Showing papers on "Computational electromagnetics published in 1977"

Elements of engineering electromagnetics

Abstract: Emphasizing practical applications, this approach integrates IBM PC BASIC programs and numerical techniques with the principles of engineering electromagnetics. This book discusses on-line parameters by numerical techniques and inserts a section on capacitance, conductance and inductance.

Numerical Electromagnetic Code (NEC) - Method of Moments. A User-Oriented Computer Code for Analysis of the Electromagnetic Response of Antennas and Other Metal Structures. Part III. User's Guide. Volume 2. Revised.

Abstract: : The Numerical Electromagnetics Code (NEC-1) is a computer code for analyzing the electromagnetic response of an arbitrary structure consisting of wires and surfaces in free space or over a ground plane. The analysis is accomplished by the numerical solution of integral equations for induced currents. The excitation may be an incident plane wave or a voltage source on a wire, while the output may include current and charge density, electric or magnetic field in the vicinity of the structure, and radiated fields. Hence, the code may be used for antenna analysis, EMP, or scattering studies. This manual contains instruction for use of the Code, including preparation of input data and interpretation of the output. Examples are included that show typical input and output and illustrate many of the special options available in NEC-1. The examples exercise most parts of the Code and, hence, may also be used to check that the Code is operating correctly.

New Method for Computing the Resonant Frequencies of Dielectric Resonators (Short Papers)

Abstract: A new method is develop for accurately predicting resonant frequencies of dielectric resonators used in microwave circuits By introducing an appropriate approximation in the field distribution outside the resonator an analytical formulation becomes possible Two coupled eigenvalue equations thus derived are subsequently solved by a numerical method The accuracy of the results computed by the present method is demonstrated by comparison with previously published data

Electromagnetic coupling through small apertures in a conducting screen

Abstract: The electromagnetic field coupling through small apertures illuminated by an arbitrary incident plane wave is discussed for general aperture shapes. A set of new integral equations in a form highly amenable to numerical solution techniques is derived. Based on the application of the Rayleigh series method, an analytical solution is obtained for the first few terms of the expansion of the aperture E - field of a circular aperture. Numerical results are also constructed for the aperture field and the diffracted field of small rectangular apertures and compared with those of the circular apertures.

Electrogravitational conversion cross sections in static electromagnetic fields

Abstract: We use Feynman perturbation techniques to analyze a classical process: the conversion of gravitational waves into electromagnetic waves (and vice versa) under the "catalytic" action of a static electromagnetic background field. Closed-form differential cross sections are presented for conversion in the Coulomb field of a point charge, electric and magnetic dipole fields, and uniform electrostatic and magnetostatic fields. Using the model calculation of conversion in a Coulomb field, we discuss the problems we must face when calculating non-gauge-invariant quantities, as is frequently done in literature. The cross sections are extremely small, but may lead to observable effects if allowed to act on astrophysical distance and time scales. The calculations also provide additional insight into the physics of electromagnetic detectors of gravitational waves.

Unified Approach to the Derivation of Variational Expression for Electromagnetic Fields

Abstract: A unified procedure to derive the variational expressions for electromagnetic field problems is presented. It is shown that the variational expressions for a variety of electromagnetic parameters such as, for instance, a resonant frequency, a propagation constant, and an impedance matrix, can be formulated systematically all from "the principle of least action" point of view. It is pointed out that the Maxwell's equations themselves can also be derived from the least action principle.

The scattering of electromagnetic radiation from dielectric scatterers

Abstract: The problem of electromagnetic wave scattering from arbitrarily shaped scatterers recently solved by using an integral equation formulation is extended to treat the case of scattering by infinite cylinders. The method is based on describing the internal field of the scatterer in terms of an independent set of plane wave functions. Numerical stability conditions are satisfied. Numerical results are presented for cylinders of elliptic cross section for two independent incident waves. Results are also given for scattering by three-dimensional spheroidal scatterers of refractive index n0=1.33. The solution presented is applicable for scatterers with size parameter (k0a) from the Rayleigh region (k0a >1) provided for each given scatterer certain matrix elements can be calculated.

A progressive numerical method and its application to large field problems in antennas and electromagnetic scattering

Abstract: It is shown that the numerical solution of electromagnetic scattering problems using moment methods can be carried out in a progressive manner by dividing the scattering surface into several small regions. The technique reduces the large matrix of the conventional moment method into several small matrices on the regions and enables one to solve easily the problem of scattering by very large objects. The accuracy of the method and the criteria for controlling computational errors are examined by its application to two-dimensional problems. Both parallel and perpendicular polarizations are assumed and the behaviour of the solutions for both smooth and singular field distributions on circular cylinders and prisms is studied. It is found that the surface distributions, such as induced currents, may be obtained more accurately by this method than the conventional moment method. The accuracy of the far fields, however, are generally of the same order for both methods. For convenience and brevity, the term PNM is used to refer to the method throughout this paper.

A new approach to the thin scatterer problem using the hybrid equations

Abstract: A new set of integral equations for electromagnetic scattering problems, the "hybrid" equations, is presented. The advantages of these equations for thin perfect conductors are discussed in comparison to the magnetic and electric field integral equations. Specific comparisons are made with the solution of the electric field integral equation for a finite hollow cylinder. It is demonstrated that the primary advantage of these equations is obtained by minimizing the coupling between component equations for the two surface currents.

Scattering of electromagnetic plane waves by a circular cylinder

Abstract: Numerical investigation of scattering electromagnetic plane waves by a circular conducting cylinder is considered. The results presented are 1) validity of asymptotic far-field expressions when it is applied to calculate near-field around the cylinder and 2) equicontours of amplitude and phase of total field around the cylinder.

New approach to studying electromagnetic mode coupling in inhomogeneous magnetized plasma

Abstract: Considering mode coupling as a consequence of the matching of boundary conditions at an infinitesimal discontinuity, a concept introduced by the same authors earlier, we derive explicit expressions for the coupling coefficients for electromagnetic waves propagating in a rather general direction in an inhomogeneous magnetized plasma. Some special cases of the theory are discussed.

Electromagnetic phenomena in impulse voltage measuring systems

Abstract: This paper deals with the theoretical and experimental studies of induced voltages in high voltage test circuits. These induced voltages are produced by electromagnetic radiation fields arising from travel - ling waves (current and charge) along the lead in the measuring system. These travelling waves are known to exist. The radiation fields can be calculated by applying distribution theory to the wave equations. All the relevant phenomena are presented and discussed for a measuring system in an indoor U.H.V. Laboratory. This contribution gives some explanation to questions of measurement phenomena and represents the first fundamental study of this topic.

Scattering of atoms by an electromagnetic field

Abstract: A theoretical analysis is made of the frequency dependence of the scattering of atoms and molecules by a standing electromagnetic wave.

Approximate analysis of electromagnetic scattering from corrugated conducting surfaces by surface impedance modeling

Abstract: Scattering from a corrugated conducting surface is analyzed by an approximate method based on Leontovich boundary condition. Comparison of results with those based on a rigorous technique justifies the use of such approximate methods for shallow gratings.

Fourier transforms in propagation and scattering problems

Abstract: Three-dimensional Fourier transforms are applied to electromagnetic wave propagation problems. After obtaining functions in transform space, inversion and contour integration yield a plane wave integral representation.

An approach to high-frequency scattering from smooth convex surfaces

Abstract: A method based on the Galerkin procedure in the transform domain that not only allows accurate solutions for both the farfield and the induced surface current be derived but also provides a convenient accuracy check for the solutions thus obtained is introduced. The total solution is constructed using only the geometrical optics method and a newly introduced synthetic aperture technique well suited for deriving efficient transform solutions for n -dimensional, smooth curved objects using ( n - 1 )-dimensional transforms. The need for the conventional creeping-wave contribution is obviated in this method.

Computer reconstruction of near-zone field from given far-zone data of two-dimensional objects

Abstract: Using a complete set of cylindrical vector wave functions, it is shown that accurate near-zone electromagnetic field can be easily reconstructed from given far-zone data of two-dimensional objects. The validity of this approach was shown by the comparison of the reconstructed results with those obtained according to the exact solution of a two-dimensional slit problem.

Electromagnetic radiation recoil

Abstract: Electromagnetic waves from a finite oscillating linear cohesive distribution of electric charge are investigated by a double-parameter approximation method applied to the Einstein-Maxwell equations of general relativity. In the metric representing the distribution, gravitational dipole terms (proportional to time) appear which indicate that the source recoils owing to the linear momentum carried away from the source by the waves.