Realisation of a compact forward looking SAR with digital beamforming on receive only

This paper presents a new system design for an airborne forward looking SAR with digital beamforming on receive only. The transmitter illuminates the swath with one single horn antenna, The receiver is configured as an array of 56 sequentially switched 2 x 2 aperture coupled patch subarrays. Each su barray points at the same, illuminated, swath. The sequentially switching i s adjusted to sample the Doppler frequencies of ail 56 receive channels. Th e switches and preamplifiers are integrated in the antenna modules. The ope rating frequency is 9,6 GHz. The 2 x 2 subarrays are assembled in 7 modules , The total length of the antenna is 3 m and the diameter is 12.5 cm. The s ystem was built under contract from the DLR, Oberpfaffenhofen, Germany and it is operated on a helicopter for Verification measurements.