Optimal Space Time Adaptive Processing for Multichannel Inverse Synthetic Aperture Radar Imaging

The thesis deals with the application of ISAR processing to obtain high resolution imaging of non-cooperative moving targets within a SAR scene. The research topic is of great interest nowadays. Modern SAR system can provide high resolution radar images of wide areas with reduced revisiting time. These features make them particularly suited for surveillance application. It is obvious that for these kind of applications the capability of imaging non-cooperative moving targets becomes fundamental. Since conventional SAR processing is unable to focus moving targets because of the lack of knowledge of the target motion a solution based on ISAR processing is proposed. In fact, ISAR systems, do not make any assumption about the target motion, but they exploit it to form the synthetic aperture and to obtain high resolution in the cross-range dimension. Since the ISAR processing must be applied to each target separately a detection step is fundamental. Although this detection step is not a problem when dealing with maritime targets, as the sea clutter return is usually much lower than the target return, it can a be a challenge when dealing with ground target. Multichannel information provided by SAR systems with multiple receivers can be exploited to mitigate the return of the static scene. STAP processing is then combined with ISAR technique to produce high resolution images of non-cooperative moving targets after detection within SAR images. The multichannel version of Range Doppler image formation algorithm is derived and analyzed. Then, it is used to define a Space Doppler Adaptive processing to mitigate the strong clutter before the application of ISAR autofocus. Performance are evaluated on simulated data. Results on real data prove the effectiveness of the proposed processing and its applicability on actual systems.