浅海负跃层条件下的warping变换宽带无源测距方法

夏季浅海波导中常常存在强烈的负跃层,研究warping变换无源测距在这种水文条件下的使用方法具有重要的应用价值。对于上发上收、上发下收和跃层强度较小时下发下收的情况,海面海底反射类简正波对声场起主要作用,可以对接收信号的自相关函数进行时域warping变换,利用特征频率匹配的方法进行无源测距。而对于跃层强度较大时下发下收的情况,水体折射-海底反射类简正波对声场起主要贡献,可以对接收信号的自相关函数进行频域β-warping变换进行无源测距。并且能在事先获得粗略的水体声速剖面参数的情况下,通过设置一个已知距离的引导声源,那么即使估计得到的波导不变量存在一定误差,实际测距结果也可以与真实距离符合得较好。利用warping变换对一次夏季浅海实验接收到的目标发出的宽带信号进行无源测距,估计距离与真实距离符合较好,相对误差在20%以内。 

Passive source range estimation based on warping transform in shallow water with a thermocline

Passive source range estimation based on warping transform in shallow water with a thermocline is studied.When the source is above the thermocline, or both the source and the receiver are below a weak thermocline, the sound field is mainly composed of reflective modes. And passive range estimation could be achieved by using time domain warping transform of the autocorrelation function of the received signal. When both the source and the receiver are below a strong thermocline, the sound field is mainly composed of refractive modes. And frequency domain β-warping transform could be introduced to achieve passive range estimation. What's more, when a guided source existing, the estimated ranges match well with the real ones, as long as the estimated waveguide invariant is within a reasonable range. Finally, passive range estimation based on warping transform is applied to broadband data collected during a summer experiment. The estimated ranges match well with the real ones.