Xie Jian, Wang Qiuping, Wang Yuexian, Yang Xin
Electronics and Information School, Northwestern Polytechnical University, Xi'an 710072, China.
Sensors (Basel). 2020 Mar 30;20(7):1914. doi: 10.3390/s20071914.
Digital communication signals in wireless systems may possess noncircularity, which can be used to enhance the degrees of freedom for direction-of-arrival (DOA) estimation in sensor array signal processing. On the other hand, the electromagnetic characteristics between sensors in uniform rectangular arrays (URAs), such as mutual coupling, may significantly deteriorate the estimation performance. To deal with this problem, a robust real-valued estimator for rectilinear sources was developed to alleviate unknown mutual coupling in URAs. An augmented covariance matrix was built up by extracting the real and imaginary parts of observations containing the circularity and noncircularity of signals. Then, the actual steering vector considering mutual coupling was reparameterized to make the rank reduction (RARE) property available. To reduce the computational complexity of two-dimensional (2D) spectral search, we individually estimated -axis and -axis direction-cosines in two stages following the principle of RARE. Finally, azimuth and elevation angle estimates were determined from the corresponding direction-cosines respectively. Compared with existing solutions, the proposed method is more computationally efficient, involving real-valued operations and decoupled 2D spectral searches into twice those of one-dimensional searches. Simulation results verified that the proposed method provides satisfactory estimation performance that is robust to unknown mutual coupling and close to the counterparts based on 2D spectral searches, but at the cost of much fewer calculations.
无线系统中的数字通信信号可能具有非圆特性，这可用于提高传感器阵列信号处理中到达方向（DOA）估计的自由度。另一方面，均匀矩形阵列（URA）中传感器之间的电磁特性，如互耦，可能会显著降低估计性能。为解决此问题，开发了一种用于直线源的稳健实值估计器，以减轻URA中未知的互耦影响。通过提取包含信号圆特性和非圆特性的观测值的实部和虚部，构建了一个增广协方差矩阵。然后，对考虑互耦的实际导向矢量进行重新参数化，以使秩缩减（RARE）特性可用。为降低二维（2D）谱搜索的计算复杂度，我们按照RARE原理分两个阶段分别估计x轴和y轴方向余弦。最后，分别从相应的方向余弦确定方位角和仰角估计值。与现有解决方案相比，所提方法计算效率更高，涉及实值运算，并将二维谱搜索解耦为两次一维搜索。仿真结果验证了所提方法提供了令人满意的估计性能，对未知互耦具有鲁棒性，且接近基于二维谱搜索的对应方法，但计算量要少得多。
