频率步进SAR虚拟阵列模型成像方法

Imaging approach for frequency-stepped SAR with virtual array model

针对频率步进合成孔径雷达(SAR)采用经典逆傅里叶变换成像方法时距离向无模糊测绘带宽度有限的问题,提出一种将频率步进SAR脉冲串信号等效为沿航迹分布的虚拟阵列雷达信号的模型及成像处理方法,并利用改进的后向投影方法实现对目标的无模糊成像。建立了频率步进SAR虚拟阵列模型,给出了基于该模型的高分辨距离像合成方法,并通过在原始后向投影方法的基础上引入距离偏移校正和二次相位补偿,实现了对目标的精确二维成像。结果表明:频率步进SAR虚拟阵列模型成像方法不受频率步进雷达无模糊测绘带宽度的理论限制,可以实现较宽测绘带内各目标的无模糊、快速成像。

Aimed at the problem that frequency-stepped synthetic aperture radar （SAR） images obtained by classic inverse Fourier transform method have a limit on unambiguous range, a new model which takes the pulse sequence of frequency-stepped SAR as an along-track virtual array radar signal and its corresponding im- aging method for frequency-stepped SAR were proposed. Meanwhile, unambiguous imaging using modified back-projection method is realized. The virtual array model for frequency-stepped SAR signal was established and the synthesis method of high resolution range profile based on this model was presented. By embedding range migration correction and secondary phase compensation into original back-projection algorithm, a precise two-dimensional image of the target was also obtained. All the results show that the virtual array model based imaging method for frequency-stepped SAR is not restricted by the theoretical limit of frequency-stepped sig- nal＇ s unambiguous range and can get images without range ambiguity for wide swath imaging rapidly.