Signatures of small drones and birds as emerging targets

This chapter concerns the basis for differentiating between birds and micro-UAVs using micro -Doppler signatures. The chapter starts with a small introduction to the different classes and configurations of UAVs. Further on, a review of the research field, covering RCS investigations, material choice and classification methods is given. Birds and UAVs as radar targets are discussed, and their electromagnetic properties, size and shape are investigated using finite difference time domain (FDTD) predictions. A particular focus is put on moving parts like rotors, propellers and bird wings. These predictions are followed by radar measurements that largely confirm the predictions, and a discussion on how to exploit the target properties for the classification is given. Radar system parameters required to differentiate between birds and UAVs using micro -Doppler are then discussed. Towards the end of the chapter, classification methods are discussed in brief before the chapter is concluded.