Hybrid Analog-Digital SAR Instrument with Reflector antenna and Overlapped subarray feed for Earth Observation

As part of the ESA studies of new instrument for Earth Observation, the study of a SAR architecture based on overlapped array antennas was launched last year. The objective of the activity is to develop a test unit of a reflector based SAR antenna fed by an array organised in overlapped subarrays, supporting novel multichannel wide-swath SAR architectures and exploiting multiple beams in both azimuth and range/elevation directions. In the study, beamforming architectures based on analogue, digital and hybrid analogue/digital configurations have been investigated and traded-off, with the conclusion that the hybrid analogue/digital beamforming on reception and only analogue beamforming approach on transmission is an optimum system architecture since it balances system complexity and system performances. The antenna system consists of a large oversize reflector with a feedarray capable of generating multiple single beams on receive for digital processing. In the paper, a description of the hybrid SAR Instrument is presented, describing the main characteristics of the system, the Antenna and the feedarray options and main characteristics and performances, and the main SAR system performances expected from this system.