Showing papers on "Computational electromagnetics published in 1985"
192 citations
TL;DR: In this article, a finite element method is presented that is particularly suited for the computer modeling of three-dimensional electromagnetic fields in inhomogeneous media and employs a new type of linear vectorial expansion functions.
Abstract: A finite-element method is presented that is particularly suited for the computer modeling of three-dimensional electromagnetic fields in inhomogeneous media. It employs a new type of linear vectorial expansion functions. Across an interface where the constitutive coefficients are discontinuous, they have the following properties: (1) the continuity of the tangential components of the electric and the magnetic field strengths is exactly preserved, (2) the normal component of the electric and the magnetic field strengths are allowed to jump and (3) the electric and the magnetic fluxes are continuous within the pertaining degree of approximation. The system of equations from which the expansion coefficients are obtained is generated by applying a Galerkin-type weighted-residual method. Numerical experiments are described that illustrate the efficiency of our elements, and the computational costs of the method.
153 citations
TL;DR: In this paper, a general computer program for low frequency scattering of electromagnetic fields by solid/hollow dielectric or conducting cylinders using the boundary element method (BEM) was developed for both transverse electric and magnetic cases.
Abstract: The computation of low frequency scattering of electromagnetic fields by solid/hollow dielectric or conducting cylinders using the boundary element method (BEM) is considered. A general computer program has been developed for both transverse electric and magnetic cases. Numerical examples are given for conducting circular cylinders, and solid and hollow dielectric cylinders. The computational accuracy is checked by comparing the results with the analytic solution or computing an error defined from the optical theorem. In addition some problems at an interior resonance of the scatterer are discussed. The method can be directly applied to more complicated geometries.
78 citations
32 citations
TL;DR: In this paper, an iterative method for solving the electromagnetic deposition inside lossy inhomogeneous dielectric bodies is proposed, which uses the conventional method of moments to formulate the problem in matrix form and solves it iteratively by the method of conjugate gradients.
Abstract: An iterative method is proposed for solving the electromagnetic deposition inside lossy inhomogeneous dielectric bodies. The technique uses the conventional method of moments to formulate the problem in matrix form. The resulting system of linear equations is solved iteratively by the method of conjugate gradients. The main advantage of the method is that the iterative procedure does not require the storage of any matrix, thus offering the possibility of solving larger problems compared to conventional inversion or Gaussian elimination schemes. Another important advantage is that monotonic convergence to a solution is ensured and accomplished within a fixed number of iterations, not exceeding the total number of basis functions, independently of the initial guess for the solution. Preliminary examples involving two-dimensional cylinders of fat and muscle are illustrated. The iterative method is expendable and applicable to the three-dimensional case.
22 citations
TL;DR: In this paper, a model for the magnetizing branch of the single phase transformer or iron core reactor is presented for the calculations of transients, where the diffusion of the electromagnetic field in the laminations of the core is considered.
Abstract: A model for the magnetizing branch of the single phase transformer or iron core reactor is presented for the calculations of transients. Eddy currents in the core and saturation are taken into account. The finite dimensional model results from the numerical approximation of the nonlinear partial differential equations representi the diffusion of the electromagnetic field in the laminations of the core [1]1. Second order central difference formulae, trapezoidal integrtiona (with damping, if desired ( 2D, and Newton's method are used for the numerical solution. A Norton/Thevenin equivalent for the core is developed to permit using it as a component in a complete transformer or reactor model.
20 citations
18 citations
TL;DR: The boundary element method (BEM) as discussed by the authors is a general formulation of the finite element method for analyzing two-dimensional electromagnetic fields, and has been shown to be a very powerful numerical method for solving electromagnetic field problems.
Abstract: The above paper has explained a general formulation of the boundary-element method (BEM) for analyzing two-dimensional electromagnetic fields, and has presented numerical examples for some boundary shapes to show that the BEM is a very powerful numerical method for solving electromagnetic field problems. It gives accurate results with far fewer nodes than the finite-element method, and can also treat field problems in unbounded regions without any additional complications.
17 citations
TL;DR: In this paper, the T -matrix was used to characterize the single scatterer response, the quasicrystalline approximation (QCA) and the correlation function.
Abstract: Electromagnetic wave propagation in a medium containing a random distribution of aligned, pair-correlated nonspherical scatterers is studied using the T -matrix to characterize the single scatterer response, the quasicrystalline approximation (QCA) and the correlation function. The resulting dispersion equation for the average medium is numerically solved as a function of frequency and the direction of propagation. Numerical results are presented for the attenuation of electromagnetic waves versus frequency, concentration, and direction of propagation.
12 citations
TL;DR: In this article, the self-patch integrals that arise in the integral equations of electromagnetic scattering are evaluated analytically for general orthogonal coordinate systems to first order in the linear size of the patch.
Abstract: The self-patch integrals that arise in the integral equations of electromagnetic scattering are evaluated analytically for general orthogonal coordinate systems to first order in the linear size of the patch. There are terms that contain spatial derivatives of the surface fields, and these terms may not be negligible. Although the formulas are derived for transient waves, the same integrals appear for monochromatic waves.
TL;DR: In this article, a modal theory for the study of the diffraction of electromagnetic plane waves by bigratings of hemispherical cavities hollowed in a plane surface of perfectly conducting material is described.
Abstract: A rigorous modal theory is described for the study of the diffraction of electromagnetic plane waves by bigratings of hemispherical cavities hollowed in a plane surface of perfectly conducting material. The theoretical study is realized for any incidence and direction of polarization and our first numerical results concern only the simpler case of normal incidence. Under this condition the efficiency curves \epsilon_{pq} of the various real diffracted orders are studied. We find that the cavity depth R has an important influence on the shape of the curves. In particular, the
01 Dec 1985
TL;DR: In this paper, two distinct approaches for creating symmetries are examined and applied to a variety of typical electromagnetic scattering problems, in order to evaluate their performance in practice, and both procedures are applied to several scattering problems.
Abstract: : The numerical solution of electromagnetic scattering problems involves approximating an exact equation by a finite-dimensional matrix equation. The use of an iterative algorithm to solve the matrix equation sometimes results in a considerable savings in computer memory requirements. For a fixed amount of computer memory, this approach permits the analysis of scatterers that are an order of magnitude larger electrically. Iterative algorithms of the conjugate gradient class are examined and applied to a variety of typical electromagnetic scattering problems, in order to evaluate their performance in practice. Depending on the geometry of the scatterer under consideration, it may be possible to build symmetries into the matrix representation and effect the necessary storage reduction. Two distinct approaches for creating these symmetries are examined. An alternate procedure, which requires some of the matrix elements to be regenerated as needed by the iterative algorithm in use, does not relay on symmetries and is applicable to a larger set of geometries. Both procedures are applied to several scattering problems. Execution time comparisons show that the approaches based on symmetries are the most efficient, and that both procedures can be superior to noniterative techniques for large scatterers. (rh)
TL;DR: In this article, the use of hybrid solutions for integral equation (IE) formulations in electromagnetics is illustrated at frequencies where a perfectly conducting scatterer exhibits internal resonances.
Abstract: The use of hybrid solutions for integral equation (IE) formulations in electromagnetics is illustrated at frequencies where a perfectly conducting scatterer exhibits internal resonances. Hybrid solutions, incorporating the Fock theory and physical optics Ansatzes, and the Galerkin representation, are compared with the method of moments (MM) solutions of the electric, magnetic, and combined field formulations at such frequencies. Numerical results are presented for spheres and a right circular cylinder.
TL;DR: In this paper, the electromagnetic field equations with electromagnetic substratum flow are strictly covariant against Galilei transformations, and boundary conditions are derived for the electrodynamic fields in presence of electromagnetic substrate flow.
Abstract: Based on the Galilean relativity principle and Maxwell's equations, electromagnetic field equations are derived for inertial frames, in which the substratum of the electromagnetic waves flows with arbitrary velocity | w | < c (velocity of light). It is demonstrated that the electromagnetic field equations with electromagnetic substratum flow are strictly covariant against Galilei transformations. Wave equations, conservation and invariance theorems, and boundary conditions are derived for the electrodynamic fields in presence of electromagnetic substratum flow. Initial-boundary-value problems are solved for electromagnetic signal propagation and induction in the substratum by an integral equation method. Physical effects for the measurement of the velocity field of the electromagnetic substratum are discussed. Maxwell's conception that his equations refer to a frame of reference with resting electromagnetic substratum is confirmed, and it is shown that Maxwell's equations are also applicable to inertial frames with small substratum velocities, | w | ≪ c.
TL;DR: In this paper, the integrals over patches that are close to the self-patch are calculated by expanding the factors in the integrand in power series, up to first order in the linear size of the patch.
Abstract: The integrals over patches that are close to the self-patch are calculated by expanding the factors in the integrand in power series. The values are computed analytically up to first order in the linear size of the patch. This procedure applies to patches for which the distance between the centers is of the same order of magnitude as the size of the patch. The same formulas are useful in steady-state scattering problems.
17 Jun 1985
01 Feb 1985
TL;DR: In this paper, the field coupling from a normally electromagnetic pulse (EMP) incident plane wave through a circular aperture within a thin planar surface has been estimated by estimating field coupling.
Abstract: Equations and curves are given for estimating field coupling from a normally electromagnetic pulse (EMP) incident plane wave through a circular aperture within a thin planar surface.
TL;DR: In this article, a volume integral method is used with the finite element technique as a differential numerical approach to predict the levitating force acting on a E core plate levitator and the results were in good agreement with the experimental measured values.
Abstract: The solution of the electromagnetic field in any electromagnetic device is best appreciated if expressed in terms of the terminal characteristics of the device, namely forces. In this paper expressions for force calculations are derived from the numerical field solutions in terms of \bar{T} -the electric vector potential and Omega(Ω)-the magnetic scalar potential. The volume integral method is used with the finite element technique as a differential numerical approach. The technique was tested to predict the levitating force acting on a E core plate levitator and the results were in good agreement with the experimental measured values.
TL;DR: In this paper, the electromagnetic fields due to dipole antennas in a bounded conducting medium modeling the sea have been formulated in integral forms and solved with the following techniques: the brute-force numericalintegration method; the modal approach by finding the residues for the integrals; the image-source approach by using the steepest descent method; and the hybrid technique with the combination of the two latter approaches.
Abstract: The electromagnetic fields due to dipole antennas in a bounded conducting medium modeling the sea have been formulated in integral forms and solved with the following techniques: the brute-force numerical-integration method; the modal approach by finding the residues for the integrals; the image-source approach by using the steepest descent method; and the hybrid technique with the combination of the two latter approaches. Quasi-static field approximations can be applied when the loss tangent of the conducting media is very large and the observation distances are small compared to the free-space wavelength. For very long wavelengths or for sufficiently thin layer thickness the normal mode approach is more useful, for shorter wavelength or for thicker layers, the image method is more efficient and accurate, whereas in the intermediate range the hybrid method then becomes necessary. We have also derived closed-form expressions for the fields at zero frequency in an image series expansion form and used Poisson's series to convert this image series into a mode series for the case when both the receiver and transmitter are located at the interface.
TL;DR: In this paper, it was shown that the boundary value problem of perfect reflection becomes the scattering problem if the boundary values specified are the values of the known incident field at the surface of the scattering body.
TL;DR: Electromagnetic theory is presented by expanding upon ideas that electrical engineering students already possess, and the equivalent network concept, well known for lumped circuits, is generalized to electromagnetic fields in free space.
Abstract: In this paper, electromagnetic theory is presented by expanding upon ideas that electrical engineering students already possess. The equivalent network concept, well known for lumped circuits (ordinary differential equations), is generalized to electromagnetic fields in free space (partial differential equations). The network, rigorously equivalent to Maxwell's equations, is suitable for all problems in free space. One illustrative antenna problem is presented and its relevance to lumped network calculations is also shown.
TL;DR: Using the relativistic BS wave function of the (0-1/2) electromagnetic bound system, the differential cross-section for the scattering of a lepton by a (0 − 1/2)-bound system is calculated in this paper.
Abstract: Using the relativistic BS wave function of the (0-1/2) electromagnetic bound system, the differential cross-section for the scattering of a lepton by a (0-1/2) bound system is calculated. The analytical expressions of the electromagnetic form factors of the bound system are also obtained.
01 Jan 1985
TL;DR: In this article, the authors considered isotropic bodies and determined the spatial distribution of the electromagnetic parameters, where µ is the magnetic permeability and σ the electrical conductivity, given an excitation source, known to us, and a scattered field, which we can measure (albeit somewhat inaccurately, because of noise and the like).
Abstract: The problem that we are trying to solve is: Given an excitation source, which is known to us, and a scattered field, which we can measure (albeit somewhat inaccurately, because of noise and the like), determine the spatial distribution of the electromagnetic parameters, µ, and σ, where µ is the magnetic permeability and σ the electrical conductivity. This allows us to determine the structure of a body in free space, or the structure of an internal flaw (or anomalous region) within a given body whose properties, such as size, shape and electrical parameters, are known to us. Throughout this paper we will consider only isotropic bodies, which means that the conductivity and magnetic permeability are scalar functions of positions.
17 Jun 1985