Diffraction analysis of frequency selective reflector antennas

A unified computational technique which allows the incorporation of the curved frequency selective surface (FSS) geometry in the computation of a dual-reflector-antenna radiation pattern is presented. The scattered fields from a illuminated FSS reflector are formalized using Huygens´ principle in such a way that the `reflecting´ and the `transparent´ FSS subreflector cases are treated identically and the thickness of the FSS subreflector remains arbitrary. The analysis utilizes local surface coordinates to describe the reflection/transmission matrices of the FSS subreflector, assuming that these matrices are available. In most cases the local tangent plane may be used to approximate the plane of the FSS in the local coordinate surface of the reflector. The way in which the local curved coordinate system can be introduced in the diffraction modeling of FSS reflectors and its importance in accurately predicting the sidelobe and cross-polarization levels are demonstrated. Results of numerical simulations are presented for several FSS subreflector configurations