Research On ISAR Imaging Technique For Ship Target

Inverse Synthetic Aperture Radar( ISAR) imaging for ship target mainly utilizes the relative motion between the ship and the radar to form a two-dimensional image. It is one of the hot researches in which the scholars all over the world are involved and it has both military and civil values, such as military reconnaissance, identification and detection of surface targets, technical support and guide for sea vessels. In addition to the linear motion while the ship target sail along its route direction, the waves will make the ship rotate around different directions. The complexities of the sea conditions will certainly increase the difficulties to obtain a relatively high quality ISAR image for the ship. The main content of this article are as follows:1. Two basic movements between radar and target are analyzed: the ideal rotation model and linear motion model. Rotation model imaging is the basis of ISAR imaging; linear movement can be converted to the rotation via appropriate compensation.2. The characteristics of the ship movement are analyzed and the models of three main rotation of the ship are constructed and the traditional R-D algorithm is studied. The simulation experiments show that R-D method can acquire a relatively good image when the ship target sails along a straight line or rotate under small angle.3. The vague in ISAR imaging caused by the translational movement of the ship target is analyzed and range alignment and phase compensation techniques are studied. A modified prominent point processing is proposed. Experiments show that, compared to Doppler centroid and prominent point processing, it can effectively improve the sharpness and the contrast of the ISAR image.4. For the ship target under big rotation condition, time-frequency theories and the ISAR imaging based on time-frequency technique are introduced. It replaces the Fourier transform by time-frequency distribution methods. By applying it to the imaging process, a clearer image can be gained. The simulations also show that imaging process based on time-frequency method is significantly better than traditional R-D algorithm.