1. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME
158
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.
INTERNATIONAL JOURNAL OF ELECTRONICS AND
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ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 5, Issue 1, January (2014), pp. 158-162
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME
159
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.

3. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME
160
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,
Impedance bandwidth (%) =
H L
C
f f
f
−
× 100 % (1)
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

4. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976
Figure 4 shows the variation of return loss versus frequency of DOS
figure it is clear that, the antenna resonates at
bandwidths BW1 = 9.25 % (4.21-4.65
GHz) and BW4 = 8.27 % (8.69-9.44 GHz).
patch, BW2 to BW4 are due to the independent resonan
on the radiating patch. Further, DOS
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
Figure 5 and 6 show the far field co
antennas are which are measured in their operating
cross polar power level is down by a maximum
polar power level. Also, it is seen that, the patterns are broadsided and linearly polarized.
construction of DOSUSMSA from
characteristics.
The gain of DOSUSMSA is calculated using the absolute gain method given by the relation,
( ) 10 log - ( ) - 20logG dB G dB dB=
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, ‘P
power transmitted by standard pyramidal horn antenna ‘P
maximum gain of SMSA and DOSUSMSA
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.
ics and Communication Engineering & Technology (IJECET),
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME
161
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 GHz), BW2 =1.7 % (5.5-5.7 GHz), BW3 =
9.44 GHz). The BW1 is due to the fundamental resonance of the
are due to the independent resonance of dual open stubs and the
r, DOSUSRMSA uses less copper area of 18.8 % when compared to
MSA by placing the dual open stubs and U slots on the radiating patch.
Radiation pattern of SMSA measured at 3.43 GHz
Radiation pattern of DOSUSMSA measured at 4.43 GHz
far field co-polar and cross-polar radiation patterns of the proposed
sured 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
polar power level. Also, it is seen that, the patterns are broadsided and linearly polarized.
MSA from SMSA does not affect the nature of broadside
calculated using the absolute gain method given by the relation,
0
( ) 10 log - ( ) - 20log
4
r
t
t
P
G dB G dB dB
P R
λ
π
   
  
  
(2)
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, ‘P
power transmitted by standard pyramidal horn antenna ‘Pt’ are measured independently
DOSUSMSA measured in its operating band is found to be
It can be noted that the gain of DOSUSMSA increases by 3.45 times more
when compared to the gain of SMSA.
ics and Communication Engineering & Technology (IJECET),
6472(Online), Volume 5, Issue 1, January (2014), © IAEME
USMSA. From this
with their respective
= 4.48% (7.20-7.53
is due to the fundamental resonance of the
the U-slot present
% when compared to
MSA by placing the dual open stubs and U slots on the radiating patch.
Radiation pattern of DOSUSMSA measured at 4.43 GHz
polar radiation patterns of the proposed
From these figures it is observed that, the
their corresponding co-
polar power level. Also, it is seen that, the patterns are broadsided and linearly polarized. Hence the
of broadside radiation
calculated using the absolute gain method given by the relation,
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
’ are measured independently. The
measured in its operating band is found to be 0.8 and
It can be noted that the gain of DOSUSMSA increases by 3.45 times more

5. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976
4. CONCLUSION
A compact, dual open stub and U slot loaded
performance for quad band operat
diagonally opposite corners of a square
patch a peak gain of 2.76 dB which is 3.45 times more when compared to the gain of SMSA
construction of DOSUSMSA from
characteristics. The DOSUSMSA is simple
material for its fabrication. This antenna may find applications in WLAN, IEEE 802.11a and systems
operating in X-band frequencies.
REFERENCES
1. Constantine A. Balanis, Antenna theory
1997.
2. Girish Kumar and K. P. Ray, Broadband microstrip
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3. J. Ollikainen, M. Fischer and P. Vainikainen,
for mobile communications, Electron Lett.
4. A. Mishra, P. Singh, N.P. Yadav, J.A. Ansari and B.R. Vishvakarma, Compactshorted
microstrip patch antenna for dual band operation, PIER C, 9 (2009),171
5. K. P. Ray and G. Kumar, Tunable
Trans Antennas Propagat 48 (2000), 1036
6. S. V. Shynu, G. Augastin, C. K. Aanandan,
loaded reconfigurable microstrip antenna,
7. Antennas: John D Kraus: MacGraw Hill Pub Co.
8. Archana Agarwal, Manish Kumar, Priyanka Jain and Shagun Maheshwari, “Tapered Circular
Microstrip Antenna with Modified Ground Plane for UWB Commun
Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4,
Issue 3, 2013, pp. 43 - 47, ISSN Print: 0976
9. P. Naveen Kumar, S.K. Naveen Kumar and S.N.Mulgi, “Design and Develo
Rectangular Microstrip Antenna for Quad and Triple Band Operation”, International Journal of
Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 3,
2013, pp. 132 - 138, ISSN Print: 0976
BIO-DATA
Dr. Nagraj K. Kulkarni
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
field of Microwave Electronics.
ics and Communication Engineering & Technology (IJECET),
6464(Print), ISSN 0976 – 6472(Online), Volume 5, Issue 1, January (2014), © IAEME
162
A compact, dual open stub and U slot loaded square microstrip antenna is designed and its
band operation is verified experimentally. By placing open stubs at two
square radiating patch with U slot embedded at
which is 3.45 times more when compared to the gain of SMSA
from SMSA does not affect nature of broad side radiation
is simple in its design and uses the low cost glass epoxy substrate
This antenna may find applications in WLAN, IEEE 802.11a and systems
Constantine A. Balanis, Antenna theory: analysis and design, John Wiley,
Broadband microstrip antennas, Artech House,
Fischer and P. Vainikainen, Thin dual resonant stacked shorted
Electron Lett. 35 (1999), 437-439.
A. Mishra, P. Singh, N.P. Yadav, J.A. Ansari and B.R. Vishvakarma, Compactshorted
microstrip patch antenna for dual band operation, PIER C, 9 (2009),171-182.
Tunable and dual band circular microstrip antenna with stubs, IEEE
Trans Antennas Propagat 48 (2000), 1036 - 1039.
C. K. Aanandan, P. Mohanan and K. Vasudevan,
reconfigurable microstrip antenna, Electron Lett. 42(2006), 316-318.
Antennas: John D Kraus: MacGraw Hill Pub Co. Ltd.
Archana Agarwal, Manish Kumar, Priyanka Jain and Shagun Maheshwari, “Tapered Circular
Microstrip Antenna with Modified Ground Plane for UWB Communications”, International
Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4,
47, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.
P. Naveen Kumar, S.K. Naveen Kumar and S.N.Mulgi, “Design and Develo
Rectangular Microstrip Antenna for Quad and Triple Band Operation”, International Journal of
Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 3,
138, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.
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
Electronics.
ics and Communication Engineering & Technology (IJECET),
6472(Online), Volume 5, Issue 1, January (2014), © IAEME
microstrip antenna is designed and its
open stubs at two
the centre of the
which is 3.45 times more when compared to the gain of SMSA. The
not affect nature of broad side radiation
cost glass epoxy substrate
This antenna may find applications in WLAN, IEEE 802.11a and systems
Wiley, New York,
Boston, London,
shorted patch antenna
A. Mishra, P. Singh, N.P. Yadav, J.A. Ansari and B.R. Vishvakarma, Compactshorted
182.
with stubs, IEEE
Vasudevan, C- shaped slot
318.
Archana Agarwal, Manish Kumar, Priyanka Jain and Shagun Maheshwari, “Tapered Circular
ications”, International
Journal of Electronics and Communication Engineering & Technology (IJECET), Volume 4,
P. Naveen Kumar, S.K. Naveen Kumar and S.N.Mulgi, “Design and Development of
Rectangular Microstrip Antenna for Quad and Triple Band Operation”, International Journal of
Electronics and Communication Engineering & Technology (IJECET), Volume 4, Issue 3,
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
researcher in the