Simulation and analysis of slot coupled patch antenna
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Simulation and analysis of slot coupled patch antenna

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    Simulation and analysis of slot coupled patch antenna Simulation and analysis of slot coupled patch antenna Document Transcript

    • International Journal of Electronics and Communication Engineering AND COMMUNICATION0976 – INTERNATIONAL JOURNAL OF ELECTRONICS & Technology (IJECET), ISSN 6464(Print), ISSN 0976 – 6472(Online) Volume& Issue 3, October- December (2012), © IAEME ENGINEERING 3, TECHNOLOGY (IJECET)ISSN 0976 – 6464(Print)ISSN 0976 – 6472(Online)Volume 3, Issue 3, October- December (2012), pp. 01-07 IJECET© IAEME: www.iaeme.com/ijecet.htmlJournal Impact Factor (2012): 3.5930 (Calculated by GISI) ©IAEMEwww.jifactor.com SIMULATION AND ANALYSIS OF SLOT-COUPLED PATCH ANTENNA AT DIFFERENT FREQUENCIES USING HFSS Tauheed Qamar1, Naseem Halder2, Mohd. Gulman Siddiqui3, Vishal Varshney4 1,2,,3,4 (Department of Electronics and Communication Engineering Amity School of Engineering And Technology, Amity University, Noida, U.p, India 1 (muhammadtauheed20@gmail.com), 2(naseem.halder@yahoo.in), 3 (mohdgulman@gmail.com ) ,4(vishal.amity08@yahoo.co.in ) ABSTRACT Microstrip patch antennas are well suited for integration in too many applications owing to their conformal nature. There are many wide banding techniques used for the MSAs. But many wide banding techniques such as using slots in the patch require an inductive coupled feed. Aperture coupled feed which makes use of thick antenna substrates is the most convenient as it has only single ground plane. Apart from this aperture coupling provides a greater radiation pattern symmetry and greater ease of design for higher impedance band width owing to a large number of design parameters. In this type of feed by using multiple patches bandwidths up to 70% are reported. This paper presents a slot coupled microstrip antenna with a rectangular patch which is located on top of two slots on the ground plane. The patch and slots are separated by an air gap and a material with low dielectric constant. The reduction in return loss is achieved as we moved to the higher frequencies. The operational frequencies are taken as from 3 GHz to 5 GHz. The comparison of s parameter plot and radiation pattern plot is done in order to achieve a better design in terms of low return loss, improved radiation pattern etc. Keywords – Air gap, Aperture coupled, High bandwidth, MSA, Radiation pattern, Return loss & S-parameter. I. INTRODUCTION Microstrip antennas have several advantages like: low cost, easy fabrication and light weight. But they suffer from disadvantages like low gain and narrow impedance bandwidth [1-5]. In high-performance aircraft, spacecraft, satellite, and missile applications, where size, weight, cost, 1
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEMEperformance, ease of installation, and aerodynamic profile are constraints, and low-profileantennas may be required. Presently there are many other government and commercialapplications, such as mobile radio and wireless communications that have similar specifications.To meet these requirements, microstrip antennas can be used [7]. These antennas are low profile,conformable to planar and non planar surfaces, simple and inexpensive to manufacture usingmodern printed-circuit technology, mechanically robust when mounted on rigid surfaces,compatible with MMIC designs, and when the particular patch shape and mode are selected, theyare very versatile in terms of resonant frequency, polarization, pattern, and impedance [6]. Inaddition, by adding loads between the patch and the ground plane, such as pins and varactordiodes, adaptive elements with variable resonant frequency, impedance, polarization, and patterncan be designed. Major operational disadvantages of microstrip antennas are their low efficiency, lowpower, high Q (sometimes in excess of 100), poor polarization purity, poor scan performance,spurious feed radiation and very narrow frequency bandwidth, which is typically only a fractionof a percent or at most a few percent. In some applications, such as in government securitysystems, narrow bandwidths are desirable [7]. However, there are methods, such as increasingthe height of the substrate that can be used to extend the efficiency (to as large as 90 percent ifsurface waves are not included) and bandwidth (up to about 35 percent). However, as the heightincreases, surface waves are introduced which usually are not desirable because they extractpower from the total available for direct radiation (space waves). The surface waves travel withinthe substrate and they are scattered at bends and surface discontinuities, such as the truncation ofthe dielectric and ground plane [8 & 13], and degrade the antenna pattern and polarizationcharacteristics. Surface waves can be eliminated, while maintaining large bandwidths, by usingcavities. Stacking, as well as other methods, of microstrip elements can also be used to increasethe bandwidth. In addition, microstrip antennas also exhibit large electromagnetic signatures at certainfrequencies outside the operating band, are rather large physically at VHF and possibly UHFfrequencies, and in large arrays there is a trade-off between bandwidth and scan volume. In orderto achieve the higher bandwidth with improved radiation efficiency and reduced return loss, slotcouple patch antenna is design in such a manner that it can easily overcome these problems [10]. II. RESEARCH METHODOLOGY The research methodology inculcates the designing of the slot couple patch antenna. Thisdesigned antenna structure is fed by using single coaxial probe feed. After feeding the antennastructure these designed antennas are further simulated over HFSS simulation software, a FETbased simulation software. These simulations are continued till an optimum result is obtained.III. INDENTATIONS AND EQUATIONS (ANTENNA DESIGN): Because of the fringing effects, electrically the patch of the microstrip antenna looksgreater than its physical dimensions. For the principal E-plane (xy-plane), this is demonstrated inFigure 1.1 where the dimensions of the patch along its length have been extended on each end by 2
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEMEa distance ∆L, which is a function of the effective dielectric constant εreff and the width-to-heightratio (W/h). ∆L ∆L L W Figure: 1.1 Physical and effective lengths of rectangular microstrip patch.A very popular and practical approximate relation for the normalized extension of the length isgiven by the following expression: ∆L/h = 0.412 {(εreff+0.3)[(W/h)+0.264]/ (εreff+0.3)[(W/h)+0.264]}…….(1) Since the length of the patch has been extended by ∆L on each side, the effective length ofthe patch is now (L = λ/2 for dominant TM010 mode with no fringing) Leffe = L+2∆L……………………………………………..(2)Based on the simplified formulation that has been described, a design procedure is outlinedwhich leads to practical designs of rectangular microstrip antennas. The procedure assumes thatthe specified information includes the dielectric constant of the substrate (εr), the resonantfrequency (fr), and the height of the substrate h. The procedure is as follows: Specify: εr, fr (inHz), and h. Determine: W, LDesign Equations:1. For an efficient radiator, a practical width that leads to good radiation efficiencies isW = ( 1/(2frඥߤ଴ ߝ଴ )ඥ2/(ߝ௥ + 1) = (‫ݒ‬଴ /2݂௥ ) ඥ2/(ߝ௥ + 1) ............................(3)Where vo is the free-space velocity of light. 3
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEME2. Determine the effective dielectric constant of the microstrip antenna.3. Once W is found using, determine the extension of the length ∆L.4. The actual length of the patch can now be determined by solving for L. ଵ ଶ௙L= – 2 ∆L……………………………………………………(4) ೝටഄೝ೐೑೑ ඥഋబ ഄబIV. STRUCTURE OF ANTENNAFigure 1.2 shows an antenna structure with a rectangular patch which is excited through two slotson the ground plane. The patch and ground plane are separated with a material (D3) with arelative permittivity of 2.2, and an air gap (D2). D1 and D3 are made from the same materialwith the same thickness. There is a 50 feed line which is divided into two 100 feed lines withdifferent lengths under the first dielectric layer under the first dielectric layer (D1). Fig: 1.2 structure of slot coupled patch antenna 4
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEMEV. Figures and Tables (RESULT) Fig: 1.3 Radiation pattern at freq 2.25 GHz Fig: 1.4 Radiation pattern at freq 3.25 GHzFig: 1.5 Radiation pattern at freq 4.5 GHz Fig: 1.6 Return loss at freq 2.25 GHz 5
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEMEFig: 1.7 Return loss at freq 3.25 GHz Fig: 1.8 Return loss at freq 4.5 GHzVI. CONCLUSION This paper presents a slot coupled patch antenna simulated at different frequencies from2.25 GHz to 4.5 GHz as shown in figures 1.3-1.8 where fig 1.3-fig 1.5 represents the radiationpattern of the antenna at 2.25,3.25 and 4.5 GHz respectively. Fig 1.6 to fig 1.8 represents returnloss characteristics of the antenna at these three frequencies respectively. The patch and theground plane are separated by a material with low dielectric constant Rogers RT/duroid 5880 andan air gap. In the first case at operating frequency 2.25 GHz the S11 versus frequency plot wecan clearly see that there is one resonance. The bandwidth is seen to be increased from 2.2625GHz to 2.3 GHz thus yielding 37.5 MHz bandwidth amounting to 1.630% bandwidth increase at2.25 GHz operating frequency. In the second case at operating frequency 3.5 GHz we can see that bandwidth is seen tobe increased from 2.18 GHz to 2.23 GHz. Hence there is an increase in the bandwidth which is50 MHz in this case and it is greater than the first case. Also we can see that the return loss isless in second case as compared to the first case. Also we can see that the radiation pattern isbetter in first case with almost no side lobes. Hence there is a tradeoff between bandwidthincrease and radiation pattern as we move from lower frequency to higher frequency. In the third case that is at operating frequency 4.5 GHz we can see that bandwidth isseen to be increased from 2.17 GHz to 2.25 GHz. Hence there is an increase in the bandwidthwhich is 80 MHz in this case and it is greater than both the first as well as second case. Also wecan see that radiation pattern get worsen as we move to higher frequencies. 6
    • International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 –6464(Print), ISSN 0976 – 6472(Online) Volume 3, Issue 3, October- December (2012), © IAEME Hence I would like to conclude that there is a tradeoff between frequency of operationand increase in bandwidth and radiation loss. Bandwidth achieved at higher frequencies is highbut the problem is that the radiation loss is also high at higher frequencies. The structure designed was only a single cavity structure but to increase the bandwidthfurther increase the number of resonant cavities in the structure which leads to other widebanding techniques such as design with stacked patches, slots on ground plane.REFERENCES1. Ghassemi, N., M. H. Neshati, and J. Rashed-Mohassel, “Investigation of multilayer probe-fedmicrostrip antenna for ultra wideband operation,” Proceeding of Asia Pacific MicrowaveConference (APMC 2007), 2135–2138, Bangkok, Thailand, Dec. 11–14, 2007.2.Milligan, T. A., Modern Antenna Design, John Wiley & Sons, Hoboken, New Jersey, 2005.3. Kumar, G. and K. P. Ray, Broadband Microstrip Antennas, Artech House, USA, 2003.4.Wong, K. L., Compact and Broadband Microstrip Antenna, John Wiley & Sones, New York,2002.5. Garg, R., P. Bhartia, I. Bahl, and A. Ittipiboon, Microstrip Antenna Design Handbook, ArtechHouse, Boston, London, 2001.6. M. P. Purchine and J. T. Aberle, “A Tunable L-Band Circular Microstrip Patch Antenna,”Microwave Journal, pp. 80, 84, 87, and 88, October 1994.7.D. M. Pozar, “Microstrip Antennas,” Proc. IEEE, Vol. 80, No. 1, pp. 79–81, January 1992.8. S. B. De Assis Fonseca and A. J. Giarola, “Microstrip Disk Antennas, Part I: Efficiency ofSpace Wave Launching,” IEEE Trans. Antennas Propagat., Vol. AP-32, No. 6, pp. 561–567,June 1984.9. S. B. De Assis Fonseca and A. J. Giarola, “Microstrip Disk Antennas, Part II: the Problem ofSurface Wave Radiation by Dielectric Truncation,” IEEE Trans. Antennas Propagat., Vol. AP-32, No. 6, pp. 568–573, June 1984.10. D. M. Pozar and D. H. Schaubert, “Scan Blindness in Infinite Phased Arrays of PrintedDipoles,” IEEE Trans. Antennas Propagat., Vol. AP-32, No. 6, pp. 602–610, June 1984.11. C. M. Krowne, “Cylindrical-Rectangular Microstrip Antenna,” IEEE Trans. AntennasPropagat., Vol. AP-31, No. 1, pp. 194–199, January 198312. J. Huang, “The Finite Ground Plane Effect on the Microstrip Antenna Radiation Patterns,”IEEE Trans. Antennas Propagat., Vol. AP-31, No. 7, pp. 649–653, July 1983.13. I. Lier and K. R. Jakobsen, “Rectangular Microstrip Patch Antennas with Infinite and FiniteGround-Plane Dimensions,” IEEE Trans. Antennas Propagat., Vol. AP-31, No. 6, pp. 978–984,November 1983. 7