Radio frequency interference in radioastronomy

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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,theireectonthesesensitivemeasurementsandthemethodstomitigatetheireec

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