Vol 63, No 5 (2018)
- Year: 2018
- Articles: 14
- URL: https://journals.rcsi.science/1064-2269/issue/view/12460
Electrodynamics and Wave Propagation
On Slow and Fast Surface Waves Propagating on Plane Boundaries of Conducting Media with High Conductance. The Zenneck Wave
Abstract
The regularities of transition of phase and group velocities from slow surface waves (whose velocities are below the light speed) to fast surface waves (whose velocities are above the light speed) on the plane boundaries of highly conducting media are investigated when the parameters of media vary. It is shown that the structure of waves does not change qualitatively in the case of this transition: the waves remain to be surface ones in contrast to surface waves of dielectric waveguides. The latter ones are transformed into leaking waves or their structure changes in a more complicated way in the case of such transition. A result relating, in particular, to the Zenneck wave is obtained.
Plasmon Resonances in a Glass Nanowire Covered with a Silver Layer of Variable Thickness
Abstract
A two-dimensional problem of diffraction of a plane electromagnetic wave by a silver shell with the boundaries formed by a circular and an elliptical cylinders is considered. The far fields and the scattering spectra are calculated by rigorous methods in the visible band. The dipole and quadrupole resonance frequencies for thin shells are determined in the quasi-static approximation. It is shown that the quadrupole resonances are degenerate and the dipole resonances are “split”; at the dip frequency, the scattered field can be directed perpendicularly to the direction of propagation of the incident plane wave.
Distribution of the Strength of the Low-Frequency Field Demodulated in the Disturbed Lower Ionosphere over the Earth Surface
Abstract
The possible distribution of the field strength of the low-frequency demodulated radiation of the high-power transmitter of the HAARP station (Alaska, USA) over the Earth surface in the Earth–ionosphere waveguide has been numerically simulated. It has been shown that, owing to the extremely weak electromagnetic coupling between the ionosphere and the waveguide in the case of an ionospheric source, the strengths of the electric and magnetic fields of the waveguide waves are relatively low and are at the level of the low-frequency noise even in the immediate vicinity of the center of the distribution. It has been confirmed that, in order to detect such a signal and measure its parameters, it is necessary to use special procedures for processing data from ground-based receivers.
On Calculation of the Amplitude–Phase Distribution of the Field Radiated from an Open End of a Rectangular Dielectric Waveguide
Abstract
The problem of calculating the amplitude–phase distribution of the field radiated from an open end of a rectangular dielectric waveguide expanding along one of its sides (a plane dielectric horn) is considered. The problem of diffraction on the junction of a feed dielectric waveguide and the horn is solved by the domain decomposition method using a model in the form of a screened dielectric waveguide. The amplitude–phase distributions over the distance from the end of the radiator are studied. The possibility of using the screened model for solving the problem of radiation from the open end of a dielectric horn is shown.
Proper and Improper Complex Waves of a Circular Two-Layer Screened Waveguide with an Axial Longitudinally Magnetized Ferrite Layer
Abstract
In a two-layer circular screened waveguide with a longitudinally magnetized inner ferrite layer, the presence of different types of complex waves (CWs) both satisfying and not satisfying the energetic orthogonality condition is shown. The CWs are the solutions of a homogeneous boundary value problem, but, in the first case, the waves are energetically independent and, in the second case, they are associated with the source and indirectly coupled through it.
Calculation of the Input Impedance of a Strip Oscillator by the Singular Integral Equation Method
Abstract
A method is developed for calculation of the input impedance of a strip oscillator (SO) located in the free space. The singular integral equation with the Cauchy singularity is obtained for the unknown function of the current density distribution on the SO surface. Plots of the input impedance depending on the SO length are given.
Antenna and Feeder Systems
Cylindrical Plasma Antenna with Large Longitudinal Density Irregularity
Abstract
The efficiency of operation of a cylindrical plasma antenna as a function of the degree of longitudinal nonuniformity of the plasma density is examined. The study is based on the method of spectral field expansion into a complete set of functions comprising surface and pseudosurface waves of the plasma column. The system of integrodifferential equations for expansion coefficients determining radiation patterns and the amplitudes of transmitted, reflected, and scattered waves is solved in the case of rapid variation in the plasma density. Dependences of the coefficients of conversion of the surface-wave energy on the plasma-density gradient, the electric length of the section of plasma nonuniformity, and the electric radius of the plasma cylinder are calculated. It is demonstrated by examples that the portion of energy of the surface wave converted into radiation may exceed 50%. It has been found that the radiation patterns are narrow with a single lobe whose maximum is at an angle of several degrees to the direction of propagation of the surface wave. As the plasma-density gradient increases, the lobe width decreases and the lobe itself shifts toward 0°.
Extension of the Polarization Receiving Coefficient to the Case of Signals and Antennas with Time-Varying Polarizations
Abstract
An extension of the classical definition of the polarization receiving coefficient to the case of signals and antennas with time-varying polarizations is proposed. Analytic expressions for the polarization receiving coefficient taking into account possible time variations of polarizations of the received signal and the receiving antenna are obtained. Application of the derived expressions is illustrated by the example of calculation of the polarization receiving coefficient for signals with polarization modulation and polarization coding.
Statistical Radiophysics
Estimating the Instants of Appearance and Disappearance of an Optical Pulse with the Rectangular Intensity Profile of an Unknown Height
Abstract
The quasi-likelihood, maximum-likelihood, and quasi-optimal algorithms for estimating the instants of appearance and disappearance of an optical pulse with the rectangular intensity profile of an unknown height are synthesized and analyzed. The losses in estimation accuracy due to the a priori unknown intensity of the optical pulse are found.
Microwave Electronics
Single-Crystal NdBa2Cu3O7–x Films for Microwave Electronics
Abstract
The growth of single-crystal films of high-temperature superconductors of the NdBa2Cu3O7–x composition with a thickness of 1–1.5 μm on Al2O3 + CeO2 substrates during the laser spraying is investigated. Technological conditions of the epitaxial growth of the films with a temperature of superconducting transition of 95 K and a critical current of more than 106 A/cm2 at the temperature of liquid nitrogen are determined. It is shown that the structure of fabricated NdBa2Cu3O7–x films is more perfect and homogeneous than the structure of YBa2Cu3O7–x films widely used in microwave electronics.
Nanoelectronics
Fundamental Limitations on Miniaturization of Shape-Memory Micromechanical Devices. Thermoelastic Martensite Transformation on Micro-, Nano-, and Mesoscales
Abstract
TEM measurements are used to experimentally study thermoelastic martensite transformation in Ti2NiCu tapered plates. The martensite phase is observed at room temperature in the Ti2NiCu alloy when the plate thickness decreases to, at least, 80 nm, and the austenite phase is observed at smaller thicknesses. It is shown that the temperature of thermoelastic martensite transition in the Ti2NiCu alloy decreases with a decrease in the thickness of the plate, the transition is blocked at a thickness of less than 20 nm, and a hysteresis dependence is observed. Possible physical and technological reasons for blocking of the martensite phase transition on nanoscale and fundamental limitations on the sizes of micromechanical devices based on the shape-memory Ti2NiCu alloy are considered.
Electron and Ion Optics
A Relativistic Electron Beam with an Elliptical Cross Section in the Plane Magnetic Field
Abstract
The algorithm for calculating narrow relativistic electron beams with the straight axis and elliptical cross section in a plane external magnetic field is proposed. The comparison with the case of an axially symmetric magnetic field is made. The solution for the emission in the ρ mode is regularized.
Physical Processes in Electron Devices
Algorithm for Elimination of Structural Noise in an Image Intensifier with Pyroelectric Array
Abstract
Signal formation in image intensifier with pyroelectric array is considered. Application of panning regime is substantiated, and impossibility of image obturation is shown. A method for processing of thermal image is proposed to eliminate structural noise and allow operation in the absence of shutter. The method is optimized for pyroelectric arrays and practical applications are presented. Development of the method, in particular, with the aid of calibration of the signal of pyroelectric array is considered.
Memristive Properties of Structures Based on (Co41Fe39B20)x(LiNbO3)100–x Nanocomposites
Abstract
The current‒voltage characteristics of the metal/nanocomposite (NC)/metal structures based on (Co41Fe39B20)x(LiNbO3)100–x NCs 2.4 and 3 μm thick are investigated in the fields of up to ~104 V/cm. The structures are synthesized via ion-beam sputtering of a composite target, in which NCs of different composition are formed in the single cycle at x = 5‒48 at %. The memristive effect (ME) manifesting itself during resistive switching of structures and the storage of incipient states has been detected at x ≈ 10 at %. It is ascertained that the ME depends weakly on used metal (Cu or Cr) contacts and the NC layer thickness, the number of switching cycles (without degradation) exceeds 105, and the ratio between the resistances of high- and low-resistance states, i.e., the Roff/Ron ratio, reaches approximately 65. The detected ME is explained by the fact that oxygen vacancies substantially affect the tunneling conductance of metal-granule chains determining the electric resistance of structures below the percolation threshold.