Volume 61, Nº 4 (2016)
- Ano: 2016
- Artigos: 14
- URL: https://journals.rcsi.science/1064-2269/issue/view/12314
Electrodynamics and Wave Propagation
On the solution of waveguide boundary value problems in the absence of the Lorentz calibration
Resumo
The spectral method for the solution of boundary value electrodynamic problems without the use of the Lorentz calibration is proposed. The method involves autonomous decompositions of the electromagnetic field components, and the Galerkin procedure is applied directly to the Maxwell equations. The efficiency of the method is demonstrated for the example of a rectangular waveguide that is inhomogeneously filled.
Equivalent surface impedance of an infinite array of slot impedance loads designed on the basis of coupled rectangular domains
Resumo
A 2D design of an infinite array of slot impedance loads (SILs) is considered. Each SIL is designed from two coupled rectangular domains connected through apertures with both each other and free space. The integral equation method is used for determination of the equivalent surface impedance (ESI). Dependences of the ESI value are investigated for different geometric dimensions to wavelength ratios. It is shown that the SILs under study can be used to obtain a reactive component of ESI having either positive or negative sign for the thickness of the impedance structure not exceeding one-quarter the wavelength.
Bragg microwave structures based on waveguide-slot lines
Resumo
It is shown that a new type of the Bragg structure based on pieces of a waveguide-slot line can be created in the microwave band. The amplitude-frequency characteristics of such a structure are described theoretically and investigated experimentally in the frequency range 8–12 GHz. The regularities in the distribution of the electric field intensity in a standing wave appearing in the investigated Bragg structure are established. It is found that a resonance singularity appears in the forbidden zone of the investigated Bragg structure when a defect in the form of the changed length of the central section of a regular waveguide is made.
Antenna and Feeder Systems
On eikonal aberrations in axisymmetric double-reflector telescopic systems
Resumo
A formula describing the eikonal distribution on the surface of the main reflector of a doublereflector system of a general form is derived and its expansion in powers of the offset of the source from the focus up to the fourth-order terms is obtained. The analysis and minimization of aberrations for a doublereflector aplanatic Schwarzschild system are performed.
Two-level optimization of a polygonal TEM horn
Resumo
Two-level optimization of a modification of the TEM-horn based on description of the horn generatrix by a broken line is considered. The number of parameters of this horn is optimized on the basis of statistical methods of reduction of the space dimensionality. For each fixed number of parameters, optimization of the horn matching is applied.
Statistical Radiophysics
Identification of an emitting target with the aid of a single finder with allowance for possible final way points
Resumo
A method for regularized generalized identification is developed for a single stationary finder that works under conditions for significant a priori uncertainty. It is demonstrated that the method involves estimation of parameters in the polynomial model of target motion, coordinates of the final way point (selected from a set of possible points), and approach time for the given point. The applicability conditions are determined for the proposed method. A step-by-step algorithm of the generalized identification of the model of motion for the emitting target is proposed. The numerical experiments on rectiand curvilinear motion of the target are performed.
Adaptive compensation for interference-source signals in the radar system with a phased array antenna under completely polarized reception
Resumo
The algorithms for detecting a known useful signal against the background of intense interferences with an arbitrary law of time modulation multichannel radar system operating in the complete polarization basis is synthesized with the help of an adaptive Bayesian approach. The algorithm makes it possible to identify desired signals under the action of interfering signals even when both types of signals arrive from the same direction.
Theory and Methods of Signal Processing
Processing of signals from land-based radio emission sources in a monostatic air-borne monitoring system
Resumo
The problem of processing of signals from fixed land-based radio emission sources (RESs) measured in a monostatic air-borne radio monitoring system is considered. On the basis of the Bayesian approach, an optimal joint procedure for RES identification from radio measurements, estimation of RES state coordinates, and RES type recognition is developed. Relationships obtained in the synthesis of the joint procedure are analyzed. The results of application of the joint procedure are compared with the results obtained by independently synthesized algorithms for RES identification, estimation of RES state coordinates, and RES type recognition.
Algorithms for noncoherent iterative reception of signals based on serial turbo codes and Walsh signals during transmission over nonstationary channels
Resumo
The results of simulating the algorithms developed for noncoherent iterative reception of signals based on highly redundant serial turbo codes and Walsh signal ensembles are presented. It is assumed that transmission is carried out over nonstationary channels.
Information-theoretic analysis of efficiency of the phonetic encoding–decoding method in automatic speech recognition
Resumo
A words phonetic decoding method in automatic speech recognition is considered. The properties of Kullback–Leibler divergence are used to synthesize the estimation of the distribution of divergence between minimum speech units (e.g., single phonemes) inside a single class. It is demonstrated that the minimum variance of the intraphonemic divergence is reached when the phonetic database is tuned to the voice of a single speaker. The estimations are proven by experimental results on the recognition of vowel sounds and isolated words of Russian language.
Electron and Ion Optics
Bipolar diodes with divergent electron beam
Resumo
Cylindrical and spherical bipolar diodes with divergent electron beams are analyzed. A tendency related to the application of plasma structures in the classical devices of vacuum electronics working in the steady-state and pulsed regimes is discussed.
Physical Processes in Electron Devices
A coherent dual-frequency phase-sensitive reflectometer with amplitude modulation of probing pulses
Resumo
The results of investigation of a new type of the optical-fiber coherent phase-sensitive reflectometer with two different optical frequencies of probing pulses are presented. The use of pulses with different optical frequencies allows recovering of the signal of an external action on the reflectometer optical fiber by means of phase diversity technique. The applicability of the proposed technique is justified theoretically and experimentally.
Novel Radio Systems and Elements
A single-element diamond-based photodetector for UV spectrophotometry
Resumo
A single-element diamond-based UV photodetector that can be used for spectrophotometric facilities is demonstrated. The UV photodetector has photoelectric sensitivity depending on the value of the applied bias voltage. Experimentally obtained variable spectral responses of the photoelectric sensitivity are demonstrated. The applicability of such photodetectors for optoelectronic devices used in multicomponent spectrophotometric systems for the analysis of multicomponent mixtures is considered.