一种基于改进WLBF频谱的异构双基地前视SAR成像算法

An imaging algorithm for heterogeneous bistatic forward-looking SAR based on modified WLBF spectrum

异构平台组成的双基地前视合成孔径雷达(SAR)配置灵活,可实现多种构型下的前视成像,具有潜在的应用价值。然而特殊的几何构型使得其回波信号具有新的特性,给频谱模型的推导及成像算法的设计带来不便。针对这一问题,提出了一种基于改进WLBF(Weighted Loffeld's Bistatic Formula)频谱的双基地前视SAR成像算法。首先,引入时域去走动和切比雪夫降阶法,减小了传统频谱模型中相位历程的加权分割误差和二阶展开误差,在此基础上推导了回波信号的改进WLBF频谱表达式。然后,使用切比雪夫多项式将改进WLBF频谱展开并设计了双基地前视SAR成像算法。最后,对频谱模型和成像算法进行了仿真分析。结果表明所提改进WLBF频谱模型与传统频谱模型相比具有较高的精确度,设计的成像算法可满足异构双基地大前视系统的成像要求。

The bistatic forward-looking Synthetic Aperture Radar（SAR）composed by heterogeneous platforms has potential applicability for its flexibility in realizing forward-looking imaging for various configurations.Nevertheless,the special configuration brings new properties to echo signals,making it inconvenient to derive the spectrum model or design imaging algorithm.For this issue,a bistatic forward-looking SAR imaging algorithm is proposed based on the modified Weighted Loffeld’s Bistatic Formula（WLBF）spectrum.First,the range walk removal and Chebyshev order reduction method are introduced to decrease the weighted segmentation errors and second-order Taylor expansion errors in phase history of the traditional spectrum model.On this basis,a modified WLBF spectrum model is derived.Then,the modified WLBF spectrum is expanded by Chebyshev polynomials,and thus a bistatic forward-looking SAR imaging algorithm is designed.Finally,simulations of the spectrum model and imaging algorithm are conducted.The results show that the proposed modified WLBF spectrum model has better accuracy compared with traditional ones,and the designed imaging algorithm can meet the imaging requirement for the heterogeneous bistatic system with high forward-looking angle.