匹配的小环形天线rfpic™装置

Incloseproximitytothehumanbody,smallloopanten-

nasoutperformsmalldipoleandmonopoleantennas

[1].Theirsize,robustnessandlowmanufacturingcost

havemadesmallloopsthemostpopularantennafor

useinminiaturekeyfobtransmitters.Asmallloop

antennatypicallyconsistsofacircular,squareorrect-

angularcoppertraceonaprintedcircuitboard.Insome

cases,discretewiresareshapedintoloops.AN831MatchingSmallLoopAntennastorfPICDevicesEQUATION2:Author:JanvanNiekerk2MicrochipTechnologyInc.Ploss=IRlossINTRODUCTIONNotethatweassumethatthecurrentIisuniformaroundthesmallloop.ThisassumptionisonlyvalidifIncloseproximitytothehumanbody,smallloopanten-theloopcircumferenceissmallerthanonefifthofanasoutperformsmalldipolea