Thesis (MscEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The aim of this thesis is to investigate the suitability of TEM (Transverse Electromagnetic) horn antennas for use as feed structures for the Square Kilometre Array (SKA) radio telescope, in particular with regard to the roundness of the radiation pattern. A literature study shows that existing TEM horn designs do not yield a round radiation pattern over a wide bandwidth and that an alternative is required. The Method of Moments (MoM) is a computational electromagnetic (CEM) technique typically used in the analysis of TEM horn antennas. An in-house MoM solver is successfully developed to analyse such antennas and is able to calculate the current density on the surface of a conductor, as well as the farfield patterns of an antenna. A modification to an exponential TEM horn antenna is proposed and simulations show the modification is successful in yielding a round radiation pattern over a wide bandwidth. The modified exponential TEM horn has a convex triangular arc at the end of each antenna plate and is constructed for measurement. Due to limited construction capabilities, the measurements deviate slightly from the simulated results but still indicate the potential of the structure to yield a round radiation pattern over a wide bandwidth. / AFRIKAANSE OPSOMMING: Die doel van hierdie tesis is om die geskiktheid van transverse elektromagnetiese (TEM) horing antennas te ondersoek vir die gebruik as voerstrukture vir die Square Kilometre Array (SKA)- radioteleskoop, veral met betrekking tot die rondheid van die stralingspatroon. ’n Literatuurstudie toon dat bestaande TEM horing ontwerpe nie ’n ronde stralingspatroon oor ’n wye bandwydte lewer nie, en dat ’n alternatief nodig is. Die metode van momente is ’n rekenbare elektromagnetiese tegniek wat tipies gebruik word in die ontleding van TEM horing antennas. ’n In-huis metode van momente ontleder is suksesvol ontwikkel om sulke antennas te analiseer en is in staat om die stroomdigtheid op die oppervlak van ’n geleier, sowel as die vêrveld patrone van die antenna te bereken. ’n Wysiging van ’n eksponensiële TEM horing antenna word voorgestel en simulasies toon dat die veranderings suksesvol is om ’n ronde stralingspatroon oor ’n wye bandwydte te skep. Die verander eksponensiële TEM horing het ’n konvekse driehoekige boog aan die einde van elke antenna plaat en is gebou vir meting. Weens beperkte konstruksie vermoëns, toon die metings ’n afwyking van die gesimuleerde resultate, maar dui nogsteeds die potensiaal aan van die struktuur om ’n ronde stralingspatroon te lewer oor ’n wye bandwydte.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis is about the design, simulation and measuring of ultra wide band antennas for use in the Square Kilometre Array (SKA). The SKA is a radio astronomy project with one of the aims of detecting hydrogen particles in deep space. Several thousand antennas over a wide band of frequencies are needed to receive the radiation from these particles. This motivates the need for a low-cost ultra wide band antenna with the focus on the low frequency part of the SKA. In this thesis we present two design strategies: The first design strategy is for a printed LPDA on a substrate and design curves are generated. A scale model was built and measurements did not correlate with simulation results. This is due to manufacturing tolerances and assembly of the pyramidal structure. The second design strategy is for a full scale zig-zag antenna and design curves were also generated. The aim here is to produce a low-cost prototype by using brazing rods for the wire structure and mount it on a wooden frame. A full scale model was built and measurements on the roof produced much interference for the radiation pattern, but the reflection coefficient was good. We suggest doing measurements in an interference free environment in order to achieve the needed results. To conclude we suggest using the zig-zag antenna for the SKA. Some issues do however need more attention as the transformer has some losses, the cross polarisation is probably not good enough and the beamwidth does not reach the specification. We demonstrated a low cost prototype and there is the possibility of low-cost large scale manufacturing but this needs to be addressed. This has however not been analysed as many factors for large scale manufacturing are very difficult to predict beforehand and lies outside the scope of this thesis. / AFRIKAANSE OPSOMMING: Hierdie tesis gaan oor die ontwerp, simulasie en opmeting van ultrawyebandantennas vir gebruik in die SKA ("Square Kilometre Array"). Die SKA is ’n radioastronomie projek met die doel om waterstof partikels op te spoor in die ruimte. Duisende antennas wat oor ’n wye band van frekwensies strek is nodig om die energie van die partikels op te vang. Hieruit is daar ’n aanvraag vir lae-koste ultrawyebandantennas met die fokus op die lae frekwensie deel van die SKA. In hierdie tesis word twee ontwerpstrategieë voorgestel: Die eerste ontwerpstrategie is vir ’n gedrukte logaritmies periodiese dipool reeks (LPDR) op ’n substraat tesame met ontwerpskurwes wat gegenereer word. ’n Skaal model is gebou en die gemete resultate stem nie ooreen met die simulasie nie. Dit kan toegeskryf word aan vervaardigingstoleransies en die aanmekaar sit van die piramide struktuur. Die tweede ontwerpstrategie is vir ’n vol skaal sigsag ("zig-zag") antenna met ontwerpskurwes wat ook gegenereer word. Die doel is om ’n lae-koste prototipe te bou deur sweissoldeerdraad te gebruik vir die draadstruktuur en dan op ’n hout raam te plaas. ’n Vol skaal model is gebou en metings op die dak het baie interferensie veroorsaak vir die stralingsveld, maar tog was die weerkaatskoëffisient goed. Ons stel voor om die metings te herhaal in ’n steuringvrye omgewing om sodoende die korrekte resultate te verkry. Om af te sluit stel ons voor om die sigsag antenna vir die SKA te gebruik. Sekere kwessies soos die transformator wat verlieserig is, die kruispolarisasie wat moontlik nie goed genoeg is nie en die bundelwydte wat nie die spesifikasie haal nie moet nog aandag geniet. Ons het ’n lae-koste prototipe gedemonstreer en daar is die moontlikheid om dit op grootskaalse vervaardiging ook goedkoop te doen, maar dit moet nog uigesorteer word. Dit was wel nie geanaliseer nie, siende dat vele faktore ’n rol speel by grootskaalse vervaardiging wat uiters moeilik is om voor die tyd te voorspel en buite die omvang van die tesis lê.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: The extension of the Karoo Array Telescope (KAT), MeerKAT, will be the most sensitive radio telescope in the southern hemisphere until it is superseded by the completion of the Square Kilometre Array (SKA). These instruments are to be constructed in the Karoo which is an area in South-Africa that is protected against Radio Frequency Interference (RFI) by the Astronomy Geographical Advantage (AGA) act. However, the telescope is also vulnerable to self-generated interference and specialised measurement systems are required to monitor RFI levels. The development of a ReAl Time Transient AnalYser (RATTY) is described and two Experimental Development Models (XDM) are compared. The first uses a mixing philosophy, and the second direct-sampling. The selection of these models was based on the evaluation of several analogue Front-End (FE) designs. A stripline-filter design process is presented along with the results obtained for custom filters developed for the FEs. Several analyses were compared to measurements performed with one of the devices and good agreement was shown between the system characteristics. Issues regarding the Spurious Free Dynamic Range (SFDR) of the FE designs were identified in the process and measurement-corrected simulations used to predict the achievable ranges. The outcome of the XDM comparison promotes the continued development of a direct-sampling strategy to fulfil the short-term goals of the project. A static calibration procedure is demonstrated for the mixing system and implemented to account for different FE configurations. An overview of the digital and software components of the RATTY system is given and Electromagnetic Compatibility (EMC) principles are applied during the construction of both systems. / AFRIKAANSE OPSOMMING: Die finale fase van die Karoo Reeks Teleskoop (KAT), MeerKAT, sal die sensitiefste radio teleskoop in die suidelike halfrond wees. Dit sal egter oortref word deur die vierkante kilometer reeks, wat die sensitiefste radio teleskoop ter wêreld sal word. Beide instrumente sal vatbaar wees vir radiofrekwensie steurings en sal opgerig word in ‘n wet-beskermde omgewing. Die teleskope is ook vatbaar vir radiofrekwensie steurings wat deur interne stelsels opgewek kan word. Dus word gespesialiseerde meetapparate benodig om die betrokke area en substelsels van die teleskope te monitor. Die ontwikkeling van ‘n meetinstrument vir die ontleding van kort-durasie tydseine (RATTY) word beskryf en twee eksperimentele ontwikkelings modelle word vergelyk. Hierdie modelle is gebaseer op die verfyning van voorafgaande ontwerpe vir die analoog substelsel van die instrument en hierdie proses word verduidelik. Die eerste model volg ‘n menger strategie waar die tweede model direkte-monstering implementeer. ‘n Dubbel-laag, mikrostrookfilter ontwerpsproses word beskryf en die gemete resultate vir die ontwikkelde filters word bespreek. Verskeie ontledings is aangewend en vergelyk met die gemete resultate van die stelsels. Hieruit word bevredigende ooreenkomste getref. Die beperkings van die modelle, weens interne distorsie, word geïdentifiseer in dié proses en verdere skattings word gemaak d.m.v. simulasies. Die eksperimentele modelle word vergelyk en die voorkeur van ‘n direkte-monsterings stelsel word gemotiveer. Die digitale en sagteware komponente word oorsigtelik behandel. Tydens die konstruksie van die modelle word die toepassing van elektromagnetiese verenigbaarheids beginsels verduidelik. Laastens word ‘n eenvoudige kalibrasie toegepas op die menger stelsel en ‘n toepassing daarvan word behandel.

The largest 21st century radio telescope, the Square Kilometre Array (SKA) is now being planned, and the first phase of construction is estimated to commence in the year 2016. Phased array technology, the key feature of the SKA, requires the use of a tremendous number of receivers, estimated at approximately 37 million. Therefore, in the context of this project, the Low Noise Amplifier (LNA) located at the front end of the receiver chain remains the critical block. The demanding specifications in terms of bandwidth, low power consumption, low cost and low noise characteristics make the LNA topologies and their design methodologies one of the most challenging tasks for the realisation of the SKA. The LNA design is a compromise between the topology selection, wideband matching for a low noise figure, low power consumption and linearity. Considering these critical issues, this thesis describes the procedure for designing a monolithic microwave integrated circuit (MMIC) LNA for operation in the mid frequency band (400 MHz to 1.4 GHz) of the SKA. The main focus of this work is to investigate the potential of MMIC LNA designs based on a novel InGaAs/InAlAs/InP pHEMT developed for 1 µm gate length transistors, fabricated at The University of Manchester. An accurate technique for the extraction of empirical linear and nonlinear models for the fabricated active devices has been developed. In addition to the linear and nonlinear model of the transistors, precise models for passive devices have also been obtained and incorporated in the design of the amplifiers. The models show excellent agreement between measured and modelled DC and RF data. These models have been used in designing single, double and differential stage MMIC LNAs. The LNAs were designed for a 50 Ω input and output impedance. The excellent fits between the measured and modelled S-parameters for single and double stage single-ended LNAs reflects the accurate models that have been developed. The single stage LNA achieved a gain ranging from 9 to 13 dB over the band of operation. The gain was increased between 27 dB and 36 dB for the double stage and differential LNA designs. The measured noise figures obtained were higher by ~0.3 to ~0.8 dB when compared to the simulated figures. This is due to several factors which are discussed in this thesis. The single stage design consumes only a third of the power (47 mW) of that required for the double stage design, when driven from a 3 V supply. All designs were unconditionally stable. The chip sizes of the fabricated MMIC LNAs were 1.5 x 1.5 mm2 and 1.6 x 2.5 mm2 for the single and double stage designs respectively. Significantly, a series of differential input to single-ended output LNAs became of interest for use in the Square Kilometre Array (SKA), as it utilises differential output antennas in some of its configurations. The single-ended output is preferable for interfacing to the subsequent stages in the analogue chain. A noise figure of less than 0.9 dB with a power consumption of 180 mW is expected for these designs.

Title: “All roads here always lead to irony”. Verbal irony as a mean of presenting dandyismin the novels ‘Faserland’, by Christian Kracht and ‘Att komma hem ska vara en schlager’, byPer Hagman. A contrastive analysis. Author: Hanna JulinSupervisor: Bärbel WestphalExaminator: Corina Löwe Summary: The aim of this study is to investigate how verbal irony is used in fiction to indicatedandyism in pop-modern literature. It is a contrastive study based on Christian Kracht’s novelFaserland (1995), which is considered to be a romana à clef in the German popliterature. Attkomma hem ska vara en schlager (2004), by Per Hagman is a Swedish novel comparative tothe German „pop-novel“. The analysis has shown that the verbal irony primarily has threefunctions: social criticism, distancing and self-criticism. These elements correspond withdistinctive features which are typical of the dandy. Irony itself, according to Barbey (1987),Schickedanz (2000) and Rauen (2010) among others, is a distinctive feature of the classicaldandy figure, as well as of the pop-modern one. However, further research consisting of bothsynchronic, diachronic and contrastive analysis is relevant, as the dandy, according to Hörner(2008) and Tietenberg (2012) among others, always renews himself – so that his image alwaysappears elegant, modern, original and rebellious in his contemporary society.

La presente investigación emplea un caso extremo, el de las bandas ska del bar de Bernabé entre el 2005 y 2007 para dar cuenta de las formas de organización de las escenas musicales alternas en Lima. Se presentan los procesos históricos constitutivos de los géneros musicales en sus contextos de origen durante las tres olas del ska, las escenas musicales alternas limeñas y el ska en Lima. Luego se observan las lógicas de articulación de personas-bandas-colectivos-escenas, como sistemas complejos autoorganizados. A continuación se profundiza en cuáles son las prácticas y estrategias para la producción musical que se constatan en el medio urbano limeño, repasando cada función de la cadena de labores para la realización de ensayos, repertorios y conciertos. Luego se observa cuáles son las dinámicas de circulación de repertorios propios y ajenos, refiriendo a los macro circuitos de distribución musical y los medios masivos oficiales de difusión musical en Lima. Finalmente refiere a cómo el concierto se constituye en una instancia de articulación ritual en el que los cultores concretan el consumo musical mediante la comunicación pública de las obras creadas. Al detallar estos procesos y dinámicas, podemos responder a nuestra pregunta de investigación, planteando que: Las escenas musicales alternas emplean la organización colectiva para la producción musical; el uso estratégico del capital social para el manejo de ciclos productivos paralelos, con lógicas propias, según cada contexto, articulando personas de todo origen sociocultural. Estas posibilidades de conducta, con sus aportes, conflictos y contradiccciones, constituyen una parte fundamental de los medios de producción musical en el medio urbano limeño. Son medios de producción de sentido, para cuya realización se articulan diversas cadenas productivas, generando bienes y servicios culturales que son constitutivos de las realidades personales y colectivas experimentadas por sus cultores. Son parte fundamental de nuestras culturas urbanas

Sociala konsekvensanalyser är en process som handlar om att beskriva, analysera och hantera avsiktliga och oavsiktliga sociala konsekvenser som uppkommer som en följd av planerad stadsutveckling. Syftet med studien är att skapa ökad kunskap kring teori och praktik i sociala konsekvensanalyser genom att jämföra teorier om social rättvisa och aktuell forskning med ett praktiskt exempel i anslutning till infrastrukturprojektet “Västlänken” i Göteborg. Studien kommer även att undersöka om det finns några eventuella utmaningar i den praktiska tillämpningen av sociala konsekvensanalyser. Vidare syftar studien till att få insikt i på vilket sätt en social konsekvensanalys potentiellt kan påverka social rättvisa. Resultatet visar att det förekommer utmaningar kring en gemensam förståelse och definition av området, avsaknad av en gemensam modell samt en brist på kompetens inom social hållbarhet och social rättvisa. Studien föreslår att det införs ett lagkrav på sociala konsekvensanalyser och utformning av en nationell modell med utgångspunkt i teorier om social rättvisa. Att inkludera sociala konsekvensanalyser i planeringsprocessen innebär att ta ställning till ett antal komplexa frågor, nödvändiga för att nå fram till ett rättvist och socialt hållbart samhälle. / Impact Assessments are common tools in urban planning, used to predict future consequences of a certain project. This study focuses on the Social Impact Assessment, which is about the processes of describing, analyzing and managing the intended and unintended social consequences of planned interventions. The purpose of the study is to create an understanding of the theory and practice in Social Impact Assessments and in what way the Social Impact Assessment could have the potential to affect social justice. This will be accomplished by comparing existing research within the subject and theories about social justice with the Social Impact Assessment carried out in an infrastructure project called "Västlänken" in Gothenburg, Sweden. The study also explores if there are any particular challenges in the field of Social Impact Assessments and its practical application. The results show that there are challenges around the common understanding and definition of the field, absence of a common model and a lack of expertise in social sustainability and social justice. The study proposes that the Social Impact Assessment becomes a legal requirement in Sweden and that a national model based on theories of social justice will be created. Including Social Impact Assessments in the planning process means taking a stand in a variety of difficult questions, necessary in the aim for a just and socially sustainable society.

Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: South Africa and Australia are now the two remaining countries bidding for the Square Kilometre Array (SKA), the biggest and most sensitive project ever undertaken in radio astronomy. The South African SKA is demonstrating its technology capabilities through the Karoo Array Telescope (KAT or MeerKAT). The development of KAT is taking place in stages to optimise design and minimise risks at each stage. An array of seven 12 m antennas will be complete by the end of 2009, called KAT-7. The following phase will see the construction of MeerKAT, which will lead to eighty arrayed dishes. Lightning and RFI studies for KAT-7 are the focus of this dissertation. Due to the extent and complexity of the South African demonstrator project, these studies have largely been conducted on a single structure. Parameters for the dish antenna and pedestal design changed throughout their development. To be effective, the doctoral research had to track these changes appropriately. A Method of Moments frequency domain computational electromagnetic code, FEKO, is used throughout the study. The consequences of direct and indirect lightning strikes are examined for the KAT-7 structure. Important FEKO model verification is achieved through measurement of physical scale models in an anechoic chamber. The microwave simulation code, CST, gives direct comparison of FEKO results by using a finite volume time domain method of calculation. Using frequency domain analysis on these models, the lightning down conductor design over the dish antenna bearings is optimised with cost-effectiveness as one driving parameter. RFI coupling levels for different designs are compared to each other to identify areas requiring RFI mitigation. Analysis of resonances enables evaluation of the mitigation at frequencies sensitive to radio astronomy. A Sommerfeld integral ground plane is used together with the computational model to investigate the use of the concrete foundation steel reinforcing as part of the lightning earthing electrode system. Different interconnections of the steel reinforcing elements are critically evaluated. The KAT-7 design incorporated clear lightning protection and RFI mitigation policies derived from recommendations contained within this dissertation. / AFRIKAANSE OPSOMMING: Suid-Afrika en Australie is nou die oorblywende twee lande wat bie vir die Vierkante Kilometer Reeks (SKA), die grootste en mees sensitiewe projek nog ooit in radio astronomie onderneem. Die Suid Afrikaanse SKA demonstreer sy tegnologiese bekwaamheid met die Karoo Reeks Teleskoop (KAT of MeerKAT). Die ontwikkeling van KAT vind plaas in fases om die ontwerp te optimaliseer en risikos te minimaliseer met elke fase. ’n Reeks van sewe 12 m antennas, genaamd KAT-7, sal teen die einde van 2009 klaar wees. Die volgende fase behels die konstruksie van MeerKAT, wat sal lei tot ’n tagtig-skottel reeks. Die fokus van hierdie proefskrif hanteer weerlig en radiofrekwensie steurings (RFS) vir KAT-7. As gevolg van die omvang en kompleksiteit van die Suid-Afrikaanse demonstreerder projek, is die studies hoofsaaklik op een struktuur gedoen. Parameters vir die antenna-skottel en -voetstuk ontwerp het met hul ontwikkeling deurgaans verander. Om effektief te wees, moes die doktorale navorsing hierdie veranderinge toepaslik volg. ’n Metode-van-Momente frekwensiedomein rekenaar elektromagnetiese kode, FEKO, is deurgaans met die studie gebruik. Die gevolge van direkte en indirekte weerligslae vir die KAT-7 struktuur is ondersoek. Belangrike FEKO model bevestiging is bereik met metings van skaalmodelle in ’n anego¨ıse kamer. Die mikrogolf-simulasie kode, CST, gee ’n direkte vergelyking met die FEKO resultate deur ’n eindige-volume-tyd-domein metode van berekening te gebruik. Met behulp van frekwensiedomein analise van hierdie modelle, is die weerligafleierontwerp oor die antenna-skottel laers ge-optimaliseer, met koste-effektiwiteit as een van die drywingsparameters. RFS koppelingsvlakke vir onderskeie ontwerpe is teen mekaar opgeweeg om areas te identifiseer wat RFS tempering benodig. Analise van resonansies stel die evaluering van die tempering in staat teen frekwensies wat sensitief is vir radio astronomie. ’n Sommerfeld integrale grondvlak word saam met die rekenaarmodel gebruik om die insluiting van die beton se staalversterking as deel van die aardingselektrodestelsel te ondersoek. Verskillende bindmetodes van die onderlinge staalversterkingselemente word krities ge¨evalueer. Die KAT-7 ontwerp inkorporeer duidelike weerligbeveiligings- en RFS temperingstrategie ¨e, komende van aanbevelings in hierdie proefskrif omskryf

Thesis (PhD)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: Superconducting electronics can make the Square Kilometre Array (SKA) a better instrument. The largest radio telescope in the world will consist of several arrays, the largest of which, consisting of more than 3000 dishes, will be situated primarily in South Africa. The ambitions of the SKA are grand and their realisation requires technology that does not exist today. Current plans see signals in the band of interest ampli ed, channelised, mixed down and then digitised. An all-digital frontend could simplify receiver structure and improve its performance. Semiconductor (analog-to-digital converters) ADCs continue to make great progress and will likely nd applications in the SKA, but superconductor ADCs bene t from higher clock speeds and quantum accurate quantisation. We propose a superconducting softwarede ned radio frontend. The key component of such a frontend is a superconducting ash ADC. We show that employing such an ADC, even a small- to moderately-sized one, will signi cantly improve the instantaneous bandwidth observable by the SKA, yet retain adequate signal-to-noise ratio so as to achieve a net improvement in sensitivity. This improvement could approach factor 2 when compared to conventional technologies (at least for continuum observations). We analyse key components of such an ADC analytically, numerically and experimentally and conclude that fabrication of such an ADC for SKA purposes is certainly possible and useful. Simultaneously, we address the power requirements of high-performance computing (HPC). HPC on a hitherto unprecedented scale is a necessity for processing the vast raw data output of the SKA. Utilising the ultra-low-energy switching events of superconducting switches (certain Josephson junctions), we develop rst demonstrators of the promising eSFQ logic family, achieving experimentally veri ed shift-registers and deserialisers with sub-aJ/bit energy requirements. We also propose and show by simulation how to expand the applicability of the eSFQ design concept to arbitrary (unclocked) gates. / AFRIKAANSE OPSOMMING: Supergeleier-elektronika kan 'n beter instrument maak van die \Square Kilometre Array" (SKA). Die wêreld se grootse radioteleskoop sal bestaan uit etlike skikkings, waarvan die grootste - met meer as 3 000 skottels - hoofsaaklik in Suid-Afrika gesetel sal wees. Die SKA is ambisieus en vereis tegnologie wat nog nie vandag bestaan nie. Volgens huidige planne sal seine in die band van belang versterk, gekanalisieer, afgemeng en dan versyfer word. 'n Heel-digitale kopstuk sal die ontvangerstruktuur kan vereenvoudig en sy prestasie kan verbeter. Halfgeleier analoog-na-digital omsetters (ADOs) verbeter voortdurend en sal waarskynlik toepassings in die SKA vind, maar supergeleier ADOs trek voordeel uit hoër klok spoed en kwantumakkurate kwantisering. Ons stel 'n supergeleier sagteware-gede nieerde radio kopstuk voor. Die sleutelkomponent van so 'n kopstuk is 'n supergeleier \ ash" ADO. Ons toon hoe die gebruik van so 'n ADO, selfs een van klein tot matige bisgrootte, die oombliklike bandwydte waarneembaar deur die SKA aansienlik sal verbeter en 'n voldoende sein-tot-ruis verhouding sal behou, en gevolglik 'n netto verbetering in sensitiwiteit sal bereik. Hierdie verbetering kan, vergeleke met konvensionele tegnologie, 'n faktor van 2 nader (ten minste vir kontinuum waarnemings). Ons analiseer belangrike komponente van so 'n ADO analities, numeries and eksperimenteel en lei af dat die vervaardiging van so 'n ADO vir SKA doeleindes beide moontlik en nuttig is. Terselfdertyd spreek ons die drywingsverkwisting van Hoë-verrigting rekenaars aan. Sulke rekenaars van 'n tot dusver ongekende skaal is 'n noodsaaklikheid vir die verwerking van die enorme rou data uitset van die SKA. Deur die gebruik van die ultra-lae-energie skakels van supergeleier skakelaars (sekere Josephson-vlakke), ontwikkel ons die eerste demonstratiewe hekke van die veelbelowende eSFQ logiese familie, en toon eksperimenteel bevestigte skuifregisters en deserieëliseerders met sub-aJ/bis energievereistes. Ons stel verder voor en wys met simulasies hoe om die toepaslikheid van die eSFQ ontwerpkonsep na arbitr^ere (ongeklokte) hekke uit te brei.

The Square Kilometre Array (SKA) is a multibillion and a multinational science project to build the world’s largest and most sensitive radio telescope. For a very large field of view, the combined collecting area would be one square kilometre (or 1, 000, 000 square metre) and spread over more than 3,000 km wide which will require a massive count of antennas (thousands). Each of the antennas contains hundreds of low noise amplifier (LNA) circuits. The antenna arrays are divided into low, medium and high operational frequencies and located at different positions to boost up the telescope’s scanning sensitivity.The objective of this work was to develop and fabricate fully on-chip LNA circuits to meet the stringent requirements for the mid-frequency array from 0.4 GHz to 1.4 GHz of the SKA radio astronomy telescope using Monolithic Microwave Integrated Circuit technology (MMIC). Due to the number of LNA reaching figures of millions, the fabricated circuits were designed with the consideration for low cost fabrication and high reliability in the receiver chain. Therefore, a relaxed optical lithography with Lg = 1 µm was adopted for a high yield fabrication process.Towards the fulfilment of the device’s low noise characteristics, a large number of device designs, fabrication and characterisation of InGaAs/InAlAs/InP pHEMTs were undertaken. These include optimisations at each critical fabrication steps. The device’s high breakdown and very low gate leakage characteristics were further improved by a combination of judicious epitaxial growth and manipulation of materials’ energy gaps. An attempt to increase the device breakdown voltage was also employed by incorporating Field Plate structure at the gate terminal. This yielded the devices with improvements in the breakdown voltage up to 15 V and very low gate leakage of 1 µA/mm, in addition to high transconductance (gm) characteristic. Fully integrated double stage LNA had measured NF varying from 1.2 dB to 1.6 dB from 0.4 GHz to 1.4 GHz, compared with a slightly lower NF obtained from simulation (0.8 dB to 1.1 dB) across the same frequency band.These are amongst the attractive device properties for the implementation of a fully on-chip MMIC LNA circuits demonstrated in this work. The lower circuit’s low noise characteristic has been demonstrated using large gate width geometry pHEMTs, where the system’s noise resistance (Rn) has successfully reduced to a few ohms. The work reported here should facilitate the successful implementation of rugged low noise amplifiers as required by SKA receivers.