Research On Source Localization By Matched Field Processing Based On Ray Theory

Reeenly, with the develOPment of underwater acouStic technology, matchedfield processing tecboques have been widely used in source localiZation andbecome one of the most boortan methods of acoustical signal processing. Whleocean environmeni is ven' complex. there are many difficulties in solving three-dimensionaI sound field, till now we still did not get an efficient method to solvethis problem. Traditional matched field processors such as linear processor.minimal variance processor, matched mode processor and so on are almost basedon the processing of sound pressure, it is well Anown tha sound pressure is atime-vaping qMity. its arnplit'Ude and phase preserve peotation, singlemeasurement or limited measurements couldn't present the real character of soundfield, so it will be more difficult to localize a source by matched field processingor get high accuracy of source localiZaion. The reasons focusing only on raytravel times are' noise tOlerance could be enhanced and the sensitivity to theenvironment model mismatch may be reduced by neglecting amplitudeinformation; phase ambiguity is eliminated by employing the grouP delay ofarriving wave packets; travel times are pseudo-linear functions of sound speedprofiles of the medium, and the pertUrbation of ray travel time is much smallerthan sound pressure's. Wth the above analysis of ray travel times, a new methodof source localiZation based on ray travel tirne is presented in Ans dissendion.There are tWo ldnds of cost functions in the thesis, the first is based on theray travel time delay of the adjacent hydrophones; the second is directly based oneq travel times. Under these fimctions, mismatch of ocean dePth, receiverlocation and sound sPeed profile have been simulated resPectively. DifferentresultS specify that the first kind of cost function is sensitive to the mismatch ofocean dePth and receiver location, but is insensitive to sound speed profile's%$jaI8x9@t$M&zmismatch and has high accuracy of depth localiZaion; the second kind of costfimction is insensitive to all three kinds of mismatch, but its resolution of depth isvery low ln order to overcome the cost function's sensitivity to mismatch,improvemeDt of the accuracy of time delay estimation and model calculation maybe adopted, when both conditions are reached, the sensitivity wiIl be greatlyreduced and the resolution of range and depth will be imProved at the same time.Finally the above results discussed are verified by source localiZaion usingexperimental data. Results rectify that matched field processing based on raytravel time delay is insensitive to the mismatch of sound speed proflle, althoughthe mismatch of ocean bottom depth and receiver location is bad to matched fieldprocessing, different forms of cost fimctions could decline the sensitivity.After the simulation analysis and experiment data processing, we couldconclude tha the inversion method of ray travel time is feasible to sotircelocaliZaion. Ray tracing is very simple and fast, and has high accuracy. Besidesthat ray theory is helpful to calculate three-dimensional sound field, and theinversion of sound field could be finished quickly enough to realize the detectionof ocean environment in wide area.