Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: A new type of wideband lters, with tunability in both the centre frequency and bandwidth,
is presented in this thesis. These lters are based on perturbed ring-resonators in
cascade, while varactor diodes are used for electronic tuning.
The Karoo Array Telescope (KAT-7) requires a front-end lter that has the ability
for ne-tuning the response after fabrication, in order to obtain the designed ltering
response. Not only are tune-all characteristics required, but also wide bandwidth, at
passband, high selectivity and implementation in microstrip technology.
In this thesis an extensive investigation of both tunable and wideband lters is done, in
order to nd a possible solution for the KAT-7 speci cations. Following this investigation,
it is concluded that no suitable design approach for tune-all wideband lters, implemented
in microstrip, exists in current literature.
Therefore, this thesis proposes a new type of lter along with the development of a
complete design procedure. Two lters are designed with this procedure to achieve the
required passband from 1.2 to 1.95 GHz (i.e. a fractional bandwidth of 49%). In the
rst lter design, with a network consisting of 4 cascaded ltering-sections, the centre
frequency is 5% tunable and the bandwidth 17.5%. With the second lter consisting of 6
cascaded ltering-sections, higher selectivity is achieved but with lower return loss. Here
the centre frequency is 8.5% tunable and the bandwidth 18.8%. The theoretical results
are validated with the fabrication of both lters.
This design is very unique in that it achieves wide bandwidth, is realisable in microstrip
and most importantly is tunable in both the centre frequency and bandwidth.
An advantage of this design procedure is that full wave simulations are minimal, due to
the complete circuit models used for optimisation. / AFRIKAANSE OPSOMMING: 'n Nuwe soort van wye-band lters, met verstelbaarheid in beide senter frekwensie en
bandwydte, word voorgelê in hierdie tesis. Hierdie lters is gebaseer op versteurde ringresoneerders
in kaskade, terwyl varaktordiodes gebruik word vir elektroniese verstelling.
Die Karoo Array Telescope (KAT-7) vereis 'n voorkant lter wat die vermoë het vir
die instemming van die respons na fabrikasie, sodat die geontwerpde lter respons behaal
kan word. Nie net word verstel-als eienskappe vereis nie, maar ook wye bandwydte, plat
deurlaatband, hoë selektiwiteit en implimentering in mikrostrook tegnologie.
In hierdie tesis is 'n veelomvattende ondersoek gedoen van beide verstelbare en wyeband
lters, sodat 'n moontlike oplossing vir die KAT-7 spesi kasies gevind kan word. Na
aanleiding van hierdie ondersoek, is die gevolgtrekking dat daar geen gepaste ontwerp benadering
vir verstel-als wye-band lters, wat geïmplimenteer is in mikrostrook, in huidige
literatuur bestaan nie.
Daarom stel hierdie tesis, saam met die ontwikkeling van 'n volledige ontwerp prosedure,
'n nuwe tipe lter voor. Twee lters is ontwerp met hierdie prosedure om die
vereiste deurlaatband vanaf 1.2 tot 1.95 GHz (dit is 'n fraksionele bandwydte van 49%)
te behaal. In die eerste lter ontwerp, met 'n netwerk wat uit 4 kaskade lter-seksies
bestaan, is die senter frekwensie 5% verstelbaar en die bandwydte 17.5%. Met die tweede
lter bestaande uit 6 kaskade lter-seksies, word hoër selektiwiteit behaal maar met laer
eggoverswakking. Hier is die senter frekwensie 8.5% verstelbaar en die bandwydte 18.8%.
Die teoretiese resultate is geldig bewys deur die fabrikasie van albei lters.
Hierdie ontwerp is baie uniek in dat dit wye bandwydte behaal, is realiseerbaar in
mikrostrook en mees belangrikste dat dit verstelbaar is in beide senter frekwensie en
bandwydte. 'n Voordeel van hierdie prosedure is dat heelgolf simulasies minimaal is,
a.g.v. die volledige stroombaan modelle wat gebruik word vir optimering.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/17791 |
| Date | 12 1900 |
| Creators | Beukman, Theunis Steyn |
| Contributors | Geschke, R. 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 | 119 p. : ill. |
| Rights | Stellenbosch University |
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