1. International Journal of Electronics and Communication Engineering & Technology (IJECET),
INTERNATIONAL JOURNAL OF ELECTRONICS AND
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Special Issue (November, 2013), pp. 216-221
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IJECET
©IAEME
Compact Broadband Circular Microstrip Feed Slot Antenna with
Asymmetric Bevel on Ground Plane for WIMAX and WLAN Applications
Neha Goyal1, Kirti Vyas2, A K Sharma3
Department of Electronics and Communication Engineering,
College of Engineering and IT, Kukas, Jaipur (Raj.), India
2Research Scholar, Bhagwant University, Ajmer, Raj, India
1,2,3Arya
1neha_goyal100@rediffmail.com, 2kirtiVyas19@gmail.com, 3aks_370@yahoo.co.in
ABSTRACT: In this paper, design and analysis of broadband compact microstrip feed slot
antennas are being presented. The ground plane of the antenna comprises of a rectangular slot
with asymmetric bevels on its lower edge. Microstrip feed line of 50 Ω is used to excite the
antenna of 24 x 22 x 1.6 mm3 volume. It operates in broad frequency band from 3.623 GHz to
6.90 GHz and covers wireless local area network (WLAN Europe: 5.2/5.8 GHz) and worldwide
interoperability for microwave access (Wi-MAX). Antenna has stable radiation patterns with
maximum gain of 5.9 dB at 6 GHz.
I.
INTRODUCTION
Growing wireless industry requires large efforts in designing of antenna to satisfy the demands
of industry with improved performance. Antennas are required to support more than one
communication standards in one system with compact size. This indicates that the antenna
should provide stable multi-band or broadband operations to meet the demand in wireless
communication systems.
As a matter of fact, the design and development of a single antenna working in two or more
frequency bands, such as in wireless local area network (WLAN : 2.4/5.2/5.8 GHz) and
worldwideinter operability for microwave access (WiMAX: 2.3/3.5/5.8GHz) is generally of
much interest in the research area of the antenna.
Many papers have been published on design of antennas for dual and broadband operations [15]. However, most of the designs mentioned in these papers are not able to provide a multiband operation with sufficiently wide bandwidth in WLAN and WiMAX bands. The antennas
proposed in [6-10] can cover required bands but these are too large in size to be integrated
into portable devices, which limit their practical applications.
In this paper, we present a simple and compact broad band antenna suited for WLAN and WiMAX operations with appropriate gain and radiation efficiency. The antenna designed is
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
Page 216

2. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
smaller in size as compared to antennas in papers mentioned above [6-10]. The proposed
antenna consists of a rectangular slot with bevels on its lower edge on ground plane and has a
circular radiating patch. Bevels on lower edge are able to achieve a broadband operation and
better reflection coefficient. The antenna is fed by 50 Ω microstrip line, the main advantage of
using microstrip line feeding is that it is easy to fabricate.
II.
ANTENNA DESIGN
Fig. 1(a) and 1(b) show the proposed microstrip feed line circular slot antennas. These consist
of circular radiating patch on one side of the substrate and other side has a rectangular slot in
ground plane. The dielectric material used for the design is FR4 having dielectric constant
εr=4.4 with substrate thickness ‘h’=1.6 mm. Both Antennas are compact in size with
dimensions of 24 x 22 mm2. Circular radiating patch with radius of ‘R’=6 mm is fed by
microstrip line of width ‘FW’ = 3mm. The ground plane has a rectangular slot with length
‘L’=18 mm and width ‘W’=16mm. The proposed slot antennas can operate in frequency band
from 3.623 GHz to 6.90 GHz covering WLAN (Europe: 5.2/5.8 GHz) and WiMAX bands. In order
to achieve band enhancement operation and proper impedance matching, two rectangular
bevels of dimension of ‘W1’x ‘L1’ and ‘W2’x ‘L2’are etched on the both side of lower edges of
rectangular slot in ground plane as shown in Fig. 1(b). The dimensions of bevel are optimized
to withstand fabrication tolerances. The electromagnetic simulation software Ansoft HFSS 11
has been employed to perform the design and optimization process. Table 1 shows the
optimized parameters of the proposed antennas.
(a)
(b)
Fig. 1: Geometry of proposed antenna (a) Antenna 1 (Without bevels) (b) Antenna 2 (with
bevel)
SW
22
III.
SL
24
W
L
W1
L1
W2
L2
16
18
3
3
2
2
Table 1: The optimal Antenna parameters (Unit: mm)
R
6
FW
3
RESULTS AND DISCUSSIONS
Two microstrip slot antennas are designed with and without bevels. Antenna 1 (without bevel)
operates in 3.53 GHz to 6.3 GHz frequency band having reflection coefficient of -19.4 dB at 4.6
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
GHz with impedance bandwidth of 63.16% with respect to central frequency of 5.24 GHz.
Antenna 2 (with bevel) operates in 3.5 GHz to 6.9 GHz frequency band with reflection
coefficient of -23.59 dB at 4 GHz and -37.71 dB at 5.7 GHz frequency having impedance
bandwidth of 56.53% with respect to central frequency of 4.9 GHz. Comparison of reflection
coefficient of these two antennas is shown in Fig. 2. Improvement in bandwidth up to ~ 5%
with higher reflection coefficient has been observed for antenna 2 (with bevel).
Fig. 3 shows the variation of VSWR with frequency from 3.5 GHz to 6.9 GHz of the antennas
with and without bevels. We have found satisfactory VSWR, which is close to 1 for the antenna
2 (with bevel) in operational band.
Fig. 2: Simulated reflection coefficient for antenna 1 (without bevel) and antenna 2 (with bevel)
Fig. 3: Simulated VSWR curve for antenna 1 (without bevel) and antenna 2 (with bevel)
A. PARAMETRIC STUDIES ON REFLECTION COEFFICIENT

Variation in length and width:Effect of various radii of circular radiating patch
(antenna 2) on reflection coefficient has also been studied. Fig. 6 shows the variation of
reflection coefficient with increase in radius of circular radiating patch. It is observed
that by increase in radius of patch, bandwidth increases and reduces reflection
coefficient in operational band width. Decrease in reflection coefficient characterizes
lower fabrication tolerance.
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
Fig. 6: Effect of variation of radius ‘R’ on reflection coefficient of proposed antenna 2

Radiation Patterns: Radiation patterns of the discussed microstrip feed circular patch
antenna (with bevel) has also been drawn in polar diagrams in Fig. 7. It is noticed that
at lower frequencies of 3.5 and 4 GHz, the E plane pattern resembles the figure of ‘8’
shape. At higher frequencies of 5.2 and 5.8 GHz, the E plane pattern are slightly modified
from conventional ‘8’ shaped pattern, this may be due to the higher order modes
generating at higher frequencies. H plane pattern is omni-directional for the entire band
of operation.
(a)
(b)
(c)
(d)
Fig. 7: Radiation patterns of the proposed antenna (with bevel) in E and H plane, (a) at
3.5 GHz (b) at 4 GHz (c) at 5.2 GHz and (d) at 5.8 GHz

Variation of Gain with Frequency:Gain of the proposed antennas with and without
bevels have also been computed and shown in Fig. 8. Satisfactory gain of 3.5dB to 5.9 dB
has been achieved from 4 GHz to 6.3 GHz frequencies band. Nearly 8 to 10 % higher gain
has been found in an antenna with bevel then without bevel.
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
Fig. 8: Simulated Gain vs. Frequency curve for antenna 1(without bevel) and antenna 2(with
bevel)
IV.
CONCLUSION
An optimal microstrip slot antenna with asymmetric bevels on its lower edge on ground plane
and circular radiating patch has been proposed. Simulated results show that proposed antenna
operates at 3.5 GHz to 6.9 GHz frequency band having reflection coefficient of -23.59 dB at 4
GHz and -37.71 dB at 5.7 GHz frequency having impedance bandwidth of 56.53% with respect
to central frequency of 4.9 GHz. The stable radiation pattern with satisfactory maximum gain of
5.9 dB at 6 GHz has been obtained. The proposed compact antenna with volumetric size of 0.85
cm3 makes it a good candidate to operate in WLAN and WiMAX bands.
REFERENCES
[1] J.-Y. Sze, T.-H.Hu and T.-J. Chen “Compact dual-band annular-ring slot antenna with
meandered grounded strip” Progress In Electromagnetics Research, PIER 95, 299-308, 2009
[2]M. S. Alam, M. T. Islam, and N. Misran “A novel compact split ring slotted electromagnetic
bandgap structure for microstrip patch antenna performance enhancement” Progress In
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[3]J. J. Tiang , M. T. Islam , N. Misran, J. S. Mandeep “Circular microstrip slot antenna for dual
frequency RFID application” Progress In Electromagnetics Research, Vol. 120, 499-512, 2011
[4]Gu, J.-H., S. S. Zhong, L. L. Xue, and Z. Sun, “Dual-band monopole antenna with L-shaped
strips for 2.4/5 GHz WLAN applications," Microwave Opt. Technol. Lett., Vol. 50, 2830-2833,
2008.
[5]Djaiz, A., M. A. Habib, M. Nedil, and T. A. Denidni, “Compact CPW-fed matched dual-band
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[6]Liu, H.-W., C.-H. Ku and C.-F.Yang, “Novel CPW-fed planar monopole antenna for
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[7]Xiong, J. P., L. Liu, Y. Z. Yin, J. Chen, and Q. Ma, “Dual- band back-to-back F-shaped antenna
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[8]Ye, L. H. and Q. X. Chu, “Compact dual-band wide band antenna for WLAN/WiMAX
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International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
[9]Ryu, K.-S. and A. A. Kishk, “UWB antenna with single or dual band-notches for lower WLAN
band and upper WLAN band," IEEE Trans. Antennas Propag., Vol. 57, 3942-3950, 2009.
[10]F. Li, L.-S. Ran, G. Zhao, and Y.-C. Jiao “A compact microstrip-line-fed slot antenna with dual
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BIOGRAPHY
Neha Goyal Received B.Tech degree in Electronics and Communication
Engineering from Arya Institute of Engineering and technology , Kukas, Jaipur,
Rajasthan,India in 2009. She is pursuing her M. Tech in Digital Communication
at, Arya College of Engineering and I.T., Kukas, Jaipur, Rajasthan, India . Her
main research interests are design and optimization of microstrip slot antenna.
Kirti Vyas received a M.Tech degree in Electronics and communication from
the Malvia National Institute of Technology, Jaipur, Rajasthan, India. She is a
M.Tech coordinator at the Arya College of Engineering and I.T., Kukas, Jaipur,
Rajasthan, India. She is pursuing her Ph.D. from Bhagwant University, Ajmer.
Her main research interests are design and optimization of microstrip patch
antennas.
Dr. Arun kumar Sharma received his Ph.D. degree in 1984 from the Physics
Department of University of Jodhpur, Rajasthan, India. From 1980 to 2010, he
worked as a Scientist with Central Electronics Engineering Research Institute;
Pilani, India for various R&D projects such as Power Triodes, Dispenser
Cathodes, Surface Analysis by Auger Electron Spectroscopy, Thyratron, DBD
based VUV/UV sources, Terahertz sources. He has authored more than 90
research articles and his current research interests are in Terahertz
Communication, Microwave filters, Microstrip Antennas etc.
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
Page 221