Thesis (MScIng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Both coaxial probe and waveguide (WG) measurement systems for electric and magnetic material property extraction were investigated. These measurement techniques were used to determine electrical properties of an inhomogeneous rock sample in its solid and crushed states. A lumped element model of the probe was used and permittivity was determined by the inversion algorithm developed by Stuchly and Stuchly. To support this technique it was compared to a full wave inversion algorithm and referenced to properties of the same samples but determined by a resonant cavity technique. The Nicholson, Ross and Weir inversion algorithm was used to determine material properties from WG measurements. As a reference, the same techniques were applied to a well defined material. It was found that neither of the measurement techniques could measure low loss factors or conductive materials and literature values were used in these cases. Various simulation models of the multiphase ore in both its solid and crushed states are presented. These models were utilised in finite-difference time-domain (FDTD) simulations of different microwave (MW) cavities. Simulation and experimental S-parameter comparisons are presented. The level of accuracy achieved varies as a function of the geometrical representation and material properties. After an S-parameter comparison with simulation results it was concluded that the electrical properties of both the solid and crushed rocks have been well determined for MW cavity design. Predicted and measured field distributions in cavities were also compared and it is shown that accurate models of multiphase materials become especially important in the determination of field distributions in and around different rock phases. Recommendations for the suggested material property determination and verification processes are presented. A specific application of this work is in the field of microwave assisted comminution. / AFRIKAANSE OPSOMMING: ’n Koaksiale probe en golfgeleier (WG) stelsels vir die bepaling van materiaal eienskappe (elektries en magneties) word gebruik met die doel om ’n nie-homogene rotsmonster te karakteriseer. Die ekstraksie algoritme van Stuchly en Stuchly word gebruik om die materiaal eienskappe te bepaal vanaf die gemete S11-parameter. Hierdie ekstraksie metode word vergelyk met ’n vol golf ekstraksie van permitiwiteit vanaf dieselfde gemete data. Beide die ekstraksie metodes word dan vergelyk met resonante holte meetings van dieselfde materiale. Die Nicholson, Ross en Weir ekstraksie algoritme word toegepas op meetings wat gedoen is deur die golfgeleier stelsel. As ’n verwysing word dieselfde tegnieke toegepas op ’n bekende materiaal en daar is gevind dit stem goed ooreen behalwe dat nie een van die twee meet tegnieke lae verlies faktore kan meet nie. Verder kan nie een van die twee sisteme geleidende materiale meet nie. Vir sulke gevalle is waardes nageslaan. Verskeie simulasiemodelle van die rots word voorgestel vir beide soliede en vergruisde monsters. Hierdie modelle word gebruik in FDTD simulasies van verskeie mikrogolftoevoegers met die oog om ’n vergelyking te tref tussen gesimuleerde en gemete S-parameters. Verskillende vlakke van akkuraatheid is bereik en is ’n funksie van die geometrie en die materiaaleienskappe van die model. Nadat gemete en gesimuleerde S-parameters vergelyk is, is gevind dat die materiaal eienskappe van beide die soliede en vergruisde rots monsters goed bepaal is vir mikrogo lf toevoeger ontwerp. Voorspelde en gemete veldverspreidings word ook vergelyk en dit is veral hierso van belang om ’n realistiese model van die nie-homogene monster te gebruik. Sekere voorstelle word gemaak om die verskillende aspekte van die meet van ma teriaaleienskappe en simulasiemodelle te kan verfyn. ’n Spesifieke toepassing van hierdie werk is in mikrogolf ondersteunde skeiding van minerale en erts.

Thesis (MScIng)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: This project investigates the improvement of an existing radar system by means of currently available technologies and signal processing techniques. Upgrades are aimed to improve the system's speci cations with focus on range resolution. Pulse compression and Doppler processing techniques are used to accomplish the improvement in range resolution. The use of pulse compression however resulted in numerous modi cations to the RF sub-system required by the introduction of Direct Digital Synthesizer modules. A full replacement of the existing signal processor with a Doppler processing based signal processor implemented on a single programmable rmware device was designed. Certain sections of this signal processor were implemented and tested. Pulse compression was successfully implemented and tested in both the transceiver and signals processor sections. / AFRIKAANSE OPSOMMING: Hierdie projek ondersoek die verbetering van 'n bestaande radar stelsel deur gebruik te maak van huidige tegnologie en seinverwerking tegnieke. Aanpasings is gemik om die radarstelselspesi kasies te verbeter met die fokus op afstandsresolusie. Pulskompressie en Doppler- lter tegnieke is gebruik om 'n verbetering te maak aan die afstandsresolusie van die stelsel. Die gebruik van pulskompressie het 'n groot aantal veranderings aan die RF-stelsel genoodsaak a.g.v. die gebruik van Direkte Digitale Sintetiseerder modules. Die huidige radarseinverwerker is volledig vervang met 'n Doppler gebaseerde verwerker. Hierdie verwerker is volledig ontwerp op 'n enkele programmeerbare fermatuureenheid maar slegs sekere gedeeltes is getoets. Pulskompressie is suksesvol toegepas en getoets in beide die RF-stelsel en in die gedeeltes van die radarseinverwerker wat getoets is.

Thesis (MScEng)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Very Large Scale Integration (VLSI) of the Rapid Single Flux Quantum (RSFQ) superconducting logic family is researched. Insight into the design methodologies used for large-scale digital systems and related logistics are reviewed. A brief overview of basic RSFQ logic gates with in mind their application in a cell based layout scheme suited for RSFQ is given. A standard cell model is then proposed, incorporating these cells, on which, a library of low temperature superconducting (L TS) cells are laid out. Research is made into computer techniques for storing and manipulating large-scale circuit netlists. On this base, a method of technology mapping Boolean circuits to an RSFQ equivalent is achieved. Placements on-chip are made, optimized for minimum net length, routed and exported to a popular electronic mask format. Finally, the convergent technology fields of solid state cooling and high-temperature superconducting electronics (HTS) are investigated. This leads to a proposal for a low profile, low cost, HTS cryopackaging concept. / AFRIKAANSE OPSOMMING: Grootskaalse integrasie (VLSI) van die "Rapid Single Flux Quantum" (RSFQ) supergeleidende familie van logiese hekke word uiteengesit. Insig in die ontwerpmetodes vir grootskaaIse digitale stelsels en verwante aspekte word ondersoek. 'n Kort oorsig van basiese RSFQ logiese hekke word gegee, met hulle toepassing in 'n uitlegskema wat geskik is vir RSFQ. 'n Standaard sel model, wat bogenoemde selle insluit, word voorgestel en 'n selbiblioteek word uitgele vir lae temperatuur supergeleidende bane. Ondersoek word ingestel na die manipulasie van die beskrywing van elektroniese bane en 'n manier om logiese Boolese baanbeskrywings om te skakel na fisiese RSFQ bane. Die fisiese plasing van selle word bespreek ten einde die verbindingslengte tussen selle te minimeer. Die finale uitleg word omgeskakel na 'n staandaard elektroniese formaat vir baanuitlegte. Die konvergerende tegnologievelde van "soliede toestand" verkoeling en hoe-temperatuur supergeleidende elektroniese bane word bespreek. Ten slotte word 'n nuwe tipe, lae profiel en lae koste kriogeniese verpakking voorgestel.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis discusses the design of a dual circularly polarized single element antenna with special emphasis on achieving a wide bandwidth and high polarization isolation. The aim of the study is to produce an antenna for transmission of colour video signals between a ground station and a low earth orbit satellite. Microstrip patch antennas are suitable for satellite applications because they are light weight, conformal and have a thin profile. However, the antennas' inherent naITOW bandwidth is one of their major drawbacks. The aperture coupled microstrip patch antenna boasts of a much-improved bandwidth over the traditional single layer microstrip antenna and the freedom of using separate substrates for the patch and the feeding network. Hence the designed single element antenna is aperture coupled. To achieve dual circular polarization with good polarization purity, the antenna had a crossed slot aperture with a balanced feed. The feed network was designed on a single layer. The design was executed in two steps using IE3D moment of methods simulation software: design of the radiating part, and design of the feed part. Each part was simulated and optimized on its own before the two were combined, simulated and optimized again. Parameters used in the antenna optimization were: the substrates' thicknesses and dielectric constants, patch and aperture dimensions, and the feed line width and offset. The designed antenna was built and measured. Initial measurements of S-parameters yielded unacceptable results, especially for S22 and S21, and so an investigation into the matter was conducted. That led to the sizes of the feed and reflector planes being extended. Absorbing material was used between the parallel feed and reflector planes because some power was, to a lesser extent, still escaping, due to the fact that the planes were fmite. Measurement results demonstrated reasonable agreement with the simulation. The final antenna had a reflection coefficient of less than -10 dB for the entire operating band of 400 MHz centred on 3 GHz, an isolation of approximately -15 dB in the operating band and a gain of 2 dBi and I dBi for Ports 1 and 2, respectively, at 3 GHz. These results, especially the gain, are influenced by the back radiation and the finite sizes of the feed and reflector planes. It is therefore recommended that an enclosed cavity be used at the back of the antenna and a 'dogbone' aperture be used to minimize back radiation. / AFRIKAANSE OPSOMMING: Die tesis omskryf die ontwerp van 'n tweevoudige sikuler gepolariseerde enkel-element antenne met spesiale klem op wye bandwydte en hoe polariserings isolasie. Die doel van hierdie studie is om 'n antenne vir uitsending van kleur video seine tussen 'n grond stasie en 'n omnentelingsatelliet daar te stel. Mikrostrook plakantennes is gepas vir satelliet toepassings weens hulle ligte gewig en dun profiel. Die antenne se gepaardgaande nou bandwydte is egter een van hulle grootste nadele. Die gleufgekoppelde mikrostrook plakantenne gee egter 'n baie beter bandwydte as die tradisionele enkellaag mikrostrook plakantenne asook die vryheid om verskillende substrate vir die plak en die voernetwerkte gebruik. Vir hierdie redes daar besluit om die enkel-element antenne sleufgekoppeld te maak. Om tweevoudige sikuler gepolariseerde met goeie polarisasie suiwerheid te kry, moes 'n kruisvonnige gleuf met 'n gebalanseerde voer ontwerp word. Die voernetwerk was op 'n enkellaag ontwerp. Die ontwerp was in twee fases in IE3D momentmetode simulasie sagteware gedoen: ontwerp van die stralings gedeelte, en ontwerp van die voer gedeelte. Elke gedeelte word afsonderlik gesimuleer en geoptimiseer voordat die twee saam gesimuleer en geoptimiseer word. Parameters wat gebruik word in die antenne optimiseering is: dikte van substraat en dielektriese konstante, plak en gleuf grootes, en voer lynwydte en afwyking. Die ontwerpde antenne is gebou en gemeet. Aanvanklike metings van S-parameters het onaanvaarbare resultate gel ewer, vera I vir S22 en S21,dus is daar besluit om die redes daarvoor te ondersoek. Dit het daartoe gelei dat die voer- en reflector vlakte groter gemmak is. Absorbeer material is tussen die parallel voer- en reflector vlakke gebruik aangesien steeds drywing verloor is weens die eindige vlakke. Meting resultate het taarnlike goed met die simulasies vertoon. Die finale antenne het 'n weerkaatskoeffisient laer as -10 dB getoon vir die volle bandwydte van 400 MHz gesentreerd rondom 3 GHz, 'n isolasie van ongeveer -15 dB in die bandwydte en 'n aanwins van 2 dBi en I dBi vir onderskeidelik Poorte I en 2 by 3 GHz. Hierdie resultate veral die aanwins is deur die straling na agter beinvloed en die eindige grootes van die voer- en reflector vlakke. Dit word om hierdie rede dus voorgestel dat 'n geslote holte aan die rugkant van die antenne gebruik word en dat 'n "dogbone" gleuf gebruik word om straling na agter te minimeer.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The aim of this thesis is the analysis and design of a broadband PIN diode switch. Pin diode switches are gaining popularity in RF and microwave applications today. This is due to their excellent switching and power handling capabilities, reliability, low cost and small size. An analysis and design procedure for broadband PIN diode switch design, using the series, shunt and compound topologies respectively, is presented. In order to do a proper switch design, accurate practical models for the components are required. Parameter extraction therefore formed an important consideration for this study. A parameter extraction procedure is presented, which enables the designer to very accurately extract the required models for the components in the environment they operate in. The designer can then do a proper design to ensure that the switch response when measured, closely corresponds to that simulated. A compound configuration switch was designed, built and measured to confirm the validity of the design procedure. The results illustrate that if the extracted models of the components are integrated into the design, the measured and simulated response compare remarkably well. / AFRIKAANSE OPSOMMING: Die doel van die tesis is die analise en ontwerp van 'n wyeband PIN diode skakelaar. PIN diode skakelaars is besig om meer populariteit te verwerf in hedendaagse RF en mikrogolf toepassings. Dit is as gevolg van die diode se goeie skakel- en drywing hantering vermoëns, betroubaarheid, lae koste en klein fisiese dimensies. 'n Analise en ontwerpsprosedure vir wye band PIN diode skakelaars in die serie, parallel en saamgestelde topologieë word getoon. Om 'n deeglike skakelaar ontwerp te doen, word akkurate en praktiese modele van die komponente benodig. Parameter ekstraksie was daarom 'n groot oorweging vir hierdie studie. 'n Metode om parameters te onttrek word getoon wat die ontwerper in staat stelom akkurate modelle van komponente te onttrek, in die omgewing waarin hulle gebruik word. Die ontwerper kan dan 'n deeglike ontwerp doen wat as dit gemeet word.. die gemete en gesimuleerde resultate goed salooreenstem. 'n Saamgestelde topologie skakelaar is ontwerp, gebou en gemeet om die ontwerpsprosedure te verifieer. Die resultate toon dat as die modelle wat onttrek is, gebruik word in die ontwerp, dan stem die gemete en gesimuleerde resultate baie goed ooreen.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The recent performance improvements of wireless communication systems are presenting possibilites for the use of wireless networks for industrial applications, which typically impose severe restrictions in terms of response time and flexibility. Traditionally most of the industrial protocols employ cable connections, which have limitations in terms of flexibility and development oportunities. The industrial protocol used for this project, is the Modbus protocol. This protocol is developed and implemented on a wireless environment by using data radio modems. The Modbus protocol is a master/slave protocol which provides an industry standard for industrial data transfer. A Modbus driver is designed for radio networks, so that it can function with different PLCs and SCADA packages, supporting Modbus protocol. This enables control and monitoring to be excercised over a long distance, and enables control equipment to be placed as required and not with particular wiring restrictions. / AFRIKAANSE OPSOMMING: Die onlangse verbetering in radiokommunikasiestelsels bied moontlikhede vir die gebruik van radionetwerke vir industriële toepassings, wat gewoonlik streng beperkings plaas in terme van responstyd en buigbaarheid. Tradisioneel is meeste van die industriële protokolle kabelgebaseer, wat redelik onaanpasbaar is. Die Modbus protokol is as basis in hierdie projek gebruik. Dit is 'n meester/slaaf industriestandaard, wat hier aangepas is vir toepassings met radiomodems. Die Modbus drywer is ontwerp om funksioneel te wees met 'n verskeidenheid van PLC's en SCADA pakette, wat die Modbus protokolondersteun. Dit stel beheer- en meetaksies in staat oor lang afstande en laat relatief vrye plasing toe van toerusting sonder bedradingsbeperkings.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Improvements in the area of satellite orientation control in the presence of large actuator gain changes are investigated. Gain changes primarily originate from actuator failures, but may also result from intermittent sensor availability and geomagnetic field effects. The stability and performance of a classic LQR control solution under these conditions is analyzed through simulation, and two adaptive schemes are developed to improve the response. The adaptive schemes mix elements from bang-bang control to increase performance, and banded control to increase robustness. These control schemes are thoroughly tested through simulation and the results are compared with those obtained for the classic solution. Extensive modelling of the system in the MATLAB™ environment is done to support the analysis of the controllers, and hardware sensors are built to provide realistic orientation measurements to the controllers. / AFRIKAANSE OPSOMMING: Verbeterings in die veld van satelliet oriëntasie beheer in die gevalle waar die aktueerders groot veranderinge in aanwins toon, word ondersoek. Aanwins veranderinge word primêr veroorsaak deur aktueerder falings, maar kan ook deur diskontinue sensor metings en magneetveld effekte van die aarde veroorsaak word. Die stabiliteit en gehalte van 'n klassieke LQR beheer strategie onder hierdie omstandighede word ondersoek deur simulasie, en twee aanpasbare beheer strategieë word ontwikkelom die oordrag te verbeter. Die aanpasbare beheer strategieë meng elemente van "bang-bang" beheer om die gehalte te verbeter, en gebande beheer tegnieke om die robuustheid van die stelsel te verbeter. Hierdie beheer strategieë is deeglik in simulasies getoets en die resultate is vergelyk met dié van die klassieke beheerder. Ekstensiewe modelleering van die stelsel is in die MATLAB™ omgewing gedoen om die beheerders te analiseer, en hardeware sensore is gebou om realistiese orientasie metings aan die beheerders te verskaf.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: The high pace of technological advancement enables the realisation of ever more advanced mobile communications standards with more functionality than simple voice communications. The hardware that is used to implement the radio sections of these systems generally require long design cycles, much longer than the design cycles of the other components of a communications system. Another problem is that, once new communications standards are introduced, the current hardware platforms used in the terminal equipment becomes obsolete because they can generally not be used with the new standards. This has serious cost implications for both the service provider and the consumer, because both parties have to acquire new equipment to be able to use the new standards. An elegant solution to the above issues is to use software-defined radio sections to replace the hardware radio components. New communications standards can then be supported by simply loading new software onto the equipment, provided the maximum processing capacity of the processor(s) that the software runs on can accommodate the bandwidth requirements of that specific standard. This thesis investigates the ideas behind software defined radio and also describes the design and implementation of a software architecture that can be used to implement software defined radios on general-purpose platforms such as personal computers. / AFRIKAANSE OPSOMMING: Die hoë tempo van tegnologiese vordering maak dit moontlik om baie gevorderde mobiele kommunikasie standaarde te implementeer wat meer funksionaliteit bied as blote spraakkommunikasie. Die hardeware wat gebruik word om die radios van sulke stelsels te implementeer neem gewoonlik langer om te ontwikkel as die ander komponente van die stelsels. Die ander probleem is dat hierdie hardeware gewoonlik nie hergebruik kan word wanneer nuwe kommunikasie standaarde in gebruik geneem word nie omdat die standaarde nie versoenbaar is nie. Dit het tot gevolg dat beide die verbruiker en die diensverskaffer groot bedrae geld moet spandeer om die nuwe tegnologie te kan gebruik. 'n Elegante oplossing vir hierdie probleme is om gebruik te maak van radios waarvan die funksionaliteit in sagteware gedefiniëer word. Nuwe kommunikasie standaarde kan dan gebruik word deur slegs die nodige sagteware op die toerusting te laai, solank die verwerkingskapasiteit van die mikroverwerkers in die stelsel die benodigde bandwydte kan akkommodeer. Hierdie tesis ondersoek die konsepte van sagteware-gedefiniëerde radio en beskryf die ontwerp en implementering van 'n sagteware argitektuur vir die implementering van sagteware-gedefiniëerde radios op veeldoelige platforms soos persoonlike rekenaars.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Common mode currents are a major source of interference in electrical and electronic systems. A universal solution to counteract common mode interference is to introduce an electromagnetic shield with known characteristics. Cable trays are often used to shield cables from unwanted electromagnetic interference (EM!) and its shielding characteristics are defined in terms of its transfer impedance. This thesis pursues the modelling and measurement of the transfer impedance and mutual inductance of non-magnetic cable trays. Theoretical analysis is firstly employed by means of Maxwell's equations after which method of moments (MoM) simulations are performed in order to determine the transfer impedance and mutual inductance within the interior region of a cable tray. The results obtained through simulation are then validated with measurements conducted with an automatic network analyser (ANA). The computational and measured data are in good agreement and the developed model can be used to predict the transfer impedance in the cross-section of non-magnetic cable trays. / AFRIKAANSE OPSOMMING: Gemenernodus strome is 'n bron van interferensie in elektriese en elektroniese stelsels. 'n Universele oplossing om hierdie gemenernodus interferensie teen werk is om 'n elektromagnetiese skerm met bekende eienskappe te implementeer. Geleier leikanale word dikwels gebruik om kabels teen elektromagnetiese interferensie te beskerm en die afskermings eienskappe word in terme van die kanaal se oordragsimpedansie gedefinieer. Hierdie tesis ondersoek die modelering en meting van die wedersydse induktansie en oordragsimpedansie van nie-magnetiese geleier leikanale. 'n Teoretiese analise word eers uitgevoer deur middel van Maxwell se vergelykings waarna metode van momente (MvM) simulasies uitgevoer word om die oordragsimpedansie en wedersydse induktansie in die interne gebied van 'n leikanaal te bepaal. Die resultate verkry deur simulasie word dan bevestig deur meting wat uitgevoer word met behulp van 'n automatiese netwerk analiseerder (ANA). Die numeriese en gemete data stem goed ooreen en die ontwikkelde model kan deurgaans gebruik word om die oordragsimpedansie in die deursnit area van nie-magnetiese geleier leikanale te voorspel.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The development of a radar system is a complex process, requiring a substantial amount of testing. In general, these tests are performed using field trials. Such trials are expensive, and their exact conditions can never be repeated. A radar environment simulator allows for repeatable testing of the majority of a radar's functionality; however, most commercial products are not cost effective. In this thesis we investigate the various approaches to modelling targets and the littoral environment, and then develop a low-cost, largely software defined simulator. This simulator is capable of generating real-time video signals for a monopulse doppler tracking radar. The core simulation routines reside in an extensible software framework which is populated with simple target and clutter models for a prototype simulator. Closed loop tracking tests verify the operation of the prototype simulator. / AFRIKAANSE OPSOMMING: Die ontwikkeling van 'n radarstelsel is a ingewikkelde proses wat verskeie stelseltoetse benodig. Veldtoetse, wat gewoonlik gebruik word, is 'n duur proses, en die toestande is nooit presies dieselfde nie. 'n Radar-omgewingsimulator kan 'n groot deel van 'n radar se funksionaliteit herhaaldelik toets. Daar is egter weinig koste-effektiewe kommersile produkte vir hierdie doel beskikbaar. Hierdie tesis ondersoek verskeie teiken- en omgewingsmodelle, waarna 'n lae-koste, meestal sagteware-gedefinieerde simulator ontwikkel word. Hierdie simulator genereer intydse videoseine vir 'n enkelpuls-dopplervolgingsradar. Die kernfunksionaliteit van die simulator is in sagteware gesetel, en basiese teiken- en omgewingsmodelle is geïmplementeer. Die prototipe-simulator word getoets deur dit aan die radar self te koppel, en dan die teiken-opsporing en -volging te verifieer.