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The design, manufacture and performance of a frequency selective surface (FSS) which is required to operate simultaneously in the TE and TM planes at 458 incidence over the frequency range 173671 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.
Introduction: The work described in this Letter addresses the need to develop low-loss FSS filter technology for signal separation in the multi-spectral microwave imager instrument (MWI) which will be employed in the Post EUMETSAT polar satellite system [1]. Primary products to be derived from the MWI mission include cloud liquid water and ice observations, and cirrus size components which are important to climate. The FSS will be employed to demultiplex the scene radiation into separate spatial and spectral channels prior to downconversion and detection. Fig. 1 depicts one proposed layout of the quasi-optical feed train for the five highest frequency channels. The purpose of this Letter is to describe the design, manufacture and electromagnetic performance of the most critical FSS which is required to separate the 664 GHz channel from the four lower frequency bands with a maximum loss of 0.5 dB when the filter operates in both the TE and TM planes and is oriented at 458 incidence in the radiometer feed train. Previously the authors reported the performance of dual polarised lowpass FSS [2, 3] which were designed to operate in the frequency range 316.5 - 358.5 GHz. The structures were constructed using two closely spaced freestanding nested C-shaped slot arrays and provided insertion loss and channel isolation of 0.9 dB/20 dB [2] and 0.5 dB/30 dB [3]. The performance criteria of the filter described in this Letter is significantly different because the MWI FSS is required to operate in highpass mode, generate spectral transmittances at...