Advances in Frequency Selective Surface Filter Technology for Earth Observation Radiometers

n the past decade Earth observation instrument technology has largely been driven by the need to provide spectroscopic characterisation of the Earth’s atmosphere for studies which will provide new insights into phenomena including atmospheric composition, ozone depletion and climate change. What these missions have in common is that they require state-of-the-art hardware to achieve the high receiver sensitivity necessary to detect weak molecular emissions at microwave to sub mm wavelengths. To satisfy satellite payload constraints on cost, mass and energy consumption, passive remote sensing radiometers traditionally employ a single mechanically scanned aperture antenna to collect radiation over a wide frequency range. The signals are spatially and spectrally separated within the quasi-optical heterodyne receiver by Frequency Selective Surface (FSS) which are normally orientated at 45 to the direction of the wave propagation. The key technology challenge is to ensure that the FSS beamsplitters simultaneously exhibit very low signal band insertion loss and meet the conflicting requirement for high isolation between adjacent frequency bands. The purpose of this talk is to give an overview of a multidisciplinary research project at Queen’s University Belfast which has exploited state of the art micromachining technology to create space qualified printed periodic arrays and substrateless FSS which are designed to provide an insertion loss <0.25 dB in multiple channels over the frequency range 23GHz to 700 GHz. Simulation and experimental results will be compared and the construction details for each of the two classes of FSS will be presented.