Radio physics and electronics

3-8

Authors: N.N. Beletskii, S.A. Borysenko

Subject and Purpose. The effect of total electromagnetic wave tunneling through a three-layer structure containing a plasma-like negative-permittivity layer is important for both gaining a better insight into the high-frequency properties of layered solids and, hence, creating new types of high-frequency radio-physical devices. The main purpose is to study the influence the frequency dispersion of the negative-permittivity layer exerts on the electromagnetic wave tunneling through a three-layer structure with an asymmetric dielectric medium. Methods and Methodology. A new universal approach is used, based on introducing dimensionless frequencies and dimensionless layer thicknesses of a three-layer structure. It allows the frequency-dependent conditions of the effect of total electromagnetic wave tunneling to be examined for different frequency ranges and various three-layer structure parameters. Results. It has been shown that taking into account the frequency dispersion of the negative-permittivity layer makes it possible to observe the total tunneling of electromagnetic waves at different frequencies with an appropriate choice of the three-layer structure parameters. In various frequency ranges, the effect of two-frequency total tunneling of electromagnetic waves has been predicted. Conclusion. In the presence of a frequency dispersion of a negative-permittivity layer as part of a three-layer structure, the total electromagnetic wave tunneling conditions of this structure are softened and modified significantly. In this case, unique phenomena arise that can be used to create fundamentally new high-frequency devices in optics, radiophysics, and electronics.

22-28

Authors: V.A. Kabanov

Subject and Purpose. One of the relevant areas of remote sensing of the environment is the development of microwave methods of passive sensing of the atmosphere. The biggest challenge occurring in radiometric measurements is measuring system calibration. The reason lies in the lack of external calibration elements whose brightness temperatures are known with a high accuracy. The paper deals with the method for determining the sky brightness temperature by relative measurements at different elevation angles. The brightness temperatures refined in the way fit for radiometric system calibration. Methods and Methodology. Basically, the approach is governed by the dependence of the atmospheric brightness temperature on the elevation angle in terms of the plane-layered isothermal atmospheric model. The measurements rely on a three-centimeter radiometric system having a horn-reflector antenna combined with the MPL-1 weather radar, the entire range of elevation angles being accessible. Besides, a combined setup of two, 10 GHz and 36 GHz, radiometers is involved for measurements from a building window. Results. The previously proposed methodology for radiometric system calibration against the sky temperature obtained by relative measurements at different elevation angles has been analyzed and tested. The calibration possibility has been examined in the case that zenith measurements are unavailable. Conclusion. The proposed method for getting sky temperatures upon relative measurements at different elevation angles significantly increases accuracy of radiometric system calibration and extends a range of weather conditions admitting calibration of the kind. It has been shown that the radiometric system calibration against the sky temperature is possible even with zenith measurements excluded.

38-45

Authors: T.V. Kalmykova, S.I. Tarapov, A.S. Vakula, S.V. Gorobets, O.Yu. Gorobets, Yu.I. Gorobets, M.A. Bulaevskaya, K.A. Getmanenko

Subject and Purpose. Synthesis of biological sorbents has become one of the ways to solve the problem of environment contamination with heavy metals. Today, studying properties of biosorbents with injection of magnetic nanoparticles is important. Thus, injection of magnetic nanoparticles of magnetite (Fe3O4) improves absorption properties of biosorbents. The subject of the present work is magnetic resonance properties of nanoparticles inside biosorbents, such as macromycetes like Pleurotus ostreatus. The purpose is to examine these magnetic resonance properties and analyze the state of magnetite nanoparticles inside Pleurotus ostreatus. Methods and Methodology. The X-band Electron Spin Resonance (ESR) method is employed to register ferromagnetic resonance (FMR) spectra at T = 294 K. TEM-images of magnetic nanoparticles are made in the transmission electron microscope. Mathematical modeling for the properties of the arising clusters of magnetic Fe3O4 nanoparticles inside macromycetes Pleurotus ostreatus is performed using a phenomenological model upon the well-known Kittel equation. A model enhancement is proposed in the case of interacting nanoparticles inside an ellipsoidal magnetic cluster. Results. It has been shown that Fe3O4 nanoparticles are well absorbed by macromycetes and gather into structural clusters regardless of the concentration of magnetic nanoparticles injected. These magnetic clusters of magnetic nanoparticles have ellipsoidal shapes with an aspect ratio of 3:1:1. The developed mathematical model makes it possible to obtain dimensions of magnetic clusters from the FMR spectra and evaluate their shape and mutual magnetic interaction. The mathematical modeling results are in good agreement with TEM-images of these clusters inside Pleurotus ostreatus. As a result of modeling are in good agreement with the TEM-images of these clusters inside Pleurotus ostreatus. Conclusion. The presented results will contribute to the development of non-destructive testing of the state of biological sorbents using magnetic resonance radio spectroscopy methods.

54-63

Authors: A.V. Degtyarev, M.M. Dubinin, V.A. Maslov, V.S. Senyuta

Subject and Purpose. In this paper, spatial power characteristics of laser beams with inhomogeneous spatial polarization are theoretically investigated depending on whether they have moderate or sharp focusing. The spotlight of the numerical simulation of laser beam focusing in the terahertz range is on the laser waveguide dielectric resonator modes coincident with waveguide eigenmodes. Symmetric and asymmetric modes with both spatially inhomogeneous azimuthal and radial polarizations and homogeneous linear polarization of the field are considered. Methods and Methodology. The study of the electric field components of laser radiation beams in their free space propagation employs Rayleigh-Sommerfeld integrals in nonparaxial approximation. The focusing lens action on the laser radiation is considered using the amplitude-phase correction function. The total intensity distributions of the resonator modes and their particular field components in the lens focal area are examined. Results. Wave beams with inhomogeneous spatial polarization of radiation are needed for meeting important fundamental and applied problems concerning terahertz electromagnetic wave interaction with matter and including diagnostics of material surface, thin films and biological objects, design and development of terahertz systems of information transmission and processing, terahertz communication systems, achievement of subwave resolution in terahertz tomography, etc. The literature on pulsed radiation beam focusing in the terahertz region is available, which cannot be said about continuous radiation beam focusing, data on the subject being practically absent. In the present work, physical features of moderate and sharp focusing of laser beams have been theoretically studied in the case of their excitation by modes of the resonator with a circular dielectric waveguide with different spatial polarizations of the field. The obtained results give a more in-depth view of the focusing features of terahertz laser beams. Conclusions. Physical features have been established for spatial power characteristics of radiation beams with different spatial polarizations of the field in the case of the excitation by modes of the laser cavity upon a circular dielectric waveguide in the terahertz range and with the regimes of moderate and sharp beam focusing in the free space considered.

74-81

Authors: O.V. Holovan, V.M. Kharchenko

Subject and Purpose. The paper presents a technology of constructing a promising meteor-burst communication system (MBCS) with code division multiplexing. It increases the bandwidth and improves the noise immunity and covert operation of the system. Methods and Methodology. The proposed technology is based on software-defined radio (SDR) and provides MBCS adaptation to the environment conditions by means of software parameter control of the signals and their transfer protocols. It includes a technique of forming a large ensemble of signals with a direct sequence spread spectrum and improved auto- and cross-correlation properties, involves the optimal reception and matched digital filtering of large-base signals. In order to improve the noise immunity, the narrow-band interference rejection in the signal spectrum is proposed and is jointly software installed with the matched filtering. The detection and synchronization techniques effectively working in the non-Gaussian and non-stationary interference conditions gained consideration. Results. A method of forming a large ensemble of direct sequence spread spectrum signals with improved auto- and cross-correlation properties has been software implemented using a pseudorandom permutation of codeword elements of a maximum-length register code. Designed with the use of fast Fourier transforms, algorithms of digital matched filtering and interference rejection as applied to large-base signals have been implemented via field-programmable gate arrays (FPGA). A method of detection and synchronization of large-base signals has been proposed and software implemented on the FPGA basis. Conclusion. The proposed algorithms and their implementation methods make it possible to increase the bandwidth, improve noise immunity and enhance covert operation of the meteor-burst communication system with code division multiplexing.