星载SAR方位向频率与多普勒频率的差异及其对成像分辨率的影响

Difference between Doppler Frequency and Azimuth Frequency and Its Influence on the Azimuth Resolution of Spaceborne SAR

为研究一种典型双基地结构SAR的精细成像算法。通过精确的方位频率表达式,详细比较了多普勒频率与方位频率的区别和联系。以往在合成孔径成像处理中通常以成像单元的多普勒频率代替方位频率,对实际精细成像的方位分辨率影响不大,误差一般都在4%以内;但是,在大的斜视角、大的发射信号调频率、波长较长等参数条件下如果忽略2种频率的差异有可能引起高达10%甚至27%以上的方位分辨率误差。只有针对不同参数的SAR系统和不同的成像精度要求,才能确定是否可以用多普勒频率代替方位频率。仿真结果验证了本文方法的有效性。

This paper compared the Doppler frequency and azimuth frequency in detail during the researching of a representative bistatic SAR imaging theory and found that using Doppler frequency instead of azimuth frequency in the general SAR processing with traditional imaging algorithms has little influence on the azimuth resolution of the fine imaging , the error is less than 4%. But if the differences between the two frequencies are neglected in the condition of larger squint angle, bigger transmit signal chirp rate, and longer wave length, the azimuth resolution error may reach as much as 10% even 27%. So, whether Doppler frequency can be used instead of azimuth frequency depends on the SAR systems with different specific parameters and the different requirements in specific imaging precision.