


卷 59, 编号 4 (2016)
- 年: 2016
- 文章: 8
- URL: https://journals.rcsi.science/0033-8443/issue/view/15147
Article
Retrieval of the Near-Surface Wind Velocity and Direction: Scat-3 Orbit-Borne Scatterometer
摘要
The new concept proposed during the development of the first Russian orbit-borne scatterometer SCAT-3 requires an additional study for estimating its efficiency and comparison with the current scatterometer concepts. Using the fan antenna pattern (with angular dimensions 1◦ × 6◦), we have reduced the antenna rotation speed by about a factor of three compared with the prototype (the “SeaWinds” scatterometer) and measured the backscattering cross section for each wind cell at the horizontal and vertical polarizations. The numerical model of the scatterometer was developed with allowance for the technical characteristics of the radar, orbital parameters, and observation scheme. The scatterometer operation is simulated with the subsequent swath formation and partitioning into the wind cells. It is shown that using the fan pattern in the scatterometer, one can improve the accuracy of the wind-direction r5etrieval in a wind cell due to employing the radiometric resolution in the processing algorithm. The main error in determining the wind direction is related to the ambiguity ±180◦, which is caused by the type of the azimuthal dependence of the backscattering cross section. With the help of the two-dimensional median filtering, we can significantly reduce the wind-direction retrieval error. This error can probably be smaller than that for the current scatterometers.



The Spectral Statistical Method for Determining the Location Parameters of a Dipole Source of Electromagnetic Radiation
摘要
Using the measured horizontal and vertical components of the magnetic and electric fields, respectively, we solve the problem of determining the location of a dipole source of electromagnetic radiation, which is equivalent to the lightning discharge, at the specified point of an infinitely conducting plane. The proposed method, which is based on the analysis of the measured-signal spectra, allows one to develop many estimates of the source location, choose the final estimate on the basis of the results of analysis of the entire totality of these estimates, and, therefore, reach stability in determining the source location. The spectral method makes it possible to obtain more stable solutions at a lower computation cost compared with the previously developed parametric extremum method. The spectral-method algorithm can be naturally parallelized. The results of the analytical and numerical studies of the accuracy and stability of the proposed method are presented.



Analysis of Surface Waves in an Elastic Medium with Aquifer
摘要
We study propagation of seismoacoustic waves in a three-layer medium consisting of a homogeneous isotropic solid deformable layer loaded on a uniform liquid layer above a homogeneous isotropic solid half-space. This medium models a geological section in which the top soil layer is separated from the deep rock by an aquifer. The dispersion relation is obtained and analyzed, and its solutions for cases that are important from the practical point of view are presented. Features of the dispersion curves and spatial distribution of the mode fields made it possible not only to reveal the existence of an aquifer under the top soil layer, but also determine its thickness and depth. It is shown that the ratio of vertical and horizontal components of the displacement vector measured on the Earth’s surface is a significant parameter for solving the geological medium reconstruction problem.



Small-Size Waveguide Diplexer Based on E-Plane Quasi-Planar Filters
摘要
We propose a new small-size version of a waveguide diplexer based on quasi-planar filters with E-plane ridge sections and inductive diaphragms on a single metal inset made of a thin foil. The diplexer contains an E-plane waveguide bifurcation and a matching stepwise transition. The effective hybrid method, which is based on the Galerkin method allowing for the field singularity at the edges, the mode matching method, and the generalized scattering matrix method, has been developed for electrodynamic analysis of the given class of diplexers. We present characteristics of the optimized version of the design of a centimeter-wave diplexer, whose length is approximately 1.5 times shorter compared with known counerparts.



Diffraction Theory of Two-Mirror Echelette Resonators
摘要
We develop the theory of a two-mirror resonator, in which one mirror is an echelette diffraction grating. The diffraction loss related to the finite sizes of the mirrors, the loss determined by the existence of a mirror diffraction maximum of the grating (coupling loss), and the ohmic loss are taken into account. We show the possibility of constructing a resonator with one high-Q mode in a wide frequency band. This mode can be used as the working mode of a gyrotron operated at the second gyrofrequency harmonic, which interacts efficiently with the electron beam. We also demonstrate the possibility of frequency tuning of the resonator in a frequency band of 1%, while retaining the parameters which are satisfactory for gyrotron operation, and a high degree of resonator selectivity (i.e., the presence of a single mode).



Twisting of Polarization of the Light Beam in a Multiply Scattering Medium
摘要
We calculate the intensity and the main mode of linear polarization, i.e., the difference in the intensities of the orthogonally polarized components, for the case of oblique incidence of a linearly polarized light beam on a disordered medium. It is assumed that multiple scattering has a sharply anisotropic character. The vector equation of radiation transfer is solved neglecting the difference in the amplitude of single scattered waves, when light becomes depolarized due to polarization twisting in the process of multiple scattering. It is shown that the angle at which the maximum of the polarization degree is observed decreases as the depth increases much slower than the angle corresponding to the intensity peak.



Estimation of the Potential Interference Immunity of Radio Reception with Spatial Signal Processing in Multipath Radio-Communication Channels. I. Decameter Range
摘要
We propose a method for estimating potential interference immunity of radio reception in the multipath radio-communication channels. Using this method for the modified Watterson model of the decameter radio channel, we study the achievable interference immunity of devices with spatial signal processing.



Ground-Based Microwave Monitoring of Middle-Atmosphere Ozone Above Peterhof and Tomsk During Stratospheric Warming in the Winter of 2013–2014
摘要
We present the results of studying the dynamics of middle-atmosphere ozone above Peterhof (60°N, 30°E) and Tomsk (56°N, 85°E) during stratospheric warming in the winter of 2013–2014 by the radiophysical method. In the ground-based observations we used the same microwave ozone meters (operated at 110.8 GHz) and the same techniques both for measuring the radiation spectra of ozone molecules and estimation of the vertical distribution of ozone in the middle atmosphere. These results were compared with satellite data on the total ozone content TOC (OMI/Aura), altitude profiles of ozone and temperature in the layer 20–60 km (MLS/Aura), and also with the data on ozone content in the layer 25–60 km, which were obtained using a Bruker IFS-125HR infrared Fourier spectrometer in Peterhof. Significant variations in ozone, which were caused by a stratospheric warming of the minor type, were observed in the atmosphere above Peterhof at altitudes of 40 to 60 km. The duration of dynamic perturbations above Peterhof was 2.5 months. Dynamic processes associated with the horizontal transport of air masses, which had an impact on the vertical structure of ozone in the middle atmosphere, were also detected above Tomsk, but this effect was less dependent on the background temperature variations.


