J. van Tonder

Fast multipole solution of metallic and dielectric scattering problems in FEKO

Complex scattering problems are solved with the multilevel fast multipole method (MLFMM). Geometries include metallic structures (wires and surfaces) as well as dielectric bodies (volume and surface equivalence principle). Validation and application examples show the large savings in memory and run-time of the MLFMM as compared to the standard method of moments (MoM). Limitations regarding dielectric bodies are addressed, which are encountered when attempting to model highly lossy dielectric bodies with a high permittivity.

Bandwidth improvement of circularly polarised arrays using sequential rotation

The authors report on the sequential rotation technique to minimize the severe bandwidth limitations associated with circularly polarized patch antennas. The technique is applicable to all circularly polarized antenna rays. The theory and experimental results are discussed as applied to a patch array. It is confirmed that remarkable antenna bandwidth improvements may be obtained through the use of sequential rotation.<<ETX>>

A study of an Archimedes spiral antenna

The gain, radiation pattern, and input impedance of a planar two-arm Archimedes spiral [Bawer and Wolfe, 1960] fed by a Marchand balun [Cloete, 1980] and designed for 2 to 6 GHz are presented. The self-complementary spiral pattern was etched onto a thin copper clad dielectric substrate and mounted 30 mm above a circular conducting ground plane with diameter 400 mm or 800 mm using a polystyrene foam spacer with open sides. The spiral was not backed by a closed cavity with conducting side walls. The paper tests a thin wire moment method code, developed for the analysis of planar spiral antennas on dielectric substrates, by comparing numerical predictions with measurements made in a 10/spl times/5/spl times/5 m anechoic chamber using an HP 8510C network analyzer. The formulation used is that of Mosig and Gardiol [1985]. For the purpose of the numerical analysis the two-arm spiral was assumed to be mounted above an infinite, perfectly conducting ground plane and to radiate into semi-infinite free space. The results of the code were also compared with numerical results published by Nakano et al. [1988].<<ETX>>

Challenges regarding the commercial implementation of the parallel MLFMM in FEKO

Real-world electromagnetic problems are becoming increasingly complex, so that the natural growth in computer power over time is not sufficient any more to keep pace with these requirements. Therefore, in addition to traditional solver techniques like FDTD, FEM or MoM also so-called fast algorithms find their way into commercial EM solver packages. In this paper, some aspects regarding the implementation and parallelization of the multilevel fast multipole method in the commercial field solver FEKO are discussed

Advanced EMC modeling by means of a parallel MLFMM and coupling with network theory

The application of a parallelized multilevel fast multipole method (MLFMM) is described and illustrated through examples for the solution of large scale and complex EMC problems. Furthermore, to reduce the modeling complexity of such EMC problems, we propose a combination of field with network theory to split large problems into smaller sub-problems which can be analyzed individually and then again assembled together by means of network theory.

Tailoring FEKO for microwave problems

In this article we have presented some of the more recent modeling options available in FEKO (waveguide ports, combination with FEM, dielectric GO, PBCs, coupling with networks) that are specifically useful to the microwave engineer. In addition to presenting some of the theory, we focused on examples to show the application of each method and discussed their advantages. The examples were kept intentionally simple such that the relevant advantages can easily be highlighted.

Method of moments accelerations and extensions in FEKO

This paper introduces several extensions and accelerations to the Method of Moments (MoM) formulation in the computer code FEKO, which all aim in solving large problems faster or using less memory.

Overview of Recent Extensions in FEKO with Regard to the MLFMM and Cable Coupling

This paper describes two recent extensions of the electromagnetics computer code FEKO. The first extension is the hybridisation of the various techniques available in FEKO with transmission line theory in order to model coupling of electromagnetic fields into shielded cables. Secondly, some improvements for the MLFMM (Multilevel Fast Multilevel Method) will be presented concerning the parallel preconditioning using SPAI (Sparse Approximate Inverse) and regarding the fast near-field calculations.

Combining domain decomposition solution techniques with higher order hierarchical basis functions

This paper considers the efficient numerical analysis of large and complex electromagnetic structures by using domain decomposition techniques such as the Numerical Greens Function (NGF) [1] and the Domain Greens Function Method (DGFM) [2] in connection with hierarchical higher order basis functions [3, 4]. Both the NGF and DGFM methods are applicable to problems that can be subdivided into distinct computational regions. Previously low order Rao-Wilton-Glisson (RWG) type basis functions [5] have been used to discretise each of the subdomains. In the current approach this has been extended to use hierarchical higher order basis functions that allow for larger and more complex geometries to be considered. The work presented in this article will discuss the formulation of the methods and the results of applying the solution techniques to various examples consisting of large and complex electromagnetic problems.

New developments in FEKO Suite 6.0 –: Aperture modeling, SPICE Sub-Circuit integration, Shielding Extensions, GPU computing

This paper introduces some of the latest extensions and improvements to the field computation package FEKO: Support for aperture modeling in the planar multilayer Greens function using magnetic surface currents, the integration of SPICE subcircuits in combination with electromagnetic models, accurate shielding computations in the modeling of geometrically thin lossy layers and acceleration by GPUs. These topics are presented and discussed along with validation and application examples.