Femke Olyslager

A Multiplicative Calderon Preconditioner for the Electric Field Integral Equation

In this paper, a new technique for preconditioning electric field integral equations (EFIEs) by leveraging Calderon identities is presented. In contrast to all previous Calderon preconditioners, the proposed preconditioner is purely multiplicative in nature, applicable to open and closed structures, straightforward to implement, and easily interfaced with existing method of moments (MoM) code. Numerical results demonstrate that the MoM EFIE system obtained using the proposed preconditioning converges rapidly, independently of the discretization density.

Efficient mode-matching analysis of discontinuities in finite planar substrates using perfectly matched layers

A new method to determine the reflection of substrate modes in finite substrate planar circuits is proposed. The perfectly matched layer (PML) concept is used to transform the open problem into a closed one. The discrete set of substrate, evanescent, and Berenger modes of the resulting anisotropic waveguides are then used in a mode-matching scheme to deduce the scattering coefficients of the substrate modes for oblique incidence on the edge of the substrate. We show results for single- and double-layered substrates and compare with finite-difference time-domain (FDTD) results. The combined perfectly matched layer (PML) mode-matching technique turns out to be very efficient.

Numerical and experimental study of the shielding effectiveness of a metallic enclosure

This paper presents a detailed study of the shielding effectivity properties of metal enclosures. Measurements in anechoic chambers are compared to full-wave electromagnetic simulations. The study is not limited to the frequency range below the first resonance frequency. Different aspects are investigated such as the influence of the size, position and number of apertures, and the effect of the presence of metal plates and of absorbing materials. Where possible, the specific behavior of the shielding effectivity is explained theoretically and existing simple design rules are assessed.

Analysis of cylindrical waveguide discontinuities using vectorial eigenmodes and perfectly matched layers

In this paper, we analyze the scattering at discontinuities in cylindrical waveguides, starting from a vectorial eigenmode expansion and by introducing perfectly matched layer (PML) boundary conditions. The structure under study is enclosed in a metal cylinder to discretize the radiative mode spectrum, while the coating of this cylinder with PML vastly reduces the influence of parasitic reflections at the metal. This allows for a model that is both faster and more accurate than previous models.

Rigorous analysis of the propagation characteristics of general lossless and lossy multiconductor transmission lines in multilayered media

The frequency-dependent propagation characteristics of lossless and lossy open coupled polygonal conductor transmission lines in a multilayered medium are determined based on a rigorous full-wave analysis. A boundary integral equation technique is used in conjunction with the method of moments. Losses in conductors and layers are included in an exact way without making use of a perturbation approach. Dispersion curves for the complex propagation constants and impedances are presented for a number of relevant examples and, where possible, compared with published data. >

An Asynchronous Parallel MLFMA for Scattering at Multiple Dielectric Objects

In this paper, a new strategy for the parallelization of the multilevel fast multipole algorithm (MLFMA) on distributed memory computers is presented. By using an asynchronous implementation of the parallel MLFMA, an efficient parallelization scheme is obtained when multiple dielectric objects are involved in the simulation. Furthermore, a better spreading of the communication through time is obtained, avoiding both communication in bursts and synchronization at each MLFMA level. This proves especially beneficial when slower interconnection networks are used.

A Nondirective Plane Wave MLFMA Stable at Low Frequencies

A novel method, called the nondirective stable plane wave multilevel fast multipole algorithm (NSPWMLFMA), is presented to evaluate the low-frequency (LF) interactions that cannot be handled by the multilevel fast multipole algorithm (MLFMA). It is well known that the MLFMA cannot be used for LF interactions, since it suffers from numerical instability. Contrary to current techniques, the proposed technique is not based on the spectral representation of the Green function. Instead the addition theorem of the MLFMA is manipulated into a form that allows numerically stable translations along the z axis. The translation operator for these translations is derived in closed form. A QR-based method is devised to allow stable translations in all the other directions. Interpolations and anterpolations are also provided, allowing a full multilevel algorithm. Since the NSPWMLFMA is based on the same mathematical foundations as the MLFMA, it requires limited adaptations to existing MLFMA codes. The fact that a QR is needed limits this algorithm to LF interactions. However, a coupling with the MLFMA is straightforward, allowing the easy construction of a broadband algorithm. The DC limit of the algorithm is also presented and it is shown that the algorithm remains valid for static problems. Finally, it is shown that the error introduced in the different steps of the algorithm is controllable, and a single-level vectorial version of the algorithm is applied to a generic scattering application to demonstrate its validity.

Time Domain CalderÓn Identities and Their Application to the Integral Equation Analysis of Scattering by PEC Objects Part II: Stability

Novel time domain integral equations for analyzing scattering from perfect electrically conducting objects are presented. They are free from DC and resonant instabilities plaguing standard electric field integral equation. The new equations are obtained using operator manipulations originating from the Calderon identities. Theoretical motivations leading to the construction of the new equations are explored and numerical results confirming their theoretically predicted behavior are presented.

Modeling differential via holes

In this paper, we present a method to characterize differential via holes in printed circuit boards in a both fast and accurate way. The via hole is modeled as a cascade of capacitances and inductances. We use FASTCAP to compute the values of the capacitances, and a closed form formula to obtain the inductance values. The numerical predictions are compared with experimental data.

A CalderÓn Multiplicative Preconditioner for the Combined Field Integral Equation

A Calderon multiplicative preconditioner (CMP) for the combined field integral equation (CFIE) is developed. Just like with previously proposed Calderon-preconditioned CFIEs, a localization procedure is employed to ensure that the equation is resonance-free. The iterative solution of the linear system of equations obtained via the CMP-based discretization of the CFIE converges rapidly regardless of the discretization density and the frequency of excitation.