中文摘要：

海上舰船目标随海浪摇摆，存在转动速度不稳定以及ISAR 成像平面时变问题，使得舰船目标ISAR 成像需要选取合适的成像时间段确保获得高质量的图像。本文首先详细分析了成像平面与舰船目标有效转速之间的关系，得出目标有效转速最大时成像平面最稳定、分辨率最高的结论，进而确定以转速最大的时段作为成像时间段的选择准则。相比已有的选择方法，本文所提方法的成像质量更好。仿真和实测数据的处理结果验证了本文所提方法的有效性。

英文摘要：

Ship targets on the sea swing because of the sea wave, which leads to instability of the rotation speed and variation of the image project plane. As a result, imaging interval selection should be taken into consideration in order to obtain a high quality ISAR image. In this paper, firstly, the relationship between effective rotating speed and image project plane is analyzed in detail, by which the conclusion that the image project plane is stable and the resolution of the ISAR image is best when the valid speed of rotation of a ship target is highest is drawn. Then a new method to select favorable imaging interval based On the rotation speed of ship targets is proposed. In comparison with existing methods, the proposed one can select a better period for ISAR imaging, which leads to an imaging result with higher quality. The effectiveness of the proposed method is verified by simulation and real data processing result.