SCIENCE & EDUCATION

pp. 235-248

pp. 190-204

pp. 140-152

pp.550-559

pp. 560-572

pp. 573-581

pp. 633-644

pp. 582-592

pp. 593-606

pp. 607-618

pp. 619-632

The paper proposes a development of the methodological support to determine vibration amplitude of the ship hull remotely using a coherent radar centimeter range on the variation of the Doppler signal spectrum reflected from a vibrating surface.It is proved that the level ratio of the spectral density at the frequency of vibration and at the frequencies of its multiples are determined by a single parameter – the phase modulation index, which is linearly related to the amplitude of vibration. As a result of field experiments it has been established that the energy of the surface gravity – capillary waves range has a high correlation with the wind speed. The paper shows a method of restrictions due to interference caused by the scattering a radio signal from the water surface.

The paper presents a novel method for tapered slot antennas analysis in time domain. The method is based on «two-step» approximation, including both the radiating slot longitudinal segmentation and the full-wave model for each slot segment. Segment radiation is approximated using Green’s function for magnetic source on a conducting half-plane. Exploited earlier, mainly, for frequency-domain analysis of electrically long antennas, the method presented in this paper has been improved to apply it in analysis of arbitrary antenna shape. For the first time, time-domain antenna parameters were calculated using such approach for test geometries. Attained results have given evidence that the method is of high accuracy.

An algorithm for generating ensembles of two classes N and Di nonlinear binary code sequences that are optimal in the sense of boundaries of packaging is presented. On the basis of this algorithm and its program realization in C#, ensembles of sequences of different lengths are obtained and their correlation properties are analyzed in detail. In the ensemble the sequences with the best properties are selected. The undoubted advantages of the N and Di sequences include the correlation properties and their substantial set of lengths. On the basis of the performed calculations the conclusions can be made about the prospect application of studied classes of sequences designed for spread spectrum systems with code division multiplexing.

The authors propose a digital method of measuring the phase shift of quasi-harmonic signals with the same instantaneous frequency on a limited sample. A real-time algorithm was created on the basis of the specified method; the proposed algorithm was tested in numerical simulations and experiments at the developed hardware-software package. The measurement error of the phase difference of harmonic signals in the experiments did not exceed 10^-6 rad while the measurement error of signals with amplitude modulation of 20% was less than 5 ∙ 10-⁵ rad. The method could be used to solve problems of radio interferometry, acoustics, etc., where the unknown value us expressed in terms of the phase difference of quasi-harmonic signals.

The authors carried out an electro-dynamic analysis of the line parameters’ dispersion characteristics of the segments of balanced stripline-slot antennas of traveling waves with different configuration. A dispersion model of the twin-strip line was presented. Dispersion equations were obtained by reduction of the original system of integral equations relating the currents and the electric fields in the cross section of the transmission line to a homogeneous system of linear algebraic equations by means of the spectral Galerkin method. In order to find the components of the two-dimensional Green tensor function the method of spectral immitances was used. Analysis of test line geometries was carried out.

The authors consider several signal processing algorithms in an on-board radar system with a multi-channel phased antenna array used for detection of small, low-speed targets. These are: split space and time non-adaptive processing, space-time adaptive processing and space-time adaptive processing with pre-beam forming in elevation plane. A simple method of result comparison for mentioned algorithms is described. The results of computer simulation of the output signal-to-(noise + interference) ratio are also presented. The particular results were obtained for a coherent impulse sequence with mean repetition frequencies.

The authors propose an algorithm for extracting navigation data from GNSS signals. Analysis of this algorithm was carried out with the use of mathematical simulation of a signal tracking system; data from navigation GLONASS (GNSS) space vehicles was used as input information. The authors provide curves displaying dependence of navigation message restoration quality on the signal to noise ratio (SNR) representing different methods of synchronization.

 The authors propose an algorithm which estimates and corrects the MIMO-OFDM-channel with frequency-selective fading in phase noise on the basis of the multidimensional digital Kalman filter. The channel model is constructed in the form of autoregressive function based on the Jakes model. White frequency noise is considered as a model of phase impact. Research results of the algorithm show its high efficiency in fast fading. The authors performed parametrical adaptation of the proposed algorithms and formulated approaches to assessment and correction of channel parameters with account of the features and structure of the data packet technology 802.16e /m, E-UTRA release 9 (LTE-Advanced). 

In this paper structural and parametric synthesis of PLL frequency synthesizers is proposed. The peculiarity of these devices includes existence of both external and internal noise in the system, which, in this case, does not allow to apply the classical method of structural synthesis based on the theory of optimal linear and nonlinear filtering. To solve the problem two steps were proposed. At the first stage optimal filters are synthesized separately for external and internal signal and noise sources. At the second stage structural synthesis is used, which includes properties of optimal filters obtained at the first stage.