Thesis (MScIng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The purpose of this study was to develop a Global Positioning System (GPS) receiver for use on a Low-Earth Orbit (LEO) satellite. The study includes an examination of some of the fundamental GPS theory and how the LEO environment affects the operation of a GPS receiver. The hardware and software that was selected for the implementation are discussed. The reasons for porting the software to a new hardware platform and methods employed in the port are given. Thereafter the process of adapting the receiver software for use in space is given. To verify the operation in space, the receiver was subjected to LEO simulations using a GPS signal simulator. These results are shown and discussed. The tests indicated that the adaptations were successful and that the receiver will function on a LEO satellite. / AFRIKAANSE OPSOMMING: Die doel van die tesis was om ’n Globale Posisionerings Stelsel (GPS) ontvanger to ontwikkel vir gebruik op ’n lae-wentelbaan satelliet. Die studie begin met fundamentele GPS teorie en hoe die funksionering van die ontvanger be¨ınvloed word deur die wentelbaan van ’n satelliet. Die hardeware en sagteware vir die implementasie word bespreek. Die rede en metodes om die sagteware aan te pas om te werk op nuwe hardeware word gegee. Daarna word die proses om die sagteware aan te pas vir ruimtegebruik gegee. Om the verifieer dat die ontvanger wel sal kan werk op ’n satelliet was dit getoets in ’n gesimuleerde ruimte-omgewing met ’n GPS seinsimulator. Hierdie resultate word gegee en bespreek. Die toetse het gewys dat die aanpassings suksesvol was en dat die ontvanger in die ruimte sal funksioneer.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / This thesis investigates to the design, analysis and testing of a Superconducting Programmable Gate Array (SPGA). The objective was to apply existing programmable logic concepts to RSFQ circuits and in the process develop a working prototype of a superconducting programmable logic device. Various programmable logic technologies and architectures were examined and compared to find the best solution. Using Rapid Single Flux Quantum (RSFQ) circuits as building blocks, a complete functional design was assembled incorporating a routing architecture and logic blocks. The Large-Scale Integrated circuit (LSI) layout of the final chip is presented and discussed followed by a discussion on testing. This thesis demonstrates the successful implementation of a fully functional reprogrammable logic device using RSFQ circuitry.

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Spoken dialogue systems accessed over the telephone network are rapidly becoming more popular as a means to reduce call-centre costs and improve customer experience. It is now technologically feasible to delegate repetitive and relatively simple tasks conducted in most telephone calls to automatic systems. Such a system uses speech recognition to take input from users. This work focuses on the speech generation component that a specific prototype system uses to convey audible speech output back to the user. Many commercial systems contain general text-to-speech synthesisers. Text-to-speech synthesis is a very active branch of speech processing. It aims to build machines that read text aloud. In some languages this has been a reality for almost two decades. While these synthesisers are often very understandable, they almost never sound natural. The output quality of synthetic speech is considered to be a very important factor in the user’s perception of the quality and usability of spoken dialogue systems. The static nature of the spoken dialogue system is exploited to produce a custom speech synthesis component that provides very high quality output speech for the particular application. To this end the current state of the art in speech synthesis is surveyed and summarised. A unit-selection synthesiser is produced that functions in Afrikaans, English and Xhosa. The unit-selection synthesiser selects short waveforms from a recorded speech corpus, and concatenates them to produce the required utterances. Techniques are developed for designing a compact corpus and processing it to produce a unit-selection database. Speech modification methods were researched to build a framework for natural-sounding speech concatenation. This framework also provides pitch and duration modification capabilities that will enable research in languages such as Afrikaans and Xhosa where text-to-speech capabilities are relatively immature. / AFRIKAANSE OPSOMMING: Telefoniese, spraakgebaseerde dialoogstelsels word steeds meer algemeen, en is ’n doeltreffende metode om oproepsentrumkostes te verlaag. Dit is tans tegnologies moontlik om ’n groot aantal eenvoudige transaksies met automatiese stelsels te hanteer. Sulke stelsels gebruik spraakherkenning om intree van die gebruiker te ontvang. Hierdie werk fokus op die spraakgenerasiekomponent wat ’n spesifieke prototipestelsel gebruik om afvoer aan die gebruiker terug te speel. Vele kommersi¨ele stelsels gebruik generiese teks-na-spraak sintetiseerders. Sulke teksna- spraak sintetiseerders is steeds ’n baie aktiewe veld in spraaknavorsing. In die algemeen poog navorsing om teks te kan lees en om te sit in verstaanbare spraak. Sulke stelsels bestaan nou al vir ten minste twee dekades. Alhoewel heeltemal verstaanbaar, klink hierdie stelsels onnatuurlik. In telefoniese spraakgebaseerde dialoogstelsels is kwaliteit van die sintetiese spraak belangrik vir die gebruiker se persepsie van die stelsel se kwaliteit en bruikbaarheid. Die dialoog is meestal staties van aard en hierdie eienskap word benut om ho¨e kwaliteit spraak in ’n bepaalde toepassing te sintetiseer. Om dit reg te kry is die huidige stand van sake in hierdie veld bestudeer en opgesom. ’n Knip-en-plak sintetiseerder is gebou wat werk in Afrikaans, Engels en Xhosa. Die sintetiseerder selekteer kort stukkies spraakgolfvorms vanuit ’n spraakkorpus, en las dit aanmekaar om die vereiste spraak te produseer. Outomatiese tegnieke is ontwikkel om ’n kompakte korpus te ontwerp wat steeds alles bevat wat die sintetiseerder sal nodig hˆe om sy taak te verrig. Verdere tegnieke prosesseer die korpus tot ’n bruikbare vorm vir sintese. Metodes van spraakmodifikasie is ondersoek ten einde die aanmekaargelaste stukkies spraak meer natuurlik te laat klink en die intonasie en tempo daarvan te korrigeer. Dit verskaf infrastruktuur vir navorsing in tale soos Afrikaans en Xhosa waar teks-na-spraak vermo¨ens nog onvolwasse is.

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Data capturing equipment are an expensive part of testing the coverage of a deployed or planned wireless service. This thesis presents the development of such a data capturing system that make use of 1800MHz GSM base stations as transmitters and a mobile phone connected to a laptop as receiver. The measurements taken, are then verified against know propagation models. Datavaslegging toerusting wat gebruik word om die dekking van draadlose stelsels te toets is baie duur en moeilik bekombaar. Hierdie tesis beskryf die ontwikkeling van so ’n datavaslegger wat baie goedkoper is en maklik gebruik kan word. Dit maak gebruik van ’n sellulêr foon en GPS gekoppel aan ’n skootrekenaar, wat die ontvanger is. Cell C basis staties word gebruik as die senders. Die data wat gemeet is word dan geverifieer deur gebruik te maak van bestaande radio frekwensie voortplanting modelle.

Thesis (MScIng)--University of Stellenbosch, 2004. / Please refer to full text for abstract.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2003. / Ground penetrating radar is currently proving itself as an invaluable tool for the prediction of geological structures in the mining environment. Borehole radar is a specific application of this technology, useful in the prediction of the course of rock layers between boreholes ahead of mining. Establishing borehole radar as an industrial tool requires a system that is more userfriendly and easier to deploy than the bi-static radar systems currently available. The development of a monostatic radar system is discussed. It is an ultra wide band, pulse radar system that operates at VHF (10-100 MHz). The system is required to detect reflections from objects 5 m away and further. This translates to a total electromagnetic propagation time of approximately 100 ns or more in the rock medium. The complete design process - from fundamental requirements, through a conceptual design, to a final electronic circuit - is discussed. The design is also built, measured in the laboratory and taken for initial field trails. The following aspects are considered: • Pulse generation by means of an original circuit based on power MOSFETs. • Routing of the transmitted- and received signal between transmitter, receiver and antenna. This is done using a novel, active quasi circulator topology. • Methods of increasing isolation (actively and passively) between transmitter and receiver. • Interfacing with a specific receiver, antenna and data acquisition system.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Spoornet is one of South-Africa’s largest railway companies. It is very important to operate the railway system as cost effectively as possible. A large portion of the railway operates from 3 kV DC traction supplies. One method of cost saving is to utilise the regenerative braking mechanism of the electric trains.

Thesis (MScIng)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Keywords: digital signal processing, OSI layer, network protocols, embedded systems, satellite technology This thesis describes the design and implementation of a rural e-mail system for the Sumbandila satellite. The rural e-mail system was developed during a project sponsored by the Department of Communications of the South African government. The complete Open Systems Interconnect (OSI) layer structure of the protocol architecture used on the satellite hardware and software is described. The equivalent implementation of the OSI layer on the ground station hardware is given. This includes the adaptation of the soundmodem Open Source Software modem to work for the e-mail system’s OSI layer. The design of the Application Layer e-mail system is described and the implementation of this design using the Python, Korn Shell and C programming environments is also given. The procedures used to test the system for reliability and the use of a database to create detailed logs of the e-mail system is shown to have generated a reliable system that is easily maintained. A critical evaluation of the system is provided in the last chapter. / AFRIKAANSE OPSOMMING: Sleutelwoorde: Syferseinverwerking, OSI-lae, netwerkprotokolle, toegewyde stelsels, satelliettegnologie Hierdie tesis beskryf die ontwerp en implementering van ’n plattelandse e-posstelsel vir die Sumbandila satelliet. Die plattelandse e-posstelsel is ontwikkel in opdrag van die Departement van Kommunikasie van die Suid-Afrikaanse regering. Die volledige Open Systems Interconnect (OSI) laagstruktuur van die protokol-argitektuur wat in die satelliet se apparatuur en programmatuur gebruik is, word beskryf. Die ekwivalente implementering van die OSI-laag op die grondstasie-apparatuur word gegee, insluitende die aanpassing van soundmodem, ’n oopbronkode sagteware-modem. Hierdie sagteware-modem word gebruik in die e-posstelsel se fisiese laag. Die ontwerp van die toepassingslaag van die e-posstelsel word beskryf, asook die implementering van hierdie ontwerp met behulp van Python, die Korninterpreteerder en C. Die prosedures waarvolgens stelselbetroubaarheid getoets is, en die gebruik van ’n databasis om noukeurige joernale van e-postransaksies te hou, demonstreer dat ’n betroubare, onderhoubare stelsel gemplementeer is. In die laaste hoofstuk word die stelsel krities geevalueer.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. / Position calculation of mobile objects has challenged engineers and designers for years and is still continuing to do so. There are many solutions available today. Probably the best known and most widely used outdoor system today is the Global Positioning System (GPS). There are very little systems available for indoor use. An absolute positioning system was developed for this thesis. It uses a combination of ultrasonic and Radio Frequency (RF) communications to calculate a position fix in doors. Radar techniques were used to ensure robustness and reliability even in noisy environments. A small mobile robot was designed and built to test and illustrate the use of the system.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Rapid Single Flux Quantum (RSFQ) cells are key in the design of complex and applicable RSFQ electronic circuits. These cells are low-level circuit elements that are used repeatedly to build larger, applicable RSFQ circuitry. Making these cells simple to layout and manufacture, but reliable for extensive use demands a careful development process for RSFQ cells. Cell functionality is verified through simulations, thereafter the cell is laid out in special software packages. Inductance of on-chip superconductor structures is extracted through careful modelling with numerical field solver software. A cell library has been developed by incorporating existing or published cells after further analysis and optimization, as well as developing new cells. Cells that have been adapted into the library include the Josephson transmission line (JTL), Splitter, Merger, D-Flip Flop (DFF), T-Flip Flop (TFF), NOT, AND, OR and XOR, DC-SFQ and SFQ-DC and PTL Driver and Receivers. New cells include NOR, NAND and XNOR. The cells were designed for the IPHT’s RSFQ1D 1kA/cmª and Hypres’ 4.5kA/cmª processes. The cells in the library have good bias current operating margins obtained through simulations (> ±26%). All cells have all the parameters listed in the thesis including extracted inductance values. In order to have a complete and verified RSFQ cell library, cells have been sent for fabrication at IPHT and Hypres facilities. These cells can now be tested on-chip, in the laboratory, to establish functionality and practical bias current margins. All test signal patterns and bias currents required for testing are defined to allow co-workers or collaborators to test the cells. / AFRIKAANSE OPSOMMING: "Rapid Single Flux Quantum" (RSFQ) selle is van sleutelbelang in die ontwerp van komplekse en toepaslike RSFQ elektroniese stroombane. Hierdie selle is laevlak stroombaanelemente wat herhaaldelik gebruik word om groter RSFQ bane mee te bou. Versigtige ontwikkeling is nodig om hierdie selle eenvoudig vir uitleg en vervaardiging te hou terwyl dit ook betroubaar is vir wye gebruik. Selfunksionaliteit word geverifieer deur middel van simulasies, waarna selle vir vervaardiging uitgelê word in spesiale sagtewarepakette. Induktansie van supergeleierstrukture op vervaardigde skyfies word deur versigtige modellering met behulp van numeriese veldoplossingsagteware onttrek. In hierdie tesis is ’n selbiblioteek ontwerp deur bestaande (gepubliseerde) selle verder te analiseer en optimeer, en deur nuwe selle te ontwerp om die biblioteek volledig te maak. Selle wat aangepas is vir hierdie biblioteek sluit die Josephson-Transmissielyn (JTL), Verdeler, Samevoeger, DWipkring (DFF), T-Wipkring (TFF), NIE, EN, OF en XOF, asook die DC-SFQ en SFQ-DC selle en Passiewe Transmissielyn (PTL) drywers en ontvangers in. Nuwe selle sluit die NOF, NEN en XNOF hekke in. Die selle is ontwerp en uitgelˆe vir beide IPHT se RSFQ1D 1kA/cmª en Hypres se4.5kA/cmª prosesse. Die selle in die biblioteek toon goeie voorspanningstroom-werksmarges, soos verkry deur simulasie (> ±26%). Parameters en berekende induktansies vir alle selle word in die tesis gelys vir naslaandoeleindes. Vir die daarstel van ’n volledige en geverifieerde RSFQ selbiblioteek is selontwerpe vir vervaardiging na IPHT en Hypres gestuur. Aangesien vervaardiging slegs een maal per jaar by IPHT gedoen word, is die skyfies egter nog nie beskikbaar nie. Na vervaardiging kan die skyfies egter getoets word om selfunksionaliteit in die laboratorium te meet. Ten einde hierdie toetsing vir enige medewerker te vergemaklik, word alle toetsparameters soos voorspanningstroom en intreeseinpatrone in die tesis gedefinieer.