Quad-ridge horn antenna with elliptically shaped sidewalls for use as a reflector feed for radio astronomy

Abstract

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.