双基地角时变下的逆合成孔径雷达越分辨单元徙动校正算法

Correction of migration through resolution cell in bistatic inverse synthetic aperture radar in the presence of time-varying bistatic angle

采用双基地逆合成孔径雷达距离-多普勒算法成像时,目标尺寸较大或累积转角过大,会引起越分辨单元徙动现象,影响成像质量.针对双基地角时变下逆合成孔径雷达成像的越分辨单元徙动问题,提出了一种校正算法.首先,建立了双基地逆合成孔径雷达回波模型,分析了越分辨单元徙动的产生机理,并通过广义的Keystone变换实现了越距离单元徙动的校正,同时消除了目标非匀速转动对成像的影响.然后,基于图像对比度最大准则估计了图像的等效旋转中心位置,并对距离向绝对定标,进而构造补偿相位项,完成了越多普勒单元徙动的校正.仿真实验结果表明,此方法能够有效地校正双基地角时变下的越分辨单元徙动,提高成像质量.

When the size of target or the rotation angle is big, migration through resolution cell may occur in the bistatic inverse synthetic aperture radar（ISAR）, which will affect the imaging quality. Aiming at the problem of migration through resolution cell of bistatic ISAR in the presence of time-varying bistatic angle, a correction algorithm is proposed in this paper. Firstly, the echo model of bistatic ISAR is built, and the mechanism of migration through resolution cell is analyzed. Migration through range cell may be corrected through the generalized Keystone transformation, and the effect of non-uniform rotation is eliminated at the same time. Then the rotating center is estimated according to the maximum criterion of image contrast, and the range bin is scaled absolutely. A phase compensation term is constructed and the correction of migration through Doppler cell is finished. Finally, the simulations are carried out and the results show that the method proposed in this paper can solve the problem of migration through resolution cell and improve the image quality.