Data Sheet

FSC‐BT646Datasheet
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 ShenzhenFeasycomTechnologyCo.,Ltd   www.feasycom.com
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 9.2  LayoutGuidelines(InternalAntenna)
Itisstronglyrecommendedtousegoodlayoutpracticestoensureproperoperationofthemodule.Placingcopperorany
metalnear antenna deteriorates its operationby having effect on the matchingproperties. Metal shield around the
antennawillpreventtheradiationandthusmetalcaseshouldnotbeusedwiththemodule.Usegroundingviasseparated
max3mmapartattheedgeofgroundingareastopreventRFpenetratinginsidethePCBandcausinganunintentional
resonator.UseGNDviasallaroundthePCBedges. 
Themotherboardshouldhavenobareconductorsorviasinthisrestrictedarea,becauseitisnotcoveredbystopmask
print.Alsonocopper(planes,tracesorvias)areallowedinthisarea,becauseofmismatchingtheon‐boardantenna.
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Figure8:FSC‐BT646RestrictedArea
FollowingrecommendationshelpstoavoidEMCproblemsarisinginthedesign.Notethateachdesignisuniqueandthe
followinglistdonotconsiderallbasicdesignrulessuchasavoidingcapacitivecouplingbetweensignallines.Following
listisaimedtoavoidEMCproblemscausedbyRFpartofthemodule.Usegoodconsiderationtoavoidproblemsarising
fromdigitalsignalsinthedesign.
Ensurethatsignallineshavereturnpathsasshortaspossible.Forexampleifasignalgoestoaninnerlayerthroughavia,
alwaysusegroundviasaroundit.Locatethemtightlyandsymmetricallyaroundthesignalvias.Routingofanysensitive
signalsshouldbedoneintheinnerlayersofthePCB.Sensitivetracesshouldhaveagroundareaaboveandunderthe
line.Ifthisisnotpossible,makesurethatthereturnpathisshortbyothermeans(forexampleusingagroundlinenext
tothesignalline).
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 9.3  LayoutGuidelines(ExternalAntenna)
PlacementandPCBlayoutarecriticaltooptimizetheperformancesofamodulewithouton‐boardantennadesigns.The
tracefromtheantennaportofthemoduletoanexternalantennashouldbe50andmustbeasshortaspossibleto
avoidanyinterferenceintothetransceiverofthemodule.  ThelocationoftheexternalantennaandRF‐INportofthe
moduleshouldbekeptawayfromanynoisesourcesanddigitaltraces.Amatchingnetworkmightbeneededinbetween
theexternalantennaandRF‐INporttobettermatchtheimpedancetominimizethereturnloss.