Shannon showed that the codes with random-like codeword weight distribution are capable of approaching the channel capacity. However, the random-like property can be achieved only in codes with long-length codewords. On the other hand, the decoding complexity for a random-like codeword increases exponentially with its length. Therefore, code designers are combining shorter and simpler codes in a pseudorandom manner to form longer and more powerful codewords. In this research, a method for designing non-binary compound codes with moderate to high coding rate is proposed. Based on this method, non-binary single parity-check (SPC) codes are considered as component codes and different iterative decoding algorithms for decoding the constructed compound codes are proposed. The soft-input soft-output component decoders, which are employed for the iterative decoding algorithms, are constructed from optimal and sub-optimal a posteriori probability (APP) decoders. However, for non-binary codes, implementing an optimal APP decoder requires a large amount of memory. In order to reduce the memory requirement of the APP decoding algorithm, in the first part of this research, a modified form of the APP decoding algorithm is presented. The amount of memory requirement of this proposed algorithm is significantly less than that of the standard APP decoder. Therefore, the proposed algorithm becomes more practical for decoding non-binary block codes. The compound codes that are proposed in this research are constructed from combination of non-binary SPC codes. Therefore, as part of this research, the construction and decoding of the non-binary SPC codes, when SPC codes are defined over a finite ring of order q, are presented. The concept of finite rings is more general and it thus includes non-binary SPC codes defined over finite fields. Thereafter, based on production of non-binary SPC codes, a class of non-binary compound codes is proposed that is efficient for controlling both random-error and burst-error patterns and can be used for applications where high coding rate schemes are required. Simulation results show that the performance of the proposed codes is good. Furthermore, the performance of the compound code improves over larger rings. The analytical performance bounds and the minimum distance properties of these product codes are studied. / Thesis (Ph.D.)-University of KwaZulu-Natal, Durban, 2013.

Thesis (MScIng)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: The Applications of Superconductors in Cellular Network Base Stations R. Du Toit Department of Electronic Engineering University of Stellenbosch Private Bag X1, 7602 Matieland, South Africa Thesis: MScEng (E&E) March 2008 Wireless communications have increasingly become part of our world. The growth of radio frequency (RF) wireless communications has led to an increasing demand for frequency spectrum licenses, increased system capacity and larger user bandwidths. These demands lead to frequent improvements on the physical and higher layers of wireless communication protocols. Changes in the physical layer are frequently followed by the need for replacement of dedicated hardware components. The need therefore exists for a more general and programmable physical layer. A more general and programmable radio architecture implies increased radio front-end performance without losing programmability. The contribution of this thesis is the analysis of how superconductor electronics (SCE) using Rapid Single Flux Quantum (RSFQ) logic may advance wireless radio front-ends by providing a general-purpose programmable radio architecture. Superconductor analogue to digital converters (ADCs) are employed as high performance, programmable digitization structures. Once a received signal is digitized, SCE can be used to rapidly do recursive operations such as synchronization and multi-path delay estimation. These operations are based on correlation, and for evaluation of such operations with SCE the popular CDMA multiplexing method is studied along with the WCDMA protocol used in the 3G UMTS standard. Two delta-type oversampling superconductor ADC modulator designs are presented and evaluated along with a hybrid decimation filter design, using both the benefits of SCE and room temperature electronics. A fast RSFQ correlator design is also presented and evaluated for use in a multi-path estimation structure. A rapid multi-path delay estimation architecture based on fast RSFQ circular data buffers and correlators is presented. The architecture uses the fast speeds of RSFQ logic to obtain accurate path delay estimates in a rapidly changing wireless environment. It is concluded that RSFQ-based wireless receiver components offer promising new options for data conversion, correlation and multi-path delay estimation implementations. / AFRIKAANSE OPSOMMING: The Applications of Superconductors in Cellular Network Base Stations R. Du Toit Department of Electronic Engineering University of Stellenbosch Private Bag X1, 7602 Matieland, South Africa Thesis: MScEng (E&E) March 2008 Draadlose kommunikasie word al hoe meer deel van ons wêreld. Groei in radiofrekwensietipe kommunikasie het gelei tot ’n toenemende aanvraag na frekwensiespektrum lisensies, vergrote stelselkapasiteit en groter gebruikerbandwydtes. Hierdie aanvrae lei tot gereelde en spoedige verbeteringe op die fisiese en hoër lae van huidige draadlose kommunikasieprotokol. Veranderinge in die fisiese laag vereis gewoonlik dat toegewyde hardewarde komponente vervang word. Die behoefte bestaan dus vir ’n meer algemene, programmeerbare fisiese laag. Dit vereis dus ’n verbetering in die radio-ontvanger se komponente naaste aan die antenna sonder om programmeerbaarheid te verloor. Die bydrae van hierdie tesis is hoofsaaklik die analise van hoe supergeleierelektronika wat van Rapid Single Flux Quantum (RSFQ) logika gebruik maak, huidige draadlose sellulêre basisstasies se fisiese laag kan verbeter deur ’n meer algemene en programmeerbare radio-argitektuur op te lewer. Supergeleier analoog-na-syfer omsetters (ADCs) word bestudeer as moontlike programmeerbare versyferingstrukture wat steeds hoë werkverrigting lewer. Wanneer ’n ontvangde sein in digitale vorm omgesit is, kan supergeleierelektronika gebruik word om vinnig rekursiewe operasies uit te voer. Voorbeelde van sulke operasies is sinkronisasie en die waardebepaling van die vertraging van verskillende paaie wat ’n sein volg na die ontvanger. Hierdie spesifieke operasies se werking is gebaseer op korrelasie, en vir die evaluasie van sulke operasies met supergeleierelektronika is die gewilde wyeband-CDMA (WCDMA) protokol wat gebruik word in die 3G UMTS-standaard. Twee supergeleier-delta-tipe oorversyferings-ADC-moduleerderontwerpe word voorgelê en evaluasie word daarop gedoen saam met ’n hibriede desimasiefilterontwerp wat gebruik maak van beide die voordele van supergeleierelektronika en kamertemperatuurelektronika. ’n Vinnige RSFQ-korreleerder word ook voorgelê en evaluasie word daarop gedoen vir gebruik binne ’n multi-padvertraging-waardebepalerstruktuur. Hierdie struktuur wat gebaseer is op RSFQ sirkulêre buffers en korreleerders, word voorgelê. Die waardebepaler maak gebruik van die spoed van RSFQ-logika om akkurate multi-padvertragingswaardes te bepaal in ’n vinnig veranderende draadlose omgewing. Die gevolgtrekking word gemaak dat RSFQ-gebaseerde draadlose ontvangerkomponente groot voordele in versyfering-, korreleerder- en multi-padvertragingsbepaler-toepassings bied.

Thesis (MScIng)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Modern communication systems demand efficient, linear power amplifiers. The amplifiers are often operated in the backed-off power levels at which linear amplifiers such as class B amplifier are particularly inefficient. The Doherty amplifier provides an improvement as it increases efficiency at backed of power levels. Doherty amplifiers consists of two amplifiers, a carrier amplifier and a peaking amplifier, of which the output is combined in a novel way. Implementation of the Doherty amplifier with transistors is not ideal. One of the main problems is the insufficient current production of the peaking amplifier at peak envelope power (PEP) if it is implemented as a class C amplifier. A suggested solution to this problem is a bias adaption system that controls the peaking amplifier gate voltage dynamically depending on the input power levels. The design and evaluation of such a adaptive Doherty amplifier is the main goal of this thesis. A classical Doherty amplifier with and an uneven Doherty amplifier with unequal power division between the carrier and peaking amplifiers are also evaluated and compared with the adaptive Doherty amplifier. The amplifiers are designed using a 10 W LDMOS FET device, the MRF282. The adaptive Doherty amplifier and the uneven Doherty amplifier show significant improvements in efficiency and output power over the even Doherty amplifier. At PEP the adaptive Doherty delivers 42.4 dBm at 39.75 % power added efficiency (PAE), the uneven Doherty amplifier 41.9 dBm at 40.75 % PAE and the even Doherty amplifier 40.8 dBm at 38.6 % PAE. At 3dB backed-off input power the adaptive Doherty amplifier has an efficiency of 34.3%, compared to 34.9 5% for the uneven Doherty amplifier and 29.75 % for the even Doherty amplifier. / AFRIKAANSE OPSOMMING: Moderne kommunikasie stelsels vereis effektiewe, linieêre drywing versterkers. Die versterkers word dikwels in laer drywings vlakke bedryf waar linieêre versterkers soos ’n klas B versterker besondere lae effektiwiteit het. Die Doherty versterker bied ’n uitweg omdat dit verbeterde effektiwiteit by lae drywings vlakke bied. ’n Doherty versterker bestaan uit twee versterkers, die hoof versterker en die aanvullende versterker, waarvan die uittrees met ’n spesiale kombinasie netwerk bymekaar gevoeg word. Die implementasie van Doherty versterkers met transistors is nie ideaal nie. Een van die hoof probleme is die onvoldoende stroom wat deur die aanvullings versterker gebied word by piek omhulsel drywing (POD). ’n Oplossing vir die probleem is om ’n aanpassings sisteem te gebruik wat die aanvullende versterker se hekspanning dinamies beheer afhangende van die intree drywings vlakke. Die ontwerp en evaluasie van so ’n aanpassings Doherty versterker is die hoof doel van hierdie tesis. ’n Klassieke Doherty versterke met gelyke drywings verdeling en ’n ongelyke Doherty versterker wat gebruik maak van ongelyke drywings verdeling tussen die hoof-en aanvullende versterkers is ook gevalueer en vergelyk met die aanpassings Doherty versterker. Die versterkers was ontwerp met ’n 10 W LDMOS FET, die MRF282. Die aanpassings Doherty versterker en die ongelyke Doherty versterker het aanmerklike verbeteringe in effektiwiteit en uittree drywing gebring in vergelyking met die ewe Doherty versterker. By POD het die aanpassings versterker 42.4 dBm teen 39.75 % drywing toegevoegde effektiwiteit (DTE) gelewer, die ongelyke Doherty versterker 41.9 dBm teen 40.75 % DTE, en die ewe Doherty versterker 40.8 dBm teen 38.6 DTE. By ’n intree drywingsvlak 3 dB laer as POD het die aanpassings Doherty versterker ’n effektiwiteit van 34.3 % getoon, in vergelyking met die onewe Doherty versterker se 34.9 % en die ewe Doherty versterker se 29.75 % DTE.

Thesis (MScIng)--University of Stellenbosch, 2008. / ENGLISH ABSTRACT: This thesis describes the design, modelling and implementation of a prototype request- processing software system, which can be used as the basis for a request processing frame- work for systems with limited request processing resources. Due to design constraints, the request-processor system described here consists of multiple processes. It is problematic to prove that a multiple process design satis es the conditions of a set of prede ned requirements. One way to verify that such a multiple process design works as intended, is to use modelchecking tools. The system was veri ed for correctness and translated into a working prototype soft- ware system. / AFRIKAANSE OPSOMMING: Hierdie tesis beskryf die ontwerp, modellering en implementering van 'n prototipe versoek- verwerking-sagtewarestelsel. Die stelsel kan gebruik word om 'n versoekverwerkings- raamwerk te ontwerp vir stelsels met beperkte versoekverwerkingshulpbronne. Die ver- soekverwerkingsstelsel bestaan uit veelvoudige prosesse. Die veelvoudige proses-ontwerp was die direkte gevolg van stelselbeperkings. Dit is problematies om te bewys dat 'n multi-proses-ontwerp korrek funksioneer. Mod- elchecking-sagteware kan gebruik word om te veri eer of 'n stelsel korrek funksioneer. Die korrektheid van die stelsel is geveri eer voordat die nale prototipe ge¨implementeer is.

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Active noise reduction (ANR) is a method of cancelling acoustic noise in a defined enclosure. Two methods exist to implement ANR, they are the analog feedback method and the digital feedforward method. Commercial ANR systems employing feedback methods have been around since the 1980's. Feedforward methods have however only become practically implemental with the age of fast real time digital signal processing. In current systems, feedback ANR is used to attenuate broadband noise whilst feedforward methods are used to attenuate narrow band or tonal noise [2]. This thesis investigates feedforward ANR to cancel broadband acoustic noise in aircraft headsets. Different adaptive filters, optimal configuration of adaptive filters and practical limitations to broadband attenuation for headsets are addressed. Results from this thesis show that at least 10dS noise energy attenuation is attainable over a bandwidth of 2.5kHz. A number of areas for further research are also identified. / AFRIKAANSE OPSOMMING: Aktiewe geraas beheer (AGS) is 'n metode om akoestiese geraas te kanselleer in 'n gedefinieerde omgewing. Twee metodes bestaan om AGS te implementeer. Hulle is die analoog terugvoer en digitale vorentoevoer metode. Kommersiële AGS wat die terugvoer metode gebruik is al in gebruik van die 1980's. Vorentoevoer metodes is egter eers sedert vinnige intydse digitale sein prosessering moontlik. In huidige stelsels word terugvoer AGS gebruik vir die attenuasie van wyeband geraas terwyl vorentoevoer metodes gebruik word om nouband of enkel toon geraas te kanselleer [2]. Die tesis ondersoek vorentoevoer AGS om wyeband akoestiese geraas te kanselleer in vliegtuig kopstukke. Verskillende aanpasbare filters, optimale opstelling van aanpasbare filters en praktiese beperkings tot wyeband attenuasie vir kopstukke word ondersoek. Resultate van die tesis wys dat ten minste 10dS geraas energie attenuasie behaal kan word oor 'n bandwydte van 2.5kHz. 'n Aantal areas vir verder navorsing is ook geïdentifiseer.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Flash memory and the errors induced in it by radiation were studied. A test board was then designed and developed as well as a radiation test program. The system was irradiated. This gave successful results, which confirmed aspects of the study and gave valuable insight into flash memory behaviour. To date, the board is still being used to test various flash devices for radiation-harsh environments. A memory protection unit (MPU) was conceptually designed and developed to morntor flash devices, increasing their reliability in radiation-harsh environments. This unit was designed for intended use onboard a micro-satellite. The chosen flash device for this study was the K9F1208XOA model from SAMSUNG. The MPU was designed to detect, maintain, mitigate and report radiation induced errors in this flash device. Most of the design was implemented in field programmable gate arrays and was realised using VHDL. Simulations were performed to verify the functionality of the design subsystems. These simulations showed that the various emulated errors were handled successfully by the MPU. A modular design methodology was followed, therefore allowing the chosen flash device to be replaced with any flash device, following a small reconfiguration. This also allows parts of the system to be duplicated to protect more than one device. / AFRIKAANSE OPSOMMING: 'n Studie is gemaak van" Flash" geheue en die foute daarop wat deur radiasie veroorsaak word. 'n Toetsbord is ontwerp en ontwikkel asook 'n radiasie toetsprogram waarna die stelsel bestraal is. Die resultate was suksesvol en het aspekte van die studie bevestig en belangrike insig gegee ten opsigte van "flash" komponente in radiasie intensiewe omgewmgs. 'n Geheue Beskermings Eenheid (GBE) is konseptueel ontwerp en ontwikkelom die "flash" komponente te monitor. Dit verhoog die betroubaarheid in radiasie intensiewe omgewings. Die eenheid was ontwerp met die oog om dit aan boord 'n mikro-satelliet te gebruik. Die gekose "flash" komponent vir die studie was die K9F1208XOA model van SAMSUNG. Die GBE is ontwerp om foute wat deur radiasie geïnduseer word in die "flash" komponent te identifiseer, herstel en reg te maak. Die grootste deel van die implementasie is gedoen in "field programmable gate arrays" and is gerealiseer deur gebruik te maak van VHDL. Simulasies is gedoen om die funksionaliteit van die ontwikkelde substelsels te verifieer. Hierdie simulasies het getoon dat die verskeie geëmuleerde foute suksesvol deur die GBE hanteer is. 'n Modulre ontwerpsmetodologie is gevolg sodat die gekose "flash" komponent deur enige ander flash komponent vervang kan word na gelang van 'n eenvoudige herkonfigurasie. Dit stelook dele van die sisteem in staat om gedupliseer te word om sodoende meer as een komponent te beskerm.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This thesis investigates and develops some aspects of low speed wireless telemetry applications. The system configuration is one of a single master, controlling and communicating with multiple slave stations over a radio network. The aim of this thesis is to develop a narrow band wireless communications network based on a protocol with slotted time base, utilizing standard, off the shelf hardware. The idea is to investigate different strategies for improvement of data throughput performance under conditions of both low- and high loading, using this basic protocol. Such strategies may, amongst others include collision detection, flow control and pre-scheduling algorithms. This thesis will also show the how the non-adaptive system's data throughput performance can be improved using an adaptive system under low- and high loading. Half-duplex communication mode will be used for data communication. / AFRIKAANSE OPSOMMING: Hierdie tesis ondersoek en ontwikkel sommige aspekte van laespoed radiotelemetrie toepassings. Die stelselkonfigurasie is een van 'n enkel meesterstasie wat met 'Il aantal buitestasies kommunikeer oor 'n radionetwerk. Die doel van die tesis is om 'n tydgegleufde protokol te ontwikkel vir nouband radiotoepassings, deur gebruik te maak van standaard, maklik beskikbare hardeware. Die doel is om verskillende benaderings te ondersoek vir die verbetering van datadeurset onder toestande van beide hoë- en lae belading. Sulke strategieë mag botsingsdeteksie, vloeibeheer en voor-skedulering insluit. Die tesis salook aandui hoe die data deurset van die nie-aanpasbare metode verbeter kan word, deur gebruik te maak van 'n aanpasbare metode vir beide beladingstipes. Die kommunikasiestelsel is half-dupleks gebaseer.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: This thesis documents the research, design, implementation and successful testing of a prototype camera probe to survey the inside of hard rock boreholes. Rock core images are intended to aid mine geologists in recording the borehole rock layers. The system consists of a wide-angle fisheye lens mounted onto a CMOS digital image sensor. The image data is read in and processed by an FPGA, then stored on a removable sn flash memory card. All of the aforementioned components are mounted inside a watertight Perspex tube. Application specific PC software is used to process the data to form strip images of the borehole wall. Using mathematical correlation, these images are stitched together into a virtual core that is a flattened representation of the rock inside the borehole. The probe contains its own power and light source which enables it to be deployed easily with no external wires needed for operation. The storage capacity, image quality, and lighting design can be improved in future design revisions. / AFRIKAANSE OPSOMMING: Die inhoud van hierdie tesis behels die navorsmg, ontwerp, implementering, en suksesvolle toetsing van 'n prototipe kameraprobe wat dit moontlik maak om die binnewand van boorgate in harde rots te besigtig. Beelde van die rotskern vergemaklik die taak van myngeoloë wat die rotslae, waardeur die boorgat strek, moet opteken. Die stelsel behels 'n wyehoek bollens wat op 'n CMOS digitale sensor gemonteer is. Die data gewerf vir die vorming van die beeld word deur 'n FPGA ingelees en verwerk, waarna dit op 'n verwyderbare SD flits geheuekaart gestoor word. Die bogenoemde komponente word alles binne 'n waterdigte Perspexbuis monteer. Gebruikerspesifieke sagteware vir persoonlik rekenaars word gebruik om die data te verwerk en sodoende strookbeelde van die binnewand van die boorgat te vorm. Met gebruik van wiskundige korrelasie word hierdie beelde aan mekaar gelas om 'n virtuele kern te vorm, wat 'n voorstelling is van die rots binne die boorgat. Die probe bevat self krag en ligbronne, wat toelaat dat dit maklik bruikbaar is sonder enige eksterne bedrading. Toekomstige hersienings van die ontwerp sal verbeterde data geheue, beeldgehalte en beligting kan bewerkstellig.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The purpose of this study was to investigate the feasibility of a moon sensor as an alternative or supplemental sensor to supply attitude information to a satellite. The visibility of the moon was evaluated with regards to that of the sun from a satellite (i.e. the feasibility of the moon sensor is compared to that of a sun sensor). An algorithm was developed to calculate the center of the moon, regardless of phase or rotation, to offer increased accuracy of the center of the moon. The accuracy of this algorithm and the possible error margins were evaluated and discussed in both ideal and actual test cases. The sensor was implemented on embedded hardware. The conclusion of the feasibility analysis was that the sensor would function well as a supplemental sensor (e.g. in conjunction with a sun-sensor) rather than as an alternative sensor. The accuracy of the moon center algorithm was satisfactory for attitude deterrnina tion. This sensor could thus be seriously considered for use on a future satellite. / AFRIKAANSE OPSOMMING: Die doel van die studie is om die lewensvatbaarheid van 'n maan-sensor, as alternatiewe of aanvullende sensor, om oriëntasie data aan 'n sateliet te verskaf, te ondersoek. Die sigbaarheid van die maan en die sigbaarheid van die son is met mekaar vergelyk, vanaf 'n sateliet (m.a.w. die uitvoerbaarheid van 'n maan-sensor is vergelyk met dié van 'n son sensor). 'n Algorittne is ontwikkel om die middelpunt van die maan, ongeag van fase of rotasie, te bereken om verhoogde akuraatheid van die maan se middelpunt te bied. Die akuraatheid van die maan-middelpunt algoritme en moontlike foute is evalueer en bespreek in beide ideale sowel as werklike toets gevalle. Die sensor was op hardeware geimplenteer. Die gevolgtrekking van die lewensvatbaarheids analise is dat die sensor effektief sal funksioneer as 'n aanvullende sensor (d.w.s saam met 'n son sensor) eerder as 'n alternatiewe sensor. Die resultate verkry van die evaluasie van die maan-middelpunt algoritme is bevredegind en is voldoende vir oriëntasie bepaling. Die sensor kan dus ernstig oorweeg word vir gebruik op 'n sateliet in die toekoms.

Thesis (MScEng)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The use of commercial-off-the-shelf components in low earth orbit (LEO) satellite systems has become a very popular design trend. Not only are many of these components sufficiently radiation tolerant, but are also less expensive than their space qualified counterparts. Commercial processors are already used in the on-board computer (OBC) of satellites like SUNSAT 2004, CanX and SNAP-I. With the increasing demand for smaller, less expensive satellites and a shorter time-to-market window, the feasibility of implementing a satellite's OBC as a system-on-a-chip (SoC) is now considered. This thesis describes a single-chip implementation, excluding memory, of a LEO microsatellite's OBC on the commercial grade Altera Excalibur embedded processor. A typical satellite OBC system was developed on the Excalibur device to test the functionality and performance of the device as a single-chip OBC. / AFRIKAANSE OPSOMMING: Die gebruik van kommersiële komponente in lae aardwentelbaan satelliet stelsels het 'n baie gewilde ontwerps neiging geword. Meeste van hierdie komersiële komponente is nie net voldoende bestand teen die radiasie in die ruimte nie, maar boonop goedkoper as soortgelyke komponente wat spesifiek vir de ruimte vervaardig is. Kommersiële verwerkers word alreeds gebruik in die aanboord rekenaar (AR) van satelliete soos SUNSAT 2004, CanX and SNAP-I. Met die aahoudende aanvraag vir kleiner, goedkoper en 'n korter ontwikkelings tydperk, word die implementering van 'n satelliet se AR as 'n stelsel-op-'nskyfie nou oorweeg. Hierdie tesis beskryf 'n enkel-skyfie implementasie, geheue uitgesluit, van 'n lae aardwentelbaan mikrosatelliet se AR op die kommersiële Altera Excalibur geïntregreerde verwerker. 'n Tipiese AR stelsel was ontwikkelop die Excalibur verwerker om die funksionaliteit en werkverrigting van die toestel as 'n enkel-skyfie AR te toets.