基于矩阵分布式重构的正交极化阵DOA估计
Orthogonal Polarization Array DOA Estimation Based on Matrix-distributed Reconstruction
-
摘要: 对于子空间类算法而言,协方差矩阵估计的准确性将很大程度的影响到算法的性能,理想的协方差矩阵估计为无限长的信号运算得到,实际中大多使用有限快拍数的采样数据进行协方差矩阵估计。有学者研究表明,阵列协方差矩阵位于由接收信号的所有可能导向矢量构成的子空间中,可以利用子空间组成的完备重构矩阵对协方差矩阵进行重构,此类方法需要对阵列的所有可能接收信号进行积分,并获得由其主成分构成的重构矩阵。为了减小低快拍数和低信噪比下采样协方差矩阵误差,并降低其运算复杂度,提出了一种基于正交偶极子组成的均匀圆阵的采样协方差矩阵重构方法。将整体阵列划分为子阵1和子阵2,子阵内部仅存在空域相位差而没有极化敏感特性,子阵间空域相位差相同,极化敏感特性不同。并基于均匀圆阵的结构特点,给出了特殊的重构矩阵,特殊的重构矩阵不依赖信号特性,仅与圆阵结构相关,通过理论分析和仿真测试可以得到,特殊的重构矩阵在维度和复杂度方面均优于全角度域和极化域积分的重构矩阵。该方法将重构算法应用到了极化敏感阵列领域同时减少了运算的复杂度,通过后续对低信噪比和低快拍数的仿真测试表明,重构后的协方差矩阵可以有效提高信号子空间和理想噪声子空间的正交性,使用重构的协方差矩阵进行极化空间谱估计提高了在恶劣环境下的信源分辨力。Abstract: The accuracy of covariance matrix estimation greatly affects the performance of subspace algorithms. The ideal covariance matrix estimation is obtained through infinite signal operations; however, in practice, a limited number of samples are mostly used for covariance matrix estimation. Scholars have shown that the covariance matrix of an array is located in a subspace composed of all possible directional vectors of the received signal. The complete reconstruction matrix composed of subspaces can be used to reconstruct the covariance matrix. This method requires integrating all possible received signals of the array and obtaining a reconstruction matrix composed of its principal components. A sampling covariance matrix reconstruction method based on a uniform circular array composed of orthogonal dipoles is proposed to reduce the sampling covariance matrix error and computational complexity in low snapshot count and low signal-to-noise ratio down sampling. The overall array was divided into subarray 1 and subarray 2, where only a spatial phase difference is present within the subarray and no polarization-sensitive characteristics. The spatial phase difference between subarrays was the same; however, the polarization sensitive characteristics were different. Based on the structural characteristics of a uniform circular array, a special reconstruction matrix is provided. The special reconstruction matrix does not depend on signal characteristics and is only related to the circular array structure. Through theoretical analysis and simulation testing, it can be concluded that the special reconstruction matrix is superior to the reconstruction matrix integrated in the full angle domain and polarization domain in terms of dimension and complexity. This method applies the reconstruction algorithm to the field of polarization-sensitive arrays while reducing computational complexity. Subsequent simulation tests at low signal-to-noise ratio and low number of snapshots showed that the reconstructed covariance matrix can effectively improve the orthogonality between the signal subspace and the ideal noise subspace. Using the reconstructed covariance matrix for polarization space spectrum estimation improves the source resolution in harsh environments.