ISAR越距离单元走动校正的近似极坐标算法

Approximately polar formatting algorithm to compensate migration through resolution cells in ISAR imaging

在ISAR系统中,通常假设不发生越距离单元走动,并应用距离多普勒(RD)算法获得目标的ISAR像。但是当雷达具有较高的分辨率,目标的尺寸较大,或目标在成像相关时间内转过了较大的角度时,散射点的越距离单元走动难以避免。为校正越距离单元走动,提出了一种近似极坐标算法。该算法将相关时间内的雷达回波数据近似为波数域梯形区域上一系列的采样点,并插值得到波数域矩形区域上的采样点,最后通过傅里叶变换得到目标的ISAR像。在目标均匀转动的假设下,该极坐标算法通过近似,不再要求已知目标的转角信息,并且能够较好地校正散射点的越距离单元走动。最后的仿真结果证实了算法的有效性。

In the ISAR imaging, the Range-doppler algorithm is usually applied, with the assumption that migration through resolution cells does not take place. But when the radar has high resolution, and the largesize targets rotate through a big angle, scatter migration through resolution cell will occur. An approximately polar formatting algorithm is proposed to compensate scatter migration through resolution cells. In the algorithm, the radar signal data received in the coherent integration interval is approximated as the samples in the trapezia area of the wave number space, and the values of uniform samples in the rectangle area are computed through interpolation, then the Fourier transform is applied to obtain the target ISAR image. With the assumption that targets uniformly rotate, the approximately polar formatting algorithm can efficiently compensate migration through resolution cells without the knowledge of target rotation angles. Finally the simulation results demonstrate the effectiveness of the algorithm.