u-blox ANTARIS 4 - Active Antenna

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your position is our focus
‘noise’thatmayinterferewiththeantennaperformance.ForfurtherinformationaboutAntennadesignsreferto

 Note
LNArequiredforpassiveantennas.
Activ tenn
ise amplifier. They can be directly connected to RF_IN. If an active
antennaisconnectedtoRF_IN,theintegratedlow-noiseamplifieroftheantennaneedstobesuppliedwiththe
throughthe
powercons
innerconductorwillbeseparatedfromtheRFsignalandrouted
tothesupplypinoftheLNA(seeFigure 60).
Section 3.4.
Passive antennas do not require a DC bias voltage and can be directly connected to the RF input pin RF_IN.
Sometimes,theymayalsoneedapassivematchingnetworktomatchtheimpedance
to50Ohms.
Note Some passive antenna designs presenta DC short to the RF input, when connected. If a system is
designedwithantennabias supplyAND thereisa  chanceofa passive antennabeing connectedto
thedesign,considerashortcircuitprotection.
AllANTARIS
®
4receivershaveabuilt-in
4.3.2 e An a
Active antennas have an integrated low-no
correct voltage through pin V_ANT or an external inductor. Usually, the supply voltage is fed
to the antenna
coaxialRFcable.ActiveantennasrequireapowersupplythatwillcontributetothetotalGPSsystem
umptionbudgetwithadditional5to20mAtypically.Insidetheantenna,theDCcomponentonthe
Antenna
Low Noise Amplifier LNA
ATR0610
GND
GND
V_ANT
Coaxial Antenna Cable
Active Antenna
RF_IN
17
19
V_ANT

Figure 60: Active antenna biasing
Generallyanactiveantennaiseasiertointegrateintoasystemdesign,asitislesssensitivetojammingcompared
to a passive Antenna. But an active Antenna must also be placed far from any noise sources to have a good
performance.
! Warning Antennas should only be connected to the receiver when the receiver is not powered. Do not
connect or disconnect the Antenna when the ANTARIS
®
4 GPS receiver is running as the receiver
calibrates the noise floor on power-up. Connecting the antenna after power-up can result in
prolongedacquisitiontime.
! Warning NeverfeedsupplyvoltageintoRF_IN. waysfeedviaV_ANToranexternalinductor.
 Note TotestGPSsignalreacquisition,werecommendphysicallyblockingthesignaltotheantenna,rather
thandisconnectingandreconnectingthereceiver.
Al
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) ReceiverDescription
GPS.G4-MS4-05007-A1
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