An efficient hybrid UTD-CSB-VWF approach for the analysis of large reflector antennas

A relatively efficient and accurate hybrid analysis for predicting the radiation patterns of large reflector antennas illuminated by realistic feeds is developed in this paper. The problem is decomposed into three main parts. First, the measured radiation pattern of the feed with the reflector absent is represented in terms of a spherical vector wave function expansion. The latter expansion directly provides the equivalent sources on the smallest mathematical spherical surface that encapsulates the feed; these equivalent sources generate the same fields external to the encapsulated sphere (with the feed absent) as those produced by the original feed. Secondly, an analytic continuation of the encapsulating sphere into complex coordinate space allows the fields generated by the equivalent sources on the complex sphere to be represented by a discrete sum of complex source beams which then illuminate the reflector. Finally it is possible to use an analytic continuation of the uniform geometrical theory of diffraction for calculating the reflection and diffraction of each complex source beam by the reflector surface and its edge, respectively, after the latter are continued into complex space. Most importantly, the reflection and diffraction of only a few complex source beams contribute to the reflector radiation pattern in any given direction thereby making the method highly efficient as well as more accurate when compared to the conventional numerical physical optics integration over the large reflector surface. Examples will be presented to illustrate the concept of this hybrid approach.