Transient excitation of coaxial cone antenna

In relation to the using of ultrawideband signals in radar and radiocommunication there appeared a variety of mathematical methods for solving the problems for such signal radiation and propagation. One of them is the method of evolutionary equations relating to the analytical methods in time domain.The essence of the method is that the basis for electromagnetic field expansion is constructed in cross-section. This permits to represent the field in waveguide or free space as a package of the modes and to trace their changes with longitudinal coordinate and passage of time. This requires to solve the evolutionary equation system that represents the second-order partial differential equations of Klein-Gordon type with given initial and boundary conditions. It is convenient to use the method for solving transient problems of radiation and propagation of waves excited by sources with arbitrary time dependencies in layered nonhomogeneous and nonstationary media.In work [2] the characteristics of the coaxial cone antenna (CCA) with a infinite screen are studied theoretically and experimentally in receiving mode. The radiator is the cone antenna excited by step of current. However, at theoretical analysis there considered only one specific case of time current dependence and used the Fourier transform of the solution for sinusoidal waves.The goal of this work is to investigate the videopulse radiation from coaxial cone antenna theoretically by means of the methods of Evolutionary Equations and Duhamel integral as well as to check experimentally the obtained results

Artificial neural networks in time domain electromagnetics

The application of artificial neural networks (ANN) is considered to the problems of electromagnetics in time domain. Amplitudes of electromagnetic field in definite points of observation in different moments of time are proposed for using as initial values for an input layer of neural network. As examples the different structures of ANN were applied to solve the problem of determination of layered medium parameters by reflected transient field analysis. The incident field is plane wave with Gaussian time dependence. The stability of the determination of medium geometrical and electrical characteristics is studied for the case of presence of experimental errors, outer interferences, and instabilities of medium parameters

Radiation of transient fields from the open end of rectangular waveguide

The problem of the excitation of a rectangular waveguide by a transient current is solved in the time domain by the evolutionary equation technique and the Riemann function method. The field radiated from the open end of a rectangular waveguide is calculated in the Kirchhoff approximation using the vector potential method. The dependences of the amplitude of the radiated field on time and angle are investigated and compared with numerical results

The energy of the field radiated by Hertz dipole

All components of electromagnetic field radiated from Hertz dipole excited by current with arbitrary time dependence are obtained in time domain by means of vector Hertz technique. The processes of transformation of quasistatic components of field into electromagnetic wave are investigated. The problem of radiation of Hertz dipole with quickly decreasing dipole moment from some constant value to zero is considered. The questions of describing the process of the forming of free electromagnetic field from quasistatic field components in near field zone of dipole are discussed

Calculation of experimental apparatus for biological object irradiation by impulse electromagnetic field

The problem of homogeneous irradiation of biological solutions by impulse electromagnetic field is investigated. The optimization of construction and sizes of the apparatus for the irradiation is carried out by direct numerical calculation in time domain. Uniformity of heat distribution is studied

Analysis of fields reflected from model of human body surface using artificial neural network in time domain

The problem of determination of thickness a layer of layered medium by impulse irradiation is considered. The impulse fields reflected from the model of human body surface are analyzed by artificial neural network in time domain directly. The normal incidence of plane wave with Gaussian time form on the layered medium with losses is considered. The reflected electromagnetic field is obtained by FDTD method. Initial data for neural network analysis are the values of amplitude of electrical component of reflected field. As an example, the network is trained to determine the thickness of one of the layers of the medium. The stability of the determination in presence of interferences, experimental errors and instabilities of medium parameters is investigated by numerical simulation

Combined vibrator-slot structures theory and applications: theoretical aspects and applications

The book presents solutions to a complex of internal and external problems of electromagnetics associated with the development of theory, construction of mathematical models and the development of rigorous methods for calculating the electrodynamic characteristics of combined vibrator-slot structures. The solutions of problems for determining the characteristics of impedance vibrator and slot radiators with arbitrary geometric and electrophysical parameters presented in the monograph were obtained within the framework of the unified methodological approach to construct asymptotic solutions of integral equations on currents and their systems. This approach made it possible to study a number of new combined vibrator-slot structures. The research results reveal the possibilities of using such structures as basic elements in the creation of modern antenna-waveguide devices operating in the ranges from meter to millimeter wavelengths, with new technical characteristics and functional purpose. The book is intended for senior and postgraduate students and researchers working in the fields of radiophysics, radio engineering and antenna-feeder design. The book covers the following topics: • excitation of electromagnetic waves in volumes with coordinate boundaries; • general issues of the theory of thin impedance vibrators and narrow slots in a spatial-frequency representation; • solution of current equations for isolated vibrator and slot scatterers; • combined radiating vibrator-slot structures in rectangular waveguide; • T-junctions of rectangular waveguides with vibrator-slot structures in coupling areas; • waveguide radiation of the combined vibrator-slot structures; • combined vibrator-slot structures located on a perfectly conducting sphere; • combined vibrator-slot Radiators in antenna arrays; • ultrawideband vibrator-slot structures;

Transient radiation from the open end of circular waveguide

The transient radiation from the open end of a circular waveguide is considered by simple analytical and direct numerical methods. The radiation of short pulse from the aperture is provided by calculation of special time form of field by means of modal basis method that permits to solve the problem of pulse evolution for positive and negative time with the use of Laplace transform. The radiation of the short pulse is calculated in Kirchhoff approximation and simulated by FDTD method. The frequency characteristics of the radiated field are considered

Near field of Hertzian dipole excited by impulse current

The angle dependence of near field radiated of Hertzian dipole excited by transient current is investigated. The more precise approximation in the solution for near field of the dipole is obtained in time domain by means of vector potential technique. As an example, the quickly decreasing excitation current case is considered

Simulation of microwave exposure of human cells by electromagnetic field of EMF band

To implement a novel method of investigation of electromagnetic field action on state of cell nucleus the simulation of irradiation of the cells of human buccal epithelium by electromagnetic field of EMF band is carried out. The cells were exposed to radiation of frequency f = 36.64 GHz, with power densities W = 10–1, 1 and 4 W/m2during 10 seconds. To answer on the question of existence of nonthermal biological effect of electromagnetic field onto living cells the specific absorption rate (SAR) of a solution that contained cells is calculated. The numerical simulation based on FDTD method permitted to take into account different parts of experimental setup to obtain real distribution of electromagnetic field inside irradiated solution