Перегляд за Автор "Lytvynenko, O. A."
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Документ Algorithms of multi frequency radiometry in the conditions of broadband interference(Одеський національний університет імені І. І. Мечникова, 2018) Orlov, V. V.; Lytvynenko, O. A.; Galanin, V. V.The development of digital technologies for multi-frequency signal reception in the low-frequency range creates the prerequisites for the application of optimal algorithms for real-time beamforming without changing the aperture of the radio telescope antenna. In the present paper, a model of the system based on multiplicative processing (MP) is considered and investigated. The system consists of two antenna arrays, the signals from the outputs of which pass through the narrowband filters of receiving devices. After filtration, they undergo MP and weighted summation. Next, we consider an algorithm for the formation of a narrow beam of the antenna pattern (AP) of a multi-frequency radio interferometer based on the well-known cosinusoid summation method. Its meaning lies in summing up the results of multiplicative processing of signals from the outputs of several spatially separated different scales bases. In work, using MP, a method is proposed for reducing the width of the main lobe of AP on one base by receiving signals at several frequencies. The further development of the method is associated with the optimization of the AP in multifrequency MP, which leads to the possibility of lowering the side-lobe levels by weighing the signals from the outputs of the MP channels. For this purpose, for the sum of odd cosine waves, it is necessary to determine the weighting factors that ensure the minimum root-mean-square level of side lobes in a given zone of AP suppression. As a result of MP processing, we obtain a decrease in the amplitudes of side lobes with an insignificant increase in the width of the antenna pattern of the antenna system. In work the algorithm of suppression of broadband hindrances is also considered. The synthesis of the optimization algorithm is reduced to the need to determine the weighting coefficients and frequencies that provide the minimum rms level of the side lobes of the AP in a given zone of suppression, with a limited range of frequency separation. These methods are proposed to use in radio astronomy to improve the quality of research.Документ Angular structure of FRII radio sources 3C169.1 and 3C263 at decameter wavelengths(Одеський національний університет імені І. І. Мечникова, 2016) Vashchishin, R. V.; Shepelev, V. A.; Lozinskyy, A. B.; Lytvynenko, O. A.The radio galaxy 3C169.1 and the quasar 3C263, located at nearly the same distance with red shift z>0.6, have similar morphological and spectral characteristics. The maps of the sources obtained at decimeter and centimeter wavelengths have shown they are FRII radio sources with steep spectra and approximately equal angular sizes. The very first investigation of the sources structure at decameter wavelengths is presented in the report. Observations were made using a network of the URAN decameter interferometers with baselines 42 to 950 km and with maximum angular resolution of arcsec order of magnitude. The models of the image of these sources based on visibility functions measured have been obtained at frequencies of 20 and 25 MHz. They were composed of elliptical components with Gaussian brightness distribution. To facilitate the comparison of these lowfrequency models with high-frequency radio images, the latter were converted to the similar models by fitting the Gaussian components to lobes and hot spots selected at the maps. Comparison of the models revealed changes in a structure of the sources caused by the frequency decrease.Документ Ionosphere response to solar eclipse effect on magnetosphere(Odessa I.I. Mechnikov National University, 2009) Derevyagin, V. G.; Lytvynenko, I. O.; Lytvynenko, O. A.Документ Radio telescope Uran-4 and the problem of radio interference(Одеський національний університет імені І. І. Мечникова, 2018) Galanin, V. V.; Lytvynenko, O. A.; Derevyagin, V. G.; Kravetz, R. O.The URAN-4 decameter radio telescope, which is located in the village of Mayaki of the Odessa region, is an element of system of the URAN radio telescopes (Ukrainian Radiointerferometer of the Academy of Sciences). The radio telescope is used according to the following scientific programs: measurements in the composition of the Interferometer with the Super Large Base (VLBI), to study the angular structure of discrete radio sources; the study of the nonstationarity of the flux of cosmic radio sources and the study of the influence of the space environment on the characteristics of the received signals. RT URAN-4 operates at frequencies of 10-30 MHz and consists of an antenna and an equipment complex. A telescope antenna is an electrically controlled phased array of 128 turnstile vibrators. It identifies two linear signal components and is endowed with the possibility of changing the position of the antenna pattern in space (2048 discrete positions of the beam). The geometric dimensions of the array 238 meters (West-East direction) and 28 meters (North-South direction). The size of the antenna pattern in the modulation mode of signal reception at a frequency of 25 MHz is 2.7 x 22 degrees. In the VLBI interferometer mode, a resolution of about 2 seconds of arc is realized. The instrumental complex of the RT URAN-4 is represented by two types of modulation radiometers, which make it possible to measure the flux densities of radio sources and apparatus intended for VLBB measurements. The working frequency range in which RT URAN-4 operates has a high level of radio interference. The work gives definitions of interference acting in the decameter range. Considered methods of dealing with them. One of the methods to combat interference is the work of the radio telescope on the frequencies permitted and legally protected from interference, the list of which is given in the article. The paper deals with issues related to the organization of the security zone around the radio telescope. On its territory, the maximum allowable power for existing nearby transmitting radio facilities and interfering industrial facilities should be legitimized, in the designated working lanes. At the same time, a monitoring service for the radio spectrum should be organized. The paper deals with the developed and manufactured portable direction finder. Its characteristics are given, recommendations on its use are given.Документ Simple radio telescopes of low frequences(Odessa I.I. Mechnikov National University, 2009) Lytvynenko, I. O.; Lytvynenko, O. A.; Koshukhar, V. B.