Vol 64, No 6 (2019)
- Year: 2019
- Articles: 11
- URL: https://journals.rcsi.science/1064-2269/issue/view/12513
Electrodynamics and Wave Propagation
Formation of Amplitude and Polarization Characteristics of Short Waves during Propagation in the Ionosphere
Abstract
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.
Regular and Irregular Planar Metamaterial Waveguides on Metal Substrates
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.
Tuning the Operating Band of an Artificial Magnetic Conductor
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.
Antenna and Feeder Systems
A Theoretical and Experimental Study of Frequency-Selective Structures for Reducing the Scattering Properties of a Phased Antenna Array
Abstract
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.
Statistical Radiophysics
Soft-Decision Algorithm in Radio Communication Systems with Frequency Hopping
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.
Theory and Methods of Signal Processing
Reconstruction of Images Distorted by Defocusing and Blurring without Determining the Type and Parameters of the Hardware Function
Abstract
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.
Radar Interferometric Survey of the Surface of an Unprepared Landing Area from on Board a Helicopter
Abstract
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.
Itakura–Saito Divergence as an Element of the Information Theory of Speech Perception
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.
Electron and Ion Optics
Exact Solutions for Dense Electron Beams with Translational Symmetry
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.
Radio Phenomena in Solids and Plasma
Multiplicative Frequency Conversion in a Scheme of Magnetostrictive Transducer. Frequency Multiplication in the Continuous Regime
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.
Novel Radio Systems and Elements
Principles of the Functioning of Nonreactive Double Memristor Oscillators
Abstract
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.