平頂光束在大氣湍流中傳輸特性及通信信道BER研究.pdf

1、西安電子科技大學碩士學位論文平頂光束在大氣湍流中傳輸特性及通信信道BER研究姓名：亢小寧申請學位級別：碩士專業(yè)：無線電物理指導教師：楊瑞科201201AbstractAbstractAtmosphericlasercommunicationsystemsarebecomingincreasinglypopularbecauseoftheirmanyadvantagesHowevertheperformanceofatmosphericl

2、asercommunicationsystemsisaffectedbyatmosphericturbulenceInordertoensurethestabilityofcommunicationsystem，itissignificanttoresearchtheinfluenceofatmosphericturbulenceonatmosphericlasercommunicationsystemsAtmosphericturbu

3、lencehasasignificantimpactonthequalityofalaserbeampropagatingthroughtheatmospheric，whichCanseverelyimpairatmosphericlasercommunicationsystemsInthispapeLthefundamentalofatmosphericturbulenceisintroduced，theformulaforcalcu

4、latingtheintensitydistributions，beamspreading，powerinbucket(PIB)andspectralcharacteristicsateanalyzedinatmosphericturbulencefromweaktostrongTheeffectsofthebeamorderthespatialcoherence，andtheturbulentparameterontheintensi

5、tydistributions，beamspreading，spectralcharacteristicsandPIBhavebeendiscussedindetailUsingfiattoppedbeamsaslightSOurCeanddifferentmodulations，theinfluenceofthescintillationandbeamspreadingonthebiterrorrates(BER)inlasercom

6、municationsystemisanalyzedBasedonthecorrectingerrorabilityofRScode，theperformanceofcommunicationsystemiseffectivelyimprovedbyusingRScodeinPPMmodulationschemeTheresultsshowthattheonaxisintensityofpartiallycoherentfiattopp

7、ed(PCFT)beamsdecreaseswithincreasingturbulenceanddecreasingcoherenceofthesource，whereastheonaxisintensityofPCFTbeamsinthefarfielddecreasesslightlywithincreasingbeamorderThespreadingofPCFTbeamsissmallerforbeamswithahigher

8、order，alowercoherencedegreeoftheSOurCeandaweakeratmosphericturbulenceThepowerinbucket(PIB)ofPCFTbeamsbothinturbulentmediaandinfreespacedecreasesbyincreasingbeamorder，decreasingthecorrelationlengthandincreasingturbulenceF

9、urthermore，ifthescalinglawisvalid，thenormalizedspectrumS(co)ofPCFTbeamspropagatingthroughturbulentatmosphereisthesameasthenormalizedsourcespectrumS0忉)砸ssimilarityisvalidforanyarbitraryorderofthefiat—topped“N99Ifthescalin

10、glawisnotvalid，S(to)ofPCFTisdifferentfromSo如)rnleonaxisscintillationindexiseffectivelyreducedandtheBERofatmosphericlasercommunicationsystemsisdecreasedbyusingflattoppedbeamsassourceThus，theinfluenceofatmosphericturbulenc