一种基于时频分布尺度变换的ISAR成像新方法

A New Method of ISAR Imaging Based on The Scale Transform in Time-Frequency Distribution Plane

空中或海面目标复杂运动所产生的方位二次相位项,会造成方位成像的严重散焦;而传统的RD成像方法、WVD瞬时成像方法、Radon-Wigner成像方法和DechirpClean成像方法由于成像效果差或运算效率低等因素,不适合复杂运动目标的ISAR成像;因此,针对这些问题,本文提出了一种基于时频分布尺度变换的ISAR成像新方法,即把包络对齐后的各距离单元数据变换到时频平面内,通过尺度变换,解信号瞬时时间和相关函数延迟量的耦合影响,把方位二次相位项所产生的时频平面内的斜线校正成平行于时间轴的直线,并沿时间轴进行能量积累,减少交叉项的影响,最终对复杂运动目标进行高分辨ISAR成像.该方法成像效果好,同时,可以通过快速变换算法实现,因此,运算效率较高,适合实时成像.最后,通过仿真和实测数据验证了该方法的有效性.

The azimuth quadratic phase term caused by the complex movement of target in the air or on the sea deteriorates the azimuth focusing quality.RD imaging algorithm,WVD imaging algorithm,Radon-Wigner imaging algorithm and DechirpClean imaging algorithm,due to bad imaging effect and inefficient operation and so on,are unfit for ISAR imaging of the complex motion target.Since,this paper shows a new method of ISAR imaging based on the scale transform in time-frequency distribution plane that changes each range cell data after range alignment correction to the new data in the time-frequency plane and solves the coupling effect between the signal time and the correlation function delay by the scale change. In doing that, the bias caused by the azimuth quadratic phase term becomes the beeline parallel to the time axis, at the same time, the ISAR image of the complex motion target can be acquired by the energy accumulation along the rectified beeline in the time-frequency plane. This method has many advantages,including the nice imaging effect and the high efficient operation and so on. The simulated and real data result confirm the effectiveuess of this method at the end of this paper.