简介：Responseofadaptivematchedfilter,alsocalledadaptivecorrelator,tomultipathchannelisdiscussedinthispaper.Ithasbeenprovedthatthenewtypeprocessorcanbettermatchwithmultipathchan-nel.Theresultsofexperimentcarriedoutonlakeandinlaboratoryarepresented.Itshowsthattheprocessorhasgooddetectingperformanceintimedomain.

简介：这份报纸为盲目评价建议了一个方法在水下在由使用的浅水环境的隧道在一个单个水中听音器或从单个beam.First收到了数据，收到的信号借助于信号依赖者TF(时间频率)分发被用于来源信号重建，与即时频率评价和TF倒置联合。然后，浅水的隧道评价被收到的信号和估计的来源信号的使用经由WRELAX技术完成。最后，数字模拟的结果和从在华南海试用拿的真实数据的试验性的测试证明了令人满意。建议方法是有用的为，这被显示出在水下隧道评价。

简介：Tostudythepossibilityofdetectingthecrossingchannelbyusingatraditionalloggingtool,acousticfieldgeneratedbyamonopolesourceinacasedwellwithacrossingchannelofvariousanglesissimulatedby2.5-DFiniteDifferenceMethod(FDM).Snapshotsofnormalstressandsynthetictime-domainwaveformsaredisplayed.Thetwo-dimensionalspectruminwave-numberandfrequencydomainsisalsocalculated,wheretheinfluenceofthechannelisclearerthanthatinthewaveforms.Numericalstudydemonstratedthatacrossingchannelcanbedetectedandsizedifitsangleisgreaterthan30degree,andlargerspacingandlowerfrequencysourcearefavorabletodetectandsizethecrossingchannel.

简介：Noncoherentunderwateracousticcommunicationchannelinadverseconditionsismodeledasaphase-randomRayleighfadingchannel,anditscapacitycurveisderived.Toapproachthechannelcapacitycurve,theconcatenatedcodeofthenonbinaryLDPCcodeandtheconstantweightcodeisproposedfornoncoherentcommunicationwhichcanlatebeiterativelydecodedintheprobabilitydomain.Withoutinformationofchannelamplitudeorphaseinthereceiver,statisticparametersoftherespectivesignalandnoisebinswereestimatedbasedonthemomentestimationmethod,theposteriorprobabilitiesoftheconstantweightcodewordswerefurthercalculated,andthenonbinaryLDPCcodewasdecodedwiththenonbinaryfactorgraphalgorithm.Itisverifiedbysimulationsthatbyutilizingtheproposedconcatenatedcodeanditsprocessingalgorithm,gaptochannelcapacitycurveisreducedby3dBwhencomparedtotheexistingmethod.Underwatercommunicationexperimentswerecarriedoutinbothdeepocean(verticalcommunication,5km)andshallowlake(horizontalcommunication,near3km,delayspreadlargerthan50ms),inwhichthesignalfrequencybandwas6kHzto10kHz,andthedatatransmissionrateWas357bps.Theproposedschemecanworkproperlyinbothexperimentswithasignal-to-noiseratiothresholdof2dB.TheperformanceoftheproposedalgorithmWaswellverifiedbytheexperiments.

简介：Theoreticalandexperimentalresearchoflowfrequencypulsecompressionandchannelmatchinshallowwatersoundchannelwerecarriedoutbasedon2000-WinterYellowSeaexperiment.Usingpulsecompressionmethod,signalswithhighsignaltonoiseratio(SNR)werereceivedoverrangeof110kilometersintheexperiment.TheSNRgainintheprocessisconsistentwiththetheoreticalprediction.Theexperimentalmeasurementindicatedthatthechannelishighlycoherentoveralengthof500s.ChannelmatchmethodwasusedtocompensatethedegradationofpulsecompressionSNRcausedbythemulti-pathpropagation.AndtheSNRgaininthechannelmatchprocesscanbetheoreticallypredicted.ExperimentalresultsshowthatlowfrequencypulsecompressionandchannelmatchmethodcanbeusedinshallowwatersoundchanneltoimprovetheSNR.

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简介：Inthispaper,theoceanacousticchannelisconsideredasatime-variantchannel.Inordertoanalysetheconjointtime-shift-fre-quency-delaydistributionorthefadingandspreadstatisticalcharacteristicsofthechannel.TheTDWVS(TwoDimensionalWigner-VilleSpectrum)ofthetime-variantchannelisdefined.TherelationbetweentheWVS(Wigner-VilleSpectrum)oftheinputandtheoutputofthechannelisdiscussedandsomeexamplesforthespecificchannelareshown.Finally,theapplicationsonthedetectionofsignalsinnoiseusingtheWVSandTDWVSaregivenandtheadvantageisobvious,whenthedetectedsignalislinearfrequency-modulationsignal.