Analysis of a ground target deployment in an airborne passive SAR experiment

Air-to-ground surveillance requires using synthetic-aperture radar (SAR) technology for clutter reduction and for fulfilling resolution requirements. By using ultra-wideband VHF- and UHF-band SAR, detection of targets concealed by forests is enhanced, compared to using SAR operating at higher frequency bands. The need for fine resolution and hence large bandwidth, however, limits the use of the former technology due to lack of allocated frequency bands. Passive SAR using illuminators of opportunity is not limited in this respect and is an alternative concept to be evaluated. An experiment was performed in June 2016 in order to assess the potential of using passive UHF-band SAR. The airborne system LORA was used in a configuration with six 10-MHz receive channels, specifically with three antenna channels covering two 8-MHz digital TV (DVB-T) frequency bands centered on 530 and 594 MHz, respectively. The trial included two different target deployments on two different days for repeat pass analysis. Resulting passive SAR images shown are from the first day of deployment and based on one TV channel with three antenna elements providing beamforming. From these images, the target response of 13 objects consisting of corner reflectors and vehicles were evaluated.