664 GHz dual polarisation frequency selective surface

The design, manufacture and performance of a frequency selective surface (FSS) which is required to operate simultaneously in the TE and TM planes at 45° incidence over the frequency range 173–671 GHz is presented. The FSS was designed to allow transmission of radiation over a 2% bandwidth centred at 664 GHz and reflect four channels centred at 448, 325, 243 and 183 GHz with a loss < 0.5 dB. The filter was formed from silicon on insulator material which was precision micromachined with an array of Jerusalem cross-slots and encapsulated with high conductivity silver. Experimental results yielded virtually identical spectral responses in the two polarisation planes with the electromagnetic performance exceeding the above specifications.