适合于大型平稳和机动目标的成像算法

The Imaging Algorithm for Steadily Flying or Maneuvering Big Targets

逆合成孔径雷达成像一般采用距离－多普勒（ Ｒ— Ｄ）成像方法［１］，在这方法中， 距离走动一般不予考虑，实际当目标较大，目标周围散射点通常发生较大的距离走动，我们己经提出一种距离走动校正方法［２］，但是这种方法一股要求散射点分布比较稀疏，且多普勒走动不严重，对于机动目标，这方法就失效了，为此，我们提出，根据低分辨回波或高分辨回波，对目标中心或重心对准聚焦后，在目标数据域通过时间的尺度变换，即通过ｋｅｙｓｔｏｎｅ插值的方法（或者方位向ＤＦＴ—ＩＦＦＴ，或方位向ＳＦＴ—ＩＦＦＴ），校正距离走动，距离压缩后（ＩＦＦＴ），对平稳飞行目标，只需要方位压缩（方位 ＦＦＴ），就可获得目标像，对机动目标，要分距离单元进行时频分析，可以采用已有的瞬时成像方法，获得距离一瞬时多普勒动态像，仿真数据和实测数据的处理表明这种方法是有效的．

Usually Range-Doppler(R-D) algorithm is employed in inverse synthetic aperture radar(ISAR) imaging, and migration through resolution cell (MTRC) is not considered, in fact, the scatterers around the target usually take place MTRC if the size of target is large. We have proposed one method to compensate MTRC, but which requires that the distribution of scatterers is sparse, and the Doppler migration is also small, for maneuvering target, this method is not effective. In this paper, we first align and focus the high resolution radar echoes, then we do time scale transform in target's wave-number domain, that is 'keystone' interpolation (which also can be realized by DFT-IFFT or SFT-IFFT in azimuth direction), to compensate MTRC, after range compress (IFFT), for steadily flying target, target image can be obtained only after azimuth compress, for maneuvering target, time-frequency analysis must be taken for every range cell, and the existing instantaneous imaging methods are also effective to obtain Range-instantaneous Doppler imsging. Simulate data and real data prove that this method is effective.