Radio physics and electronics

10-17

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

Atmospheric dust is a mixture of minute particles of various salts and minerals; it also contains the remains of plants and animals, spores of pathogenic microbes, etc. The winds carry the dust over long distances, and its presence in the atmosphere is one of the factors that significantly affect the planet's climate. Currently, for space monitoring of aeolian processes and their consequences only multispectral optical systems are used (TOMS, METEOSAT, MODIS, etc.); they cannot identify the areas which are the sources of raising dust in the atmosphere regardless of clouds, brightness and transparency of the atmosphere. This problem can be solved by the space remote sensing radar systems. The article presents the first results of processing the method of radar identification of desert areas in which under the influence of aeolian processes the process of raising dust from the surface to the atmosphere takes place. The testing was performed using the data of radar remote sensing of Mauritania deserts of SAR Envisat-1. The peculiarities of manifestation of focused backscattering of radio waves in radar images at different speeds of surface wind, surface radar radiation and wind directions were analyzed. It is concluded that applying the radar remote sensing to identify areas raising dust in the atmosphere is effective. The results of the study allow to create new methods of remote monitoring of processes in desert areas, affecting the climate of vast regions of the Earth.

24-30

Authors: A .V. Dormidontov, Yu. V. Prokopenko, V. M. Yakovenko

One of the urgent problems of modern radiophysics is the study of the fundamental properties of solid-state structures that contain nanodimension fragments. Studies of the excitation mechanisms of electromagnetic waves when the charged particles move in various electrodynamic systems form the basis of electronics. In this case, a number of the fundamentally important characteristics of structures include their dispersion equations. They allow to determine the place of electrodynamic structures in the radio physical systems of different purposes. An energy loss of a charged particle per unit time on the waves and/or oscillations excitation in the system is the data characteristic. In electrostatic approximation the dispersion equation describing the eigenmodes of semiconductor cylinder with the layer of two-dimensional electron gas on the side surface (3D+2D-plasma) has been obtained. The energy loss of charged particle was found when it was moving in external magnetic field that has the intensity vector parallel to the symmetry longitudinal axis of the 3D+2D-plasma of cylindrical configuration. It was noted that the obtained relation has the universal character. With the help of it the energy loss may be determined for rotary motion of particle around the cylinder and its translational motion parallel to the cylinder generatrix. The effect of non-reciprocity of the eigenmodes excitation of 3D+2D plasma cylinder was discovered. These modes have identical structures of the field distribution, but differ in the propagation direction along the azimuthal coordinate. Research results extend our conceptions about the electrodynamic properties of systems with plasma mediums and systematize the knowledge of the excitation mechanisms of electromagnetic waves in electrodynamic systems that form the basis of microwave devices.

39-44

Authors: O. V. Sytnik, S. A. Masalov, G. P. Pochanin

The actual problem of measuring the thickness of the surface layers of the soil using GPR radar systems under stringent restrictions on the minimum length of a video pulse and under the presence of the noise caused by resonance effects in antenna and multiple reflections of the sounding signal from the boundaries between media has been studied. Traditional extreme correlation signal processing methods do not provide the resolution less than half of the total duration of the pulse. To overcome this limitation is possible by using nonlinear methods, for example the homomorphic signal processing. The possibility of high resolution of subsurface stratified media boundaries by using non-linear homomorphic digital signal processing of reflections is proved theoretically and experimentally. The proposed method has used the non-linear spectrum transformation of ultra wideband sounding signals. It allows getting resolution approximately to 5 % of pulse duration instead of limitation of the traditional correlation method of signal processing. The FFT algorithm is used to calculate the amplitude spectrum of the signal, the result is subjected to logarithms and then the inverse Fourier transform is computed, to get a signal's cepstrum containing the probe signal and digital signal delay. The analysis of cepstrum at a relatively high signal to noise ratio allows one to calculate the estimate of the thickness of the layer. The results of simulations and experimental data processing are also shown.

54-61

Authors: K. A. Lukin, P. P. Maksymov

The actual task of semiconductor electronics is development and creation of diode generators of microwave power on the basis of active elements with the extended functional possibilities. It is shown that avalanche-generator diodes (AGD) on the basis of abrupt p–n-junctions with constant voltage of the reversed bias are the generators of microwave power. The theoretical analysis of mathematical model of AGD is based on the decision of the complete system of equalizations of diffusive-drifting model describing physical processes in a diode taking into account the influence of charge of mobile carriers on the electric field. A limiting cycle and invariant torus is certain in the phase plane of AGD. It is shown that at high voltage of the reversed bias on abrupt p–n-junctions in AGD there is an internal feed-back between the electric field and avalanche current, resulting in current instability and generation of two-frequency oscillations. The results of theoretical analysis of AGD can be of practical interest to developers of powerful dual-frequency sources of electromagnetic waves of microwave range.

70-79

Authors: V.V. Glamazdin, M.P. Natarov, V.N. Skresanov, A.I. Shubnyj

The application of open resonators in the measurement technique or in the generator oscillation systems requires taking into account the influence of coupling elements (CE) on the open resonator (OR) characteristics. The additional radiation loss takes place under the OR excitation or energy output process. It is not known about investigations of such loss in mirror dielectric disk resonators (MDDR) with whispering gallery modes, which are the type of OR. The results of experimental investigation of the radiation loss of the MDDR CE with matched waveguides are presented. Two methods of measurements, the impedance method and the method of power balance, were modified for application to MDDR and used for investigations. Two types of CE have been studied: the hole in the thing metal wall on the surface of the MDDR mirror which is connected to the rectangular waveguide and the narrow slot on the mirror surface which is smoothly transformed to rectangular waveguide. The results of radiation loss characteristics measurements, their dependence of sizes and disposition relative to the disk are presented. Comparison of the characteristics of different CE has been made. It has been shown that slot CE have higher efficiency, both excitation and output, than hole CE.

87-91

Authors: A. Ya. Kirichenko, G. V. GolubnichayaPARTICULARITIES OF INTER-TYPE INTERAC

Disc dielectric resonators with whispering gallery modes are usually characterized by high Q-factor, nevertheless, dense spectrum of these oscillation is the factor which impedes their use as microwave elements. In particular, inter-type interaction of oscillations results in the distortions of amplitude-frequency characteristics. The investigation of particularities of this interaction allows one to understand conditions when they appear and find the possibilities to avoid them. The particularities of inter-type interaction in disk quasioptical resonator, excited at high azimuthal modes, in the case of internal excitation of parasitic oscillations in single disk are investigated experimentally. The influence of parameters of coupling element between the resonator and dielectric waveguide on the resonance characteristics is studied. It is shown, that this influence can be compensated by introducing the additional irregularity. Also it is demonstrated, that parameters of two-hump resonant characteristic strongly depend upon azimuthal position of this irregularity. Till the present time the intermode interaction was investigated only in the case of external excitation, using two disk dielectric resonators. The obtained results can be used as a method for selection of disc dielectric resonator oscillation spectrum.

98-101

Authors: O. I. Bilous, N. V. Bryuzginova, S. P. Siren ko, A. I. Fisun

UHF-radiation is used in medicine for medical treatment and diagnostic. Low-level and super low-level radiation influence is named as the information one. In this case the heat balance of bioobjects is unchanged. The UHF-autohemotherapy with microwave blood activation is one of the ways of the present-day physiotherapy. In this paper it has been proposed to monitor the efficiency of this physiotherapeutic procedure by means of testing the electrophoretic mobility of nuclei of buccal epithelium cells. The set of the experiments is carried out for the purpose of corroboration of the possibility to make an estimation of the neurological pathology treatment in traditional medical way and by the UHF-autohemotherapy.