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1、AALTOUNIVERSITYSCHOOLOFELECTRICALENGINEERINGDepartmentofRadioScienceandEngineeringJukka-PekkaG?oranPorkoRadiofrequencyinterferenceinradioastronomyMaster'sThesissubmittedinpartialful llmentoftherequirementsforthedegreeofMasterofScienceinTechnology.Espoo,May11,2011Supervisor:Pr
2、ofessorMarttiHallikainenInstructor:PetriKirves,M.Sc.AALTOUNIVERSITYSCHOOLABSTRACTOFTHEOFELECTRICALENGINEERINGMASTER'STHESISAuthor:Jukka-PekkaG?oranPorkoNameoftheThesis:RadiofrequencyinterferenceinradioastronomyDate:May11,2011Numberofpages:77Department:DepartmentofRadioScience
3、andEngineeringProfessorship:SpaceTechnologyCode:S-92Supervisor:Prof.MarttiHallikainenInstructor:PetriKirves,M.Sc.Radioastronomyisasub eldofastronomy,whichstudiescelestialobjectswithhighlysensitiveradioreceiversandlargeradiotelescopes.Theseradioastronomicalmeasurementsareperfo
4、rmedinawiderangeoffrequencieswhicharelimitedbytheradiowindowsetbytheattenuationintheEarth'satmosphereandtheman-maderadiofrequencyinterferences(RFI).Thisthesisdiscusses,measuresandidenti estheseman-madeRFIs,theire ectonthesesensitivemeasurementsandthemethodstomitigatetheire ec
5、tsontheobservation.TheexternalradiofrequencyenvironmentintheMets?ahoviRadioObservatorywasmeasuredinthesummerof2010withanantennaandaspectrumanalyserinseveralfrequencybands.Asradioastronomicalmeasurementsarealsovulnerabletotheself-generatedRFIsoftheobservatory,afewcorresponding
6、measurementswereperformedtodeterminethestateoftheinternalradiation.Threeradiore-ceiversweretestedtoestimatetheimpactofexternalandinternalRFIsonradioastronomicalmeasurements.Toidentifytheinterferencesourcesandtheirorigin,aspectrumanalyserwasconnectedtotheintermediatefrequency(
7、IF)portofara-dioreceiver,whiletheradiotelescopewassettosweepthehorizonwithalowelevation.Themostsigni cantexternalRFIsourcesdiscoveredinthisstudyconsistedofDigitalVideoBroadcasts(DVB),GSM,UMTS(3G-network),aviationradiobroad-castsandradioamateuractivity.Thestrongestdetectedinte
8、rnalinterferencesourcescomprisedcellphonesandmicrowaveovens.Thisthes
