Propagation Of Electromagnetic Signals Research Articles

Coal-gangue recognition for top coal caving face based on electromagnetic detection

Identifying the coal-gangue mixing ratio during top coal caving is essential for automating the coal caving process efficiently. In this article, a block impression reconstruction method is proposed to create 3D models of coal-gangue mixtures with varying gangue ratios and morphological distributions, based on real coal-gangue blocks that reflect actual coal-falling conditions. These 3D models are then input into CST software for electromagnetic forward simulation. The relationship between electromagnetic signal propagation characteristics and gangue ratio is analyzed, resulting in the creation of a coal-gangue mixture electromagnetic signal dataset. An Optuna-XGBoost-based model is then designed to identify the coal-gangue mixing ratio and the recognition performance is firstly verified by using the electromagnetic forward simulation data. Finally, to verify the method’s practicality, a microwave detection test bench for top coal caving is set up and some comparative experiments are conducted. The experimental results indicate that the electromagnetic signals of coal and rock with different gangue contents exhibit significant differences, and the proposed coal-gangue identification model has significant advantages in accuracy and overall performance compared to other competing models.

Development of an innovative patch antenna design and implementation using ENG materials for health care systems and 5G networks

The object of this study is a new design of an overhead microstrip antenna, including Epsilon Negative (ENG) metamaterials and L-shaped parasitic overlays aimed at achieving dual-band operation and improving the performance of modern wireless communication systems. The research is aimed at solving the problem of limited bandwidth and dual-band functionality in conventional antenna designs. This study solves the problem of limited bandwidth and dual-band functionality in conventional microstrip patch antenna designs, which are crucial for modern wireless communication systems. The inclusion of L-shaped parasitic overlays effectively expands the bandwidth in each frequency range. The results indicate significant improvements: at the upper resonant frequency, a 10 dB return loss bandwidth of 27.84 % (2.88–3.81 GHz) and a 3 dB axial ratio bandwidth of 5.05 % (2.90–3.05 GHz) are achieved, while at the lower resonant frequency, a return loss bandwidth is 10 dB, which is 6.11 % (2.22–2.36 GHz). These improvements indicate a significant increase in antenna performance compared to conventional designs, which is confirmed by comparing the simulation results with the measurement results. Distinctive features contributing to these results include the use of ENG metamaterials, which improve electromagnetic properties and signal propagation; vertical transitions, which provide efficient dual-band operation; and L-shaped parasitic overlays, which significantly expand bandwidth. These characteristics combine to eliminate the limitations of traditional designs, which makes the proposed antenna suitable for use in a wide frequency range in modern wireless communication systems.

Влияние числа Куранта на результаты численного моделирования распространения сигналов в недиспергирующих однородных средах

The paper is devoted to the study of the connection between the numerical dispersion arising in FDTD modeling of electromagnetic signal propagation in nondispersive homogeneous media optically different from vacuum and the Courant number in the 2D case. The main results are formulated in the form of four statements, as well as a number of corollaries and remarks that determine the nature of the numerical dispersion, the optimal value of the Courant number and the limitations of the method. It is proved that the optimal choice of the Courant number eliminates the numerical dispersion and extends the capabilities of the developed numerical algorithm to media, which refractive index is lesser than refractive index of vacuum, as well as media with negative refraction.

Investigating Equatorial Plasma Depletions through CSES-01 Satellite Data

Ionospheric plasma density irregularities, which are one of the primary sources of disturbance for the Global Navigation Satellite System, significantly impact the propagation of electromagnetic signals, leading to signal degradation and potential interruptions. In the equatorial ionospheric F region after sunset, certain plasma density irregularities, identified as equatorial plasma bubbles, encounter optimal conditions for their formation and development. The energy spectra of electron density fluctuations associated with these irregularities exhibit a power-law scaling behavior qualitatively similar to the Kolmogorov power law observed in fluid turbulence theory. This intriguing similarity raises the possibility that these plasma density irregularities may possess turbulent characteristics. In this study, we analyzed electron density, temperature, and pressure data obtained from the China Seismo-Electromagnetic Satellite (CSES-01) to delve into the spectral properties of equatorial plasma depletions in the ionospheric F region at an altitude of about 500 km. This research marks the first exploration of these properties utilizing CSES-01 data and focuses on 14 semi-orbits that crossed the equator after midnight (01:00–03:00 LT), characterized by a geomagnetic quiet condition (Kp < 1). The analysis of electron temperature, density and pressure within equatorial plasma depletions revealed power-law scaling behavior for all the selected parameters. Notably, the spectral index values of these parameters are different from each other. The significance of these findings in terms of investigating plasma depletions via magnetic field signatures, as well as their relationship to the occurrence of Rayleigh–Taylor convective turbulence, is examined and discussed.

Electromagnetic signal propagation through lossy media via surface electromagnetic waves.

A theory of surface electromagnetic waves in gradient media exhibiting arbitrary surface gradients of dielectric permittivity and magnetic permeability has been developed. Novel low-loss propagating surface wave solutions have been found in the gradient media in which both dielectric permittivity and magnetic permeability are dominated by their imaginary parts. Several examples of gradient geometries in which the surface wave problem may be solved analytically have been found. Examples of practically useful surface wave geometries spanning from radio communication underwater to UV nanophotonics have been demonstrated.

Features of Propagation and Absorption of Electromagnetic Signals in Periodic Structures of Conducting and Dielectric Layers

Features of Propagation and Absorption of Electromagnetic Signals in Periodic Structures of Conducting and Dielectric Layers

Research on Near-Field Propagation Characteristics of Partial Discharge Electromagnetic Wave Signal in Switchgear

In the authors’ previous research, a new method for partial discharge detection in the switchgear based on near-field detection was proposed. The content of this paper is the continuation of the authors’ previous research. In order to realize the reasonable layout of the near-field magnetic field probe for partial discharge detection in the switchgear, this paper simulates and analyzes the influence of the internal structure of the switchgear on the near-field propagation characteristics of the electromagnetic wave signal generated by partial discharge, and determines the installation position of the near-field probe in the switchgear. Firstly, the propagation characteristics of electromagnetic wave signals in the different media of the switchgear are analyzed, and the switchgear model is established. Then, based on the finite difference time domain method, the influence of different devices in the switchgear on the near-field propagation of the partial discharge electromagnetic wave signal is simulated. The simulation results show that the current transformer, insulator, busbar and cabinet all obviously attenuate the amplitude of the near-field electromagnetic wave signals generated by partial discharge, and the insulator causes obvious signal distortion. Finally, it is determined that the near-field probe can be installed on the inner wall or the right wall near the bottom plate of the switchgear.

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.

High-Resolution Observation of Ionospheric E-Layer Irregularities Using Multi-Frequency Range Imaging Technology

E-region field-aligned irregularities (FAIs) are a hot topic in space research, since electromagnetic signal propagation through ionospheric irregularities can undergo sporadic enhancements and fading known as ionospheric scintillation, which could severely affect communication, navigation, and radar systems. However, the range resolution of very-high-frequency (VHF) radars, which is widely used to observe E-region FAIs, is limited due to its bandwidth. As a technology that is widely used in atmosphere radars to improve the range resolution of pulsed radars by transmitting multiple frequencies, this paper employed the multifrequency radar imaging (RIM) technique in a Wuhan VHF radar. The results showed that the range resolution of E-region FAIs greatly improved when compared with the results in traditional single-frequency mode, and that finer structures of E-region FAIs can be obtained. Specifically, the imaging results in multifrequency mode show that E-region FAIs demonstrate an overall descending trend at night, and it could be related to the tides or gravity waves due to their downward phase velocities or even driven by downwind shear. In addition, typical quasi-periodic (QP) echoes with a time period of around 10 min could be clearly seen using the RIM technique, and the features of the echoes suggest that they could be modulated by gravity waves. Furthermore, the RIM technique can be used to obtain the fine structure of irregularities within a short time period, and the hierarchical structure of E-region FAIs can be easily found. Therefore, the multifrequency imaging RIM technique is suitable for observing E-region FAIs and their evolution, as well as for identifying the different layers of E-region FAIs. Combined with the RIM technique, a VHF radar provides an effective and promising way to observe the structure of E-region FAIs in more detail to study the physical mechanism behind the formation and evolution of ionospheric E-region irregularities.

Spatiotemporal Search for Pulsed Radiation in the Photon Flux Detection Mode with Prolonged Observation Time of the Decomposition Element

The development of science and technologies of microwave frequencies (UHF) has contributed to the fact that the use of ultrawideband (UWB) pulsed signals has emerged as a separate scientific and technical area of radiophysics, requiring a deeper study of the methods of formation, emission, reception and processing of such signals. Aperture radiators are mainly used to transmit UWB signals. This type of emitters is a variety of modifications of mirror antennas, horn antennas of various shapes and profiles, open waveguides, planar and conformal antenna arrays, as well as lens antennas. The classical theory of analysis of radiation and propagation of electromagnetic signals is well known, but its application to the synthesis of UWB emitters in the time domain often becomes too cumbersome and incorrect. Progress in the fields of radar, communications, and radio astronomy in the 1960s stimulated the creation of aperture theory based on physical optics approaches. This theory makes it possible to analyze and calculate the characteristics of mirror radiators and antenna arrays with sufficient accuracy for practical application. It is often possible to use the aperture theory to analyze some horn emitters that have a large radiation surface relative to the spatial dimensions of pulsed signals.

Three-Dimensional Ray-Based Tomographic Approach for Contactless GPR Imaging

This paper proposes a three-dimensional imaging approach for contactless ground penetrating radar surveys. The imaging problem is formulated in the linear inverse scattering context and solved by using the Singular Values Decomposition tool. A ray-based model accounting for the electromagnetic signal propagation into an inhomogeneous medium is developed to accurately evaluate the kernel of the integral equation to be inverted. Under the proposed model, an analysis of the spatial resolution performance is carried out as a function of the geometrical and electromagnetic parameters of the scenario. To this end, theoretical concepts based on diffraction tomography and the Singular Value Decomposition of the scattering operator are exploited. Reconstruction results based on full-wave simulated data assess the feasibility of the imaging approach.

Pervasive Machine Learning for Smart Radio Environments Enabled by Reconfigurable Intelligent Surfaces

The emerging technology of reconfigurable intelligent surfaces (RISs) is provisioned as an enabler of smart wireless environments, offering a highly scalable, low-cost, hardware-efficient, and almost energy-neutral solution for dynamic control of the propagation of electromagnetic signals over the wireless medium, ultimately providing increased environmental intelligence for diverse operation objectives. One of the major challenges with the envisioned dense deployment of RISs in such reconfigurable radio environments is the efficient configuration of multiple metasurfaces with limited, or even the absence of, computing hardware. In this article, we consider multiuser and multi-RIS-empowered wireless systems and present a thorough survey of the online machine learning approaches for the orchestration of their various tunable components. Focusing on the sum-rate maximization as a representative design objective, we present a comprehensive problem formulation based on deep reinforcement learning (DRL). We detail the correspondences among the parameters of the wireless system and the DRL terminology, and devise generic algorithmic steps for the artificial neural network training and deployment while discussing their implementation details. Further practical considerations for multi-RIS-empowered wireless communications in the sixth-generation (6G) era are presented along with some key open research challenges. Different from the DRL-based status quo, we leverage the independence between the configuration of the system design parameters and the future states of the wireless environment, and present efficient multiarmed bandits approaches, whose resulting sum-rate performances are numerically shown to outperform random configurations, while being sufficiently close to the conventional deep <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> network (DQN) algorithm, but with lower implementation complexity.

Electromagnetic waves in lossy conductive media: cylindrical and spherical symmetry cases

It was recently demonstrated that surface electromagnetic waves can propagate inside stratified lossy conductive media. Here we consider electromagnetic waves in lossy conductive media in the cylindrical and spherical symmetry cases. We demonstrate that low loss electromagnetic waves may also propagate along cylindrical channels inside lossy media. Applications of these cylindrical waves may include active communication through plasma, search for underground cables, and propagation of electromagnetic signals along bones and nerves inside biological tissues. On the other hand, consideration of the spherical symmetry case indicates the possibility of deeply subwavelength ‘hot spots’ inside highly lossy biological tissues.

Результаты численного моделирования задачи видеоимпульсного георадиолокационного исследования в пресноводных водоемах

Ground-penetrating radar profiling on the surface of water bodies is applied in various geological and engineering studies. Here, we present the results of numerical simulation of the propagation of a video pulse electromagnetic signal in a freshwater body with gradients of the permittivity and electrical conductivity in the near-bottom layer. The method of numerical solutions of Maxwell's equations in the time domain is applied, in the general setting for rapidly changing processes, without restrictions on the magnitude of the change in the parameters of the medium. The results make it possible to explain the apparent decrease in water depth according to GPR data in comparison with the true depth and the appearance of additional reflecting boundaries on radargrams in the bottom layer.

Joint Inversion of Evaporation Duct Based on Radar Sea Clutter and Target Echo Using Deep Learning

Tropospheric duct is an anomalous atmospheric phenomenon over the sea surface that seriously affects the normal operation and performance evaluation of electromagnetic communication equipment at sea. Therefore, achieving precise sensing of tropospheric duct is of profound significance for the propagation of electromagnetic signals. The approach of inverting atmospheric refractivity from easily measurable radar sea clutter is also known as the refractivity from clutter (RFC) technique. However, inversion precision of the conventional RFC technique is low in the low-altitude evaporation duct environment. Due to the weak attenuation of the over-the-horizon target signal as it passes through the tropospheric duct, its strength is much stronger than that of sea clutter. Therefore, this study proposes a new method for the joint inversion of evaporation duct height (EDH) based on sea clutter and target echo by combining deep learning. By testing the inversion performance and noise immunity of the new joint inversion method, the experimental results show that the mean error RMSE and MAE of the new method proposed in this paper are reduced by 41.2% and 40.3%, respectively, compared with the conventional method in the EDH range from 0 to 40 m. In particular, the RMSE and MAE in the EDH range from 0 to 16.7 m are reduced by 54.2% and 56.4%, respectively, compared with the conventional method. It shows that the target signal is more sensitive to the lower evaporation duct, which obviously enhances the inversion precision of the lower evaporation duct and has effectively improved the weak practicality of the conventional RFC technique.

Magnetic Field and Electron Density Scaling Properties in the Equatorial Plasma Bubbles

The ionospheric plasma density irregularities are known to play a role in the propagation of electromagnetic signals and to be one of the most important sources of disturbance for the Global Navigation Satellite System, being responsible for degradation and, sometimes, interruptions of the signals received by the system. In the equatorial ionospheric F region, these plasma density irregularities, known as plasma bubbles, find the suitable conditions for their development during post-sunset hours. In recent years, important features of plasma bubbles such as their dependence on latitude, longitude, and solar and geomagnetic activities have been inferred indirectly using their magnetic signatures. Here, we study the scaling properties of both the electron density and the magnetic field inside the plasma bubbles using measurements on board the Swarm A satellite from 1 April 2014 to 31 January 2016. We show that the spectral features of plasma irregularities cannot be directly inferred from their magnetic signatures. A relation more complex than the linear one is necessary to properly describe the role played by the evolution of plasma bubbles with local time and by the development of turbulent phenomena.

Terahertz Window Frequency Signal Attenuation and Dispersion Characteristics in Tropical Climate Zone: An Experimentally Validated Reliability Analysis

The propagation of electromagnetic signals through atmosphere is affected by absorptive and dispersive processes present therein. The resulting attenuation increases in adverse weather conditions. The loss of signal power due to scattering of electromagnetic waves in free space, is one of the most common hazards in ultrafast wireless communication systems. The scattering of signal is caused by the suspended atmospheric hydrometeors. Moreover, due to the humidity of the atmosphere, the defocusing of the electromagnetic beam, known as scintillation, may occur. In this paper, the authors, for the first time, have presented a comprehensive analysis of terahertz (THz) signal attenuation along with scintillation effect, in fog-laden atmosphere of Indian subcontinent under tropical climatic belt. The frequency-dependent properties of the signal attenuation have been analysed using an indigenously developed Non Linear Terahertz Attenuation Model (NLTAM)simulator. Moreover, the difference between single and multiple scattering effects of THz signal has also been presented here. The nature of THz signal attenuation spectra in foggy atmosphere, agrees closely with experimental findings, for near THz or IR signal transmission in fog-based aerosols weather scenario in both tropical and non-tropical regions. The experimental study at MMW regime was carried out through radiometric measurement of fog attenuation at Kolkata (22 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sup> N, tropical region) and the results are compared with the NLTAM model data for reliability verification. The signal attenuation is found to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim \,\,16\times 10^{5}$ </tex-math></inline-formula> dB/Km around 2.0 THz frequency. By incorporating parametric variations in the present simulator, the authors have estimated the reliable range of THz signal energy, coming out of atmospheric fog-layer. The authors have developed a separate reliability model to address this aspect of study. To initiate a comparative analysis on the prediction of attenuation of THz wave for different types of scattering mechanisms, especially in foggy atmosphere, under tropical climatic region, a novel technique has been developed and reported by the authors for the first time.

Features of propagation and absorption of electromagnetic signals in periodic structures of conducting and dielectric layers

Different regimes of electromagnetic signal transmission through heterostructures formed by a sequence of conducting and non-conducting layers are discussed for various ratios between the frequency of radiation and the transport frequency of electron scattering in the conducting layers. Possibility to increase the efficiency of detecting or filtering electromagnetic radiation in a wide range of frequency range (from subTHz to far IR) in such structures is analyzed. Keywords: propagation of electromagnetic waves in heterostructures, resonant tunneling, THz-IR detectors, bolometers.

Research on Simulation and Test of Spatial Isolation Based on Geographic Information

In the process of site selection for the deployment of distributed systems, in order to solve the problem of inaccurate spatial isolation simulation results caused by the large influence of complex geographic information such as terrain and weather on the propagation of radio waves, and to solve the problem of inefficient and inefficient spatial isolation testing. This paper proposes to select suitable propagation models for different geographical information in different regions, clarifies the simulation calculation method, and proposes a test method to accurately determine the direction of the transceiver antenna for the minimum spatial isolation. By comparing and analyzing the simulation calculation results and test verification results, correction parameters such as simulation system error, atmospheric absorption loss, and geological absorption loss are proposed. This article analyzes and studies the correction value of radio wave transmission loss of S-band electromagnetic signal under different geographic information conditions such as snowfall and iron ore through an example. It can provide reference values for some of the influencing factors of electromagnetic signal propagation loss under geographic information conditions, and it can improve the accuracy of the simulation calculation results of the spatial isolation under the conditions of geographic information.

Tropospheric Delay in the Neapolitan and Vesuvius Areas (Italy) by Means of a Dense GPS Array: A Contribution for Weather Forecasting and Climate Monitoring

Studying the spatiotemporal distribution and motion of water vapour (WV), the most variable greenhouse gas in the troposphere, is pivotal, not only for meteorology and climatology, but for geodesy, too. In fact, WV variability degrades, in an unpredictable way, almost all geodetic observation based on the propagation of electromagnetic signal through the atmosphere. We use data collected on a dense GPS network, designed for the purposes of monitoring the active Neapolitan (Italy) volcanoes, to retrieve the tropospheric delay parameters and precipitable water vapour (PWV). This study has two main targets: (a) the analysis of long datasets (11 years) to extract trends of climatological meaning for the region; (b) studying the main features of the time evolution of the PWV during heavy raining events to gain knowledge on the preparatory stages of highly impacting thunderstorms. For the latter target, both differential and precise point positioning (PPP) techniques are used, and the results are compared and critically discussed. An increasing trend, amounting to about 2 mm/decades, has been recognized in the PWV time series, which is in agreement with the results achieved in previous studies for the Mediterranean area. A clear topographic effect is detected for the Vesuvius volcano sector of the network and a linear relationship between PWV and altitude is quantitatively assessed. This signature must be taken into account in any modelling for the atmospheric correction of geodetic and remote-sensing data (e.g., InSAR). Characteristic temporal evolutions were recognized in the PWV in the targeted thunderstorms (which occurred in 2019 and 2020), i.e., a sharp increase a few hours before the main rain event, followed by a rapid decrease when the thunderstorm vanished. Accounting for such a peculiar trend in the PWV could be useful for setting up possible early warning systems for those areas prone to flash flooding, thus potentially providing a tool for disaster risk reduction.