Underwater Broadband Target Localization using the Interference Pattern of Spectrogram Estimated by Three Sensors

In this paper, we propose a moving target localization algorithm using an acoustic spectrogram. A time- versus-frequency spectrogram provides information of trajectory of the moving target in the underwater. For a source at sufficiently long range from a receiver, broadband striation pattern seen in spectrogram represents the mutual interference between modes which reflected by surface and bottom. The slope of the maximum intensity striation is influenced by waveguide invariant parameter beta and distance between target and sensor. When more than two sensors are applied to measure the moving ship-radited noise, the slope of the maximum intensity striation and frequency are variable depend on distance between target and receiver. We assumed two sensors to fixed point then form a circle of apollonios which set of all points whose distances from two fixed points are in a constant ratio. In case of three sensors are applied, two circle form an intersection point so a coordinate of this point can be estimated as a position of target. To evaluates a capability of the proposed localization algorithm, simulation is performed using acoustic propagation code.