A numerically-efficient scheme for computing the scattering from supporting struts and radome beams of a cassegrainian reflector antenna system

A metal space frame radome is essential in achieving pointing accuracy consonant with angular resolution, minimizing dish distortion by environmental effects and, hence, reducing demands on adaptive optics systems in large millimeter wave telescopes. Both design and evaluation of the radome then require extremely accurate assessment of noise temperature effects by radome scattering. The analysis reported herein is prerequisite to such a calculation. In this paper, we present a numerically efficient and accurate scheme for the computation of radome and feed support scattering in electrically large antenna systems. The first step in our approach consists of breaking up the surface of the scatterer into flat patches whose dimensions are on the order of 10/spl lambda/ /spl times/ 10/spl lambda/. Next, we find a complex exponential representation, involving only a few terms, for the tangential component of the incident H field on the patch by using a curve-fitting technique based on the pencil-of-function method. Finally, we take advantage of the exponential nature of the current representation and express the far field contribution of the patch to the pattern in a closed form.