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    Octagon shaped slot loaded rectangular microstrip monopole antennas for Octagon shaped slot loaded rectangular microstrip monopole antennas for Document Transcript

    • INTERNATIONAL JOURNAL OF ELECTRONICS AND International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEMECOMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)ISSN 0976 – 6464(Print)ISSN 0976 – 6472(Online)Volume 4, Issue 2, March – April, 2013, pp. 158-164 IJECET© IAEME: www.iaeme.com/ijecet.aspJournal Impact Factor (2013): 5.8896 (Calculated by GISI) ©IAEMEwww.jifactor.com OCTAGON SHAPED SLOT LOADED RECTANGULAR MICROSTRIP MONOPOLE ANTENNAS FOR MULTI-BAND OPERATION AND VIRTUAL SIZE REDUCTION M. Veereshappa1 and Dr.S.N Mulgi2 1 Department of Electronics, L.V.D.College, Raichur: 584 101, Karnataka, India 2 Department of PG Studies and Research in Applied Electronics, Gulbarga University, Gulbarga 585 106, Karnataka, India ABSTRACT This paper presents the design and development of octagon shaped slot loaded rectangular microstrip monopole antenna for multi-band operation and virtual size reduction. The antenna operates for eight bands of frequencies in the frequency range of 1 to 16 GHz. If the radius of complimentary circular slot inside the octagonal is changed from 0.6 cm to 0.5 cm the antenna operates for five bands of frequencies without changing the nature of monopole radiation characteristics. The antenna gives maximum virtual side reduction of 62 % and highest gain of 11.86 dB. The proposed antennas are investigated experimentally and may find application in microwave communication systems. Keywords: microstip antenna, monopole, octagonal slot, ominidirectional, virtual size 1. INTRODUCTION Emerging trends in microwave communication systems often require antennas with compact size, simple in design, low manufacturing cost and capable of operating more than one band of frequencies. Owing to its thin profile, light weight, low cost, planar configuration and easy fabrication, the microstrip antenna is the better choice for these requirements. Number of investigations have been reported in the literature for dual, triple, and multiband operation [3-6]. Design and analysis of octagon shaped hybrid coupled microstrip antenna for multiband operation [7], octagonal microstrip antenna for RADAR and spacecraft applications [8], CPW- feed octagon shaped slot antenna for UWB application [9], bandwidth enhancement of wide slot antenna fed by CPW and microstripline [10] etc. The designs of single feed equilateral triangular microstip antennas with a virtual size reduction up to about 158
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME22 % by embedding cross slots on radiating patch [11], a square-ring microstrip antenna withtruncated corners shows 19 % virtual size reduction [12], double C-slot microstip antenna isdesigned and simulated to have a gain of 6.46 dBi and gives a virtual size reduction of 37 %[13], slotted rectangular microstip antenna has been designed to achieve maximum virtualsize reduction around 50 % [14] etc have been found in the literature. In this paper a simpletechnique has been demonstrated to construct the monopole antennas for multi-bandoperation, large virtual size reduction and high gain by loading octagon shaped slot on thepatch and changing the radius of circle inside the octagonal slot.2. DESIGN OF ANTENNA GEOMETRY The art work of the proposed antenna is sketched by using computer software Auto-CAD to achieve better accuracy and is fabricated on low cost FR4-epoxy substrate materialof thickness of h = 0.16 cm and permittivity εr = 4.4. Figure 1 shows the top view geometry of octagonal shaped slot loaded rectangularmicrostrip antenna (OSLRMA). In Fig.1 the area of the substrate is L × W cm. On the topsurface of the substrate a ground plane of height which is equal to the length of microstriplinefeed Lf is used on either sides of the microstripline with a gap of 0.1 cm. On the bottom of thesubstrate a continuous ground copper layer of height Lf is used below the microstripline. TheOSLRMA is designed for 3 GHz of frequency using the equations available for the design ofconventional rectangular microstrip antenna in the literature [2]. The length and width of therectangular patch are Lp and Wp respectively. The feed arrangement consists of quarter wavetransformer of length Lt and width Wt which is connected as a matching network between thepatch and the microstripline feed of length Lf and width Wf. A semi miniature-A (SMA)connector is used at the tip of the microstripline feed for feeding the microwave power. InFig.1 octagon shaped slot is loaded on rectangular patch of vertices X. Further a circle ofradius R is loaded inside octagon slot. Fig: 1 Top view geometry of OSLRMA 159
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEMEFigure 2 shows the geometry of modified octagonal shaped slot loaded rectangular microstripantenna (MOSLRMA). In this figure the radius of circle inside the octagon and is taken as 0.5cm. Fig: 2 Top view geometry of MOSLRMAThe other geometry of Fig. 2 remains same as that of Fig.1. The design parameters of theproposed antenna is shown in Table 1 Table 1 Designe parameters of proposed antenna Antenna L W Lp Wp Lf Wf Lt Wt X R parameter Dimensions 8.0 5.0 2.34 3.04 2.48 0.3 1.24 0.05 0.714 0.6 in cm3. EXPERIMENTAL RESULTS The antenna bandwidth over return loss less than -10 dB is tested experimentally onVector Network Analyzer (Rohde & Schwarz, Germany make ZVK model 1127.8651). Thevariation of return loss verses frequency of OSLRMA is as shown in Fig. 4. From this graphthe experimental bandwidth (BW) is calculated using the equations, f −f  BW =  2 1  ×100 % (1)  fc were, f1 and f2 are the lower and upper cut of frequencies of the band respectively when itsreturn loss reaches – 10 dB and fc is the center frequency of the operating band. From thisfigure, it is found that, the antenna operates between 1 to 16 GHz and gives eight resonantmodes at f1 to f8, i.e. at 1.12, 1.29, 2.01, 4.89, 6.29, 7.41, 8.99, and 15.53 GHz. The magnitude 160
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEMEof experimental -10 dB bandwidth measured for BW1 to BW8 by using the equation (1) isfound to be 50 MHz (4.48 %), 50 MHz (3.90 %), 50 MHz (2.51 %), 80 MHz (1.63 %), 80MHz (1.26 %), 330 MHz (4.46 %), 1.62 GHz (17.25 %), and 5.32 GHz (40.06 %)respectively. The resonant mode at 1.12 GHz is due to the fundamental resonant frequency of thepatch and others modes are due to the novel geometry of OSLRMA. The multi moderesponse obtained is due to different surface currents on the patch. The fundamental resonantfrequency mode shifts from 3 GHz designed frequency to 1.12 GHz due to the couplingeffect of microstripline feed and top ground plane of OSLRMA. This shift in fundamentalfrequency gives a virtual size reduction of 62.66 % which is 12.66 % large compared to theliterature value [14]. Fig: 3 Variation of return loss versus frequency of OSLRMA Figure 4 shows the variation of return loss verses frequency of MOSLRMA. It isseen that, the antenna operates for five bands of frequencies BW9 to BW13. The magnitude ofthese operating bands measured at BW9 to BW13 is found to be 210 MHz (17.28 %), 140MHz (2.90 %), 410 MHz (5.56 %), 1.76 GHz (18.96 %), and 5.40 GHz (40.60 %)respectively. The resonating modes f1, f2, and f3 of BW1, BW2, and BW3 of Fig.3 are mergedtogether into single band BW9 as shown in Fig.4. Further from Fig.4 it is clear that, theMOSLRMA is capable of widening its operating bands when compared to the operatingbands of OSLRMA. The resonant mode at 1.12 GHz is slightly shifts towards higherfrequency side at 1.14 GHz resulting a virtual size reduction of 62 %. Fig: 4 Variation of return loss versus frequency of MOSLRMA 161
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME The gain of the proposed antennas is measured by absolute gain method. The powertransmitted ‘Pt’ by pyramidal horn antenna and power received ‘Pr’ by antenna under test(AUT) are measured independently. With the help of these experimental data, the gain (G)dB of AUT is calculated by using the formula, P   λ  (G) dB=10 log  r  - (G t ) dB - 20log  0  dB (2)  Pt   4πR Where, Gt is the gain of the pyramidal horn antenna and R is the distance between thetransmitting antenna and the AUT. Using equation (2), the maximum gain of OSLRMA andMOSLRMA measured in their operating bands is found to be 9.57, 11.86 dB respectively. Itis evident that, the MOSLRMA is capable of giving lager gain when compared to the gain ofOSLRMA. The co-polar and cross-polar radiation pattern of OSLRMA and MOSLRMA ismeasured in their operating bands. The typical radiation patterns measured at 4.83 GHz and7.27 GHz are as shown in Fig 5 to 6 respectively. The obtained patterns are ominidirectionalin nature. Fig: 5 typical radiation pattern of OSLRMA measured at 4.83 GHz Fig: 6 typical radiation pattern MOSLRMA measured at 7.27 GHz 162
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME4. CONCLUSION From the detailed experimental study, it is concluded that, the OSLRMA excitedthrough microstripline feed has been designed for multi-band operation. The antenna operatesfor eight bands of frequencies in the frequency range of 1 to 16 GHz and gives virtual sizereduction of 62.66 %. If radius of circle inside the octagonal slot is varied from 0.6 cm to 0.5cm the antenna operates for five bands of frequencies in which magnitude of each operatingbands are enhanced compared to operating bands of OSLRMA. The MOSLRMA alsoenhances the gain when compared to the gain of OSLRMA. In both the cases the antennagives ominidirectional radiation characteristics. The proposed antennas are simple in theirdesign and fabrication and they use low cost FR4 substrate material. With these features theproposed antennas may find application in microwave communication systems operating inthe frequency range of 1 to 16 GHz.ACKNOWLEDGEMENTS The authors would like to thank Dept. of Sc. & Tech. (DST), Govt. of India. NewDelhi, for sanctioning Vector Network Analyzer to this Department under FIST project. Theauthors also would like to thank the authorities of Aeronautical Development Establishment(ADE), DRDO Bangalore for providing their laboratory facility to make antennameasurements on Vector Network Analyzer.REFERENCES1 Constantine A. Balanis, Antenna theory analysis and design, John Wiley, New York, 1997.2 I. J. Bahl and P. Bharatia, Microstrip antennas, Dedham, MA: Artech House, New Delhi, 1981.3 Waterhouse, R.B, and Shuley, N.V: “Dual frequency microstip rectangular patches”, Electron lett, 28(7), 1992, pp. 606-607.4 W. –C. Liu and H.-J. Liu, “Compact triple-band slotted monopole antenna with asymmetrical CPW grounds” Electron lett, 42(15), 2006, pp.840-842.5 K. G. Thomas and M. Sreenivasan,”Compact triple band antenna for WLAN, WiMAX applications,” Electron lett. Vol. 45(16), 2009, pp.811-813.6 C. W. Jung, I. Kim, Y. Kim and Y. E. Kim. “Multiband and multifeed antenna for concurrent operation mode”. Electron lett, 43(11), 2007, pp.600-602.7 A. Sahaya Anselin Nisha and T. Jayanthy, “Design and Analysis of Multiband Hybrid Coupled Octagonal Microstrip Antenna for Wireless Applications”, Res. J. Appl. Sci. Eng. Technol., 5(1): 275-279, 20138 Krishan, K., E.S. Kaur,. Investigation on octagonal microstrip antenna for RADAR & spacecraft applications. Int. J. Sci. Eng. Res., 2(11): 2011, pp.1-7.9 S. Natarajamani, S .K Behera1, S K Patra1 & R K Mishra, cpw-fed octagon shape slot antenna for UWB application, Procedings of Int. Conf. on Antenna, Propogation & Remote Sensing, 2009, Jodhpur.10 S.W. Qu, C. Ruan and B. Z. Wang, “Bandwidth enhancement of wide slot antenna fed by CPW and microstrip line,” IEEE antennas and Wireless Propagation Letters. Vol.5. 2006, pp. 15-17, 163
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME11 Gui-Han Lu; Kin-Lu Wong, “Single-feed circularly polarized equilateral- triangular microstip antenna with a tuning stub” IEEE Trans on Antennas and Propagat 48(12), 2000, pp.1869-1872.12 Gautam, A.K; Negi,R; Kanaujia,B.K, “Square-ring microstip for CP operation” Antennas and Propagation (APCAP),2012 IEEE Asia-Pacific conference proceedings, pp.263-264.13 Tlili,B. “Design of double C-slot microstip patch antenna for WiMax application” Antennas and Propagation Society International Symposium (APSURSI), 2010 IEEE conference proceedings, pp.1 - 4.14 Kumar, R.; Malathi, P.; Ganesh, G. “On the miniaturization of printed rectangular microstip antenna for wireless application.” Microwave and Optoelectronics Conference, 2007, pp.334 – 336.15 M. Veereshappa and Dr.S.N Mulgi, “Design and Development of Triple Band Ominidirectional Slotted Rectangular Microstrip Antenna”, International journal of Electronics and Communication Engineering & Technology (IJECET), Volume 3, Issue 1, 2012, pp. 17 - 22, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.16 P.A Ambresh and P.M.Hadalgi, “Slotted Inverted Patch - Rectangular Microstrip Antenna For S And L - Band Frequency”, International journal of Electronics and Communication Engineering & Technology (IJECET), Volume 1, Issue 1, 2010, pp. 44 - 52, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.17 M. Veereshappa and Dr.S.N Mulgi, “Rectangular Slot Loaded Monopole Microstrip Antennas for Triple-Band Operation and Virtual Size Reduction”, International journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 1, 2013, pp. 176 - 182, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. 164