Seil Sautbekov

The Radiation Problem from a Vertical Hertzian Dipole Antenna above Flat and Lossy Ground: Novel Formulation in the Spectral Domain with Closed-Form Analytical Solution in the High Frequency Regime

We consider the problem of radiation from a vertical short (Hertzian) dipole above flat lossy ground, which represents the well-known “Sommerfeld radiation problem” in the literature. The problem is formulated in a novel spectral domain approach, and by inverse three-dimensional Fourier transformation the expressions for the received electric and magnetic (EM) field in the physical space are derived as one-dimensional integrals over the radial component of wavevector, in cylindrical coordinates. This formulation appears to have inherent advantages over the classical formulation by Sommerfeld, performed in the spatial domain, since it avoids the use of the so-called Hertz potential and its subsequent differentiation for the calculation of the received EM field. Subsequent use of the stationary phase method in the high frequency regime yields closed-form analytical solutions for the received EM field vectors, which coincide with the corresponding reflected EM field originating from the image point. In this way, we conclude that the so-called “space wave” in the literature represents the total solution of the Sommerfeld problem in the high frequency regime, in which case the surface wave can be ignored. Finally, numerical results are presented, in comparison with corresponding numerical results based on Norton’s solution of the problem.

Resonances in Reverse Vavilov-Cherenkov Radiation Produced by Electron Beam Passage over Periodic Interface

Resonances in reverse Vavilov-Cherenkov radiation produced by the charged particles beam passage over periodic boundary of dispersive left-handed medium are found out and studied. Analysis and modeling are performed on the base of rigorous mathematical approaches. For the first time, several physical peculiarities owing to these effects are considered in the conditions of possible resonant scattering of electromagnetic waves.

Diffraction Radiation Effects: A theoretical and experimental study.

This article is devoted to the theoretical and experimental study of diffraction radiation effects. Diffraction radiation is generated by the scattering of an eigenfield of density-modulated electron beam or a surface eigenwave of open dielectric waveguide on a nearby periodic structure. For the first time, these effects were studied using rigorous models exploiting exact absorbing conditions (EACs). This article also details the design and experimental testing of radiating elements for planar diffraction antennas with extremely low sidelobe levels, which exploit diffraction radiation effects.

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.

DOUBLY-PERIODIC PHOTONIC CRYSTALS: SPECTRAL PROBLEMS ANALYSIS

The present work is devoted to the clarification of the conditions necessary for step-by-step justification of the possibility of reduction of the homogeneous system of linear algebraic equations for the spectral problems of 2-D photonic crystals by the plane waves method. The issues related to the algorithms and the numerical solutions of these spectral problems are analyzed. The possibility of analytical regularization is investigated, and the ways to improve the convergence of the obtained results are identified.

Solution of the Neumann Problem of Diffraction by a Strip Using the Wiener–Hopf Method: Short-Wave Asymptotic Solutions

Plane wave diffraction by a strip is considered by the Wiener–Hopf method and the simple short-wave asymptotic solutions are obtained. The Neumann boundary value problem is reduced to the solutions of the Fredholm integral equations of the second kind, and the exact solution in the form of the sum of infinite series has been found by the method of successive approximations. With the help of the saddle point method, the integral operators are calculated and the asymptotic solutions of system are found. The outcomes are compared with supra known asymptotic solutions taking into account tertiary diffraction. Quarternary diffraction was solved and the calculation methodology for the subsequent diffractions was shown.

Diffraction Radiation Phenomena: Physical Analysis and Applications

The chapter is devoted to the problems of analysis and applied usage of the diffraction radiation phenomena, which are exploited in antennas and generators for millimeter and submillimeter waves. The diffraction radiation occurs when surface waves of open waveguides or eigenfields of charged-particle beams are transformed by periodic gratings into radiated fields. Main properties of the diffraction radiation phenomena have been studied using the given-current approximation and rigorous methods taking into account actual size of devices exploiting the phenomena. The algorithm of experimental synthesis of planar diffraction antennas with record-breaking low side lobes level has been developed and applied to design a real-world device.

Dyadic Green’s Function for Biaxial Anisotropic Media

In this chapter, authors construct the dyadic Green’s function for a biaxial anisotropic media. Among the obtained analytical results, worthy of mention are the representation of the singular part of the Green’s function in an explicit form and the representation of its regular part in the form of a relatively simple double integral over a limited region. These results are aimed at developing efficient numerical algorithms and asymptotic representations in the problems of wave scattering in anisotropic media.

Radiation of a magnetic dipole in hyperbolic uniaxial media

The fundamental solutions of a of Maxwells equations system for uniaxial anisotropic media are deduced by means of generalized functions method. In particular, the analytical solution of Maxwells equations for radiation of a point magnetic dipole in hyperbolic uniaxial media are obtained in vector form. The radiation pattern of a point magnetic dipole are constructed in such a medium.

The Exact Absorbing Conditions Method in the Analysis of Open Electrodynamic Structures: Circular and Coaxial Waveguides

The exact absorbing conditions (EAC) have been constructed and used for truncating an unbounded domain of computation in open initial boundary value problems, which describe space-time transformations of electromagnetic waves in axially symmetrical waveguides. The equivalence theorem is proved that gives grounds for rigorous theoretical justification of the EAC-method.