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IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com

IJERA (International journal of Engineering Research and Applications) is International online, ... peer reviewed journal. For more detail or submit your article, please visit www.ijera.com

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  • 1. Srilakshmi.A, N.V.Koteswara Rao, D.Sreenivasa Rao / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 4, June-July 2012, pp.943-946 Bandwidth Enhancement Using Figure Eight Shaped Slot Antenna Srilakshmi.A Associate professor, Vasavi college of Engineering, ECE department, Hyderabad, India N.V.Koteswara Rao Head and Professor of ECE, CBIT, Hyderabad, India D.Sreenivasa Rao Professor of ECE, JNTUH,Hyderabad , India Abstract An eight shaped annular ring slot antenna is of figure eight and a vertical reference line. The optimized presented. A simple 50 ohms microstrip line is used to results are found to be impedance bandwidth more than excite the slot. Two annular slots are linked to achieve 1GHz. A simple 50 ohms microstrip line is used to excite wide band width. Parametric Design and Analysis is the slot. carried out with permutations of the angle between the line Parametric Analysis is carried out with joining the centers of the two rings of eight shaped slot and combinations of the angle between the line joining the a vertical reference line and with permutations of the centers of the two rings of eight shaped slot and a vertical distance between the centers of the two rings of eight reference line from 15 to 90 degrees in steps of 15 degrees shaped slot. Its optimal impedance band width(S11<-10dB) and with permutations of the distance between the centers is 2. to 3.5 GHz, more than 1GHz , 55% centered at of the two rings of eight shaped slot from 7 mm to 9.5 mm 2.7GHz. in steps of 0.5mm. The Antenna Size is 35mm x 65mm x1.6mm. Its optimal impedance band width(S 11<-10dB) is Keywords Microstrip Antenna, Wideband, Annular 2.12 to 3.16 GHz, more than 1GHz , 44% centered at Ring Slot 2.3GHz at angle of rotation is 15 degrees and centre to centre distance 17mm.. The simulated and measured INTRODUCTION results are explained below. It is well known that annular ring patch antennas [1-5] and annular slot antennas[6-9] have bring interest CONFIGURATION AND DESIGN OF EIGHT because of their significant characteristics such as wide SHAPED ANNULAR RING SLOT ANTENNA bandwidth, small size, light weight and ease of fabrication. The configuration of figure eight shaped annular Normally the bandwidth for single frequency annular slot ring slot antenna is illustrated in figure1. It consists of eight is about 10%[6,9]. Several techniques have been reported shaped annular slot. The slot antenna is excited by a 50 to achieve broad band for annular slot antennas[9,10]. It ohms microstrip line to provide impedance matching. has been reported in the subsequent work [11-14], annular Normally the resonant frequencies are mainly found by slot antenna have 10-20% impedance bandwidth, which is circumference length of annular slot. wider than conventional microstrip patch antenna. The annular- slot width and the microstrip feed line However the development of wireless parameters have significant effect on antenna parameters. communications experiencing an exponential growth hence The fundamental resonant frequency of increase the need for wideband microstrip antennas. As a conventional annular circular ring slot antenna comprises result, new antennas have to developed to provide larger in the ground plane of a dielectric substrate fed by a bandwidth and this, within small dimensions. challenge microstrip conductor can be calculated according to the which arises is that the gain and bandwidth performances following[12] of an antenna are directly related to its dimensions. These 300 f0  ------------- 1 applications include WWANs, WLANs and WPANs. 2 Rm  re Usually, broad band characteristics are tough to achieve, Where Rm is the average radius of inner ring radius and because good impedance matching is difficult. outer ring radius in mm. f0 is the resonant frequency in In this paper an 8- shaped slot antenna is GHz. And  re is effective dielectric constant of annular proposed, there by increasing the surface current path and enabling wide bandwidth of the slot antenna. By adjusting ring patch is given by 2 r the parameters of the antenna parametric analysis is carried  re  ------- 2 out using HFSS software by changing the inclination angle 1  r that is angle between the line joining centers of two circles 943 | P a g e
  • 2. Srilakshmi.A, N.V.Koteswara Rao, D.Sreenivasa Rao / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 4, June-July 2012, pp.943-946To improve the impedance bandwidth one more annular RESULTS AND DISCUSSIONSlinked slot is introduced. Using below equation width of Based on the simulated results effect of angle ofthe microstrip line width for 50 ohms is calculated[15]. rotation and center to center distance of two annular slots 87 5.98h of eight shaped slot are discussed in the following section.Z0 ()  ln[ ] -----3  r  1.41 (0.8w  t ) DEPENDENCE ON THE ANGLE OFANALYSIS AND STUDY OF THE ROTATION AND CENTER TO CENTERPARAMETERS DISTANCE The Return loss plots by adjusting the rotation W angle AG and distance of separation between the centers y of rings 2Rc are shown in Figure.2. It is observed in figure.2 that impedance bandwidth for return loss below - AG 10 dB is from 2.28 GHz to 3.64 GHz when angle of rotation AG = 15 degrees and Rc =9mm, which is more than 44 % centered at 2.3GHz. % Bandwidth for different L combinations of antenna parameters is shown in figure 3. Rc Ro and in table1. Flatten gain of 4dBi is observed over the optimized band, shown in figure 4. It is also observed that Ri E plane and H plane Radiation patterns at different values of frequencies are relative omni directional shown in figure 5. 50 ohms feed line SMA Ansoft Corporation XY Plot 1 HFSSModel4-WITH AG = 15 Connector -10.00 -12.00Figure1. Geometry of the Eight shaped antenna RETURN LOSS PLOT FOR AG = 15 degrees -14.00 -16.00 -18.00 In this paper, the effects of eight shaped slot -20.00antenna parameters are discussed and analyzed using HFSS -22.00 Curve Info AG=15 fw =3.5mm h=1.6mm l=35mm Rc=7mm Ri=6. AG=15 fw =3.5mm h=1.6mm l=35mm Rc=7.5mm Ri=software which is a FEM based simulator.. Annular slot -24.00 AG=15 fw =3.5mm h=1.6mm l=35mm Rc=8mm Ri=6. AG=15 fw =3.5mm h=1.6mm l=35mm Rc=8.5mm Ri= -26.00antennas have relatively broad band characteristics AG=15 fw =3.5mm h=1.6mm l=35mm Rc=9mm Ri=6.compare to conventional patch antennas. Normally , for Ansoft Corporation 2.00 2.50 3.00 XY Plot 5 Freq [GHz] 3.50 HFSSModel2narrow slot antennas impedance bandwidth is around 10%. -10.00However for wide slots high bandwidth can be obtained, % Bandwidth -12.00because of reduced quality factor. -14.00 dB(S(LumpPort1,LumpPort1)) A single layer with 8 shaped slot is taken out ofinfinite ground plane. FR4 substrate was selected to -16.00reduce the cost, which has a relative permittivity of 4.4, -18.00 Curve Info AG=30deg h=1.6mm l=35mm Rc=7mmloss tangent of 0.01 and a thickness of 1.56 mm. The -20.00 AG=30deg h=1.6mm l=35mm Rc=7.5mground plane size was 65mmX35mm. Radius of inner ring AG=30deg h=1.6mm l=35mm Rc=8mm AG=30deg h=1.6mm l=35mm Rc=8.5mof the slot is Ri=6.5mm,Radius of the outer ring slot is -22.00taken as Ro=9.5mm. Ansoft Corporation 2.50 3.00 3.50 XY Plot 5 Freq [GHz] 4.00 4.50 HFSSModel2 The 50 ohms feed line length is fl= 19.5mm, and -10.00width is fw3mm was designed for good impedance -15.00matching. Radius of the inner slot ring is Ri=6.5 mm ,radius of the outer circle of ring is Ro=9.5 mm, separation dB(S(LumpPort1,LumpPort1)) -20.00distance between the centers of two slots is 2Rc and theangle between the line joining the centers of the two rings -25.00 Curve Infoof eight shaped slot and a vertical reference line is AG. The -30.00 AG=45deg h=1.6mm l=35mm Rc=7mmdimensions Ri,, Ro, optimized to get wider bandwidth. AG=45deg h=1.6mm l=35mm Rc=7.5m AG=45deg h=1.6mm l=35mm Rc=8mm Angle of inclination AG is varied from 15 to 90 -35.00 AG=45deg h=1.6mm l=35mm Rc=8.5mdegrees insteps of 15degrees. The half of the distance 2.50 3.00 3.50 4.00 4.50 Freq [GHz]between the centers of two linked annular rings is Rc isvaried from 7 to 9.5 mm insteps of 0.5mm. Only oneparameter is varied every time in the numerical simulation 944 | P a g e
  • 3. Srilakshmi.A, N.V.Koteswara Rao, D.Sreenivasa Rao / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.comAnsoft Corporation XY Plot 5 Vol. 2, Issue 4, June-July 2012, pp.943-946 HFSSModel2 Ansoft Corporation XY Plot 6 HFSSModel1 5.00 Curve Info -10.00 dB(GainTotal) Setup1 : Sw eep1 Phi=0deg dB(GainTotal) Setup1 : Sw eep1 -12.00 Phi=90deg 0.00 dB(S(LumpPort1,LumpPort1)) -14.00 dB(GainTotal) -16.00 -5.00 Curve Info -18.00 AG=60deg h=1.6mm l=35mm Rc=7mm Ro=9.5mm w=65m AG=60deg h=1.6mm l=35mm Rc=7.5mm Ro=9.5mm w=65 -10.00 AG=60deg h=1.6mm l=35mm Rc=8mm Ro=9.5mm w=65m -20.00 AG=60deg h=1.6mm l=35mm Rc=8.5mm Ro=9.5mm w=65 AG=60deg h=1.6mm l=35mm Rc=9mm Ro=9.5mm w=65m 2.00 2.50 3.00 3.50 4.00 4.50Ansoft Corporation Freq [GHz] XY Plot 1 HFSSModel1 -15.00 -9.00 1.00 1.50 2.00 2.50 3.00 3.50 4.00 4.50 5.00 Freq [GHz] -11.00 Figure. 4 Gain performance of the antenna -13.00Return loss for 45 degrees angle -15.00 Radiation Pattern 5 0 Curve Info -17.00 Phi=0deg Curve Info -30 30 Phi=90deg AG=75deg b=50mm fl=19.5mm fw=3.5mm h=1.6mm l=35mm Rc=7mm 10.00 -19.00 AG=75deg b=50mm fl=19.5mm fw=3.5mm h=1.6mm l=35mm Rc=7.5m 8.00 AG=75deg b=50mm fl=19.5mm fw=3.5mm h=1.6mm l=35mm Rc=8mm -60 60 -21.00 AG=75deg b=50mm fl=19.5mm fw=3.5mm h=1.6mm l=35mm Rc=8.5m 6.00 4.00 -23.00 -90 90Ansoft Corporation 2.00 2.50 3.00 XY Plot 1Freq [GHz] 3.50 4.00 HFSSModel2 4.50 -10.00 -120 120 -15.00dB(S(LumpPort1,LumpPort1)) -150 150 -180 -20.00 Curve Info -25.00 AG=90deg h=1.6mm l=35mm Rc=7mm AG=90deg h=1.6mm l=35mm Rc=7.5m Figure. 5 Radiation pattern of the antenna AG=90deg h=1.6mm l=35mm Rc=8mm AG=90deg h=1.6mm l=35mm Rc=8.5m Eplane – red, H plane – blue) AG=90deg h=1.6mm l=35mm Rc=9mm -30.00 Table 1. Band width performance of the antenna 2.00 2.50 3.00 3.50 Freq [GHz] 4.00 4.50 S.No Angle of Rc distance % BandFigure.2 Return loss plots for Angle AG = 150 Rotation (mm) Width, 300,450,600,750 for different values of Rc AG(deg) 1 15 7.5 16.47 2 15 8 24.09 3 15 8.5 41.97 4 15 9 44.06 5 30 7 10.81 6 30 7.5 18.35 7 30 8 18.02 8 30 8.5 15.93 9 30 9 13.91 10 45 7 21 11 45 7.5 18 12 45 8.25 10.97 13 90 7 18.02 14 90 7.5 18.35 15 90 8 16.82 16 90 8.5 21.6 90 9 12.8Figure.3 Bandwidth performance of the antenna Experimental Results Photographs of top view and bottom vies are show in figure 6. Fabricated antenna consists centre to centre distance between two rings is 19mm and angle of rotation is 15 degrees. VSWR vs frequency plot was shown in figure 7. From experimental results it is observed that the impedance band width is from 2 to 3.5 GHZ centered at 2.7 GHZ that is 55%. 945 | P a g e
  • 4. Srilakshmi.A, N.V.Koteswara Rao, D.Sreenivasa Rao / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 4, June-July 2012, pp.943-946 2) BATCHELOR J.C., LANGLEY R.J.: „Microstrip ring antennas operating at higher order modes for mobile applications‟,IEE Proc. H, Microw., Antennas Propag., 1995, 141, (2),pp. 151–155 3) GUO Y.X., LUK K.M., LEE K.F.: „L-probe proximity-fed annular ring microstrip antennas‟, IEEE Trans. Antennas Propag., 2001, 49, (1), pp. 19–21 4) BAO X.L., AMMANN M.J.: „Comparison of several novel annular-ring microstrip patch antennas for circular polarization‟, J. Electromag. Waves Appl., 2006, 20, (11), pp. 1427–1438 5) Parsche, Fracis Eugene, US. Patent No. 6992630, Annulal ring Antenna 6) BATCHELOR J.C., LANGLEY R.J.: „Microstrip annular ring slot antennas for mobile applicaiotns‟, Electron. Lett., 1996, 32, (18), pp. 1635–1636 7) SHARMA S.K., SHAFAI L., JACOB N.: „Investigation of wideband microstrip slot antenna‟, IEEE Trans. Antennas Propag., 2004, 52, (3), pp. 865–872Figure 6.Photograph of the fabricated antenna 8) TEHRANI H., CHANG K.: „Multifrequency operation of microstrip-fed slot-ring antennas on thin low-dielectric permittivity substrates‟, IEEE Trans. antennas Propag., 2002, 50, (9), pp. 1299– 1308 9) YOSHIMURA Y.: „A microstripline slot antenna‟, IEEE Trans. Microw. Theory Tech., 1972, 20, (11), pp. 760–762 10) HONG C.S.: „Large bandwidth circular slot at resonance with directional radiation‟, Electron. Lett., 1988, 24, (23), pp. 1449–1450 11) JANG Y.W.: „Experimental study of wideband printed annular slot antenna with cross-shaped feedline‟, Electron.Lett., 2002, 38, (22), pp. 1305– 1307 12) Wong.K.L. and T.W. Chiou, “ Broad band singleFigure 7. Return loss vs Frequency plot patch circularly polarized microstrip antenna with dual capacitively coupled feeds”. IEEE Trans.CONCLUSION Antennas Prop. Vole 49, 41-47, 2001 An eight shaped slot is implemented to achieve 13) T.-N. Chang,Wideband circularly polarised antennabroadband characteristics of the antenna. Parametric using two linked annular slots, Electronics letters,analysis to achieve wide bandwidth is investigated with June 2011 Vol. 47 No. 13permutations of the angle between the line joining the 14) Chang, T.-N., and Han, Y.-L.: „A dual-bandcenters of the two rings of eight shaped slot and a vertical circularly polarized antenna using combined C-reference line, and the distance between the centers of the shaped and L-shaped slots excited by a microstrip,two rings of eight shaped slot. Simulated results of Microwave and Optical Technologyimpedance matching and radiation patterns are discussed. Letters,Volume 53, 1041–1044, May 2011Experimental results are discussed. And experimental 15) Balanis.C.A.Antenna Theory Analysis Design,impedance band width for VSWR<2dB is achieved for the Second Edition, United states of America, Johnband of 2 to 3.5 GHZ centered at 2.7 GHZ that is 55%. Wiley &Sons 1997..p73Simulated results are good agreement with the 16) Srilakshmi.A, Koteswararao.N.V, Srinivasarao.D,experimental results. Recent Advances in Intelligent Computational Systems (RAICS), 2011 IEEE , 2011 , Page(s): 851REFERENCES – 8551) Xiulong Bao, Max Amman,Microstrip-Fed Dual- Frequency Annular-Slot Antenna Loaded by Split- Ring-Slot,IET Microw. Antennas Propag., 2009, Vol. 3, Iss. 5, pp. 757–764 946 | P a g e