P. N. Melezhik

The H-polarized wave diffraction by a partially screened cylinder with magnetic active plasma properties: the analytical regularization procedure

Plane electromagnetic wave diffraction is considered as applied to a partially screened circular plasma cylinder with a related permittivity tensor The screening is realized with an infinitely thin and perfectly conducting unclosed circular cylinder with the generator parallel to the geometrical axis of the anisotropic plasma cylinder taken for the axis of a Cartesian coordinate system. The two-dimensional diffraction problem is considered.

Cherenkov radiation based antenna with the funnel-shaped directional pattern

ABSTRACT An axially symmetric diffraction antenna of a new type is presented and studied in details in the paper. The antenna is based on the effect of Cherenkov-like radiation. In contrast to diffraction antennas presented earlier, the proposed antenna does not contain periodic structures, which are effortful in manufacturing for millimetre and shorter waves. The antenna consists of a dielectric-filled cylindrical waveguide which feeds a biconical dielectric prism. Simulation results show that the proposed antenna has high efficiency, low sidelobe level, and the radiation pattern with high directivity. The proposed antenna could be used in various communication and radar systems.

1D inverse problems of electromagnetic theory of layered inhomogeneous anisotropic media

The inverse problems of the reconstruction of the dielectric permittivity tensor of multilayered inhomogeneous anisotropic slab by the reflection (transmission) coefficients known at the discrete sets of frequencies and angles of incidence are considered. The inverse problems have been reduced to optimal control problems for the Riccati equation. An analytical- numerical method for solving these problems has been developed. Numerical experiments demonstrating the computational efficiency of the proposed method have been carried out.

Inverse problems of electromagnetic sounding: Gradient medium and periodic boundary

The problems of the periodic interface profile reconstruction and the recognition of dielectric constant of the layered medium according to the values of the reflection coefficients for a finite set of probing frequencies are rather urgent in connection with the development of modern non-destructive testing methods. To solve them the original problems are reduced to the search for the optimal control (the profile of the dielectric constant) of the Cauchy problem for the Riccati equation. Construction of optimal control in the class of polynomial functions is based on the minimization of the corresponding functional. The criterion of selection of polynomial approximations for profile permittivity uses the separation of input data into Training and Testing sequences of probing frequency. An analysis of errors of the reconstruction of the imaginary part of permittivity of the layered medium was carried out.

Analytical-numerical method for solving problems of electromagnetic wave diffraction by the local cylindrical inhomogeneity

An analytical-numerical method for studying the diffraction characteristics of the inhomogeneous magnetodielectric circular isotropic cylinder excited by linearly polarized plane electromagnetic wave is suggested. The method is based on the construction of special solutions to the Cauchy problem for the Riccati equation and gives the opportunity to investigate the diffraction process for this type of structures.

Resonant Cherenkov type radiation in dispersive metamaterials

The radiation of moving charged particles makes a fundamental problem in modern physics and has long been the subject of a thorough study [1-26]. As early as 1889, O. Heaviside considered the electromagnetic field of a point charge uniformly moving in a dispersion-less medium and was seemingly the first (as follows from the literature) to ask himself: What happens when the charged particle velocity, u exceeds the velocity of light v in the medium? He found that the spherical wave front of particle radiation takes a conical shape with the semi-angle θ = ν/u reported in his Theory of Electromagnetism, volume 3, 1905 [1]. Later, Lord Kelvin got also curious about the matter and proposed in his lecture on thermal radiation [2], in 1900 that an atom moving at a speed exceeding the speed of light produces a conical wave, as it holds upon Mach principle in acoustics. In 1904, A. Sommerfeld considered a purely theoretic and even hypothetic problem on electron movement in a vacuum at a velocity exceeding the velocity of light there and concluded about the directional property of electron radiation [3]. However the advent of the relativity theory did Sommerfelds conclusions out of question, for the relativity theory keeps physical bodies away from the movement at a velocity equal or, the more so, exceeding the velocity of light. This conflict with the relativity theory might give a reason why the problem of supraluminal speed movement of charged particles was left out of consideration.

Resonant plane wave scattering by a grating of rectangular bars and a metamaterial

Research into the special features of the wave processes in open structures (open waveguides and resonators, diffraction gratings) completed with metamaterials [1, 2] attracts considerable interest and both allows formulation of new physical principles of electromagnetic wave generation, amplification and channeling and promotes adoption of such specific properties of the electromagnetic field in these structures as Doppler shift inversion, changes of Cerenkov radiation direction, etc. [1]. An important stage in these studies is the research into resonant effects arising during the plane monochromatic electromagnetic wave diffraction by single-periodic structures with metamaterials [3]. In this report, resonant phenomena occurring in the H-polarized plane wave scattering by a grating are discussed. The grating is made of rectangular perfectly conducting bars, the slots are filled with a metamaterial, its effective permittivity depending on the excitation wave frequency. In a frequency region where the real part of the effective permittivity of the metamaterial takes on negative values, a denumerable set of frequencies with a finite accumulation point has been found at which the reflection coefficient comes close to a unit. This anomalous reflection is caused by the excitation of specific oscillations localized on the metamaterial-vacuum interface.

Electromagnetic-wave diffraction by a strip grating with a layer of planar-stratified medium

A new solution approach to problem of wave diffraction by an inhomogeneous magnetodielectric layers, whose permittivity and permeability are piecewise continuous functions of a single spatial coordinate, was proposed in [1]. The approach is based on the reduction of the Helmholtz equation to the Riccati differential equation. The original numerical algorithm using a robust recurrence formula was constructed to calculate the solution integrals of the Riccati equation.In this work utilizing the results [1] we develop a high-performance method of the diffraction characteristics calculation for a periodic strip grating lying on an inhomogeneous dielectric layer. The excitation by an obliquely incident plane electromagnetic wave is considered.

Development of up-to-date sea surface-object monitory radar facility “Burevestnik-1” installed at naval and sea border guard surveilance point

The makeup and technical data of the state-of-the art X-band radar system referred to as “Burevestnik-1” have been described. This system is designed to ensure engineering supervision and sea-surface objects monitoring when accommodated at surveillance outposts, on river boats, sea-going vessels including high-speed ships.

X-band coaxial magnetron with field and secondary emitters

The findings of experimental investigations into and the field fests of the X-band cold, secondary - emission cathode magnetron referred to as “Buton” are presented. The primary - electron producing source in this system are the field emitters (FE). In addition to this, the data on 3-D simulation of the secondary-electron multiplication (SEM) process in this type of magnetron are given. The batch-produced “Buton” magnetrons are shown to offer an actual working capacity with 50ns to 6μs - width of e.m. radiation pulses. One of the noticeable features of these magnetrons installed in the transmitters of the lot-produced “Burevestnik-1” radar facility was their trouble-free operation time that lasted for over 12000 hours.