Application of passive millimeter-wave imaging and UHF-based synthetic aperture radar for threat detection

Kurzfassung

Passive millimeter-wave remote sensing for enhanced vision: For many military or peace-keeping operations it is necessary to provide better situational awareness to the commander of a vehicle with respect to possible threats in his local environment (predominantly ahead), at a distance of a few ten to a few hundred meters. As a beneficial part of a suitable multi-sensor system, an imaging radiometer with a sufficiently high frame rate and field of view is considered and will be presented in the briefing. The radiometer, working 24 hours in all weather and sight conditions, generates quasi-optical images simplifying the microwave image interpretation. Furthermore it offers the advantage to detect and localise objects and persons under nearly all atmospheric obstacles and also extents the surveillance capabilities behind non-metallic materials like clothing or thin walls and thin vegetation. Based on constraints of low costs and the observation of a large field of view, the radiometer still offers a moderate resolution at a moderate scan speed. Active microwave remote sensing for buried object detection: Many countries face the problem of landmines and unexploded ordnance contaminated land sections which present a significant risk to the civilian population. The detection and subsequent clearance of these explosive hazardous substances is therefore extremely important and necessary. Within the framework of an EU project called TIRAMISU (Toolbox Implementation for Removal of Anti-personnel Mines, Sub-munitions and UXO) a ground-based, near field broadband multi-element radar system (called TIRAMI-SAR) using the synthetic aperture method is being developed. TIRAMI-SAR is based on the SAR principle for the medium range detection of mines at several meters average distance. The truck based radar system operates under a side-looking geometry in the range direction (i.e. cross-track direction) with the method of pulse compression. Using an operational bandwidth of round about 2.7 GHz, a spatial range resolution of 5-10 cm can be achieved. In the along-track direction (i.e. in motion or azimuth direction), the method of synthetic aperture radar (SAR) leads to a similarly high spatial resolution (azimuth resolution). The selected UHF range represents a good compromise between the penetration depth of the electromagnetic waves and the practical size of usable, broadband antennas. With this setup it is possible to scan an area of approx. 50 m² (e.g. 5 m across track, > 10 m along track) in round about 3 minutes. Using nearly arbitrary geometries for the mono-static and bi-static antenna arrangement in combination with polarimetry information for improved detection and localization, it is possible to produce multiple two-dimensional (2D) SAR images and by incoherent or coherent superposition a type of three-dimensional (3D) SAR images as well.