Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: An investigation of the functional similarities and di erences between a combline lter and an evanescent-mode
waveguide lter is presented. The design theory of the two types of lters is outlined. Two lters are designed
to operate at a centre frequency of 2 GHz with a 5% bandwidth using similar waveguide dimensions, but using
the two di erent design theories. The bandpass characteristics of the two lters are then compared over the
primary passband and over a broad range of frequencies to observe the stopband characteristics. It is shown
that a combline lter with a large groundplane spacing behaves like an evanescent-mode waveguide lter but a
di erence in bandwidth exists between the two.
Di erent aspects related to the manufacture of coaxial cavity lters are addressed with speci c emphasis on
cost reduction. The considerations to be made when choosing the right materials, manufacturing techniques
and surface nishes for microwave coaxial cavity lters so that good performance is obtained while reducing
the overall costs associated with manufacturing are discussed. The concept of Design for Manufacture (DFM)
is discussed.
Three combline lters are designed for reduced manufacturing cost, applying di erent changes in the physical
structure to suit the speci c manufacturing technique used. Two of these have the same design speci cations,
operating at a centre frequency of 1.3 GHz with a 10% bandwidth but are designed for manufacture using two
di erent manufacturing techniques: milling and wire-cutting EDM. The third lter is designed for manufacture
using a combination of the milling and wirecutting processes to have a bandwidth of 1.8% with the primary
passband centred at 2.125 GHz. Problems encountered in manufacturing are explained, one of which results in
the use of waterjet cutting for the manufacture of lters initially supposed to be manufactured using wirecutting
EDM. Measurement results for the manufactured lters show a good agreement between the bandwidths of the
3D electomagnetic simulation results. The obtained results also show the e ects of poor surface nishing and
of deformations on the resonant frequency and the unloaded Q of the lters. / AFRIKAANSE OPSOMMING: 'n Studie van die funksionele ooreenkomste en verskille tussen kamlyn lters en gol
eier-onder-afknip lters
word aangebied. Die ontwerpstegnieke van beide tipes lters word aangebied. Twee lters word ontwerp met 'n
senterfrekwensie van 2GHz en 'n bandwydte van 5%, met soortgelyke gol
eierafmetings maar deur gebruik te
maak van die verskillende ontwerpstegnieke. Die gedrag van die twee lters word vergelyk in die deurlaatband
sowel as oor 'n wye stopband. Dit word getoon dat 'n kamlyn lter met 'n groot grondvlakspasi ering soos 'n
gol
eier-onder-afknip lter optree, met 'n verskil in bandwydte.
Verskillende aspekte wat verband hou met die vervaardiging van koaksiale lters, met spesi eke klem op koste
vermindering, word aangebied. Die oorwegings wat die keuses van materiaal, vervaardigingstegnieke en oppervlakte
afwerking be nvloed word bespreek. Die konsep van Ontwerp vir Vervaardiging (DFM in Engels) word
bespreek.
Drie kamlyn lters word ontwerp vir verminderde vervaardigingskoste deur die siese sruktuur aan te pas by die
spesi eke vervaardigingstegniek. Twee van die lters het dieselfde spesi kasie, naamlik 'n senterfrekwensie van
1.3GHz en 'n 10% bandwydte, maar word ontwerp vir twee verskillende vervaardigingsprosesse, naamlik frees en
draadsny. 'n Derde lter word ontwerp vir 'n kombinasie van hierdie twee prosesse, en met 'n senterfrekwensie
van 2.125GHz en 'n bandwydte van 1.8%. Probleme met die vervaardiging word bespreek, onder andere die
verandering van draadsny na water-sny tegnieke. Gemete resultate toon goeie ooreenstemming met die teoretiese
analise wat die bandwydtes betref, maar swak oppervlak afwerking het 'n verswakking van die onbelaste Q van
die resoneerders tot gevolg.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/18064 |
| Date | 12 1900 |
| Creators | Nassar, Shamim O. |
| Contributors | Meyer, P., Van der Walt, P. W., De Villiers, D. I. L., 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 | English |
| Type | Thesis |
| Format | 166 p. : ill. |
| Rights | Stellenbosch University |
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