u-blox ANTARIS 4 User Manual

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Smallersizedpatcheswillusuallyreachtheirmaximumgainwithaslightlysmallergroundplanecomparedtoa
larger sizepatch. However,themaximum gainof  a smallsized patch withoptimumgroundplanemay stillbe
muchlowerthanthegainofalargesizepatchonalessthan
optimalgroundplane.
Itisnotonlygainandaxialratioofthepatchantennathatisaffectedbythesizeofthegroundplanebutalso
thematchingoftheantennatothe50Ohmsimpedanceofthereceiver.SeeSection 1.5.8 formoreinformation
onmatching.
1.5.4 Helix Antennas
Helixantennas canbe designedfor usewith orwithout ground plane.For example,theradiatingelements on
boardtheGPSsatelliteshaveagroundplane.Usinganarrayofhelixantennas,theGPSsatellitescancontrolthe
directionoftheemittedbeam.Ifahelixantennaisdesignedwithoutground
planeitcanbetunedsuchtoshow
amoreomnidirectionalradiationpatternasshowninFigure 10.
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Figure 10: Radiation pattern of helix antenna without ground plane, Sarantel, Ltd.
Althoughwecandeterminean axialratio closeto 9dB between zero degree and90degrees elevation, which
redonthemarket.Again,antennagainwilldecreasewithdecreasedsize.
rs
prefer the pole like style of the helix antenna, which is quite similar to the style of
 antennas used in mobile
e application is a hand held device, the antenna should be
designed in such a waythat natural user
operationresults in optimum antennaorientation. The helix antenna
srespect.
compares to the patch antenna, the back lobe of the helix generally degrades much smoother and does not
show any sensitivityat the –180degreedirection. In contrast, the back lobe of
 a patch antenna depends very
muchonsizeandshapeofthegroundplane.Aswithpatchantennas,fillingtheantennawithamaterialwitha
high dielectric constant can reducethesize of helix antennas. Sizes in the order of 18mm length and 10mm
diameterarebeing
offe
1.5.7 Helix or Patch, which selection is best?
For practical applications the possibilities of integrating a certain style of antenna into the actual device is  of
primaryconcern.Somedesignsnaturallypreferthepatchtypeofantenna,e.g.forrooftopapplications.Othe
phones.Furthermore,itisimportantthattheantenna’smainlobepointstotheskyinordertoreceiveasmany
satellites as possible with maximum gain. If th
seemstobemoreappropriateinthi
However, one has to keep in mind that comparable antenna gain requires comparable size of the antenna
aperture, which will lead to a larger volume filled by a helix antenna in comparison to a
 patch antenna. Helix
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) GPSFundamentals
GPS.G4-MS4-05007-A1
  Page 19

u-blox ANTARIS 4 Specifications

General

Brand	u-blox
Model	ANTARIS 4
Category	GPS
Language	English