Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / Nonlinear transistor modeling is becoming increasingly popular due to the demand for high linearity and high efficiency microwave amplifiers. The available models often fail to accurately predict the higher order harmonics and intermodulation distortion, which are essential when designing high-linearity amplifier circuits. This thesis describes the design of hardware and software used for the development of nonlinear CAD models. A multiline TRL calibration kit is designed and manufactured so that the characterisation of a LDMOSFET, with a RF output power capability of 10W, can be performed using an adaptive-bias S-parameter measurement algorithm. Verification standards are also manufactured and used to determine the measurement accuracy after calibration. A series of GUIs are developed to ease the model extraction process. The extraction of the small-signal model parameters is performed between 0.4 and 3 GHz, and the extraction of the parameter values for the Fager large-signal model is then performed. An improved model is defined that implements two nonlinear charge sources in stead of the three nonlinear capacitors used in the Fager model. The nonlinear charge equations are formulated using the voltage-derivatives of the calculated nonlinear charge at each port of the device. By accurately modeling the voltagederivatives of the charge, where the voltages are functions of time, the prediction of the current produced by each of the charge sources is improved. The nonlinear models are verified against the MET model, and all three models are compared to measured data. It is shown that the models are able to accurately predict the single-tone and two-tone output harmonics for class-AB operation, and in many cases the predictions outperform that of the MET model. The single-tone output power is also verified for class-C operation. Although this prediction is not extremely accurate, it is found that the correct trend for the output harmonic power can be predicted.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / Outside the confines of cities and metropolitan areas, telecommunications may still be required. Farmers may, for example, want to communicate with each other or with local municipality or law enforcement. Various factors may make the application of fixed infrastructure telecommunications networks to rural situations like these unfeasible. Fixed infrastructure may prove to be ineffective due to geographic, social or monetary reasons. Ad hoc networking seems like an intriguing solution to these elements of the rural telecommunications problem. Instead of using the client-server architecture approach, ad hoc networks use a peer-to-peer network architecture that allows the network to change in a more dynamic fashion. Hosts of such a network can join or leave the network dynamically and will share in the forwarding responsibility. Routing is done dynamically. Transceiver range is still an issue. To counteract this problem satellites can be used to extend the communications range of a network. Communication with a satellite can be added by using gateway hosts that are equipped to establish satellite up- or downlinks. Even if one such gateway host is deactivated, ad hoc network hosts should be able to find alternative gateways (if such alternative gateways exist). For this thesis, various MAC and Network protocols will be evaluated. One protocol set will be selected and adapted to a low-bandwidth situation. Cross layer design will be used in an attempt to decrease overhead of this strategy. A simulation model was devised to predict system performance. These simulations was followed by interpretation of results which rendered a theoretical basis with which network behaviour can be explained and even predicted. A tool-like framework has, in effect, been developed for the simulation and development of ad hoc network protocols. Novel approaches to protocol behaviour analysis have also been devised.

Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2006. / This project was initiated by ARMSCOR to research the feasibility of an unmanned aerial vehicle launching from and landing on a South African Navy ship. The objective of this project was to develop a strong basis for other similar projects.

Thesis (MScIng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Primary health care telemedicine services require the acquisition and transmission of patient data including high quality still and video images via telecommunication networks. The objective of this thesis is to investigate the implementation of a generalpurpose medical camera as an alternative to the complex and costly CCD based cameras generally in use at present. The design is based on FillFactory’s SXGA (1280 ×1024) CMOS image sensor. A low-cost Altera Cyclone FPGA is used for signal interfacing, filtering and colour processing to enhance image quality. A Cypress USB 2.0 interface chip is employed to isochronously transfer video data up to a maximum rate of 23.04 MBytes per second to the PC. A detailed design and video image results are presented and discussed; however the camera will need repackaging and an approval for medical application by medical specialists and concerned bodies before releasing it as full-fledged product. / AFRIKAANSE OPSOMMING: Primêre gesondheidssorg telemedisyne dienste moet hoëkwaliteit televisiebeelde van hul pasiënte verkry deur van telekommunikasienetwerke gebruik te maak. Die doel van hierdie tesis is om die toepassing van n meerdoelige mediese kamera te ondersoek as n alternatief tot duur, komplekse CCD-gebaseerde kameras wat huidiglik gebruik word. Die ontwerp is gebaseer op n hoëkwaliteit CMOS beeldsensor. n Goedkoop Altera Cyclone FPGA word gebruik vir seinkoppelvlak, filtering en kleurprosessering om die kwaliteit van die beeld te verhoog. n Hoëspoed USB 2.0 poort word gebruik om die data teen die nodige spoed te versend. n Gedetailleerde ontwerp, en die beeldresultate word voorgelê en bespreek. Die kamera moet egter eers deur mediese spesialiste en relevante beheerliggame goedgekeur word voordat dit as n volledige produk vrygestel kan word.

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: 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) -- Stellenbosch University, 2004. / ENGLISH ABSTRACT: Wireless Area Network technology for industrial and factory applications is important for satisfying inflexible (safety-critical) real-time requirements in sometimes harsh environments. Many of these applications involve mobile subsystems and could benefit from recent Wireless LAN technologies replacing the current cable-based systems. An immediate question is how this technology can be used for wireless Area Network systems? An important aspect of this question is the development of time-variable wireless links with good real-time performance. This project will attempt to answer some aspects of this question. The main objective of this thesis is to create a wireless area network for instrumentation purposes, interconnecting various monitoring and control transducers to a central master station. This project focuses on three transmission technologies used for wireless LANs with low power consumption; capable of close range positioning, indoors as well as outdoors. These transmission technologies are Infrared LAN (IrDA), Spread Spectrum LAN and Narrowband Microwave LAN. As a result of the evaluation of the three technologies, an Infrared LAN (IrDA) system was implemented as an area network, utilising an IrLAP protocol (Master and Slave) as a communication protocol. The Master is enabled to monitor and control all slaves interfaced to it. / AFRIKAANSE OPSOMMING: Draadlose netwerktegnologie vir industrietoepassings, is nodig om aan te pas by spesifieke veiligheids- en omgewingstoestande. Baie van hierdie toepassings het betrekking op mobiele substelsels en kan baat by vervanging van bekabeling met onlangse draadlose netwerktegnologie. Die ontwikkeling van sulke netwerke met goeie tydreaksie, is hier belangrik. Die hoofdoel van hierdie tesis is om ’n draadlose areanetwerk te skep vir instrumentasiedoeleindes, wat verskeie monitor-en beheeromsetters aan ’n sentrale meesterstasie sal verbind. Hierdie projek fokus op 3 sulke benaderings, nl. Infrarooi AN (IrDA), Spreispektrum AN en Nouband Mikrogolf AN. Na ondersoek is ’n stelsel gebaseer op IrDA, geimplementeer as areanetwerk, met behulp van die IrLAP protokol. Die meester beheer alle kommunikasie met- en beheeraksies van die buitestasies.