Frequency selective surface beamsplitter for sub-mm wave polarimetric space science instruments

In this paper we report on the design, fabrication and measurement of a frequency selective surface (FSS) which generates virtually identical spectral responses in 3% wide channels when the filter is operated in the TE and TM polarisation at 45deg incidence. The structure is formed from two closely spaced freestanding arrays with unit cells containing nested short circuited rectangular loop and dipole slot elements. The FSS provides 30 dB isolation between the frequency bands 316.5 - 325.5 GHz and 349.5 - 358.5 GHz and 0.6 dB insertion loss. Simulated and measured transmission coefficients are in close agreement.