| The passive sonar makes use of the target noise or signal received by the transducer array to estimate the target distance and azimuth. Its advantage is that sonar itself doesn't providing signal. Noise or signal radiated from target is used to detect the target distance and azimuth. Three elements array is the commonly used technology in passive localization. High precise delay time estimation is the key technology in order to take care of precise positioning.Passive localization of underwater noise target with distance of 1 kilometer is the main research in this thesis. The principle of passive localization with three elements array is introduced. The precise formula and approximately formula of passive ranging and direction finding are derived and application of two formulas is given. Errors impacting precision of ranging and direction finding are analyzed, such as random error, array installation error and marine rocking error and so on. The principle of time delay estimation is presented and cross correlation method is used to acquire time delay of two-channel signals. Effect of time delay beamforming and slide window correlating in correlation peaks detection is studied. Broad band noise radiated from target is divided into four narrow bands to acquire precise time delay estimation. 4-point interpolation and bands synthesizing method is used to improve the precision of time delay estimation. Finally, parameter-estimation based on LMS is used to filter estimated value.Passive localization posed in this thesis is simulated in matlab, and the simulating results are given. Finally, noise data radiated from marine is analyzed using the simulating method. From the analyzed results of simulating and the experiment data, this method has good effect of measuring distance and direction. The results validate the passive ranging method investigated in this thesis.
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