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.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The primary payload of the University of Stellenbosch's micro-satellite, SUNSAT I, was a high quality imager, capable of taking stereoscopic images of the surface of the earth. Although the orbit of SUNSAT I will have the satellite pass over the whole earth, contact via the SUNSAT I ground station at the University will only be made for 3% of each day. To be able to photograph any part of the earth onboard memory was provided on the satellite to store the image until it can be downloaded to the ground station. A high speed downlink was also added to the satellite to be able to download a complete image from the onboard memory in one pass and also to take realtime pictures as the satellite passes over the ground station. At that stage there was no way to capture the data at the ground station. A high speed digital data capture mechanism was needed. The thesis discusses the development of a high speed capture card. Due to the high speeds needed it provided an excellent opportunity to develop the card using the PCI bus, the first design to do so at the University, as an interface with a computer. A prototype card was developed first to do proof of concept. It is shown that the prototype card fulfilled the functional requirements and it was also used to capture the first image from the complete satellite during the final tests before launch. Finally a production card for use in the ground station was designed and assembled. / AFRIKAANSE OPSOMMING: Die hoof loonvrag van die Universtieit van Stellenbosch se eerste mikrosatelliet, SUNSAT I, is "n hoë kwaliteit kamera wat stereoskopiese fotos van die oppervlak van die aarde kan neem. Alhoewel die satelliet oor die hele oppervlakte van die aarde gaan beweeg, is dit vir slegs 3% van die dag sigbaar vanaf die grondstasie by die Universiteit van Stellenbosch. Om 'n foto van enige plek op aarde te kan neem is daar aanboord geheue op die satelliet geplaas om die foto te stoor totdat dit by die grondsatsie afgelaai kan word. "n Hoë spoed skakel is ook daargestelom die data in die geheue van die satelliet in een verbyvlug te kan aflaai. Dit stel die satelliet ook in staat om intydse fotos gedurende In verbyvlug van die satelliet te kan neem. Op daardie stadium het daar nog nie "n manier bestaan om die hoë spoed data vas te lê nie. In Meganisme om die hoë spoed digitale data te vang was nodig. Hierdie tesis bespreek die ontwikkeling van so In data vang kaart. Weens die hoë snelhede wat benodig word, het die PCI bus die ideale oplossing gebied om die data teen "n hoë spoed op In persoonlike rekenaar te stoor. Dit was ook die eerste ontwerp aan die Universiteit wat van die PCI bus gebruik gemaak het. In die eerste instansie is In prototipe ontwikkel om te bewys dat dit wel moontlik is om die data teen die benodigde tempo te kan stoor. Daar word gewys dat die prototipe aan die behoefte voldoen en dit is ook gebruik om die eerste beeld vanaf die volledige satelliet te vang voordat dit gelanseer is. In die tweede instansie word In produksiekaart ontwikkel en aanmekaar gesit.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: High-temperature (HTc) SQUID magnetometers are used in the biomedical field of magnetocardiography (MCG). The use of MCG enables a much earlier diagnosis of potentially dangerous conditions than the use of electrocardiography (EeG). For the use of MCG, high-quality HTc SQUIDs are necessary. These SQUIDs can only be realised if the design and fabrication processes are well defined and understood. In this thesis an extensive literature review on the design process explains all the concepts necessary to understand and design a high-quality HTc SQUID. Then the fabrication process is redefined and characterised. The SQUIDs are fabricated with YBCO thin films on MgO substrates. The relevant steps in the process are the pulsed laser deposition (PLD), UV lithography and argon ion milling. The characterisation of the fabrication process is based on a statistical method called Design of Experiment (DOE). This enables more information to be obtained about the fabrication process than before. For the PLO process the important parameters are determined and an initial optimisation is done. During the characterisation process it is proven that the use of ozone during PLO has a positive effect on the quality of the YBCO thin film. On the PLD apparatus the substrate heater and laser-beam profile is improved. The UV lithography process is analysed and a DOE is proposed for optimisation. A temperature bath is added to the process to enable better reproducibility. An rf multicusp ion mill is built for argon-ion milling, this device is tested and shown to provide the required etching capability. / AFRIKAANSE OPSOMMING: Hoë-temperatuur (HTc) SQUID magnetometers word in die biomediese rigting vir magnetokardiografie (MKG) gebruik. Met MKG kan 'n mens potensieel gevaarlike toestande heelwat vroeër diagnoseer as wat moontlik is met elektrokardiografie (EKG). HTc SQUIDs van hoë kwaliteit word benodig vir MKG. Sulke SQUIDs kan slegs vervaardig word as die vervaardiging en ontwerpsprosesse goed gedefinieer en verstaan word. In hierdie tesis verduidelik 'n omvattende literatuurstudie oor die ontwerpsproses al die konsepte wat nodig is om 'n SQUID van hoë kwaliteit te verstaan en te ontwerp. Verder word die vervaardigingsproses geherdefinieer en gekarakteriseer. Die SQUIDs word vervaardig met YBCO-dunfilm op MgO-substrate. Die relevante stappe tydens die vervaardiging is: gepulseerde laser deposisie (PLO), UV-litografie en argon-ioonstraling. Die karakterisering van die vervaardigingsproses is gebaseer op 'n statistiese metode genaamd "Design of Experiment" (DOE). Hierdie metode laat 'n mens toe om meer inligting oor die proses te verkry as wat voorheen moontlik was. Gedurende die karakterisering word bewys dat die gebruik van osoon gedurende die PLO-proses 'n positiewe invloed op die kwaliteit van die YBCO-dunfilm het. Die PLO-apparaat se substraatverwarmer en laserstraalprofiel word verbeter. Die UV-litografieproses word geanaliseer en 'n DOE word voorgestel vir die optimisering daarvan. Daar word 'n temperatuurbad by die proses gevoeg om die herhaalbaarheid te verbeter. 'n "Rf multicusp ion mill" word gebou, die toestel word getoets en daar word aangetoon dat dit die nodige etsvermoë het.

Thesis (MScEng)--Stellenbosch University, 2002. / Some digitised pages may appear illegible due to the condition of the original hard copy. / ENGLISH ABSTRACT: Speaker recognition systems have evolved to a point where near perfect performance can be obtained under ideal conditions, even if the system must distinguish between a large number of speakers. Under adverse conditions, such as when high noise levels are present or when the transmission channel deforms the speech, the performance is often less than satisfying. This project investigated the performance of a popular speaker recognition system, that use Gaussian mixture models, on speech transmitted over a high frequency channel. Initial experiments demonstrated very unsatisfactory results for the base line system. We investigated a number of robust techniques. We implemented and applied some of them in an attempt to improve the performance of the speaker recognition systems. The techniques we tested showed only slight improvements. We also investigates the effects of a high frequency channel and single sideband modulation on the speech features of speech processing systems. The effects that can deform the features, and therefore reduce the performance of speech systems, were identified. One of the effects that can greatly affect the performance of a speech processing system is noise. We investigated some speech enhancement techniques and as a result we developed a new statistical based speech enhancement technique that employs hidden Markov models to represent the clean speech process. / AFRIKAANSE OPSOMMING: Sprekerherkenning-stelsels het 'n punt bereik waar nabyaan perfekte resultate verwag kan word onder ideale kondisies, selfs al moet die stelsel tussen 'n groot aantal sprekers onderskei. Wanneer nie-ideale kondisies, soos byvoorbeeld hoë ruisvlakke of 'n transmissie kanaal wat die spraak vervorm, teenwoordig is, is die resultate gewoonlik nie bevredigend nie. Die projek ondersoek die werksverrigting van 'n gewilde sprekerherkenning-stelsel, wat gebruik maak van Gaussiese mengselmodelle, op spraak wat oor 'n hoë frekwensie transmissie kanaal gestuur is. Aanvanklike eksperimente wat gebruik maak van 'n basiese stelsel het nie goeie resultate opgelewer nie. Ons het 'n aantal robuuste tegnieke ondersoek en 'n paar van hulle geïmplementeer en getoets in 'n poging om die resultate van die sprekerherkenning-stelsel te verbeter. Die tegnieke wat ons getoets het, het net geringe verbetering getoon. Die studie het ook die effekte wat die hoë-frekwensie kanaal en enkel-syband modulasie op spraak kenmerkvektore, ondersoek. Die effekte wat die spraak kenmerkvektore kan vervorm en dus die werkverrigting van spraak stelsels kan verlaag, is geïdentifiseer. Een van die effekte wat 'n groot invloed op die werkverrigting van spraakstelsels het, is ruis. Ons het spraak verbeterings metodes ondersoek en dit het gelei tot die ontwikkeling van 'n statisties gebaseerde spraak verbeteringstegniek wat gebruik maak van verskuilde Markov modelle om die skoon spraakproses voor te stel.

Thesis (MScEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: There is a large variety of telemetry recervmg software currently available for the reception of telemetry information from different satellites. Most of the software used in receiving telemetry data is satellite specific. Hence, a user-friendly way is needed to make telemetry data easily accessible. A satellite-based web server is aimed at providing telemetry information to any standard web browser as a way of bringing space technology awareness to the people. Two different satellite-based web server methods are examined in this thesis. Based on the evaluation, the on-board File server with proxy server was proposed for satellite-based web server development. This requires that the File server be ported to the on-board computer of the satellite. The web proxy server is placed on the ground segment with the necessary communication requirements to communicate with the on-board File server. In the absence of satellite, the satellite-based web server was successfully implemented on two computers, laying a good foundation for implementation on the on-board computer of the satellite (OBe). / AFRIKAANSE OPSOMMING: Daar is 'n groot verskeidenheid telemetrie ontvangs sagteware huidiglik beskikbaar vir die ontvangs van telemetrie informasie vanaf verskillende satelliete. Die meeste van die sagteware wat gebruik word om telemetrie data te ontvang is satelliet spesifiek. Gevolglik, 'n gebruikers vriendelike metode is nodig om telemetrie data maklik beskikbaar te maak. 'n Satelliet-gebaseerde web-bediener word beoog om telemetrie informasie te verskaf aan enige standaard web-blaaier as 'n metode om mense bewus te maak van ruimte tegnologie. Twee verskillende satelliet gebaseerde web-bediener metodes salondersoek word in hierdie tesis. Gebaseer op 'n evaluering, word die aanboord leêr-bediener met instaanbediener voorgestel vir satelliet-gebaseerde webbediener ontwikkeling. Hiervoor is dit nodig dat die leêr-bediener na die aanboord rekenaar van die satelliet gepoort word. Die web instaanbediener word op die grond segment geplaas met die nodige kommunikasie benodighede, om te kommunikeer met die aanboord leêr-bediener. In die afwesigheid van die satelliet was die satellietgebaseerde web-bediener met sukses geïmplementeer op twee rekenaars, met die gevolg dat 'n goeie fondasie gelê is vir die implementering op die aanboord rekenaar van die satelliet (OBC).

Thesis (MScEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: We present all the components needed for a fully-fledged stereo vision system, ranging from object detection through camera calibration to depth perception. We propose an efficient, automatic and practical method to calibrate cameras for use in 3D machine vision metrology. We develop an automated stereo calibration system that only requires a series of views of a manufactured calibration object in unknown positions. The system is tested against real and synthetic data, and we investigate the robustness of the proposed method compared to standard calibration practice. All the aspects of 3D stereo reconstruction is dealt with and we present the necessary algorithms to perform epipolar rectification on images as well as solving the correspondence and triangulation problems. It was found that the system performs well even in the presence of noise, and calibration is easy and requires no specialist knowledge. / AFRIKAANSE OPSOMMING: Ons beskryf al die komponente van 'n omvattende stereo visie sisteem. Die kern van die sisteem is 'n effektiewe, ge-outomatiseerde en praktiese metode om kameras te kalibreer vir gebruik in 3D rekenaarvisie. Ons ontwikkel 'n outomatiese, stereo kamerakalibrasie sisteem wat slegs 'n reeks beelde van 'n kalibrasie voorwerp in onbekende posisies vereis. Die sisteem word getoets met reële en sintetiese data, en ons vergelyk die robuustheid van die metode met die standaard algoritmes. Al die aspekte van die 3D stereo rekonstruksie word behandel en ons beskryf die nodige algoritmes om epipolêre rektifikasie op beelde te doen sowel as metodes om die korrespondensie- en diepte probleme op te los. Ons wys dat die sisteem goeie resultate lewer in die aanwesigheid van ruis en dat kamerakalibrasie outomaties kan geskied sonder dat enige spesialis kennis benodig word.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Structure from Motion is defined as the problem of extracting the 3d motion of a camera moving through a scene, as well as the 3d structure of the scene, from the image sequence produced by the camera over time. Several methods based on the Kalman filter have been proposed in the past, mostly based on the Extended Kalman filter. We propose an algorithm based on the dual Unscented Kalman filter to estimate the structure and motion of an object under perspective projection. It is shown that the algorithm is stable and accurate under synthetic as well as real-world conditions. / AFRIKAANSE OPSOMMING: Struktuur vanuit Beweging is 'n rekenaar-visie probleem waarin die 3d beweging van 'n kamera deur 'n ruimte, asook die 3d struktuur van die ruimte, bepaal moet word slegs vanuit die 2d beelde in die beeldreeks wat deur die kamera geneem word. 'n Verskeie reeks oplossings, gebaseer op die Kalman filter, is reeds voorgestelom die probleem op te los. Meeste van die oplossings implementeer die "Extended Kalman filter", of EKF. Ons stel 'n algoritme voor, gebaseer op 'n nuwe nie-lineêre benadering tot die Kalman filter, die sogenaamde "Unscented Kalman filter", of UKF. Hierdie algoritme bepaal die struktuur en beweging onder 'n perspektief-projeksie kamera. Daar word getoon dat die algoritme stabiel en akkuraat funskioneer onder sintetiese sowel as reële toevoer.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Keywords: Coupled resonator filters, Co-axial line resonators, Basic Coupling Design, Co-axial resonator filter The study of the basic dynamics of filters, with the emphasis on coupled resonator filters, is presented. Special attention is paid to the synthesis of doubly terminated coupling matrices using the Darlington method. Due to restrictions placed on the filter by the equivalent circuit used, a coupling matrix reduction is applied to the resulting coupling matrix. An investigation is performed on A/2 co-axial line resonators, with the emphasis on rectangular co-axial line resonators with a round center conductor. The basic definition of the coupling coefficient is revisited and it is calculated using the method based on Bethe's theory and Cohn's experimental work. A 4th-order co-axial resonator filter operating at 3 GHz is designed using the theory outlined in this thesis. The measured response is in good agreement with the theory in terms of the center frequency, but disagree in terms of the coupling coefficient, bandwidth and Q-factor. The reasons for this, as well as suggestions for improving the accuracy of the parameters mentioned, are given. / AFRIKAANSE OPSOMMING: Sleutelwoorde: Gekoppelde resoneerder filters, Ko-aksiale lyn resoneerders, Basiese Koppeling Ontwerp, Ko-aksiale resoneerder filter Die studie van die basies dinamika van filters, met die klem op gekoppelde resoneerder filters, is voorgelê. Spesiale aandag is gegee aan die sintese van dubbelbelaste koppel matrikse met die gebruik van die Darlington metode. As gevolg van die beperkings wat op die filter geplaas word deur die gebruik van die ekwivalent stroombaan, word 'n koppel matriks vermindering gebruik. 'n Ondersoek is gedoen op A/2 ko-aksiale lyn resoneerders, met die klem op reghoekige ko-aksiale lyn resoneerders met 'n ronde binnegeleier. Die basiese definisie van die koppel koëffisiënt is hersien en dit is bereken met die gebruik van die metode wat baseer is op Bethe se teorie en Cohn se experimentele werk. 'n 4de-orde ko-aksiale resoneerder filter wat opereer by 3 GHz is ontwerp met die gebruik van die teorie wat in hierdie tesis gaskets word. Die gemete weergawe is in goeie ooreenkoms met die teorie in terme van die senter frekwensie, maar verskil in terme van die koppel koëffisiënt, bandwydte en Q-faktor. Die rede hiervoor, as ook voorstelle vir die verbetering van die akkuraatheid van die parameters wat genoem is, IS gegee.

Thesis (MScEng) -- Stellenbosch University, 2003. / ENGLISH ABSTRACT: The video-based computer vision patient positioning system that is being developed at iThemba Laboratories, relies on the accurate, robust location, identification and tracking of a number of markers on the patient's mask. The precision requirements are demanding - a small error in the location of the markers leads to an inaccurate positioning of the patient, which could have fatal consequences. In this thesis we discuss the contsruction of suitable markers, their identification with subpixel accuracy, as well as a robust tracking algorithm. The algorithms were implemented and tested on real data. We also note and give examples of other applications, most notably 2D human face tracking and the 3D tracking of a moving person. / AFRIKAANSE OPSOMMING: Die video-gebaseerde rekenaarvisie pasiënt posisionerings stelsel wat by iThemba Laboratoriums ontwikkel word, maak staat op die akkurate opsporing, identifikasie en volging van 'n stel merkers op die pasiënt se masker. Die akkuraatheids voorwaardes is besonders streng - selfs 'n klein fout in die lokasie vandie merkers sal lei tot die onakkurate posisionering van die pasiënt, wat dodelike gevolge kan hê. In hierdie tesis bespreek ons die konstruksie van geskikte merkers, die identifikasie van die merkers tot op subbeeldingselement vlak en ook die akkurate volging van die merkers. Die algoritmes is op regte data getoets. Ander toepassings soos 2D en 3D menlike gesigs-volging word ook kortliks bespreek.

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Handwritten signatures are provided extensively to verify identity for all types of transactions and documents. However, they are very rarely actually verified. This is because of the high cost of training and employing enough human operators (who are still fallible) to cope with the demand. They are a very well known, yet under-utilised biometric currently performing far below their potential. We present an on-line/dynamic handwritten signature verification system based on Hidden Markov Models, that far out performs human operators in both accuracy and speed. It uses only the local signature features-sampled from an electronic writing tablet-after some novel preprocessing steps, and is a fully automated system in that there are no parameters that need to be manually fine-tuned for different users. Novel verifiers are investigated which attain best equal error rates of between 2% and 5% for different types of high quality deliberate forgeries, and take a fraction of a second to accept or reject an identity claim on a 700 MHz computer. / AFRIKAANSE OPSOMMING: Geskrewe handtekeninge word gereeld gebruik om die identiteit van dokumente en transaksies te bevestig. Aangesien dit duur is in terme van menslike hulpbronne, word die integrit eit daarvan selde nagegaan. Om handtekeninge deur menslike operateurs te verifieër. is ook feilbaar-lOO% akkurate identifikasie is onrealisties. Handtekeninge is uiters akkurate en unieke identifikasie patrone wat in die praktyk nie naastenby tot hul volle potensiaal gebruik word nie. In hierdie navorsing gebruik ons verskuilde Markov modelle om dinamiese handtekeningherkenningstelsels te ontwikkel wat, in terme van spoed en akkuraatheid heelwat meer effektief as operateurs is. Die stelsel maak gebruik van slegs lokale handtekening eienskappe (en verwerkings daarvan) soos wat dit verkry word vanaf 'n elektroniese skryftablet. Die stelsel is ten volle outomaties en geen parameters hoef aangepas te word vir verskillende gebruikers nie. 'n Paar tipes nuwe handtekeningverifieërders word ondersoek en die resulterende gelykbreekpunt vir vals-aanvaardings- en vals-verwerpingsfoute lê tussen 2% en 5% vir verskillende tipes hoë kwaliteit vervalsde handtekeninge. Op 'n tipiese 700 MHz verwerker word die identiteit van 'n persoon ill minder as i sekonde bevestig.