Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: One of the problems with any deep space communication system is that information may be altered or lost during transmission due to channel noise. It is known that any damage to the bit stream may lead to objectionable visual quality distortion of images at the decoder. The purpose of this thesis is to design an error correction and data compression algorithm for image protection, which will allow the communication bandwidth to be better utilized. The work focuses on Sunsat (Stellenbosch Satellite) images as test images. Investigations were done on the JPEG 2000 compression algorithm's robustness to random errors, putting more emphasis on how much of the image is degraded after compression. Implementation of both the error control coding and data compression strategy is then applied to a set of test images. The FEe algorithm combats some if not all of the simulated random errors introduced by the channel. The results illustrates that the error correction of random errors is achieved by a factor of 100 times (xl00) on all test images and that the probability of error of 10-2in the channel (10-4for image data) shows that the errors causes little degradation on the image quality. / AFRIKAANSE OPSOMMING: Een van die probleme met kommunikasie in die ruimte is dat informasie mag verlore gaan en! of gekorrupteer word deur ruis gedurende versending deur die kanaal. Dit is bekend dat enige skade aan die bisstroom mag lei tot hinderlike vervorming van die beelde wat op aarde ontvang word. Die doel van hierdie tesis om foutkorreksie en datakompressie te ontwikkel wat die satelliet beelde sal beskerm gedurende versending en die kommunikasie kanaal se bandwydte beter sal benut. Die werk fokus op SUNSAT (Stellenbosch Universiteit Satelliet) se beelde as toetsbeelde. Ondersoeke is gedoen na die JPEG2000 kompressie algoritme se bestandheid teen toevalsfoute, met klem op hoeveel die beeld gedegradeer word deur die bisfoute wat voorkom. Beide die kompressie en die foutkorreksie is ge-implementeer en aangewend op die toetsbeelde. Die foutkorreksie bestry die gesimuleerde toevalsfoute, soos wat dit op die kanaal voorkom. Die resultate toon dat die foutkorreksie die toevalsfoute met 'n faktor 100 verminder, en dat 'n foutwaarskynlikheid van 10-2 op die kanaal (10-4 op die beelddata) weinig degradering in die beeldkwaliteit veroorsaak.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: An antenna for ground level deployed Ground Penetrating Radar applications is presented. The antenna is matched to the ground via a low impedance dielectric matching section improving the radiation pattern and input impedance characteristics. A bowtie antenna was used for the design with the edges rounded to stabilize the resonant frequency. The radiation pattern was focused to the one side of the antenna for ground penetration using a non-absorptive metallic cylindrical air filled cavity. Edge reflections from the antenna were reduced by means of discrete resistor terminations between the antenna and the cavity. A wire equivalent of the solid metallic antenna was investigated giving similar characteristics to that of the solid antenna. The radiation pattern deformation arising from transmitting a wave from an antenna in air into the ground due to the impedance mismatch was investigated. This was overcome with the use of a polypropylene dielectric slab inserted between the antenna and the ground. Together with improving the radiation pattern the antenna was less sensitive to ground parameter variations and to an air gap introduced between the slab and the ground. This was implemented as a wheel mounted system with adjustable height settings depending on the terrain. A pair of mounted antennas was constructed to be tested on an existing bistatic Stepped Frequency Continuous Wave radar operating in the 50-400 MHz band developed by the University of Cape Town. This antenna is seen as providing a solution to the problem of coupling an antenna to a low wave impedance medium such as ground. / AFRIKAANSE OPSOMMING: 'n Antenne word vir Grond Penetrerende Radar toepassings voorgestel. Dit is spesifiek ontwikkel vir oppervlak ontplooide stelsels ontwerp. Die antenne is aangepas tot die grond deur middel van 'n diëlektriese aanpassingseksie wat die starlingspatroon en intree-impedansie karakteristieke verbeter. Die antenne is tot die grond toe aangepas deur middel van 'n diëlektriese aanpassingseksie wat die starlingspatroon en intree-impedansie karakteristieke verbeter. 'n Strikdas antenne was gebruik vir die ontwerp, met die kante gerond om die resonante freqwensie te stabiliseer. Om die stralingspatroon van die antenne na een kant toe te fokus was 'n nie-absorbeerede metaleiese, luggevulde, silindriese holte daaragter geplaas om die energie vorentoe te weerkaats. Weerkaatsings van die rand van die antenne word onderdruk met behulp van koppelende weerstande tussen die antenne en die holte. A draad ekwivalent van die antenne was ook ondersoek met goeie ooreenstemming met die soliede strikdas. Die impedansie wanaanpassing wat ontstaan as 'n antenne wat in lug is, in die grond in straal veroorsaak dat die stralingspatroon van die antenne vervorm word. Dit was gevind dat deur 'n aanpassings blad van 'n diëlektriese materiaal, naamlik polipropileen, gebruik te maak tussen die antenne en die grond dat dit die probleem oplos. Saam met dit was gevind dat die antenne minder sensitief was vir veranderings in grondparameters en ook vir 'n lug gaping tussen die blad en die grond. Die het gemaak dat die antenne op wiele gemonteer kon word met verstelbare hoogte afhangend van die terrein. 'n Stel geskaleerde antennes was gemaak om op 'n beskikbare bistatiese Trap Frekwensie Kontinue Golf radar te werk. Dit werk oor die 50-400 MHz band en was ontwikkel deur die Universitiet van Kaapstad. Die antenne word gesien as 'n oplossing vir antenne koppelingsprobleme ondervind by laë golf impedansie materiale.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: This thesis describes various software technologies implemented, or specifically developed, for the SUNSAT micro-satellite mission. With the discussion centered on the Mission Operations System functions of Data Handling and Mission Control, particular emphasis is placed on data processing aspects such as the deployed database schema, and the data communications mechanisms implemented as part of the communications protocol stack. Both the groundsystem architecture and the Flight Software are discussed, their constituent components are analysed, and recommendations are made for improvement. Finally, a Unified Information Model for the design and operation of future, integrated satellite groundsystems is proposed, with suitable implementation technologies being identified and introduced. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die sagteware tegnologieë wat qeirnpternenteer. of spesifiek ontwerp is vir die SUNSAT mikro-satelliet missie, Met die bespreking gefokus op die Missie Operasionele Stelsel funksies van Data Hantering en Missie Beheer, word daar veral klem gelê op data prosesserings aspekte, soos byvoorbeeld die databasis skema wat ontplooi is, asook die data kommunikasie meganismes wat qeimplernenteer is as deel van die kommunikasie protokol stapel. Beide die grondstelsel argitektuur en die Vlugsagteware word bespreek, hulonderskeie komponente word geanaliseer, en aanbevelings ter verbetering word gemaak, Laastens word daar 'n Verenigde Informasie Model voorgestel vir die ontwerp en operasionele werking van 'n toekomstige, qeinteqreerde satelliet grondstelsel. Geskikte tegnologieë vir die implementasie hiervan word ook qeidentifiseer en voorgelê,

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The application of artificial neural networks to microwave circuits is investigated. A neural network model is developed for two parallel waveguides coupled by a longitudinal slot in the common broad wall. Training data is generated through a moment method solution of the integral equations that describe the structure. A systematic investigation of training options is carried out and the development of the model is described in detail. The model is evaluated and compared with an Adaptive Sampling Interpolation (ASI) Technique. The neural network is found to be less accurate than the ASI Technique at a much greater expense of development time and required user supervision. / AFRIKAANSE OPSOMMING: Die toepassing van neurale netwerke op mikrogolfbane is ondersoek. In Neurale netwerk-model is ontwikkel vir twee parallelle golfleiers met longitudinale gleufkoppeling in die gemeenskaplike bree wand. Data vir die opleiding van die netwerke is verkry deur In momentmetode-oplossing van die integraalvergelykings wat die struktuur beskryf. Verskillende ontwerpsopsies vir die netwerke is stelselmatig ondersoek en die ontwikkelingsproses van die netwerk is volledig beskryf. Die model is geevalueer en vergelyk met In Aanpasbare Monstering Interpolasietegniek (AMI). Daar is gevind dat die neurale netwerk minder akkuraat is as die AMI terwyl die koste aan ontwikkelingstyd en gebruikerstoesig hoer is.

Thesis (MScEng)--University of Stellenbosch, 2001, / ENGLISH ABSTRACT: A frequency domain Power Line Carrier (PLC) simulation program, with the ability to simulate signal attenuation including the coupling equipment, was developed. This simulation program was put to the test against the independent program of Professor L.M. Wedepohl and against practical field measurements. The predictions of the two programs were in precise agreement for a wide range of input parameters. Results from the field tests and predictions also showed close agreement. Further investigations, applying the simulation program, explained how ground conductors and soil resistivity influences PLC signal propagation. An experiment, which was developed to monitor PLC signal attenuation, was installed on the PLC system between Koeberg power station and Acacia substation, both near Cape Town. Data logged continuously over 28 days, indicated measurable and deterministic PLC signal attenuation variations with typical time constants of a few hours. Simulations of the PLC system indicated that the signal amplitude variations were influenced by changes in the height above the ground plane of the phase conductor. This significant finding creates the possibility to obtain real time knowledge of the sag of an Over Head Transmission Line (OHTL) by exploiting an operational PLC system. The knowledge about real time sag can be used in economical dynamic ampacity control systems. The practical and financial benefits to the electricity supply and distribution industry can be significant. / AFRIKAANSE OPSOMMING: 'n Frekwensie gebied "Power Line Carrier" (PLC) simulasie program wat die sein verswakking en die koppeling verliese kan naboots, is ontwikkel. Die program is getoets teen die onafhanklike program van Professor L.M. Wedepohl asook praktiese metings in die veld. Die vooruitskatings van beide programme is presies die selfde vir 'n wye reeks van parameters. Metings en nabootsings het ook noue ooreenstemming getoon. Verdere ondersoek, m. b. v. die program, is gedoen ten einde te verduidelik hoe grond-geleiers en grond weerstand die PLC sein se voortplanting beïnvloed. 'n Eksperiment om die PLC sein se verswakking mee te monitor is ontwerp. Die eksperiment was geïnstalleer in die PLC stelsel tussen Koeberg kernkragstasie en Acacia substasie, naby Kaapstad. Die eksperiment was vir 28 dae geaktiveer en die data wat die eksperiment opgelewer het toon meetbare PLC sein verswakking met tyd konstantes van 'n paar uur. Verdere nabootsings het gewys dat die veranderende verswakking in die PLC seinsterkte toegeskryf kan word aan die wisseling in hoogte van die fase geleiers bo die grondvlak. Hierdie bevinding is van besondere belang aangesien dit die moontlikheid oopmaak om die gemiddelde sak van kraglyne in reële tyd en onder bedryfs toestande te kan meet. Die informasie van die reële sak van kraglyne kan gebruik word in effektiewe stroomdrae-vermoë beheer stelsels. Die praktiese en finansiële voordele wat krag voorsieners en verspreiders hieruit kan put kan aansienlik wees.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Balanced loads such as antennas normally require baluns when they are measured. For wide band applications, designing and building a balun complicates the measurement and introduces errors. A simple model for load impedances was developed, together with a novel measurement procedure. The procedure enables the measurement of balanced loads using a network analyzer with no balun. Measured and simulated results are presented. / AFRIKAANSE OPSOMMING: Gebalanseerde laste soos antennas benodig gewoonlik balons om korrek gemeet te word. Die ontwerp van 'n balon vir wye band toepassings bemoeilik die metings en veroorsaak foute. 'n Eenvoudige model vir die lasimpedansies is ontwikkel sowel as 'n eenvoudige meetmetode. Die metode word gebruik om die gebalanseerde laste te meet met 'n netwerk analiseerder sonder die gebruik van 'n balon. Gemete en gesimuleerde resultate word getoon.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Unshielded distribution lines has a poor performance during lightning activity. Lightning initiates flashovers between the phases and earth and causes line breakers to trip several times during a lightning storm. In addition equipment like fuses, surge arresters and transformers are damaged by lightning and cause in some cases long power interruptions to customers. The application of line surge arresters on distribution lines is a solution that is implemented worldwide to limit the lightning related problems. This thesis investigated using line surge arresters in conjunction with bushing-mount fuses to decrease nuisance fusing and transformer damage during lightning activity. Two new pieces of equipment (dropout surge arresters and transformer bushingmount fuses) were developed and strategically placed on 4 different distribution lines. Equipment failures decreased by 90 % while financially the project had an excellent return on investment. / AFRIKAANSE OPSOMMING: Distribusie lyne sonder skermdrade presteer swak gedurende weerlig aktiwiteit. Weerlig veroorsaak oorvonking tussen fases en aard geleiers wat lei tot breker klinke. Transformators, sekerings, stuwingsafleiers en ander toerusting word ook deur weerlig beskadig en veroorsaak in sommige gevalle lang toevoer onderbrekings. Installering van lyn stuwingsafleiers op distribusielyne is 'n metode wat wêreldwyd gebruik word om oorvonking en weerligskade te beperk. Hierdie tesis ondersoek die installering van lyn stuwingsafleiers en deurvoerder gemonteerde sekerings om transformator skade en onnodige blaas van sekerings te beperk tydens weerlig aktiwiteit. Nuwe toerusting (uitval stuwingsafleiers en transformator deurvoerder gemonteerde sekerings) was ontwikkel en strategies op 4 verskillende distribusie lyne geïnstalleer. 'n Negentig persent vermindering in toerusting beskadiging is behaal terwyl die projek finansiël 'n goeie opbrengs op belegging meegebring het.

Thesis (MScEng)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: This report describes the development of a Java Bytecode Compiler (JBC) for the 8051 micro-controller. Bytecodes are found in the class file generated when a Java source file is compiled with the java compiler (javac). On Java platforms, the Java Virtual Machine (JVM) interprets and executes the bytecodes. Currently existing Java platforms do not support programming the 8051 using Java. As an 8-bit micro-controller with only 64 KB of total memory, the 8051's word size and memory is too limited to implement a NM. Moreover, full applications of the 8051 require that it handles hardware interrupts and access 110 ports and special registers. This thesis proposes a JBC to compile the standard bytecodes found in the class file and generate equivalent assembly code that can run on the 8051. The JBC was tested on the 8051 compatible AT89C52*44 micro-controller with a program that simulates an irrigation controller. The code generated by the JBC executes correctly but is large in size and runs slower than code of a program written in assembly. Conclusions drawn are that the JBC can be used to compile Java programs intended for the 8051 and its family of micro-controllers. In particular, it is especially a good tool for people who prefer Java to other languages. The JBC is suitable for smaller programs that do not have efficiency as a major requirement. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwikkeling van 'n Java "Bytecode" samesteller (Java Bytecode Compiler, JBC) vir die 8051 mikro beheerder argitektuur. "Bytecodes" is die produk van die standaard Java samesteller "javac" en word deur 'n platform spesifieke Java Virtuele Masjien gelees en uitgevoer. Geen NM is huidig beskikbaar vir die 8051 argitektuur nie. Die gekose 8-bis 8051 mikro beheerder het 'n beperkte interne geheue van 64kB. Hierdie beperking maak dit nie geskik vir 'n IVM nie. Daar moet ook voorsiening gemaak word om hardeware onderbrekings te hantering en te kan kommunikeer met die poorte en spesiale registers van die mikro beheerder. JBC word ontwikkel wat die standaard "Bytecode" kompileer na geskikte masjien kode wat dan op die mikro beheerder gebruik kan word. Die JBC is ontwikkel en toets en 'n eenvoudige besproeiing program is geskryf om op 'n Atmel AT89C52*44 te loop. Die kode werk goed maar is nog nie geoptimeer nie en loop onnodig stadig. Optimerings metodes word aanbeveel en bespreek. Die gevolgtrekking is dat die huidige JBC kan gebruik word om Java kode te skryfvir die 8051 beheerder. Dit maak die hardeware platform nou beskikbaar aan Java programmeerders. Daar moet wel gelet word dat die JBC op die oomblik net geskik is vir klein programme en waar spoed nie die primêre vereiste is nie.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The topic of this thesis is speaker adaptation, whereby speaker-independent speech models are adapted to more closely match individual speakers by utilising a small amount of data from the targeted individual. Speaker adaptation methods - specifically, the MAP, MLLR and MLED speaker adaptation methods - are critically evaluated and compared. Two novel extensions of the MLED adaptation method are introduced, derived and evaluated. The first incorporates the explicit modelling of the mean speaker model in the speaker-space into the MLED framework. The second extends MLED to use basis vectors modelling inter-class variance for classes of speech models, instead of basis vectors modelling inter-speaker variance. An evaluation of the effect of two different types of feature vector - PLP-cepstra and LPCCs - on the performance of speaker adaptation is made, to determine which feature vector is optimal for speaker-independent systems and the adaptation thereof. / AFRIKAANSE OPSOMMING: Die onderwerp van hierdie tesis is spreker-aanpassing, dit wil sê, die verandering van 'n spreker-onafhanklike spraakmodel om nader aan 'n spreker-afhanklike model vir 'n individu te wees, gegewe 'n klein hoeveelheid spraakdata van die individu. Die volgende sprekeraanpassing-metodes word geëvalueer: MAP, MLLR en MLED. Twee nuwe uitbreidings vir die MLED-metode word beskryf, afgelei en geëvalueer. Die eerste inkorporeer die eksplisiete modellering van die gemiddelde sprekermodel van die sprekerruimte in die MLED metode. Die tweede uitbreiding maak gebruik van basisvektore vir MLED wat vanaf die interklas-variansie tussen 'n stel sprekerklasse in plaas van die interspreker-variansie afgelei is. Die effek van twee tipes kenmerk-vektore - PLP-kepstra en LPCC's - op die prestasie van sprekeraanpassings-metodes word ondersoek, sodat die optimale tipe kenmerk-vektor vir spreker-onafhanklike modelle en hul aanpassing gevind kan word.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The purpose of this thesis was to design and test the interfaces of sensors and actuators. In the complete Attitude Determination and Control System CADCS) the Interface Control Processor (ICP) must be interfaced to various sensors and torquers. The testing of interfaces involves the simulation of sensors and actuators and also two of the Attitude Control Processor's functions, i.e. sending actuator commands and receiving sensor data. The tested interfaces are for two actuators and three sensors. Both analog and digital sensors and actuators are interfaced i.e. reaction wheels, magnetorquers, magnetometer and horizon /fine sun sensor. The simulated sensors and actuators are to be employed on three axis controlled, low earth o~biting micro-satellites. To test the interfaces, a test circuit was developed and the design is presented. Finally the software to facilitate the testing was developed and is also presented with the analysis based on protocol implementation and data rates. / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis was om sensor en aktueerder koppelvlakke te ontwerp en te toets. In die volledige Attitude Determination and Control System CADCS) moet die Interface Control Processor CICP) aan verskeie sensore en torquers gekoppel word. Die toets van koppelvlakke behels die simulasie van sensore en aktueerders en ook twee van die Attitude Control Processor (ACP) se funksies, naamlik die stuur van aktueerder bevele en die ontvang van sensor data. Die koppelvlakke vir twee aktueerders en drie sen sore is getoets. Beide analoog en digitale sensore en aktueerders is gekoppel, naamlik die reaksiewiele, magneetspoele, magnetometer en horison I fyn son sensor. Die gesimuleerde sensore en aktueerders sal gebruik word op drie-as beheerde, lae aardbaan mikrosatelliete. Om die koppelvlakke te toets is 'n stroombaan ontwikkel waarvan die ontwerp hier aangebied word. Sagteware om die toetse te fasiliteer is ontwikkel en word ook hier aangebied tesame met . analises gebaseer op protokol implementering en data tempo's.