基于北斗卫星外辐射源的目标直接定位算法

Direct Position Determination of Moving Target Using BeiDou Satellite External Illuminators

由于北斗卫星导航系统具有全球覆盖、自主可控等优势,近年来以其作为外辐射源构建无源雷达系统成为研究热点。研究了基于多颗北斗卫星外辐射源的无源雷达目标定位问题,提出一种联合北斗卫星信号结构的直接定位算法。该算法将接收信号进行分时处理,利用北斗信号结构已知的特点,重构纯净直达波信号,继而利用纯净直达波信号对目标回波信号进行脉冲压缩。依据最大似然准则以及目标-接收机-外辐射源位置几何关系,构建脉压信号数据关于目标位置-速度估计的似然函数,通过寻找似然函数极大值得到目标位置和速度估计。此外,推导了目标定位的克拉美罗界(Cramér-Rao Lower Bound, CRLB)。仿真实验结果验证了所提算法的有效性,同时通过与现有定位方法的对比,证明所提算法具有更高的定位精度和稳健性,并且在信噪比适中时可以逼近CRLB。

Passive radar using BeiDou navigation satellites as external illuminators has been a hot area of research in recent years, since BeiDou navigation satellites has advantages of global coverage, self-development and controllability. Target localization problem in passive radar using multiple BeiDou navigation satellites as external illuminators is researched. A direct position determination algorithm combining BeiDou signal structure is proposed. The proposed algorithm divides the received signal into segments, reconstructs the pure direct path signal by using the known features of Beidou signal structure, and then applies pulse compression on the target echo signal by using the pure direct path signal. Based on the maximum likelihood criterion and the geometric relationship among the target, receiver and external illuminators, the likelihood function of the pulse compression signal data with respect to target position and velocity estimation is derived, and then, the target position and velocity estimation can be obtained by finding the maximum value of the likelihood function. Moreover, the Cramér-Rao Lower Bound(CRLB) of the target position determination is also derived. Simulation results verify the effectiveness of the proposed algorithm. Compared with existing algorithms, the proposed algorithm has higher localization accuracy and robustness, and can approach the CRLB at reasonable signal-to-noise ratios.