Showing papers on "Computational electromagnetics published in 1984"
TL;DR: In this article, a volume integral equation is formulated and solved by using the method of moments for calculating the electromagnetic scattering from and internal field distribution of arbitrarily shaped, inhomogeneous, dielectric bodies.
Abstract: A method for calculating the electromagnetic scattering from and internal field distribution of arbitrarily shaped, inhomogeneous, dielectric bodies is presented. A volume integral equation is formulated and solved by using the method of moments. Tetrahedral volume elements are used to model a scattering body in which the electrical parameters are assumed constant in each tetrahedron. Special basis functions are defined within the tetrahedral volume elements to insure that the normal electric field satisfies the correct jump condition at interfaces between different dielectric media. An approximate Galerkin testing procedure is used, with special care taken to correctly treat the derivatives in the scalar potential term. Calculated internal field distributions and scattering cross sections of dielectric spheres and rods are compared to and found in agreement with other calculations. The accuracy of the fields calculated by using the tetrahedral cell method is found to be comparable to that of cubical cell methods presently used for modeling arbitrarily shaped bodies, while the modeling flexibility is considerably greater.
887 citations
TL;DR: In this article, a matrix equation is constructed using the electric tensor Green's function appropriate to a layered earth, and it is solved for the vector current in each cell, and scattered fields are found by integrating electric and magnetic tensor green's functions over the scattering currents.
Abstract: We have developed an algorithm based on the method of integral equations to simulate the electromagnetic responses of three‐dimensional bodies in layered earths. The inhomogeneities are replaced by an equivalent current distribution which is approximated by pulse basis functions. A matrix equation is constructed using the electric tensor Green’s function appropriate to a layered earth, and it is solved for the vector current in each cell. Subsequently, scattered fields are found by integrating electric and magnetic tensor Green’s functions over the scattering currents. Efficient evaluation of the tensor Green’s functions is a major consideration in reducing computation time. We find that tabulation and interpolation of the six electric and five magnetic Hankel transforms defining the secondary Green’s functions is preferable to any direct Hankel transform calculation using linear filters. A comparison of responses over elongate three‐dimensional (3-D) bodies with responses over two‐dimensional (2-D) bodie...
250 citations
TL;DR: In this article, the electromagnetic scattering from partially or totally penetrable bodies of revolution (BOR) is formulated in terms of coupled Fredholm integral equations, solved by the method of moments (MM).
Abstract: The electromagnetic scattering from partially or totally penetrable bodies of revolution (BOR) is formulated in terms of coupled Fredholm integral equations, solved by the method of moments (MM). The scatterers can have axial inhomogeneities, formed by dissimilar dielectric materials. The case of conducting bodies with axially discontinuous coatings is also treated. The penetrable regions can be lossy, characterized by complex permeability and permittivity. Boundary conditions are rigorously treated everywhere including the intersection of the various regions. The solutions are expressed in terms of combinations of two special matrices arising from the Galerkin technique. These solutions are implemented numerically for a class of generic axially inhomogeneous BOR scatterers. Numerical results given for various conducting/dielectric cylinder combinations using this formulation are compared with experimental data. For special cases where comparisons are possible, the present analysis replicates the results of the Mie theory.
130 citations
TL;DR: In this article, a single surface integral equation for problems involving electromagnetic scattering from homogeneous dielectric bodies illuminated by time-harmonic sources is developed via the equivalence principle.
Abstract: A single surface integral equation for problems involving electromagnetic scattering from homogeneous dielectric bodies illuminated by time-harmonic sources is developed via the equivalence principle. The equation is formulated in terms of an equivalent electric current defined at the body surface. When allowed to radiate in a homogeneous medium having the material parameters of the exterior medium of the original problem, the electric current solution to the integral equation produces the correct scattered electric and magnetic fields external to the body.
114 citations
TL;DR: In this article, the nonlinear propagation of an electromagnetic wave along an external magnetic field in a uniform plasma is reconsidered in order to include the combined effects of the relativistic mass and ponderomotive-force nonlinearities.
Abstract: The nonlinear propagation of an electromagnetic wave along an external magnetic field in a uniform plasma is reconsidered in order to include the combined effects of the relativistic-mass and ponderomotive-force nonlinearities. The results of previous works on this subject are improved significantly.
89 citations
TL;DR: In this article, a new technique for interfacing electrical machine models with electromagnetic transients programs is presented, which does not require a Thevenin equivalent circuit of the electrical network.
Abstract: A new technique is presented for interfacing electrical machine models with electromagnetic transients programs. The machine models with their associated controls, loads or turbines can be assembled as subroutines by the user and interfaced to the electrical network or other machine models directly. The machine models employ the standard state variable equations and may use any integration technique for solution. The technique does not require a Thevenin equivalent circuit of the electrical network.
62 citations
TL;DR: In this paper, two stability criteria for discretization of the source type integrals are formulated to guarantee that the instability can be controlled by reducing the discretisation step, if they are met, and analyzed the solution of two two-dimensional electromagnetic scattering problems.
Abstract: The transient scattering of two-dimensional electromagnetic fields by an obstacle of finite extent is investigated with the aid of the time domain integral equation technique. In solving such equations with the marching-on-in-time method, numerical instabilities form a major problem. These instabilities can be attributed to errors in the discretization of the source type integrals that occur in the equations. In this paper, we formulate two so-called stability criteria for such a discretization that, if they are met, guarantee that the instability can be controlled by reducing the discretization step. With the aid of these criteria, we analyze the solution of two two-dimensional electromagnetic scattering problems, namely the scattering of a pulsed plane wave by a perfectly conducting and an inhomogeneous, lossy dielectric cylinder. Numerical results are presented and discussed.
54 citations
TL;DR: Group theory is used to factorize systems of equations for the expansion coefficients of the electromagnetic field scattered by a cluster of spheres as discussed by the authors, and simple but significant examples are given in this paper.
Abstract: Group theory is used to factorize systems of equations for the expansion coefficients of the electromagnetic field scattered by a cluster of spheres. Simple but significant examples are given.
42 citations
TL;DR: In this paper, a method of conjugate gradient is presented for the solution of operator equations arising in electromagnetics, and the particular problem to which the method has been applied is the electromagnetic scattering from arbitrary oriented wire antennas.
Abstract: In this paper the method of conjugate gradient is presented for the solution of operator equations arising in electromagnetics. The particular problem to which the conjugate gradient method has been applied is the electromagnetic scattering from arbitrary oriented wire antennas. With this iterative technique, it is possible to solve electromagnetic problems involving electrically large structures without storing any matrices as is conventionally done in the method of moments. The basic difference between the proposed method and the matrix methods (Rayleigh-Ritz, Galerkin's, method of moments) for the same expansion functions is that for the iterative technique we are solving a least squares problem. Hence, as the order of the approximation is increased, the proposed technique guarantees a monotonic convergence for the residuals AI-Y, whereas matrix methods, in general, do not yield monotonic convergence. The conjugate gradient method converges for any initial guess; however, a good one may significantly lower the computation time. Also, explicit error formulas are given for the rate of convergence. Numerical results are presented for electromagnetic scattering from arbitrary oriented thin-wire antennas.
42 citations
TL;DR: In this paper, simple closed-form expressions for the resonant frequency and electromagnetic field distribution for various modes of the open and closed-ring microstrip resonators are derived by utilizing the perturbation analysis of the equivalent curved waveguide model.
Abstract: Simple closed-form expressions for the resonant frequency and electromagnetic field distribution for various modes of the open- and closed-ring microstrip resonators are derived by utilizing the perturbation analysis of the equivalent curved waveguide model. These results are shown to be in good agreement with the exactly computed values obtained by the solution of the eigenvalue equation for the equivalent waveguide model and the experimental data. The effect of gap capacitance on the eigenvalues of the open-ring resonator is also examined.
37 citations
TL;DR: Using the surface equivalence theorem, four coupled integral equations for electromagnetic scattering by a thin material plate were developed in this article, and these equations can be written as open surface integral equations.
Abstract: Using the surface equivalence theorem, four coupled integral equations are developed for electromagnetic scattering by a thin material plate. Using symmetry properties, it is shown that these equations can be written as open surface integral equations. Surface impedance relationships are obtained and used to eliminate two of the four integral equations. The remaining two equations are solved using the method of moments (MM). Numerical results for penetrable and impenetrable material plates are in reasonable agreement with measurements.
TL;DR: The infinitesimal scaling technique, which enables the coefficient matrix required for assembling the contribution of an extended element into the global functional to be determined without explicit knowledge of internal basis functions, is used.
Abstract: The ability to treat extended uniform linear regions (particularly unbounded external regions) as single elements is a desirable addition to electromagnetic finite element techniques. The use of extended elements requires basis functions that are better approximations to the solutions of the underlying partial differential equations than the conventional polynomial basis functions. This problem can be circumvented by means of the infinitesimal scaling technique, which enables the coefficient matrix required for assembling the contribution of an extended element into the global functional to be determined without explicit knowledge of internal basis functions.
TL;DR: In this paper, a new method is presented that rapidly evaluates the many Green's tensor integrals encountered in three-dimensional electromagnetic modeling using an integral equation, where efficient and accurate computation of Hankel transforms are obtained by related and lagged convolutions.
Abstract: A new method is presented that rapidly evaluates the many Green’s tensor integrals encountered in three‐dimensional electromagnetic modeling using an integral equation. Application of a fast Hankel transform (FHT) algorithm (Anderson, 1982) is the basis for the new solution, where efficient and accurate computation of Hankel transforms are obtained by related and lagged convolutions (linear digital filtering). The FHT algorithm is briefly reviewed and compared to earlier convolution algorithms written by the author. The homogeneous and layered half‐space cases for the Green’s tensor integrals are presented in a form so that the FHT can be easily applied in practice. Computer timing runs comparing the FHT to conventional direct convolution methods are discussed, where the FHT’s performance was about 6 times faster for a homogeneous half‐space, and about 108 times faster for a five‐layer half‐space. Subsequent interpolation after the FHT is called is required to compute specific values of the tensor integra...
TL;DR: In this paper, a technique for the electromagnetic modeling of arbitrary perfectly conducting structures using polygonal plates is described, illustrated by three realistic examples, and the method is shown to be effective in the case of a perfectly conducting structure.
Abstract: A technique for the electromagnetic modeling of arbitrary perfectly conducting structures using polygonal plates is described. The method is illustrated by three realistic examples.
01 Jan 1984
TL;DR: In this paper, a scalar transmission line matrix simulating the propagation of a Hertzian potential in three-dimensional space is presented, which is numerically more efficient than the traditional TLM method.
Abstract: This paper presents novel scalar transmission line matrix simulating the propagation of a Hertzian potential in three-dimensional space. The new method is numerically more efficient than the traditional TLM method.
TL;DR: In this paper, the transmembrane potential difference induced by an impressed electromagnetic field in a spherical homogeneous cell with nonlinear membrane is obtained by using the Volterra-series formalism.
Abstract: The transmembrane potential difference induced by an impressed electromagnetic field in a spherical homogeneous cell with nonlinear membrane is obtained by using the Volterra-series formalism. Some possible generalizations are suggested, and computed results are discussed.
TL;DR: In this article, a fast Hankel transform (FHT) algorithm is proposed to evaluate the many Green's tensor integrals encountered in three-dimensional electromagnetic modeling using an integral equation.
Abstract: A new method is presented that rapidly evaluates the many Green's tensor integrals encountered in three-dimensional electromagnetic modeling using an integral equation. Application of a fast Hankel transform (FHT) algorithm (Anderson 1982) is the basis for the new solution, where efficient and accurate computation of Hankel transforms are obtained by related and lagged convolutions (linear digital filtering). The FHT algorithm is briefly reviewed and compared to earlier convolution algorithms written by the author. The homogeneous and layered half-space cases for the Green's tensor integrals are presented in a form so that the FHT can be easily applied in practice. Computer timing runs comparing the FHT to conventional direct convolution methods are discussed, where the FHT's performance was about 6 times faster for a homogeneous half-space, and about 108 times faster for a five-layer half-space. Subsequent interpolation after the FHT is called is required to compute specific values of the tensor integrals at selected transform arguments; however, due to the relatively small lagged convolution interval used (same as the digital filter's), a simple and fast interpolation is sufficient (e.g. by cubic splines).
TL;DR: In this paper, an inverse electromagnetic scattering technique was investigated, which uses the polarization characteristics of the scattered wave to form an image of the convex portions of the scattering body, and a differential equation relating these local measurements to the surface has been established.
Abstract: Investigated is an inverse electromagnetic scattering technique that uses the polarization characteristics of the scattered wave to form an image of the convex portions of the scattering body. The depolarization of an electromagnetic signal by a scattering surface is related to thee local principal curvatures through the measurable leading edge of the impulse response. A classic problem in differential geometry (Christoffel–Hurwitz) deals with the reconstruction of such a surface from a knowledge of this kind of information, and a differential equation relating these local measurements to the surface has long been established. A Fortran code employing a “finite-element” solution to this equation has been constructed and tested on synthetic data.
TL;DR: In this article, the authors used summary representation as the basis for a new hybrid scheme to solve the two-dimensional Helmholtz equation for electromagnetic modeling, and showed that substantial computing time and storage savings can be made.
Abstract: The method of summary representation developed by G. N. Polozhii is a quasi-analytical method for solving self-adjoint, finite-difference boundary value problems expressed on regular meshes. In principle, the method should allow considerable savings in computing time as well as improved accuracy when compared to commonly used finite-difference schemes. We have used summary representation as the basis for a new hybrid scheme to solve the two-dimensional Helmholtz equation for electromagnetic modeling. The theory behind this hybrid scheme is presented. Preliminary results for the two-dimensional problem show that substantial computing time and storage savings can be made.
25 Jun 1984
TL;DR: In this article, the Numerical Electromagnetics Code (NEC) is applied to frequency-domain modeling of HV systems, taking into account not only the geometry of each individual piece of apparatus but also the effect of coupling between different components of the HV system.
Abstract: The Numerical Electromagnetics Code (NEC) is applied to frequency-domain modelling of HV systems. This application results in an improved model in comparison with the lumped-distributed approach. The new model not only takes into account the geometry of each individual piece of apparatus but also includes the effect of coupling between different components of the HV system. The model additionally incorporates the effects of parasitic elements such as the inductance of a resistive divider or ground plane losses. The limitations and capabilities of the user-oriented implementation of the NEC in the analysis of HV systems are presented by modelling a few of the following problems: the electromagnetic interference (EMI) generated by discharging an RV impulse generator, the transfer function of a resistive divider, and the electromagnetic (EM) field distribution of a resistive divider.
TL;DR: In this article, the transient response of imperfectly conducting and permeable spheroidal objects is determined using the impedance boundary conditions, which relates conveniently the solution to the object's physical parameters and simplifies the computations.
Abstract: The transient response of imperfectly conducting and permeable spheroidal objects is determined using the impedance boundary conditions. Since the impedance boundary conditions are not known in the time domain, the frequency domain analysis is used to formulate the problem. The use of impedance boundary conditions relates conveniently the solution to the object's physical parameters and simplifies the computations. For highly conducting objects a simplified method is used to determine numerically the frequency domain data, which utilizes the numerical code for perfectly conducting objects. The excitation is assumed to be due to a periodic pulse train and generated by a small circular loop antenna. The procedure for the computation of the transient response, at very low excitation frequencies, is presented and the response forms for different object parameters and orientations are computed.
25 Jun 1984
CGG1
25 Jun 1984
TL;DR: In this article, the authors proposed a new condition, valid everywhere in air and which can be applied for both E and H polarization, that only one line is added to the grid discretizing the ground.
Abstract: To simulate the propagation of an electromagnetic plane wave in an inhomogeneous ground, the finite difference approach can be used. One of the main problems in using this method is imposing the boundary conditions near the ground surface, especially at high frequency. Indeed, for the E polarization, the upper top of the numerical grid must be sufficiently far away from the air-ground interface in order to neglect the field due to the heterogeneities and the discretization of the atmosphere is necessary. For magneto-telluric modeling, improved boundary conditions have already been proposed. This paper deals with a new condition, valid everywhere in air and which can be applied for E and H polarization. Thus even at high frequency, as for radar applications, only one line is added to the grid discretizing the ground.
25 Jun 1984