Marianne Bingle

Scattering and absorption by thin metal wires in rectangular waveguide-FDTD simulation and physical experiments

The high-frequency internal impedance model of a round ohmic conductor is incorporated into the subcell thin-wire formulation of the finite-difference time-domain method to model the microwave properties of metal wires. For magnetic metals, such as steel, an effective conductivity is introduced to account for the increase in ohmic loss due to the high-frequency permeability. Physical experiments with half-wave resonant copper- and steel-wire inclusions, supported by a dielectric slab in a standard S-band rectangular waveguide, support the formulation.

The role of chirality and resonance in synthetic microwave absorbers.

Summary Microwave absorption by a lossy dielectric material containing thin metal wires is considered. The wires are bent to create either chiral, non-chiral or racemic unit cells. No physical mechanism is found to support patents which were granted between 1990 and 1993, and related claims in the engineering literature, that chirality is the key to improved microwave absorbers. Instead, in synthetic composites which employ thin metal wires in a lossy dielectric host, half-wave resonance of the inclusions – not their geometric shape – is identified as the mechanism responsible for enhanced absorption. It is also found that – even in an essentially lossless host – resonant steel wires, whether chiral or not, can strongly absorb electromagnetic waves.

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.

Improving the convergence and parallel memory efficiency of the MLFMM in FEKO

This paper summarizes the latest extensions to the multilevel fast multipole method in the commercial code FEKO: stabilisation and the use of IVIPI shared-memory programming.

Theory and application of an MLFMM/FEM hybrid framework in FEKO

The Multilevel Fast Multipole Method (MLFMM) has been combined with the Finite Element Method (FEM) in the computational electromagnetics code FEKO in order to offer a more efficient solution approach for electrically large problems incorporating complex dielectric regions. In this contribution, we present theoretical aspects and implementation details of the MLFMM/FEM technique in FEKO. Practical application examples are presented.

Recent extensions in FEKO suite 5.4

Many new features have been included in the latest release of the electromagnetic simulation package FEKO suite 5.4 from July 2008. This paper aims at giving an overview of the major new features added to the computational kernel, which are: Modelling of periodic boundary conditions for 1-D and 2-D periodic structures, the inclusion of waveguide port excitations within the MoM/PO hybrid method, the parallelisation of the MoM/FEM hybrid method for distributed memory systems, and also the modelling of complicated cable harnesses by a new interface to the cable modelling code CRIPTE.

Microwave absorption by chiral, racemic and non-chiral unit cells: the role of chirality in absorbing materials

A theoretical and experimental study is conducted to investigate the role of chirality in synthetic microwave absorbers. Three closely related anisotropic unit cells of thin wire objects, one chiral, one racemic and one non-chiral, are studied around resonance in a rectangular waveguide. Conducting thin wire chiral and non-chiral objects, embedded in an absorbing dielectric host and positioned in a rectangular waveguide, are numerically analysed with the finite difference time domain method. Measured and predicted results for the scattering parameters are presented.