Processing of Airborne Microwave Photonic SAR Raw Data With Inaccurate RSF

Due to system instability and other reasons, the actual range sampling frequency (RSF) of the system may deviate from the ideal value for the microwave photonic synthetic aperture radar (SAR). This deviation may lead to severe residual range cell migration (RCM) and even range defocus after imaging, which can seriously affect the image quality. To resolve this problem, this article proposes an airborne microwave photonic SAR imaging algorithm based on inaccurate system parameter estimation. First, the algorithm estimates and compensates for the range spatial-variant motion error to eliminate the effect of this motion error on the remaining RCM and range defocus. Second, based on the minimum entropy criterion of the image, we use the optimization model to estimate the actual RSF. Finally, the existing wide-beam autofocus method is used to correct the azimuth spatial-variant motion error. The simulation data and the measured data processing results verify the effectiveness of the proposed method.