RADIATION CHARACTERISTICS OF A HORN ANTENNA

Abstract

The widespread application of paraboloidal reflector antennas in microwave communication, radar and radio astro nomy has stimulated considerable interest in the develop ment of physically small improved feed systems which will have high directivity, low side lobes and a multiple beam facility. This work comprises of a detailed theoretical and experimental investigations into the radiation characteris tics of some improved primary feeds, with greater directivity, increased on-axis gain and low side lobes, for reflector antennas. The development of this new feed system are based on design of new type of horn antenna using the properties of unsymmetrical radial surface wave. A new type of radiating structure using the properties of unsymmetrical radial surface wave suggested by Arora [10] has been designed and electric and magnetic field components were derived using electric Hertzian vector potential. The field lines were also drawn inside the horn using the derived field equations. The radiation characteristics of the newly designed structure were also studied in the forward direction as well as in space. Results obtained show that the system will have pattern with greater directivity and low side lobes as compared to conventional type of horn antenna of the same dimensions. The effort were also made to design an optimum horn antenna to give a maxi mum on -axis gain. The effect of placing dielectric sphere in the vicinity of radiating surface wave horn aperture has been investigated. Sphere loading is seen to narrow the -3db beamwidth. The sphere loaded system also posses greater on -axis gain, low side lobes and a variable beam feed system. Finally some suggestions are made for further work in this field.