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The finite difference time domain modelling of liquids with dispersive dielectric properties
Thesis (M. Eng.) -- University of Stellenbosch, 1995.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613907048202240 |
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| access_status_str | Open Access |
| author | Bingle, Marianne |
| author2 | Cloete, J. H. |
| author_browse | Bingle, Marianne Cloete, J. H. |
| author_facet | Cloete, J. H. Bingle, Marianne |
| author_sort | Bingle, Marianne |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (M. Eng.) -- University of Stellenbosch, 1995. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/54887 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:43:35.721Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/54887 The finite difference time domain modelling of liquids with dispersive dielectric properties Bingle, Marianne Cloete, J. H. Davidson, D. B. Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. Dielectrics Dielectric measurements Time-domain analysis Coaxial cables Body of revolution Dissertations -- Electrical engineering Thesis (M. Eng.) -- University of Stellenbosch, 1995. ENGLISH ABSTRACT: The dielectric properties of materials are of great importance in fundamental and applied research. A study of dielectric materials, their microscopic behaviour and their influence on macroscopic fields leads to the various material models for dispersive dielectric materials. A short review is given of the electromagnetic description of dielectric behaviour. A complete measurement system for measuring dispersive dielectric liquids is described. The system consists of a short-circuited coaxial cavity fed by a coaxial connector. The research for this thesis is concerned with the measurement and analysis of the coaxial cavity system filled with a dispersive dielectric of known properties. The goal is to obtain a model of the measuring system which accurately predicts the reflection measurements for the known dielectric. Measurements are conducted over the frequency range of the network analyser, 30MHz to 6GHz. The measurement system involves a stepped discontinuity in the coaxial geometry. The transition from the coaxial connector to the cavity is achieved by two step discontinuities, in the inner and outer conductors respectively, offset with a distance δ. The effect of the amount of offset on reflection in the coaxial system is investigated, both with the body of revolution finite difference time domain method and through measurement to find the optimum value of δ for minimum reflection over the frequency range of interest. Reflection measurements were done with a network analyser over the frequency range 30MHz to 6GHz. The results from the numerical simulations show good agreement with the measurements. The well-matched transition that resulted from this investigation led to simple calibration and modelling of the measurement system. The system is analysed in the time domain with the body of revolution finite difference time domain method and in the frequency domain with transmission line theory. The body of revolution finite difference time domain method solves for the time-dependent Maxwell equations; the discretised convolution integral is solved by recursion. The analysis of the measurement system is tested by determining the reflections from the cavity when filled with purified water and comparing it to measurements. In both methods of analysis, the permittivity of the water is described by a Debye model. The body of revolution finite difference time domain simulation, after transformation to the frequency domain, and the transmission line analysis are in good agreement. The measured reflection coefficient for a water-filled cavity is compared to the results of the analyses over the 30MHz to 6GHz frequency band. Water leaking into the transition region significantly influenced the measured reflection coefficient in the upper frequency band. Prevention of water leaking into the transition region improved the agreement between the measured and predicted reflection coefficient of the analysis. Higher order modes did not prove to be a problem in the highly symmetrical measurement system. AFRIKAANSE OPSOMMING: Diëlektriese eienskappe van materiale is belangrik in fundamentele en toegepaste navorsing. 'n Studie van diëlektriese materiale, hul mikroskopiese gedrag en hul invloed op makroskopiese velde lei tot die verskillende materiaalmodelle vir diëlektriese materiale. 'n Kort oorsig word gegee oor die elektromagnetiese beskrywing van diëlektriese materiale. 'n Volledige meetstelsel word beskryf om dispersiewe diëlektriese vloeistowwe te meet. Die stelsel bestaan uit 'n kortgeslote koaksiale silinder, gevoer met 'n koaksiale konnektor. Die navorsing vir hiedie tesis dek die meting en analise van die koaksiale stelsel, gevul met 'n dispersiewe vloeistof met goedomskryfde eienskappe. Die oogmerk is om 'n model van die meetstelsel te bepaal wat die weerkaatsmetings met die bekende diëlektrikum akkuraat voorspel. Die metings word uitgevoer oor die frekwensiebereik van die netwerk analiseerder, 30MHz tot 6GHz. Die oorgang van die konnektor na die silinder behels 'n trapdiskontinuiteit in die koaksiale geometrie. Die oorgang word bewerkstellig deur 'n trapdiskontinuiteit in beide die binne- en buitegeleier, geskei met n afstand δ. Die invloed van δ op die weerkaatsing in die koaksiale stelsel word ondersoek deur meting en deur die eindige verskil tydgebied metode vir rondomtalie strukture. Sodoende word 'n optimum waardfe vir δ bepaal waar minimum weerkaatsings oor die frekwensiebereik in die stelsel voorkom. Die weerkaatsmetings is met 'n netwerkanaliseerder gedoen oor die bereik 30MHz tot 6GHz. Die resultate van die numeriese simulasies toon goeie ooreenstemming met die metings. Hierdie ondersoek het ‘n goedaangepaste oorgang tot gevolg gehad wat tot eenvoudige kalibrasie en modellering van die meetstelsel gelei het. Die stelsel word in die tydgebied geanaliseer met die eindige verskil tydgebiecl metode en in die frekwensiegebied deur transmissielynanalise. Die eindige verskil formulering los die dispersiewe Maxwell vergelykings in die tydgebied op. Die gediskretiseerde konvolusie integraal word deur rekursie opgelos. Die analise van die meetstelsel word getoets deur die weerkaatsings te bepaal wanneer die silinder met gesuiwerde water gevul word en die resultaat te vergelyk met metings. Die permittiwiteit van die water word in beide metodes van analise deur n Debye model beskryf. Die numeriese simulasie, na transformasie na die frekwensiegebied en die transmissielynanalise toon goeie ooreenstemming oor die 6GHz frekwensiebereik; die gemete weerkaatskoëffisient word vergelyk met die resultate van die analise oor die 30MHz tot 6GHz frekwensiebereik van die meting. Water wat indring in die oorgangsgebied het 'n groot invloed gehad op die gemete weerkaatskoëffisient. Nadat die oorgangsgebied waterdig gemaak is, is die ooreenstemmeing tussen die metings en die voorspelde weerkaatskoëffisient van die analise verbeter. Hoër orde modusse was nie 'n probleem in die hoogs simmetriese meetstelsel nie. Masters 2012-08-27T11:36:47Z 2012-08-27T11:36:47Z 1995 Thesis http://hdl.handle.net/10019.1/54887 en_ZA Stellenbosch University 97 pages : ill. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Dielectrics Dielectric measurements Time-domain analysis Coaxial cables Body of revolution Dissertations -- Electrical engineering Bingle, Marianne The finite difference time domain modelling of liquids with dispersive dielectric properties |
| title | The finite difference time domain modelling of liquids with dispersive dielectric properties |
| title_full | The finite difference time domain modelling of liquids with dispersive dielectric properties |
| title_fullStr | The finite difference time domain modelling of liquids with dispersive dielectric properties |
| title_full_unstemmed | The finite difference time domain modelling of liquids with dispersive dielectric properties |
| title_short | The finite difference time domain modelling of liquids with dispersive dielectric properties |
| title_sort | finite difference time domain modelling of liquids with dispersive dielectric properties |
| topic | Dielectrics Dielectric measurements Time-domain analysis Coaxial cables Body of revolution Dissertations -- Electrical engineering |
| url | http://hdl.handle.net/10019.1/54887 |
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