基于幅度响应约束的稳健自适应宽带波束形成

Robust Adaptive Broadband Beamforming Based on Constraints Magnitude Response

针对信号方向失配会导致自适应波束形成算法的性能急剧下降这一问题,提出一种基于幅度响应约束的稳健自适应宽带波束形成方法。通过对阵列波束指向附近范围内的波束幅度响应施加约束来克服对信号方向失配的敏感性,并结合频率不变技术,使阵列波束图在主瓣区域内波束图近似保持频率不变特性,然后采用参考频率上幅度响应约束的优化方法来确定最优权值。仿真结果表明:与基于最差情况性能最优的稳健方法相比,该方法复杂度低,能灵活控制稳健的方位区域宽度和幅度响应抖动值,且不仅能有效地控制波束主瓣区域内信号的畸变,还改善了阵列输出的信干噪比,使其更接近最优值。

The performance of adaptive beamforming algorithms is known to undergo substantial degradation in the presence of even slight steering direction error. To account for mismatches, a novel robust adaptive broadband beamforming algorithm based on constraints magnitude response （CMR） was proposed. An array magnitude response constraint over the region around the array steering direction was used to increase the robustness of the optimal beamforming against steering direction mismatch. Combined with the frequency invariant tech- nique, the array beampatten kept approximately the same amplitude response to the wideband incident signal at different frequencies. The weight vector was optimized to involve minimization of a quadratic function subject to constraint on magnitude response at the reference frequency. Simulation results demonstrated that, compared with the worst-case optimization method, the algorithm had low complexity and was able to flexibly control the robust response region with specified beamwidth and response ripple. Furthermore, the proposed beam former could obtain the prescribed robustness against steering vector errors, suffered the least distortion from the directions near the steering angle,improved the output array signal-to-interference-plus-noise ratio （SINR） performance,and made SINR consistently close to the optimal one.