一种加载量迭代搜索的稳健波束形成

Diagonal loading level estimation for robust beamforming

当阵列的导向矢量并不精确已知时,自适应波束形成有较大的性能损失。为提高波束形成的稳健性,对角加载成为一种常用的方式。但困扰这类方法的核心问题是合适的加载量如何确定。粗估导向矢量经对角加载后得到修正的导向矢量,如果加载量合适,则修正后的导向矢量接近真实导向矢量,即与噪声子空间的正交性变好。基于以上分析,构造修正导向矢量向信号子空间和噪声子空间投影的加权代价函数来评价加载量的合适与否,进而提出一种迭代搜索合适加载量的方法。计算机仿真验证了方法的有效性,与同类方法对比显示其优越性。

Often in practice the knowledge of the array steering vector is imprecise, the adaptive beamformer may suffer considerable performance degradation. In order to improve the robustness of the beamfromer, diagonal loading has been a popular approach. However, for most of these methods, it is not clear how to choose the appropriate diagonal loading level. Through diagonal loading processing, the modified steering vector is obtained from the coarse steering vector. The more appropriate diagonal loading level is, the more the modified steering vector approaches the true steering vector, the better the orthogonality between the modified steering vector and the noise subspace becomes. Based on the analysis, a cost function which is combined by the two norms of the modified steering vector respectively projected to the noise subspace and signal subspace is given for evaluating the diagonal loading level. Furthermore, an iterative search method for estimating the loading value is proposed. Simulations demonstrate effectiveness and robustness of the proposed method compared with other methods.