作为一种特殊的新型双基合成孔径雷达(SAR)成像模式,弹载双基前视SAR(Missile-borne Bistatic Forward-Looking SAR,MBFL-SAR)可实现末端俯冲段前视2维成像.然而距离历程中双根号及高阶项的同时存在导致其2维频谱难以有效获得,且收发平台高度的不断变化和运动方向的不同造成回波相位的空变特性.该文提出一种基于斜距等效的MBFL-SAR相位空变校正方法.该方法利用修正的双曲线斜距模型将具有双根号和高阶项的距离历程表达式等效并简化为单根号斜距表达形式,进而利用驻定相位原理求得其高精度2维频谱;随后通过多项式高阶拟合的方法精确补偿频谱中空变的相位项,完成场景成像聚焦.该方法可高精度成像且相对于传统方法聚焦性能有显著提高.最后,通过仿真验证了所提方法的有效性.%As a new and special bistatic SAR imaging mode, Missile-borne Bistatic Forward-Looking SAR (MBFL-SAR) can perform Two-Dimensional (2D) imaging during the terminal diving period of missile. However, double square root and high order terms in range history make it difficult to obtain its 2D frequency spectrum effectively. The changing heights and different velocities of the transmitter and the receiver yield to the space variant characteristic of echo signal phase. This paper presents a phase space-variance correction method for MBFL-SAR based on the revised equivalent range equation. In this method, the range equation containing double square root and high order terms is equivalent and simplified to one only containing single square root, based on which 2D frequency spectrum with high precision is gained using the principle of stationary phase. Then, the space variant phase terms of 2D frequency spectrum are compensated accurately through high order polynomial fitting, followed by the focus of the imaging scene. This method can perform imaging with high precision and is more efficient than the traditional algorithm. Finally, the simulation experiments validate the effectiveness of the proposed algorithm.
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