A Passive Positioning Method Using Waveguide Invariant

Waveguide invariant is a scalar for characterizing the distance-frequency interference stripes, which is formed by the acoustic field due to mutual interference between different normal wave modes. Target can be passively positioned by the slope of the interference stripes and the frequency based on the definition of . In this paper, a method for calculating the slope of the interference stripes is presented by taking advantage of Sobel sharpening operator to detect pattern edge. First, the pattern of the interference stripes is divided into smaller parts to keep the slope of stripes in each part approximately constant. Then, the Sobel edge detection method is employed to select the intermediate value and calculate the slope in the frequency range of the smaller part, further to obtain estimation value of distance by using the formula of . Finally, the same on a different frequency range smaller pattern estimated value to the average to a more accurate estimation can be obtained by integrating the distance estimations of all smaller parts. Passive positioning of target can be realized by calculating the slope of interference stripes. Simulation result shows that the proposed method possesses a good performance in distance estimation, and the maximum relative error of target distance estima-tion is smaller than 10%. Lake trial indicates that the maximum error of its target distance estimation is smaller than 25 m.