A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Spectral Techniques for Estimating Characteristics of Secondary Sources in Multipath Propagation Channels
The potential of spectral analysis is considered as for determining the number of signal modes arriving at the reception point through a multipath propagation channel. The technique has been used to determine the number and coordinates of reflecting points, as well as their lifetimes the diffuse-scattering sea surface. Also, reflection factors, location heights and motion velocities have been estimated for elevated inversion layers in the troposphere.
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Filtering Methods for Frequency-Modulated Signals Based on the Robust Amplitude Estimation and Clipping Technique
An analysis of the frequency-modulated (FM) signal distribution law has allowed the authors to suggest two new estimation techniques for the FM signal amplitude, fit for signals distorted either by gaussian or nongaussian noise with the “heavy-tail” probability distribution law. Two methods of FM signal reconstruction have been developed on the basis of the clipping filtering and the suggested amplitude estimation algorithms. A comparative analysis has been performed for the developed methods and the known filtering approaches utilizing the sliding window technique and the robust discrete Fourier transform. The proposed methods evidently improve the quality of the FM signal reconstruction if compared with the prior approaches.
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
The Accurate Two-Dimensional Model of the Effect of the Surface Waves Transformation into the Spatial Modes
The accurate mathematical model of radiation of the natural electric modes of a planar dielectric waveguide on finite number of rectangular grooves cut off on the surface of the perfectly conductive screen has been developed. Such structures are widely used in antennas of diffraction radiation. The cases of finite and zero gaps between the waveguide and the screen have been considered separately. The influence of the coupling on the diffraction characteristics of the antenna has been investigated.
1A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
2National Technical University
21, Frunze Str., Kharkiv 61001, Ukraine
Microwave Losses in a Quasioptical Dielectric Resonator as a Function of the Thickness of Ultra-Thin Conducting Endplates
We report on a large sharp variation (~103 times) of the quality-factor of a quasioptical dielectric resonator with conducting endplates in the form of ultra-thin copper films as their thickness changes only to ~0.9 nm. The measurements have been carried out in the 8-mm waveband at room temperature. An explanation of the effect is represented based on both the microwave properties of the resonator with a film and the dependence of continuity of ultra-thin copper films on the thickness.
1National university «Kyiv-Mogilyan Academy»
2, G. Skovorody Str., Kyiv, 04070, Ukraine
2 M.M. Bogolyubov Institute of Theoretical Physics, NAS of Ukraine
14 B, Metrologichna Str., Kyiv, 03143, Ukraine
Dynamics of the Davydov Soliton in Electrostatic Field
The paper considers the influence of an electrostatic field on the self-localized state dynamics of quasiparticles in a one-dimensional molecular chain. It was shown that a weak electrostatic field accelerates the propagation of the quasiparticle along the chain, which can explain the charge transport processes in molecular systems. The dependence of quasiparticle velocity and its lifetime on field magnitude and the other system parameters was analyzed. As demonstrated below, a resting quasiparticle, belonging to a ring chain, having accumulated some sufficient portion of energy, starts moving in a however weak but non-zero electric field.
A. Usikov Institute of Radio Physics and Electronics,
National Academy of Sciences of Ukraine
12, Academician Proskura Str., Kharkiv 61085, Ukraine
Electrodynamics Properties of Surface Waves, which Propagate Along the Boundary of Two Layer Periodic Semiconductor Structures
The electrodynamics properties of new type of surface waves, which propagate along the boundary of two various layer periodic structures, were considered. The analytic formulas for dispersion of these waves were received and the accounts of dispersion curves of surface waves were given. It was found that two types of waves were existed: surface waves, where dispersion curve asymptotically tends to hybrid plasma frequencies, and surface waves between „dielectric zones”, when w>>whibrid. The phase velocity depending on the collision frequency in semiconductor was investigated. It was shown, that increase of minimal wave velocity is conditioned by the growth of part of energy in layer with great dissipation.
Institute of Radio Astronomy, National Academy of Sciences of Ukraine
4, Krasnoznamennaya Str., Kharkiv 61002, Ukraine
Modeling, Investigation and Optimization of 100 KW Coaxial Microwave Plasmatron Design
Using computer-aided simulation, the influence of geometric dimensions of the coaxial microwave plasmatron on characteristics of the field in a discharge chamber has been investigated. The problem of matching of a rectangular waveguide feeding with large-size coaxial diameter plasmatron has been studied. New types of coaxial-to-waveguide junctions which have sufficiently broad transmission band and capable to operate with high power level have been proposed. It is demonstrated that the mode interference in the coaxial of the plasmatron might cause heterogeneity upon the angle of the field structure in discharge chamber. The methods for testing the field structure in the plasmatron discharge chamber with two-mode operation has been studied, and its effect on the characteristics of the discharge has been analyzed. Several types of optimized plasmatron structures presenting an interest for practical applications, including microwave-plasma burners for coal dust combustion are suggested.
Duration of Unit Elements of Discrete Signals
Kharkiv National University of Radio Engineering and Electronics,
14, Lenin Ave, Kharkiv, 61166, Ukraine
Improvements in the Autoregression Technique of Speech Signal Processing
The question of synthesized speech quality improvement using additional processing of prediction remainder low-frequency component was considered. 30 samples of phonemes “a” and “oo” were taken for analysis. Analysis of quality improvement was made using cepstrum estimation method. Quality improvement was 16.51% for “a” phonemes and 35.26% for “oo”.