Micro Doppler Signatures Extraction from Rotating Marine Radar Antennas on Ships in VHR SAR Images

The work focuses on the characterisation of marine navigation radars on ships from space-borne very high resolution (VHR) SAR images. The rotations of the antennas produce additional Doppler modulation in the SAR ship images, referred to as micro-Doppler effect. By properly detecting and extracting such features, relevant information such as the ON/OFF state of the radar antenna, its size and rotation speed could be made available, thus providing an additional support tool for ship behaviour/recognition. To this purpose, a processing chain has been here proposed that: i) autofocuses the ship images (usually defocused in SAR images due to their own velocity), ii) identifies the range cells containing mD features and iii) applies time-frequency analysis to extract marine radar characteristics. Results achieved against VHR SAR data are provided, demonstrating the capability of the proposed approach to detect and characterize rotating marine radar antennas in real scenarios.