Maneuvering Targets Inverse Synthetic Aperture Radar Imaging Study

ISAR transmits wide bandwidth signals to obtain high range resolution. The cross-range resolution is obtained by the Doppler frequency information of the target's rotation. It has the ability to acquire the imaging of the targets over a long distance under all weather conditions. In fact, ISAR imaging is an important breakthrough in the fields of modern radar technique. It is very important to not only military but also civilian use.ISAR imaging algorithm and ISAR system simulation are studied based on the establishment of radar echo model.1. Stepped-frequency signals are used in echo simulation. It could generate synthetic high resolution image. We studied the characteristic of the signals and processing methods. Spatially variant apodization algorithm is introduced to significantly reduce sidelobe levels without degrading mainlobe resolution. The dissertation demonstrates the maneuvering target imaging model with acceleration and rotating motion and its signal processing to solve attitude perturbation of the targets.2. Motion compensation includes range alignment and phase reference selection technology. Frequency correction algorithm, spatial correction algorithm and envelope minimum entropy algorithm are respectively applied in range alignment. Phase compensation is according to selection of the phase reference.3. Joint time-frequency analysis technology is proposed in focusing imaging instead of traditional range-Doppler method. It could apparently improve the image quality. Time-frequency resolution and cross term interference of some kinds of typical time-frequency distribution are analyzed in the dissertation. A combined time-frequency method and a reassigned method are proved to get better ISAR image.4. ISAR imaging of multi-targets, taken ballistic missile and fake targets for example, is given to prove the feasibility of recognition. It establishes the foundation for further research of target recognition.