Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: This work considers the acceleration of matrix-based computational electromagnetic (CEM) techniques using graphics processing units (GPUs). These massively parallel processors have gained much support since late 2006, with software tools such as CUDA and OpenCL greatly simplifying the process of harnessing the computational power of these devices. As with any advances in computation, the use of these devices enables the modelling of more complex problems, which in turn should give rise to better solutions to a number of global challenges faced at present. For the purpose of this dissertation, CUDA is used in an investigation of the acceleration of two methods in CEM that are used to tackle a variety of problems. The first of these is the Method of Moments (MOM) which is typically used to model radiation and scattering problems, with the latter begin considered here. For the CUDA acceleration of the MOM presented here, the assembly and subsequent solution of the matrix equation associated with the method are considered. This is done for both single and double precision oating point matrices. For the solution of the matrix equation, general dense linear algebra techniques are used, which allow for the use of a vast expanse of existing knowledge on the subject. This also means that implementations developed here along with the results presented are immediately applicable to the same wide array of applications where these methods are employed. Both the assembly and solution of the matrix equation implementations presented result in signi cant speedups over multi-core CPU implementations, with speedups of up to 300x and 10x, respectively, being measured. The implementations presented also overcome one of the major limitations in the use of GPUs as accelerators (that of limited memory capacity) with problems up to 16 times larger than would normally be possible being solved. The second matrix-based technique considered is the Finite Element Method (FEM), which allows for the accurate modelling of complex geometric structures including non-uniform dielectric and magnetic properties of materials, and is particularly well suited to handling bounded structures such as waveguide. In this work the CUDA acceleration of the cutoff and dispersion analysis of three waveguide configurations is presented. The modelling of these problems using an open-source software package, FEniCS, is also discussed. Once again, the problem can be approached from a linear algebra perspective, with the formulation in this case resulting in a generalised eigenvalue (GEV) problem. For the problems considered, a total solution speedup of up to 7x is measured for the solution of the generalised eigenvalue problem, with up to 22x being attained for the solution of the standard eigenvalue problem that forms part of the GEV problem. / AFRIKAANSE OPSOMMING: In hierdie werkstuk word die versnelling van matriksmetodes in numeriese elektromagnetika (NEM) deur die gebruik van grafiese verwerkingseenhede (GVEe) oorweeg. Die gebruik van hierdie verwerkingseenhede is aansienlik vergemaklik in 2006 deur sagteware pakette soos CUDA en OpenCL. Hierdie toestelle, soos ander verbeterings in verwerkings vermoe, maak dit moontlik om meer komplekse probleme op te los. Hierdie stel wetenskaplikes weer in staat om globale uitdagings beter aan te pak. In hierdie proefskrif word CUDA gebruik om ondersoek in te stel na die versnelling van twee metodes in NEM, naamlik die Moment Metode (MOM) en die Eindige Element Metode (EEM). Die MOM word tipies gebruik om stralings- en weerkaatsingsprobleme op te los. Hier word slegs na die weerkaatsingsprobleme gekyk. CUDA word gebruik om die opstel van die MOM matriks en ook die daaropvolgende oplossing van die matriksvergelyking wat met die metode gepaard gaan te bespoedig. Algemene digte lineere algebra tegnieke word benut om die matriksvergelykings op te los. Dit stel die magdom bestaande kennis in die vagebied beskikbaar vir die oplossing, en gee ook aanleiding daartoe dat enige implementasies wat ontwikkel word en resultate wat verkry word ook betrekking het tot 'n wye verskeidenheid probleme wat die lineere algebra metodes gebruik. Daar is gevind dat beide die opstelling van die matriks en die oplossing van die matriksvergelyking aansienlik vinniger is as veelverwerker SVE implementasies. 'n Verselling van tot 300x en 10x onderkeidelik is gemeet vir die opstel en oplos fases. Die hoeveelheid geheue beskikbaar tot die GVE is een van die belangrike beperkinge vir die gebruik van GVEe vir groot probleme. Hierdie beperking word hierin oorkom en probleme wat selfs 16 keer groter is as die GVE se beskikbare geheue word geakkommodeer en suksesvol opgelos. Die Eindige Element Metode word op sy beurt gebruik om komplekse geometriee asook nieuniforme materiaaleienskappe te modelleer. Die EEM is ook baie geskik om begrensde strukture soos golfgeleiers te hanteer. Hier word CUDA gebruik of om die afsny- en dispersieanalise van drie gol eierkonfigurasies te versnel. Die implementasie van hierdie probleme word gedoen deur 'n versameling oopbronkode wat bekend staan as FEniCS, wat ook hierin bespreek word. Die probleme wat ontstaan in die EEM kan weereens vanaf 'n lineere algebra uitganspunt benader word. In hierdie geval lei die formulering tot 'n algemene eiewaardeprobleem. Vir die gol eier probleme wat ondersoek word is gevind dat die algemene eiewaardeprobleem met tot 7x versnel word. Die standaard eiewaardeprobleem wat 'n stap is in die oplossing van die algemene eiewaardeprobleem is met tot 22x versnel.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: This thesis discusses the steps that should be taken when conceptualising, designing and implementing a South African national research and education network. It looks at all aspects of specifying transmission mediums and technology, choosing hardware and interfaces and detailing node layout and optic fibre network architecture. It examines the design of a national transport backbone, as well as a metropolitan optic fibre network. It considers ways in which the network may be made future-proof, both in terms of capacity and technology, and suggests ways to integrate the incumbent tertiary and education network into a fully-fledged, world-class network. Finally it benchmarks the network against similar networks in other countries, most notably the United States of America. / AFRIKAANSE OPSOMMING: Hierdie tesis bespreek die stappe wat geneem behoort te word wanneer 'n Suid Afrikaanse nasionale navorsings en tersiêre opvoedings netwerk gekonseptualiseer, ontwerp en geïmplementeer word. Dit beskou al die aspekte rondom die spesifiseering van transmissie mediums en -tegnologie, die keuse van hardeware en koppelvlakke en die detailering van nodus uitlegte en optiese vesel netwerk argitektuur. Dit ondersoek die ontwerp van 'n nasionale transmissie ruggraat netwerk, sowel as 'n metropolitaanse optiese vesel netwerk. Dit oorweeg maniere waarmee 'n netwerk toekomsproef gemaak kan word, beide in terme van kapasiteit sowel as tegnologie, en stel maniere voor waarmee die huidige tersiêre opvoeding en navorsingsnetwerk geïntegreer kan word na 'n volwaardige, wêreldklas netwerk. Uiteindelik word die netwerk ontwerp vergelyk met soortgelyke netwerke in ander lande, spesifiek in die Verenigde State van Amerika.

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.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The recent emergence of ubiquitous wireless connectivity and the increasing computational capacity of modern vehicles have triggered immense interest in the possibilities of vehicular connectivity. A plethora of potential applications for vehicular networks have been proposed in the areas of safety, traffic infrastructure management, information, and entertainment. The broad range of applications requires creative utilisation of the available wireless medium, using a combination of existing and novel wireless technologies. In this research the evaluation of one such configuration is performed. Dedicated short range communication for safety applications is assumed, and the use of Wi- Fi and WiMAX for non-safety applications is evaluated. Little is known about the media streaming performance of these wireless technologies in realistic vehicular ad-hoc network (VANET) scenarios. Due to the extreme mobility and unpredictable environmental aspects in a real road environment, an empirical evaluation is performed and presented. Evaluation of a multi-vehicle to infrastructure (V2V2I) VANET, using Wi-Fi for the vehicle-to-vehicle communication and WiMAX for the vehicle to infrastructure (V2I) communication is experimented. It is observed that Wi-Fi is unaffected by the vehicle speed; whenever nodes are within communication range, data gets transferred normally. A detailed characterisation of the network architecture is presented and the results show that a multitude of applications can be supported with this proposed network architecture. / AFRIKAANSE OPSOMMING: Die toenemende beskikbaarheid en digtheid van koordlose netwerke en die verhoogde verwerkingsvermoëns van moderne voertuie het die afgelope paar jaar aansienlike belangstelling gewek in die moontlikhede wat voertuig-kommunikasie bied. ʼn Magdom moontlike toepassings is voorgestel in ʼn wye verskeidenheid van velde insluitende veiligheid, verkeersinfrastruktuur, informasie en vermaak. Hierdie voorstelle vereis die kreatiewe benutting van die beskikbare en nuwe koordlose tegnologieë. Hierdie tesis evalueer een voorbeeld van so ‘n opstelling. ʼn Toegewyde kortafstand kommunikasie modus vir veiligheidstoepassings word aangeneem, terwyl Wi-Fi en WiMAX vir ander toepassings evalueer word. Daar is min navorsing oor die kapasiteit en seinsterkte van hierdie beskikbare netwerke onder realistiese voertuig netwerk (VANET) scenario‘s. Weens die hoë mobiliteit van voertuie en ook die onvoorspelbaarheid van hierdie omgewing word ʼn empiriese evaluasie beskou as die mees gepaste metode. Die navorsing ondersoek ʼn multi-voertuig-totinfrastruktuur- netwerk wat Wi-Fi gebruik vir voertuig-tot-voertuig (V2V) kommunikasie en WiMAX vir voertuig-tot-infrastruktuur (V2I) kommunikasie. Die navorsing bevind dat Wi-Fi nie beïnvloed word deur die spoed van die voertuig nie: wanneer die nodes binne die bereik is van die netwerk word data normaal oorgedra. ‗n Gedetailleerde karakterisering van dié netwerk word gedoen en die resultate dui aan dat ‗n groot hoeveelheid toepassings ondersteun kan word deur dié opstelling.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The Solid-State Transformer (SST) is presented as an alternative to the traditional Line-Frequency Transformer (LFT) used for voltage-level transformation in distribution grids. The LFT technology is highly matured which results in low costs and high efficiency. The SST however, introduces several advantages compared to the LFT, some of which are input unity power-factor, near perfect output-voltage regulation, frequency variation as well as harmonic filtering. The SST consists of three power-electronic converter stages: The input stage, the isolation stage and the output stage. The input and isolation stages are implemented with a multilevelconverter topology incorporating a converter-stack for each phase. Each stack consists of N converter building blocks, called cells. In this thesis the design and implementation of the main controller is presented. The main controller, together with N cell controllers, is responsible for the control of the cells within the respective stack. Three main controllers are thus implemented within the SST. Each cell consists of an Active Rectifier (AR) and a DC-DC Converter (DC-DC). The SST control design thus starts with the AR control which is subsequently expanded to Cascaded Active-Rectifier (CAR) control. Design is completed with the addition of the DC-DC control. Time domain simulations of the AR- and CAR-control are presented and discussed. Test measurements, verifying functionality of each control design-phase, are presented and discussed. / AFRIKAANSE OPSOMMING: Die Drywingselektroniese Transformator (DET) word voorgestel as ’n alternatief vir die Lyn Frekwensie Transformator (LFT) wat gebruik word vir spannings-vlak tranformasie op distribusie vlak. The LFT tegnologie is ver gevorderd wat ly tot hoë effektiwiteit en lae kostes. The DET bied wel voordele soos intree eenheids arbeid faktor, na aan perfecte uittree-spannings regulasie, frequensie variasie sovel as harmoniese filrteering. Die DET bestaan uit drie drywingselektroniese omsetter stadiums: Die intree-stadium, die isolasie-stadium en die uittree-stadium. The intree- en isolasie-stadiums word geïmplimenteer met ’n multivlak-omsetter topologie wat bestaan uit ’n omsetter-stapel vir elke fase. Elke stapel bestaan uit N omsetter boustene wat selle genoem word. In hierdie tesis word the ontwerp en implementasie van die hoofbeheerder voorgestel. Die hoofbeheerder, tesame met N selbeheerders, is verantwoordelik vir die beheer van elke sel in die spesifieke stapel. In die DET word daar dus drie hoofbeheerders gebruik. Elke sel bestaan uit ’n Aktiewe Gelykrigter (AG) en ’n GS-GS omsetter (GS-GS). Die DET beheerontwerp begin dus met die (AG) beheer wat daarna uitgebrei word na Kaskade Aktiewe Gelykrigter (KAG) beheer. Die beheer ontwerp word voltooi deur die byvoeging van die GSGS beheer. Tyd-gebied simulasies van die AG- en KAG-beheer word voorgelê en bespreek. Toetsmetings wat die funksionaliteit van elke beheer ontwepsfase verifeer, word voorgelê.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The Electronic Systems Laboratory at Stellenbosch University is currently developing a fully 3-axis controlled Attitude Determination and Control Subsystem (ADCS) for CubeSats. This thesis describes the design and development of an Onboard Computer (OBC) suitable for ADCS application. A separate dedicated OBC for ADCS purposes allows the main CubeSat OBC to focus only on command and data handling, communication and payload management. This thesis describes, in detail the development process of the OBC. Multiple Microcontroller Unit (MCU) architectures were considered before selecting an ARM Cortex-M3 processor due to its performance, power efficiency and functionality. The hardware was designed to be as robust as possible, because radiation tolerant and redundant components could not be included, due to their high cost and the technical constraints of a CubeSat. The software was developed to improve recovery from lockouts or component failures and to enable the operational modes to be configured in real-time or uploaded from the ground station. Ground tests indicated that the OBC can handle radiation-related problems such as latchups and bit-flips. The peak power consumption is around 500 mW and the orbital average is substantially lower. The proposed OBC is therefore not only sufficient in its intended application as an ADCS OBC, but could also stand in as a backup for the main OBC in case of an emergency. / AFRIKAANSE OPSOMMING: Die Elektroniese Stelsels Laboratorium by die Universiteit van Stellenbosch is tans besig om ’n volkome 3-as gestabiliseerde oriëntasiebepaling en -beheerstelsel (Engels: ADCS) vir ’n CubeSat te ontwikkel. Hierdie tesis beskryf die ontwerp en ontwikkeling van ’n aanboordrekenaar (Engels: OBC) wat gebruik kan word in ’n ADCS. ’n Afsonderlike OBC wat aan die ADCS toegewy is, stel die hoof-OBC in staat om te fokus op beheer- en datahantering, kommunikasie en loonvragbestuur. Hierdie tesis beskryf breedvoerig die werkswyse waarvolgens die OBC ontwikkel is. Verskeie mikroverwerkers is as moontlike kandidate ondersoek voor daar op ’n ARM Cortex-M3-gebaseerde mikroverwerker besluit is. Hierdie mikroverwerker is gekies vanweë sy spoed, effektiewe kragverbruik en funksionaliteit. Die hardeware is ontwikkel om so robuust moontlik te wees, omdat stralingbestande en oortollige komponente weens kostebeperkings, asook tegniese beperkings van ’n CubeSat, nie ingesluit kon word nie. Die programmatuur is ontwikkel om van ’n uitsluiting en ’n komponentfout te kan herstel. Verder kan programme wat tydens vlug in werking is, verstel word en vanaf ’n grondstasie gelaai word. Grondtoetse het aangedui dat die OBC stralingverwante probleme, soos ’n vergrendeling (latchup) of bis-omkering (bit-flip), kan hanteer. Die maksimum kragverbruik is ongeveer 500 mW en die gemiddelde wentelbaankragverbruik is beduidend kleiner. Die voorgestelde OBC is dus voldoende as ADCS OBC asook hoof-OBC in geval van nood.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This thesis addresses the complications that are encountered when characterising the performance of differential microwave LNAs. The predominant sources of noise in electronic circuits are introduced and equivalent two-port noise models for active devices are derived. Correlation between noise generators are defined by means of the noise correlation matrix and existing network theory is adapted to include noise analysis of twoport and multi-port networks. Mixed-mode scattering parameters are introduced in order to define the signal performance of differential and common-mode propagation in multi-port networks and, by applying the same theory, the mixed-mode correlation matrix for a three-port dLNA is derived. Furthermore, an expression is derived for de-embedding the differential noise figure of a three-port dLNA using two single ended measurements. Two dLNA designs, both incorporating wideband 180°-Hybrid ring couplers, are discussed and the differential signal and noise performance of the dLNAs are compared to that of their constituent single ended LNAs. / AFRIKAANSE OPSOMMING: Hierdie tesis behandel die komplikasies wat ontwerpers in die gesig staar tydens die karakterisering van mikrogolf differensiële laeruis versterkers. Die hoof ruisbronne in stroombane word bespreek en ekwivalente tweepoortnetwerkmodelle vir aktiewe toestelle word afgelei. Korrelasie tussen ruisbronne word gedefnieer deur middel van ruiskorrelasiematrikse en bestaande tweepoort- en multipoort-netwerkteorie word aangepas om ruismodelle in te sluit. Weens die feit dat differensiële- en gemene-wyse voortplanting van seine voorkom in multipoortnetwerke word gemengde-modus S-parameters behandel. Dieselfde teorie maak dit vervolgens moontlik om die gemengde-modus ruiskorrelasiematriks van ’n drie-poort differensiële laeruis versterker af te lei. Verder word daar ’n wyse voorgestel waarmee die differensiëleruissyfer van ’n drie-poort differensiële laeruis versterker vanuit twee enkel ruissyfermetings bereken kan word. Twee differensiële laeruis versterker ontwerpe, waarvan beide wyeband 180 -differensiaalkoppelaars implementeer, word bespreek en die differensiëlesein- asook die differensiëleruis-werking word vergelyk met die werking van die omsluite ongebalanseerde laeruis versterkers.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Low earth orbit (LEO) satellite communication presents a unique environment which inherently di ers from most other communication channels. Due to the varying orbital patterns of LEO satellites the link exhibits varying link margins. Limited communication time windows need to be optimised to maximise the volumetric data throughput. Large coding gains can be obtained by the implementation of forward error correction codes. This thesis presents a means for optimising the data throughput of LEO satellite communication through the implementation of a mission speci c error control strategy. Low density parity check (LDPC) codes are versatile and present good error performances at many di erent code rates and block lengths. With power limitations on the space segment and remote ground stations, hardware utilisation e ciency must be optimised to reduce power consumption. In response to this requirement, this thesis evaluates various algorithms for LDPC decoders. An iterative LDPC decoder, implementing an approximation algorithm, is presented as a low complexity solution with good error performance. The proposed solution provides a very good balance between required hardware complexity and coding performance. It was found that many parameters of the decoders and codes can be altered to allow the implementation of these codes in systems with varying memory and processing capabilities. / AFRIKAANSE OPSOMMING: Kommunikasiekanale van satelliete met lae wentelbane, bied 'n unieke omgewing wat inherent verskil van meeste ander kommunikasiekanale. As gevolg van veranderende wentelbaanpatrone, vertoon die kanaal 'n wisselende foutgedrag. Kommunikasievensters is beperk en moet geoptimeer word om die totale deurset van die stelsel te maksimeer. Groot koderingswinste kan verkry word deur die implementering van foutkorreksie kodes. Hierdie tesis voorsien 'n metode om die datadeurset van satelliete met lae wentelbaan te optimeer, deur middel van implementering van 'n missie-spesi eke foutbeheer strategie. Lae digtheid pariteit toetskodes (LDPC) is veelsydige kodes, bied goeie foutbeheer en is doeltre end vir verskillende kodekoerse en bloklengtes. Met drywingsbeperkinge op die ruimtesegment en afgesonderde grondstasies, moet hardeware komponente doeltreffend gebruik word om drywingsverbruik te verminder. Ten einde aan hierdie ontwerpsvereiste te voldoen, evalueer hierdie tesis verskeie LDPC dekodeerderalgoritmes. Deur 'n iteratiewe LDPC dekodeerder met 'n benaderingsalgoritme te implementeer, word 'n oplossing van lae kompleksiteit aangebied, maar wat steeds goeie foutkorreksie eienskappe toon. Die voorgestelde oplossing bied 'n baie goeie balans tussen benodigde hardeware kompleksiteit en koderingsprestasie. Daar is gevind dat heelwat parameters van die dekodeerders en kodes aangepas kan word, ten einde implementering in stelsels met 'n wye verskeidenheid van geheuespasie en verwerkingsvermoëns moontlik te maak.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In recent years Autonomous Underwater Vehicles (AUVs) have become interesting for harbor mapping and protection. AUVs require a SONAR sensor for observing their surroundings, thus enabling them to perform collision avoidance manoeuvres and scanning their operating environment for intruders or foreign objects, e.g. mines. To perform such actions the SONAR sensor is required to supply very fine range resolution for target imaging, as well as providing information about possible target velocity. Basic SONAR theory is discussed, as well as different approaches to signal design and processing techniques, for achieving the required resolution in range and target velocity. Two of the discussed approaches are selected for processing range and target velocity, respectively. Both approaches are simulated for their validity before being tested by using a custom-built platform. The platform is highly configurable and designed for capacity of testing a variety of SONAR signals and set ups. Furthermore, the platform is built by using off-the-shelf components to minimize development costs. The results of simulations and practical tests are presented. A high correlation between theory and practice is achieved. The knowledge and the platform presented form the stepping stone for further SONAR sensor developments. / AFRIKAANSE OPSOMMING: In die laaste jare het outonome onderwater voertuie (OOV) toenemend belangrik geword vir die kartografie en beskerming van hawens. OOV’s vereis SONAR sensore wat hulle in staat stel, om hulle omgewing waar te neem en sodoende botsing vermydings take te verrig en ook om hul werksomgewing noukeurig te skandeer om indringers of vreemde voorwerpe, bv. myne, op te spoor. Om sulke werk te verrig, word van die SONAR sensor vereis, om baie fyn afstand oplossings vir teiken te verskaf, insluitend die moontlike snelheid van die teiken. Basiese SONAR teorie word bespreek, en dan verskeie benaderings van sein ontwerp en verwerkings tegnieke. Twee van die bespreekte benaderings word gekies om afstand en teiken snelheid onderskeidelik te verwerk. Altwee benaderings word gesimuleer om hul geldigheid vas te stel, voor dat hulle getoets word op ’n pasmaat vervaardigde platform. Die platform is hoogs aanpasbaar en is ontwerp vir sy vermoë om ’n verskeidenheid SONAR seine en verwerkings te hanteer. Verder is die platform vervaardig met standard rakonderdele om ontwikkelingskoste so laag as moontlik te hou. Die uitslae van die simulerings en praktiese toetse word voorgestel. ’n Hoë mate aan korrelasie is bereik tussen teorie en praktyk. Die kennis en die platvorm, wat hier voorgestel word, vorm die eerste trappie vir toekomstige SONAR sensor ontwikkeling.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A collaboration between the Katholieke Universiteit van Leuven (KUL) and Stellenbosch University (SU), resulted in the development of a satellite based platform for use in agricultural sensing applications. This will primarily serve as a test platform for a digitally beam-steerable antenna array (SAA) that was developed by KUL. SU developed all flight - and ground station based hardware and software, enabling ground to flight communications and interfacing with the KUL SAA. Although most components had already been completed at the start of this M:Sc:Eng: project, final systems integration was still unfinished. Modules necessary for communication were also outstanding. This project implemented an automatic repeat and request (ARQ) strategy for reliable file transfer across the wireless link. Channel coding has also been implemented on a field programmable gate array (FPGA). This layer includes an advanced forward error correction (FEC) scheme i.e. a low-density parity-check (LDPC), which outperforms traditional FEC techniques. A flexible architecture for channel coding has been designed that allows speed and complexity trade-offs on the FPGA. All components have successfully been implemented, tested and integrated. Simulations of LDPC on the FPGA have been shown to provide excellent error correcting performance. The prototype has been completed and recently successfully demonstrated at KUL. Data has been reliably transferred between the satellite platform and a ground station, during this event. / AFRIKAANSE OPSOMMING: Tydens ’n samewerkingsooreenkoms tussen die Katholieke Universiteit van Leuven (KUL) en die Universiteit van Stellenbosch (US) is ’n satelliet stelsel ontwikkel vir sensor-netwerk toepassings in die landbou bedryf. Hierdie stelsel sal hoofsaaklik dien as ’n toetsmedium vir ’n digitaal stuurbare antenna (SAA) wat deur KUL ontwikkel is. Die US het alle hardeware en sagteware komponente ontwikkel om kommunikasie d.m.v die SAA tussen die satelliet en ’n grondstasie te bewerkstellig. Sedert die begin van hierdie M:Sc:Ing: projek was die meeste komponente alreeds ontwikkel en geïmplementeer, maar finale stelselsintegrasie moes nog voltooi word. Modules wat kommunikasie sou bewerkstellig was ook nog uistaande. Hierdie projek het ’n ARQ protokol geïmplementeer wat data betroubaar tussen die satelliet en ’n grondstasie kon oordra. Kanaalkodering is ook op ’n veld programmeerbare hekskikking (FPGA) geïmplementeer. ’n Gevorderde foutkorrigeringstelsel, naamlik ’n lae digtheids pariteit toetskode (LDPC), wat tradisionele foutkorrigeringstelsels se doeltreffendheid oortref, word op hierdie FPGA geïmplementeer. ’n Kanaalkoderingsargitektuur is ook ontwikkel om die verwerkingspoed van data en die hoeveelheid FPGA logika wat gebruik word, teenoor mekaar op te weeg. Alle komponente is suksesvol geïmplementeer, getoets en geïntegreer met die hele stelsel. Simulasies van LDPC op die FPGA het uistekende foutkorrigeringsresultate gelewer. ’n Werkende prototipe is onlangs voltooi en suksesvol gedemonstreer by KUL. Betroubare data oordrag tussen die satelliet en die grondstasie is tydens hierdie demonstrasie bevestig.