With the development of the array signal processing techniques, more and more robust methods are proposed for non-stationary interference cancellation at the beamforming stage. Among these methods, null widening methods or well-known covariance matrix taper (CMT) methods are the research hotspots. However, the typical CMT-class methods modified the whole covariance matrix with the same taper matrix, which means that all the nulls produced by the covariance matrix will be widened to the same width in cosine angular domain. This will make a waste of degrees of freedom (DOFs) in the scene that different interference sources have a different degree of non-stationarity. In this Letter, also adopting CMT structure, a flexible widening method is discussed, which utilises the relationship between each eigenvector and the steering vector of each interference source. The proposed method can widen different nulls with different width, which can save the consumption of DOFs as many as possible according to the demand. Besides, as a subspace-based method, it can preserve the minimal sample support property. The simulation results show the effectiveness of the proposed method.

中文翻译：

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一种具有多个单独加宽零点的灵活鲁棒自适应波束成形方法

随着阵列信号处理技术的发展，越来越多的鲁棒方法被提出用于波束成形阶段的非平稳干扰消除。在这些方法中，零点扩展方法或众所周知的协方差矩阵锥度（CMT）方法是研究热点。然而，典型的 CMT 类方法用相同的锥度矩阵修改了整个协方差矩阵，这意味着协方差矩阵产生的所有零点将在余弦角域中加宽到相同的宽度。这会在不同干扰源具有不同非平稳度的场景中浪费自由度（DOF）。在这封信中，同样采用 CMT 结构，讨论了一种灵活的加宽方法，它利用了每个特征向量和每个干扰源的导向向量之间的关系。所提出的方法可以用不同的宽度加宽不同的零点，可以根据需要尽可能多地节省DOF的消耗。此外，作为一种基于子空间的方法，它可以保留最小样本支持特性。仿真结果表明了所提出方法的有效性。