Goldhahn Ryan, Hickman Granger, Krolik Jeffrey
Duke University, Durham, North Carolina 27708-0291, USA.
J Acoust Soc Am. 2008 Nov;124(5):2841-51. doi: 10.1121/1.2980519.
Reverberation often limits the performance of active sonar systems. In particular, backscatter off of a rough ocean floor can obscure target returns and/or large bottom scatterers can be easily confused with water column targets of interest. Conventional active sonar detection involves constant false alarm rate (CFAR) normalization of the reverberation return which does not account for the frequency-selective fading caused by multipath propagation. This paper presents an alternative to conventional reverberation estimation motivated by striations observed in time-frequency analysis of active sonar data. A mathematical model for these reverberation striations is derived using waveguide invariant theory. This model is then used to motivate waveguide invariant reverberation estimation which involves averaging the time-frequency spectrum along these striations. An evaluation of this reverberation estimate using real Mediterranean data is given and its use in a generalized likelihood ratio test based CFAR detector is demonstrated. CFAR detection using waveguide invariant reverberation estimates is shown to outperform conventional cell-averaged and frequency-invariant CFAR detection methods in shallow water environments producing strong reverberation returns which exhibit the described striations.
混响常常限制主动声纳系统的性能。特别是，粗糙海底的反向散射会使目标回波模糊不清，和/或大型海底散射体可能容易与感兴趣的水柱目标混淆。传统的主动声纳检测涉及对混响回波进行恒虚警率（CFAR）归一化，这并未考虑多径传播引起的频率选择性衰落。本文提出了一种不同于传统混响估计的方法，其灵感来自于在主动声纳数据的时频分析中观察到的条纹。利用波导不变性理论推导了这些混响条纹的数学模型。然后使用该模型推动波导不变混响估计，这涉及沿这些条纹对时频谱进行平均。给出了使用真实地中海数据对这种混响估计的评估，并展示了其在基于广义似然比检验的CFAR检测器中的应用。结果表明，在产生具有所述条纹的强混响回波的浅水环境中，使用波导不变混响估计的CFAR检测优于传统的单元平均和频率不变CFAR检测方法。
