双频宽带微带天线和分形天线的研究

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1、摘要近年束，由于通信系统向着大容量，多功能和智能化的趋势发展，微带天线的双频特性和宽带设计引起了人们很大兴趣。基于微带天线的许多优点，例如体积小，重量轻，剖面薄，易共形，易集成以及低成本等，使微带天线得到了广泛的应用。本文第一部分介绍了微带天线的辐射原理及一般微带天线的分析方法，详细分析了微带天线双频和宽频带的设计技术，得到了一种双频宽带微带天线的设计方法，即通过贴片开槽和缝隙耦合馈电得到双频宽带特性。运用基于有限元法的AnsoffHFSS软件仿真了这种双频宽带微带天线，得到了S参数仿真结果及低频段和高频段的辐射方向图，其在低频段和高频段的相对带宽

2、分别达到了12．O％和57．9％，远远高于一般的微带天线的相对带宽，而且天线在低频段和高频段的辐射特性非常相似。本文第二部分介绍了分形的概念和几种常用的分形结构，以及基于分形理论设计的分形天线。分形天线由于其局部和整体、局部与局部之问都存在形状上的自相似特性，很容易形成双频或多频段辐射。运用AnsoflHFSS软件仿真分析了二次迭代Sierpinski单极子天线在不同张角下的谐振和辐射特性。关键词：微带天线，双频，宽带，分形天线AbstractInrecentyears，therehasbeenincreasinginterestinthedual

3、frequencyandwidebandoperationofmicrostripantennas，duetothedevelopmentoflargercapacity,multi·functionsandintelligencecommunicationsystems．Microstripantennashavebeenusedinmanyfieldsfortheirinherentadvantagessuchaslightweight，thinprofile，manufacturing，packagingandinstalling．Thera

4、diationtheoryandanalysismethodofmicrostripantennaarepresentedinthefirstpartofthisthesis．Thedesigntechniqueofdualfrequencymicrostripantennaandwidebandmicrostripantennaareanalyzeddetailedly．Anoveldesignofdualandwidebandmicrostripantennaispresented．Thedualfrequencyoperationisachi

5、evedbyloadrectanglenotchineachedgesofrectangleantennaandthewidehandoperationisachievedbyaperture-stackedcouplingfeed．ThereturnlossandradiationpatternsofthisantennahavebeensimulatedbytheAnsofiHFSS，whichisfoundonFiniteElement，andthebandwidthofantennais12．0％atlowerresonantfrequen

6、cyand57．9％atupperresonantfrequency,whichiswiderthancommonlymicrostripantenna．Theantennahassimilarradiationpatternsatlowerresonantfrequencyandupperresonantfrequency．Theconceptionandsomecommonstructureoffractalarepresentedinthesecondpartofthisthesis．Becauseoftheshapeself-similar

7、itypropertyoffractalantennasbetweenparttowholeandparttopart，it’Seasytoformdual—frequencyandmulti-frequencyradiation．TheSierpinskifractalantennawithtwoiterationsandmodifiedtheflareangleissimulatedbytheAnsoflHFSS．Returnlossesandfarfieldsradiationpatternaregottenindifferentcondit

8、ions．Keywords：Micmstripantenna，dualfrequency，wideband，fractal