Bandwidth efficient stacked arrangement of square patches

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Bandwidth efficient stacked arrangement of square patches

  1. 1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 134 BANDWIDTH EFFICIENT STACKED ARRANGEMENT OF SQUARE PATCHES Ashish Joshi1 , Nelofar Tyagi2 , Sangya Singh3 , Saumya Jaiswal4 1,2 Department of Electronics and Communication Engineering, HMR Institute of Technology and Management, Delhi-110036, India 3,4 Jayoti Vidyapeeth Women’s University, Jaipur, Rajasthan -303007, India ABSTRACT A stack arrangement of square patch antenna is proposed and analyzed in this paper. An antenna is designed on a glass epoxy FR-4 substrate. In the proposed stack arrangement there are two patches: lower & upper patch, both patches having the same dimension. There is an air gap of 0.5 mm between two patches. The lower patch is fed through probe feed with sub miniature version A (SMA) connector and the upper structure is parasitically coupled to the lower patch. Simulation results which are analyzed in this paper are return loss, input impedance, voltage standing wave ratio (VSWR) and 2-D radiation pattern. Simulation results obtained are compared with single square patch antenna of same size. This proposed antenna operates at two resonant frequencies and also has a relatively very broad impedance bandwidth (32.54%). The proposed structure is simulated using IE3D simulator software. Keywords: Permittivity, probe feed, parasitic coupling, VSWR I. INTRODUCTION The microstrip patch antennas are popularly used these days due to their small size and low cost. However they have some disadvantages like narrow bandwidth and low gain. These disadvantages reduce the practical application of microstrip antenna [1-3] So, various techniques are used to enhance the bandwidth [4-5]. Stacked arrangement of patch antenna is one of the techniques to improve the performance of antenna by enhancing the bandwidth. A stacked patch antenna is an arrangement which includes a first antenna element and a second antenna element for cooperating with the first antenna element. These antenna elements are preferably a passive parasitic element in combination with a driven element [6]. A flexible substrate is provided having first and second opposing surfaces, each respectively in contact with the first and second antenna elements. The flexible substrate preferably has a desired dielectric property to INTERNATIONAL JOURNAL OF ELECTRONICS AND COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET) ISSN 0976 – 6464(Print) ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August, 2013, pp. 134-139 © IAEME: www.iaeme.com/ijecet.asp Journal Impact Factor (2013): 5.8896 (Calculated by GISI) www.jifactor.com IJECET © I A E M E
  2. 2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 135 provide a desired capacitance between the antenna elements. One or both of the antenna elements are fixed on the respective opposing surface. In this paper, the radiation performance of stacked arrangement of modified two square patches is analyzed. The lower patch is fed through probe feed with SMA connector and the upper structure is parasitically coupled to the lower patch. The size of the upper patch and lower patch are kept same. The propose structure has been initially optimized using the Method of Moments based CAD tool IE3D [7]. This paper has IV sections, Brief introduction is given in section I. Section II describes the antenna design. Simulation results and analysis is discussed in section III and conclusion is given in section IV. II. ANTENNA DESIGN A conventional square patch having length ‘a’ =25mm designed on glass epoxy FR-4 substrate (∈r = 4.4, tan δ= 0.025, substrate thickness ‘h’ = 1.59 mm). The square patch is fed through SMA connector with associated 50 ohm feed line. This arrangement is simulated with method of moment based IE3D simulation software The proposed stacked antenna design is made up of two patches, one layer of air and a probe connected to the lower patch. The antenna structure is simulated with substrate parameter available for glass epoxy FR-4(∈r=4.4, tan δ= 0.025).The substrate thickness is 1.59 mm. The lower patch having length ‘L1’= 25 mm, an air-gap layer with dielectric permittivity 1 and thickness‘d’ = 0.5 mm is between the lower and upper patches. The upper patch having length ‘L2’= 25 mm same as lower patch. The lower patch named as driven element is feed through SMA connector and the upper patch is parasitically coupled to lower patch. III. SIMULATION RESULTS AND ANALYSIS Simulation results for single and stacked square patch arrangement are as follows: 1. Reflection Coefficient v/s Frequency The centre frequency or resonant frequency is selected as the one at which the return loss is minimum. Fig 1.1: Simulated reflection coefficient (S11) of stacked arrangement of square patches with frequency
  3. 3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 136 As shown in fig 1.1, return loss is -49.23 dB at resonant frequency 5.24 GHz and -28.89 dB at resonant frequency 6.016GHz.This stack arrangement operate at these two frequencies 5.24 and 6.016 GHz. Fig 1.2: Simulated reflection coefficient (S11) of single square patch with frequency Fig 1.2 shows return loss for single patch of same dimension, we observe that return loss is high as compared to stack. And it also operates at only one freq. instead of two frequencies as in stacked. Bandwidth can be calculated from return loss plot. For single patch impedance bandwidth is 3.73 % while for stack it is 32.54 %, means impedance bandwidth is approximately 9 times higher if proposed stack arrangement is used. 2. Input impedance v/s Frequency Fig 2.1: Simulated input impedance of stacked arrangement with frequency The simulated input impedances of stack arrangement at two resonance frequencies are (49.63 +j 0.44) ohm and (50.23 – j 1.75) ohm which suggests excellent patching between antenna and feed arrangement at both resonance frequencies
  4. 4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 137 Fig 2.2: Simulated input impedance of single square patch with frequency The simulated input impedance of single patch antenna at resonance frequency is (50.09 – j 0.20) ohm which suggests excellent patching between antenna and feed arrangement. 3. VSWR v/s Frequency Fig 3.1: Simulated VSWR variation with frequency of stacked arrangement Fig 3.2: Simulated VSWR variation with frequency of single square patch
  5. 5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 138 Fig 3.1 and 3.2 shows VSWR variations with frequency. It is observed from the both plots that VSWR values at resonant frequencies are between the desired range 0-1, which indicates very good matching between antenna and feed arrangement. 4. Radiation pattern Since a Microstrip patch antenna radiates normal to its patch surface, the elevation pattern for φ = 0 and φ = 90 degrees would be important. Fig 4.1: Elevation pattern for stacked arrangement In fig 4.1 and 4.2 elevation pattern plots are shown for stack and single patch respectively. These plots show E-plane and H-plane elevation patterns at resonant frequency. The radiation patterns in entire bandwidth are almost identical in shape and nature Fig 4.2: Elevation pattern for single patch
  6. 6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME 139 IV. DISCUSSION AND CONCLUSIONS The radiation performance of stacked arrangement of square patches is simulated by using IE3D simulation software and its performance parameters i.e. return loss, bandwidth, VSWR is compared with conventional square patch. It is realized that proposed antenna resonates at two frequencies with much improved impedance bandwidth (32.54%) than conventional square patch (3.73%). The radiation patterns in entire bandwidth are almost identical in shape and nature. The simulated performance of antenna is encouraging and hopefully after proper testing, this antenna may prove to be a suitable structure for modern communication systems. REFERENCES [1] C. A Balanis, “Antenna Theory Analysis and Design”, 4th Edition, John Wiley & Sons, New York, 2009 [2] R. Garg and P. Bhartia, Microstrip antenna handbook. Boston: Artech house, 2001 [3] Keith R. Carver and James W. Mink, “Microstrip Antenna Technology”, IEEE Transactions on Antennas and Propogation, Vol.AP-29, No.1, January 1981 [4] A. Rani and R.K. Dawre. “Design and Analysis of Rectangular and U Slotted Microstrip Patch for Satellite Communication”, International Journal of Computer Applications, Vol-12, No.7, June 2010 [5] Mohammad Tariqul Islam and Mohammed Nazmus Shakib , “High Gain Microstrip Patch Antenna”, European Journal of Scientific Research, Vol.32 No.2(2009), pp.187-193 [6] Shekhawat, S.; Sekra, P.; Bhatnagar, D.; Saxena, V.K.; Saini, J.S.; “Stacked Arrangement of Rectangular Microstrip Patches for Circularly Polarized Broadband Performance”, Antennas and Wireless Propagation Letters, IEEE ,Vol. 9 ,2010 [7] IE3D User’s Manual, Zeland Software, Inc., Fremont. C. [8] Kishan Singh and Shivasharanappa N Mulgi, “Complementary-Symmetric Corner Truncated Compact Square Microstrip Antenna for Wide Band Operation”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 1, Issue 1, 2010, pp. 99 - 106, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. [9] Sandeep Kumar, Suresh Sahni, Ugra Mohan Kumar and Devendra Singh, “Design of Circularly Polarized Microstrip Square patch Antenna for Improved Bandwidth and Directive Gain with Low Return Loss”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 2, 2013, pp. 324 - 331, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. [10] Nagraj Kulkarni and S. N. Mulgi, “Corner Truncated Inverted U - Slot Triple Band Tunable Rectangular Microstrip Antenna for Wlan Applications”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 3, Issue 1, 2012, pp. 1 - 9, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472. [11] Anurag Sharma, Ramesh Bharti and Archanaagarwal, “Enhanced Bandwidth Slotted Microstrip Patch Antenna”, International Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 2, 2013, pp. 41 - 47, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.

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