ANOVELMETHODFORDESIGNINGDUALFREQUENCYSLOTPATCHANTENNASWITHTWOPOLARIZATIONSWUDI1,OHISHIBASHIHIDEKAZU2,SEOKAZUYUKI2,INAGAKINAOKI31DEPARTMENTOFCOMMUNICATIONENGINEERING,SHANGHAIUNIVERSITY,SHANGHAI200072,CHINA2KOJIMAR3NAGOYAINSTITUTEOFTECHNOLOGY,NAGOYA4668555,JAPANABSTRACTTHISPAPERPRESENTSANEWMETHODFORDESIGNINGADUALFREQUENCYPATCHANTENNAWITHCIRCULARANDLINEARPOLARIZATIONSDUALFREQUENCYOPERATIONSAREBEHAVEDBYETCHINGTWONARROWSLOTSCLOSETOTHERADIATINGEDGESOFARECTANGULARPATCHTHECIRCULARPOLARIZATIONATTHELOWERRESONANTFREQUENCYOFTHEDUALFREQUENCYANTENNACANBEACHIEVEDBYSETTINGAPERTURBATIONSEGMENTATANAPPROPRIATELOCATIONINTHEPATCHELEMENT,ANDPLACINGTHEFEEDPOINTONTHEDIAGONALAXISSEVERALEXPERIMENTALRESULTSOFADESIGNEDANTENNASHOWTHEGOODCHARACTERISTICSFORCIRCULARANDLINEARPOLARIZATIONSATBOTHRESONANTFREQUENCIESCLCNUMBERTN8211DOCUMENTCODEAKEYWORDSDUALFREQUENCYSLOTPATCHANTENNASLINEARPOLARIZATIONCIRCULARPOLARIZATIONINRADARANDCOMMUNICATIONSYSTEMS,DUALFREQUENCYOPERATIONSAREOFTENREQUIREDSPECIALLY,INMODERNMOBILEGLOBALPOSITIONSYSTEMGPS,ITWILLBEDESIRABLETHATONEOFTWOFREQUENCIESISTHECIRCULARPOLARIZATIONPLANARANTENNAHASBEENINVESTIGATEDFORMULTIFREQUENCYVERYWELLSINCEITISADVANTAGEOUSINLOWCOST,LOWWEIGHTANDCONFORMABILITYEARLYDUALFREQUENCYPLANARANTENNAISMULTILAYEREDSTACKEDPATCHSTRUCTURE,ANDTHERADIATINGELEMENTISUSEDTOBECIRCULAR1,ANNULAR2,RECTANGULAR3ANDTRIANGULARPATCHES4RECENTLY,ADUALFREQUENCYANTENNAISINTRODUCEDINWHICHTHESTRUCTUREISDINGLELAYERPATCHWITHTWOSLOTSCLOSETOTHERADIATINGEDGES,ANDGOODPERFORMANCESOFSIMULTANEOUSIMPEDANCEMATCHINGANDGAINAREDEMONSTRATEDFORBOTHRESONANTFREQUENCIESHOWEVER,ALLTHECONVENTIONALINVESTIGATIONSAREONLYFORTHECASEINWHICHTHEANTENNAPOLARIZATIONISLINEAR,WHILETHEDUALFREQUENCYANTENNAWITHCIRCULARPOLARIZATIONHASNOTBEENTOUCHEDYETINTHISPAPER,WEPRESENTADESIGNMETHODOFADUALFREQUENCYANTENNAWITHCIRCULARANDLINEARPOLARIZATIONSBASEDONTHECONVENTIONALINVESTIGATIONFORTHEDUALFREQUENCYLINEARPOLARIZATIONANTENNA57,TWORESONANTFREQUENCIESAREDETERMINEDBYADJUSTINGTHESIZEOFTHEPATCHELEMENTANDTHESLOT,ASWELLASTHELOCATIONOFTHESLOTINTHEELEMENTTHEKEYTOOBTAINACIRCULARPOLARIZATIONFORANANTENNAISTOSATISFYTHECONDITIONFOREXCITINGCIRCULARPOLARIZATION,IE，THECIRCULARPOLARIZATIONCANBEEXCITEDBYSETTINGTHEPERTURBATIONSEGMENT,ATANAPPROPRIATELOCATIONINTHEPATCHELEMENT,ANDBYPLACINGTHEFEEDPOINTONTHEDIAGONALAXISWEHAVEEXPERIMENTALLYOBTAINEDTHECIRCULARANDTHELINEARPOLARIZATIONSATBOTHLOWERANDUPPERFREQUENCIES,ANDSOMEEXPERIMENTALRESULTSWILLBEDEMONSTRATEDONTHEREFLECTIONLOSSATINPUTPORTANDTHERADIATIONPATTERNOFTHEANTENNA1CONFIGURATIONOFCONVENTIONALDUALFREQUENCYPATCHANTENNAFIGURE1SHOWSACONFIGURATIONOFACONVENTIONALDUALFREQUENCYANTENNAWITHLINEARPOLARIZATIONTWORESONANTFREQUENCIESAREBEHAVEDBYETCHINGTWOSLOTSCLOSEANDPARALLELTOTHERADIATINGEDGES,ANDTHELOWERRESONANTFREQUENCYISDETERMINEDBYTHEOUTLINESIZEOFTHEPATCHELEMENT,WHILETHEUPPERRESONANTFREQUENCYISDETERMINEDBYTHESIZEANDTHEPOSITIONOFTHETWOSLOTSINTHEPATCHELEMENTBECAUSETHESLOTSARECLOSELYLOCATEDTOTHERADIATINGEDGES,AMINORPERTURBATIONOFTHETM10MODECANBEEXPECTEDASFORUNPERTURBEDTM30MODE,SINCETHESLOTSARELOCATEDWHERETHECURRENTSHALLBESIGNIFICANT,THECURRENTWILLBESTRONGLYMODIFIED,ANDAPERTURBEDTM30RADIATIONPATTERNSIMILARTOTHETM10MODECANBEOBTAINEDOUROBJECTINTHISINVESTIGATIONISTOOBTAINADUALFREQUENCYANTENNAWITHBOTHPOLARIZATIONINWHICHTHELOWERFREQUENCYISWITHACIRCULARPOLARIZATIONANDTHEUPPERFREQUENCYISWITHALINEARPOLARIZATIONFORASQUAREPATCHANTENNAWITHLENGTHOFTWOPARALLELSUBTENDSOFTHEPATCHELEMENTINORDERTOSETAPERTURBATIONSEGMENTAREAOFSFEDBYONEPORT,AWAYTOEXCITEACIRCULARPOLARIZATIONISTOEXTENDTHES,ANDPLACETHEFEEDINGPOINTONTHEDIAGONALAXISWHENANAPPROPRIATEPERTURBATIONISSELECTED,ACIRCULARPOLARIZATIONWITHAGOODAXIALRATIOCANBEOBTAINEDFIG1CONFIGURATIONOFCONVENTIONALDUALFREQUENCYANTENNA2DESIGNINGFORDUALFREQUENCYSLOTPATCHANTENNASWITHTWOPOLARIZATIONSINACONVENTIONALINVESTIGATIONFORDUALFREQUENCYWITHLINEARPOLARIZATION57,TOENSUREAGOODRADIATIONEFFICIENCYATBOTHFREQUENCIES,THEASPECTRATIOBETWEENTHETWOSIDESOFTHEPATCHISTAKENINTHERANGE1078LWANDTHELOWERFREQUENCYISDETERMINEDBY2“2/,LRRCFLTWHERECISTHEVELOCITYOFLIGHTINFREESPACE，ISTHEEFFECTIVEPERMITTIVITYGIVENBYR31210,2RYXXAND41504WLWL5“,RGTHERE610361,28074LN25185XYGYXANDTHEUPPERFREQUENCYISDETERMINEDBY72/,HRRCFLLDWTINABOVEEXPRESSION,THEPARAMETERSOFW,L,T,W,D,LAREREFERREDTOFIG2,ANDTHEISTHEDIELECTRICCONSTANTOFTHESUBSTRATEHOWEVER,INTHISSTUDY,INORDERTOOBTAINRACIRCULARPOLARIZATIONATTHELOWERRESONANTFREQUENCY,THEASPECTRATIOOFTHEOUTLINESIZEOFTHEPATCHWILLBECHANGEDSOTHATTHEMENTIONEDFORMULASABOVEWILLNOTBECOMPLETELYSATISFIEDFIG2CONFIGURATIONOFDUALFREQUENCYWEPRESENTADESIGNMETHODFORDUALFREQUENCYSLOTPATCHANTENNAWITHTWOPOLARIZATIONASFOLLOWSSTEP1DESIGNASQUAREPATCHANTENNAWITHTHEDESIRABLELOWERFREQUENCYF10BYUSINGACONVENTIONALMETHODSTEP2ETCHTWOSLOTSCLOSEANDPARALLELTOTHERADIATINGTOBEHAVETHEDUALFREQUENCIESOPERATIONBYUSINGEQ7HOWEVERTHELOWERRESONANTFREQUENCYF10WILLCHANGE,SINCETHESLOTSMODIFYTHECURRENTDISTRIBUTIONOFTHETM10STEP3ADJUSTTHESIZEOFTHEANTENNAELEMENTTOOBTAINTHEDESIREDLOWERRESONANTFREQUENCYSTEP4ADJUSTTHELENGTHANDTHEWIDTHOFTHESLOTSTOOBTAINTHEUPPERRESONANTFREQUENCYF30STEP5SETPERT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在對角線上。當(dāng)選擇了一個合適的攝動單元時，將會獲得一個具有很好軸比的圓極化天線。圖1傳統(tǒng)雙頻天線的結(jié)構(gòu)2雙頻雙極化開槽貼片天線的設(shè)計在雙頻線極化天線的傳統(tǒng)研究中，為確保在雙頻上都具有好的輻射效率，貼片兩邊的縱橫比取值范圍是（1）078LW并且低頻取決于（2）“2/,LRRCFLT其中C為自由空間的光速，為有效的介電常數(shù)，通常R（3）1210,2RYXX（4）54WLWL（5）“,RGT這里（6）10361,28074LN25185XYGYX高頻取決于（7）2/,HRRCFLLDWT上述表達式中，參數(shù)W，L，T，W，D，L參閱圖2，是基底的介電常數(shù)。然R而，在本文研究中，為在低頻端獲得一個圓極化，貼片輪廓的縱橫比將會改變，因此，上述公式將不會完全得到滿足。圖2雙頻天線的結(jié)構(gòu)我們提出了一種雙頻開槽雙極化天線的設(shè)計方法，如下所述第一步用傳統(tǒng)方法設(shè)計符合要求的低頻的方形貼片天線。第二步應(yīng)用方程（7），刻蝕兩個與輻射邊緣很近的平行槽來實現(xiàn)雙頻工作。然而，由于兩槽改變了TM10的電流分布，較低的諧振頻率F10將會改變。第三步校正天線單元的大小來獲得所想要的低頻。第四步校正兩槽的長寬來獲得較高的諧振頻率F30。第五步設(shè)置天線的攝動單元和饋點來獲得在低諧振頻率下的圓極化。3實驗結(jié)果與討論我們用實驗的方法設(shè)計了一個雙頻雙極化貼片天線。圖2展示了天線的結(jié)構(gòu)，天線的詳細說明如表1所示。在這個天線結(jié)構(gòu)中，我們延長貼片天線的L邊來來調(diào)節(jié)攝動元素，而將饋點設(shè)置在對角線上以便獲得圓極化特性。表1具有雙極化的雙皮貼片天線的詳細說明GPSVICSFREQUENCY/GHZ157525POLARIZATIONCIRCULARLINEARRETURNLOSS1515GAIN3DB5DB圖3顯示了測量到的所設(shè)計雙頻天線的反射損失，天線是由50同軸電纜反饋的。由這幅圖可見，兩個諧振頻率均在所需的1575GHZ和250GHZ兩個頻點附近，這兩個頻率將被應(yīng)用于GPS和VICS，并同時實現(xiàn)了較好的阻抗匹配在1575GHZ附近的反射損失值為17DB，在25GHZ附近的反射損失值為27DB。圖3反射損失的頻率特征圖4顯示了這個天線的軸比隨頻率變化而變化的關(guān)系?？梢钥闯鲈?575GHZ時的最佳軸比為1DB。圖4軸比的頻率特性與圖3相比，圖5顯示了測量到的天線阻抗特性。這說明在低頻1575GHZ出為實現(xiàn)圓極化而留有攝動余量。圖5輸入阻抗的頻率特性圖6顯示了在較低諧振頻率1575GHZ上設(shè)計的圓極化天線的輻射圖。圖中，我們使用單位DBIC來表示增益大小