Evanescent-Mode Ridge-Waveguide Radiating Filters for Space Applications

This paper describes a new family of all-metallic radiators based on below-cutoff apertures fed by evanescent-mode ridge-waveguide filters. The passband of the filters and the polarization of the apertures are configured to radiate orthogonal signals at a different center frequencies. The simultaneous operation of these radiators in an array configuration results in interleaved apertures producing overlapped fields. This strategy reduces the volume and weight of the antenna system, which is an especially appealing characteristic in satellite antennas. Each isolated evanescent-mode filter ends in a small-size aperture and is designed following a novel synthesis procedure. Next, the radiating elements are combined, and the resulting array is analyzed as a multiplexer from the input ports to the free-space region, thus accounting for all mutual couplings between different apertures. To validate the theoretical formulations, a prototype has also been manufactured. The results obtained show very good agreement between simulation and measurements in terms of reflection coefficient, sidelobe level, and realized gain, thereby fully validating the new family of radiating arrays.