8467

7848

كارشناسي ارشد

مخابرات سيستم

اصفهان: دانشگاه صنعتي اصفهان، دانشكده برق و كامپيوتر

1392

يازده،[120] ص: مصور،جدول، نمودار

ص.ع.به فارسي و انگليسي

محمد صادق فاضل، مجتبي بهشتي

جواد اخلاقي

7/11/92

محمود مدرش هاشمي، علي محمد دوست حسيني

مهندسي برق و كامپيوتر

ID7848

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

121 Reverberation Suppression in Active Sonar using Space Time Adaptive Processing Javad Ebrahimi j ebrahimi@ec iut ac ir Date of Submission 2013 7 2 Department of Electrical and Computer Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language FarsiSupervisor Mohammad Sadegh Fazel Fazel@cc iut ac ir Mojtaba Beheshti Behesht@cc iut ac irAbstract Extension of applications of sonar from deep water to shallow and very shallow water cause sonardesigners to create special techniques in order to overcome underwater acoustic channel challenges inshallow water In such environments reverberation is dominant limiting effect and is a severe problem foractive sonar because the target echo level may not exceed the reverberation level and so the performance ofactive sonar detector will be degraded The problem becomes more challenging if the sonar platform ismoving producing self induced Doppler spread in reverberation In other hand corresponding Dopplerfrequency of targets with slow relative speeds is low So the target Doppler frequency falls in the region ofreverberation spectrum In these situations conventional techniques such as matched filtering are inefficientleading to the degradation of the detection performance of active sonar therefore special techniques thatprocess signals in both spatial and temporal dimension will be required Such techniques suppressreverberation and improve the detection performance In this thesis space time adaptive processing STAP techniques for detection of slow targets in active sonar with moving platform is studied and simulated Sub optimum techniques introduced to overcome some Limitations of fully adaptive space time processor According to the characteristics of underwater acoustic channel it is obvious that there are majordifferences between propagation of acoustic waves under water and electromagnetic waves in the air Thesedifferences cause severe limitations in using STAP for sonar The final goal of this thesis is to investigatethese limitations and propose a new approach to overcome that Simulation results show that proposedtechnique is useful in real underwater conditions and highly suppress reverberation without conventionalSTAP limitations Keywords STAP Active Sonar Reverberation Detection

محمد صادق فاضل، مجتبي بهشتي

جواد اخلاقي

محمود مدرش هاشمي، علي محمد دوست حسيني