Thesis (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: This thesis is concerned with the measurement of the complex permeability of
thin round wires at radio frequencies. This is of interest as such wires are used
in various applications, such as absorbing chaff. Iron and nickel alloys are also
used for their good tensile properties but have an undesired electromagnetic effect
which needs to be characterised. Although little work has been done in this field
in recent decades it remains a relevant problem. In this thesis the advantages of
accurate wide-band measurements performed by automatic network analysers are
applied to the field.
The measurement system is a closed coaxial transmission line with a short
circuit termination. The centre conductor is the wire of interest. The surface
impedance of the wire is related to complex permeability and is measured using
low-loss transmission line approximations applied to half-wavelength resonances.
The loss associated with complex permeability is separated from conductivity by
a D.C. conductivity measurement.
A full wave analysis of the coaxial mode was performed and compared to
measured values. The maximum error of the propagation constant was found to
be 31% at the highest frequencies and was primarily due to length uncertainties.
By varying parameters expected error bands around the measured permeability
were found. These bands are of the order 1 and demonstrate that the system is
sufficiently robust.
The measurement of the permeability of two non-magnetic wires was performed
and a relative permeability of 1 was found, demonstrating the correct
working of the system. A steel wire was measured and compared to measurements
found in literature. The permeability dropped as frequency rose as was expected,
and an acceptable comparison to other measurements was made as there
is no verification standard.
Thus a simple measurement system that takes advantage of calibrated automatic
network analyser measurements has been developed and demonstrated to
work with sufficient accuracy. / AFRIKAANSE OPSOMMING: In hierdie tesis word die meting van die komplekse permeabiliteit van dun
ronde drade by radio frekwensies ondersoek. Hierdie drade word in verskeie
toepassings gebruik, waaronder dié van absorberende materiale. Nikkel- en ysterallooie
word ook vir hul goeie breekkrageienskappe gebruik. In laasgenoemde
gevalle moet die ongewenste elektromagnetiese effekte wat voorkom, gekarakteriseer
word. Hoewel baie min werk in onlangse dekades gedoen is, bly die meting
van die komplekse permeabiliteit 'n relevante probleem. In hierdie tesis word
die voordele van akkurate wyeband metings, soos geneem deur 'n outomatiese
netwerk analiseerder, toegepas in dié veld.
Die meetopstelling is 'n geslote koaksiale transmissielyn, kortgesluit aan een
end. Die middel geleier is die draad van belang. Die oppervlak impedansie van
die draad is verwant aan die komplekse permeabiliteit, en word gemeet deur die
gebruik van lae verlies transmissielyn benaderings, soos toegepas op halfgolf resonante
frekwensies. Die verlies wat met die komplekse permeabiliteit geassosieer
word, word van die geleidingsvermoë onderskei deur 'n G.S. meting van die geleidingsvermoë.
'n Volgolf analise van die koaksiale mode is uitgevoer en met gemete waardes
vergelyk. 'n Maksimum fout van 31% by die hoogste frekwensie is in die voortplantingskonstante
gevind. Hierdie volg primêr uit onsekerhede in lengte. Deur
die parameters te varieer kon 'n verwagte foutband rondom die gemete permeabiliteit
gevind word. Hierdie bande is van die orde 1 waaruit volg dat die stelsel
'n genoegsame robuustheid toon.
Die komplekse permeabiliteit van twee nie-magnetiese drade is gemeet en 'n
relatiewe permeabiliteit van 1 is gevind. Hierdie bevestig die korrekte werking van
die stelsel. 'n Staal draad is opgemeet en met gepubliseerde meetresultate vergelyk.
Soos verwag, verminder die permeabiliteit met 'n verhoging in frekwensie.
Hoewel geen verifiëringstandaard beskikbaar is nie, is 'n aanvaarbare vergelyking
met ander metings gemaak.
Die produk van die navorsing is 'n metingstelsel wat, met behulp van 'n gekalibreerde
outomatiese netwerk analiseerder, aanvaarbare akkuraatheid in die meting
van die komplekse permeabiliteit van dun ronde drade by radio frekwensies kan
verkry.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53657 |
| Date | 04 1900 |
| Creators | Stuart, Thomas (Thomas Edward Walter) |
| Contributors | Reader, H. C., Cloete, J. H., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 69 p. : ill. |
| Rights | Stellenbosch University |
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