Precise bearing and automatic target tracking in digital sonar

I.IntroductionItiswellknownthatthepreciseestimationofDOA(DirectionOfArrival)oftargetisanimportantthesisinpassivesonardesign.TheoptimumestimationaccuracyexpressionforlinearrayispresentedbyLewisalldothersll-3].Basedonthepointofviewoftime-delayestimation,Carteretal.showthattheaccuracyoftime-delayestimationofreceivedsignalbetweentwodifferentchannelscanreachtheoptimumCramer-RaolowboundI4-6].Forthedigitalsonarthebearingbeamdirectionisusuallyequal-spaceddistributedwithino-36o".Inordertofindthep…

Precise bearing and automatic target tracking in digital sonar

Precise bearing and Automatic Target Thacking (ATT) for moving vessels is an important thesis in passsive sonar design. Thaditionally in the analogue sonar, DOA (Direction Of Arrival) of the target is determined by the single beam steerillg directioll, which rotate some kind of compensator to steer the target. The compensator is typically made of many electronic and mechanical components. The bearing accuracy substantially depellds on the accuracy of tapped delay line and many mechanical factors. With the application of digital technique in sonar, the precise bearing and ATT technique have attracted much interests for sonar designer. For a digital sonar the multi-beam system has discrete beam direction, which distributed in space, each beam has its fixed steering direction. It is important to use them to estimate precisely DOA of target and then to track the target automatically when the target is moving. An algorithm, which can precisely estimate the value of DOA of the target, is derived in this paper. The relationship among bearing accuracy and the array aperture, signal frequency band is expressed. The expression of time-delay estimation and bearing accuracy is presented. DOA of the target can be precisely calculated by the parabolic interpolation in the neighbourhood of the main lobe of the directivity function. It is easy to implement ATT technique in real time by DSP chips. The results of system simulation show that the algorithm derived in this paper has very good performance in target tracking.