Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: A computational tool for numerical synthesis via optimization is developed. Only
two port waveguide devices are considered. The Finite Element Method (FEM) is
used for the electromagnetic analysis. Specifically, the frequency domain electric
field FEM is used with vector curl-conforming constant tangential/linear normal
brick-shaped elements. Special boundary conditions are used at the ports.
These boundary conditions only consider dominant mode propagation. The issues
surrounding the implementation of this formulation are discussed. The results generated
using this code compare favorably to examples from independent sources.
A parametric mesher that is used in conjunction with the FEM is developed. This
is done to eliminate the need for human intervention during each iteration of the
synthesis procedure. Fast Frequency (FF) techniques are presented to reduce the
computational requirements of the synthesis. FF techniques reduce the cost of calculating
many frequency samples in a specified band and do not reduce the computational
requirements of computing a FEM solution at a single frequency. The FF
techniques presented are: Asymptotic Waveform Evaluation (AWE), Model Based
Asymptotic Waveform Evaluation (MB-AWE) and Model Based Parameter Estimation
(MBPE) . The results obtained using these techniques are compared and
the most suitable technique for the synthesizer is selected. MBPE is selected as
the most suitable technique for this application. An adaptive sampling algorithm
for Model Based Parameter Estimation is presented. The algorithm relies on the
difference between multiple models generated from the same samples to determine
the sample locations. The use of this algorithm enables a model of a narrow band
filter at X-band to be determined using only fourteen FEM solutions. The difference
between the model- and the FEM solutions is less then -lOOdBacross the
band. A sample synthesis using generalized simulated annealing is presented. A
single pole filter in X-band waveguide is successfully synthesized to illustrate the
usefulness of the code. The use of FF techniques results in a computational cost
saving of a factor of forty times. / AFRIKAANSE OPSOMMING: 'n Rekenaar werktuig vir numeriese sintese deur middel van optimering word ontwikkel.
Slegs twee-poort golfleierkomponente word beskou.
Die Eindige Element-metode (EEM) word vir die elektromagnetiese analise gebruik.
Meer spesifiek, die frekwensiegebied, elektriese-veld EE-formuleering word
gebruik, met eurl-ondersteunende, konstant-tagensiaaljlineêr-normaal, baksteenvormige
vektorelemente. Spesiale grensvoorwaardes word by die poorte gebruik.
Hierdie grensvoorwaardes neem slegs voortplanting van die dominante modus in ag.
Die kwessies rondom die implementering van hierdie EEM word bespreek. Resultate
wat met hierdie kode verkry word, vergelyk goed met dié vanuit onafhanklike
bronne. 'n Parametriese diskretisasie prosedure in ontwikkel, vir gebruik saam
met die genoemde EEM, met die doelom menslike interaksie uit die weg te ruim,
tydens die sintese proses.
Vinnige Frekwensie (VF) tegnieke word beskryf, met die doelom die berekeningskoste
van die sintese te verminder. VF tegnieke verminder die berekeningskoste
verbonde aan 'n reeks EEM oplosings binne 'n gegewe frekwensieband, maar verminder
nie die koste verbonde aan 'n enkel-frekwensie EEM oplossing nie. Die
VF tegnieke wat beskryf word, is die volgende: Asimptotiese Golfvorm Evaluasie
(AGE), Model Gebaseerder Asimptotiese Golfvormevaluasie (MGAGE) en Model-
Gebaseerde Parameterekstraksie (MGPE). Die resultate wat met hierdie metodes
verkry word, word vergelyk om sodoende die mees toepaslike VF tegniek te kies.
MGPE word gekies as die mees toepaslike tegniek.
'n Aanpasbase monsteringsalgoritme vir MGPE word beskryf. Die algoritme berus
op die verskil tussen twee modelle wat vanaf dieselfde stel punte geskep word, om
monsterfrekwensiewaardes te bepaal. Die gebruik van hierdie algoritme lei tot 'n
model van 'n nou-, X-band filter, vanuit slegs veertien EEM oplossings. Die verskil
tussen hierdie model en enige EEM oplossings binne die band, is kleiner as -lOOdB.
'n Voorbeeld sintese, wat gebruik maak van veralgemeende, gesimuleerde versmelting,
word beskryf. 'n Enkel-pool filter by X-band word suksesvol gesintetiseer om
die bruikbaarheid van die kode te illustreer. 'n Faktor veertig vermindering III
berekeningskostes word behaal deur gebruik te maak van VF tegnieke.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52762 |
| Date | 12 1900 |
| Creators | Clarke, Samuel R. (Samuel Robert) |
| Contributors | Davidson, D. B., Stellenbosch University. Faculty of EngineeringEngineering. 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 | 88 p. : ill. |
| Rights | Stellenbosch University |
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