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

This thesis mainly focuses on the applications of Inverse Synthetic Aperture Radar (ISAR) processing for high resolution imaging of non-cooperative moving targets observed by a Bistatic Multichannel SAR system. Synthetic Aperture Radar (SAR) is a coherent imaging technique, formulated at the beginning of the 1950s, able to obtain fine resolution images of natural and man-made objects from a long stand off ranges with reduced revisiting time either in all-weather/all-day conditions. Due to these proprieties, SAR systems have been widely used for the environmental monitoring and homeland security applications in the last few decades, making the non-cooperative moving target imaging capability of the system an essential feature. In order to obtain a coherent processing of the echoes received from the scene and to form the synthetic aperture, the illuminated area must be considered static during the observation time. This represents a fundamental drawback since conventional SAR processing is unable to obtain a well-focused image of non-cooperative moving targets which may be possibly present within the observed area. Target defocus is due to the residual motion of the moving target with respect to the static focusing point in the scene. ISAR processing does not base its functioning on the static scene assumption but conversely exploits target own motions for the synthetic aperture formation in order to obtain high cross-range resolution images. Bistatic ISAR system has recently gained attention for its capabilities to overcome some geometrical limitations of monostatic ISAR system and for the developments of some possible applications such as multistatic and passive ISAR imaging. A solution that jointly combine SAR and ISAR processing in order to obtain well focused images of non-cooperative targets in bistatic scenario is analyzed in this thesis. In order to apply ISAR processing to SAR image, targets must be detected first. This step does not represent a particular issue in maritime applications since sea clutter return is lower compared to the target return but, conversely, it can be a critical issue in the case of ground targets embedded in a strong ground clutter that can also be heterogeneous in some real scenarios