Reflector antennas used for radio astronomy require feeds that use the reflector surface as
efficiently as possible while maintaining low noise levels. The specifications of new radio
astronomy telescopes under development such as MeerKAT and the square kilometre array
calls for feeds that have wide frequency bandwidths. The antennas traditionally used as
reflector feeds, corrugated horns, are incapable of achieving the required bandwidth. Thus
new feeds have to be developed that are capable of achieving high efficiencies and low
noise over a large frequency bandwidth.
A quad-ridge horn antenna is developed that is more suitable for use as a reflector feed
antenna. Quad-ridge horn antennas are dual-polarized and can obtain wide bandwidths. A
disadvantage of using a quad-ridge horn as a reflector feed is that the radiation pattern
changes as a function of frequency. The geometry of the quad-ridge horn antenna is
investigated to determine which features of the antenna can be used to control the radiation
pattern. The use of elliptically shaped sidewalls is proposed. Elliptically shaped sidewall
quad-ridge horn antennas are shown to have improved radiation patterns that are more
constant as a function of frequency compared to conventional quad-ridge horn antennas. A
prototype of such an antenna, with the design based on the results of the parametric study,
is presented. The antenna is well matched to the source and has excellent radiation patterns
over a wide bandwidth. Good agreement between measured and simulated results is
obtained.
Voer-antennas vir radio-astronomie reflektor-antennas moet die reflektor-oppervlak
optimaal benut en lae ruisvlakke handhaaf. Nuwe radio-astronomie teleskope wat tans
ontwikkel word, soos die MeerKAT en die SKA, benodig voer-antennas wat oor breë
bandwydtes funksioneer. Die voer-antenna wat tradisioneel gebruik word, die geriffelde
horing-antenne, kan nie oor sulke groot bandwydtes funksioneer nie. Breë bandwydte
voer-antennes wat die oppervlakte van die reflektor optimaal benut en lae ruisvlakke
handhaaf, moet dus ontwikkel word.
‘n Kwad-rif horing-antenne word ontwikkel wat meer geskik is as ‘n reflektor voerantenna.
Kwad-rif horing-antennas is dubbel-gepolariseer en kan oor groot bandwydtes
funksioneer. ‘n Nadeel van kwad-rif horing-antennas is dat die stralingspatroon as ‘n
funksie van frekwensie verander. Die geometrie van die antenna word parametries
ondersoek om vas te stel watter onderdele van die antenna gebruik kan word om die
stralingspatroon te beheer. Die gebruik van sywande wat ellipties gevorm is, word
voorgestel. Dit word gedemonstreer dat antennas met ellipties-gevormde sywande
stralingspatrone het wat minder varieer as ‘n funksie van frekwensie as konvensionele
kwad-rif horing antennas. ‘n Prototipe met ‘n ontwerp wat gegrond is op die resultate van
die parametriese studie, word voorgelê. Die prototipe is goed aangepas en het baie goeie
stralingspatrone oor ‘n breë bandwydte. Gesimuleerde en gemete resultate van die antenna
stem goed ooreen.
