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Passive SAR data have been registered using the airborne low frequency SAR system LORA. For this purpose, the radar sensor was reconfigured to not transmit any signals but only gather data along the pre-defined synthetic aperture. The receiver unit was tuned to fully accommodate the DVB-T signal centred at 634 MHz (channel #41), acting as the illuminator of opportunity within the ground scene mapped...
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...
Bistatic and passive radar are emerging technologies for covert ground surveillance based on cooperative or non-cooperative transmitters, respectively. The latter uses transmitters of opportunity, e.g. terrestrial digital video broadcasting (DVB-T). In the paper, we show results from two unique experiments conducted using airborne systems operating in the VHF and UHF bands. The first experiment investigates...
The paper presents results from developing and testing a bistatic SAR system for ground surveillance in the VHF band (25–83 MHz). It is based on two radars developed by FOI: The monostatic LORA system installed in an aircraft and the bistatic and passive CARINA system installed on a helicopter. CARINA is based on direct RF sampling of two receiver channels (2 × 14 bits @ 250 MSPS) together with continuous...
Airborne bistatic SAR data have been collected at VHF- and UHF-band to investigate clutter suppression in forested and urban areas. The synchronization between the SAR systems is accomplished using the 1-PPS signal provided by the GPS system. The same signal is also used as input to a disciplined 10 MHz master oscillator integrated in both radar systems to maintain sufficient phase stability. Images...
The paper describes work done by FOI to develop cost-effective methods for the detection and classification of small surface vessels at sea or in littoral waters. We report on the architecture, current realization, and initial tests of a prototype system consisting of a coherent pulse-Doppler radar operating at S-band and an optical sensor module consisting of a gated active laser imaging sensor for...
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