简介:ThisworkpresentsacomputationalmatrixframeworkintermsoftensorsignalalgebrafortheformulationofdiscretechirpFouriertransformalgorithms.Thesealgorithmsareusedinthisworktoestimatethepointtargetfunctions(impulseresponsefunctions)ofmultiple-inputmultiple-output(MIMO)syntheticapertureradar(SAR)systems.Thisestimationtechniqueisbeingstudiedasanalternativetotheestimationofpointtargetfunctionsusingthediscretecross-ambiguityfunctionforcertaintypesofenvironmentalsurveillanceapplications.Thetensorsignalalgebraispresentedasamathematicsenvironmentcomposedofsignalspaces,finitedimensionallinearoperators,andspecialmatriceswherealgebraicmethodsareusedtogeneratethesesignaltransformsascomputationalestimators.Also,thetensorsignalalgebracontributestoanalysis,design,andimplementationofparallelalgorithms.AninstantiationoftheframeworkwasperformedbyusingtheMATLABParallelComputingToolbox,whereallthealgorithmspresentedinthispaperwereimplemented.
简介:在里面常规多乐队直角的频率部门multiplexing极端宽带(MB-OFDMUWB)接收装置,快Fourier变换(快速傅里叶变换)算法被昂贵、消费力量的数字信号处理器(DSP)认识到芯片。在这篇文章,更低的力量,更低的费用,和更低的复杂性即时模拟表面声学的波浪(锯)啁啾Fouriertransform设备被用来代替DSP部分。MB-OFDMUWB接收装置基于M-C-MSAWchirpFourier变换被介绍,并且从输入信号的信号转变的步也被描绘。当在环境由IEEE802.15SG3a建议了的隧道使用了时,模拟结果证明建议接收装置与充分数字的接收装置相比提供类似的位错误性能。
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简介:Wepresentthenumericalresultsfortheoptimizationofthepump-to-idlerconversionefficienciesofnanosecondidlerwavelengthtunablecascadedopticalparametricoscillators(OPO)indifferentwavelengthtuningranges,wheretheprimarysignalsfromtheOPOprocessarerecycledtoenhancethepump-to-idlerconversionefficienciesviathesimultaneousdifferencefrequencygeneration(DFG)processbymonolithicaperiodicallypoled,magnesiumoxidedopedlithiumniobate(APMgLN)crystals.TheAPMgLNcrystalsaredesignedwithdifferentchirpparametersfortheDFGprocesstobroadentheirthermalacceptancebandwidthstodifferentextents.TheidlerwavelengthtuningofthecascadedOPOisrealizedbychangingthetemperatureofthedesignedAPMgLNcrystalandthecascadedoscillationisachievedinasinglepumppasssinglyresonantlinearcavity.Thepump-to-idlerconversionefficiencieswithrespecttothepumppulsedurationandratioofOPOcoefficienttoDFGcoefficientarecalculatedbynumericallysolvingthecoupledwaveequations.TheoptimalworkingconditionsofthetunablecascadedOPOspumpedbypulseswithenergiesof350μJand700μJarecomparedtoobtainthegeneralrulesofoptimization.ItisconcludedthattheoptimizationbecomestheinterplaybetweentheratioofOPOcoefficienttoDFGcoefficientandthepumppulsedurationwhentheidlerwavelengthtuningrangeandthepumppulseenergyarefixed.Besides,higherpumppulseenergyisbeneficialforreachinghigheroptimalpump-to-idlerconversionefficiencyaslongastheAPMgLNcrystalisoptimizedaccordingtothispumpcondition.Tothebestofourknowledge,thisisthefirstnumericalanalysisofidlerwavelengthtunablecascadedOPOsbasedonchirp-assistedAPMgLNcrystals.
简介:目的:采用chirp信号作为声刺激进行听性稳态反应(auditorysteady-stateresponse,ASSR)测试,观察chirp-ASSR反应阈值与纯音听阈阈值的相关性,探讨chirp-ASSR客观听力检测在儿童临床听力评估中的价值。方法选取2012年6月至2013年2月中山大学附属第六医院听力中心检测的儿童共40例(共74耳)作为研究对象,在0.5kHz、1.0kHz、2.0kHz和4.0kHz处进行chirp-ASSR和纯音听阈测试,并对结果进行统计学分析。结果40例接受测试的儿童年龄4-13岁,平均年龄7.7岁。纳入研究的74耳包括男48耳,女26耳;右34耳,左40耳;正常听力59耳,听力损失轻度4耳、中度6耳、重度5耳。0.5-4kHz频率chirp-ASSR反应阈与纯音听阈的相关系数r分别为0.812、0.884、0.842、0.892;chirp-ASSR反应阈经过校正后所得的各频率预估听阈与纯音听阈值更加接近。结论chirp-ASSR作为一种具有频率特异性的客观测听技术,能够较好的反映儿童真实的听力水平。