柱体表面圆环阵稳健高增益波束形成的模态域直接优化方法研究

以无限长刚性柱体表面圆环阵为研究对象,提出了一种直接模态域稳健高增益波束形成方法,并将其应用到更实际的有限长刚性柱体表面圆环阵。该方法运用相位模态理论将波束响应表示成特征波束与模态系数的乘积后求和的形式,并结合散射理论求解了其模态域的噪声互谱矩阵。与已有的模态域稳健高增益方法需利用阵元域权值间接求取近似模态权系数不同的是,该方法利用二阶锥规划,在满足相关约束条件下直接给出了最优的模态权系数。仿真结果表明,直接模态域方法不仅能通过白噪声增益约束提高稳健性,在低频段还能通过改变模态阶数更灵活地在阵增益和稳健性之间折中,同时对旁瓣级等其它性能指标也能很好地控制,可用以有效设计实用的稳健高增益波束形成器。

On direct optimization in mode space for robust supergain beamforming of circular array mounted on a cylinder

A direct robust supergain method in mode space for the circular array mounted on an infinite rigid cylinder is proposed,and then it is also applied to the circular array mounted on a finite rigid cylinder which is more practical. According to the concept of phase modes,the beam pattern is expanded into a series of eigen-beams multiplying by modal coefficients.The modal noise cross spectral matrix is calculated from sound scattering theory.In the original modal robust supergain method,the coefficient vector in mode space is transformed indirectly from the weighting vector in sensor space.The method presented here gives the most suitable modal coefficient vector directly under the related constraint conditions based on the second-order cone programming.The results of simulation show that the direct modal robust supergain method can not only improve robustness using the white noise gain constraint,but also change the mode orders to provide compromise between array gain and robustness in low frequencies.Beam performance measures such as sidelobe level can be optimized as well as array gain,so this new method can give more effective schemes for designing practical robust supergain beamformer.