基于子空间的对角加载水平估计

Diagonal Loading Level Estimation Based on Subspace

Capon波束形成器通常利用对角加载方法来提高稳健性能。然而,对角加载方法的主要缺陷是不容易可靠地获得对角加载水平,从而影响加载效果。由子空间正交理论,噪声与信号子空间相垂直,因此当加载后的导向矢量与真实导向矢量重合时,加载后的导向矢量与噪声子空间垂直。基于这样的特性建立了一个代价函数。分析表明,这个代价函数为一凸问题,通过凸优化软件求解可以很容易地获得合适的加载水平,且与不确定集的参数值无关。仿真结果表明,利用该文获得的加载水平,Capon波束形成器能够有效地提高其稳健性能。

In general,the Capon beamformer uses diagonal loading approach to improve the robustness.However,the main shortcoming of the diagonal loading approach is that there is no easy and reliable way of choosing the loading level,hence the performance may degradation.According to the subspace orthogonal theory,the noise subspace and the signal subspace are vertical,then the loaded steer vector which coincides the real one and the noise subspace are also vertical.In this paper,we construct a cost function based on the fact we formulated above.Via analyzing the characteristic of the cost function deeply,we find that the cost function is a convex optimization problem and can be solved by convex optimization program.Based on our cost function,we can choose the appropriate loading level easily,which is not related to the uncertainty parameter.Using the appropriate loading level,the proposed robust Capon beamformer can be computed at a comparable cost.Its excellent performance is demonstrated via a number of numerical simulations.