u-blox ANTARIS 4 User Manual

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Moreover,the GPSbandisfarbeyondthe1GHz limitthatappliestoalmostallEMCregulations.So, evenifa
deviceiscompliantwithrespecttoEMCregulationsitmightseverelydisturbaGPSreceiver.
IftheGPSantennaistobeplacedveryclosetosomeotherelectronics,
e.g.theGPSreceiveritselforaPDA-like
e, nvery seriously rightfromthe conceptphaseofthe design.Itis oneof
r and Ground Planes
Usesolidplanesforpowerandgroundinterconnect.ThiswilltypicallyresultinaPCBwithatleastfourlayersbut
willalsoresultinamuchlowerradiation.Solidgroundplanesensurethatthereisadefinedreturnpathfor
the
signals routed on thesignal layer.Thiswill reduce the “antenna” areaof the radiating loop. Planes shouldbe
solidinasensethattherearenoslotsorlargeholesinsidetheplane.
Theouterextentofthepowerplaneshouldbewithintheextentoftheground
plane.Thisavoidsthattheedges
of the two planes form a slot  antenna at the board edges. It’s a good idea to have a ground frame on the
circumferenceofeverylayerthatisconnectedtothegroundplanewithasmanyviasaspossible.Ifnecessary,a
shield can
 then be easily mounted on top of this frame (see Figure 12). Furthermore, free space on the
outermost Layers can be filled with ground shapes connected to the ground plane to shield radiation from
internallayers.
applianc theEMC issuemust betake
the most demanding tasks in electrical engineering to design a system that is essentially free of measurable
emissionsinagiven
frequencyband.
1.6.2 Eliminating Digital Noise Sources
Digital noise is caused by short rise-times of digital signals. Data and address buses with rise-times in the
nanosecondrangewillemitharmonicsuptoseveralGHz.Thefollowingsectionscontainsomegeneralhintson
howtodecreasethelevelofnoiseemittedfromdigitalcircuitboardthatarepotentiallyin
closeproximitytothe
GPSreceiverortheantenna.
1.6.2.1 Powe
Bad: Excessive Radiation
Good: Radiation terminated
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Figure 12: Signal and power plane extends should lie within ground plane extends
Optional shield
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Figure 13: Further improvement of reduction of power plane radiation
1.6.2.2 High Speed Signal Lines
Keep high-speed lines as short as possible. This will reduce the area of the noise-emitting antenna, i.e. the
conductor traces. Furthermore, the use of line drivers with controlled signal rise-time is suggested whenever
GPSModules-SystemIntegrationManual(SIM)(incl.ReferenceDesign) GPSFundamentals
GPS.G4-MS4-05007-A1
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u-blox ANTARIS 4 Specifications

General

Brand	u-blox
Model	ANTARIS 4
Category	GPS
Language	English