u-blox ANTARIS 4 User Manual


12x12mm
2
.VerycheapconstructiontechniquesmightuseordinarycircuitboardmateriallikeFR-4orevenair
as adielectric,but this will resultin a much largersize, typicallyintheorder of 10x10cm
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. Figure 8shows a
typicalexampleof theradiationpatternofa16x16mm
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ceramicpatchantenna.Thismeasurementonlyshows
theuppersphereoftheradiationpattern.Dependingongroundplanesizetherewillalsobeaprominentback
lobepresent.

Figure 8: Typical Radiation Pattern of a Patch Antenna, MuRata, Inc.
ForthespecificexampleshowninFigure 9 onecaneasilyseethattheso-calledaxialratio,therelationofmajor
tominoraxisoftheellipticalpolarizationhasaminimumatthe50mm
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squaregroundplane.Atthispoint,the
polarization ofthe antennais closestto anidealcircularpolarization (axialratio= 0dB). Ata 100mm
2
square
ground plane size this particular patch shows an axial ratio in the order of 10dB, which is closer to linear
inthe leftgraphof
usion, the correct
 groun compromis
polarization thantocircularandwillresultin respectivelosses. Thiseffectcanalsobe seen
the figure, where gain no longer increases
with increasing ground plane size. In concl
dimensions for the size of the d plane can serve as auseful e between maximum gain and
reasonablepolarizationloss.

Figure 9: Typical Gain and Axial Ratio of a Patch antenna with respect to ground plane size, MuRata, Inc.
A good allowance for ground plane size is typically in the area of 50to70mm
2
. This number is largely
independent of the size of the patch itself (when considering ceramic patches). Patch antennas with small
groundplaneswillalsohaveacertainback-lobeintheirradiationpattern,makingthemsusceptibletoradiation
comingfromthebacksideoftheantenna,e.g.multi-pathsignalsreflectedoffthe
ground.Thelargerthesizeof
thegroundplane,thelessseverethiseffectbecomes.
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) GPSFundamentals
GPS.G4-MS4-05007-A1
  Page 18

u-blox ANTARIS 4 Specifications

General

Brand	u-blox
Model	ANTARIS 4
Category	GPS
Language	English