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Abstract
The analytical and experimental investigations into the radiation characteristics of a high-gain antenna system are made. The antenna system consists of an H-plane sectoral horn with a layer of dielectric coating at the bottom E-plate (the top plate is removed) as a surface-wave source and a dielectric sphere placed off-set in front of the horn aperture. The radiation characteristics are derived by treating the antenna system as a microwave lens illuminated by an aperture source. There is good overall agreement between theoretical and experimental results of radiation pattern and gain measurements especially for dielectric spheres of diameters less than two wave lengths. It is observed that the on-axis gain of the surface-wave horn antenna is increased due to dielectric sphere loading. The system also possesses reduced 3-dB beamwidth. The proposed antenna system can be used either as a highly directive variable beamwidth feed for parabolic reflectors or as a convenient and effective high-gain source of radiation of UHF and microwave frequencies.