Радиотехника и электроника

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Soft-Decision Algorithm in Radio Communication Systems with Frequency Hopping

Sat, 06/01/2019 - 00:00
Abstract

An expression for soft decisions is obtained for incoherent demodulation of signals with m-digit frequency-shift keying in radio communication systems with character frequency hopping in the presence of additional noise with unknown intensity in the frequency channels of the system. Results of simulation are presented.

Formation of Amplitude and Polarization Characteristics of Short Waves during Propagation in the Ionosphere

Sat, 06/01/2019 - 00:00

Abstract—The paper inverstigates variation in the parameters of the complex amplitude vector of narrowband signals along ray trajectories as applied to short waves in a three-dimensionally inhomogeneous anisotropic ionosphere plasma. Numerical experiments are conducted, as well as analysis of the polarization and amplitude characteristics of ordinary and extraordinary waves depending on the position of the source, the carrier frequency of the signal, the angular coordinates of the radiation and geophysical conditions.

Tuning the Operating Band of an Artificial Magnetic Conductor

Sat, 06/01/2019 - 00:00
Abstract

Approximate formulas for calculating the coefficient of reflection from an artificial magnetic conductor (AMC) based on a capacitive lattice (with additional capacitances installed between its elements to tune the AMC operating band) were derived. The results of numerical calculations validating the estimates using approximate formulas are presented. The engineering feasibility of a thin radio absorber with a tunable operating band based on this AMC and a resistive film was demonstrated theoretically and experimentally. The results of measurements performed in a waveguide with a cross section of 72 × 34 mm2 revealed that the center frequency of the operating band of the radio absorber shifted from 4.9 to 2.7 GHz as additional capacitances varied from 0 to 1.27 cm.

Multiplicative Frequency Conversion in a Scheme of Magnetostrictive Transducer. Frequency Multiplication in the Continuous Regime

Sat, 06/01/2019 - 00:00
Abstract

Oscillations of magnetization and elastic displacement in a ferrite plate that is normally magnetized with respect to the plate plane are studied in the continuous excitation regime. Frequency multiplication determined by the ratio of the resonance frequencies of the magnetic and elastic subsystems is analyzed. Time and amplitude characteristics of the low- and high-level excitation regimes are studied under conditions for reorientation of magnetization. Recommendations for experiments are proposed.

Itakura–Saito Divergence as an Element of the Information Theory of Speech Perception

Sat, 06/01/2019 - 00:00
Abstract

On the basis of the information theory of speech perception, a substantiation of the symmetric form of the Itakura–Saito divergence as the minimum decision-making statistics of the asymptotically optimal algorithm for recognition of speech signals at the basic, phonetic level of their processing is given. The conclusions of the theoretical study are confirmed by the results of an experiment. It is shown that the use of the synthesized algorithm can significantly improve the accuracy and reliability of the automatic recognition of the most problematic phonetic units.

Regular and Irregular Planar Metamaterial Waveguides on Metal Substrates

Sat, 06/01/2019 - 00:00
Abstract

The characteristics of lower type TM modes guided by a metamaterial planar waveguide located on a metal substrate are investigated. The influence of a finite metal conductivity on dispersion curves is studied. The influence of ohmic loss on the characteristics of wave scattering is considered using the example of the problem about the break of such a waveguide.

Radar Interferometric Survey of the Surface of an Unprepared Landing Area from on Board a Helicopter

Sat, 06/01/2019 - 00:00

Abstract—The paper considers the possibilities of radar interferometric survey of the surface of a landing site from on board a helicopter. It is shown that if the phase-difference dependence obtained in this way is superimposed on the radio-brightness pattern of the reflection according to resolution elements after irradiation of the studied surface under study, then it is possible to reconstruct a high-quality three-dimensional image of the landing area and to determine with high accuracy its possible slope, the characteristics of its relief, and the contours of foreign objects on it.

A Theoretical and Experimental Study of Frequency-Selective Structures for Reducing the Scattering Properties of a Phased Antenna Array

Sat, 06/01/2019 - 00:00

Abstract—A theoretical and experimental study of band-stop frequency-selective structures (FSSs) for reducing the scattering properties of linear antenna arrays outside of their operating band is presented. To perform the study, a two-layer FSS based on square loops located in different layers of the dielectric base has been selected. An electrodynamic simulation of the backscattering diagram (BSD) of a linear periodic structure shielded by the FSS has been carried out. An effect of nonsuppression of certain diffraction scattering lobes has been discovered and experimentally confirmed. The discovered effect has been physically explained and measures to eliminate it have been proposed. The results of the electrodynamic simulation of an antenna system consisting of an L-band phased antenna array (PhAA), a two-layer FSS located in front of the PhAA, and an absorbing material are presented.

Exact Solutions for Dense Electron Beams with Translational Symmetry

Sat, 06/01/2019 - 00:00
Abstract

Variants with generally spatial trajectories with one of the Cartesian coordinates that is cyclic for describing flows have been revealed among three-dimensional invariant solutions of the nonstationary nonrelativistic beam equations. The equations of plane solenoidal flows have been analyzed, whose solutions are not directly related to the group properties of the general beam equations.

Principles of the Functioning of Nonreactive Double Memristor Oscillators

Sat, 06/01/2019 - 00:00

Abstract—A new class of nonreactive memristor generators is considered. It is shown that the double memristor generator has wide functionality for controlling and modulating output signals. The various operation modes of such generators are studied, including those characteristic of artificial neurons nodes, such as excitation and inhibition, control of pulse trains, and change in the repetition rate in a packet.

Reconstruction of Images Distorted by Defocusing and Blurring without Determining the Type and Parameters of the Hardware Function

Sat, 06/01/2019 - 00:00

Abstract—A new approach to solving the problems reconstructing images distorted by defocusing and blurring is proposed. It is shown that for an alternating amplitude spectrum of the hardware function (HF), the renormalization method with constraint (RMC) with the classical universal reference spectrum (URS) does not lead to successful reconstruction. An algorithm is presented that automatically takes into account the sign of the HF spectrum due to the change in shape of the URS. This algorithm for the reconstruction of a distorted image yields results that weakly depend on the type and parameters of the HF.

Analysis of Scanning Characteristics in the H plane of Ultrabroadband Cylindrical Antenna Arrays of Biconical Elements

Wed, 05/01/2019 - 00:00
Abstract

Finite-element method is used to construct electrodynamic models of cylindrical phased antenna arrays using bicones and fragments of bicones. Numerical experiments are used to study scanning characteristics of cylindrical phased antenna arrays with different numbers of biconical elements. Phase relationships of the elements are optimized for minimization of side lobes. It is shown that the ultrabroadband regime of the cylindrical phased antenna arrays can be implemented using circular scanning in the Н plane.

Multiplicative Frequency Conversion in a Scheme of Magnetostrictive Transducer. Frequency Multiplication in the Relaxation Regime

Wed, 05/01/2019 - 00:00
Abstract

Stimulated oscillations of magnetization and elastic displacement in a normally magnetized ferrite plate with magnetoelastic properties are considered. Frequency multiplication at the ratio determined by the multiplicity of the resonance frequencies of the magnetic and elastic subsystems is analyzed. Time and amplitude characteristics of the effect are studied using a model of the impact excitation of the elastic system due to short-term effect of the magnetic system. Frequency division in the same scheme of the magnetostrictive transducer is employed for comparison.

On Simulation of Sheet Electron Beams with Regard to the Initial Transverse Thermal Velocities of Electrons

Wed, 05/01/2019 - 00:00
Abstract

A technique to take into account the initial transverse electron thermal velocities in converged sheet electron beams has been developed. This determines the main integral characteristics of a thermal beam in a gun and transportation region of the paraxial approximation via chosen characteristic electron trajectories. We have equations of characteristic electrons motion, initial conditions to solve equations, and formulas for the current density distribution in the thermal beam cross-section and current fraction in conventional boundary. The derived equations and formulas may be used in modeling electron-optical systems and choosing parameters in which the effect of heat electron motion on beam characteristics will lie within tolerable limits.

Dependence of Microcontroller Failure Parameters via Ultrashort Radio Pulses under Operation Conditions

Wed, 05/01/2019 - 00:00
Abstract

In this paper, we studied the functional failure of microcontroller (MC) ATmega8515 under ultrashort pulse series action at clocking frequencies of 1, 8, and 15 MHz. We analyzed the probabilities of occurrence in various types of failure and their connection with clocking frequency and magnitude of field strength. The correlation of MC failure with its operation phase is shown. The possibility to study, at least qualitatively, the behavior of complex electronic systems using well-known mathematical models was demonstrated.

Designing a Beam-Plasma Traveling Wave Tube

Wed, 05/01/2019 - 00:00
Abstract

The method of equivalent systems is used to simulate resonator slow-wave structures of beam-plasma devices. A collisionless plasma is considered as a filler for the drift channel. The adequacy of the model is shown by comparing the calculation results with known experimental data. The dispersion characteristics of slow-wave systems are analyzed. The structure of the high-frequency unit of a beam-plasma traveling wave tube is developed, and the parameters of the tube are evaluated using the VEGA code.

Synthesis of a Three-Channel Waveguide Microwave Multiplexer with a Modified Structure

Wed, 05/01/2019 - 00:00
Abstract

The synthesis procedure of a waveguide multiplexer with a modified structure is considered. Compared with standard methods, the approach to the synthesis of this structure is based on the principle of decomposition, to simplify and accelerate the development of complicated devices. To check the performance ability of a proposed structure, the three-channel X-band waveguide multiplexer with a modified design of channel filters was synthesized. Design and experimental results are compared.

Detection of Ordinary and Extraordinary Waves Using an Antenna Array with Controlled Polarization Characteristic

Wed, 05/01/2019 - 00:00
Abstract

Results on detection of waves with oppositely rotating electric vectors using a phased antenna array with controlled polarization characteristic that can be rotated in the plane of the incident wave are presented. Owing to the stroboscopic effect, the wave that is split upon ionospheric propagation into ordinary and extraordinary components can be detected at two frequencies: difference frequency that is equal to the rotation frequency of the polarization characteristic of the antenna and sum frequency depending on the type of the interacting component (ordinary or extraordinary).

Calculation of the Velocity of the Electromagnetic Field Propagation in a Medium with Inclusions

Wed, 05/01/2019 - 00:00
Abstract

Two variants of the method of calculation of the electromagnetic field propagation velocity in a medium with inclusions are investigated. The multiple scattering theory based on the electromagnetic wave diffraction by spherical particles in a Q-layered lattice and by Q-particles located inside a waveguide along its axis is considered.

The Natural Waves of a 1D Lattice of Rectangular Dielectric Rods

Wed, 05/01/2019 - 00:00
Abstract

The problem about the eigen waves of the infinite periodic lattice of rectangular dielectric rods located in a plane waveguide is considered. The boundary value problem is solved with the partial domain method, and the dispersion equation for the propagation constant of an eigen wave is obtained. The fields of eigen waves are found. The expression for the characteristic impedance of the fundamental wave is obtained. Results of the numerical investigation of the behavior of the moderating ratio and the characteristic impedance of the fundamental wave of the lattice are presented.

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