Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The use of Focal Plane Arrays (FPAs) as suitable feed-structures for the Parabolic Dish Reflector antennas that are intended to form a large part of the Square Kilometre Array (SKA) is currently the topic of conversation in various SKA research groups. The simulation of these structures however, relies on intensive computational resources, which can result in very long simulation runtimes - a serious problem for antenna designers. It was the purpose of the research to investigate efficient simulation techniques, based on the Method of Moments (MoM). In this thesis, the reader will be introduced to ways of improving FPA design by using resources such as High Performance Clusters, developing efficient MoM formulations for FPAs such as the Vivaldi antenna array and by developing efficient solution techniques for the resulting MoM equations by using techniques such as the Characteristic Basis Function Method (CBFM). In addition to the above mentioned methods, the concept of distributed computing is explored as a way to further aid the antenna designer in obtaining desired results in a reasonable time and with sufficient accuracy. / AFRIKAANSE OPSOMMING: Die gebruik van Fokus Punt Samestellings (FPS) vir die voer van Paraboliese Skottel Antennas in die Square Kilometer Array (SKA), geniet tans baie aandag in verkeie navorsing-sirkels. Die analise van hierdie samestellings vereis egter intensiewe berekenings-infrastrukture, wat tot lang simulasies kan lei - ’n ernstige probleem vir antenna ontwerpers. Die doel van die skrywer se navorsing was om effektiewe simulasie metodes te ondersoek, gebaseer op die Moment Metode. In hierdie tesis, sal die leser bekendgestel word aan verskeie metodes om die ontwerp van Fokus Punt Samestellings doeltreffend te verrig; nl. die gebruik van Parallel Rekenaar Klusters, die ontwikkeling van effektiewe Moment Metode kode vir samestellings soos die Vivaldi antenna konfigurasie, asook die ontwikkeling van effektiewe oplos-metodes vir die matrikse wat deur die Moment Metode gelewer word, deur die sogenaamde Karakteristieke Basis Funksie Metode (KBFM) te gebruik. Hierby ingesluit word die konsep van verspreide numeriese berekening ondersoek, as ’n manier waarop die antenna ontwerper resultate binne ’n aanvaarbare tyd en akkuraatheid kan verkry.

Philosophiae Doctor - PhD / Next-generation galaxy surveys will usher in a new era of high precision cosmology. They will increasingly rely on the galaxy bispectrum to provide improved constraints on the key parameters of a cosmological model to percent level or even beyond. Hereby, it is imperative to understand the theory of the galaxy bispectrum to at least the same level of precision. By this, we mean to include all the general relativistic projection effects arising from observing on the past lightcone, which still remains a theoretical challenge. This is because unlike the galaxy power spectrum, the galaxy bispectrum requires these lightcone corrections at second-order. For the rst time, this PhD project looks at all the local relativistic lightcone e ects in the galaxy bispectrum for a at Friedmann-Lemaitre-Robertson-Walker Universe, giving full details on the second-order scalars, vectors and tensors. These lightcone effects are mostly Doppler and gravitational potential contributions. The vector and tensor modes are induced at second order by scalars. We focus on the squeezed shapes for the monopole of the galaxy bispectrum because non-Gaussianity of the local form shows high signatures for these triangular con gurations. In the exact squeezed limit, the contributions from the vectors and tensors vanish. These relativistic projection effects, if not included in the analysis of observations, can be mistaken for primordial non-Gaussianity. For future surveys which will probe equality scales and beyond, all the relativistic corrections will need to be considered for an accurate measurement of primordial non-Gaussianity.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: This thesis presents the design, construction and measurement of two wide-band LNA’s for the SKA-Mid range (350-1200 MHz). The first wide-band LNA involves the investigation of classic low noise amplifier techniques, which includes basic noise theory, stability analysis, feedback design and the development of sophisticated matching techniques for ultra wide-band performance. Final measurements show a flat gain response equal to 19 dB, with a noise figure of 1.5 dB and an output return loss of 10 dB across the entire bandwidth. A multi-path cascading concept is introduced for the second low noise amplifier design, which aims to connect two single frequency amplifiers in parallel to operate from 500 to 700 MHz. The design process involves several optimization schemes to realise the matching networks for the cascaded topology and the noise performance of the device was confirmed by using multi-port noise theory. The prototype presents significant bandwidth improvements compared to a single frequency LNA design. Excellent agreement between the simulation and measurement were obtained with a flat gain response of 20 dB across a 2:1 bandwidth, with a low noise figure of 0.95 dB and an output return loss of 13 dB across the operation bandwidth of 400 to 800 MHz. / AFRIKAANSE OPSOMMING: Hierdie tesis behandel die ontwerp, konstruksie en meting van twee wyeband laeruis versterkers vir die SKA - Mid reeks (350–1200 MHz). Die eerste wyeband laeruis versterker, ondersoek klassieke laeruis versterker tegnieke wat insluit basiese ruisteorie, stabiliteit analise, terugvoerontwerp en die ontwikkeling van gevorderde aanpassingstegnieke vir ultra wyeband werkverrigting. Finale metings het ’n plat aanwins van 19 dB, met ’n ruisfiguur van 1.5 dB en ’n uittree-refleksie koëffisiënt van -10 dB oor die hele bandwydte vertoon. ’n Multi-pad konsep word bekend gestel vir die tweede laeruis versterker. Die ontwerp het twee enkel frekwensie laeruis versterkers in parallel verbind om vanaf 500 tot 700 MHz te werk. Die ontwerp proses bevat verskeie optimalisering skemas om die aanpassings netwerke vir die kaskade topologie te realiseer. Die ruissyfer van die versterker is bevestig deur die gebruik van multi-pad ruisteorie. Die prototipe het beduidende bandwydte verbeterings vertoon in vergelyking met ’n enkel frekwensie versterker ontwerp. ’n Uitstekende ooreenkoms tussen die simulasie en meting was verkry met ’n plat aanwins van 20 dB oor ’n 2:1 bandwydte, met ’n laeruisfiguur van 0.95 dB en ’n uittree-refleksie koëffisiënt van -13 dB oor die bandwydte van 400-800 MHz.

Masters of Science / The study of the faint radio universe and of its properties has recently become a very active field of research not only because of the much improved capabilities of the SKA pathfinders but also because of the need to better plan for SKA surveys. These new facilities will map large areas of the sky to unprecedented depths and transform radio astronomy into the leading technique for investigating the complex processes which govern the formation and evolution of galaxies. This thesis combines multi-wavelength techniques, highly relevant to future deep radio surveys, to study the properties of faint radio sources. The nature of the faint radio sources is presented, over a large GMRT survey area of an area of 1.2 deg2 comprising 2800 sources. Utilising multi-wavelength data we have matched 85% of the radio population to Spitzer/IRAC and obtained a redshift estimate for 63%. The redshift associations are a combination of photometric and spectroscopic redshift estimates. This study investigates several multi-wavelength diagnostics used to identify AGN, using radio, infrared, optical and x-ray data . This analysis shows that various diagnostics (from the radio through the X-ray ones) select fairly different types of AGNs, with an evidence of a disagreement in the number of AGNs selected by each individual diagnostics. For the sources with redshift we use a classification scheme based on radio luminosity, x-ray emission, BOSS/SDSS spectroscopy, IRAC colors satisfying the Donley criterion, and MIPS 24ɥm radio-loud AGN criteria to separate them into AGNs and SFGs. On the basis of this classification, we find that at least 12.5% of the sources with redshifts are AGNs while the remaining 87.5% are adopted as SFGs. We explore the nature of the classified sources through the far-infrared radio correlation. We measure a median qIR value of 2:45± 0:01 for the SFGs and qIR value of 2:27 ± 0:05 for the AGNs. The decrease in the median value of qIR for the AGNs is a result of the additional AGN component to radio emission for the AGN-powered sources and find tentative evidence of an evolution of the qIR with redshift.

Thesis (PhD)--Stellenbosch University, 2015. / AFRIKAANSE OPSOMMING : Die vierkantkilometer-radioteleskoop SKA (―Square Kilometre Array‖) sal na verwagting die grootste teleskoop op aarde en die grootste wetenskapprojek in Afrika wees. Hierdie verhandeling konsentreer op hoe die SKA vanaf September 2011 tot Augustus 2012 in die Suid-Afrikaanse media uitgebeeld is. Dit handel oor die leemtes in die literatuur oor wetenskapkommunikasie, veral wat betref wetenskapkommunikasie in Afrikaverband. Deur uit massa- en wetenskapkommunikasieteorie te put, modelleer die studie kommunikasieprosesse en -uitsette met behulp van ‘n konseptuele raamwerk wat op die gedagte van die openbare sfeer berus. Die navorsing word in die besonder onderstut deur onderhoude met sleutelinformante en die ontleding van nuus- en sosiale media. Die wetenskapkommunikasie oor die SKA gedurende hierdie tydperk was stelselmatig gekenmerk deur ‘n hoë vlak van koördinasie tussen die aansporings, strategieë en strukture van alle hoofrolspelers oor die kommunikasiestelsel heen. Al die hoofrolspelers buite die media het die SKA op so ‘n manier in die openbare sfeer probeer uitbeeld dat dit openbare steun sou werf. Primêre hekwagterfunksies is aan die voorste SKA-organisasie- en openbaresektor-rolspelers toegewys, maar was verder afgewentel binne universiteite. Hekwagterfunksies in die media is hoofsaaklik deur nuuswaarde sowel as institusionele kultuur en organisatoriese kenmerke bepaal. Verhoudings tussen wetenskaplikes en joernaliste was oënskynlik oor die algemeen positief en gegrond op vertroue. Die beduidendste bron van inligting vir joernaliste was die SKA self, gevolg deur rolspelers in die openbare sektor. Tog is ander rolspelers, bepaald plaaslike belanghebbendes, gemarginaliseer. Die Afrikaanstalige media het veral onder plaaslike gemeenskappe ‘n belangrike rol gespeel en het meer dikwels as ander oor die SKA berig. Die sosiale media het die SKA merendeels op ‘n soortgelyke wyse as die nuusmedia hanteer, maar die struktuur van kommunikasie-uitsette is beïnvloed deur die kenmerkende eienskappe van sosiale media self, waaronder die virale verspreiding van boodskappe en hoër vlakke van vryewilsoptrede (―agency‖) deur individuele rolspelers. Tog was daar aanduidings van beduidende media-integrasie, in die sin dat groot Suid-Afrikaanse mediahuise die bron was van die meeste boodskappe in sowel die nuus- as sosiale media. / ENGLISH ABSTRACT : The Square Kilometre Array (SKA) radio telescope is set to become the largest telescope on Earth, and also the largest science project in Africa. This dissertation focuses on the manner in which the SKA was represented in the South African media from September 2011 to August 2012. This addresses gaps in the literature on science communication, particularly with respect to science communication in an African context. By drawing on mass communication theory and science communication theory, it models communication processes and outputs using a conceptual framework based on the notion of the public sphere. Empirically, the study is underpinned by key informant interviews and the analysis of news media and social media content. Systemically, the science communication of the SKA during this period was characterized by a high level of alignment of incentives, strategies, and structures across the main actors in the communication system. Main actors outside the media all aimed to position the SKA in the public sphere in a manner that would grow public support. Primary gatekeeping functions were positioned at the apex of the SKA organisation and public sector actors, but were more devolved within universities. Gatekeeping in the media was primarily driven by news value, as well as institutional culture and organisational attributes. Relationships between scientists and journalists were found to be generally positive and trust-based. The most significant source of information for journalists was the SKA itself, followed by public sector actors. However, other actors were marginalized, particularly local stakeholders. The Afrikaans language media played an important role, particularly among local communities, and published about the SKA relatively more often. The social media represented the SKA in a broadly similar manner to the news media, but the structure of communication outputs was influenced by the distinct attributes of the social media, including the viral propagation of messages and higher levels of agency by individual actors. However, there were indications of substantial media integration, in that major South African media corporations were the source of the majority of messages in both the news and social media. The tone of media outputs was largely neutral or positive, framing the SKA as a 'good news story‘. The overarching dominant frame for representing the SKA was the site allocation process, in which South Africa and Australia competed in a bid to host the telescope for the international SKA consortium. Science and technology aspects of the project constituted the second most common framing, within which the search for extra-terrestrial intelligence was the most commonly represented research question. Representations of technological aspects of the SKA were generally shallow, with most articles mentioning only one aspect of the project‘s technology. The SKA was also constructed as a symbol, representing an instance of African scientific and technological achievement, African participation in globalized science, and a refutation of Afro-pessimism. The impact of the SKA on the public imagination, and the public sphere, was thus clearly far wider and deeper than only its science and technology accomplishments and contributions.

>Magister Scientiae - MSc / The growth rate of large-scale structure is a key probe of gravity in the accelerating Universe. Standard models of Dark Energy within General Relativity predict essentially the same growth rate, whereas Modified Gravity theories without Dark Energy predict a different growth rate. Redshift-space distortions lead to anisotropy in the power spectrum, and extracting the monopole and quadrupole allows us to determine the growth rate and thus test theories of gravity. We investigate redshift-space distortions in the intensity maps of the 21cm emission line of neutral hydrogen (HI) in galaxies after the Epoch of Reionization: HI intensity mapping delivers very accurate redshifts. We first use the standard approach based on the Fourier power spectrum. Then we explored an alternative approach, based on the spherical-harmonic angular power spectrum. Fisher forecasting was used to make predictions of the accuracy with which MeerKAT will measure the growth rate parameter, via the proposed MeerKAT Large Area Synoptic Survey (MeerKLASS). Then we extend the forecasts to consider the planned HI intensity mapping survey in Phase 1 of the Square Kilometre Array. These forecasts enable us to predict at what level of accuracy General relativity and various alternative theories could be ruled out.

Masters of Science / Upcoming and ongoing 21cm surveys, such as the Square Kilometre Array (SKA), Hydrogen Epoch of Reionization Array (HERA) and Low Frequency Array (LOFAR), will enable imaging of the neutral hydrogen distribution on cosmological scales in the early Universe. These experiments are expected to generate huge imaging datasets that will encode more information than the power spectrum. This provides an alternative unique way to constrain the astrophysical and cosmological parameters, which might break the degeneracies in the power spectral analysis. The global history of reionization remains fairly unconstrained. In this thesis, we explore the viability of directly using the 21cm images to reconstruct and constrain the reionization history. Using Convolutional Neural Networks (CNN), we create a fast estimator of the global ionization fraction from the 21cm images as produced by our Large Semi-numerical Simulation (SimFast21). Our estimator is able to efficiently recover the ionization fraction (xHII) at several redshifts, z = 7; 8; 9; 10 with an accuracy of 99% as quantified by the coefficient of determination R2 without being given any additional information about the 21cm maps. This approach, contrary to estimations based on the power spectrum, is model independent. When adding the thermal noise and instrumental effects from these 21cm arrays, the results are sensitive to the foreground removal level, affecting the recovery of high neutral fractions. We also observe similar trend when combining all redshifts but with an improved accuracy. Our analysis can be easily extended to place additional constraints on other astrophysical parameters such as the photon escape fraction. This work represents a step forward to extract the astrophysical and cosmological information from upcoming 21cm surveys.

Thesis (PhD)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The Square Kilometre Array (SKA) and its demonstrator MeerKAT are being designed to operate over a wide frequency range and are expected to achieve greater sensitivity and resolution than existing telescopes. The radio astronomy community is well aware of the negative impact that radio frequency interference (RFI) has on observations in the proposed frequency band. This is because weak radio signals such as those from pulsars and distant galaxies are difficult to detect on their own. The presence of RFI sources in the telescope’s operating area can severely corrupt observation data, leading to inaccurate or misleading results. Power-line interference and radiation from electric fences are examples of RFI sources. Mitigation techniques for these interference sources in the SKA system’s electromagnetic environment are essential to ensure the success of this project. These techniques can be achieved with appropriate understanding of the characteristics of the noise sources. Overhead power-line interference is known to be caused mainly by corona and gap-type (commonly known as sparking noise) discharges. Sparking noise is the dominant interference for the SKA. It is mainly encountered on wooden pole lines, which are usually distribution lines operated at up to 66 kV AC in the South African network. At this voltage level, the voltage gradients on the lines are insufficient to generate conductor corona. The power requirements for SKA precursors will be below this voltage level. The aim of the research in this dissertation is to evaluate the power line sparking characteristics through measurements and simulation of line radiation and propagation characteristics. An artificially made sparking noise generator, which is mounted on a power line, is used as noise source and the radiation characteristics are measured. Measurements were carried out in different environments, which included a high-voltage laboratory (HV-Lab), a 40m test-line, and another 22-kV test line of approximately 1.5 km. The key sparking noise parameters of interest were the temporal and spectral characteristics. The time domain features considered were the pulse shape and the repetition rate. The lateral, longitudinal and height attenuation profiles were also quantified. Since sparking noise current pulses are injected or induced onto power line conductors, the line will act as an unintentional antenna. The far-field radiation characteristics of the line were evaluated through measurements on physical scale-model structures and simulations. 1/120th and 1/200th scaled lines, using an absorbing material and metallic ground planes, respectively, were simulated in FEKO. The measurements of the constructed scale models were taken in the anechoic chamber. Both measurements and simulations showed that the line exhibits an end-fire antenna pattern mode. Line length, pulse injection point and line configuration were some of the parameters found to affect the radiation patterns. The findings from this study are used to determine techniques to identify the sparking noise, and locate and correct the sources when they occur on the line hardware. Appropriate equipment is recommended to be used for the location and correction of sparking noise. / AFRIKAANSE OPSOMMING: Die Vierkante Kilometer Reeks (SKA) en sy demonstrasie projek, die Karoo Reeks Teleskoop (KAT), word ontwerp om oor 'n wye frekwensie-bereik te funksioneer. Beide sal na verwagting beter sensitiwiteit en resolusie as bestaande radioteleskope he. Die radio-astronomie-gemeenskap is deeglik bewus van die negatiewe impak wat radio-frekwensie steurnisse (RFS) op waarnemings in die voorgestelde frekwensieband het. Die rede hiervoor is dat swak radio-seine soos die van pulsars en verafgelee sterrestelsels inherent moeilik is om te bepaal. Die teenwoordigheid van RFS bronne in die teleskoop se onmiddellike operasionele gebied kan waarnemings nadelig beinvloed. Dit lei uiteindelik tot onakkurate of misleidende resultate. Kraglyne en uitstralings van elektriese heinings is voorbeelde van RFS bronne. Metodes om die oorsake van die steurnisse van die SKA se elektromagnetiese omgewing te verminder is noodsaaklik om die sukses van hierdie projekt te verseker. Dit vereis egter deeglike begrip van die eienskappe van hierdie bronne. Steurnisse as gevolg van oorhoofse kraglyne word hoofsaaklik veroorsaak deur korona en gapingtipe ontladings (algemeen bekend as vonkontladings). Vonkontladings word hier beskou as die belangrikste oorsaak van steurnisse vir die SKA. Dit word in die Suid-Afrikaanse netwerk hoofsaaklik aangetref op houtpaal-installasies, wat gewoonlik bestaan uit distribusie lyne wat tot en met 66 kV wisselstroom (WS) bedryf word. By hierdie operasionele spanning is die spanningsgradient op die lyn onvoldoende om korona op te wek. Die kragvereistes vir die SKA se voorafgaande projekte sal sodanig wees dat hierdie spanningsvlak nie oorskry sal word nie. Die doel van die navorsing omskryf in hierdie proefskrif is om die eienskappe van vonkontladings rondom kraglyne te evalueer. Dit word gedoen met behulp van metings en simulasies van uitstralings- en voortplantingspatrone wat met 'n spesifieke lyn geassosieer kan word. 'n Kunsmatige vonkontladingsopwekker word op 'n kraglyn geplaas en dien as bron om die uitstralingspatrone te meet. Metings is uitgevoer in verskillende omgewings, insluitende 'n hoogspanningslaboratorium (HV-Lab), 'n 40 m toetslyn en 'n 22 kV WS toetslyn van ongeveer 1.5 km lank. Die hoof vonkontladings eienskappe van belang is die temporale en spektrale eienskappe. Die tydgebiedeienskappe wat ondersoek is, is die pulsvorm asook die pulsherhalingskoers. Die laterale, longitudinale en hoogte-attenuasie profiele word ook gekwantifiseer. Aangesien stroompulse deur vonkontladings op die kraglyn geplaas of geinduseer word, sal die lyn as 'n ongewenste antenna optree. Die ver-veld uitstralingskenmerke van die lyn is ook geëvalueer deur gebruik te maak van fisiese skaalmodelstrukture en -simulasies. 1/120ste en 1/200ste geskaleerde lynmodelle, wat onderskeidelik 'n absorberende- en metaalgrondvlak bevat, was gebruik om 'n 3 spanlengte kraglyn te simuleer met behulp van FEKO. Metings van die fisiese skaalmodel strukture is in 'n anegoise kamer geneem. Beide die metings en die simulasies toon dat die lyn 'n endpunt uitstralingspatroon het. Lynlengte, die opwekkingsposisie van die stroompuls en die lynkonfigurasie is 'n paar van die parameters wat die uitstralingpatroon beïnvloed, soos in die navorsing aangedui. Die bevindinge van hierdie studie word gebruik om steurnisse as gevolg van vonkontladings op die kraglyn te identifiseer, op te spoor en uiteindelik reg te stel. Toepaslike toerusting word voorgestel wat gebruik kan word vir die identifisering en opsporing van vonkontladings.

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.