Fraunhofer Institute for High Frequency Physics and Radar Techniques FHRIn the deployment of airborne radar systems, a central objective is to obtain results of the highest possible precision in the detection and classification of objects on the ground. Research conducted at Fraunhofer FHR has demonstrated that multidimensional radar imaging can provide valuable additional information about a scene. The institute addresses this topic on behalf of the German Armed Forces and actively contributes to relevant NATO research groups.
In crisis situations, reliable airborne reconnaissance of ground conditions is indispensable. The use of synthetic aperture radar (SAR) systems in combination with high‑resolution imaging radar techniques already delivers highly useful results today. However, for users in the armed forces, security agencies, and industry, key questions remain: How can reconnaissance performance be improved? How can images be made more precise, and how can more information about objects such as military vehicles and buildings be extracted?
In this context, researchers at Fraunhofer FHR investigated the added value that imaging radar techniques can provide for object classification when airborne data are collected from multiple viewing directions and when multiple frequencies (Ka‑band and W‑band) and multiple polarizations are employed. The theories and algorithms developed for this purpose were validated in an international measurement campaign in which Fraunhofer FHR participated with the systems MIRANDA‑94 and Pamir‑Ka. The measurements were conducted at a military test range of the Royal Air Force in the United Kingdom, enabling a realistic assessment of the methods under operationally relevant conditions.
Positive Effects of Multiple Viewing Angles, Frequencies, and Polarizations
The results are highly promising: the collected data clearly show that the use of multidimensional radar leads to significant benefits for target detection and recognition. Different viewing angles, frequency changes at identical aspect angles, and varying polarizations each provide additional information that can be decisive for identifying objects, such as distinguishing between specific vehicle or tank types.
Scientific Excellence and International Recognition
The work carried out at Fraunhofer FHR has resulted in numerous publications, including a 300‑page technical report and two books to which the institute made substantial contributions. NATO also recognized the outstanding achievements of the researchers in the NATO Research Task Group SET‑250 by awarding the NATO STO Excellence Award.
Transfer to Future Sensor Systems and Applications
Building on the insights gained, current research investigates the advantages of multidimensional radar imaging using compact sensors mounted on drones. As part of its involvement in the NATO research group SET‑317, Fraunhofer FHR participated in another international measurement campaign in Switzerland, where multidimensional SAR data were collected using various drones. Fraunhofer FHR conducted measurements with its own system, and the resulting data are currently being evaluated at the institute. Initial findings confirm the high potential of these approaches for future operational systems.