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					        INTERNATIONAL and Communication Engineering & Technology (IJECET),
International Journal of ElectronicsJOURNAL OF ELECTRONICS AND
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME
 COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)                                                        IJECET
Volume 5, Issue 1, January (2014), pp. 158-162
© IAEME: www.iaeme.com/ijecet.asp                                              ©IAEME
Journal Impact Factor (2013): 5.8896 (Calculated by GISI)
www.jifactor.com




    DUAL STUB AND U - SLOT LOADED SQUARE MICROSTRIP
           ANTENNA FOR QUAD BAND OPERATION

                                       Dr. Nagraj K. Kulkarni
                           Department of Electronics, Government College,
                                 Gulbarga-585105, Karnataka, India



ABSTRACT

        In this communication, a novel dual open stub and U slot loaded square microstrip antenna is
presented as a technique for quad band operation. The proposed design has a structure of 80 × 50 ×
1.6 mm3. The antenna consists of two open stubs and U slot of optimum geometry embedded on the
square radiating patch which is exited by microstripline feed at the center. The proposed antenna
operates between 4.37-9.40 GHz of frequency. The peak gain of 2.76 dB is achieved with broadside
radiation characteristics when compared to the conventional square microstrip antenna. The design
concepts are given. The experimental results are presented and discussed. This antenna may find
applications in WLAN, IEEE 802.11a and systems operating in X-band frequencies.

Key words: Square Microstrip Antenna, Quad Band, Open Stub, U-Slot.

1. INTRODUCTION

        In the present scenario microstrip antennas are becoming more popular because of their
advantages like low profile, low volume, planar structure, compatibility to microwave and millimeter
wave integrated circuits (MMICs) and ease of installation, conformability to curved surfaces [1]. The
modern wireless communication systems like WLAN and WiMax are rapidly growing and the small
and compact antennas possessing triple quad bands is the need of the hour. Many microstrip antenna
designers put forth their efforts to meet these requirement using the techniques of variable inductive
or capacitive loads to the patch [2], loading of shorting walls at different locations [3-4], stub loading
technique [5], integrating varactor diodes to the radiating patches and changing their biasing voltages
[6] etc. But, the antenna having dual open stubs and U shaped slot on the square radiating patch
which is capable of operating at four bands with better gain is presented in this study. This kind of
geometry is found to be rare in the literature.


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International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME

2. ANTENNA DESIGN.

        The proposed antenna is fabricated using low cost glass epoxy substrate material of area A x
B, thickness h = 1.66 mm and dielectric constant εr = 4.2. The artwork of proposed antennas is
sketched using computer software auto CAD to achieve better accuracy. The bottom surface of the
substrate consists of a tight ground plane copper shielding. Photolithography process is used to
fabricate the antennas.




                            Figure 1: The top view geometry of SMSA

        Figure 1 shows the top view geometry of conventional square microstrip antenna (SMSA).
SMSA is designed for the resonant frequency of 3.5 GHz using the equations available in the
literature for the design of square microstrip antenna [7]. SMSA consists of a square radiating patch
of equal length (L) and width (W), which is excited through a microstripline of length Lf and width
Wf. A 50 semi miniature-A (SMA) connector is used at the tip of the microstripline to feed the
microwave power. A quarter wave transformer of length Lt and width Wt is incorporated to match
the impedances between lower edge of the patch and microstripline feed.




                         Figure 2: The top view geometry of DOSUSMSA

        Figure 2 shows the top view geometry of dual open stub and U slot loaded square microstrip
antenna (DOSUSMSA), which is constructed from SMSA. The open stubs of dimensions Xd and Yd
are placed at two diagonally opposite corners along the width of SMSA. The U slot of width 1 mm
is placed at the center of the square patch. Uh and Uv are the horizontal and vertical arm lengths of
the U slot. The dimensions Uh and Uv are taken in terms of λ0, where λ0, is a free space wave length
in cm corresponding to the designed frequency of 3.5 GHz. The various dimensions of the proposed
antennas are listed as in Table 1.

                                                159
International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME

              Table 1. Design Parameters of SMSA and DOSUSMSA (in cm)
      Antenna     L     W      Lf   Wf      Lt  Wt    A B Xd Yd       Uh                    Uv
       SMSA         2.04   2.04   2.18   0.32   1.09   0.06    5    8    -     -      -      -
    DOSUSMSA        2.04   2.04   2.18   0.32   1.09   0.06    5    8   0.8   0.2    λ0/6   λ0/6

3. EXPERIMENTAL RESULTS AND DISCUSSION

        The Agilent Technology make (Agilent N5230A: A.06.04.32) Vector Network Analyzer is
used to measure the experimental return loss of SMSA and DOSUSMSA.




                   Figure 3: Variation of return loss versus frequency of SMSA

        Figure 3 shows the variation of return loss versus frequency of SMSA. From this figure it is
seen that, the SMSA resonates at 3.43 GHz of frequency which is nearer to the designed frequency
of 3.5 GHz. The experimental impedance bandwidth over return loss less than -10 dB is calculated
using the formula,

                                                fH − f L
                  Impedance bandwidth (%) =              × 100 %               (1)
                                                   fC

      where, fH and fL are the upper and lower cut off frequencies of the resonating bands
when their return loss reaches -10 dB and fC is a centre frequency of fH and fL. The impedance
bandwidth is found to be 2.94 %.




                Figure 4: Variation of return loss versus frequency of DOSUSMSA


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International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME

                                                                          DOSUSMSA. From this
       Figure 4 shows the variation of return loss versus frequency of DOSUS
figure it is clear that, the antenna resonates at four bands f1, f2 f3 and f4 with their respective
                                   4.65
bandwidths BW1 = 9.25 % (4.21-4.65 GHz), BW2 =1.7 % (5.5-5.7 GHz), BW3 = 4.48% (7.20-7.53
                                  9.44
GHz) and BW4 = 8.27 % (8.69-9.44 GHz). The BW1 is due to the fundamental resonance of the
                                                resonan
patch, BW2 to BW4 are due to the independent resonance of dual open stubs and the U-slot present
                               r, DOS
on the radiating patch. Further, DOSUSRMSA uses less copper area of 18.8 % when compared to
                 MSA
copper area of SMSA by placing the dual open stubs and U slots on the radiating patch.




                    Figure 5: Radiation pattern of SMSA measured at 3.43 GHz




                 Figure 6: Radiation pattern of DOSUSMSA measured at 4.43 GHz

                                            co                 polar
       Figure 5 and 6 show the far field co-polar and cross-polar radiation patterns of the proposed
                            sured
antennas are which are measured in their operating bands. From these figures it is observed that, the
cross polar power level is down by a maximum -15dB when compared to their corresponding co-
polar power level. Also, it is seen that, the patterns are broadsided and linearly polarized. Hence the
                         MSA
construction of DOSUSMSA from SMSA does not affect the nature of broadside radiation
characteristics.
       The gain of DOSUSMSA is calculated using the absolute gain method given by the relation,

                                        Pr                       λ0 
                       (G ) dB = 10 log     - (Gt ) dB - 20 log        dB    (2)
                                        Pt                       4π R 

       where, Gt is the gain of the pyramidal horn antenna and R is the distance between the
transmitting antenna and the antenna under test (AUT). The power received by AUT, ‘Pr’ and the
                                                                            independently.
power transmitted by standard pyramidal horn antenna ‘Pt’ are measured independently The
maximum gain of SMSA and DOSUSMSA measured in its operating band is found to be 0.8 and
2.76 dB respectively. It can be noted that the gain of DOSUSMSA increases by 3.45 times more
when compared to the gain of SMSA.



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International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME

4. CONCLUSION

       A compact, dual open stub and U slot loaded square microstrip antenna is designed and its
performance for quad band operatoperation is verified experimentally. By placing open stubs at two
diagonally opposite corners of a square radiating patch with U slot embedded at the centre of the
                                                                                       SMSA.
patch a peak gain of 2.76 dB which is 3.45 times more when compared to the gain of SMSA The
construction of DOSUSMSA from SMSA does not affect nature of broad side radiation
characteristics. The DOSUSMSA is simple in its design and uses the low cost glass epoxy substrate
material for its fabrication. This antenna may find applications in WLAN, IEEE 802.11a and systems
operating in X-band frequencies.

REFERENCES

                                          theory
 1. Constantine A. Balanis, Antenna theory: analysis and design, John Wiley, New York,
    1997.
 2. Girish Kumar and K. P. Ray, Broadband microstrip antennas, Artech House, Boston, London,
    2003.
 3. J. Ollikainen, M. Fischer and P. Vainikainen, Thin dual resonant stacked shorted patch antenna
    for mobile communications, Electron Lett. 35 (1999), 437-439.
 4. A. Mishra, P. Singh, N.P. Yadav, J.A. Ansari and B.R. Vishvakarma, Compactshorted
                                                                   (2009),171 182.
    microstrip patch antenna for dual band operation, PIER C, 9 (2009),171-182.
 5. K. P. Ray and G. Kumar, Tunable and dual band circular microstrip antenna with stubs, IEEE
    Trans Antennas Propagat 48 (2000), 1036 - 1039.
 6. S. V. Shynu, G. Augastin, C. K. Aanandan, P. Mohanan and K. Vasudevan, C- shaped slot
                                                                             318.
    loaded reconfigurable microstrip antenna, Electron Lett. 42(2006), 316-318.
 7. Antennas: John D Kraus: MacGraw Hill Pub Co. Ltd.
 8. Archana Agarwal, Manish Kumar, Priyanka Jain and Shagun Maheshwari, “Tapered Circular
                                                                  Communications”,
    Microstrip Antenna with Modified Ground Plane for UWB Communications”, International
    Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4,
                                            0976
    Issue 3, 2013, pp. 43 - 47, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.
 9. P. Naveen Kumar, S.K. Naveen Kumar and S.N.Mulgi, “Design and Develo          Development of
    Rectangular Microstrip Antenna for Quad and Triple Band Operation”, International Journal of
    Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 3,
                                     0976
    2013, pp. 132 - 138, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.


BIO-DATA

               Dr. Nagraj K. Kulkarni received his M.Sc, M.Phil and Ph. D degree in Applied
               Electronics from Gulbarga University Gulbarga in the year 1995, 1996 and 2014
               respectively. He is working as an Assistant professor and Head, in the Department of
               Electronics Government Degree College Gulbarga. He is an active researcher in the
               field of Microwave Electronics.




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