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Vol 70, No 7 (2025)
ELECTRODYNAMICS AND RADIO WAVE PROPAGATION
Radio absorbing material based on square resistive contours
Abstract
Based on solving the problem of diffraction of a normally incident electromagnetic wave onto a structure in the form of a lattice of square resistive circuits located in a dielectric layer, the frequency dependences of the effective dielectric permeability of the structure are obtained. It is shown that the effective relative magnetic permeability of the structure is close to unity. The possibility of varying the variance dependences over a wide range by changing the parameters of the structure is shown. The transformation of the character of the dielectric permeability dispersion from relaxation to resonance with increasing frequency is shown.
Radiotehnika i èlektronika. 2025;70(7):627-634
627-634
THEORY AND METHODS OF SIGNAL PROCESSING
Statistical model of directional fading for land-mobile satellite communication systems. Part 1
Abstract
This study investigates a directional fading model for narrowbeam receiving antennas, typical of user terminals in modern satellite communication systems. Through analytical simplification, we derive an approximate version of the original model, where the power spectral density of the fading process is approximated by a Gaussian function. This approximation enables a computationally efficient synthesis method for the target application scenario. To validate the synthesized process, we compare its level-crossing statistics with theoretical predictions from a generalized reference model. Additionally, we propose a heuristic expression for a key model parameter controlling the angular spread of fading components. This expression is formulated in terms of physical parameters defining the radiation pattern of parabolic antennas, which are widely used in satellite terminals.
Radiotehnika i èlektronika. 2025;70(7):635-643
635-643
Statistical model of directional fading for land-mobile satellite communication systems. Part 2
Abstract
This paper presents a refined model of the flat fading stochastic process in satellite communication channels caused by multipath propagation when using narrowbeam receiving antennas. The key improvement over prior model lies in a reparameterization that explicitly accounts for the main lobe of a typical antenna radiation pattern, following ITU-R recommendations. For the proposed model, we derive expressions for level-crossing rate and average fade duration. The simulation of DVB-S2X VL-SNR signal propagation over fading channel based on derived model was performed, which demonstrates negligible loss in error resilience under fading depths most frequently observed in practice.
Radiotehnika i èlektronika. 2025;70(7):644-650
644-650
РАДИОФИЗИЧЕСКИЕ ЯВЛЕНИЯ В ТВЕРДОМ ТЕЛЕ И ПЛАЗМЕ
To the theory of multi-wave Cherenkov interaction of a ribbon electron beam with a plane dielectric system
Abstract
The possibility of using a waveguide with a dielectric insert as an electrodynamic Cherenkov amplifier system for electromagnetic waves in the entire microwave range up to frequencies of 1013 rad/s is investigated. As the simplest analogue of an electrodynamic system with a simply connected crosssection, a flat waveguide partially filled with an isotropic dielectric is considered. The frequency dependences of the multimode amplification coefficients of electromagnetic waves for various electron beam geometries in the modes of singleparticle and collective forced Cherenkov effects are obtained. The strong dependence of the coefficients and amplification mechanisms on the distance between the boundaries of the electron beam and the dielectric is investigated.
Radiotehnika i èlektronika. 2025;70(7):651-663
651-663
ЭЛЕКТРОНИКА СВЧ
Construction of peripheral area of fingers of power RF LDMOS transistor
Abstract
A review and study of the design options for the peripherals of RF LDMOS transistor fingers has been carried out. The study was carried out by means of 3D modeling in Sentaurus TCAD. As a result, the design variants allowing to provide the level of the drain-source breakdown voltage at the periphery not lower than in the working part of the finger were determined.
Radiotehnika i èlektronika. 2025;70(7):664-671
664-671
ПРИМЕНЕНИЕ РАДИОТЕХНИКИ И ЭЛЕКТРОНИКИ В БИОЛОГИИ И МЕДИЦИНЕ
Sliding Analysis of Remote Photoplethismography Signal Outliers Duration for Heart Rate Estimation
Abstract
A method for studying the heart rate variability is proposed based on the analysis of the dynamics of instantaneous periods of the pulse wave measured by remote photoplethysmography. Logically related stages of evaluation directly from measured data of quadrature components and outliers durations of biomedical signals above threshold levels are analyzed. Modern methods of intellectual analysis of nonstationary time series are used to obtain implementations of a family of adaptive estimates of periods and instantaneous frequencies of the fundamental heartbeat tone.
Radiotehnika i èlektronika. 2025;70(7):672-682
672-682
НАНОЭЛЕКТРОНИКА
Features of the cellular microstructures formation in iron-garnet films using focused ion beam etching
Abstract
The results of cellular microstructures formation in dielectric iron-garnet films are presented. We used local surface modification (etching) by focused ion beam lithography. It is shown that using a scanning electron microscope along with an ion column is effective to compensate for the surface charge while etching in iron garnets. This method does not require an additional sputtering of conductive layer onto the garnet film. The etching depth must be more than half of the initial film thickness for implementation of a monodomain state inside the cells, At the same time, the size of the initial domain structure in the film must be taken into account when choosing the lateral cell sizes.
Radiotehnika i èlektronika. 2025;70(7):683-688
683-688
Thin Film Formation During the Au Thermal Vacuum Evaporation at the (100) GaAs Substrate Surface
Abstract
The processes of formation of thin gold films on the surface substrate of gallium arsenide during evaporation in vacuum are investigated. The formation of gallium arsenide islands with a hexagonal lattice structure is detected. The influence of the conditions of manufacturing Au-GaAs contacts on the possibility of their use in microwave devices is discussed.
Radiotehnika i èlektronika. 2025;70(7):689-694
689-694
Magneto-optical properties of the BiIG/GGG/SiO2 heterostructure around the magnetic compensation point
Abstract
The results of Faraday effect and magnetic circular dichroism study in BiIG/GGG/SiO2 heterostructure are presented. The heterostructure consists of nanometer-thick layers of Bi3Fe5O12 (BiIG) iron garnet and Gd3Ga5O12 (GGG) paramagnetic garnet synthesized on SiO2 quartz substrate. It is shown that a magnetic compensation point arises in the BiIG layer due to ion diffusion at the BiIG/GGG interface. The specific features of diamagnetic transitions, caused by the presence of Fe3+ ions in different sublattices of the iron garnet and responsible for magneto-optical effects, are investigated around the magnetic compensation point. A sharp change in the energy of diamagnetic transitions is observed across the compensation point.
Radiotehnika i èlektronika. 2025;70(7):695-699
695-699
PHYSICAL PROCESSES IN ELECTRONIC DEVICES
700-706