Research On Airborne ISAR Imaging Of Ship Targets

Inverse Aperture Radar (ISAR) can image non-cooperative moving targets such as aircrafts, ships and celestial objects over a long distance under all weather and all day. It is of particular interest for strategic defense, anti-submarine warfare and radar astronomy. The airborne ISAR imaging of ship target depends on the ship's rotation relative to the radar line of sight (RLOS). This rotation has two sources: One originates from the relative movement between the radar and the ship. The other comes from the ship sway (roll, pitch and yaw). Moreover, the practical sea-state changes frequently and is unpredictable. All of these increase the difficulty in achieving high quality images. In this article, we have a deep study on the airborne ISAR imaging of ship targets.In the preface to this dissertation, the development of the ISAR is introduced briefly. Subsequently the range-Doppler principle and many kinds of methods for motion compensation are detailed. Finally, the main contents of this thesis are summarized.Chapter 2 exposits the principle of the airborne ISAR imaging of ship targets in detail using the concept of image projection plan and effective rotating vector. And some imaging results under every ship sway (roll, pitch and yaw) are presented.Radar imaging of ocean-going ships is difficult to get good images because of the complicated relative motion, so time-frequency analysis is performed for ship imaging with the ISAR real data in Chapter 3. The time-frequency curve of stern scatterer is analyzed. Furthermore, high quality images are obtained by identifying the regions which are uniform in frequency.Chapter 4 exposits the method of optimal time selection for ship ISAR imaging in detail. It is based on a proper decomposition of the ship motion in horizontal and vertical components. Proper imaging intervals in order to obtain high quality ship images are selected using the estimated rotating angular velocity and Doppler extension. Also, some results under certain simulation environments are presented.