Том 62, № 11 (2017)
- Жылы: 2017
- Мақалалар: 16
- URL: https://journals.rcsi.science/1064-2269/issue/view/12426
Electrodynamics and Wave Propagation
Radiation from a two-dimensional array of coupled slot lines
Аннотация
The problem of radiation of the eigenmodes of an infinite 2D array of semi-infinite coupled slot lines is solved. An analytical solution for the electric field on conductors is found by the Wiener–Hopf method in the approximation of narrow conductors forming the slot lines. An algorithm of numerical implementation of this solution is developed. Expressions for elements of the scattering matrix of an infinite array are found. Dependences of the elements of the scattering matrix on frequency and the structure parameters are studied numerically.
Passively Q-switched spaser as a terahertz clock oscillator for plasmon computer
Аннотация
The interaction of plasmons in spaser with saturable absorber leads to pulse generation under passive Q-switching. A distributed scheme of spaser that represents a groove on metal surface filled with active medium is considered. The Maxwell–Bloch equations are used to describe generation of 1D plasmons in such a distributed spaser. The operation of the system as a terahertz clock oscillator is demonstrated with the aid of numerical experiment.
Calculation of the input impedance of a stripline dipole conformally situated on a dielectric cylinder
Аннотация
A method for calculation of the input impedance of a stripline dipole (SD) conformally situated on a dielectric cylinder is developed. A singular integral equation (SIE) for the unknown current density distribution function on the SD surface is obtained. A numerical method for solution of this SIE is described. The dependence of the input impedance on the SD length is obtained.
On excitation of the surface wave on the plane surface of an electrically conducting medium with high conductivity by a vertical aperture, the Zenneck wave
Аннотация
The efficiency of excitation of the surface wave, in particular, the Zenneck wave on the plane boundary of an electrically conducting medium with high conductivity by a vertical aperture is introduced and analyzed.
Antenna and Feeder Systems
Synthesis and analysis of constrained polyfocal lenses with symmetric focal curves
Аннотация
The problems of synthesis of bifocal, trifocal, and quadrifocal constrained lenses with symmetric focal curves are solved. The solution of the problem for the shape of the lens surface in the first case is obtained in the explicit analytical form and, in the other cases, in a parametric analytical form. Based on the numerical study of the eikonal, parameters of the lenses are optimized and the analysis of the eikonal aberrations of the optimized lenses is performed for two values of the maximum angle of view: 60° and 90°. The results of a numerical experiment for a planar constrained quadrifocal lens and a maximum angle of view of 60° are presented.
Analysis and optimization of an array of miltimode plane waveguides excited by TM waves in order to form sectorial partial directional patterns
Аннотация
An electrodynamic analysis of an infinite periodic array of radiating planar multimode waveguide sections of finite length, each of which is excited by TM waves through a pair of input planar waveguides, is carried out. A numerical algorithm based on the method of projective field matching at the boundaries of partial domains, making it possible to calculate the partial directional pattern of the array and the amplitudes of the reflected waves in the input waveguides, is developed. Three circuits for the excitation of the array are considered, and the optimization of the length of the radiating sections and the parameters of the excitation circuits in order to form sectorial partial directional patterns of the array is performed. Results characterizing the comparative efficiency of the considered circuits for different periods of array are presented.
Statistical Radiophysics
Noise of electrode sensor in pulsating liquid flow
Аннотация
A periodic component of the ac electrode voltage (electrode noise) is revealed in experiments. The frequency of the periodic component is equal to the pulsation frequency of the flow velocity of liquid in which the electrode sensor is immersed. For the electrode sensor that moves in liquid such a component of the electrode noise may prevail and determine the sensitivity. The sensitivity of a sensor with stainless-steel electrodes with respect to the velocity pulsations is determined to be 1.2 × 10−6 V s/m. Pulsations of the electrode potential can be interpreted using variations in the rate of electrochemical reaction on the electrode surface.
Theory and Methods of Signal Processing
Potential efficiency of data transmission systems in channels with non-Gaussian quasi-pulsed interferences
Аннотация
The potential efficiency of data transmission systems in channels with quasi-pulsed radio interferences of the natural and industrial type has been estimated. The lognormal model of pulsed interference components has been used.
Low-complexity SIC-MMSE for joint multiple-input multiple-output detection
Аннотация
Iterative detection and decoding based on a soft interference cancellation–minimum mean squared error (SIC-MMSE) scheme provides efficient performance for coded MIMO systems. The critical computational burden for a SIC-MMSE detector in a MIMO system lies in the multiple inverse operations of the complex matrix. In this paper, we present a new method to reduce the complexity of the SIC-MMSE scheme based on a MIMO detection scheme that uses a single universal matrix with a non-layer-dependent inversion process. We apply the Taylor series expansion approach and derive a simple non-layer-dependent inverse matrix. The simulation results reveal that the utilization of the universal matrices presented in this paper produces almost the same performance as the conventional SIC-MMSE scheme but with low computational complexity.
Whispered speech recognition based on gammatone filterbank cepstral coefficients
Аннотация
This paper presents the results on whispered speech recognition using gammatone filterbank cepstral coefficients for speaker dependent mode. The isolated words used for this experiment are taken from the Whi-Spe database. Whispered speech recognition is based on dynamic time warping and hidden Markov models methods. The experiments are focused on the following modes: normal speech, whispered speech and their combinations (normal/whispered and whispered/normal). The results demonstrated an important improvement in recognition after application of cepstral mean subtraction, especially in mixed train/test scenarios.
Dynamics Chaos in Radiophysics and Electronics
Analysis of chaotic synchronization of cascade coupled systems for phase-locked loop using wavelet analysis
Аннотация
A method for detection and study of chaotic synchronization of cascade coupled single ring continuous phase-locked-loop systems is based on the determination of the phase of chaotic signal using continuous wavelet transform and the subsequent monitoring of phases on time (frequency) scales. Morlet, Gauss, Shannon, and B-spline complex wavelets are studied. The results of mathematical simulation are presented. Signal-to-noise ratios that allow chaotic phase synchronization are estimated.
Electron and Ion Optics
Formation of a ribbon electron beam of a planar gyrotron in the end region and near the edge of the cathode
Аннотация
The problem of formation of a ribbon beam with the cross section shaped as an elongated parallelogram, which is typical of electron-optical systems of planar gyrotrons due to the drift velocity along the cyclic coordinate, is solved. A local solution of the Laplace equation in the case of the temperature-limited emission near the cathode edge is constructed in the general case of 2D flows with nonuniform beam parameters. In contrast to arbitrary setting of the electrode geometry in this region, this solution does not violate the adopted hydrodynamic model of the flow. The results corresponding to typical parameters of a planar gyrotron are presented.
Configuration of the thermal gap in magnetron-injection guns complying with the hydrodynamic flow model
Аннотация
An exact solution of the exterior problem for a planar magnetron is constructed in the case of emission limited by the temperature and the space charge. The configuration of the lateral cathode surface and the electrode with a negative potential, which form a profiled thermal gap, is calculated. In contrast to an arbitrary geometry of the electrode in this region, this configuration does not violate the adopted hydrodynamic flow model. The case of a planar diode with the T-mode emission is also studied.
Synthesis of systems formation of converging sheet electron beams at partial magnetic shielding of the cathode
Аннотация
The synthesis method of electro-optical systems forming converging sheet electron beams at partial magnetic shielding of the cathode is developed. Equations of the inerior and exterior problems of the synthesis method and an equation for estimation of the deformation of the configuration of the sheet electron beam in the transit channel are obtained in the paraxial approximation. The proposed method is used to simulate electron guns forming converging sheet electron beams with the electrical parameters similar to the parameters of the uncompressed electron beam for terahertz radiation sources.
Novel Radio Systems and Elements
Analytical approximation of the generalized ambiguity function of the MIMO synthetic-aperture radar system
Аннотация
The generalized ambiguity function in spatial coordinates and its approximate analytical representation are obtained for the multifrequency multiple-input multiple-output (MIMO) synthetic-aperture radar (SAR) system. The examples in which ambiguity-function cross sections in range and azimuth are calculated in the Earth remote sensing problem for the MIMO SAR system installed on a spacecraft and compared with those for the classical SAR system are presented. In the case of the MIMO SAR system, the physical meaning and the practical importance of an increase in azimuthal resolution are explained.
High-symmetry DC SQUID based on the Nb/AlOx/Nb Josephson junctions for nondestructive evaluation
Аннотация
Topology of high-symmetry thin-film SQUIDs based on the Nb/AlOx/Nb tunneling junctions is developed and optimized. The devices exhibit relatively low sensitivity to static external field and electric interference. An experimentally implemented SQUID sensor with an integrated input coil with a sensitivity of 0.26 μA/Ф0 exhibits an intrinsic noise with respect to magnetic flux of less than \(5\mu {\Phi _0}/\sqrt {Hz} \). A system for encapsulation of sensors is developed for applications in multichannel systems for nondestructive evaluation of materials and alternative diagnostic systems.