A.T. de Hoop

A finite-element method for computing three-dimensional electromagnetic fields in inhomogeneous media

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.

A Computational Model of the Electromagnetic Heating of Biological Tissue with Application to Hyperthermic Cancer Therapy

To investigate the potentialities of hyperthermia as a cancer therapy, computer simulations have been performed. This simulation consists of two tuccessive steps. First, the heat generated in a distribution of biological tissue when irradiated by a source of electromagnetic radiation is computed. The mathematical tool for determining the disbution of generated heat is the domain-integral-equation technique. This technique enables us to determine in a body with arbitrary distribution of permittivity and conductivity the electromagnetic field due to prescribed sources. The integral equation is solved numerically by an iterative minimization of the integrated square error. From the computed distribution of generated heat, the temperature distribution follows by solving numerically the pertaining heat transfer problem. The relevant differential equation together with initial and boundary conditions is solved numerically using a finite-element technique in space and a finite-difference technique in time. Numerical results pertaining to the temperature distribution in a model of the human pelvis are presented.

New reciprocal circuit model for lossy waveguide structures based on the orthogonality of the eigenmodes

In this contribution, we present a new consistent equivalent transmission line model to describe the propagation along lossy hybrid waveguide structures. All existing consistent transmission line models are based on the assumption that the power propagated by the modes considered in the waveguide is the same as the power propagated in the model. In a lossy reciprocal waveguide, this leads to a nonreciprocal transmission line model because the modes are not power orthogonal. We start from the Lorentz orthogonality condition to construct a reciprocal transmission line model, even for lossy waveguides. For multiconductor waveguides, we discuss what we call RI-and RV-models, in analogy with the existing PI- and PV-models. We also present a generalisation of these RI- and RV-models to general waveguide structures. The theory is illustrated with a comparison of an RI- and PI-model for a lossy thick microstrip structure. >

The Pulsed-Field Multiport Antenna System Reciprocity Relation and Its Applications—A Time-Domain Approach

A novel time-domain approach to the derivation of the pulsed electromagnetic field multiport antenna system reciprocity theorem is presented. The theorem interrelates the field and system properties in two states: the transmitting state and the receiving state. General time-domain Thevenin (voltage-source, impedance-based) and Norton (electric-current source, admittance-based) type equivalent circuits are constructed for antenna systems whose local properties are described in terms of multiport Kirchhoff circuits. Applications to an indoor wireless communication performance analysis and the analysis of cosmic microwave background radiation measurement are briefly indicated. Numerical results are provided for the pulsed-field transfer between two wire loops, a configuration that is representative for the operation of wireless telecommunication systems and for the pulsed-field EM interference analysis in nano-electronic integrated circuit devices.

Finite formulation and domain-integrated field relations in electromagnetics - a synthesis

Complementary formulations of the integral type have established themselves as the most adequate approach to computational electromagnetics. This paper proposes a computational strategy that benefits from the advantages offered by the finite formulation of the electromagnetic (EM) field, employing integral field quantities and dual meshes, and by the domain-integrated field relations approach to EM field computation.

Three‐dimensional relativistic scattering of electromagnetic waves by an object in uniform translational motion

A general, relativistic formalism is developed for the three‐dimensional scattering of electromagnetic waves by an object that is in uniform translational motion with respect to a source of electromagnetic radiation. The theory applies to objects of arbitrary size, shape, and physical composition. In particular, the temporal frequency spectrum of the field detected by a receiver that is stationary with respect to the source is determined. Numerical results pertaining to the scattering of a time‐harmonic plane wave by a small, uniformly moving particle are presented.

Absorbing boundary conditions and perfectly matched layers - an analytic time-domain performance analysis

The time-domain performance of a number of absorbing boundary conditions invoked on the boundary of a domain of computation, as well as of a perfectly matched layer surrounding such a domain, is carried out for a test configuration for which analytic expressions for the relevant field quantities exist. The test configuration consists of a small loop antenna radiating into a homogeneous, isotropic half-space. On the planar boundary of this halfspace, either an absorbing boundary condition is invoked or a perfectly matched layer is started that is truncated at some finite depth of penetration. For a loop parallel to the boundary, closed-form analytic expressions for all field components of the spuriously reflected field are presented for all truncation conditions involved. A number of important features show up that might be masked in purely numerical implementations of the procedures under consideration.

Model Pulses for Performance Prediction of Digital Microelectronic Systems

Pulse-shape models are presented that furnish the tools for analyzing a number of aspects of the performance of microelectronic circuits. Model pulse shapes are provided and their properties are analyzed in detail. Applications that are covered include the replication of measured pulses that are of relevance for inter- and intra-chip interconnects and, concurrently, examples of passive circuits that generate them. The pulses are appropriate as input to time-domain electromagnetic simulation. They are also instrumental to microelectronic performance prediction protocols and measurement equipment-aspects that are of crucial importance to integrated circuit packaging.

Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwells equations numerically to be practically inapplicable. To overcome this difficulty, an approximate method is proposed that models the interaction of the layer with an incident electromagnetic field via a boundary condition that expresses the in-plane conduction and contrast electric polarization currents in terms of the exciting incident field by relating the jump in the tangential component of the magnetic field strength across the layer in terms of the (continuous) tangential component of the electric field strength in the layer. In the pertaining layer admittance coefficient, the integrated values of the conductance and the contrast permittivity profiles across the layer occur. The model is applied to the scattering of an incident plane wave with pulsed time signature by a layer of infinite extent. Expressions for pulse shapes of the scattered field are obtained. In them, the layer properties and the direction of incidence and polarization of the incident wave occur as parameters. Numerical results are presented for reflected and transmitted wave pulse shapes for some parameter values.

Reflection And Transmission of Electromagnetic Waves at a Rough Interface between Two Different Media

An iterative technique is developed to rigorously compute the electromagnetic wave reflection and transmission at a rough interface between two media. The method is based upon a wave-function expansion technique in which the electromagnetic field equations and the radiation condition are satisfied analytically, while the boundary conditions at the interface are satisfied numerically. The latter is accomplished by an iterative minimization of the integrated square error in the boundary conditions. In each step of the iteration, only Fourier transforms of the spectral and spatial variables occur. As starting value, the Sommerfeld-Weyl plane interface results can be employed.