Research On Time Reversal Mirror Passive Localization

This paper focuses on the passive localization techniques based on time reversal mirror (TRM), validates the applicability and feasibility of TRM and corresponding algorithms.This paper mainly concentrates on the following problems:First, basic theory, physical and mathematic models, and corresponding processing methods of passive localization based on TRM are studied according to the reciprocity principle of the sound field and ray theory of sound propagation. The feasibility of TRM technique applying to passive localization is proved in theory. It deduces the formulas of TRM and establishes passive localization models of single sensor, two-sensor-array and multi-sensor-array. The study reveals that the matched degree between simulated and actual sound channel determines the passive localization performances of TRM.Second, the paper verifies the correctness of algorithms and codes, and evaluates the performances of TRM passive localization with simulation data processing. The target location is found at the highest power output of TRM by searching over vertical depth and horizontal range. The simulation results indicate that the localization precision reaches the search step of which the minimum is 2 meters in depth and 5 meters in range. The minimum detectable SNR of single sensor may reach to -8dB, and the more sensors are used in TRM processing, the higher the detection performance. The results also conclude that the array gain of TRM is greater than conventional beamforming based on the hypothesis of plane wave.Third, sea-test data processing of vertical array indicates the potential useful value of TRM. The single sound pressure sensor and single vector hydrophone can localize target, and multi-sensor array may detect target in lower SNR. But, it shows that the localization precision of sea-test data is much lower than that of simulation data, so that it puts forwards the new TRM algorithm which is more tolerant and more robust.Fourth, the time reversal mirror technology can be used in several fields of sonar. TRM may focus energy at target position, which may change the disadvantage of multi-path channel into advantage. The lake test verifies that the active or passive time reversal mirror technology can also be used in active sonar and improves signal to reverberation ratio. It also can be used in improving passive ranging performance under the impact of multi-path transmission, which has been studied in theory and tested using simulated data in this paper.Fifth, the paper studies TRM passive localization with vector hydrophone. The oceanic acoustic signal includes sound press signal and vibration signal. The detection performance of single vector hydrophone TRM is as high as that of two sound press sensors, however, its computation is as twice heavy as single sound press sensor. Single vector hydrophone can carry out spatial three-dimension localization.As a newly bora technique, domestic researches on the passive localization by TRM are still at their initial stages. The author hopes this paper will be helpful to the promotion of further studies on the correlative techniques and their applications on sonar and generalizations.