Broadband Passive Sonar Signal Simulation in Shallow Ocean

Baiju M. Nair; K. P. Arunkumar; Sudha B. Menon

doi:10.14429/dsj.61.89

Baiju M. Nair Naval Physical & Oceanographic Laboratory, Kochi
K. P. Arunkumar Naval Physical & Oceanographic Laboratory, Kochi
Sudha B. Menon Naval Physical & Oceanographic Laboratory, Kochi

Keywords: Sonar signal simulation, shallow ocean, normal mode model, plane-wave model

Abstract

The broadband plane wave model is valid only in the far-field of a point source under free-field propagating conditions. However the acoustics in ocean is characterized by multi-modal acoustic propagation due to its top-bottom limited boundary conditions. The effect of multi-modal field is to alter the source spectrum while the effect of dispersion is to modify the pulse shape. Moreover the use of a plane wave beamformer in a multi-modal field leads to a bias in the bearing estimates. These effects are highly dependant on the environment parameters and have important ramifications for target localization and classification in an ocean waveguide. We propose a more realistic simulator which essentially models these effects and therefore serves to provide test signals for first hand verification of signal processing algorithms to be developed for such scenarios. This model is to be understood as a better model than the naïve plane wave model which is entirely oblivious of even the gross features such as wave propagation in an oceanic waveguide. The channel parameter so estimated from the present simulation can be convolved with the radiated noise spectra of the source to generate the passive sonar signal.

Defence Science Journal, 2011, 61(4), pp.370-376, DOI:http://dx.doi.org/10.14429/dsj.61.89

Author Biographies

Baiju M. Nair, Naval Physical & Oceanographic Laboratory, Kochi

Mr Baiju M. Nair completed his MSc(Physics) from Loyola College, Chennai,in 2001. He has worked in the field of electromagnetic wave propagation in microwaves devices and vacuum systems at MTRDC, Bengaluru. Subsequently he has been working as Scientist at Naval Physical and Oceanographic Laboratory(NPOL), Kochi. His main areas of research include underwater sound propagation, underwater acoustic scattering from object and boundaries, environmentally adaptive algorithms, modelling, and acoustic data analysis.

K. P. Arunkumar, Naval Physical & Oceanographic Laboratory, Kochi

Mr K.P. Arunkumar obtained his BTech. (Elect. & Electro. Engg.) from Government Engineering College, Thrissur, in 1998 and ME in Signal Processing from Indian Institute of Science, Bengaluru, in 2007. Currently, he is scientist at Naval Physical Oceanographic Laboratory, Cochin, working in Sonar Signal Processing, since April 2000. His research interests include array signal processing, image and multidimensional signal processing, detection and estimation theory, time frequency analysis, and adaptive signal processing.

Sudha B. Menon, Naval Physical & Oceanographic Laboratory, Kochi

Mrs Sudha B. Menon received BTech (Elect. & Electro. Engg.) from Government Engineering College, Thrissur, in 1992 and MTech (Comp. & Info. Sc) from Cochin University of Science and Technology, Cochin, in 1994. She is currently working as a scientist at Naval Physical and
Oceanographic Laboratory, Cochin, in the area of sonar signal processing. Her research interests include array signal processing, adaptive algorithms, and underwater acoustics.