多项式结构宽带波束形成器的性能分析及其改进

首先从理论上分析了多项式结构宽带波束形成器的鲁棒性能。分别从传声器失配误差影响下阵列波束图扰动的统计分析以及白噪声增益分析两个方面揭示了影响多项式结构宽带波束形成器鲁棒性能的内在规律。发现当波束主瓣指向处于可调范围边缘时,与指向中心相比,多项式结构波束形成器的鲁棒性能变差。然后分析了影响多项式结构宽带波束形成器阵列指向性指数的主要因素,指出了多项式结构的截断误差会导致宽带波束形成器的主瓣指向出现偏差,进而造成阵列指向性指数性能下降。为了克服现有设计结构存在的缺陷,提出了一种具有波束主瓣指向自校正能力的改进设计结构。与现有设计结构不同,所提出的设计结构中的调向功能模块能够充分反映出波束期望指向和实际指向之间存在的非线性关系,避免了现有设计方法因采用线性调向功能模块而造成较大波束指向偏差的问题,有效改善了多项式结构宽带波束形成器的性能。

Performance analysis and improvement of polynomial broadband beamformers

The robustness of the Polynomial Broadband BeamFormers(PBBF)is theoretically studied.Based on the statistical analysis of beampattern distortion in the presence of microphone mismatches and the analysis of white noise gain,the inherent properties on the robustness of the PBBF are revealed.It is shown that,when the main lobe of the beam is steered to the edge of look direction range,the robust performance of PBBF is worse than that when steered to the center.Moreover,the main factors affecting the directivity index of the PBBF are also studied.It is pointed out that the truncation error of the polynomial structure may lead to large deviation of the main lobe orientation,which can significantly deteriorate the directivity index as a result.In order to overcome the drawback of the existing design,we then present an improved design structure with a self-calibration capability.Compared with the existing design,the steering module used in the proposed structure can fully reflect the nonlinear relationship between the expected and the actual beam orientation,thus avoiding the large steering deviation caused by the linear steering module used in the existing structure,which can effectively improve the performance of the PBBF.