利用LOFAR谱图的二维傅里叶变换脊计算波导不变量
doi: 10.3724/SP.J.1146.2007.00800
Calculating the Waveguide Invariant by the 2-D Fourier Transform Ridges of Lofargram Image
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摘要: 该文提出了利用被动声纳信号LOFAR谱图的二维傅里叶变换计算波导不变量的方法。在用简正波方法分析了两种典型波导的波导不变量分布情况的基础上，推导了利用LOFAR谱图二维傅里叶变换脊计算波导不变量的公式。运用该公式仿真计算了Pekeris波导和具有负跃层的浅海波导声场中声源深度从10m变化到90m时的波导不变量值，经过与南海试验数据的计算对比，两者计算结果相符。与简正波方法相比，该方法不需要精确了解海洋环境参数，同时避免了复杂的微分方程求解运算，更适合于信号的实时处理。Abstract: A new method is presented in this paper for the calculation of waveguide invariant () with passive sonar lofargram image. The distributions of in two waveguides are studied with normal mode model. Concise formula for calculating is then derived by finding the 2-D Fourier transforms ridges of the lofargrams. The algorithm is exercised for a Pekeris waveguide and a simulated shallow water waveguide containing thermoclines with source depth varying from 10m to 90m. It then is applied to a lofargram collected during an experiment at the South China Sea. The result of experimental data is well matched to the simulations. The approach differs from normal mode algorithm by virtue of its avoidance of potentially prohibitive computation and accurate estimation of environmental parameters and is more suitable for real-time signal processing.
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