Radio physics and electronics

13-25

Authors: A. V. Brovenko, A. A. Vertiy, N. P. Melezhik, P. N. Melezhik, A. Ye. Poyedinchuk

A numerical analytical method of the reverse problem solution is suggested for the relative permittivity profile of layered inhomogeneous media to be obtained from the frequency dependence of the reflection coefficient of a monochromatic plane electromagnetic wave. The idea of the method is to reduce the initial reverse problem to the optimal control problem of the Riccati equation. The solution scheme employs a numerical analytical method for the direct problem solution of monochromatic plane wave diffraction by layered inhomogeneous media and takes advantage of some algorithm developed for smoothing the gradient of the residual functional. With the algorithms elaborated for solving the direct and reverse problems of wave diffraction by layered structures, a series of numerical experiments has been performed, the efficiency of the suggested approach in not a direct determination of layered structure parameters is demonstrated.

32-39

Authors: A. P. Nickolaenko, M. Hayakawa

We model an effect on the Schumann resonance signal recorded in Japan of the ionosphere non-uniformity centered above the earthquake at Taiwan. Changes in the resonance spectrum occur due to interference of the direct radio wave with one reflected from the ionosphere modification above the earthquake. The first part addresses typical models of ELF radio propagation constant and connects it with the vertical profile of atmospheric conductivity. The profile with a knee is analyzed, which is widely used for modeling the Schumann resonance. The four models are included suggested in literature for obtaining the frequency dependence of complex propagation constant of ELF radio waves. It is assumed that the pre-seismic and seismic activity locally reduces the height of the lower-boundary of the ionosphere above the earthquake. The maximum reduction reaches 20 km, and the horizontally symmetric perturbation is described by Gaussian curve having the scale of 1 000 km.

48-57

Authors: V. K. Ivanov, A. Ya. Matveev, V. N. Tsymbal, S. Ye. Yatsevich

Aeolian processes transporting sand and dust is a powerful erosive force that shapes the structure of the surface of the vast territories and loads the atmosphere with aerosols suspended dust spread by wind over long distances. The presence of atmospheric dust in the environment of the planet is one of the factors significantly affecting the temperature and climatic conditions of vast regions. There are no published data on the characteristics of the radio waves scattering features manifested in radar studies of aeolian sand and dust transport processes in desert regions, which can be used for determining the parameters of a remote transport. The article presents the results of the analysis of multiyear surveys of desert areas by side-looking radars (SLR) of “Cosmos-1500” and “Sich-1” satellites, synthetic aperture radars (SAR) of ERS-1, ERS-2 and Envisat-1, aimed at identifying the radio waves scattering features manifested in radar studies of aeolian sand and dust transportation processes in desert regions, which can be used for remote determining the parameters of transportation. It was proposed to explain the mechanism of the effect of a highly directional intense radio waves backscatter, which manifests itself in areas covered with deep sand at the direction of irradiating the surface towards the general direction of the surface wind in the range of local irradiation angle surface Q » 31¸34°, due to their interaction with consistently oriented ionized air layers bordering on sand ripples structures in the process of forming it with aeolian transportation of sand-dust mixture. Ionization is caused by strong inhomogeneous electric field arising in the aeolian transport process. Results of the study allow to create new remote monitoring methods of processes in desert areas that affect the climate of vast regions of the Earth.

62-67

Authors: N. N. Beletskii, S. A. Borysenko, N. I. Gvozdev

The defect photonic crystals bordering on the solid-state plasma-like media are worthy of special attention. These structures are of interest due to the occurrence of the plasma and defective waves which can interact resonantly with each other. The effect of resonance interaction of different types of electromagnetic waves in defective photonic crystals is not adequately investigated. In this paper, the resonance interaction of plasma and defective TM-electromagnetic waves in a one-dimensional defect dielectric photonic crystal, bordering on the solid-state plasma-like medium, is studied on the basis of the numerical solution of the dispersion equation. The dispersive and energy properties of plasma and defective waves are investigated in accordance with the dielectric constant of the crystal lattice of the solid-state plasma-like medium. It is found that the resonance interaction of plasma and defective waves depends strongly on the type of solid-state plasma-like media. It is established that the effect of resonance interaction between the plasma and the defective waves takes place when the defective photonic crystal borders on the semiconductor plasma. It is shown that the resonance interaction of plasma and defective waves disappears in the case when the defective photonic crystal borders on metal. The results of the study extend significantly our knowledge about the nature of the resonance interaction of plasma and defective waves in defect photonic crystals. The obtained results can be used in developing new devices of microelectronics and photonics.

81-84

Authors: R. I. Bilous, S. P. Martynyuk, A. P. Motornenko, I. G. Skuratovskiy

The resonance structures serve as the basis for many electronic devices. Therefore the creation of the effective tunable resonator is the actual and important problem. Using of the waveguide-dielectric resonator insures opportunity for the mechanical frequency tuning over a wide range but at the same time the Q-factor is changed. The last investigations suggested that the decrease of the eigen Q-factor of the tuning waveguide-dielectric resonator in the section of the circular cut-off waveguide can be decreased by using the resonance short-circuit plunger calculated on the given frequency. The investigations have been conducted for the 3-cm waveband. This paper is devoted to investigation of the possibility to increase Q-factor of the resonator of the waveguide-dielectric type in the millimeter band where influence of the contact imperfection between the plunger and waveguide walls is essential. As a result of the conducted investigations the Q-factor more than 2 000 in over the band of the tuning frequency was obtained for the resonator made of the section of the circuit cut-off waveguide with the Teflon dielectric in the 8-mm waveband.

94-98

Authors: Yu. A. Nestryzhenko

The laser emission polarization and control of its spectrum by means of low-loss prisms is a problem of considerable importance which has been addressed in a great number of research papers. The known polarizers, especially straight view prisms, are characterized by certain disadvantages arising from losses of light energy and/or a need for additional reflecting coatings. These are not always acceptable for laser application, and the problem of spectral control may require the use of additional elements in the laser cavity. In this paper a four-facet, straight view spectral polarizing prism is described involving no cemented components for controlling the laser polarization and spectrum. The effect is due to additional total internal reflection surfaces inside the prism. Theoretical calculations have confirmed feasibility of such a prism for relatively simple, e. g. rhomboid configuration, and the possibility of manufacturing the device in a simple way. The prototype embodied has been tested and showed an effective laser polarization and possibility of its spectral control. This prism can greatly simplify the procedures for laser tuning, providing new possibilities for polarizational and spectral control of the laser emission and generation of two orthogonal polarized rays which may be useful for effective frequency conversation in nonlinear crystals.