u-blox ANTARIS 4 - Page 110

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your position is our focus
Figure 86showsthesequentialorderofthesignalpresentatpinTIMEPULSEandtherespectiveoutputmessage
epersecondandaonesecondnavigationupdaterate.forthesimplecaseof1puls
UTC 8:30:00 UTC 8:30:01
Position fix
calculation
Protocol: UTC 8:30:00
TIMEPULSE
Serial Data Out
Protocol: UTC 8:30:01
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Figure 86: TIMEPULSE output signal and protocol time message, example for 1 s period and rising edge configuration
The navigation update rateand TIMEPULSE period should be configured toresult in ameaningful pattern. For
example,havingfournavigationupdatespersecondand3TIMEPULSE’spersecondwouldmakecorrelationof
TIMEPULSEoutputandoutputmessagedifficult.
aligned to the sampling clock of 23.104
MHz. This results in a timing re ion of
or has to be added to the time accuracy estimation delivered through the timing
messageUBX–TIM(Timing)-TP(Timepulse).
TherisetimeoftheTIMEPULSEsignalaffectsthe absoluteaccuracy oftheTIMEPULSEsignaland needstobe
considered. At 15pF load capacitance the output driver is able to deliver a typical rise time of 7ns, but the
maximumrisetimemayalsoreach25ns.Lowloadonthispinisthereforemandatory.
TheGPSreceiveralwayscalculatestimeandpositionatthephase
centeroftheGPSantenna.Astheapplication
usingthetimesignalisnotdirectlyattheantenna,anydelayscausedbycables,filtersandanyotherprocesses
havetobe considered.TheCable Delay (5.5ns/ m forPTFEisolatedcoaxial cable) is thedelay inthe antenna
cable
fromtheGPSantennaphasecentertotheAntennaPin,theRFGroupDelayisthedelayfromtheAntenna
Pin totheTIMEPULSEPin (which isdefined asa constant) andthe User Delay are anyother delays intheuser
application.
 Note WhenusingtheTIMEPULSEfora 
TimingApplicationitisrecommendedthattheRFsignaldelaybe
calibratedagainstareference-timingsource.
 Note To get the best timing accuracy withthe GPS antenna, a fixed position is needed and the receiver
mustbeconfiguredtothestaticplatform(refertoSection 4.6.3).
 Note UseLEA-4TforApplications
withhightimingaccuracyrequirements.
4.7.1.1 TIMEPULSE, Application Examples
The default setting for the TIMEPULSE defines a 1PPS signal, with a defined accuracy if the TDOP and
T accuracy masksareused.Parameterchangescanbemadeaccordingtospecificapplicationrequirements.
 Note Ifthereis‘NoFix’orTDOPorT accuracy maskareexceedednoTIMEPULSE
isbeingoutput.
The TIMEPULSE signal is
43ns. This quantization err
solut
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) ReceiverDescription
GPS.G4-MS4-05007-A1
  Page 110