BANDWIDTH EFFICIENT STACKED ARRANGEMENT OF SQUARE PATCHES

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BANDWIDTH EFFICIENT STACKED ARRANGEMENT OF SQUARE PATCHES Powered By Docstoc
					International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
         INTERNATIONAL JOURNAL OF ELECTRONICS AND
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 4, July-August (2013), © IAEME
 COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)

ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)                                                     IJECET
Volume 4, Issue 4, July-August, 2013, pp. 134-139
© IAEME: www.iaeme.com/ijecet.asp                                           ©IAEME
Journal Impact Factor (2013): 5.8896 (Calculated by GISI)
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        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

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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

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

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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

        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

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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




             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


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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

       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


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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

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
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 [4] A. Rani and R.K. Dawre. “Design and Analysis of Rectangular and U Slotted Microstrip Patch
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 [5] Mohammad Tariqul Islam and Mohammed Nazmus Shakib , “High Gain Microstrip Patch
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 [6] Shekhawat, S.; Sekra, P.; Bhatnagar, D.; Saxena, V.K.; Saini, J.S.; “Stacked Arrangement
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 [7] IE3D User’s Manual, Zeland Software, Inc., Fremont. C.
 [8] Kishan Singh and Shivasharanappa N Mulgi, “Complementary-Symmetric Corner Truncated
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 [9] Sandeep Kumar, Suresh Sahni, Ugra Mohan Kumar and Devendra Singh, “Design of
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 [10] Nagraj Kulkarni and S. N. Mulgi, “Corner Truncated Inverted U - Slot Triple Band Tunable
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 [11] Anurag Sharma, Ramesh Bharti and Archanaagarwal, “Enhanced Bandwidth Slotted
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      0976- 6464, ISSN Online: 0976 –6472.




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