A light weight SAR has been designed, suitable for short range tactical UAVs, consisting of a fully digital receive array, and a very compact active transmit antenna. The weight of the complete RF front is expected to be below 3 kg, with a power consumption below 30 W. This X-band system can provide image resolution down to 10 cm at up to 5 km range. The system makes use of FMCW technology and digital beam forming in the horizontal direction, with 24 receive channels. A switchable transmit antenna is designed, to allow wide coverage with sufficient antenna gain. RF electronics for the receive panels have been realized and tested, as well as a low phase noise transmitter. Detailed antenna design has been performed, and critical issues such as bandwidth and transmit-receive isolation have been assessed by simulation.