Design of a Modulated FSS Subreflector for a Dual-Reflector System

This paper describes the design of a modulated FSS subreflector for a S/Ka-band Cassegrain dual-reflector system. The FSS subreflector separates the radiation from the S-band (2.0-2.3 GHz) and Ka-band (25.5-2.7.5 GHz). To simplify the manufacturing of the subreflector, a conical FSS subreflector is considered. Instead of using a periodic FSS where all array elements are identical, a modulated FSS subreflector with varying sized array elements is considered. The FSS elements are optimized to emulate an axial displaced hyperboloid surface, thereby compensating for the non-optimal conical subreflector surface. In Ka-band, the optimized modulated FSS subreflector improves the peak gain of the antenna system with more 6 dBs compared to the use of a periodic FSS.