A Planar Microstrip-Line Fed Elliptical Crescent Patch UWB 5.2 GHz/5.8 GHz Notch Antenna With U-Shaped Slot

Transcription

1 A Plaar Microstrip-Lie Fed Elliptical Crescet Patch UWB 5.2 GHz/5.8 GHz Notch Atea With U-Shaped Slot Jyoti R. Pada ad Rakhesh S. Kshetrimayum Departmet of Electroics ad Commuicatio Egieerig, Idia Istitute of Techology, Guwahati, Idia ( ad Abstract A plaar ultrawidebad (UWB) moopole atea with a U-shaped slot is etched i the radiatig patch for the 5.2/5.8 GHz bad-otched fuctio is preseted. The proposed atea has a elliptical crescet radiatig patch with a U-shaped slot is removed from the patch. The structure provides a wide fractioal badwidth of more the 115% ( GHz) except i the frequecy bad rage of 5.2 GHz to 5.8 GHz, which is the operatig frequecy rage of Wireless Local Area Network (WLAN). A 50-Ω microstrip-lie is used to feed the atea. The proposed atea is simple ad compact i size providig broadbad impedace matchig, cosistet radiatio patter appropriate gai characteristics withi the UWB frequecy rage. Idex Terms bad-otched characteristic, elliptical crescet patch, moopole atea, U-shaped slot, WLAN, ultrawidebad (UWB). T I. INTRODUCTION HE emergig ultrawide-bad (UWB) radio is the techology of this era of high speed digital commuicatio. After the Federal Commuicatio Commissio s (FCC) declaratio for the usage of huge badwidth from 3.1 GHz to 10.6 GHz for the commercial wireless applicatio i February 2002 [1], there is widespread urge for the research ad developmet of the UWB compoets ad systems, which could ehace the credibility of the UWB system ad UWB atea is oe of them. Last ie years researchers all over the world desiged ad proposed may UWB ateas, which are compact, low cost, less fragile, light weight ad easily icorporable i the portable ad had held devices i the UWB system. There are may challeges i the UWB atea desig ad the otable amog them are broadbad impedace matchig, appropriate gai characteristics ad stable radiatio patter. But alog with the vast operatig badwidth of the UWB atea ( GHz), there exist some arrowbad wireless services, which occupy some of the frequecy bads i the UWB bads. The most well kow amog them is wireless local area etwork (WLAN) IEEE802.11a ad HIPERLAN/2 WLAN operatig i 5-6 GHz bad. I some atea desigs, the UWB atea uses filters to otch out the iterferig bads. But the use of filters icreases the complexity of the UWB system ad also icreases the weight. Hece it is eeded to desig the UWB atea with bad-otched characteristics both i 5-6 GHz to mitigate the iterferece betwee the arrowbad wireless system ad UWB systems. Till ow may desigs of the UWB bad-otched ateas are proposed [2]- [18] to alleviate the disturbace caused by the WLAN with the UWB system. The simple ad most commoly used approach is to icorporate various shapes ad sizes of slots ito the mai radiator. I [2] a bell shaped patch with stair case structure is proposed. Apart from that two parasitic patched are prited o the substrate to provide the bad-otch characteristics. A L- shaped slot [3] is cut i the edges of mai radiator with a C- shaped i the mai radiator. A arc shaped slot is cut i the elliptical shaped patch [4], with a rectagular slot is cut i the groud plae. A rectagular tuig stub [5] is embedded i the circular aular rig, which geerates the bad-otched characteristics i the UWB spectrum. A split rig resoator (SRR) [6] is used i the mai patch for the bad otched characteristics. A rig shaped parasitic patch [8] is prited withi the cetral circular slot. The cetral circular slot is cut from the bell shaped patch. A cuttig pie with the flare agle θ is cut from the circular patch [9]. This atea is cosists of two moopoles with a small strip bar is located i betwee the two moopoles [10]. A simple arc [12] is cut i the circular radiatig patch provides the bad otch characteristic. A H- shaped structure is prited i backside of the substrate ad two rectagular slots are cut from the groud plae. The radiatig patch is rectagular oe ad fed by a microstrip lie [13]. A square shaped SRR is prited o the circular shaped radiatig elemet [14]. Two L-shaped slots are cut from the groud plae with a arc is cut from the circular radiatig patch [15]. A deep almost full shaped arc is cut i the aular circular rig [16]. A E-shaped slot is cut from the rectagular radiatig patch with a otched groud plae [17]. I this atea the circular disc is used as the radiatig elemet, which is fed by the papered microstrip lie. The groud plae is roud corered, which ehace the impedace badwidth especially at the high frequecy. I oe structure two L-shaped slot is cut from the groud plae ad i aother structure a pair of square rig resoators is created i the groud plae, which provides

2 the required the bad-otch characteristic to otch out the WLAN bad from the UWB spectrum [18]. Based o the backgroud of the structures of various UWB otch-ateas above, this paper proposes a simple ad compact microstrip lie fed plaar UWB atea with badotched characteristics i 5.5 GHz ( GHz). The badotched characteristic i the proposed atea ca be achieved by removig a U-shaped slot from the elliptical crescet metal radiatig patch. It is observed that by adjustig the total legth of the U-shaped slot to be approximately half the guided wavelegth ( λ ) of the required otch frequecy, a destructive g iterferece takes place makig the atea o-radiatig at that otch frequecy. The tuig of the cetral otch frequecy ca be doe by suitably adjustig the total legth of the U- shaped slot. The optimizatio of the desig ad the subsequet simulatio is doe by IE3D software [19]. The proposed atea provides a impedace badwidth of GHz with VSWR 2, except the badwidth of GHz for IEEE802.11a ad HIPERLAN/2 WLAN systems. The appropriate gai ad stable radiatio patters are also obtaied. I this paper, a compact UWB atea of area 44 by 44 mm 2 is first proposed. Simply by removig a U-shaped slot from the elliptical crescet-radiatig elemet, a sigle bad-otched characteristic from 5.05 to 6.09 GHz is obtaied to reduce the potetial iterferece betwee the arrowbad system ad the UWB system. Details of simulatio results ad the atea desigs are preseted to demostrate the performace of the proposed atea. Fig. 1 shows the geometry ad cofiguratio of a UWB atea. The atea (referred to as atea 1 i this paper) was fabricated o a h=1.6 mm FR4 epoxy substrate with the dielectric costat ε r =4.4 ad loss taget taδ= As show i the figure, the shape of the radiatig elemet is elliptical crescet patch. The radiatig elemet is fed by 50-Ώ microstrip trasmissio lie, which is termiated with a sub miiature A (SMA) coector for the measuremet purpose. The electromagetic software IE3D is employed to perform the desig ad optimizatio process. The desig parameters are give i the Fig.1. Fig. 2 shows the VSWR characteristics of the atea 1. The VSWR graph cuts the VSWR=2 lie at 2.73 GHz ad remais below the lie till GHz. This depicts that there is good impedace matchig betwee the microstrip trasmissio lie ad the elliptical crescet-radiatig elemet. Fig. 3 represets the gai i dbi verses frequecy. The gai icreases with the frequecy ad the maximum at 12.0 GHz. The maximum gai of atea 1 is 4.72 dbi at 12.0 GHz. II. ANTENNA DESIGN AND RESULTS A. UWB Atea Desig ad Results Fig. 2. VSWR vs. frequecy of atea 1. Fig. 3. Simulated gai (dbi) vs. frequecy of atea 1. Fig. 1. Geometry ad cofiguratio of atea 1.

3 B. Bad-Notched UWB Atea Desig ad Results Alog with the UWB spectrum ( GHz), some arrowbad systems operate. Notable amog them is IEEE a ad HIPERLAN/2 WLAN system. Hece, to mitigate the iterferece from the above arrowbad system, badotch fuctio is desirable i the UWB system. Fig. 4 shows the geometry ad dimesio of the UWB atea with bad-otch characteristic from GHz bad (deoted as atea 2). By removig a U-shaped slot from the elliptical crescet-radiatig patch of atea 1, a bad otch fuctio is created. It is oteworthy that whe the badotched structure is applied to the atea 1, there is o redesigig work eeded for the previously take dimesios. I geeral, the mai aim behid the desig methodology of the otch fuctio is to tue the total legth of the U-shaped slot approximately equal to the half guided wavelegth (λ g ) of the desired otch frequecy, which provides the iput impedace sigular. At the desired otch frequecy, the curret distributio is aroud the U-shaped slot. Hece, a destructive iterferece for the excited surface curret will occur, which causes the atea to be o-resposive at that frequecy. The iput impedace closer to the feed poit, chages abruptly makig large reflectios at the required otch frequecy. λ g c = (2) f ε eff where L is the total legth of the U-shaped slot, ε eff is the effective dielectric costat of CPW feed-lie ad c is the speed of light i free space. We ca take (1) ito cosideratio for obtaiig the total legth of the U-shaped slot at the very begiig of the desig. Fig. 5 depicts the simulated VSWR of the atea 2 for the differet N of the U-shaped slot. As observed, the adjustmet of the bad-otched frequecy ca be doe by varyig the legth (N) of the U-shaped slot. By decreasig N from 4.65 to 3.00 mm, the tip of the otched bad shifted from 5.5 GHz to 6.5 GHz.The total legth L of the U- shaped slot for the atea 2 is deoted as L=2N The performace of the simulated VSWR of the atea 2, which provides the desired ceter otch frequecy of 5.5 GHz, is show i the Fig. 6. From the figure it is very clear that, the desired filterig property is achieved by itroducig a U-shaped slot. Compared to atea 1 desig, the sigle bad-otched UWB atea effectively blocks out the 5-6 GHz ad still performs excellet impedace matchig at other frequecies of UWB bad. The tip of the desired otch bad is exactly at 5.5 GHz at the VSWR value of 5.33, which is the ceter frequecy of the WLAN bad. The otch bad stretches from 5.05 GHz to 6.09 GHz, i which whole of the WLAN bad is immersed. The atea gai of atea 2, compared to atea 1 i the etire UWB is preseted i the Fig.7, which shows a sharp decrease i gai at 5.5 GHz, which is the ceter frequecy of the WLAN bad ad good performaces at other frequecies of the UWB bad. Fig. 4. Geometry ad cofiguratio of atea 2. The expressio for the legth of the U-shaped slot for a give otch frequecy ( f ) is give by Fig. 5. Effect of legth (N) o the VSWR of the atea 2. L λ g = (1) 2 where

4 Fig. 6. Simulated VSWR of atea 2, compared to atea 1. Fig. 8. Simulated E-plae (yz-plae) radiatio patters of atea 2 at (a) 3.5 GHz, (b) 5.5 GHz, (c) 7.5 GHz ad (d) 10.5 GHz. Fig.7. Simulated gai of atea 2, compared to atea 1 Fig. 8 shows the E-plae (yz-plae) radiatio patter of the atea 2 at 3.5, 5.5, 7.5 ad 10.5 GHz respectively ad Fig. 9 shows the H-plae (zx-plae) radiatio patter of the atea 2 at 3.5, 5.5, 7.5 ad 10.5 GHz respectively The H-plae radiatio patter is purely omi-directioal at all the simulated frequecies. I the E-plae, the radiatio patter is like a small dipole leadig to a bi-directioal radiatio patter. The E-plae radiatio patter is directioal alog ad 90 0 respectively except at 3.5 GHz, 5.5 GHz ad 7.5 GHz. At 3.5 GHz ad 7.5 GHz, the E-field is tilted towards left. At 5.5 GHz, the E-field is tilted towards right. There is somehow o chage i the shape of E-plae radiatio patter at all the simulated frequecies. Hece the atea 2 exhibits stable ad costat radiatio patter at all the frequecies. Fig. 9. Simulated H-plae (zx-plae) radiatio patters of atea 2 at (a) 3.5 GHz, (b) 5.5 GHz, (c) 7.5 GHz ad (d) 10.5 GHz. III. EQUIVALENT CIRCUIT MODEL I this sectio, a equivalet circuit for the UWB otch atea is preseted to ivestigate the bad-otch mechaism

5 of the UWB atea. Coceptually, a microstrip feed-lie is represeted as a plaar trasmissio lie with characteristic impedace of 50-Ω ad the rectagular groud plae behaves as the impedace matchig etwork. Covetioally the radiatig elemet of the UWB atea ca be represeted by may RLC parallel cells i series, which is show i the Fig.10. The U-shaped slot is modelled as the series stub with the equivalet circuit of the UWB atea [21], which is show i the Fig.11.The UWB atea ca be simply represeted by a 50-Ω load resistace i the system i most cases as we kow that a atea is the last compoet of may trasmissio systems. This approximatio is valid if the atea is well matched but this cocept is ot valid for the UWB ateas. I case of UWB ateas, the large badwidth is the result of suitable overlap of several adjacet resoaces ad each resoace ca be represeted by RLC parallel circuit[20]. Approximately, the radiatig elemet of the UWB atea ca be demostrated as several parallel RLC circuits show i Fig.10.The expressio for the equivalet circuit iput impedace of the UWB atea is give by jω. Rk. Lk Ze = (3) 2 k = 1 Rk.(1 ω. Lk. Ck ) + jω. Lk The equatio (3) ca be used to evaluate the values of RLC compoets. Oly the real part of the above equatio ca be cosidered to determie the values of the RLC compoets with the expressio Rk Re = (4) 1 k = Rk.( 2 π f. Ck ) 2 π f. Lk From the simulatio by IE3D, several impedace data about the desired frequecies ca be obtaied, which icludes the datas of real part (resistace) ad imagiary part (reactace) of the iput impedace. Usig the datas of real part i the equatio (4), a iterative ad curve fittig method ca be used to calculate all the differet parameters R k, L k ad C k [20]. Fig. 10. Equivalet circuit for radiatig elemet of UWB atea. Fig. 11. Equivalet circuit model for atea 2. At 5.5 GHz, the cocetratio of curret is aroud the U- shaped slot. At the top of the slot the impedace is zero (short circuit) ad ear the atea feedig poit the impedace is very high (ope circuit). I this case, the high impedace ear the feedig poit is resposible for the desired impedace mismatch at the otch frequecy of 5.5 GHz. At 5.5 GHz, the legth L b is half the legth of the U-shaped slot L. Hece the iput impedace is very high (ope circuit) at the feedig poit, which is obvious with the trasmissio-lie-like mode. So, a destructive iterferece takes place at 5.5 GHz, causig the atea to be o resposive at the desired frequecy bad (5-6 GHz). IV. CONCLUSION To mitigate the potetial iterferece betwee the UWB systems ad arrowbad systems such as WLAN, a compact microstrip-fed plaar elliptical UWB atea with bad rejectio at WLAN frequecies has bee proposed. The relatioship betwee the total dimesio of the U-shaped slot ad the bad rejectio operatio has bee preseted. Stable radiatio patter ad costat gai i the UWB bads are obtaied. The atea preseted i this paper is expected to fid future applicatio i UWB system. REFERENCES [1] First Report ad Order, Revisio of Part 15 of the Commissio s Rule Regardig Ultra-Widebad Trasmissio systems FCC 02-48, Federal Commuicatio Commissio, [2] K. -H. Kim, Y. -J. Cho, S. -H.Hwag ad S. O. Park, Bad-otched UWB plaar moopole atea with two parasitic patches, Electro.Lett., vol. 41, o.14, pp , Jul, [3] W. Choi, K.Chug, J.Chug ad J.Choi, Compact ultra-widebad prited atea with bad-rejectio characteristics, Electro.Lett., vol. 41, o.18, pp , Sep, [4] C.-Y. Huag.,W. C.Hsia ad J. S. Kuo, Plaar ultra-widebad atea with a bad-otched characteristics, Microwave Opt. Techol. Lett., vol. 48,o.1, pp , Ja [5] Y.Gao, B. L. Ooi ad A.P. Popov, Bad-otched ultra-widebad rigmoopole atea, Microwave Opt. Techol. Lett., vol. 48,o.1, pp , Ju [6] J.Kim, C.S.Cho ad J.W.Lee, 5.2 GHz otched ultra-widebad atea usig slot-type SRR, Electro.Lett., vol. 42, o.6, pp , Mar, [7] K. -H.Kim ad S. O Park, Aalysis of the small bad-rejected atea with the parasitic strip for UWB, IEEE Tras. Ateas Propag., vol. 54, o.6, pp , Ju [8] K. -H.Kim ad S. O Park, Desig of the bad-rejected UWB atea with the rig-shaped parasitic patch, Microwave Opt. Techol. Lett., vol. 48,o.7, pp , Jul [9] C. Y.Huag ad W. C Hsia, Plaar ultra-widebad atea with a frequecy otch characteristic, Microwave Opt. Techol. Lett., vol. 49,o.2, pp , Feb [10] K.Chug, S. Hog ad J.Choi, Ultrawide-bad prited moopole atea with bad-otch filter, IET Microw. Ateas Propag., vol. 1,o.2, pp , Apr [11] C. -Y. Hog, C. W.Lig, I. Y.Tar ad S. -J. Chug, Desig of a plaar ultrawidebad atea with a ew bad-otch structure, IEEE Tras. Ateas Propag., vol. 55, o.12, pp , Dec [12] S.N.Kha, J.X.Xiog ad S. He, Low profile ad small size frequecy otched plaar moopole atea from 3.5 to GHz, Microwave Opt. Techol. Lett., vol. 50,o.11, pp , Ja [13] R. Zaker, C. Ghobadi ad J. Nouriia, Novel modified UWB plaar moopole atea with variable frequecy bad-otch fuctio, IEEE Atea Wireless Propag Lett., vol. 7, pp ,2008.

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