Abstract
The spillover from a normal symmetrical Cassegrain aerial, particularly when the aerial is directed towards a. low elevation stationary satellite, is equally distributed towards the sky and the local hot Earth. In order to direct this radiation more toward the sky, both the subreflector and its feed horn have to be tilted in the appropriate direction. The consequences of this procedure are complex. The subreflector requires considerable redesign and the primary radiation pattern can therefore suffer serious degradation. The study has been aimed at optimizing the design and assessing the consequences in such a way as to achieve a considerable reduction in the Earth-directed spillover without undue decrease in gain or deterioration in secondary radiation performance. Theoretical analysis has been shown to be in good agreement with experimental patterns and computer programs have been produced which enable all systems of this type to be predictably analysed.