基于直达波和熵的一站固定式双基成像算法

一站固定式双基合成孔径雷达（BiSAR）相比于传统的单基SAR有其独特的优势，但是由于收发平台分置，在实际的双基系统中，通常会在接收到的信号中引入同步误差。此外，不精确的参数如移动端的位置，会使得传统的同步算法和成像算法效果降低。为了解决上述问题，提出了一种基于图像最小熵原则和直达波直接对未同步的原始回波进行成像处理的算法。该算法将同步过程和成像过程结合，避免了传统同步算法的复杂数学分析建模，并精确计算了移动端的位置，从而提高了成像质量。首先利用直达波信号去除同步误差，其次对直达波信号进行峰值相位提取，计算收发端的最近距离，搜索一致压缩后的图像进行最优熵对应的值，进而完成直达波的补偿和精确的移动端位置，完成图像的聚焦。

Algorithm based on direct signal and entropy optimization for spaceborne/stationary BiSAR imaging

Compared to monostatic SAR, BiSAR brings lots of benefits. However, because the transmitter and receiver are put on different platforms, synchronization errors are generally introduced into the received data in real bistatic systems. Additionally, the position of the transmitter would affect the quality of traditional synchronization and imaging algorithms. Considering the situations above, an imaging algorithm based on entropy optimization and direct signal with non synchronous echo directly is proposed. It could avoid complex mathematical modeling analysis and could get accurate position of transmitter. First, the synchronization errors are eliminated through matching echo signal with the direct signal. Second, extract the phase of direct signal and calculate the range between the transmitter and receiver. Then search the accurate imaging parameters based on entropy optimization. After that the image could be well focused.