High Resolution Synthetic Aperture Radar

This manuscript first introduces the fundamentals of Synthetic Aperture radar (SAR), there including the principle of the high resolution imaging capability, the processing required to focus the images, with its constraints and the different acquisition modes. Thereafter, it shows the potential ways to increase the imaging capabilities based on the concept of distributed SAR. Specifically both multistatic and MIMO SAR are considered with both aims of increasing azimuth resolution and increasing the ground range swath. The formation of increased high resolution images by exploiting the distributed SAR concept is then described in details for a specific application: to increase the cross range resolution of ISAR images of rotating targets. This distributed ISAR technique is devised for two different cases: (i) MIMO case with each platform carrying an active radar, that transmits and receives RF waveforms, (ii) multistatic case with a single platform carrying an active radar (i.e. transmitting and receiving) and the remaining platforms equipped with passive sensors (i.e. receiving only). The processing chain required to focus the High Resolution distributed ISAR is shown, together with the results obtained against simulated ISAR data for both the MIMO and the multistatic cases. The performance analysis shows that the distributed approach is able to provide an increase of the cross range resolution up to the number of platforms in the multistatic case and even higher in the MIMO case, if the platforms are properly located. This is of great benefit in applications where the target rotation angle is insufficient to guarantee the desired resolution. A typical case is the imaging of ship targets with rotation induced by the sea swell structure under low sea state conditions.