通过现场可编程门阵列(FPGA)设计并实现星载合成孔径雷达(SAR)成像处理,能够完成对多种模式星载SAR回波数据的高速处理。该文搭建的成像处理系统以子孔径极坐标格式算法(PFA)为核心,首先,在精确的多普勒中心频率估计基础上,采用基于尺度变换原理的距离向处理(PCS)与方位向高精度sinc插值级联的算法处理流程实现子孔径数据域重采样,极大地提升了处理精度与运算效率;然后,对各子孔径图像进行辐射校正消除扇贝效应,并采用加权平均算法获得了全孔径拼接图像;最后,基于Sentinel-1卫星实测数据对本系统进行了验证和分析,在系统工作频率200 MHz情况下,能够在5.92 s内实现8 192×8 192像素点的32位单精度浮点成像处理,实测数据成像结果验证了该系统的有效性,从而为实时处理奠定了技术基础。

The space-borne SAR imaging processing system is designed and implemented in this paper, which is able to deal with multi-mode echo based on field programmable gate arrays ( FPGA). The kernel of the proposed system is the sub-aperture polar format algorithm (PFA). First, by using the principle of chirp scaling (PCS) in range pulse compression and sinc interpolation in azimuth processing, which is based on the accurate estimation of Doppler centroid frequency, the resampling of the sub-aperture data is realized. Both the accuracy and the efficiency of the algorithm have been improved significantly. Next, the radiometric correction is adopted to correct the scalloping effect, meanwhile, the weighted average algorithm is used to obtain the full aperture SAR image. Finally, the experimental data based on the Sentinel-1 satellite is employed to validate and analyze the system. According to the measured results, when the FPGA works at 200 MHz, an 8 192×8 192 SAR data matrix with single precision within 5.92 s is achieved by the system proposed in this paper. The processing of the experimental data is in good agreement with proposed method. This system can be a good candidate in radar imaging field due to the effectiveness and real-time capability.

TN911.7