u-blox ANTARIS 4 - Page 60

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4.1.1.1 The RF Section explained
TheRFsectionfulfillsfourmajortasks:
• LowNoiseAmplificationoftheantennasignal
The built-in Low noise amplifier, LNA (ATR0610) provides the initial amplification of the antenna signal. It
hasaverylownoisefigureandisthefirstpre-amplificationstage.Theperformanceofthispartdetermines
thenoise
performanceofthewholereceiver.
• Filteringoftheantennasignal
SincethearchitectureoftheATR0601doesnotuseanimagerejectmixerforpowersavingreasons,aSAW
filterattheRFinputisneededtosuppresstheimagefrequency.
• Frequencyconversionoftheinputsignaltoa
frequencysuitedfordigitalprocessing.
• Samplingoftheanalogsignaltoobtainadigitalbitstream
loopisusedinfrontoftheA/D-convertertomaintainanoptimumloadfor
mize the dynamic range of its 1.5bit resolution. The A/D
converter output
signalissampledusingthesamplingclock,yieldingasynchronoustime-discreterepresentationoftheinput
ncy.
inte
Inorderto
supplyaDC tintotheV_ANTpin,whichisinternallyfedintotheRF_INpin.
4.1.1.2 The Digital Section explained
Anautomaticgaincontrol(AGC)
the converter input and maxi
signal.
• Generationofthemainclockfreque
An gratedcrystaloscillator(XTOorTCXO)generatesthemainclockfrequencyof23.104MHz.
easeconnectionofactiveantennas,abias-Tis
integratedintomostmodules.Itprovidestheabilityto
curren
Thecorecomponentofthedigitalsectionisthe highlyintegratedbasebandprocessorATR0621.It containsan
serialports).
e BO
firmwa
• TheRE eitherasoutputtoinitializeexternallogicuponpowerupoftheGPSmodule
orasinputtoinitiateahardwareresetoftheGPSmodulefromexternalhardware.
ROMbasedreceivershaveGPSMODEpinstodefineacustomizedstartupconfiguration.

ARM7CPU,the GPScorrelator hardware, RAMand ROM,batterybackupRAM,RTC,reset generator andtwo
voltageregulators.AllProgrammablereceiverscontainadditionalFLASHmemory.
ThecrystalrequiredfortheRTCis
alsointegratedintoallGPSmodules.
Digital Interface:
• AllGPSModuleshaveatleasttwocommunicationinterfaces(USBor
• PinEXTINT0canbeusedtogeneratedirectsoftwareinterruptsfromoutsideoftheGPSmodule.
• TheTIMEPULSEpinprovidesahighlyconfigurabletimepulsesignal,synchronizedtoUTCor
GPStime.
• Th OT_INT pin is used to start the GPS Receiver in Boot Mode (e.g. to recover in case of corrupt
reimagesduetofailedfirmwareupdates).
SET_Npincanbeused
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) ReceiverDescription
GPS.G4-MS4-05007-A1
  Page 60