SCHUMANN RESONANCE IN THE MODEL OF THUNDERSTORM ACTIVITY, UNIFORMLY DISTRIBUTED OVER THE GLOBE
Y. P. Galyuk
The interest in the phenomenon of Schumann resonances arises from the fact that it is one of the few tools that can help you learn the properties of the lower ionosphere, the measurement of which by direct methods is extremely difficult (the satellites are flying above, and weather balloons – below). The phenomenon is caused by the presence of circumnavigation electromagnetic waves in the range of ultra-low frequencies, caused by the global thunderstorm activity. In solving inverse problems it is extremely important to have the most adequate mathematical model of the phenomenon, changing the parameters of which, one can achieve the perfect match between theory and experiment. The article sets out strict methods of calculation of ELF fields in the model of regular waveguide “Earth-isotropic ionosphere”, as well as the electric and magnetic components of the noise power.
RADAR TECHNIQUES FOR IDENTIFICATION OF DESERT REGIONS – THE SOURCES OF DUST IN THE ATMOSPHERE
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.
THE DETERMINATION OF NEARSHORE WAVES PARAMETERS BY THE INTERFEROMETRIC SYNTHETIC APERTURE RADAR
U. Goncharenko, G. Farquharson, V. Gorobets
Nearshore zones have a significant impact on life and economics. Along with the weather and climate stabilizing factor, caused by the water proximity, on the border of land and sea occur specific gradients and flows of heat, moist, pressure, etc. They might cause dangerous nature phenomena such as hurricanes, floods, etc. which need to be predicted and monitored. The remote sensing of neashore zone might be a part of such monitoring. The results of microwave remote sensing of neashore zone of New River inlet obtained by frequency-modulated continuous wave along-track interferometric synthetic aperture radar are presented. The estimation of neashore waves parameters such as wave height, phase velocity, etc. using ATI SAR images are performed. The algorithm for the estimation of bandwidth and shape of the radial velocity spectrum of braking wave is proposed and the dependence of the bandwidth of radial velocity spectrum on significant wave height is obtained.
ENERGY LOSS OF CHARGED PARTICLE ON THE WAVES EXCITATION IN SEMICONDUCTOR CYLINDER WITH TWO-DIMENSIONAL ELECTRON GAS ON THE SIDE SURFACE
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.
MICROWAVE LOSS IN LOW-ABSORBING DIAMOND-LIKE MATERIALS AT 1 K < T < 300 K.
THE PHENOMENOLOGICAL SIMULATION
R. V. Golovashchenko, V. N. Derkach, S. I. Tarapov
The development and manufacture of new materials for micro- and nanoelectronics are inextricably linked with the problem of studying the electromagnetic energy loss mechanisms in these materials in the gigahertz band. The reasonable technique of search for these mechanisms is the analysis of the temperature dependence of the loss tangent of such materials at temperatures from cryogenic ones to room ones. In this paper, the phenomenological simulation of loss in low-absorbing materials having a diamond-like crystal lattice is performed on the basis of experimental data. The experiments were carried out in the frequency range 60…120 GHz and at temperatures 1…300 K. The technique of measuring energy characteristics of the whispering gallery mode disk dielectric resonator is applied. As a result, the roles of main loss mechanisms for the materials under research are clarified and the values of basic physical parameters of materials are determined.
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.
K. A. Lukin, P. P. Maksymov
Creation of modern solid-state microwave power sources is based on the application of active elements with expanded functionality. The reverse-biased p–n-junctions with DC voltage are active elements of diodes generators. Avalanche-generator diodes (AGD) based on reverse-biased abrupt p–n-junctions with DC voltage are promising for creating diode generators. We investigated the static current-voltage characteristic of AGD by the methods of diffusion-drift theory. The induced current in the AGD external circuit was investigated. It was found that the spectrum of induced current is determined by the spectrum of auto oscillations of AGD. The results of the research are the theoretical basis for the creation of diode microwave generators with the requisite energy and spectral characteristics.
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.
E. A. Velichko, A. P. Nickolaenko
Nanowires and nanotubes made of noble metals are widely used in today’s technologies as elements of lasers, biosensors and other devices. However, not all possible problems arising in study of such objects are presented in literature. In this paper, by means of numerical simulation, the cylindrical nanoobjects made of gold and silver are considered as a specific prism that is capable of selecting isolated wavelength bands and scattering them at different angles. For this purpose a plane H-polarized electromagnetic wave scattering by nanocylinders with or without concentric dielectric cover or nanotubes made out of silver and gold in the visible range of wavelengths are studied. The scattering problem is solved in the classical manner, by separation of variables in polar coordinates. The complex permittivity is used in computations of gold and silver based on published experimental data. The results suggest that the studied nanoobjects can serve as a frequency-selective receiver or an optical filter which selects and rejects at different angles some wavelengths, but there is a great influence of geometrical parameters of scatterers and the dielectric constant of the coating.
COUPLING RADIATION LOSS IN THE MIRROR DIELECTRIC DISK RESONATOR.
PART 1. MATCHED WAVEGUIDE COUPLING
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.
V. V. Glamazdin, M. P. Natarov, V. N. Skresanov, A. I. Shubnyj
The coupling radiation loss of the whispering gallery mode mirror dielectric disk resonator (MDDR) with mismatched waveguides was researched. The findings are of particular interest to the developers of MDDR solid-state oscillators where semi-conductor devices and impedance matching circuits are located in the waveguide, forming a complex load in the waveguide. The dependences of MDDR resonance frequency and Q-factor on the amplitude and phase of the wave reflected from inhomogeneities in the waveguide back to the resonator are measured. Two types of couplers (a hole in the diaphragm on the mirror and an open end of the narrower waveguide on the mirror) are studied. For the open end type coupler it has been shown that MDDR resonant frequency and Q-factor can be calculated using the proposed lumped elements scheme of MDDR coupler and measuring procedure described in the first part of this paper. Coupling radiation loss and Joule loss in the load which are brought in MDDR by the complex load in the waveguide are calculated.
A. Ya. Kirichenko, G. V. Golubnichaya
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.
A. V. Brovenko, A. A. Vertii, N. P. Melezhik, P. N. Melezhik, A. Ye. Poyedinchuk
The problem of permittivity profile reconstruction from reflection coefficient data for a stratified dielectric medium illuminated with a probing plane electromagnetic wave at a finite set of frequencies is considered to deal with a topical problem in the context of the development of state-of-the-art nondestructive methods of testing. The initial problem is reduced to the search of an optimal control (permittivity profile) of the Cauchy problem for the Riccati equation. The optimal control is treated in the class of polynomial functions and is based on the minimization of a relevant functional. A criterion is suggested for choosing polynomial approximations to the permittivity profile, which separates input data sets between training and test sequences of probing frequencies. Error analysis made for the reconstruction of the permittivity imaginary part in a stratified medium shows that the relative error of the reconstruction does not exceed 10 % when the permittivity imaginary part is small (Ime ~ 10–4) and it is under 1 % when the permittivity imaginary part is large (Ime ³ 0.1). The developed algorithms can reconstruct the complex permittivity in a stratified medium to accuracy appropriate for practical applications.
MONITORING MICROWAVE IMPACT EFFICIENCY UPON THE BIOLOGICAL OBJECTS
O. I. Bilous, N. V. Bryuzginova, S. P. Sirenko, 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.