Radio physics and electronics

11-17

Authors: 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.

25-32

Authors: 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.

40-47

Authors: 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.

52-57

Authors: 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.

74-82

Authors: 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.

88-96

Authors: 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.