近场聚焦在大孔径光纤拖曳探测系统中的应用

Application of Near-field Beam-forming in Large-aperture Optical Towed Detection System

大孔径光纤水听器拖曳侦测系统广泛应用的方位估计方法是远场波束形成,该方法假设目标在阵列的远场区域,适用于估计远距离目标的方位。而远近场存在临界距离,大孔径阵列的远近场临界距离较远,实际中会有很多目标处于大孔径阵列的近场。对该类目标进行远场近似处理,获得的方位幅度图会发生畸变,并影响方位估计的精度。针对这类目标,论文通过仿真和实际海上拖曳探测数据对比了近场聚焦与远场波束形成的性能。结果表明,对不能近似为远场的目标,近场聚焦可获得更窄的波束宽度与更强的聚集能量,可有效提高目标测向精度,并实现目标距离的估计。证明了近场聚焦在大孔径光纤水听器拖曳侦测系统中的应用价值。

Far-filed beam-forming usually determine the direction of a long-range target by approximation at the farfield area of the array.It is widely used in the detection system of large-aperture optical towed linear arrays.However,there has a critical distance between far-near-field.A large-aperture array has a larger far-near-field critical distance.Actually,multiple targets are located in near-field for a large-aperture linear array.In these circumstances,if far-field beamforming is still used for approximate processing,it will cause bearing-amplitude distortion which seriously influences the precision of the target direction estimate.For such targets,the performance of near-field focused beam-forming and farfield beam-forming are compared through simulation and towed trials data.The results show that when detecting targets which can＇t be considered to be located in far-field,near-field focused beam-forming can achieve the narrowest beam width and the strongest focused energy.It can also effectively improve the precision of target direction finding and estimate target distance.The value of applying near-field focused beam-forming in the detection system of large-aperture optical towed linear arrays is confirmed.