u-blox ANTARIS 4 - Active vs. Passive Antenna

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your position is our focus
2.7 Active vs. Passive Antenna
ceivercannot provide
e
Time-To-First-Fix(TTFF).Therefore, good sky visibility is very important.
ge Carrier-To-Noise-Ratio (C/No) of
theaverageoftheC/Noratioof
as.
Firstsomegeneralissues:
• A GPSreceiver needstoreceive signals from asmany satellites as possible.A GPS re
optimal performance in narrow streets between high buildings (i.e. in urban canyons), in underground
parking lots or if objects cover the ant nna. Poor sky visibility may result in
position drift or a prolonged
• A GPS receiver will only achieve the specified performance if the avera
thestrongestsatellitesreachesatleast44dBHz.Inawell-designedsystem,
highelevationsatellitesshouldbe intherange
between44dBHzandabout50dBHz.Withastandardoff-
the-shelfactive antenna, 47dBHz should easily be achieved. Even the best receiver can’t make up for
signal loss due to a poor antenna, in-band jamming or a bad RF-board design.
Table4looksatsomeoftheissuestoconsiderwhenselectingactiveorpassiveantenn

Active Antenna Passive Antenna
ActiveantennaconnectedtotheGPSmodule.
Passivepatchantennas,chipantennasorhelical
antennasconnectedwithamicrostriporstriplineto
theGPSmodule.
A widerange of active patch or helicalantennas are
availableonthemarket.Theydifferinsize,sensitivity
andpowerconsumption
• Passive patch antennas or helical antennas are
availableindifferentformfactorsandsensitivities
• Needsmorepowerthanapassiveantenna
• Antenna must be connected with a
care
designed micro strip or strip line to the GP
fully
S
e antenna must
e sensitivity of the GPS antenna to
tingcircuitsorgeneralsignaljamming.
moduletoensureagoodGPSperformance.
• The PCB design with a passiv
consider th
otherradia

• Due to theproximity of antenna, GPS andother
circuits,in-bandjamming maybecomeelectronic
acriticalissue.

Table 4: Active vs. Passive Antenna
  you are not an expert in RF designs and place the antenna away fromNote Take an active antenna, if
noiseemittingcircuits.
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) SystemConsideration
GPS.G4-MS4-05007-A1
  Page 42