Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods

The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGF...

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Main Author:	Ramli, Khairun Nidzam
Format:	Thesis
Language:	English
Published:	2011
Subjects:	QC Physics QC501-766 Electricity and magnetism
Online Access:	http://eprints.uthm.edu.my/3026/1/24p%20KHAIRUN%20NIDZAM%20RAMLI.pdf
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id	my-uthm-ep.3026
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spelling	my-uthm-ep.30262021-11-02T01:40:16Z Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods 2011 Ramli, Khairun Nidzam QC Physics QC501-766 Electricity and magnetism The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric materials irradiated by geometrically intricate sources. The Method of Moments modelling employed a two-dimensional electric surface patch integral formulation solved by independent linear basis function methods in the circumferential and axial directions of the antenna wires. A similar orthogonal basis function is used on the end surface and appropriate attachments with the wire surface are employed to satisfy the requirements of current continuity. The surface current distributions on structures which may include closely spaced parallel wires, such as dipoles, loops and helical antennas are computed. The results are found to be stable and showed good agreement with less comprehensive earlier work by others. The work also investigated the interaction between overhead high voltage transmission lines and underground utility pipelines using the FDTD technique for the whole structure, combined with a subgridding method at points of interest, particularly the pipeline. The induced fields above the pipeline are investigated and analysed. FDTD is based on the solution of Maxwell’s equations in differential form. It is very useful for modelling complex, inhomogeneous structures. Problems arise when open-region geometries are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to circumvent this difficulty. The establishment of edge elements has greatly improved the performance of this method and the computational burden due to huge numbers of time steps, in the order of tens of millions, has been eased to tens of thousands by employing quasi-static methods. This thesis also illustrates the principle of the equivalent surface boundary employed close to the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid techniques due to their ability to analyse a system of multiple discrete regions by employing the principle of equivalent sources to excite the coupling surfaces. The method has been applied for modelling human body interaction with a short range RFID antenna to investigate and analyse the near field and far field radiation pattern for which the cumulative distribution function of antenna radiation efficiency is presented. The field distributions of the simulated structures show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of the phenomena in the interaction between electromagnetic fields and human tissues. 2011 Thesis http://eprints.uthm.edu.my/3026/ http://eprints.uthm.edu.my/3026/1/24p%20KHAIRUN%20NIDZAM%20RAMLI.pdf text en public phd doctoral University of Bradford School of Engineering, Design and Technology
institution	Universiti Tun Hussein Onn Malaysia
collection	UTHM Institutional Repository
language	English
topic	QC Physics QC501-766 Electricity and magnetism
spellingShingle	QC Physics QC501-766 Electricity and magnetism Ramli, Khairun Nidzam Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods
description	The main objective of this research is to model and analyse complex electromagnetic problems by means of a new hybridised computational technique combining the frequency domain Method of Moments (MoM), Finite-Difference Time-Domain (FDTD) method and a subgridded Finite-Difference Time-Domain (SGFDTD) method. This facilitates a significant advance in the ability to predict electromagnetic absorption in inhomogeneous, anisotropic and lossy dielectric materials irradiated by geometrically intricate sources. The Method of Moments modelling employed a two-dimensional electric surface patch integral formulation solved by independent linear basis function methods in the circumferential and axial directions of the antenna wires. A similar orthogonal basis function is used on the end surface and appropriate attachments with the wire surface are employed to satisfy the requirements of current continuity. The surface current distributions on structures which may include closely spaced parallel wires, such as dipoles, loops and helical antennas are computed. The results are found to be stable and showed good agreement with less comprehensive earlier work by others. The work also investigated the interaction between overhead high voltage transmission lines and underground utility pipelines using the FDTD technique for the whole structure, combined with a subgridding method at points of interest, particularly the pipeline. The induced fields above the pipeline are investigated and analysed. FDTD is based on the solution of Maxwell’s equations in differential form. It is very useful for modelling complex, inhomogeneous structures. Problems arise when open-region geometries are modelled. However, the Perfectly Matched Layer (PML) concept has been employed to circumvent this difficulty. The establishment of edge elements has greatly improved the performance of this method and the computational burden due to huge numbers of time steps, in the order of tens of millions, has been eased to tens of thousands by employing quasi-static methods. This thesis also illustrates the principle of the equivalent surface boundary employed close to the antenna for MoM-FDTD-SGFDTD hybridisation. It depicts the advantage of using hybrid techniques due to their ability to analyse a system of multiple discrete regions by employing the principle of equivalent sources to excite the coupling surfaces. The method has been applied for modelling human body interaction with a short range RFID antenna to investigate and analyse the near field and far field radiation pattern for which the cumulative distribution function of antenna radiation efficiency is presented. The field distributions of the simulated structures show reasonable and stable results at 900 MHz. This method facilitates deeper investigation of the phenomena in the interaction between electromagnetic fields and human tissues.
format	Thesis
qualification_name	Doctor of Philosophy (PhD.)
qualification_level	Doctorate
author	Ramli, Khairun Nidzam
author_facet	Ramli, Khairun Nidzam
author_sort	Ramli, Khairun Nidzam
title	Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods
title_short	Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods
title_full	Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods
title_fullStr	Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods
title_full_unstemmed	Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods
title_sort	modelling and analysis of complex electromagnetic problems using fdtd subgridding in hybrid computational methods
granting_institution	University of Bradford
granting_department	School of Engineering, Design and Technology
publishDate	2011
url	http://eprints.uthm.edu.my/3026/1/24p%20KHAIRUN%20NIDZAM%20RAMLI.pdf
_version_	1747831013326716928

Modelling and analysis of complex electromagnetic problems using FDTD subgridding in hybrid computational methods

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