Study On ISAR Motion Compensation

The objects of ISAR imaging are usually non-cooperative targets. So the motion compensation is a key technique in ISAR. The motion of a moving target relative to the radar can be decomposed into two parts:the translational motion of a reference point in the target and the rotational motion of others about the reference point. Only the latter is useful to the imaging. The former does not contribute to the imaging and is harmful. It influences ISAR imaging in two aspects:First,it causes the range misalignment of the range profiles which makes the processing in cross-range impossible. Second,it introduces an additive phase component which induces defocus in cross-range. Therefore,the task of the motion compensation is to remove out the translational motion before imaging. It is usually divided into two steps:range alignment and phase compensation. In this article,we have a deep study on the ISAR motion compensation algorithms by combining with the ISAR real data which aims for a better-quality image of ISAR.In the preface to this dissertation,the basic idea the development of the ISAR are introduced briefly. And the main contribution of this dissertation is summarized here.Chapter 2 exposits the problem of the ISAR motion compensation in detail after the principle of the ISAR imaging is described.In chapter 3 the principles of the main range alignment methods at the present time are detailed and further the performance of these methods is analyzed. Subsequently the concrete implementation steps of them and some measurements for further improving the alignment accuracy are presented. Finally,the alignment results of the ISAR real data achieved by these methods are shown.In chapter 4,firstly a detailed exposition of the current main methods of ISAR. phase compensation is presented. Secondly we apply the ROPE algorithm to ISAR phase compensation and illustrate how to use it. Finally,by combining with the ISAR real data,the performance of the ROPE is compared with the other methods. The fact demonstrates that ROPE is an effective method for phase compensation and accomplished simply. It has good compensation performance superior to some existing methods. In the end,conclusions and possible future work are explained.