Broadband matched-field processing: coherent and incoherent approaches

C. Soares
S.M. Jesus
SiPLAB-FCT, Universidade do Algarve,
Campus de Gambelas,
PT-8005-139 Faro, Portugal.

Comments: download pdf file.
Ref.: J. Acoust. Soc. Am., vol. 113(5),  pp. 2587-2598, 2003.

Matched-field based methods always involve the comparison of a physical model output and the actual data. The method of comparison and the nature of the data varies according to the problem at hand, but the result becomes always largely conditioned by the accurateness of the physical model and the amount of data available. The usage of broadband methods has become a widely used approach to increase the amount of data and to stabilize the estimation process. Due to the difficulties to accurately predict the phase of the acoustic field the problem whether the information should be coherently or incoherently combined across frequency has been an open debate in the last years. This paper provides a data consistent model for the observed signal, formed by a deterministic channel structure multiplied by a perturbation random factor plus noise. The cross-frequency channel structure and the correlation of the perturbation random factor are shown to be the main causes of processor performance degradation. Different Bartlett processors, such as the incoherent processor [Baggeroer88], the coherent normalized processor [Michalopoulou96] and the matched-phase processor [Orris00], are analysed and compared in light of the optimum processor performance. Finnaly a cross-frequency incoherent processor is proposed that is analytically shown to have the same performance as the matched-phase processor with however an extremely low computation complexity.