兼顾远场和近场性能的便携式三维声纳设计

为了降低三维成像声纳系统的复杂度，并保证系统在整个水下探测范围内具有准确的波束图，提出兼顾远场和近场性能的便携式三维成像声纳设计方法. 该设计采用十字型阵列实现三维声纳成像，相比平面阵，极大降低了硬件复杂度，设备灵活轻便. 针对发射阵列，提出近场条件下的多频发射波束形成算法，根据十字型阵列的景深划分多个发射聚焦区间，并通过菲涅尔近似，配置各聚焦区间的时延参数，保证近场的波束性能. 针对接收阵列，提出优化的CZT (chirp zeta transform) 波束形成算法，可实现远场和近场条件下的快速波束形成，且计算量低于其他波束形成算法. 仿真实验表明,在近场聚焦区间内，该算法的角度分辨率和旁瓣高度变化差异较小，波束图性能稳定. 实际水下实验证实该设计可以在探测场景内获得清晰的水下三维图像.

Design of portable three-dimensional sonar for both far-field and near-field

A design of portable three-dimensional (3D) imaging sonar for both far-field and near-field was proposed, in order to reduce the complexity of 3D imaging sonar system and guarantee the accuracy of beam patterns for the whole underwater scene. The cross array, which could largely simplify the hardware complexity compared to the planar array, was used to achieve 3D sonar imaging and make the system portable. For the transmitting array, a near-field multiple-frequency transmitting algorithm was proposed to guarantee the performance of the beam pattern in the near field. The whole 3D scene was divided into several focal regions according to the depth of field, and the time-delay parameters for each focal region were calculated based on the Fresnel approximation. For the receiving array, an optimized chirp zeta transform beamforming was proposed to implement both far-field and near-field fast beamforming with lower computational requirement than those of other methods. The simulation experiments demonstrated that the angle resolution and the side lobe peak of the proposed algorithm had a relative small variation in the near field focal regions, and the performance of the beam pattern was stable. The real underwater tests verified that the proposed design could generate high quality underwater images within the detection scenes.