简介：ThesynchrodoublepulsesignalmodeisfreuqentlyusedinShortBaseLine(SBL)underwaterpositioningsystemsoastoobtaintheinforma-tionofbothdistanceanddepthofatargetsimultaneously.Howerer,thissignalmodealsobringsaboutrangingindistinctnessresultinginashorterpositioningdistancemuchlessthanthatlimitedbytheperiodofthesynchrosignal.Thispaperpresentsahardwaredistance-gatedataacquiringscheme.Itputstheoriginaldatasenttothecomputerinorderof"directfirstpulse—depthinformationpulse(orfirstpulsereflectedbywatersurface)…"toguaranteetheeffectivepositioningdistanceofthesystem.Ithastheadvan-tageofreducingtheprocessingtimeofthecomputerthusensuringtherealtimefunctioningofthesystem.Afigureoftheorbitofanunderwatermovingtargetmeasuredinpracticeisattachedtotheendofthepaper.