In SONAR(Sound Navigation and Ranging), passive localization of sound sources in range and depth are important issues. It has long been known that multi-modal dispersion in a shallow water waveguide degrades the performance of localization by conventional plane-wave beamforming. This is due to the advent of spurious effects unique to the waveguide environment, such as multiple peaks and beam spreading in the beam output. Attempts, on the other hand, have been made to localize sources in ocean waveguides by exploiting multi-modal interference using methods such as matched field processing(MFP). Apart from being computationally expensive, MFP techniques require accurate knowledge of the wave propagation environment. They are susceptible to large systematic errors from mismatch when adequate environmental information is not available.
The range of a source in a ocean waveguide can sometimes also be estimated by the simpler waveguide invariant method, which employs only incoherent processing of acoustic intensity data as a function of range and bandwidth. It is convenient to apply the concept of waveguide invariant . This has earlier been shown to be useful for explaining interference patterns of broadband signals.
In this thesis we proposed that instantaneous and computationally inexpensive source range estimation method. The proposed method requires neither a priori knowledge of environmental parameters nor multiple modes in the received field. In the proposed method we introduced a concept of the slope of modal interference patterns show that the information of source range. So, we analyzed the single sensor spectrogram then compare the ratio of between source range and positioned sensors. Then we estimated the trajectory of moving source and demonstrated the results of computer simulation.
This thesis is organized as follows : Section 2 overviews the underwater acoustic propagation model. In Section 3, array invariant source range estimating method is described. In Section 4, the proposed method is described, and simulation results are discussed. Finally Section 5 gives conclusions and future works.