Design of a 229 GHz Freestanding Double Layer FSS for Quasi-Optical Networks

This paper presents a 229 GHz freestanding double layer Frequency Selective Surface (FSS) for quasi-optical feed systems in space missions, which has the ability to separate the frequency bands of 226~232 GHz (4.8% bandwidth) and 23~185 GHz with insertion loss in pass band less than 0.24 dB and return loss in stop band over 30 dB. It should be noted that the FSS is working in TE polarization at 45 degree incidence. The FSS topology consists of two air spaced freestanding metallic screens, and the unit cell is a shorted hexagonal ring slot which is designed to resonate at 229 GHz band. Moreover, the two simulated results of shorted circular ring slot unit and shorted hexagonal ring slot unit has been compared, which shows the shorted hexagonal ring slot unit is a recommended unit shape for performance.