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1、AbstractWiththecomingofinformationage,therehasbeenanincreasingdemand,inmilitaryaswellasthecommercialapplicationsforsuchantennadesignthatpossessthesmallsize,easeoffabrication,conformal,lowcostandwidebandcapabilities.Asthemicrostripantennahastheadvantagesoflightweight,smallvolume
2、andeasytomanufacture,theyhavebeenwidelyusedinpersonalwirelesscommunication.Butthetraditionalmicrostripantennawithnarrowbandwidthisdifficulttomeettherequirementsonthefrequencybandofmoderncommunication.Therefore,toachievethemicrostripantennawithmultifrequency,broadbandhasbecomean
3、importantsubjectintheresearchofmodernantenna.Therearemanymethodsproposedtorealizetheminiaturizationandmultibandcharacteristicoftheantennas.However,thesemethodsaresospecializedthatonlysomeaspectsofthedemandcanbemetwhiletheoverallperformanceoftheantennaisdecreasedtosatisfythecomm
4、unicationsystem.Tosolvethisdilemma,thisdissertationproposesminiaturized,multi-bandandwidebandantennasbasedonfractalstructurestheoryanddiscussestheproblemsduringtheresearchoftheantennas’designasfollows.Inthispaper,chapterpresentsamulti-fractalantennastructure,Koch-likefractalcur
5、veandSierpinskiGasketaresyncretizedinminor-mainway,formingsocalledKoch-likesidedSierpinskiGasketmulti-fractaldipole.Sixmatchedbands(S11<-10dB)withmoderategainandhighefficiencyareobtainedwithinband1.5GHz—14GHz,theconsistentresultsofsimulationhaveevincedthemulti-fractalantennaspe
6、culiarpropertiesandsuperiorityoveritsmono-fractalsinimpedanceuniformity,gainpattern,efficiencyanddimension.Expectthat,theproposedantennaexhibitsresonantfrequencyat4.98GHzwithareturnlossof-38.31dBtosatisfythebandspecificationsforwirelessapplications.Theantennaexhibitsastableradi
7、ationpatternthroughouttheoperatingfrequencyrangeof3.76-5.81GHz.SoitisattractivetoPCS,UMTS,WLAN,WiFi,WiMAXandothercommunicationsystems.Thendesigntwopseudo-fractalantennaswhichbasedonregularpolygon,theresultsshowthattheproposedmicrostripantennacanbeusedfor20GHz-2.78GHzand3GHz-10.
8、8GHzfrequencyrange.Simulationresultsshowthattheantenna