分析了成像后的星载SAR复数图像压缩的必要性及复数图像特点, 对已有压缩算法做了简单分析。在此基础上, 提出一种基于FFT变换和加权量化的星载SAR复数图像压缩算法, 同时建立了适合SAR复数图像压缩的码率控制模型, 提出一种精确码率控制方法。实验结果表明, 以幅值PSNR和平均结构相似度以及平均相位误差为性能指标, 提出的SAR复数图像压缩算法优于现有压缩算法(JPEG2000、H.264等); 同时, 提出的码率控制算法能够实现精确码率控制。

With the rapid development of SAR missions, on-board SAR image processing is required. SAR could obtain much higher resolution images than ordinary radar, and it is very necessary to compress data before transmission, since the generated SAR data volume is much higher than the data bandwidth of the satellite downlink. In this paper, an efficient compression algorithm with accurate rate control is proposed based on SAR complex image characteristics. The algorithm applies an adaptive weighted quantizer on 2D-FFT coefficients, and then uses entropy encoder to code the quantized coefficients. Based on the established R-Q and MPE-Q statistical models, an accurate rate control is developed. We measure the compression performance with PSNR and MSSIM (Mean Structural Similarity) of the magnitude image and MPE (Mean Phase Error). With four SAR complex images compressed at different ratios, the compression performance is analyzed and compared with other algorithms including JPEG2000, H.264, etc. Experimental results show that the proposed algorithm outperforms other algorithms, and the rate control obtains high accuracy.