基于伪逆极坐标傅里叶变换的快速ISAR方位定标

Fast Cross-range Scaling for ISAR Imaging Based on Pseudo Polar Fourier Transform

在逆合成孔径雷达(ISAR)成像中,由距离多普勒或时频分析方法得到的ISAR图像方位向仅是目标的多普勒频率分布,不能反映目标的真实形状,需对ISAR图像进行方位定标。该文提出一种快速的ISAR方位定标方法来估计目标的旋转角速度(RAV)。首先,该方法利用高效的伪逆极坐标快速傅里叶变换把两幅不同时刻ISAR图像的旋转运动转化为沿极角的平移运动。然后,在极坐标域定义了一种新的积分相关代价函数来粗估目标的RAV。最后,通过采用二分法估计得到最优的RAV,进而实现ISAR方位定标。相比于现有方位定标算法,所提方法避免了插值操作带来的精度损失和高计算复杂度问题。计算机仿真和实测数据实验结果证明了所提方法的有效性。

For the Inverse Synthetic Aperture Radar(ISAR)imaging,the ISAR image obtained by the Range-Doppler(RD)or time-frequency analysis methods can not display the target's real shape due to its azimuth relating to the target Doppler frequency,thus the cross-range scaling is required for ISAR image.In this paper,a fast cross-range scaling method for ISAR is proposed to estimate the Rotational Angular Velocity(RAV).Firstly,the proposed method utilizes efficient Pseudo Polar Fast Fourier Transform(PPFFT)to transform the rotational motion of two ISAR images from two different instant time into translation in the polar angle direction.Then,a new cost function called integrated correction is defined to obtain the RAV coarse estimation.Finally,the optimal RAV can be estimated using the Bisection method to realize the cross-range scaling.Compared with the available algorithms,the proposed method avoids the problems of precision loss and high computational complexity caused by interpolation operation.The results of computer simulation and real data experiments are provided to demonstrate the validity of the proposed method.