Dottorato in TECNOLOGIE DELL'INFORMAZIONE E DELLE COMUNICAZIONI (ICT)

Titolo della tesi: MULTIDIMENSIONAL PASSIVE ISAR FOR MARITIME TARGET IMAGING

In the last years a huge progress on passive radar techniques has been experienced. A challenging topic is to improve the passive imaging capability with the final goal to enable in the near future passive target identification and classification. Such research field has been till now limited from the achievable range resolution, depending on the bandwidths of the signal transmitted from a non-cooperative illuminator. To overcome such limitation, in this work multidimensional Inverse Synthetic Aperture Radar (ISAR) approaches are introduced. The multidimensionality is provided in terms of angle of view, operating frequency and polarization. In particular, among available Illuminators of Opportunity, this study focuses on terrestrial and satellite digital video broadcasting (DVB-T and DVB-S) signals. DVB-T operates at UHF/VHF-band exploiting terrestrial illuminators and represents, at present days, the most used IO for passive radar systems. DVB-S signals operate at Ku-band by means of geostationary satellite illuminators and few contributions about its exploitation for passive imaging are available in the literature. Moreover, the introduction of multipolar data to enhance the ISAR image quality can be considered as a challenging research in the passive bistatic imaging field. During this work, theoretical approaches suitable for both DVB-T and DVB-S signals, in case of one polarization data as well as multipolar data, have been developed. To validate such methods, experimental data were collected within two different measurement campaigns. The results achieved during this research show the feasibility of passive ISAR imaging based on DVB-S transmissions, which can be improved considering different time acquisitions. Furthermore, ISAR images obtained exploiting simultaneusly DVB-T and DVB-S over a cooperative maritime target have been first compared and then combined in order to improve the target size estimation. Finally, the different approaches introduced in the polarimetric domain permit, from one hand, to separate scattering mechanisms belonging to distinct parts of the imaged target, and, from the other hand, to enable the formation of ISAR products with enhanced quality. The results achieved within this Thesis contribute to the research in the passive target imaging field and sow the seeds for further investigations.