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GPS Antennas - u-blox · PDF fileGPS Antennas locate, communicate ... Application Note . Abstract . Overview of important antenna and interference issues to be ... 5.4 GSM Applications

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  • GPS Antennas

    locate,c

    ommun

    icate,accelerate

    RF Design Considerations for u-blox GPS Receivers Application Note

    Abstract Overview of important antenna and interference issues to beconsideredwhenintegratingu-bloxGPSreceivers.

    www.u-blox.com

  • GPSAntennas-ApplicationNote

    Document Information

    Title GPSAntennas

    Subtitle RFDesignConsiderationsforu-bloxGPSReceivers

    Document type ApplicationNote

    Document number GPS-X-08014-A1

    Document status Released

    Thisdocumentandtheuseofanyinformationcontainedtherein,issubjecttotheacceptanceoftheu-bloxtermsandconditions.Theycanbedownloadedfromwww.u-blox.com.u-bloxmakesnowarrantiesbasedontheaccuracyorcompletenessofthecontentsofthisdocumentandreservestherighttomakechangestospecificationsandproductdescriptionsatanytimewithoutnotice.u-bloxreservesallrightstothisdocumentandtheinformationcontainedherein.Reproduction,useordisclosuretothirdpartieswithoutexpresspermissionisstrictlyprohibited.Copyright2009,u-bloxAG.

    GPS-X-08014-A1 Page 2 of 40

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  • GPSAntennas-ApplicationNote

    Contents

    Contents..............................................................................................................................3

    1 Introduction..................................................................................................................5

    2 Antenna basics .............................................................................................................5 2.1 Generalconsiderations ......................................................................................................................... 5 2.2 Antennarequirements.......................................................................................................................... 5 2.3 Antennaplacement .............................................................................................................................. 6 2.4 Activeandpassiveantennas ................................................................................................................. 7

    3 Passive antenna types..................................................................................................8 3.1 Patchantenna ...................................................................................................................................... 8 3.2 Helixantenna ....................................................................................................................................... 9 3.3 Monopoleantennas ........................................................................................................................... 10

    3.3.1 Chipantenna .............................................................................................................................. 10 3.3.2 FractalElementAntenna(FEA)..................................................................................................... 13

    3.4 Dipoleantenna................................................................................................................................... 14 3.5 Loopantenna ..................................................................................................................................... 15 3.6 PlanarInvertedFAntenna(PIFA) ......................................................................................................... 15 3.7 HighendGPSantennas ...................................................................................................................... 16

    4 Which antenna is best for my application? ..............................................................17 4.1 Helixorpatch? ................................................................................................................................... 17 4.2 OtherAntennaTypes.......................................................................................................................... 17

    5 Design Considerations ...............................................................................................18 5.1 PatchAntennas .................................................................................................................................. 18

    5.1.1 GroundPlane .............................................................................................................................. 18 5.1.2 Placement ................................................................................................................................... 20 5.1.3 ESDIssues ................................................................................................................................... 20

    5.2 HelixAntennas ................................................................................................................................... 21 5.2.1 GroundPlane .............................................................................................................................. 21 5.2.2 Placement ................................................................................................................................... 21

    5.3 AntennaMatching ............................................................................................................................. 22 5.4 GSMApplications............................................................................................................................... 23

    5.4.1 IsolationBetweenGPSandGSMAntenna................................................................................... 23

    GPS-X-08014-A1 Released Page 3 of 40

  • GPSAntennas-ApplicationNote

    5.5 DualAntennaSystems........................................................................................................................ 23

    6 Interference Issues .....................................................................................................26 6.1 SourcesofNoise................................................................................................................................. 26 6.2 EliminatingDigitalNoiseSources ........................................................................................................ 27

    6.2.1 PowerandGroundPlanes ........................................................................................................... 27 6.2.2 HighSpeedSignalLines............................................................................................................... 28 6.2.3 DecouplingCapacitors ................................................................................................................ 28

    6.3 Shielding ............................................................................................................................................ 30 6.3.1 FeedthroughCapacitors ............................................................................................................. 30 6.3.2 ShieldingSetsofSub-SystemAssembly ....................................................................................... 32

    6.4 IncreasingJammingImmunity............................................................................................................. 33 6.4.1 In-bandjamming......................................................................................................................... 33 6.4.2 Out-bandjamming...................................................................................................................... 33

    7 Performance Tests ......................................................................................................35 7.1 Skyview ............................................................................................................................................. 35 7.2 Statisticview....................................................................................................................................... 35 7.3 SupplyVoltageCheck......................................................................................................................... 36 7.4 SensitivityTest .................................................................................................................................... 36 7.5 StartupTest ........................................................................................................................................ 36

    Appendix ..........................................................................................................................37

    A Example of receiver signal to noise (C/No) performance calculation .....................37

    Related Documents ..........................................................................................................39

    Revision history................................................................................................................39

    Contact..............................................................................................................................40

    GPS-X-08014-A1 Released Page 4 of 40

  • GPSAntennas-ApplicationNote

    1 Introduction AntennasareacriticalpartofanyGPSreceiverdesignandtheirimportancecannotbestatedhighlyenough.

    Eventhebestreceivercannotbringbackwhathasbeenlostduetoapoorantenna,in-bandjamming,orabadRF-boarddesign.GPSsignalsareextremelyweakandpresentuniquedemandsontheantenna.ThechoiceandimplementationoftheantennacanultimatelyplayasignificantroleinGPSperformance.

    ThisdocumentconsiderssomeoftheRFandinterferenceissueswhenimplementingaGPSantenna.

    2 Antenna basics 2.1 General considerations AGPS receiverneeds to receive signals fromasmany satellitesaspossible.Optimalperformancewillnotbeavailableinnarrowstreetsandundergroundparkinglotsorifob