基于直升机平台SAR的方位重影抑制方法

直升机合成孔径雷达(SAR)已成为遥感领域的重要探测工具。针对平台微小高频振动导致方位重影,造成图像质量降低的问题,提出了一种振动相位补偿算法。首先利用回波录取的几何构型,推导基于直升机振动平台的SAR回波表达式,并引入雅可比-安格尔恒等式,对回波完成一阶贝塞尔级数展开,获得高频振动误差与方位向重影的关系式。然后,从直升机SAR实测数据入手,对方位相位进行差分、提取和快速傅里叶变换,得到振动频点信息,并对频点信息进行反演,得到高频误差相位。最后,利用高频误差相位对原始回波进行补偿,抑制成对回波模糊现象,从而消除方位重影。基于实测数据的成像处理结果验证了所提方法的有效性。

Azimuth Ghost Reduction Method for Helicopter-BorneSynthetic Aperture Radar Systems

Helicopter-borne synthetic aperture radar (SAR) has become one of the important tools in the remote sensing field. The tiny high-frequency vibrations of the helicopter platform cause obvious changes in echo phase and result in undesired azimuth ghost targets, which will degrade SAR image quality. According to vibration characteristics of the helicopter platform, this paper proposes a vibration phase error compensation imaging algorithm. Firstly, the expression of high resolution SAR echo from vibration platform is derived, and then first-order Bessel series is expensed by the Jacobi-Anger identity. After that, the relationship between vibration frequency and azimuth ghost target is obtained. The vibration parameters, such as vibration frequency points of propeller and rotor from real data, can also be obtained from differential phase after fast Fourier transform (FFT), and the vibration frequency parameters are extracted to construct the reference function. Finally, after compensating the phase of vibrating signals by constructing the reference function with vibration parameters, the energy of paired echoes is suppressed, and deghosted target SAR images can be obtained. The experimental results based on airborne data demonstrate the effectiveness of the proposed method.