Study On Space-time Filtering Technology And Its Application In Acoustic Based On An Acoustic Vector Time-reversal Mirror

Ocean is underwater acoustic channel propagate signal from source to receiver. It is important for signal processor to know how to compensate for aberrations caused by inhomogeneities in the propagation medium. Time reversal (TR) is a unique self-adaptive focusing technique developed from phase conjugation using in nonlinear optics and ultrasonic fields. It can avoid imaging aberration of inhomogeneous media in acoustic and realize self-adaptive focusing without the prior knowledge of the media and the transducer. On the other hand, a number of recent studies have demonstrated vector signal process is excel to general acoustic pressure signal process whether in estimator performance of DOA or detector performance of signal. Combined TR with vector signal process and used in passive location is the main content of the thesis.As the first dissertation for Passive Vector Time Reversal (PVTR) technique, overviews of the TR techniques developed at home and abroad and the corresponding application status about vector hydrophone are introduced in the exordium of the thesis.Firstly, the thesis discusses the vector underwater acoustic models. A mathematical model of pressure and particle velocity channel is established by using the theory of ray acoustic. We can demonstrate the conclusion, that Normal Mode models can be approximated by Ray Theory models not only for pressure propagation but also for vector propagation problem, by compare two vector channels established by different models.Active time reversal's refocuses principle and the physical fundamentals of the combined signal processing with acoustic pressure and particle velocity are reviewed in the thesis, on which the passive pressure TR (PPTR) and PVTR are studied based. PVTR's refocuses and passive location principle are proved from the point of view of the theory of ray acoustic. Particularly, PVTR's spatial matchcharacteristic and processing gain are simulated in the paper, which enrich the theoretical basis of PVTR.Whether the technique of PVTR is convenient and robust or not is important for PVTR's application. In the other part of the thesis the algorithm of the PVTR is optimized and degraded performance of PVTR in the presence of data modeling errors are studied. The discussion includes data modeling errors at sea surface, sea bottom, sound channel axis, channel depth, and so on. Results of the simulation show that this kind of PVTR technology not only has higher performance and precision, but also is more robust and stable than conventional time-reversal technology. The location performance of two elements array's TRM is simulated and the focusing properties with different aperture size are studied in the thesis. The results are useful to farther research.Finally, the thesis analyses the data of the trials in lake, and PVTR's locating results are presented. The experiment results are basically consistent with theory results and simulations. The results demonstrate experimentally that PVTR will be a new tool in applied physics.