Radio physics and electronics

10-15

Authors: I.M. Mytsenko, D.D. Khalameyda

Subject and Purpose. Statistical data on how the satellite signal level varies with changes in the characteristics of tropospheric layers and lower-troposphere hydrometeors serve designers a useful guide in the development of systems for diagnosing weather conditions and hydrometeor characteristics. The aim of the work is to generalize results from the long-term research into daily dependences of X-band radio signal attenuation between the geostationary satellite and Earth terminals. On this basis it is possible to find relationship between signal level changes at the point of reception and geophysical atmospheric agents. Methods and methodology. A receiving measuring and recording complex developed by the authors is employed for the purpose of establishing relationship between geostationary satellite signal level at the receiving point and geophysical atmospheric agents. Results. A block-diagram of the receiving measuring and recording complex is presented, its operation described. Geometric parameters of the radio signal path of propagation have been considered. Signal level measuring results obtained using a Hot Bird geostationary satellite in the period from 03 to 17 January 2019 have been generalized and interpreted. Conclusions. X-band radio signal attenuation on the path from a geostationary satellite to the Earth has a daily dependence. The radio signal level variations are not connected with alterations in spatial and technical parameters of the geostationary satellite or receiving equipment. The day and night changes in radio signal level are attributed to different daytime durations and different angles of sunbeam (including twilight) incidence on tropospheric areas associated with the receiving antenna pattern in the propagation direction, which entails changeable temperature regime and moisture content in these areas. Geophysical agents in the highest tropospheric layers insolated from far beyond the horizon can also be interpreted for long-distance tropospheric radio wave propagation in these tropospheric regions.

23-31

Authors: Yu.O. Pedenko, A.V. Bukin, N.G. Reznichenko

Subject and Purpose. The Matrix Pencil method is investigated as a means of increasing the accuracy of measuring the angles of low-altitude targets above sea level. The aim of the study was to evaluate its effectiveness in the conditions of interference created by multi-beam propagation, represented by mirror and diffuse reflection of radio waves from the sea surface, and thermal noise of radar receiving channels, and to justify measures to achieve high efficiency in different combinations. and obstacle levels. Methods and Methodology. The study was conducted by computer simulation. It covered the sea waves, which met the conditions of both specular and strong diffuse reflection, as well as different levels of thermal noise in the receiving channels of the radar. Typical conditions were used in the simulation: the length of the route – 2000 m, the height of the center of the receiving antenna at sea level – 12 m, the width of the antenna beam – 1°, the angular height of the target – 0.3°. The effectiveness of the method was determined by comparing it with the previously studied method of root-MUSIC under identical conditions. Results. The data on the errors of measuring the place angle when using different a priori parameters of the Matrix Pencil method are obtained. Recommendations for the choice of these parameters have been developed to minimize errors in measuring the angles of the place. The advantages and disadvantages of the Matrix Pencil method in comparison with the root-MUSIC method are noted. Conclusion. The obtained results can be used in the development of radars designed to support low-altitude objects above sea level.

37-45

Authors: Yu.O. Averkov, Yu.V. Prokopenko, V.M. Yakovenko

Subject and Purpose. Eigenwave studies of various bounded structures make a prolific line of investigation in both modern radiophysics and solid-state and functional electronics. Conducting solids demonstrating plasma (semiconductor) properties attract particular attention. Owing to the high conductivity of semiconductors (as it is inversely proportional to the charge carrier effective mass that is smaller than the free electron mass), interest exists in propagation features of slow elliptical-polarization electromagnetic waves – helicons – in magnetized semiconductor waveguides. The present work aims to determine eigenwave spectra of a solid-state plasma cylinder in a strong constant concentric magnetic field. Methods and Methodology. The eigenwave theoretical study of a magnetoplasma cylinder in the free space is conducted in terms of Maxwell's equations. The motion equation of conduction electrons of a solid-state plasma is adopted with quasi-stationarity electromagnetic field conditions satisfied. The collision frequency of majority charge carriers is assumed substantially less than their cyclotron frequency. Results. The dispersion equation of a cylindrical solid-state plasma (semiconductor) waveguide has been obtained. It has been shown that a collisionless magnetoplasma waveguide supports propagation of bulk and surface helicons. The propagation is accompanied by the surface current flowing lengthways cylinder components. Charged particle collisions destroy the surface current and initiate additional (to helicons) H-type hybrid waves such that their phase velocities coincide with phase velocities of the helicons. It has been found that the nonreciprocity effect holds for the waveguide eigenwaves having identical field distribution structures but different azimuthal propagation directions, and it also does as soon as the external magnetic field changes its sense. Conclusion. The research results have deepened our understanding of physical properties of bounded structures with plasma-like filling media. More systematization has been added to the knowledge of eigenwave behavior of these structures in a quasi-stationarity electromagnetic field.

54-66

Authors: N.P. Yeliseyeva, S.L. Berdnik, V.A. Katrich

Subject and Purpose. Two impedance resonant monopoles of electric length 0.2 £ l / l £ 0.3 are mounted on a rectangular screen perpendicularly to the screen surface and studied for the directional radiation properties (directive gain and radiation patterns) depending on the monopole separation and the side length and aspect ratio of the screen. Methods and Methodology. A three-dimensional diffraction vector problem of two impedance monopoles mounted on a perfectly conducting rectangular screen is solved in terms of the uniform geometric theory of diffraction. Allowances are made for the diffracted field asymptotics of the secondary diffraction at the screen edges and for the electric current distribution asymptotics of a thin impedance dipole in the free space. Results. For a lattice of two impedance monopoles mounted on a rectangular screen, 3-D programs have been developed for calculating its radiation patterns, directive gain Dmax at a radiation maximum, and radiation resistance in view of the secondary diffraction at the screen edges. The radiation pattern shaping for the diffraction and total fields and the directive gain Dmax have been analyzed depending on the monopole separation x / l  0.1...1, the screen side length x / l  1.2…4, and the screen aspect ratio W / L  0.5…3. It has been shown that the so obtained optimum separation x opt  0.65, optimum length Lopt and optimum ratio (W / L) opt make Dopt three times greater than the lowest Dmax value. Conclusions. The three-dimensional vector problem of field diffraction of two impedance monopoles mounted on an ideally conducting rectangular screen has been solved. It is of interest that given an optimum monopole separation xopt and an optimum side length Lopt of the square screen, a lattice of two monopoles offers a greater radiation resistance and a two times larger Dopt than a single monopole on the same screen does. The developed computational programs and the obtained numerical results enable efficient actual wireless communication systems to be modelled for both ideally conducting and impedance resonant monopoles.