New fractal geometry for dual band and small size microstrip patch antenna

Transcription

1 New fractal geometry for dual bad ad small size microstrip patch atea Asst. lect. Amer A. Osma Almustasiriyah Uiversity College of Egieerig Abstract A ew techique to reduce the size of microstrip patch ateas is proposed for dual bad operatio, by replacig each side of covetioal square patch ad drillig i ceter. It is foud that, the resoat frequecy of the atea ca be greatly lowered (from 1.44 GHz to GHz), for the higher iteratio order. Ad this property ca be utilized to reduce the size of the microstrip ateas (5.5 times of patch size reductio is achieved). It is also foud the variatio i gai betwee the two resoaces (ƒ0 =0.925 GHz ad ƒ1=1.8 GHz) does ot exceed 1 db, which represets good variatio for most applicatios. The patches derived from this techique ca fid applicatios i itegrated low-profile wireless commuicatio systems. Atea performace has bee evaluated usig HFSSv11software package. شكل هندسي كسوري جديد ثنائي الحزمة وصغير الحجم لهوائي شرائط دقيقة الخالصة: اقترح في هذا البحث تقنية جديدة لتقليل حجم الهوائي الشريطي الدقيق للتشغيل بحزمتي تردد وذلك باستبدال كل ضلع من إضالع الرقعة المستطيلة و ثقب مركز الرقعة بفتحة مناسبة. وقد وجد إن التردد ألرنيني لهذا الهوائي ينخفض إلى حد كبير )من 1.44 الىGHz GHz ) للمراتب العليا من التكرار لعملية االستبدال و ألثقب للرقعة. ويمكن استخدام هذه الطريقة لتقليل حجم الهوائي الشريطي)حيث تم الحصول على 5.5 مرة انخفاض تقليص في حجم الهوائي(. كذلك وجد إن التفاوت في الربح ال يتجاوز 1dB بين الحزمتين ( GHz و ) 1.8 GHz, وهذا الفرق يمثل نتيجة جيدة بالنسبة لمعظم التطبيقات.حيث يمكن لرقع الهوائيات المستنبطة من هذه التقنية العمل في التطبيقات الدوائر المتكاملة في نظام االتصاالت الالسلكية.وقد تم تقيم اداء الهوائي باستخدام برمجيات محاكاة حزمة الهياكل ذات الترددات العالية.HFSSv11 118

2 Itroductio: I recet years, as the demads of portable systems have icreased, low-profile systems have draw much iterest from researchers. I makig such low-profile commuicatio systems, the size of the atea is critical. Therefore, may kids of miiaturizatio techiques, such as usig of high dielectric substrates [1], applyig resistive or reactive loadig [2], ad icreasig the electrical legth of the atea by optimizig its shape [3], have bee proposed ad applied to microstrip patch ateas. The applicatio of fractal geometry to covetioal atea structures optimizes the shape of the ateas i order to icrease their electrical legth, which thus reduces their overall size. Because fractal geometries have two mai features i commo, space-fillig ad self-similar properties, fractal shape atea elemets preset various advatages: wide badwidth [4], multibad [5], ad reduced atea size, amog others. Koch fractal geometry exhibits well-kow features that have bee used to costruct miiaturized moopole ad loop ateas [6&7]. Other literature cocerig the techiques of reducig the size of patch atea by etchig the edges of the patch as Koch curves ad ier patch as the sierpiski carpet[8]. A compact microstrip atea practical for both the GPS/DCS dual-bad mobile commuicatio had bee preseted[9]. I this work, Koch fractal geometry has bee applied to microstrip patch ateas to reduce their overall size, ad the effectiveess of this techique is the verified through umerically aalyzed usig HFSSv.11 software package. [It is foud that as the iteratio umber icrease, the resoace frequecies become lower tha those of the zero iteratio, which represets a covetioal square patch. I other words, microstrip patch ateas employig Koch fractal islad geometry ca operate at a much lower frequecy rage while maitaiig a idetical.] Atea Desig: The fractal geometry ca be obtaied by replacig each side ad droppig i ceter of the mai square patch by a modified square slot whose iteratio factor is *side legth of mai patch. Fig(1) shows the proposed fractal shapes with differet iteratio orders. Because the shape of achieved fractal is similar to butter flay, we call them Fractal Butter Fly(FBF). 119

3 A B C D Fig(1). Geometries of the proposed ovel fractal shapes combied by(0.1875*side legth of mai patch). A_Zero iteratio, B_ First iteratio, C_ Secod iteratio, D_ Third iteratio Fig.(2) shows the simulated cofiguratio of proposed small_size patch atea with third iteratio order usig HFSSv.11, ad the cofiguratio of order ateas with differet iteratio orders are same to fig.(2 ). All of these ateas are fabricated o 3.2 mm thickess substrate with relative permittivity 4.5. The legth of the square patch is 40 mm, also it ca be see as the iteratio umber icreases, the average electrical legth of the patch also icreases, just like the iductive loadig ad slot loadig,techiques reported i [10] ad [11], thus to lowerig the resoat frequecy of the proposed patch ateas. The proposed atea is cadidate for use i applicatio as global system for mobile (925 MHz ad/or 1800 MHz) commuicatio GSM. W W ω Fig.(2) Simulated cofiguratio for the proposed small_size fractal atea with third iteratio order L 120

4 Results: Four FBF atea structures, had bee modeled at the desig frequecies (0.925 ad 1.8)GHz. The computed iput retur losses of these atea patches are show i Fig.(3). This does ot prevet the possibility of other resoat bads out of this rage. Fig.(3) The calculated iput retur loss for 5 modeled fractal patches elemets. Fig.(3) the calculated iput retur loss for the 4 modeled fractal patch elemets. 121

5 Table 1: summary of the simulatio Result. Ate a type Zero iteratio First iteratio Secod iteratio Third iteratio ƒ 0 (GHz) ƒ 1 (GHz ) S11(dB ) at ƒ S11(d B) at ƒ 1 Badwidt h at ƒ 0 Badwidt h at ƒ 1 Size Reductio 3.1% % % 6.8% % 7.2% 72% 76% Gai(d Gai(d B) at ƒ 0 B) at ƒ Based o the simulated results give above, the size reductio property of the proposed fractal patch atea ca be discuss through the summarized results listed i table1. Colum1 shows the fractal atea with differet iteratio orders, colums( 2, 3),(4,5),(6,7), ad (9,10)show the simulated resoat frequecies, retur loss, badwidth, ad atea gai respectively. Colum 8 shows size reductio i percetage of the proposed patch atea (usig ovel techique) compared to their covetioal couterpart.also it ca be see from table1, the atea i first, secod, ad third iteratio order achieved %100, %100, ad %100 size reductio respectively. Ad this meas that the proposed fractal atea (third order iteratio) is more tha (o) times smaller tha the covetioal patch atea resoated at the same frequecy. From results i colum2 (o2 ad o3), it is observed that dual resoat bad are achieved i frequecy rage specified by this study. As ca be see from fig.(3) ad table1, the square patch atea (atea fractal with zero iteratio), is resoated at 1.44 GHz has oe resoat bad i the frequecy rage specified by this study. While it also observed that, whe the atea fracted with first iteratio, two bads oticed at GHz ad 2 GHz, that s mea the lower resoat frequecy 1.44 GHz (atea with zero iteratio fractal) shifted to GHz (atea with first iteratio fractal)ad ew resoat bad is occur (2GHz). Ad also the proposed fractal patch ateas i secod ad third iteratio orders, are resoated at (0.9245,1.793)GHz ad (0.925,1.8)GHz respectively. These results show the frequecy lowerig pheomeo. Also it is observed that is the resoat frequecy lowerig i retur loss (S11-10 db) effect will be isigificat whe the iteratio order becomes higher. 122

6 Ateas gai results are also carried out at their resoat frequecies, ad it is observed that the peak gai of covetioal square patch atea (zero order iteratio ) resoated at 1.44 GHz is 3dB, ad the peak gai of the proposed fractal patch ateas with secod ad third iteratio order, are (1.315, 0.87) db ad (1.078, 0.466) db, respectively. The atea peak gais is ievitable whe effective radiatio area of the proposed fractal patch ateas decreased. Fig.(4_a), shows the ormalized radiatio patters, for FBF zero iteratio (covetioal square patch)at resoace frequecy 1.44 GHz.Fig.(4_b), shows the ormalized radiatio patters, for FBF secod iteratio at resoace frequecies GHz, ad GHzit ca be show that, the variatio i gai does ot exceed 1 db whichcosidered good variatio for most applicatios. Fig.(4_c), shows the ormalized radiatio patters, for FBF third iteratio at resoace frequecies GHz, ad 1.80 GHz. Also it ca be show that, the variatio i gai does ot exceed 1 db H_ plae E_ plae Fr=1.44 GHz (a) Fr=0.9249GHz Fr=1.793 GHz (b) Fr=0.925 GHz Fr=1.8 GHz (c) Fig.(4) ormalized radiatio patters of the proposed fractal patch ateas (a), (b),ad (c). 123

7 Coclusio: From simulated results the followig poits are coclude: 1- The resoat frequecy of the fractal atea is lowered (from 1.44 GHz to GHz), that meas this property ca be used to reduce the size of the patch atea. 2- The simulated results show a maximum 5.5 times of patch size reductio is achieved by the proposed fractal ateas. 3- Small size ad dual bad (0.925 ad 1.8 GHz) operatio patch atea is proposed i this work as cadidate for global system GSM. 4- For the dual resoat frequecy achieved i secod ad third iteratio the variatio i gai betwee ƒ0 (0.925 GHz) ad ƒ1(1.8 GHz) does ot exceed 1dB, (Gai=1.078 db at ƒ0)&(gai=0.466 db at ƒ1 ) which cosider good variatio for most applicatios. 5- Wider operatig frequecy badwidth achieved at resoat frequecy 1.8 GHz (atea at third iteratio) tha that achieved at resoat frequecy 1.44 GHz (atea at zero iteratio). Refereces: [1]T.K. Lo ad Y. Hwag, Microstrip ateas of very high permittivity for persoal commuicatios, 1997 Asia Pacific Microwave Coferece, pp [2]R.A. Saiati, CAD of microstrip ateas for wireless applicatios, Artech House, Norwood, MA, [3]H.Y. Wag ad M.J. Lacaster, Aperture-coupled thi-film supercoductig meader ateas, IEEE Tras Ateas Propagat AP-47(1999), [4]P.E. Mayes, Frequecy-idepedet atea ad broad-bad derivatives thereof, Proc IEEE 80 (1992), [5]C. Puete, J. Romeu, R. Pous, ad A. Cardma, O the behavior of the Sierpiski multibad fractal atea, IEEE Tras Ateas Propagat AP-46 (1998), [6]N. Cohe ad R.G. Hohlfed, Fractal loops ad the small loop approximatio, Commuicatio Quarterly (Witer 1996), [7]Il-Kwo Kim, Jog-Gwa Yook, ad Ha-Kyu Park, Fractal-Shape Small Size Microstrip Patch Atea Wiley IterSciece ( DOI /mop , 2002 Wiley Periodicals, Ic. Microwave Opt Techol Lett 34: 15 17,

8 [8]We-lig Che, Guag-Mig wag, ad Che-Xig Zhag Small-Size Microstrip Patch Atea Combiig Koch ad Sierpiski Fractal-shapes IEEE Ateas ad wireless propagatio letter, vol.7, [9]Shu-Yu L. ad H. Kuag-Chih, 2005, A Compact Microstrip Atea for GPS ad DCS applicatio, IEEE Tras. Ateas propag., 53: [10]S. Reed, L. Desclos, C. Terret, ad S. Toutai, Size reductio of a patch atea by meas of iductive loads, Microw. Opt. Techol. Lett., vol. 29, o. 2, pp , Feb [11]L. Desclos, Size reductio of patch by meas of slots isertio, Microw. Opt. Techol. Lett., vol. 25, o. 2, pp , Feb