Thesis (MScEng)-- Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis presents a thorough study of the printed sinuous antenna and its characterisation as a feed for re ector antenna applications. Two di erent techniques are used in this study, namely a parametric study and an e cient surrogate based optimisation strategy. A planar sinuous antenna over a re ecting ground plane, with no absorber lining, is designed following a parameter study from which e ective design guidelines are derived. The designed prototype displays a bandwidth ratio of more than 3 : 1 from 1:9􀀀6:2 GHz, at a measured return loss of 10 dB, representing a signi cant improvement over the octave band previously achieved with a similar antenna. An optimisation based approach is followed in formally investigating a conical sinuous antenna over a re ecting ground plane. An e cient surrogate based optimisation strategy, in which the antenna's response is approximated by a Kriging model, is used. The search for optimal design parameters as well as improvements in the accuracy of the Kriging model is accomplished by using expected improvement as the in ll sampling criterion. The antenna is optimised for return loss, aperture e ciency for a prime-focus paraboloid re ector as well as cross-polarisation and results from the optimisation are used to derive e ective design guidelines and performance limitations. The investigations are conducted for the 2 􀀀 6 GHz band and the obtained results can be easily applied for designs with wider bandwidths. Simulation results reveal improved return loss, aperture e ciency and cross-polarisation performances compared to what has previously been reported for this antenna. / AFRIKAANSE OPSOMMING: Hierdie tesis bied 'n deeglike studie van die gedrukte stroombaanbord sinuous antenna, sowel as die karakterisering daarvan as voer vir re ektor antenna toepassings. Twee verskillende tegnieke word gebruik, naamlik 'n parametriese studie en 'n surrogaat-gebaseerde optimering strategie. E ektiewe doeleindes vir die ontwerp is van 'n parameter studie afgelei, waarvolgends 'n planêre sinuous antenna met 'n weerkaatsingsgrondvlak ontwerp is sonder enige absorberende materiale. Die prototipe vertoon beter as 'n 3 : 1 bandwydte van 1:9 GHz tot 6:2 GHz teen 'n gemete weerkaatsingskoë siënt van beter as 􀀀10 dB, wat dui op 'n aansienlike verbetering teenoor die oktaaf bandwydte wat voorheen met 'n soorgelyke antenna bereik is. 'n Optimering-gebaseerde benadering is gebruik om ondersoek in te stel in die gebruik van 'n koniese sinuous antenna met 'n weerkaatsingsgrondvlak. 'n Doeltre ende surrogaat-gebaseerde optimeering strategie is gebruik, waar die antenna se weergawe deur 'n Kriging model benader word. Die verwagte verbetering is gebruik as maatstaf in die soektog vir optimale ontwerpsparameters, sowel as om die akkuraatheid van die Kriging model te verbeter. Die antenna is geoptimeer vir sy weerkaatsingskoë siënt, stralingsvlak e ektiwiteit for 'n paraboloïed antenna sowel as kruispolarisasie. Resultate van die optimering is gebruik om e ektiewe riglyne vir die ontwerp en grense vir die werkverrigting op te stel. Die antenna is ondersoek vir die 2 tot 6 GHz frekwensieband en die resultate wat verkry is kan maklik op ontwerpe met selfs wyer bandwydtes toegepas word. Simulasie resultate dui op 'n verbetering in weerkaatsingskoë siënt, stralingsvlak e ektiwiteit en kruispolarisasie in vergelyking met wat berig is vir hierdie antenna.