ALGORITHMS WITH STABILIZING COEFFICIENTS FOR SOLVING POORLY DETERMINED RADIOPHYSICS PROBLEMS
A. A. Kurayev, V. V. Matveyenko, T. L. Popkova
This article describes the algorithms with correcting and stabilizing coefficients to provide sustainable solutions to systems of equations related to poorly determined tasks of electrodynamics and nonlinear dynamics. It demonstrates the use of the modified algorithms in the task of E0i-waves propagation in irregular waveguide and dynamic model of Rössler’s chaos. In the latter case the article demonstrates that “deterministic” (i. e. regenerating) chaos is impossible.
A RADIOMETER FOR METEOROLOGICAL MEASUREMENTS WITH ACCURATE CALIBRATION BY THE SKY BRIGHTNESS TEMPERATURE
V. A. Kabanov
Methods for passive sensing the atmosphere in the microwave range are one of important directions of remote sensing of environmental protection. To develop simple and cost-effective technical solutions and radiometric measuring techniques is an important task. A simple mobile radiometric system of 3-cm wavelength range designed for meteorological research has been presented. The radiometer is made on the basis of modulation scheme with some features of construction elements and input calibration. A method for accurate determination of the sky brightness temperature used for calibrating radiometric system has been proposed. A variant of constructing a radiometer with the use of satellite converter gas been implemented.
SETUP AND CALIBRATION OF THE RADIOREFRACTOMETER FOR MEASUREMENT OF THE ATMOSPHERIC REFRACTIVE INDEX
V. A. Kabanov
The most accurate information on the dielectric structure of the atmosphere can be obtained by radiorefractometers. These devices are essential when measuring a fine structure of the refractive index of the medium under investigation. The information obtained through them is particularly important in studies of tropospheric radio propagation conditions. Despite the advantages of refractometers compared with meteorological measurements, the task of calibration remains important. A brief description of a microwave refractometer developed by the author is presented. It shows the ability to set up and calibrate the instrument using standard meteorological measurements without a special reference chamber in a closed room.
BEYOND-THE-HORIZON RADIO WAVE PROPAGATION AND SURFACE OBJECTS RADAR OBSERVATION IN THE NORTH-WESTERN AREA OF THE PACIFIC OCEAN
F. V. Kivva, I. M. Mytsenko, A. N. Roenko
In general, the coverage range of vessel navigation radars in different areas of the World Ocean is determined by radio wave propagation conditions in these areas. Therefore, the experimental data introducing clarity into diagnosis and prognosis methodology of radio wave attenuation factor is of a great interest. The paper presents the results of experimental researches on radio wave attenuation factor distance dependences and coverage range of vessel navigation radars in the north-western part of the Pacific Ocean. The attenuation factor of direct and reflected signals was studied simultaneously with meteorological researches and investigations of formation conditions of surface ducts and inverse layers. Attenuation factor distance dependences, statistical distribution functions of evaporation duct heights, and data on vessel navigation radar coverage ranges were obtained. The results of the researches promote deeper understanding of the processes in the lower atmosphere layer above the ocean surface that determine the conditions of radio wave propagation and coverage range of vessel navigation radars in different areas of the World Ocean.
THREE-FREQUENCY REMOTE SENSING OF LIQUID PRECIPITATION
A. Linkova, G. Khlopov
The study of integral and microstructure characteristics of liquid precipitation is of great practical interest for solution of many problems of national economy. Particularly, monitoring rain intensity is important for design of collecting systems and engineering structures, as well as it essentially influences productivity of agriculture. Radar methods for study of liquid precipitation permit to measure rain parameters over the large areas in real time. That is why they are more preferable in comparison with contact methods based on raingauges and disdrometers. A three-frequency method for radar remote sensing of liquid precipitation is proposed and studied in this paper, which allows restoring spatial profile of rain parameters. The results of numerical simulation of three-frequency radar remote sensing of liquid precipitation are presented; they were obtained for different sets of operating wavelengths of radar for the range of rain intensity 0…30 mm/h. It is shown that the usage of millimeter wavelengths is not reasonable due to strong attenuation of signal power at large distances and for large rain intensities. However, application of longer wavelengths permits to reduce influence of attenuation and to decrease measurement errors of rain parameters. The maximal measurement error of rain intensity is not more than 7 %.
ABOUT THE IMPACT OF COMMUNICATION CHANNEL ON GNSS RADIOSIGNALS PROPAGATION IN THE KHARKIV REGION
S. R. Shchekin, F. V. Kivva, V. N. Gorobets, A. L. Kovorotniy
In the paper we presented the results of systematic measurements of the positioning precision of several stationary navigation stations with known coordinates, which are equipped with single- and dual-frequency GPS/GLONASS navigation receivers. Particular attention has been paid to environment parameters caused by rains (including summer rains with thunderstorms), snowfalls, fogs and clouds. The experimental investigations of the fluctuations of zenith tropospheric delay and spatial coordinates of the reception stations located at the distance of 5.8 km have been performed. The factors which limit the maximum permissible positioning precision have been evaluated. The results of the paper are relevant to the problems of operative prediction of the meteorological phenomena and researching their physical properties.
V. I. Khizhnyi, A. P. Korolyuk, T. M. Khizhnaya
High temperature antiferromagnets such as iron borate, hematite etc., have high magnetoelastic coupling. As a result, in the conditions of birefringence effect, there is a possibility to control parameters of sound waves by a small external magnetic field. On the other hand, high magnetoelastic coupling raises the sensitivity of sample magnetic system to external mechanical influences, for example from the side of acoustic contacts with piezotransdusers. In this paper the effect of contactless (electromagnetic) sound generation in external magnetic field, while minimizing the impact of external mechanical stresses on the magnetic properties of the sample is experimentally studied. As a result, the birefringence effect at the electromagnetic excitation of high-frequency ultrasonic wave is detected, which is of interest from the viewpoint of its instrument application. Comparison of a theory of birefringence effect with experimental data is conducted. The magnitude of a magnetoelastic gap for iron borate is obtained.
AlGaInAs GRADED-DAP GUNN DIODE
I. P. Storozhenko, М. V. Kaydash
Gunn diodes are the active elements for generating electromagnetic waves in the millimeter range. An urgent task of today is to increase their cutoff frequency and output power. One of the ways to do it is to use graded-gap semiconductors. The paper presents the results of numerical experiments on the electromagnetic waves generation with the help of Gunn diodes based on graded-gap AlGaAs-GaAs-InGaAs compound. The numerical simulation has been conducted by means of the temperature model of intervalley transfer of electrons in the graded-gap semiconductors. The length of the diode active area was 2.5 mm with the concentration of ionized impurities therein 1016 cm–3. We have shown that the AlGaAs-GaAs-InGaAs-diodes can be used as active elements for generating electromagnetic oscillations in the millimeter wave range. In GaAs-InxGa1–xAs- and Al0.2Ga0.8As-GaAs-InxGa1–xAs-diodes the output power increases almost linear with InAs percentage in the range from 0 to 50 %. As it turned out GaAs-Ga0.5In0.5As-diode has the greatest value of the output power Р = 12,2 kW´cm–2 at frequency of f = 45 GHz and efficiency of h = 10.5 %. Al0.2Ga0.8As-GaAs-In0.5Ga0.5As-diode has the greatest generation efficiency of h = 11,3% at Р = 10.6 kW´cm–2 and f = 41 GHz output power and generation efficiency of Al0.2Ga0.8As-GaAs-diode in 2 to 3 times lower than the parameters of mentioned above diodes. Our findings extend the knowledge of the physical processes of carrier transport in complex semiconductor structures and can be used for technological development of new high-performance devices based on A3B5 semiconductors.
V. V. Ovsyanikov
The present paper analyses the period of birth and development of science and technology of dipole antennas with reactive and complex loads, microwave dielectric and plasma antennas, as well as dipole and helical electrically small antennas, multi-frequency, broadband and pin antennas with improved radiation pattern, loop antennas and antenna arrays. We have considered the methods of evaluation and calculation of the basic parameters of antennas, such as the current distribution, input impedance, voltage standing-wave ratio, efficiency, radiation pattern and polarization characteristics. The results of calculations and the design features of these antennas were considered.
WAVE PROPAGATION IN A CIRCULAR BELOW CUTOFF TWO-LAYERED WAVEGUIDE WITH HIGH LOSS LIQUID AT FREQUENCY RANGE 5…30 GHz
Z. E. Eremenko, K. S. Kuznetsova
Methods for determination of complex permittivity of high loss liquids are essential in various fields of science and technology. The propagation of electromagnetic waves in a circular two-layer metal waveguide with a central low loss dielectric rod, surrounded by high loss liquid in the microwave range has been studied. The dependencies of the complex wave propagation constant on frequency and the magnitude of the liquid layer were obtained. The presence of high loss liquid surrounding the dielectric rod, allows expanding the range of operating wavelengths from the millimeter to centimeter range. The value of the decay constant is relatively small. Thanks to a high loss medium, this waveguide structure does not have a fixed value of the cutoff frequency. An anomalous low value of the attenuation constant of the electromagnetic wave has been detected at the centimeter wavelength range for certain operating frequencies and liquid layers. The proposed structure can be applied as a measuring cell for the determination of the complex permittivity of high loss liquids in small volumes.
N. G. Kokodii, V. О. Timaniuk, E. Ya. Levitin, M. V. Kaydash
Nowadays, methods for determining the optical properties of nanoparticles are being actively developed and improved. The most popular are optical methods, in particular those that investigate the dependence of the spectral intensity of radiation passed through the medium with the particles, because they are less sensitive to a particle shape. In the scientific literature there are many works studying separately the scattering and absorption of light. There are few applied scientific works studying attenuation of light. In this paper the algorithm for processing the measurement data of the light attenuation by suspension of nanoparticles is proposed. The algorithm consists of three phases and provides information about the size and the complex refractive index of the particles. In this study, firstly, the average particle size was measured by method of power function, secondly, the optical properties of the particles were measured by method of spectral transparency and thirdly, the function of the particle size distribution was determined. The algorithm has been successfully tested during the measurement of the size and optical properties of Ag–Fe3O4 nanoparticles in water.
O. M. Stadnyk, O. O. Silin
The problem of generalization of the classical results on the electric dipole radiation over the Earth's surface in the case of the left-handed metamaterial half-space is important for many practical applications related to the focusing of wave fields. It is desirable to do without undue simplifications: geometrical optics approximation, neglecting losses, restrictions on the wave packet associated with the introduction of the group velocity, neglecting the type (only monopole) of source. In the paper, the model problem of radiation of elementary electric dipole situated normally to the plane boundary between dissipative left-handed and ordinary media has been rigorously solved. The numerical simulation revealed the expected radar pattern-like structure of the reflected field in the first medium and complex (on average tapered) interference field structure with a pronounced maximum in the region of the left-handed metamaterial half-space. The spatial distribution of the electromagnetic field in two media, depending on the height of the dipole and the magnitude of losses in the left-handed metamaterial is presented. The analysis of the Poynting vector streamlines confirmed the hypothesis, previously put forward by the authors, that the change in sign of the tangential component at the interface, that is common for electromagnetic surface waves, is the cause of the focusing ability of the boundary between the normal and the left-handed media, rather than each of them individually.