u-blox ANTARIS 4 - Active Antenna Bias Power

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4.3.3 Active Antenna Bias Power
ion ption of LEA-4M. For LEA-4M and NEO-4S
nsiderthe
This sect only applies to TIM-4x and LEA-4x receivers with the exce
refer to Section 4.3.3.1.
Therearetwoways tosupply thebiasvoltage topinV_ANT.Itcanbe suppliedexternally(pleaseco
datasheet specification)or internally.For Internalsupply, theVCC_RFoutput must beconnected toV_ANTto
supply the antenna with a filtered supply voltage. However, the voltage specification
of the antenna has to
matchtheactualsupplyvoltageoftheANTARIS
®
4GPSReceiver(e.g.3.0V).
Active Antenna
Active Antenna
ANTARIS GPS Module
GND
RF_IN
GND
ANTARIS GPS Module
GND
RF_IN
GND
V_ANT
VCC_RF
LNA
external
supply
antenna
voltage
V_ANT
VCC_RF
LNA
R_BIAS

R_BIAS

Figure 61: Supplying Antenna bias voltage
Sincethebiasvoltage isfedintothemost sensitivepartofthereceiver,i.e.theRFinput, thissupplyshouldbe
virtuallyfreeofnoise.Usually,lowfrequencynoiseislesscriticalthandigitalnoisewithspuriousfrequencieswith
harmonicsuptotheGPSbandof1.575GHz.Therefore,it
isnotrecommendedtousedigitalsupplynetstofeed
pinV_ANT.
An internal switch (under control of the ANTARIS
®
4 GPS software) can shutdown the supply to the external
antennawheneveritisnotneeded.ThisfeaturehelpstoreducepowerconsumptionwhentheGPSreceiverisin
SleepMode.
4.3.3.1 Antenna Bias Voltage for LEA-4M and NEO-4S
his section only applies to LEA-4M and NEO-4S For all other receivers, refer to Section 4.3.3.
EO-4SandLEA-4MdonotprovidetheantennabiasvoltageforactiveantennasontheRF_INpin.It
istherefore
essary to provide this voltage outside the module via an inductor as indicated in Figure 62. u-blox
S-36NX). Alternative parts are feasible if the inductor’s
resonantfrequencymatchestheGPSfrequencyof1575.4MHz.
T
N
nec
recommends using an inductor from Coilcraft (0402C
Low Noise Amplifier
Active Antenna
RF_IN
VCC_RF
GND
GND

Figure 62: Recommended wiring for active antennas
PassiveantennascandirectlybeconnectedtotheRF_INpinofLEA-4MandNEO-4S. Noinductorisrequiredin
thiscase.
 Note Pleaserefertosection3.6.6forlayoutrecommendationsfortheantennabiasvoltageinductor.
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) ReceiverDescription
GPS.G4-MS4-05007-A1
  Page 74