基于多维Kronecker积的低秩稳健超指向性波束形成方法
Low-Rank Robust Superdirective Beamforming Using Multidimensional Kronecker Products
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摘要: 超指向性波束形成器凭借其高空间指向性,能够有效抑制空间各向同性噪声,在语音通信、远场拾音等场景中发挥了重要作用。然而,其稳健性较差,对阵元不一致性和自噪声的敏感性限制了实际应用。为提高稳健性,通常需在高指向性与稳健性之间做出权衡,如使用对角加载因子约束白噪声增益。然而随着麦克风阵列规模的扩大,传统优化设计的波束形成器因参数冗余导致效率降低。基于Kronecker积的波束形成是一种计算高效的解决方案,能够在降低参数规模的同时,提高波束形成器的稳健性。但现有研究多局限于二维分解形式,对更高维度的分解结构的研究较少,尚未充分探讨比较不同的分解模式对波束形成器性能的影响。针对上述问题,本文将现有的二维Kronecker积方法推广至多维形式,提出了一种基于多维Kronecker积形式的低秩稳健超指向性波束形成方法。该方法通过将波束形成器分解为多组短滤波器的Kronecker积形式,提升设计灵活性。在不失真约束下,以最大化指向性因子为目标,交替迭代求解多组短滤波器。实验结果表明,对于不同阵列结构,所提方法在不同分解模式下均能以更少的参数 (滤波器系数个数)和更低的矩阵求逆维度实现与传统方法相当的性能,因此在实际系统中具有更高的效率。进一步地,通过分析不同分解方式对波束形成性能的影响,验证了所提方法的有效性与计算优势。Abstract: Superdirective beamformers exhibit high spatial directivity and can therefore effectively suppress spatially isotropic noise, playing a key role in speech communication, far-field pickup, and other scenarios. However, because they are highly sensitive to array imperfections and self-noise, the lack of robustness limits their practical applications. To improve their robustness, a trade-off between high directivity and robustness is typically required, such as using diagonal loading factors to constrain white noise gain. However, as the number of microphones increases, conventional robust superdirective beamformers become less efficient owing to excessive parameter redundancy. Kronecker product beamforming offers a computationally efficient solution that enhances the robustness of beamformers while reducing parameter size. Existing studies, however, are mostly constrained to two-dimensional formulations, with limited research on higher-dimensional decomposition structures and the effects of different decomposition modes on beamformer performance. To address the above issues, we extend the existing two-dimensional Kronecker product method to a multidimensional form and propose a low-rank robust superdirective beamforming method based on multidimensional Kronecker product. This method improves design flexibility by decomposing the beamformer into a Kronecker product form of multiple sets of short filters. Under a distortionless constraint, the method alternately iterates to solve for the multiple sets of short filters with the goal of maximizing the directivity factor. Experimental results show that for different array structures, the proposed method achieves comparable performance to traditional methods with fewer parameters (number of filter coefficients) and lower matrix inversion dimensions across different decomposition modes. Therefore, it exhibits higher efficiency in practical systems. Furthermore, by analyzing the impact of different decomposition approaches on beamforming performance, the effectiveness and computational advantages of the proposed method were verified.