To develop and test a reflector based SAR antenna fed by an array organised in overlapped subarrays, with reduced complexity and cost with respect to active planar array SAR antennas.

Several SAR future Earth Observation missions requires large reflector antennas generating highly directive overlapped beams. This has been done so far with high power waveguide Beam Forming Networks including ferrite switches as implemented for Core H2O pre-developments. In this activity, it is proposed to investigate reflector antennas fed by overlapped subarrays. This represents an extremely promising concept for on-board SAR instruments. In fact, arrays based on overlapped subarrays permit generating highly directive beams enabling low spill over losses with the possibility of creating contiguous overlapped beams with a required cross-over level of typically 1 dB. A possible solution, recently developed for ESA Telecom applications, consists in overlapping contiguous feeds in a radiative way, i.e. without any bulky waveguide Beam Forming Network. This overlapping can be achieved by using EBG materials or Fabry-Perot resonators placed in front of the feeding array; other configurations recently proposed may be considered as well. In the case of Earth Observation missions, this overlapping may be significantly easier to achieve because contiguous beams should be activated sequentially in time with an associated simplification of the focal array architecture (especially in the filters needed to decouple contiguous feeds). Special attention shall be paid on the power handling needs. A first advantage of this new technology reflector, especially when the operational frequency is high, may be obtained replacing active phased arrays antennas with a reflector based antenna. A second advantage will be guaranteed feeding the reflector with an array organized in overlapped subarrays with the overlap done in a radiative way or in a guided way. The activity will be organized in 2 parts: 1) design, analysis and optimization of the feeding array architecture; 2) proof of concept. A breadboard will be designed and manufactured in order to demonstrate the capabilities of the new antenna architecture. The design of the feeding array will allow to extrapolate the performance of the entire antenna including the reflector.