Radio physics and electronics

12-23

Authors: Guo Qiang, Luo Yi-yang, V. I. Lutsenko, Zheng Yu

Subject and purpose. Recently, there has been an interest in the use of non-equidistant active phased antenna arrays (AA) in airborne radars to facilitate the aerodynamics of the thermal regimes of their operation. Non-equidistant linear AAs reduce the number of antenna elements without noticeable loss of resolution (accuracy) and at the same time maintain a low level of side lobes. Almost all large antennas of radio telescopes and long-range radars are grids with non-equidistant arrangement of elements and with an unfilled aperture. The aim of this work is to develop new and non-traditional methods for constructing nonequidistant antenna arrays using Latin squares and cyclic difference sets. Results. The possibility of synthesizing large AAs based on the composition of squares using cyclic difference sets (CDS) for the formation of elements of Latin squares is shown. A method for their construction and a synthesis algorithm are proposed. The properties of this type of antenna arrays, which provide a sufficiently low side radiation at a high degree of rarefaction, are studied. The features and main characteristics of such antennas are investigated. Methods and methodology. The algorithm for calculating the coordinates of the antenna arrays using the values of the elements of Latin squares in this case is the same as in the construction of a lattice based on magic squares. It is based on the use of the value of the element of the generating matrix (the formed square) as the basis of the interferometer formed by the neighboring elements. The directivity patterns of the AAs were studied and the side lobe levels of the resulting non-equidistant antennas were estimated. Conclusions are made about the novelty of the proposed concept of constructing non-equidistant antenna arrays on the basis of Latin squares accepting the CDS as elements and its advantages in comparison with known methods. The possibility of synthesizing large antenna arrays on the basis of the composition of squares using the CDS for forming elements of Latin squares with small filling and redundancy coefficients and permissible values of lateral radiation is shown. In terms of characteristics, they are better than non-equidistant two-dimensional lattices, used up to the present time, constructed only on the basis of cyclic difference sets. The characteristics of the obtained lattices are studied. It is shown that the use of the Latin square, using the CDS as elements in the synthesized matrix, significantly improves its characteristics, and also provides a more flexible variation of the design parameters(v, k, l).

33-46

Authors: A. P. Nickolaenko, Yu. P. Galuk, M. Hayakawa

Subject and purpose of the work. In the present work, the perturbations are simulated of the amplitude of the vertical electric and horizontal magnetic fields of global electromagnetic (Schumann) resonance caused by the local ionosphere disturbance over the earthquake center with an account for the day–night non-uniformity. The source and the receiver are located at the same meridian symmetrically with respect to the equator at the points with coordinates 22.5° N and 22.5° S respectively. Position of the propagation paths is fixed relative the morning terminator: on its night (60° E) or the dayside (120° E). Variations of the amplitudes perturbation of the fields are considered when the localized non-uniformity moves along or across the propagation path. Methods and methodology. To determine the propagation parameters of extremely low frequency (ELF) radio waves, the full wave solution is used, which leads to the solution of the Riccati equation. The spectral components of the fields are found numerically using the two-dimensional telegraph equation. The results of the work. Numerical estimates are obtained of the influence of the local non-uniformity of the ionosphere on the amplitude of the electric and magnetic fields at different frequencies in the global electromagnetic (Schumann) resonance band for different positions of disturbance relative the propagation path located at the night or the dayside of the morning terminator. Conclusion. The influence of localized non-uniformity on the field amplitude increases with frequency. Field modifications in the presence of a local disturbance are of the interference nature due to interaction of the direct and the reflected from the local inhomogeneity radio waves. The day-night regular non-uniformity of the ionosphere plays a minor role and its influence might be neglected.

58-68

Authors: D. M. Glibitskiy, O. A. Gorobchenko, O. T. Nikolov, T. A. Cheipesh, T. N. Dzhimieva, I. S. Zaitseva, A. D. Roshal, A. M. Zibarov, A. V. Shestopalova, M. A. Semenov, G. M. Glibitskiy

Subject and purpose. In this paper, we studied the relationship of the structural and aggregation state of biopolymers with the quantitative characteristics of the textures of the films formed during the drying of biopolymer solutions. Methods and methodology. The structural changes of the biopolymer were determined by IR, UV and fluorescence spectroscopy, the size and surface potential of biopolymer particles were determined by dynamic light scattering, the state of the water environment was determined by microwave dielectrometry. To obtain films, saline solutions of calf thymus Na-DNA, bovine serum albumin (BSA) or human serum albumin (HSA) were dried in a glass cuvette under thermostatically controlled conditions. For the numerical characterization of textures, the relative area, fractal dimension and characteristics of zigzag patterns were used. Results. The paper presents a mini-review of the results during the development of a method for assessing the influence of biologically active substances (inorganic and organic) and physical factors (temperature and gamma irradiation) on biopolymers by the changes in texture parameters. It is shown that the formation of zigzag structures is sensitive to the structural and aggregation effects of biologically active substances and physical factors, and requires the presence of chloride ions. Conclusion. A method for assessing the influence of the corresponding factors by the changes in texture parameters is proposed. The presented results clarify the role of biopolymer, as well as salt cations and anions, in the formation of textures (in particular, zigzag structures) on the surface of films, and show the relationship of structural changes and aggregation of biopolymer with quantitative characteristics of zigzag patterns.