimation show that the use of calibration data from the moving or fixed reflectors alone does not enable a good identification of all soil parameters. With the moving reflector, the error between the estimated mean value and the exact target value for θr and α is 9 % and 45 %, respectively, and less than 3 % for the other parameters. The best reduction of the size of the parameter distribution is obtained for n, with a posterior distribution 9 times smaller than the prior one. For the others, this reduction ratio varies between 1 and 5. For the fixed reflectors, the estimated mean values are far from the target values for α, θr and n, representing for a reflector located at 120 cm 15 %, 27 %, and 121 %, respectively. On the other hand, when both data are combined, all soil parameters can be well estimated with narrow confidence intervals. For instance, when using both data from the moving wetting front and a fixed reflector located at 120 cm for calibration, the estimated mean values of the errors of all parameters are less than 5 %. Moreover, all parameter distributions are well reduced, with a maximum reduction for Ks, leading to a posterior distribution being 46 times smaller than the prior one, and the worst but still satisfactory being for θr for which the posterior distribution is 8 times smaller than the prior one. The methodology was applied to fine, medium, and coarse sands with very good results, particularly for the finest soil. The thickness of the unsaturated zone was also tested (0.5, 1, and 2 m) and a better estimation of the hydrodynamic parameters is obtained when the water table is deeper. In addition, the height of water applied in the infiltrometry test influences the speed of the test without affecting the performance of the proposed method.

A 3D TLM code for the study of the ELF electromagnetic wave propagation in the Earth's atmosphere

The interest in the study of electromagnetic propagation through planetary atmospheres is briefly discussed. Special attention is devoted to extremely-low-frequency fields in the Earth's atmosphere for its global nature and possible applications to climate monitoring studies among others. In the Earth's case, the system can be considered as a spherical electromagnetic shell resonator in which two concentric and large conducting spheres with a radius around 6300 km are separated by a very small distance of around 100 km, the atmosphere height. A numerical solution using the Transmission Line Method is proposed. The classical spherical-coordinate description is easy to use, however, the important difference in the dimensions along the three coordinate directions causes high numerical dispersion in the results. A Cartesian scheme with equal node size for all directions is used to reduce this undesired dispersion. A pre-processing stage is the key point introduced to lessen the resulting high demand of memory and time calculation and make the solution feasible. A parallelized Fortran code together with pre- and post-processing Python programs to ease the user interface are provided with this work. Details on the Fortran code and the Python modules are included both in the paper and the source codes to allow the use and modifications by other researchers interested in electromagnetic propagation through planetary atmospheres. The program allows calculation of the time evolution of the electromagnetic field at any point in the atmosphere. It includes the possibility of considering multiple time-dependent sources and different homogeneous and inhomogeneous conductivity profiles to model different situations. Profiles to study day-night asymmetries or locally perturbed profiles which have been attributed to earthquakes in the literature are implemented, for instance.

Propagation of Electromagnetic Waves in a Nonlinear Hyperbolic Medium

Propagation of Electromagnetic Waves in a Nonlinear Hyperbolic Medium

Emission spectroscopy diagnosis and discharge characteristics distribution analysis of high-frequency, high-enthalpy inductive coupling plasma generator

To study the electromagnetic properties through reentry plasma on ground, a large-sized inductive coupled plasma generator is designed to produce a long-duration, large size and high temperature plasma flow in a low-pressure vacuum tank. Among all plasma parameters, the spatial distribution of electron density and electron temperature is of utmost importance for analyzing the electromagnetic scattering properties. In this study, we used the emission spectroscopy diagnosis method to explore the aforementioned parameters at two locations: upflow and downflow of the discharge coil in the plasma generator. Experiments were conducted under various discharge conditions for argon, with the panel power ranging from 28 kW to 85 kW. The results showed that, at the upflow of the discharge coil, the electron temperature at the center was higher than that at the edge, exhibiting an arch-shaped profile. However, at the downflow of the discharge coil, the electron temperature at the center was lower than that at the edge, exhibiting a saddle-shaped profile. The electron density exhibited a completely opposite distribution compared to the electron temperature, with higher values at the edge for upflow and higher values at the center for downflow. By varying the panel power, we observed the similar phenomenon: the electron temperature decreased, while the electron density increased with the increase in power. Finally, brief analysis was provided at the end of the paper. This study offered valuable insights into the transition of plasma distribution in a plasma generator, providing a reference for future research on the propagation of electromagnetic waves in plasma sheaths.

Simulation of Electromagnetic Waves in Magnetized Cold Plasma by a Novel BZT-DGTD Method

This work presents a novel discontinuous Galerkin time domain (DGTD) approach based on second-order bilinear <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">z</i> transform (BZT) to analyze the behavior of electromagnetic waves in a magnetized cold plasma. The Maxwell’s equations and current density equation are utilized to formulate the governing mathematical expressions of magnetized plasma, and the BZT approach is employed to construct the time domain iterative formula. The suggested technique outperforms existing methods in terms of stability, performance, and aliasing effect avoidance. The efficacy of the suggested BZT-DGTD approach is investigated by analyzing electromagnetic wave propagation in unmagnetized and magnetized cold plasmas, and a comprehensive comparison is performed with commercial software WCT and COMSOL to validate its practicality. Furthermore, the features of electromagnetic wave propagation in plasma are investigated under numerous circumstances, and these instances are compatible with plasma physics.

Multi-Focus Additive Metalens Based on Complex Coding Principle

The convolution addition principle of encoding metasurface based on traditional theories can only achieve angular deflection of a single beam. In this paper, the encoding mode of the metasurface is extended to the complex domain, and the concept of complex encoding metalens is proposed, which can realize the joint control of the multi-focus and multi-angle in the metalens imaging space. Complex coding reveals the relationship between different bit codes, and the resulting coded metalens is closer to the nature of electromagnetic (EM) wave propagation in physical sense. Using the complex addition theorem to add two metalens with different encoding modes, the new metalens is extended to a higher bit, and has the angular characteristics of the previous two metalenses focal points. At this time, the angle regulation of the multi-focal point is mutually not disturbed. Our proposed complex additive encoding metalens method provides a new idea for the design of multi-focal lenses in the future.