直升机载旋转式合成孔径雷达成像振动误差补偿算法

A Vibration Error Compensation Algorithm for Helicopter-borne Rotating Synthetic Aperture Radar

作为一种新型成像体系,旋转式合成孔径雷达(ROSAR)能够通过天线的旋转替代平台运动来获得合成孔径并实现成像。但是直升机平台的高频振动会在信号回波中引入严重的相位误差并导致最终图像质量下降。由于距离与相位的耦合,传统成像算法如距离多普勒算法(RDA)对信号处理后,无法直接估计出振动误差相位,因此现有的自聚焦算法无法用来改善成像性能。在本文中,提出了一种新的ROSAR成像处理流程来补偿由直升机高频振动引入的相位误差。首先建立了ROSAR包含振动误差的回波信号模型,然后利用双重多普勒Keystone变换(DDKT)对斜距历程及振动误差引起的距离徙动(RCM)进行校正,在此基础上,推导了详细的包含非距离依赖振动相位误差的信号回波解析表达式。最后利用经典的自聚焦算法即可获得聚焦良好的ROSAR图像。仿真实现结果证明了所提算法的有效性。

As a new imaging framework,the rotating synthetic aperture radar(ROSAR)obtains synthetic aperture by antenna rotation instead of platform motion.However,the high-frequency vibration on helicopters will cause severe phase error in signal echo and performance degradation of the final image.The vibration phase error can’t been estimated via conventional imaging algorithms,such as Range-Doppler Algorithm(RDA),due to range and azimuth coupling,so the existing autofocus methods cannot be used to improve the imaging performance.In this letter,a new ROSAR imaging procedure was proposed to compensate the phase error caused by high-frequency vibration of helicopters.Firstly,the vibration model of ROSAR signal echo was established;secondly,double Doppler Keystone transform(DDKT)was adopted to correct the range cell migration(RCM)induced by slant range history and vibration error;thirdly,the analytical echo expression with range-independent vibration phase error has been derived with more details provided.Finally,the focused image can be obtained via classical autofocus algorithms.The experimental results with simulation data verified the effectiveness of the proposed method.