1. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 2, February (2014), pp. 168-172, © IAEME
168
A NOVEL U-SLOT CIRCULAR MICROSTRIP ANTENNA FOR TRIPLE
BAND OPERATION
Dr. Nagraj K. Kulkarni
Government College, Gulbarga-585105, Karkataka, India
ABSTRACT
In this communication a novel design and development U slot loaded circular microstrip
antenna is presented for triple band operation. The antenna has a volume of 8 X 5 X 0.16 cm3
and
operates between the frequency range of 5.57 to 8.34 GHz giving a maximum impedance bandwidth
of 10.34 % with a peak gain of 1.85 dB. The simple commercially available glass epoxy substrate
material is used to fabricate the antenna. The microstripline feed arrangement is incorporated to
excite the antenna. The antenna shows linearly polarized broadside radiation characteristic. The
design detail of the antenna is described. The experimental results are presented and discussed. This
antenna may find applications for systems operating in C and X-band frequencies.
Keywords: Circular Microstrip Antenna, Slits, Triple Band.
1. INTRODUCTION
The modern communication systems are requiring the compact and multi featured antennas.
The microstrip antennas have become attractive candidates to suit the need of the hour in handling
the transmit/receive action in emerging communication applications like WLAN, WiMax and
HIPERLAN/2, 3G-4G mobile systems, because of their numerous inherent features like low profile,
low fabrication cost, ruggedness, planar configuration, light weight, integrability with MMICs and
ease of installation [1]. The triple and multiple band antennas are realized by many methods such as,
slot on the patch, arrays, use of stubs and shorts, various shapes of meander slots [2-5] etc. But in
this study a simple circular microstrip antenna with U shaped slot placed at the center of the patch is
used to achieve triple band operation. This kind of antenna structure is found to be rare in the
literature.
INTERNATIONAL JOURNAL OF ADVANCED RESEARCH IN ENGINEERING
AND TECHNOLOGY (IJARET)
ISSN 0976 - 6480 (Print)
ISSN 0976 - 6499 (Online)
Volume 5, Issue 2, February (2014), pp. 168-172
© IAEME: www.iaeme.com/ijaret.asp
Journal Impact Factor (2014): 7.8273 (Calculated by GISI)
www.jifactor.com
IJARET
© I A E M E

2. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 2, February (2014), pp. 168-172, © IAEME
169
2. ANTENNA DESIGN
The low cost commercially available glass epoxy substrate material of thickness h = 0.16 cm
and εr = 4.2 is used to fabricate the conventional circular microstrip antenna (CCMSA) and U
slotloaded circular microstrip antenna (UCMSA). The art work of proposed antennas is sketched
using auto-CAD software to achieve better accuracy. The antennas are etched using the
photolithography process.
Figure 1: Top view geometry of CCMSA
Figure 1 shows the top view geometry of CCMSA. The radiating patch radius R is designed
for the resonant frequency of 3.5 GHz, using the basic equations available in the literature [6]. A
quarter wave transformer of length Lt and width Wt is used between lower semicircle of the patch
and microstripline feed of length Lfeed and width Wfeed for matching their impedances. A semi
miniature-A (SMA) connector of 50 impedance is used at the tip of the microstripline to supply the
microwave power.
Figure 2: Top and bottom view geometry of UCMSA

3. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 2, February (2014), pp. 168-172, © IAEME
170
Figure 2 shows the top and bottom view geometry of UCMSA. The U shaped slot of
horizontal and vertical arm lengths h and v is placed at the center of the radiating patch. The H
shaped slot of width 1 mm having horizontal and vertical arm lengths Hh and Hv is placed on the
ground plane such that the middle point of this slot coincides with the center of the radiating patch.
The dimensions R, h, v, Hh and Hv 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. Table 1 gives the design parameters of the
CCMSA and UCMSA.
Table 1: Design parameters of the CCMSA and UCMSA
Antenna R Lfeed Wfeed Lt Wt A B H v Hh Hv
CCMSA 1.227 2.18 0.32 1.097 0.07 5 8 - - - -
UCMSA 1.227 2.18 0.32 1.097 0.07 5 8 λ0/10 λ0/2 λ0/5 λ0/2
3. RESULTS AND DISCUSSION
Vector Network Analyzer (The Agilent N5230A: A.06.04.32) is used to measure the
experimental return loss of CCMSA and UCMSA.
Figure 3 shows the variation of return loss versus frequency of CCMSA. From this figure it is
seen that, the CCMSA resonates at 3.31 GHz of frequency which is close to the designed frequency
of 3.5 GHz. The experimental bandwidth is calculated using the formula,
2 1
c
f f
Bandwidth (%) =
f
−
× 100
where, f2 and f1 are the upper and lower cut off frequencies of the resonated band when its
return loss reaches -10dB and fc is a centre frequency between f1 and f2. The bandwidth of CCMSA
is found to be 3.0 %.
Figure 3: Variation of return loss versus frequency of CCMSA

4. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 2, February (2014), pp. 168-172, © IAEME
171
Figure 4: Variation of return loss versus frequency of UCMSA
Figure 4 shows the variation of return loss versus frequency of UCMSA. It is clear from this
figure that, the antenna operates for three bands BW1 = 10.34 % (5.59-6.20 GHz), BW2 = 4.91%
(6.94-7.29 GHz) and BW3 = 6.69 % (7.8-8.34 GHz) for the resonating modes of f1, f2 and f3
respectively. The BW1 is due to the fundamental resonance of the patch. The bands BW2 and BW3
are due to the U shaped slot present on the radiating patch. Further it can be noted that, the insertion
of the H shaped slot on the ground plane helps to give the frequency ratio f2/f1 of about 1.206, which
indicates the flexibility to design dual and triple bands.
Figure 5: Radiation pattern of UCMSA measured at 5.895 GHz
The far field co-polar and cross-polar radiation patterns of the proposed antenna is measured
in its operating band. The typical radiation pattern of UCMSA measured at 5.895 GHz is shown in
Fig. 5. From this figure it is observed that, the pattern is broadsided and linearly polarized. The gain
of the proposed antenna is calculated using absolute gain method given by the relation,
( ) 0r
t
λPG (dB) = 10 log - (Gt) dB - 20 log dB
P 4πR
 
 
 
where, Pt and Pr are transmitted and received powers respectively. R is the distance between
transmitting antenna and antenna under test. The peak gain of UCMSA measured in BW1 is found to
be 3.14 dB.

5. International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
6480(Print), ISSN 0976 – 6499(Online) Volume 5, Issue 2, F
4. CONCLUSION
From this study it is concluded that,
with a maximum bandwidth of about 10.34 % and a frequency ratio of 1.206.
broadside radiation characteristics with a peak gain of
substrate material with simple design and fabrication.
operating in C and X-band frequencies.
REFERENCES
1. Constantine A. Balanis,“Antenna theory : analysis and
(1997).
2. Girish Kumar and K. P. Ray, “Broadband microstri Antennas”, Artech House, Boston, London,
2003.
3. S. V. Shynu, G. Augastin, C. K. Aanandan,
loaded reconfigurable microstrip
4. S. T. Fang and K. L. Wong, “A
a pair of narrow slots,” Microwave
5. J. H. Lu and K. L Wong “Slot
Compact dual - frequency operation”,
6. Bahl, I. J. and P. Bhartia, “Microstrip
7. M. Veereshappa and Dr.S.N Mulgi, “Corner Truncated Rectangular Slot Loaded Monopole
Microstrip Antennas for Quad
and Communication Engineering & Technology (IJECET)
pp. 165 - 171, ISSN Print: 0976
8. Nagraj Kulkarni and S. N. Mulgi, “Corner Truncated Inverted U
Rectangular Microstrip Antenna for Wlan Applications”
and Communication Engineering & Technology (IJECET)
ISSN Print: 0976- 6464, ISSN Online: 0976
9. Gangadhar P Maddani, Sameena N Mahagavin
Microstrip Array Antennas For Wide Triple Band Operation
Electronics and Communication Engineering & Technology (IJECET)
2010, pp. 53 - 61, 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.
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976
6499(Online) Volume 5, Issue 2, February (2014), pp. 168-172
172
From this study it is concluded that, UCMSA gives triple bands between 5.57 to 8.34
a maximum bandwidth of about 10.34 % and a frequency ratio of 1.206. The antenna exhibits
broadside radiation characteristics with a peak gain of 1.85 dB. The proposed antenna uses low cost
material with simple design and fabrication. This antenna may find applications
frequencies.
Constantine A. Balanis,“Antenna theory : analysis and design”, John Wiley,
Girish Kumar and K. P. Ray, “Broadband microstri Antennas”, Artech House, Boston, London,
C. K. Aanandan, P. Mohanan and K. Vasudevan,
microstrip antenna, Electron Lett. 42(2006), 316-318.
Wong, “A dual frequency equilateral – triangular microstrip
Microwave Optical Technology Letters, Vol. 23, pp. 82
“Slot Loaded meandered rectangular microstrip
operation”, Electronic Letters, Vol. 34, pp. 1048- 1050,
“Microstrip Antennas”, Artech house, New Delhi, 1980.
M. Veereshappa and Dr.S.N Mulgi, “Corner Truncated Rectangular Slot Loaded Monopole
Microstrip Antennas for Quad-Band Operation”, International Journal of Electronics
and Communication Engineering & Technology (IJECET), Volume 4, Issue 2, 20
171, ISSN Print: 0976- 6464, ISSN Online: 0976 –6472.
Nagraj Kulkarni and S. N. Mulgi, “Corner Truncated Inverted U - Slot Triple Band Tunable
strip Antenna for Wlan Applications”, International Journal of Electronics
and Communication Engineering & Technology (IJECET), Volume 3, Issue 1, 2012, pp. 1
6464, ISSN Online: 0976 –6472.
Gangadhar P Maddani, Sameena N Mahagavin and Shivasharanappa N Mulgi
Microstrip Array Antennas For Wide Triple Band Operation”, International Journal of
Electronics and Communication Engineering & Technology (IJECET), Volume
, 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 researcher in the
field of Microwave Electronics.
International Journal of Advanced Research in Engineering and Technology (IJARET), ISSN 0976 –
2, © IAEME
5.57 to 8.34 GHz
The antenna exhibits
dB. The proposed antenna uses low cost
This antenna may find applications for systems
Wiley, New York,
Girish Kumar and K. P. Ray, “Broadband microstri Antennas”, Artech House, Boston, London,
Vasudevan, C- shaped slot
microstrip antenna with
pp. 82-84, 1999.
microstrip antenna With
1050, 1998.
Artech house, New Delhi, 1980.
M. Veereshappa and Dr.S.N Mulgi, “Corner Truncated Rectangular Slot Loaded Monopole
International Journal of Electronics
, Volume 4, Issue 2, 2013,
Slot Triple Band Tunable
International Journal of Electronics
, Volume 3, Issue 1, 2012, pp. 1 - 9,
Shivasharanappa N Mulgi, “Rectangular
International Journal of
, Volume 1, Issue 1,
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
e Gulbarga. He is an active researcher in the