A dual band array-fed reflector ScanSAR antenna

The paper presents the array-fed reflector antenna of the CoReH2O (Cold Regions Hydrology High-resolution Observatory) SAR instrument currently being investigated within Phase-A under ESA contract. The antenna is a dual linearly polarized single-offset reflector, illuminated by two side linear arrays operating in X and Ku band respectively. Each array comprises seven compact multimodal horns in quasi rectangular waveguide. These are sequentially excited, a couple at a time, for optimum antenna pattern synthesis and secondary beams overlap. Each horn is a multiple step rectangular waveguide structure that provides the right modal content at aperture, very close to the analytical patterns synthesized through benchmarks. The Ku band feed has been subjected to a pre-development activity aimed at validating the design. The measured results at feed level show good agreement with predictions. Measured pattern has been used as primary source in the antenna model and satisfactory performance have been predicted on radiated beams. The X band feed has been designed with the same electromagnetic model adopted for Ku band and all performances are predicted with the same accuracy. Further breadboarding activities are foreseen in X band, finalized to characterize a reduced dual band feed cluster and the relevant switching systems, taking into account the effect of mutual coupling between the two frequency bands.