改进的机载斜视SAR方位大孔径方法

Improved Azimuth Large-aperture Approach for Squint Airborne SAR

由于机载SAR平台受气流颠簸的影响严重,处理机载SAR实测数据时需要采用方位大孔径方法来减小运动参数的变化。然而,当使用传统方位大孔径方法处理斜视SAR实测数据时会引起方位时域混叠现象,并最终影响成像质量。为了解决这个问题,本文首先建立了机载斜视SAR瞬时多普勒模型;在此基础上研究了子孔径方位频谱拓展及方位时域混叠现象,推导出子孔径单边拓展点数的计算公式;然后提出了改进的机载斜视SAR方位大孔径方法,避免了方位时域混叠现象的发生;最后,通过仿真和实测数据实验验证了所提算法的正确性。

Airborne synthetic aperture radar （SAR） raw data are affected by variable aircraft parameters due to atmospheric turbulence and aircraft properties. In order to decrease the influence of variable aircraft information, the azimuth large-aperture approach is thus applied in airborne SAR real-data processing. However, it will cause the aliasing of azimuth-signal in squint SAR mode and degrade the image quality. In this paper, a novel model of airborne squint SAR instantaneous dopper frequency is constructed at first, then the study of azimuth sub-aperture spectrum extension and azimuth time-domain aliasing is presented. After that, a modified azimuth large-aperture approach is proposed to eliminate the aliasing in azimuth time-domain. Finally, simulations and experimental results of squint SAR mode are all provided to demonstrate the validity of the proposed approach.