Legendre函数加权的声纳宽频带恒定束宽波束特性分析*

为了处理水声信号,声纳阵列通常需要形成宽频带恒定束宽的波束。采用两种阵元加权方法分析二维圆弧形恒定束宽换能器声纳阵列:球面Legendre函数加权方法和柱面Legendre函数加权方法。分别对球面阵、柱面阵和平面阵这三种几何结构的声纳阵列进行分析,并且计算波束宽度和波束方向。结果表明,在宽频带范围内,除了柱面Legendre函数加权的球面阵之外,其余Legendre函数加权的声纳阵列均能利用简单的、不随频率变化的阵元权重和阵元延时,形成恒定束宽的波束,并且具有较小的旁瓣,此外波束方向与预设方向也较为一致。相对于其他恒定束宽波束形成方法,Legendre函数加权方法能利用较低的计算复杂度来实现良好的宽频带恒定束宽的波束特性。

A broadband constant-beamwidth beamforming method for sonar arrays using Legendre-function shading

In order to process the hydroacoustic signals, broadband constant-beamwidth beamforming method is usually required for the sonar arrays. The algorithm of the Constant Beamwidth Transducer (CBT) arrays is extended to the two-dimensional sonar arrays, and two element weighting methods are used: the spherical Legendre-function shading method and the cylindrical Legendre-function shading method. Three different arrays using the above methods are analyzed respectively, including the spherical array, the cylindrical array, and the planar array. The beamwidth and the beam direction are also calculated. The results indicate that the Legendre-function shaded sonars arrays achieve constant-beamwidth mainlobe, small sidelobes, and desired beam direction in broadband using simple and frequency-independent element weightings and delays, except for the cylindrically-Legendre-function-shaded spherical array. Compared with other constant-beamwidth beamforming methods, the Legendre-function shading method achieves good beam properties with low computational complexity.