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1、DESIGNOFASINGLEFREQUENCYGPSSOFTWARERECEIVERPeterRinderNicolajBertelsenPeterRinderBasicGPSreceiverstructure-Designandimplementation2ProjectGoalDesignandimplementasinglefrequencyGPSsoftwarereceiver3GPSsignalsNavigationdataPseudo-randomnoisesequencesCarrierwave
2、4NavigationdataSatelliteorbitinformation(ephemerides)SatelliteclockinformationSatellitehealthandaccuracySatelliteorbitinformation(almanac)Bit-rateof50bpsRepeatedevery12.5minutes5Pseudo-randomnoisesequencesSpreadingsequences(C/A)Lengthof1023chipsChippingrateo
3、f1.023Mcps1sequencelasts1ms32sequencestoGPSsatellitesSatelliteidentificationSeparatesignalsfromdifferentsatellites6CarrierwaveSignaltransmissionTwofrequencies:L1=1575.42MHzL2=1227.60MHzC/AcodeonL1Bipolarphase-shiftkeying(BPSK)modulation7GPSsignalCarrierwaveN
4、avigationdataCarrieranddata20ms1ms1databit8GPSsignalCarrieranddataResultingsignalPRNcode9ImportanttasksofaGPSreceiverPreparereceivedsignalsforsignalprocessingFindsatellitesvisibletothereceiverForeachsatelliteFindcoarsevaluesforC/Acodephaseandcarrierfrequency
5、FindfinevaluesforC/AcodephaseandcarrierfrequencyKeeptrackoftheC/AcodephaseandcarrierfrequencyastheychangeovertimeObtainnavigationdatabitsDecodenavigationdatabitsCalculatesatellitepositionCalculatepseudorangeCalculateposition10ReceiverchannelReceiverchannelRe
6、ceiverchannelReceiverchannelReceiverchannelReceiverchannelReceiverchannelReceiveroverviewRFfront-endA/DconverterAcquisitionReceiverchannelPositioncalculationPreparereceivedsignalsforsignalprocessing11ReceiverchannelReceiverchannelReceiverchannelReceiverchann
7、elReceiverchannelReceiverchannelReceiverchannelReceiveroverviewRFfront-endA/DconverterAcquisitionReceiverchannelPositioncalculationFindsatellitesvisibletothereceiverFindcoarsevaluesforC/Acodephaseandcarrierfrequencyforeachsatellite12ReceiveroverviewFindfine
8、valueforC/AcodephaseFindfinevalueforcarrierfrequencyKeeptrackoftheC/AcodephaseandcarrierfrequencyastheychangeovertimeCodetrackingCarrierTrackingBitsyn-chronizationDecodenav.dataCalculatesatelli