Design of tri-band FSS used as subreflector in Ku and Ka bands

In this letter, a novel tri-band frequency selective surface (FSS) is designed to be used as the subreflector for reflector antennas. The FSS mainly consists of two layers of a square loop reflecting the linear polarization electromagnetic waves in Ku band (12.3 GHz -15.2 GHz) and a hexagon around with a hexagonal ring transmitting the circular polarization electromagnetic waves in Ka bands (18 GHz - 21.5 GHz and 29.3 GHz -32 GHz). A stable response is achieved for both TE and TM polarizations as well as oblique incidence angles, thus ensuring the reflector antennas utilize two feeds simultaneously. Then an array of FSSs with radius of 78 mm is designed and simulated together with the Ku and Ka feeds respectively. The simulated radiation patterns show that the FSS array makes only slight influence on the Ka feed and simulated results of the FSS array together with the Ku feed accord with that of the PEC patch with Ku feed. It is concluded that the FSS array is transparent in Ka bands and reflective as a PEC patch in Ku band.