Ridge-Waveguide Stub Filters for Earth Observation Dual-Band Antenna-Feed Systems

This paper describes the ridge-waveguide stub filter configuration that was integrated in the Ku/Ka-band antenna-feed chain developed during the A/B1 phases of the Copernicus Imaging Microwave Radiometer (CIMR) programme. The filter geometry is based on the direct cascade of asymmetric stubs that are alternatively arranged along the opposite sides of the main ridge-waveguide. This arrangement results in maximization of the gaps between the metal surfaces. Hence, the layout presented allows for the rejection of all the relevant modes, while minimizing insertion loss that is a key figure-of-merit in radiometric applications. The filter was designed by the spectral element-method presented in [10].