u-blox ANTARIS 4 User Manual

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1.7 High Sensitivity GPS (SuperSense
®
GPS)
GPSsignalsarealreadyveryweakwhenthey arriveattheEarth’ssurface.By thetimetheGPSsignalsarriveat
the receiver they are typically as weak as –130dBm (–160dBW). This is well below the thermal noise level.
StandardGPSreceivers(e. TIM-4A)integratethereceivedGPSsignalsforup
to20ms.Thisresultsintheability
to track signals down to about –150dBm (–180dBW). High Sensitivity GPS receivers are able to integrate the
incoming signals much longer than this and can therefore track down to levels approaching -160dBm. High
SensitivityGPScanprovidepositioninginmanybutnotall
indoorlocations.Signalsareeitherheavilyattenuated
by the building materials or reflected in as multipath. High Sensitivity GPS Receivers can also  compensate the
performancedeficitsofsmallerantennas.
For Standard GPS Receivers, signal reflections and multipath effects are undesirable phenomena. Indoor GPS
reception, however, must - besides the direct line-of-sight
 signal - rely on reflected GPS signals in order to
receiveasufficientnumberofsatellitestocalculatepositions.Sincereflectionsincreasethepropagationdelays,
thepositioningaccuracywillobviouslydecrease.GoodHighSensitivityGPSReceiverslikeSuperSense
®
willtune
theirmultipathsuppressioninsuchawaythatmultipathissuppressedonchannelswithstrongsignalsinorder
 in caseof  poor reception in order toprovide an
optimalGPScoverage.
e
at aprice.Customers mustaccept some tradeoffs whilethe signal
mance (acquisition sensitivity, increased acquisition times), positioning
g.
to achieve anexcellent accuracywhereas itaccepts allsignals
Thebenefits ofweaksignal trackingcom
level is low: Reduced acquisition perfor
accuracyanddynamicresponsiveness.
Strong Signals Weak Signals
Acquisition
Positioning Accuracy
Verygood
Dependsonsignalquality
andEnvironment
Fast Limited
Dynamic Responsiveness
High Limited
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Figure 23: Trade-off in Weak Signal GPS
High Sensitivity GPS Receivers open new applications and market opportunities such as navigation in building
interiorsorthecovertuseofGPSreceiversinvehiclesandtheyhelptodrivedownthecostsbyallowingtheuse
ofsmallerGPSantennas.
Antenna: Located under seat
+ 3D Fix
+ 2D Fix
+ Degraded Mode
+ Invalid Fixes
TIM-LL (ANTARIS) TIM-LH (SuperSense)
Patch antenna in upright position
Antenna
underneath
driver'sseat
Antenna: Located under seat
+ 3D Fix
+ 2D Fix
+ Degraded Mode
+ Invalid Fixes
+ 3D Fix
+ 2D Fix
+ Degraded Mode
+ Invalid Fixes
TIM-LL (ANTARIS) TIM-LH (SuperSense)
Patch antenna in upright position
driver'sseat
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Figure 24: Improved GPS Coverage with High Sensitivity GPS Receivers
Antenna
underneath
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) GPSFundamentals
GPS.G4-MS4-05007-A1
  Page 29

u-blox ANTARIS 4 Specifications

General

Brand	u-blox
Model	ANTARIS 4
Category	GPS
Language	English