Efficient approach to analyze the dual-reflector antenna system with defocused feeds

A time-saving reflection point locating technique based on the geometrical optics approximation is proposed. The technique provides an efficient evaluation of a Cassegrain or Gregorian antenna system. For comparison, all the reflection points are calculated with the proposed technique and W.V. Rusch's approach (1979). Patterns calculated by these two techniques show very similar results. However, the computation time of the proposed technique is only one-fourteenth that of Rusch's approach. It is concluded that, for a slightly defocused feed system, the proposed approximation technique works well for a dual reflector antenna system. It can be extended to a monopulse tracking antenna system with multiple feeds.<>