Transmission Of Electromagnetic Radiation Research Articles

Estimation of ground-based atmospheric turbulence strength (C n2) by neural network architecture

Estimating the atmospheric turbulence strength (C n 2) becomes significant in the research field of electromagnetic radiation transmission through the atmosphere, particularly optical waves. As turbulence strength increases, the quality and strength of these optical waves may decrease and cause much trouble as they pass through the atmosphere. Throughout the years, C n 2 has been formulated by different research groups for various geographical locations and seasons using macro-meteorological variables empirically and theoretically. However, since these models are based on the data collected from numerous places and conditions, such as deserts or coastal areas, they do not provide accurate C n 2 predictions for our experimental site, as demonstrated for three well-known models in the paper. In this study, a novel, to our knowledge, artificial neural network (ANN) model named as quadratic Fourier neural network (QFNN) is trained to estimate C n 2 from experimentally measured ground-based atmospheric turbulence strength and macro-meteorological variables during the winter season in a rural area. The trained model gives reliable estimations, achieving a value of R2=0.92 for experimental C n 2 values.

Plasma Response of a Metallic “Grating” Metasurface on a Substrate

The transmission of electromagnetic radiation through a silicon substrate with a square metallic grid deposited on one side has been studied experimentally. It has been established that the electrodynamic response of the structure is equivalent to the excitation of a transverse electromagnetic plasma mode in it with the plasma frequency determined by the geometric parameters of the grating, as well as by the thickness and relative permittivity of the substrate. A theoretical model has been developed to qualitatively describe the experimental results obtained.

PRODUCTION TECHNOLOGY OF RADIO-TRANSPARENT CERAMIC MATERIALS

Ceramic radiotransparent materials are non-metallic materials that ensure the transmission of electromagnetic radiation in the radio frequency range of 105–1012 Hz with minimal dielectric losses in the operating temperature range (tgδ 10-2–10-5, ε < 10) and a low value of the radio wave reflection coefficient (P < 1 %). Ceramic radiotransparent materials are used to create rocket and aircraft fairings that protect antenna systems from external factors. For the synthesis of radiotransparent ceramic materials, it is expedient and promising to use such crystalline phases as celsian (BaAl2Si2O8) and slawsonite (SrAl2Si2O8) due to their low dielectric constant and dielectric loss tangent, as well as rather high thermal stability and melting point compared to other aluminosilicate compounds (mullite, spodumene, cordierite, etc.). The development of technology for obtaining radio-transparent ceramic antenna fairings and elements of protective structures of antenna systems of aviation facilities based on the BaO (SrO) – Al2O3 – SiO2 system is relevant. For the formation of complex profile ceramic radiotransparent materials slurry casting in porous gypsum molds is used. In order to compare the developed ceramic compositions, the physico-mechanical, dielectric and electrodynamic properties were studied under normal conditions and in the millimeter frequency range (26-38 GHz). As a result of the research, the following have been developed: a technology for the production of ceramic radiotransparent materials based on slawsonite by semi-dry pressing method, based on celsian-slawsonite by slip casting method and based on celsian or slawsonite by slip casting method. It has been established that the developed materials meet the technical requirements for radio-transparent ceramic materials and can be used to produce elements of protective structures of antenna equipment, such as nose fairings for aircraft.

Heterogeneous radio absorbing composite materials based on powdered charcoals for electronic devices protection from the electromagnetic radiation impact

The results of theoretical and experimental substantiation of the technique developed by the authors for the manufacture of heterogeneous (two- or three-layer) radio absorbing composite materials based on powdered charcoals are presented. The technique is based on layer-by-layer pouring of mixtures of a gypsum binder and powdered charcoal (non-activated birch, activated birch, activated coconut) into molds in the order in which the outer (relative to the electromagnetic radiation propagation front) layer of the composite material is characterized by the lowest wave resistance, and the inner layer is characterized by the highest wave resistance. The specified order is determined by the results of the theoretical substantiation of the developed technique. In the course of its experimental substantiation, regularities for changing the electromagnetic radiation reflection and transmission coefficients values of the manufactured materials depending on the value of the radiation frequency in the range of 0.7–17.0 GHz have been established. Based on the established regularities, it was stated that the minimum value of the electromagnetic radiation reflection coefficient of the two-layer materials manufactured according to the developed and substantiated technique (thickness ~ 5.0 mm) is –12.0 ± 1.0 dB and corresponds to electromagnetic radiation frequencies of 0.8 and 2.6 GHz (it’s provided, when such materials are fixed on metal substrates). The minimum value of the electromagnetic radiation reflection coefficient of the three-layer materials (thickness ~ 10.0 mm) under the specified condition is also –12.0 ± 1.0 dB and corresponds to electromagnetic radiation frequencies of 4.5 and 6.0 GHz. The electromagnetic radiation transmission coefficient values of such materials decrease with an average step of 4.0 dB as the frequency of the radiation increases by 1.0 GHz in the range of 2.0–10.0 GHz and increase with a similar step as the frequency increases by 1.0 GHz in the range of 10.0–17.0 GHz. The minimum value is –30.0 ± 2.0 dB. The materials manufactured according to the developed and substantiated technique seem to be promising for ensuring the protection of electronic devices from the effects of electromagnetic interference (both active and passive types).

Перспективные слоистые гибкие радиопоглощающие материалы на основе порошкообразного угля

The article presents the technique for obtaining advanced layered radio-absorbing materials based on powdered charcoal. The technique includes the following technologies: incorporation of the electrolyte aqueous solution into the material particles pores; adhesive pressing. The developed technique is more manufacturable compared to the analogs. Materials obtained in accordance with this technique are characterized by the flexibility, as well as lower cost compared to other carbon-containing radio-absorbing materials. The experimental characteristics of electromagnetic radiation reflection and transmission coefficients in the frequency range 2.0 – 17.0 GHz of the materials obtained in accordance with the developed technique are described. The results of the comparative analysis of these characteristics are provided. Based on these results, it’s determined that the average values of electromagnetic radiation reflection coefficient in the specified frequency range of the materials based on powdered non-activated wood charcoal, powdered activated wood charcoal and powdered activated coconut charcoal are –4.5 dB, –8,5 dB and –9.0 dB (when these materials fixed on metal reflectors). The average values of their electromagnetic radiation transmission coefficient are –11.5 dB, –20.0 dB and –15.5 dB respectively. The investigated materials seem to be promising for use in order to protect electronic equipment from external electromagnetic interference.

Improved technology of frequency-selective UHF electromagnetic shields containing helical elements

An improved technology of frequency-selective electromagnetic shields has been considered. The technology has been improved by embedding classic Archimedean helical elements made from foiled materials into the bulk of the shields for the improvement of the frequency-selective performance of the shields and pinning of these elements in the bulk of the shields by means of fusion bonding. These design features provide for the main advantage of the improved technology in comparison with counterparts, i.e., lower time consumption. The technology has been improved in the following two aspects: 1) identification of helical element parameters providing for the greatest energy loss of the UHF electromagnetic radiation interacting with the helical elements; 2) identification of the optimum helical element arrangement in the shield bulk providing for the smallest transmission and reflection coefficient of the UHF electromagnetic radiation by the shields. Technology improvement in accordance with the former of the above aspects has been achieved based on analysis of publications dealing with mathematical simulation and study of the parameters of UHF electromagnetic radiation transmission by planar helical antennas. Technology improvement in accordance with the latter aspect has been achieved based on experimental data. Test shields have been fabricated with specifically arranged embedded helical elements, and comparison has been made between the UHF electromagnetic radiation transmission and reflection coefficients of the shields. Shields fabricated in accordance with the improved technology suggested herein show good promise for the electromagnetic noise protection of electronic devices.

Measuring setup for determining the parameters of materials that absorb radio waves

A measuring complex for determining the coefficients of reflection and transmission of electromagnetic radiation through radio-absorbing materials has been developed and manufactured. Measurements are made by the direct method by comparison with a reference material. When measuring the transmission of radio waves through an absorbing material, the standard is air, and when measuring the reflection of radio waves, a sheet of steel is used as the standard. When measuring the transmission of radio waves through an absorbing material, the standard is air, and when measuring the reflection of radio waves, a sheet of steel is used as the standard. The installation uses replaceable horn antennas and standard microwave generators. The distance necessary for carrying out measurements in the far field of antenna radiation was determined and the maximum sizes of the irradiation spots of the measured materials for various frequencies in the range from 1 to 20 GHz were calculated. A measurement setup that is efficient in terms of the “price-quality” criterion is made, easy to maintain and does not require computational work.

Методы и средства для измерения комплексных диэлектрической и магнитной проницаемостей материалов на СВЧ

This paper describes methods and tools for measuring the complex permittivity and permeability of various materials in the range of 0.9 – 40 GHz. A list of equipment necessary for the practical implementation of methods for experimental evaluation of the complex permittivity and permeability (ε, μ) of various materials, as well as the coefficients R of reflection and T of the transmission of electromagnetic radiation through samples of materials, is proposed. In the measuring circuits, the vector network analyzer PNA-X N5244 is used. Six schemes are given for connecting standard horn antennas to a network analyzer. Three methods for measuring the complex permittivity and permeability by the values of the reflection coefficient and one method for the values of the reflection coefficient and the transmission coefficient are considered: waveguide method for measuring ε and μ by the values of the reflection coefficient; methodology for measuring ε and μ by the values of the reflection coefficient in free space; resonator technique for measuring ε and μ; a technique for measuring ε and μ by the values of the reflection and transmission coefficient in free space. A comparative analysis of the measurement results of images obtained at the installation equipped with a vector analyzer of circuits of Agilent PNA-X N5244A and a complex based on panoramic VSWR meters in the range of 8 – 38 GHz is carried out. The measurements carried out made it possible to test the proposed methods.

Inertia Sensor Detecting Materials using Electromagnetic Signals

There are many commercial sensors that use inertia systems and others that use electromagnetic systems. Until now, none of the existing sensors combines a circular inertia movement with the simultaneous transmission of electromagnetic radiation in the band of very low (VLF) and ultra low (ULF) frequencies. The aim of this paper is to show the design of such a sensor, that contains an electromagnetic signal generator and to observe and monitor its movement on a free rotating inclined platform. An accurate positioning and monitoring system is used in order to measure the velocity and acceleration at every position on its movement. It is a novel system that is already in use in material identification and localization. It is indubitably working and exports excellent results, although we are not still familiar with the laws of physics that determine the specific phenomenon. Until this point the sensor is used to identify only a limited number of materials. In the future it would be ideal to use it for more materials, find their frequencies and create a library that contains many materials and different kind of substances.

Design and Construction of Axial Mode Mono-Filar Helical Antenna for Hydrogen Line Emission Studies with 4NEC2 Tool

Antennas have come to play a significant role in the reception and transmission of electromagnetic radiation or signals which in turn have improved scientific research in the various areas where they have been used. Astronomy is not left out; as a study of everything beyond earth’s atmosphere, useful signals have to travel great distances to reach us. Hence the need for equipment to detect such signals. The Helical Antenna is known to possess high gain (directivity) and can process signals with any type of orientation/polarization which implies high sensitivity hence the desire to use it. Simulation was done using the legacy 4NEC2 software. The purpose of this paper is to design a circularly polarized helical antenna operating in axial mode that is suitable for detection of neutral hydrogen line emission at the frequency of 1420 MHz and to show how it can be used as a feed for an off-set parabolic dish.

Accumulation of spatial charge on the surface of protecting coatings used against the penetration of high frequency electromagnetic fields

The article deals with the transmission of electromagnetic radiation through a selected building element. Measurements were made to determine the shielding effectiveness of the electromagnetic field. In order to increase the shielding effectiveness, shielding coatings were applied to the selected building element, some of which were concentrated with a laboratory-generated powder to improve the shielding effectiveness of the electromagnetic field. It has been found that a spatial charge occurs when an electromagnetic field impinging on the surface of shielding coatings. The size and polarity of the surface charge depends on the type of shielding coating, the frequency and duration of the electromagnetic field. Measurements were performed for the frequency range from 0.9 to 7 GHz.

Single-Layer Dichroic Filters for Multifrequency Receivers at THz Frequencies

In this work, we report the design, construction, and characterization of two free-standing single-layer frequency-selective surface structures to be used as dichroic filters in the THz range. Their spectral responses are aimed to fulfill a stringent band-pass performance in the atmospheric window between $600\; \text{and } 725$ GHz. Specifically, the dichroics have been required to allow a transmission of electromagnetic radiation of at least 90%, achieve a rejection in the stop-band lower than $-25$ dB, and have cross-polarization levels below $-30$ dB. All these specifications were demanded to be satisfied at normal and nonnormal beam incidence. We have studied dichroic filters with hexagonal patterns of two different apertures, a well-known single-hole geometry and, in order to enhance the spectral performance, a novel aperture geometry that we call the flower type. Their transmission characteristics were measured using a Fourier transform spectrometer. The electromagnetic simulations and experimental results not only show a good agreement but they demonstrate that the flower-type geometry can greatly outperform its single-hole counterpart achieving all the desired requirements. In this way, we demonstrate the feasibility of implementing single-layer systems at (sub)-THz frequencies suitable for low-noise astronomical applications.

ELECTROMAGNETIC AND SOUND INSULATION PROPERTIES OF COMBINED SHIELDS BASED ON THE NEEDLE-PUNCHING MATERIAL AND FRAGMENTS OF ALUMINUM FOIL

A method for creating the electromagnetic radiation shields, which consists in fixing fragments of aluminum foil on the surface of a needle-punched carbon-containing material has been proposed. In accordance to the proposed method the shield samples have been made. The fragments of the used aluminium foil were in the form of rectangles or half rings the overall dimensions of which didn't exceed 20 mm. Using an automated meter of transmission and reflection coefficients SNA 0.01–18, shielding characteristics in the frequency range 0.7–17 GHz of the shield samples made in accordance with the proposed method have been obtained. Using the measuring stand, the main components of which were a white noise generator, power amplifier, speaker, sound analyzer MANOM-2, in the frequency range 20–16000 Hz, the soundproofing properties of the shield samples made in accordance with the proposed method have been obtained. It was shown that the values of the electromagnetic radiation reflection coefficients in the frequency range of 0.7–17 GHz of the investigated shields vary from –0.5 to –19.0 dB, and the electromagnetic radiation transmission coefficient in the specified frequency range vary from –2.0 up to –18.0 dB. It was found that the of electromagnetic radiation reflection coefficient values in the frequency range 0.7–17 GHz and the electromagnet radiation transmission coefficient values in the frequency range 6–17 GHz of the shields made in accordance with the proposed method using fragments of aluminum foil in the form of half rings, by 1,0–6.0 dB below the same values of the shields made using fragments of aluminum foil in the form of rectangles. It was determined that the studied shields provide sound attenuation by 2–3 dB in the frequency range from 20–16000 Hz. In view of the obtained results, shields manufactured in accordance with the proposed method are recommended for use in order to protect information circulating in the premises from leakage through the acoustic channel and the channel of secondary electromagnetic radiation.

Research on Quantitative Remote Sensing Monitoring Algorithm of Air Pollution Based on Artificial Intelligence

When the current algorithm is used for quantitative remote sensing monitoring of air pollution, it takes a long time to monitor the air pollution data, and the obtained range coefficient is small. The error between the monitoring result and the actual result is large, and the monitoring efficiency is low, the monitoring range is small, and the monitoring accuracy rate is low. An artificial intelligence-based quantitative monitoring algorithm for air pollution is proposed. The basic theory of atmospheric radiation transmission is analyzed by atmospheric radiation transfer equation, Beer–Bouguer–Lambert law, parallel plane atmospheric radiation theory, atmospheric radiation transmission model, and electromagnetic radiation transmission model. Quantitative remote sensing monitoring of air pollution provides relevant information. The simultaneous equations are constructed on the basis of multiband satellite remote sensing data through pixel information, and the aerosol turbidity of the atmosphere is calculated by the equation decomposition of the pixel information. The quantitative remote sensing monitoring of air pollution is realized according to the calculated aerosol turbidity. The experimental results show that the proposed algorithm has high monitoring efficiency, wide monitoring range, and high monitoring accuracy.

The pseudo-limit problem existing in electromagnetic radiation transmission and its mathematical physics principle analysis

Abstract In the study of electromagnetic radiation transmission for large airflow layers, it is found that not all electromagnetic waves are capable of forming waveguide propagation, and have a limit value problem. This is because whether electromagnetic waves propagating in the atmosphere can be captured by the atmospheric waveguide generated under specific meteorological conditions into the waveguide layer, depending on the wavelength (frequency) of the electromagnetic wave, the relative position of the emission source and the evaporating waveguide. And parameters such as the emission angle of the source. When the angle of incidence of the sun and the angle of observation are at a horizontal level, the amplitude of the electromagnetic radiation reflection is not unique. From a mathematical point of view, the limit value is not unique or the limit value is discontinuous, which is called the pseudo limit problem. This electromagnetic transmission pseudo-limit problem is a mathematical physics principle that ignores the physical principles implied in electromagnetic radiation. Based on this background, the paper studies the influencing factors of the pseudo-limit problem of electromagnetic transmission in large airflow layer, and analyzes the mathematical physics principle in the pseudo-limit problem by using Snell’s optical law.

ELECTROMAGNETIC RADIATION REFLECTION AND TRANSMISSION CHARACTERISTICS OF TWO-LAYER STRUCTURES BASED ON TRANSITION METAL OXIDES

The aim of the work, the results of which are presented in the framework of the article, was to study the of electromagnetic radiation interaction laws in the frequency range 0.7…17 GHz with two-layer structures, the surface layer of which was made using powdered titanium dioxide, and the inner layer was made using a powder material based on oxide ferric iron. The thickness of the layers of the studied structures varied from 0.3 to 1 cm. To achieve this goal, theobjectives associated with the development of a methodology for the manufacture of multilayer structures based on composite materials containing transition metal oxides, as well as with the measurement of such structures samples electromagnetic radiation reflection and transmission coefficients in the frequency range 0.7...17 GHz. These measurements were carried out using a panoramic meter of reflection and transmission coefficients SNA 0.01–17. Based on the obtained measurement results, it was shown that in the frequency range 0.7…2 GHz, the lowest values of electromagnetic radiation reflection coefficient, reaching –20 dB, are characterized by structures whose surface layer thickness is 1 cm, and in the range 2 ... 17 GHz – structures, thickness the surface layer of which is 0.5 or 1 cm (depending on the thickness of the inner layer). The values of electromagnetic radiation transmission coefficient in the frequency range of 0.7...17 GHz of such structures reach –23 dB. Based on the results of the study, it is proposed to use the considered structures in the process of creating shielded rooms or improving the latter (for example, in cases, when it's necessary to reduce the level of passive interference in rooms shielded with metal materials).

Reflection and transmission of light by a half-space with a nonlocal response: A complex variable approach

A solution of the electromagnetic reflection and transmission problem by a half-space of a simple material with a nonlocal response to external electric fields is investigated with the aid of several mathematical results of the complex variable theory, the Sokhotski relations, and the Hilbert transform. We found that the problem of reflection and transmission of electromagnetic radiation in the Fourier space is equivalent to an integral equation arising in the Riemann boundary problem. The classical results of Fresnel’s formulas for S polarization are recovered, and the special case of the reflection and transmission of light by a half-space of small spheres in the diluted regime of particle concentration is found to also follow Fresnel’s formula with effective optical properties.

Development of Poly (vinylidene fluoride) and Polyaniline blend with high dielectric permittivity, excellent electromagnetic shielding effectiveness and Ultra low optical energy band gap: Effect of ionic liquid and temperature

Electrically conductive polymer blends have attracted profound attention as dielectric materials. However, achieving isotropic behavior, electrical stability and low current leakage is still challenging. Here we have synthesized a conductive polymer blend of Polyaniline (PANI) and Poly (vinylidene fluoride) (PVDF) exhibiting relatively high dielectric permittivity (εʹ) together with low band gap. Ionic liquid (IL) has been incorporated and the effect of IL in the dielectric properties are explored. The interfacial adhesion, morphology and the dielectric polarization of the blends are investigated. The electromagnetic shielding effectiveness (EMISE) of the conductive blends is studied in X-band frequency range. The electrical stability and decrease in current loss of the blends has been analyzed through I–V characteristics. The findings reveal that with increase in PANI loading in the temperature range of 25–100 °C and IL incorporation results in excellent dielectric properties for charge storage applications. The high efficiency of absorption and low transmission of electromagnetic radiation by the conductive blends is the main reason for excellent EMISE possessed by the systems which can be used for shielding applications in electronics. The increase in electrical stability and decrease in current leakage ability appear in the form of narrow band gap.

The Effect of Coloring on the Transmission of Electromagnetic Radiation in Eyeglass Lenses

The paper presents the results of investigations on the transmission of electromagnetic radiation from the UV-Vis ranges of organic colored spectacle lenses. All investigated lenses had the same refractive index and one of them differed in the SPF (sun protection factor). The main criterion for the quality of colored eyeglass lenses is eye protection against harmful UV radiation, infrared radiation and excessive exposure to solar radiation. The lenses were measured using a Varian UV-Vis Cary model 300 spectrophotometer. These studies showed that the best protection against this radiation is the choice of coloring in a color other than blue, and that as the power of the colored lens increases, protection against harmful UV radiation decreases.

Electro-Optical Device with Tunable Transparency Using Colloidal Core/Shell Nanoparticles

Suspended particle devices (SPDs) adapted for controlling the transmission of electromagnetic radiation have become an area of considerable focus for smart window technology due to their desirable properties, such as instant and precise light control and cost-effectiveness. Here, we demonstrate a SPD with tunable transparency in the visible regime using colloidal assemblies of nanoparticles. The observed transparency using ZnS/SiO2 core/shell colloidal nanoparticles is dynamically tunable in response to an external electric field with increased transparency when applied voltage increases. The observed transparency change is attributed to structural ordering of nanoparticle assemblies and thereby modifies the photonic band structures, as confirmed by the finite-difference time-domain simulations of Maxwell’s equations. The transparency of the device can also be manipulated by changing the particle size and the device thickness. In addition to transparency, structural colorations and their dynamic tunabilit...