Abstract
In this paper, a scheme based on the time reversal technique is proposed to improve the detection performance for detecting a cylindrical object bottoming at the seafloor in shallow water. When the time reversal technique is applied to the response of the clutter with the strong time-varying characteristic of shallow water, it is difficult to obtain a high peak response. However, in the case where a cylindrical object is placed on the seafloor because the time-invariant property of the target response is stronger than the time-varying property of the reverberation by the clutters, the time reversal technique can be applied to enhance the target signal. In this paper, it is demonstrated that the peak due to the target that is contacted at the seabed becomes higher when applying the time reversal technique. The performance is investigated by using numerical computation of the probability of detection for various probabilities of false alarm and computer simulation.
Highlights
Detection of objects bottoming at the sea floor in shallow water is a very important problem.It is essential in underwater exploration for protecting the underwater environment, and is a critical technology in the field of military detection.A side scan sonar is mainly applied in conventional methods to obtain images within detection fields, and studies have been performed to recognize cylindrical targets by using image signal processing [1,2,3,4,5]
In order to investigate the effect of the shape parameter α on the probability of detection, the probability of detection is numerically estimated as a function of the normalized target signal power with respect to the scale parameter; that is, S0 = Pt /λ for the probability of false alarm
When seabed clutter exists in the received signal, the scattering signal by the target is buried in the clutter signals, which makes accurate detection difficult
Summary
Detection of objects bottoming at the sea floor in shallow water is a very important problem. The time domain correlation analysis according to distance and frequency shows that the time-varying characteristics of the shallow water channel become stronger as the distance becomes longer and as the frequency increases [26] For this reason, the time reversal technique can achieve good performance even if the scattering environment is complicated. A method is proposed to improve the detection performance using the time reversal technique in the situation where the clutter is mixed in the shallow water. For the scattering waveform of the cylindrical object considered in this work, because the time-varying characteristic of the target response is weaker than that of the reverberation by the clutter, the time reversal technique can increase the peak of the target signal.
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