利用波导不变量的浅海负跃层声源深度判别

在夏季负跃层水文条件下,声源激发的声场同时存在折射类和反射类简正波,导致通过分离简正波进行深度判别的方法性能下降甚至失效·提出了一种利用波导不变量判别声源深度的方法。当接收器位于负跃层以下时,水面声源和水下声源的波导不变量数值不同。在本文的仿真条件下,水面声源波导不变量约等于1,当声源位于负跃层以下时,波导不变量大于1.利用频域warping变换从干涉结构中提取与实际距离成线性关系的时域脉冲,可以在未知声源距离的情况下,从声场干涉结构中获得声源激发声场的波导不变量,从而在夏季负跃层水文条件下进行声源深度判别。方法无须声源与接收器存在最近经过距离,可适用于单水听器或水平阵波束形成后输出的LOFAR谱.仿真结果证明,方法可以提取水面目标和水下目标的时延轨迹并计算干涉条纹的波导不变量。最后,对海试实验数据进行分析处理,从水面声源的干涉条纹中提取波导不变量,证明了方法的有效性。 

Source depth discrimination in negative thermocline using waveguide invariant

Aiming at the topic of source depth discrimination of negative thermocline in shallow water,an approach which is used to extract the waveguide invariant from the interference pattern by warping transform is present.On condition that the receiver is below the thermocline,the waveguide invariant of the surface source is approximate equal to 1 and the waveguide invariant of the underwater source is larger than 1.The interference pattern is warped to obtain its relation items of modes.A time delay pulse which is proportional to the real range is extracted,so the waveguide invariant of the interference pattern can be calculated without knowing the range.This method does not need the nearest passing distance and can be used on a single hydrophone or the LOFAR spectrum which is the output of beam forming by a horizontal array.The formula derivation and simulation results provide that the time delay pulse of the relation items aroused by sources in different depths are proportional to the real range.The waveguide invariant can be extracted and the depth of the source can be identified.At last,the waveguide invariant of a ship is extracted.The experimental results prove its effectiveness.