Bi-hydrophone LOFAR (low frequency analysis record) spectrogram analysis-based target depth distinguishing method

Abstract

The present invention provides a bi-hydrophone LOFAR (low frequency analysis record) spectrogram analysis-based target depth distinguishing method. The method includes the following steps that: 1) based on sound field data received by two hydrophones which are located above and below a spring layer respectively, LOFAR spectrograms of receiving sound intensities at the two depths are calculated; 2) a rectangular region is selected from the two obtained LOFAR spectrograms respectively, and the coordinate ranges of the two rectangular regions are the same, and two-dimensional Fourier transformation is performed on the rectangular regions, and then the integral values of the sound intensities are calculated in a transform domain according to an angle traversal mode, so that the probability density functions of interference fringe angles can be obtained; 3) the expected values of the two probability density functions are calculated, so that the difference of the two expected values can be calculated; a depth distinguishing judgment threshold angle value is set; and 4) the depth of a target is judged according to the result of the comparison of the difference of angle expected values and a judgment threshold. With the method of the invention of the invention adopted, priori information of marine environment is not required, the amount of calculation is small, and the depth of a target in a shallow sea environment with a spring layer can be distinguished.

Description

technical field [0001] The invention relates to a target depth resolution method. Background technique [0002] Surface sound sources such as ships will bring false alarms to underwater target monitoring equipment, and the effective distinction between surface sound sources and underwater targets is one of the key capabilities of sonar equipment. [0003] The existing object depth resolution methods are mainly based on the matching field processing method and some more robust extension methods, such as modal scintillation and modal filtering [Baggeroer (1988), Premus (1999, 2004)]. Based on the determined propagation model, the matching field processing method cross-correlates the actual measured sound field data with the copy field calculated by the propagation model to obtain a performance surface and estimate the distance and depth of the target. Most localization methods based on matched field processing use vertical or horizontal arrays to obtain sufficient spatial inf...

AI Technical Summary

Problems solved by technology

In practical applications, these two types of methods mainly have two shortcomings. One is that the hydrophone array system used is relatively complex, the cost is high, and it is difficult to deploy at sea. For example, the vertical array will be inclined due to the influence of ocean currents. And the amount of inclination is generall

Images