u-blox LEA-4R System Integration Manual And Reference Design

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your position is our focus

Abstract

mentscribestheatures dspecificationsofthe

LEA-4R/TIM-4RlowpowerDRGPSmodules.Itguidesthrougha

designandprovidesinformationtogetmaximumGPS

performanceatverylowpowerconsumption.



u-blox AG

Zürcherstrasse68

8800Thalwil

Switzerland

www.u-blox.com



Phone+4117227444

Fax+4117227447

[email protected]



LEA-4R / TIM-4R

System Integration Manual / Reference Design

Manual

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This docu de fe an







your position is our focus

Title LEA-4R/TIM-4R

Subtitle SystemIntegrationManual/ReferenceDesign

Doc Type Manual

Doc Id GPS.G4-MS4-05043

Revision

Index Date Name Status / Comments

InitialVersion TG

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

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign 

GPS.G4-MS4-05043 

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your position is our focus

Preface

TheLEA-4R/TIM-4RSystemIntegrationManualprovidesthenecessaryinformationtosuccessfullydesigninand

configuretheseANTARIS®4-basedGPSreceivers.ThisdocumentspecificallyreferstotheDeadReckoning

technologyavailableintheLEA-4RandTIM-4R.ItdoesnotexplaintheANTARIS®4system.Fordetailed

informationregardingANTARIS®4technology,seetheANTARIS®4 System Integration Manual [5].



Technical Support

Worldwide Web

Ourwebsite(www.u-blox.com)isarichpoolofinformation.Productinformation,technicaldocumentsand

helpfulFAQcanbeaccessed24haday.

By E-mail

Ifyouhavetechnicalproblemsorcannotfindtherequiredinformationintheprovideddocuments,contactthe

nearestoftheTechnicalSupportofficesbyemail.Useourservicepoolemailaddressesratherthananypersonal

emailaddressofourstaff.Thismakessurethatyourrequestisprocessedassoonaspossible.Youwillfindthe

contactdetailsattheendofthedocument.

By Phone

Ifanemailcontactisnottherightchoicetosolveyourproblemordoesnotclearlyansweryourquestions,call

thenearestTechnicalSupportofficeforassistance.Youwillfindthecontactdetailsattheendofthedocument.

Helpful Information when Contacting Technical Support

IfyoucontactTechnicalSupportpleasepreparethefollowinginformation:

• Receivertype(e.g.LEA-4R/TIM-4R)andfirmwareversion(e.g.V4.00)

• Receiverconfiguration,e.g.informofau-centerconfigurationfile.

• Cleardescriptionofyourquestionortheproblemtogetherwithu-centerlogfile.

• Ashortdescriptionofyourapplication

• Yourcompletecontactdetails



LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign Content

GPS.G4-MS4-05043  Page 3

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your position is our focus

Contents

1Dead Reckoning Fundamentals...................................................................................7

1.1DeadReckoningenabledGPS(DR)..............................................................................7

1.2DeadReckoningPrinciple............................................................................................7

1.3DeadReckoningPerformance .....................................................................................8

2Design-In.....................................................................................................................10

2.1SchematicDesign-InChecklistforLEA-4R/TIM-4R .....................................................10

2.2TIM-4R/LEA-4RDesign ..............................................................................................11

2.2.1Forward/BackwardIndication............................................................................11

2.2.2Odometer/Speedpulses.....................................................................................11

2.2.3PowerSupplyforGyroscope,TemperatureSensorandA/DConverter.................11

2.2.4SPIInterfaceforGyroscopeandTemperatureSensor ..........................................12

2.3Pinouttables ............................................................................................................13

2.4LayoutDesign-InChecklistforANTARIS®4.................................................................14

2.5Layout ......................................................................................................................14

3Receiver Description...................................................................................................15

3.1DeadReckoningenabledGPSmodule(DRmodule)...................................................15

3.1.1Architecture .......................................................................................................15

3.1.2InputSignals/Sensors.........................................................................................17

3.1.3DRspecificParameters .......................................................................................20

3.1.4DRCalibration....................................................................................................21

3.1.5StorageofParameters ........................................................................................23

3.1.6StaticPosition.....................................................................................................24

3.2PowerSavingModes ................................................................................................24

3.3AntennaandAntennaSupervisor .............................................................................24

3.3.1OpenCircuitDetect............................................................................................24

4Navigation ..................................................................................................................25

4.1.1Overview............................................................................................................25

4.1.2NavigationUpdateRate......................................................................................25

4.1.3DynamicPlatformModel ....................................................................................26

4.1.4StaticHoldMode ...............................................................................................26

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign Content

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4.1.5DegradedNavigation..........................................................................................26

4.1.6AlmanacNavigation ...........................................................................................26

4.1.7NavigationInputFilters.......................................................................................27

4.1.8NavigationOutputFilters....................................................................................28

4.1.9PositionQualityIndicators ..................................................................................28

4.1.10DGPS(DifferentialGPS) ......................................................................................31

4.1.11SBAS(SatelliteBasedAugmentationSystems).....................................................31

4.1.12RAIM(ReceiverAutonomousIntegrityMonitoring)..............................................31

5Product Testing...........................................................................................................32

5.1u-bloxIn-SeriesProductionTest ................................................................................32

5.2TestParametersforOEMManufacturer ....................................................................32

5.3SystemSensitivityTest ..............................................................................................33

5.3.1GuidelinesforSensitivityTests ............................................................................33

5.3.2‘Go/Nogo’testsforintegrateddevices ...............................................................33

5.4TestingofLEA-4R/TIM-4RDesigns ............................................................................34

5.4.1DirectionSignal ..................................................................................................34

5.4.2SpeedpulseSignal ..............................................................................................34

5.4.3Gyroscope(Rate)Input .......................................................................................34

5.4.4TemperatureSensor ...........................................................................................34

5.4.5EraseCalibration ................................................................................................34

6PC Support Tools ........................................................................................................35

AMigration from TIM-LR to TIM-4R .............................................................................36

A.1MigrationfromTIM-LRtoTIM-4Rpinout .................................................................37

BDefault Settings..........................................................................................................38

B.1Hardware .................................................................................................................38

B.2Navigation................................................................................................................38

B.3PowerSavingModes ................................................................................................39

B.4CommunicationsInterface ........................................................................................40

B.5Messages(UBX–CFG–MSG) ..................................................................................40

B.6Messages(UBX–CFG–INF) .....................................................................................41

B.7TimingSettings.........................................................................................................42

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign Content

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your position is our focus

CReference Design for TIM-4R.....................................................................................42

DMechanical Data.........................................................................................................43

D.1Dimensions...............................................................................................................43

D.2Specification.............................................................................................................44

Glossary ............................................................................................................................45

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LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign Content

GPS.G4-MS4-05043  Page 6

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your position is our focus

1 Dead Reckoning Fundamentals

1.1 Dead Reckoning enabled GPS (DR)

DeadReckoningisafeaturetomakeGPSmoreaccurateandreliableinurbancanyonenvironmentsandduring

GPSoutages.Itusesadditionalsensorstomeasurespeed,headinganddirection(forward/backward).Therefore

aDRenabledGPSreceiverconsistsofaGPSreceiver,aturnratesensor(gyroscope)andaspeedindicator

(odometer1).BycombiningtheinformationofallsensorsapositioncanbedeterminedevenifGPSpositioningis

degradedorimpossibleduetorestrictedskyview.ThismeansthataDRenabledreceivercontinuestoreport

positionswhenGPSsignalsareblocked,suchasintunnelsorinheavyurbancanyonenvironments.

GPS Kalman Filter

GPS

receiver

Dead Reckoning

Parameter Enhanced Kalman Filter (EKF)

Position,

Speed,

Direction,

Time

Calibration

TurnRate

Speed

Forward/Backward

GPS

Signals

GPSPosition,

GPSData



Figure 1: Dead Reckoning Block diagram

1.2 Dead Reckoning Principle

IncontrasttoGPS,whichdeliversabsolutepositions,DeadReckoningisarelativemethod.Thesensorsgive

informationforadefinedmeasurementperiod,andthelocationiscalculatedrelativetothepreviouslyknown

position.ThereforeanabsoluteGPSpositionisrequiredasastartingpoint,whichisthelastknownGPSposition.

n+1

+dy

n+1

+dx

Known parameters:

=Traveleddistance(odometer,direction)

=Newangle(gyroscope)

=scos(

)

=ssin(

)

=last GPSposition

=DRposition



Figure 2: Dead Reckoning Principle

Parametersusedfortherelativepositioncalculationare:





1Anodometerisbydefinitionadevice,whichmeasureslineardistancetraveled.GPSreceiverscanalsoincludesoftware(alsoknownasan

odometer)usedtocalculatethisdistance.

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign DeadReckoningFundamentals

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• Distance travelled:Odometerpulses

• Direction:Forward/backwardindicator

• Angular turn rate:Gyroscope

1.3 Dead Reckoning Performance

AsDRisanincrementalalgorithm,thequalityoftheDRpositiondependsverymuchonthequalityandstability

ofthesensorsused.Anaccuratemodel,lowtolerancesandlowthermaldriftsareessentialforreliableposition

output.

TheperformancefiguresofaDRsystemarealwaysproportionaltodistancetraveledortime.

calculated route

based on sensor

signals

Known parameters:

=Traveleddistancesince GPSSignalslost

=Distanceerror

Performance parameters:

d/S

=Positionerrorpercentageincomparison

todistancetraveled

∆Φ

Angularheadingerror

Fix types:

=GPSposition

=DRposition

=Realposition

∆Φ

Actual route

Length = S



Figure 3: Dead Reckoning Performance Parameters

TheseamlesstransitionbetweenabsoluteGPSpositionsandrelativeDRpositionsisadvantageousingetting

optimalperformancefromaDRenabledGPSreceiver.ANTARIS®4GPSTechnologyemploysblendedalgorithms

toobtaintheoptimumfrombothsystems.

GPSPositioningisweightedmoreheavilyaslongastheGPSparameter(e.g.DOP,numberofsatellites,signal

quality)indicatesgoodandreliableperformance.Insituations,wheretheGPSsignalsarepoor,reflectedfrom

buildings(multipath)orjammedtheDRsolutionisusedwithahigherweighting.

Poor GPSNo GPS Good GPS

GPS DRGPS DRGPS DR

Extrapolation Blending Calibration

EKF EKF EKF

Position,Velocity,Time

Position,Velocity,Timefrom

real-timeclock

Altitudeheldconstant



Figure 4: Dead Reckoning Blending

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign DeadReckoningFundamentals

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your position is our focus

• No GPS:DuringGPSloss,onlyDR-(sensorbased)positionsarereported.Thepositioniscalculated

basedonthesignalsoftheturnratesensorandspeedsensor,withreferencetothelast

knownGPSsolution.

• Poor GPS:InurbancanyonswithfastchangingskyvisibilityorduringdegradedGPSreception,the

ANTARIS®4DRTechnologyperformsacalculationbyblendingtheGPSandsensorbased

positioning.

• Good GPS:WithgoodGPSperformanceandoptimalskyview,theGPSpositionhasahigherweight

thantheDR/sensorbasedpositionontheoverallnavigationsolution.Inthissituation,the

GPSpositionvaluesareusedtocalibratetheDRsensorsortoperformsensorintegrity

checks(toestablishifthesensorsarewellcalibrated).

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign DeadReckoningFundamentals

GPS.G4-MS4-05043  Page 9

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your position is our focus

2 Design-In

ThissectionprovidesaDesign-InChecklistaswellasReferenceSchematicsfornewdesignswithLEA-4R/TIM-4R.

FormigrationofexistingTIM-LRproductdesignstoTIM-4RpleaserefertoAppendix A.

2.1 Schematic Design-In Checklist for LEA-4R/TIM-4R

Designing-inaLEA-4R/TIM-4RGPSreceiveriseasy,especiallywhenadesignisbasedonthereferencedesignin

Appendix C.Nonetheless,itpaystodoaquicksanitycheckofthedesign.Thissectionliststhemostimportant

itemsforasimpledesigncheck.TheLayoutChecklistinSection 2.4alsohelpstoavoidanunnecessaryrespinof

thePCBandhelpstoachievethebestpossibleperformance.

! Note It’shighlyrecommendedtofollowtheDesign-InChecklistwhendevelopinganyANTARIS®4GPS

applications.Thiscanshortenthetimetomarketandsignificantlyreducethedevelopmentcost.

! Note Forimportantinformationexplainingthevariousaspectsofthischecklistseesection3intheAntaris®4

System Integration Manual [5]

Check Power Supply Requirements and Schematic:

 Isthepowersupplywithinthespecifiedrange?

 PlaceanyLDOasnearaspossibletotheVCCpinofthemodule;ifthisisnotpossibledesignawidepower

trackorevenapowerplanetoavoidresistancebetweentheLDO/powersourceandtheGPSModule.

 IstherippleonVCC below50mVpp?

Backup Battery

 AbackupbatteryisamustforDRenabledGPSreceiver’sdesigns.

 MakesuretoconnectabackupbatterytoV_BAT.LEA-4R/TIM-4Rdonotoperatewithoutabackupbattery.

 Whenyouconnectthebackupbatteryforthefirsttime,makesureVCC isonor–ifnotpossible–powerup

themoduleforashorttime(e.g.1s)ASAPinordertoavoidexcessivebatterydrain.

 Whilepoweroff,makesuretherearenopull-upordownresistorsconnectedtotheRxD1,RxD2,EXTINT0

andEXTINT1asthiscouldcausesignificantbackuporsleepcurrent(>25µAormoreinsteadof5µA).

Antenna

 Activeantennaissupported.

 Thetotalnoisefigureshouldbewellbelow3dB.

 Ifapatchantennaisthepreferredantenna,chooseapatchofatleast18x18mm(25x25mmisevenbetter).

 Makesuretheantennaisnotplacedclosetonoisypartsofthecircuitry.(e.g.micro-controller,display,etc.)

 Foractiveantennasadda10RresistorinfrontofV_ANTinputforshortcircuitprotectionorusethe

antennasupervisorcircuitry.

 WhenmigratingfromTIM-LRreduceR5oftheAntennaShortandOpenSupervisorcircuitto18k.

 Adaptthevalueofsomeoftheresistorsinthereferencedesigntothe3.0Vvoltagelevels(seeAppendix C).

Serial Communication

 ChooseUBXforanefficient(binary)datahandlingorifmoredataisrequiredthansupportedbyNMEA.

 WhenusingUBXprotocol,checkiftheUBXqualityflags(seeSection 4.1.9.2)areusedproperly.

 CustomizetheNMEAoutputifrequired(e.g.NMEAversion2.3or2.1,numberofdigits,outputfiltersetc.)

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign Design-In

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Schematic

 LeavetheRESET_Npinopenifnotused.Don’tdriveithigh!

 LeaveBOOT_INTpinopenifnotusedforfirmwareupdate.

 Planuseof2ndinterfaceforfirmwareupdatesorasaserviceconnector.

2.2 TIM-4R/LEA-4R Design

LEA-4R

TIM-4R

Odometer

Optional

Direction

Turn Rate Sensor

Filer, opto-couplers

3Vlevels

SPEED

FWD

SPIRATE

Low-Pass

filter

(MOSI)leaveopen

Digital

Temp

Sensor

GND

RF_IN

Coaxial

connector

RF_IN VANTV_ANT

AADET_N

VCC_REF

V_BAT

VCC(3V)

GND

VDD18_OUT

TxD1/ TxD2

RxD1/ RxD2

USB

TIMEPULSE

RESET_N

Optional

(BOOT_INT)leaveopen

Opencircuit

detection

(optional)

Gyro

Backup

Supply



Figure 5: Block Schematic of a complete LEA-4R / TIM-4R Design

2.2.1 Forward / Backward Indication

Useoftheforward/backwardindicationsignalFWDisoptionalbutstronglyrecommendedforgooddead

reckoningperformance.ConnecttoVDD18_OUT(1.8V)ifnotused.

Youneedtocheckthevoltagelevelsandthequalityofthevehiclesignals.Theymaybeofdifferentvoltage

levels,forexample12Vnominalwithacertaindegreeofvariation.UseofoptocouplersorotherapprovedEMI

protectionandfilteringisstronglyrecommended.

2.2.2 Odometer / Speedpulses

DRreceiversusesignalsfromsensorsinthecartoestablishthevelocityanddistancetraveled.Thesesensorsare

referredtoastheodometerandthesignalscanbedesignatedodometerpulses,speedpulses,speedticks,wheel

pulsesorwheelticks.Thesetermsareoftenusedinterchangeablywhichcansometimesleadtoconfusion.For

thesakeofconsistency,inthisdocumentwewillbereferringtothesesignalsasspeedpulses.

2.2.3 Power Supply for Gyroscope, Temperature Sensor and A/D Converter

TheGyroandtheA/D-Converterareespeciallysensitivetovoltagedropandripple.Thereforeacleanpower

supplymustbedesigned,whichis,forexample,notaffectedfromcurrentspikesproducedbytheGPSmodule.

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign Design-In

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! Note ForbestDRperformanceit’srecommendedtodesignaseparate(reference)5Vpowersupplyforthe

gyroandtheA/Dconverter.

2.2.4 SPI Interface for Gyroscope and Temperature Sensor

TheLEA-4R/TIM-4RareconfiguredasSPImasters.FollowingsignalsareusedfortheSPIinterface:

Pin Signal name Direction Usage

22PCS2_NOutputSelectsA/Dconverterforgyrosignal

9PCS0_NOutputSelectstemperaturesensorwithSPIinterface

23SCKOutputSPIclock

2MISOInputSerialdata(MasterIn/SlaveOut)

1MOSIOutputSerialdata(MasterOut/SlaveIn),leaveopen

Table 1: SPI pin for LEA-4R

Pin Signal name Direction Usage

24PCS1_NOutputSelectsA/Dconverterforgyrosignal

25PCS0_NOutputSelectstemperaturesensorwithSPIinterface

26SCKOutputSPIclock

27MISOInputSerialdata(MasterIn/SlaveOut)

28MOSIOutputSerialdata(MasterOut/SlaveIn),leaveopen

Table 2: SPI Pin for TIM-4R

ThefollowingblockschematicspecifiestheA/DconverterandtemperaturesensorfortheLEA-4RandTIM-4R.

PleasenotethattheNationalLM70-3sensorfunctionsat3V.Ifthe5Vversion(LM70-5)isused,alevel

translationwithopen-drainbuffersandpull-upresistorsattheoutputsisrequired.

LEA-4R

TIM-4R

Turn Rate Sensor

(MOSI)

22K

10R

leaveopen

Gyro

SCK

MISO

PCS0_N

PCS1_N(TIM-4R)

+5V

REF

10uand

100 n

GND

CONV

SCK

VCC

REF

12-Bit

A/DConverter

Linear LTC1860

Temperature

Sensor

National LM70-3

SDO

SI/O

GND

+3V

220n/100n

RATE

100n

GND

100K

VDD18

PCS2_N(LEA-4R)



Figure 6: Attaching A/D converter and temperature sensor using SPI interface

ForPCS0_N,apull-upresistorisnotrequiredsincethispinalreadyhasapull-upresistorinsideLEA-4R/TIM-4R.

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign Design-In

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Forbestresults,supplythe5Vvoltageforthegyroscopethroughalowpassfilterasillustrated.Providea

dedicatedreferencevoltagelinefromthegyroscopesupplypintotheVREFinputoftheA/Dconverter.

Addappropriatecouplingcapacitancesaccordingtotherecommendationsinthedatasheetsoftheillustrated

semiconductorproducts.Allshownresistorsshallhave5%accuracyorbetter.Allshowncapacitors(X7Rtypes)

shallhave10%accuracyorbetter.

! Note ForcorrectoperationwiththeLEA-4R/TIM-4Rfirmware,thiscircuitmustbeadoptedwithoutmaking

anymodificationssuchas,butnotlimitedto,usingdifferenttypesofsemiconductordevicesand

changingsignalassignment.

2.3 Pinout tables

LEA-4R TIM-4R

NameI/ODescriptionNameI/ODescription

1 MOSIOSPIMOSIVCCISupplyvoltage

2 MISOOSPIMISOGNDIGround

3 TxD1OSerialPort1BOOT_INTIBootmode

4 RxD1ISerialPort1RxD1ISerialPort1

5 VDDIOIPadvoltagesupplyTxD1OSerialPort1

6 VCCISupplyvoltageTxD2OSerialPort2

7 GNDIGroundRxD2ISerialPort2

8 VDD18OUTO1.8VoutputFWDIDirectionindication(1=Forward)

9 PCS0_NOSPIChipSelect0(Temperature

Sensor)

EXTINT1IExternalInterupt

10 RESET_NI/OResetVDD18_OUTO1.8Vsupplyoutput

11 V_BATIBackupvoltagesupplyGNDIGround

12 BOOT_INTIBootmodeGNDIGround

13 GNDIGroundGNDIGround

14 GNDIGroundGNDIGround

15 GNDIGroundGNDIGround

16 RF_INIGPSsignalinputGNDIGround

17 GNDIGroundRF_INIGPSsignalinput

18 VCC_RFOOutputVoltageRFsect. GNDIGround

19 V_ANTIAntennaBiasvoltageV_ANTIAntennaBiasvoltage

20 AADET_NIActiveAntennaDetectVCC_RFOOutputVoltageRFsection

21 FWDIDirectionIndication(1=Forward)V_BAT2IBackupvoltagesupply

22 PCS2_NOSPIChipSelect2(A/DConverter)RESET_NI/OReset(Activelow)

23 SCKOSPIClockSPEEDISpeedpulses

24 VDDUSBIUSBSupplyPCS1_NOSPIChipSelect1(A/DConverter)

25 USB_DMI/OUSBDataPCS0_NOSPIChipSelect0(TemperatureSensor)

26 USB_DPI/OUSBDataSCKOSPIclock

27 SPEEDISpeedpulsesMISOISPIMISO

28 TIMEPULSEOTimepulse(1PPS)MOSIOSPIMOSI

29 - TIMEPULSEOTimepulsesignal

30 - AADET_N3IActiveAntennaDetect

Shadedpinsrelatetodeadreckoningspecificfunctionality.

Table 4: Pinout LEA-4R/TIM-4R



2Batterybackupvoltageisnecessarytomemorizethelastvehiclepositionanddirectionoftheprevioustrip.Thisisparticularlyimportant

whentheprevioustripendedinanobstructedplace,forexampleaparkinggarage,andplausibledeadreckoningnavigationshallcontinue

whendrivingagain.



3AADET_Nwillonlybeoperatedasinputpinif“OpenCircuitDetection”foractiveantennasisactivatedorconfigured.

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2.4 Layout Design-In Checklist for ANTARIS®4

FollowthischecklistforyourLayoutdesigntogetanoptimalGPSperformance.

Layout optimizations

 IstheGPSmoduleplacedaccordingtotherecommendationinAntaris®4 System Integration Manual [5]?

 HaveyoufollowedtheGroundingconcept?

 Keepthemicrostripasshortaspossible.

 AddagroundplaneunderneaththeGPSmoduletoreduceinterference.

 Forimprovedshielding,addasmanyviasaspossiblearoundthemicrostrip,aroundtheserial

communicationlines,underneaththeGPSmoduleetc.

Calculation of the micro strip

 Themicrostripmustbe50OhmsanditmustberoutedinasectionofthePCBwhereminimalinterference

fromnoisesourcescanbeexpected.

 Incaseofamulti-layerPCB,usethethicknessofthedielectricbetweenthesignalandthe1stGNDlayer

(typicallythe2ndlayer)forthemicrostripcalculation.

 IfthedistancebetweenthemicrostripandtheadjacentGNDarea(onthesamelayer)doesnotexceed5

timesthetrackwidthofthemicrostrip,usethe“CoplanarWaveguide”modelinAppCadtocalculatethe

microstripandnotthe“microstrip”model.

2.5 Layout

PleaserefertotheAntaris®4 System Integration Manual [5] forlayoutrecommendations.



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3 Receiver Description

3.1 Dead Reckoning enabled GPS module (DR module)

3.1.1 Architecture

ADeadReckoningenabledANTARIS®4GPSReceivercontainsanANTARIS®4GPSmodulewiththeadditionof

anEnhancedKalmanFilter(see Figure 7).ConnectedtotheDRmoduleareaturnratesensor(gyroscope)witha

temperaturesensor,odometer(speedpulsesignalsource)andadirectionindicator(forward–backward.).

SimilartotheANTARIS®4GPSmodules,theDRmodulesupportsactiveandpassiveantennasandhasan

optionalantennasupervisorcircuitry.Twoserialportsareavailableforcommunication(seeSection on Serial

Communication in Antaris®4 System Integration Manual [5])andarefreelyconfigurableforNMEAoru-blox

proprietaryprotocols.ItprovidesaTIMEPULSEsignalfortimingsynchronization(seeSection on Timing in

Antaris®4 System Integration Manual [5]).

InordertostoreanyDRspecificdatasuchaslastposition,currentheading,calibrationdata,thetemperature

compensationtable(TC)etc.,aDRmodulerequiresabackupbattery.Furthermore,thesedataarestoredin

Flashinrepetitiveintervals.

! Note Donotuseanypowersavingmodes(e.g.FixNow™Mode)astheDRalgorithmandpowersaving

modesareincompatible.

3.1.1.1 Enhanced Kalman Filter (EKF)

TheEnhancedKalmanFilteristhecoreoftheANTARIS®4DRTechnology.Itcombinesallthesensorsignals

(odometer,directionindicator,gyroscope,temperature),whicharesampledwith40Hzandcombinesthemwith

theGPSsolution.

TheGPSKalmanFilterandtheEnhancedKalmanFilteraretightlycoupledtoproducethebestpositionsolution

fromboth,theGPSsystemandthesensor-basedsystem.Theweightingbetweenbothsystemsiscontrolledby

GPSqualityindicators(e.g.DOPvalues,numberofSV,residualsetc.)andvariancesforallDRrelatedparameters.

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign ReceiverDescription

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GPS Front-End

Functionality

GPS Antenna

Gyro

Direction

Digital

Temp.

Sensor

Odometer

RF_IN

Position Calculation

KalmanFilter

Stage1

Dead Reckoning

Enhanced KalmanFilter

Weighted-Mixer

Stage2

1 Hz

update rate

40 Hz

update rate

1 Hz

update rate

DR enabled

GPS receiver

serialoutput

Calibration

Parameters,

Temperature

offsettable



Figure 7: Enhanced Kalman Filter

3.1.1.2 Sensor Integrity Check

TheSensorIntegrityCheckmonitorsthequalityoftheattachedsensors(gyroandodometer)andreports

unexpecteddrifts,ormalfunctions.AssoonastheDRsensorsaresufficientlycalibratedtheANTARIS®DR

Technologybeginswithsensorintegritychecks.

Ifasensorsignalisoutofrange,anerrormessageisproducedviaserialportandreportedinNAV-EKFSTATUS.

InthiscasetheEnhancedKalmanFilterisswitchedoffmeaningthatsubsequentlyonlyGPSpositionsolutions

arereported.

Torecoverthesystem,thesensorshavetobecheckedformechanicalfailures,allcalibrationparameter(Sensor

CalibrationandTemperatureCalibration)havetoberesetandaninitialcalibration(seeSection3.1.4)hastobe

done.

Forshortminimalerrorsthesystemisabletorecoveritself.InthiscasetheerrorwillbeclearedandtheDR

modulewillreportcombinedpositionsolutionsagain.

! Note TheINFmessage:“ERROR:EKFdisabled.Gyrodatainconsistent.”indicatesashutdownoftheDR

algorithmduetoinconsistencyofthegyrosignal.Ithappensifthegyroisdefectorthesystemis

miscalibrated.Torecover,checkthegyroandresetthereceiver.Ifithappensagain,resetallcalibration

dataandrepeataninitialcalibration.

! Note TheINFmessage:“ERROR:EKFdisabled.Tickdatainconsistent.”indicatesashutdownoftheDR

algorithmduetoinconsistencyofthespeedpulses/odometersignal.Ithappensifthespeedsignalline

orthesensorisbroken.Torecover,checktheodometersignalandresetthereceiver.Ifithappens

again,resetallcalibrationdataandrepeataninitialcalibration.

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign ReceiverDescription

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3.1.2 Input Signals/ Sensors

3.1.2.1 Turn rate sensor (Gyroscope)

Thegyroscopeindicatestheturnrateofthedevice.ThegyrooutputsignalisconnectedviaanA/Dconverterto

theDRmoduleandsampledat40Hz.Theintegrationofthegyrosignaloveronemeasurementperiodisequal

totherelativeturnofthedeviceduringthisperiod.

Therearethreemajorparametersofthegyroscope:

• Gyro Bias:Describestheoffsetofthegyrosignalataturnrateof0[deg/s].+/-25.0[deg/s]isthe

maximumallowedGyroBiasOffset.

• Gyro Scale Factor:Describestherelationofthetypicalgyrosensitivity[V/(deg/s)]oftherealmeasured

outputvoltage[V]totheactualturnrate[deg/sec].

Thisvaluehasanupperlimitof1.2,andalowerlimitof0.8.Thismeansthatthe

implementedgyrocanvaryby+/-20%,fromthetypicalgyrosensitivity.

• Gyro Bias as function of the temperature:

AnydifferencesfromtheGyroBiasOffsetovertheentiretemperaturerangearestoredin

alookuptable,calledTemperatureCompensationTable(TC).Thistablecoversa

temperaturerangeof–40degCelsiusto+80degCelsius.

TurnRate

w[deg/s]

+100

Gyro

Voltage

0-100

2.5

5.0

GyroBiasOffset

typicalGyroSensitivity

GyroScaleFactor

realGyroSensitivity



Figure 8: Gyroscope Signals

Gyro-

scope

module



Figure 9: Gyroscope Signals Flow

! Note Themountingangleofthegyroinfluencesitsperformancesignificantly.Theangleofinclineshouldnot

exceedthemaximalvaluereferringtotheturnaxisofthevehicle.Consultthedatasheetofthegyro

carefullytochoosetheappropriatemountingtechniqueaswelltherightparametersettings(e.g.Gyro

Sensitivity,Polarity,maxangleofinclinationetc.)

Zaxis

Yaxis

Xaxis

zaxis

Angleofincline

Gyro



Figure 10: Mounting of the gyroscope

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign ReceiverDescription

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

RefertotheLEA-4R/TIM-4Rdatasheetsforrecommendationsabouttheselectionofgyros.

! Note Pleasefollowdesignrecommendationsfromthegyroscopemanufacturersforproperanalogsignal

conditioning.

3.1.2.2 Temperature sensor

TheOutputoftheGyroscope(especiallyGyro Offset)isverysensitivetotemperaturechanges.Therefore

ANTARIS®DRmodulessupportanautomatictemperaturecompensationagainstthiseffect.

Toachievereasonableperformanceofthiscompensationthetemperaturesensorhastohaveamoderate

hysteresisandtheenvironmentaltemperatureshavetobereproduciblebyaround5degreesCelsius.

! Note ThetemperaturesensorhastobebuiltintheGyroscopeorasnearaspossibletotheGyroscopeto

measurethetemperatureofthegyroscope.

Temperature compensation

TocompensatethevariationoftheGyroOffsetwithdifferenttemperatures,theANTARIS®DRTechnology

maintainsaTemperature Compensation table(TC).Therangeisfrom–40to+85degreesCelsius.Thetableis

continuouslyupdatedwithnewvaluesassoonasthereceiverisstationary(noodometerpulsesattheinput)for

morethan3seconds.Thisprocessallowsthereceivertolearnaboutthetemperaturecharacteristicsofthe

individualgyroinitsspecificenvironment.

TheTCstabilizesasmoremeasurementsareobservedforthesametemperature.Fortemperaturerangesnot

measuredyettheTCBiasOffsetwillbeextrapolatedfromtheavailabledata.

degree

Celsius

+80

TCBias

Offset

+40

-40



Figure 11: TC compensation graph

! Note TheINFmessage:“WARNING:DiscardedTCMeasurement:RMSGyro=xx.xxxmV”indicatesthatthe

gyrohasatohighnoisetomeasureit’soffsetvaluesfortemperaturecompensation.Ifthismessage

appearsregularly,thegyromighthaveamechanicaldefectorismountedataplacewithtoohigh

vibrations.

3.1.2.3 Speedpulse Signal

ThespeedpulsesignalrequiredforDRmodulesmusthaveafrequencyrangefrom1Hzto5kHz(0Hzisequalto

aspeedof0km/hour).Thespeedpulsesignalmustbelineartothedrivenspeed.

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign ReceiverDescription

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TheScale Factor istheratiobetweenthefrequencyofthespeedpulsesignalandtherealspeed.Ithasa

maximumrangeof0.02[m/pulse]to1[m/pulse](i.e.from50kpulsesperkmto1000pulsesperkm.IftheScale

Factor exceedsthelowerorupperlimit,theoutputwillbeheldatthelimitingvalue.

x00.050

Measurement

Interval

x00.060 x00.070 x00.080 x00.090 x00.100 x00.110 x00.120

0 112211

SpeedpulsesperInterval

Timetag



Figure 12: Speed signal

! Note Non-linearityofthespeedpulsesignal(e.g.nopulsesbelow5km/h),mayleadtowrongdirection

calculationandthereforewrongpositioning.

! Note Ifthepulsefrequencyisbelowtheminimumfrequency(1Hz),speedwillbesetto0m/sandtheposition

outputisfrozenatthelastknownposition.

3.1.2.4 Direction (Forward/ Backward Signal)

Thedirectionsignalindicateswhetherthevehicleismovingforwardorbackward.Ifthesignalishigh,it

indicatesforwarddriving,butitcanbeconfiguredvice-versainUBX–CFG(Config)–EKF(EKFSettings).

It’srecommendedtouseadirectionindicatorforbestDRperformance.Ifnodirectionsignalisavailable,it’s

recommendedtosetthedirectiontoforward.

Consequencesifnodirectionsignalisavailable:

Direction

GPS coverage

Forward Backward

Insufficient to

determine a position

(DR only)

Thedirectionsignalindicatesthe

rightdirection

Good DR performance, all

position are valid

TheDRoutputwillindicateawrong

direction(alwaysforward).

DR positions are wrong as the

direction is wrong

Good GPS coverage Thedirectionsignalindicatesthe

rightdirection

 Good DR performance

Forshortdistancestheinfluenceofthe

mismatchingdirectionsignalcanbe

neglected(inorderofmeters,e.g.

maneuveringacarintoaparkinglot).

Forlongerdistancesitmighthave

significantimpacttothecalibration

parameter.

Table 5: Consequences of a missing direction signal

! Note Astheforward/backwarddirectionsignalisnotavailableinallcars,trytomakeuseofthereversegear

light.

LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign ReceiverDescription

GPS.G4-MS4-05043  Page 19

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your position is our focus

3.1.3 DR specific Parameters

3.1.3.1 DR specific GPS configuration

AstheGPSKalmanFilterandtheEnhancedKalmanFilterareoptimizedbyu-blox,donotchangethePower

ModeinUBX-CFG(Config)–RXM(ReceiverManager)oranyoftheUBX-CFG(Config)–NAV(Navigation)

parameters!

3.1.3.2 DR Configuration Options

ThefollowingconfigurationoptionsareavailablewiththeUBX–CFG(Config)-EKF(EKFSettings)message:

• TheEKFcanbeenabledordisabled.WhentheEKFisdisabledthemodulefunctionsonlyintheGPSmode,

thereisnoDRfunctionalityavailable.

• Itispossibletomanagedataandmemoryinthefollowingways.Pleasenotethatifthedefaultsettingsare

changedthemaximumnumberofflashwrite/releasecyclesneedstobetakenintoaccount:

• TheTemperatureTableandCalibrationDatacanbecleared.Whenthisisthecasethecalibrationbegins

again.

• TheintervaltosavethecontentofthetemperaturecompensationtablefromtheinternalBattery

BackupRAMtotheFlashmemorycanbedetermined.

• Thehardwareinterfacecanbeconfiguredinthefollowingways:

• TheDirectionPinPolaritycanbeset.Thedefaultis‘0–High=Forward’

• TheaxisorthedirectionofrotationoftheGyroifthevoltageoutputispositivecanbeset(default

settingis‘0–ClockwiseRotation).

• Thehardwarecanalsobeconfiguredtosimplifycalibration.Thisdoesnot,however,eliminatetheneedto

performacalibration.

• TheOdometercanbeconfiguredtosetthenumberofspeedpulsesperkilometer(defaultvalueis3500

[pulses/km]).

• ThenominalbiasvoltageandsensitivityoftheGyrocanbeset,aswellasthemaximumallowedRMSof

theGyro.ThisvalueisneededtocontrolthequalityofthemeasuredGyrooffsettobesavedinthe

temperaturecompensationtable.

TheDRStatusisreportedbythe(PUBX,05/EKFSTATUS)message.

! Note FordetailedinformationregardingtheconfigurationofthemessagespleaseseetheANTARIS 4GPS

TechnologyProtocolSpecifications[3].

3.1.3.3 DR Navigation Parameters (UBX – NAV (Navigation) – EKFSTATUS (Status))

Parameter Description Unit

Sensor Data 

SpeedPulsesNumberofspeedpulsesinonemeasurement

period[Pulses/Period]

PeriodDurationofonesensormeasurementperiod[ms]

MeanGyroUncorrectedMeanValueoftheGyrointhelast

period.

TemperatureMeasuredtemperatureatthegyroscope[°C]

DirectionSignalfromthedirectionindicator[forward/backward]

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LEA-4R/TIM-4R-SystemIntegrationManual/ReferenceDesign ReceiverDescription

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u-blox LEA-4R System Integration Manual And Reference Design

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