一种改进的ISAR图像方位向定标方法

确定逆合成孔径雷达（ISAR）图像的方位向像素尺寸,即方位向定标,是正确获得目标外形和尺寸等特征信息的前提。ISAR图像的方位向像素取决于雷达波长和目标相对于雷达视线在相干积累时间内的转角,前者是已知的,但后者在对非合作目标成像方式下难以确定。在研究已有定标算法的基础上,提出了一种改进的ISAR图像方位向定标方法,即首先用最大对比度（IC）和质量评估（QE）准则筛选出多个质量最好的包含特显点的距离单元,然后提取这些单元内特显点的回波信号并估计各特显点的调频率,最后由特显点的距离坐标和调频率获取目标的转动角速度,从而实现ISAR图像的方位向定标。仿真和实测数据的处理结果表明,该算法的定标效果明显优于已有算法。

An Improved Cross-Range Scaling Method for ISAR

To obtain the information about target,such as the size and the shape,it is necessary to determine the cross-range resolution of the inverse synthetic aperture radar（ISAR） image.The cross-range resolution of an ISAR image depends on the radar wavelength and the rotating angle of target relative to radar-line-of-sight（RLOS） during the coherent integration time.The wavelength is known,but the rotating angle is difficult to determine due to the non-cooperative motion of the target.In this paper,an improved approach for estimating the effective rotation vector is presented by analyzing the relation between the chirp rate of the cross-range signal and the range cell.A new technique based on the multiple dominant scatterers synthesis is used in order to estimate their chirp rate.Finally,the processing results of simulated and real data show that the performance of the improved cross-range scaling method outperforms the original one.