辐射源直接定位是一种能够直接从原始采样信号中估计出辐射源位置的无源定位技术.利用单颗卫星对地球表面固定辐射源进行直接定位具有定位精度高、灵活性强等特点,因而具有重要的研究价值.然而,传统空域子空间数据融合直接定位方法缺乏对多普勒信息的充分利用,其在单星直接定位场景下的定位性能不足.现有空时子空间数据融合直接定位方法提升了该场景下的定位性能,但其仍存在低信噪比条件下定位精度和分辨率不足的问题.针对这些问题,该文提出了一种改进实值空时子空间数据融合的单星直接定位方法,实现了辐射源高程已知条件下单星对多辐射源的直接定位.首先,该文基于WGS-84地球椭球面模型建立联合到达角和多普勒频率的空时信号模型,充分利用了卫星相对辐射源高速运动产生的多普勒频移信息.随后,该文引入了托普利兹矩阵调整方法,对空时信号模型中接收信号的协方差矩阵进行分块,然后对分块矩阵进行调整,并使用前后向平滑和空时子空间酉变换技术来得到实值的空时子空间.最后,该文融合多个时隙的空时子空间数据建立定位的代价函数,同时设计出符合特征空间思想的分子函数,得到改进的代价函数,再通过网格搜索方法估计出辐射源的位置.仿真结果表明:所提方法在低信噪比下相比MUSIC(Multiple Signal Classification)直接定位方法、MVDR(Minimum Variance Distor tionless Response)直接定位方法、ML(Maximum Likelihood)直接定位方法和U-ST-SDF(Unitary Space-time Subspace Data Fusion)方法具有更好的定位性能.
Improved Single-Satellite Direct Position Determination Method via Real-Valued Space-Time Subspace Data Fusion
Direct position determination of radiation sources is an unpowered localization technique that estimates the po-sition of radiation sources directly from the raw sampled signals.Direct localization of fixed radiation sources on the Earth's surface using a single satellite has significant research value due to its high positioning accuracy and strong flex-ibility.However,traditional spatial subspace data fusion methods used for direct localization lack sufficient utilization of Doppler information,leading to inadequate positioning performance in single-satellite direct localization scenarios.Ex-isting space-time subspace data fusion methods have improved positioning performance in such scenarios,but they still suffer from poor accuracy and resolution under low signal-to-noise ratio conditions.To address these issues,this study proposes an improved single-satellite direct localization method based on real-valued space-time subspace data fusion,enabling direct localization of multiple radiation sources with known elevation.First,the study establishes a space-time signal model based on the WGS-84 Earth ellipsoid model,incorporating both the arrival angles and Doppler frequen-cies,effectively utilizing the Doppler frequency shift information caused by the satellite's relative high-speed motion with respect to the radiation sources.Subsequently,this study introduces the Toeplitz matrix adjustment method to block-adjust the covariance matrix of the received signals in the space-time signal model.Forward-backward smoothing and space-time subspace unitary transformation techniques are employed to obtain a real-valued space-time subspace.Subse-quently,this paper combines space-time subspace data from multiple time slots to construct the cost function for local-ization and designs a numerator function based on the feature space concept to improve the cost function.The radiation source's position is then estimated using a grid search method.Simulation results demonstrate that the proposed method outperforms the multiple signal classification(MUSIC)direct localization method,minimum variance distortionless re-sponse(MVDR)direct localization method,maximum likelihood(ML)direct localization method,and unitary space-time subspace data fusion(U-ST-SDF)method in low signal-to-noise ratio conditions,exhibiting superior positioning performance.
direct position determination(DPD)subspace data fusion(SDF)Toeplitz matrixarrival anglesDoppler frequency
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