mm-Wave SAR demonstrator as a test bed for advanced solutions in microwave imaging

The capability of imaging and surveying ground areas with airborne and spaceborne sensors has a very high priority in many applications, both in the civilian and military sectors. One of the most essential uses of this capability is in disaster monitoring, where up-to-date, reliable images and data are vital for the undertaking and coordinating of rescue actions. Sensors in space are very accurate but typically have a long revisit time, and thus their use for continuous monitoring is limited. Manned aircrafts equipped with optical, infrared, and synthetic aperture radar (SAR) are costly, and their operation in poor weather conditions (like heavy storms) are limited due to concerns over pilot safety. Unmanned aerial vehicles (UAV) are ideal candidates for the safe and cheap surveillance and imaging of such areas. They can provide continuous monitoring at very low cost, be deployed very quickly, and pose no risk of the loss of life in the case of a platform malfunction caused by heavy weather conditions, technical problems, or human error. The disadvantage of small, unmanned platforms is that they only offer limited space for payloads and have a low electrical power supply. This lays down the conditions for the design of an airborne sensor for small- and medium-sized UAVs. The cheapest solution for UAV surveillance is the use of visual light cameras. Optical cameras are cheap, light, and require a low supply of power, but their usage is limited to the daytime and good weather conditions. The presence of heavy rain, clouds, fog, or smoke can significantly reduce their imaging distance, sometimes down to just a few meters. Far better results can be obtained using much longer electromagnetic waves. The use of far infrared (e.g. in the 10 μm region) can provide thermal information and can be used for the detection of people in both day and night conditions, but it does not provide satisfactory images of land and infrastructures. The use of millimeter and centimeter microwaves with active illumination, combined with SAR technology, can provide high resolution images in all weather conditions, day and night, at a distance of several kilometers.