Recent advances in submillimetre wave FSS technology for passive remote sensing instruments

In this paper we report on the design, manufacture and measured performance of two Frequency Selective Surfaces (FSS) which generate high pass filter responses with 3.6% and 2% wide transmission channels centred at 448 GHz and 664 GHz respectively. The FSS exhibit transmission losses lower than 0.5 dB in the TM plane (448 GHz) and simultaneously for TE and TM polarisations (664 GHz) when operated at 45º incidence. Reflection band losses are less than 1 dB for minimum edge of channel frequency separation ratios of 1.3:1 and 1.44:1. Both structures were constructed from silicon on insulator (SOI) wafers using precision micromachining and plating processes including the use of deep reactive ion etching to pattern the individual slots and remove the substrate under the periodic arrays. Quasi-optical transmission measurements in the 113–700 GHz range yield spectral transmission coefficients which are in close agreement with the numerical predictions.