Design and simulation of sierpinski carpet fractal antenna and comparision of different feeds

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Special Issue: 04 | May-2014 | NCRTECE-2014, Available @ http://www.ijret.org 35
DESIGN AND SIMULATION OF SIERPINSKI CARPET FRACTAL
ANTENNA AND COMPARISION OF DIFFERENT FEEDS
S.Ravi1
, V.Srinivasa Rao2
1
Dept. of Elect & Comm. Engineering, GITAM Institute of technology, Visakhapatnam, India
2
Dept. of Elect & Comm. Engineering, GITAM Institute of technology, Visakhapatnam, India
Abstract
The rapid growth in wireless communication has led to need of antennas with increased bandwidth, high gain and low profile. In this
paper, a multi band microstrip antenna is designed by applying fractal concept to a rectangular microstrip antenna. The antennas
properties gain, and return loss, are studied to achieve better performance. The designed antenna is compared for different feeding
techniques and the results are analyzed. This antenna is designed and simulated by using HFSS software.
Keywords—microstrip; fractal; multiband; feeding techniques.
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1. INTRODUCTION
Nowadays, in order to face the technological improvement,
humankind needs to hold up with the advancement. This
advancement has led to the development of cellular devices to
provide high-speed and high-quality information exchange
between portable devices located anywhere in the world. This
brought up many new areas of investigation; the one with
main interest for this work is the research of antennas with
fractal geometry.
An antenna is a device which is used to transmit or receive
electromagnetic waves. The IEEE Standard definitions of
terms for antenna (IEEE Std 145-1983) defines the antenna or
aerial as „„A means for radiating or receiving radio waves” [1].
The microstrip antennas are one type of antennas having
advantages like low-profile, amenable to planar and non-
planar surfaces, simple and economical to fabricate using
modern printed-circuit technology and mechanically robust.
The main problem of common antennas is that only operate at
one or two frequencies, narrowing the number of bands that
equipment is capable of supporting. Another issue is the size
of a common antenna. Due to the very minimal space that a
handset has, setting up more than one antenna is very difficult.
To help these problems, the research is focused in fractal
shaped antennas [2].
2. MICROSTRIP ANTENNAS
Microstrip antennas consist of a metallic patch on a grounded
substrate. The metallic patch can take many configurations,
rectangular and circular patches are mostly used shapes.
Microstrip antennas are increasing in popularity for use in
wireless communication because of low profile and easy to
fabricate. Therefore, they are extremely compatible for
embedded antennas in handheld devices such as cell phones.
Some of the advantages of microstrip antennas are,
 Miniature in size and low weight.
 Low profile planar configuration due to which it can be
easily mounted.
 Low fabrication cost, so they can be manufactured in
large quantity.
 Mechanically tough when mounted on rigid surfaces.
 Can be used for both linear and circular polarization.
Microstrip antennas also suffer from some draw backs
compared to conventional antennas. Some of the
disadvantages are,
 Low power handling capability.
 Narrow band width.
 Extraneous radiations from feeds and junctions.
 Surface wave excitation.
There are several feeding techniques for microstrip antennas
like, microstrip feed, inset feed, aperture coupled feed, coaxial
probe feed and proximity coupled feed. In this paper, we have
designed the antenna with microstrip feed and inset feed
techniques.
3. FRACTAL ANTENNAS
A fractal is a rough or fragmented geometric shape that can be
subdivided in parts, each of which is ( at least approximately)
a reduced-size copy of the whole. Fractals are self-similar
structures and independent of scale [3]. The fractal term was
coined in 1975 by, Benoit B. Mandelbrot who is a French
mathematician. Since Mandelbrot work a wide variety of
application areas for fractals have been found and studied, an
area in particular is fractal electrodynamics. This area
combines electromagnetic theory with fractal geometry, this
merger results in new radiation patterns, propagation and

__________________________________________________________________________________________
scattering problems. Studies in this area show that fractals
have good electromagnetic radiation patterns and advantages
over traditional antennas. These advantages are used to face
modern wireless communication problems. For example, they
can be used as compact multi-band antennas.
Fractals are known as infinitely complex because of its
similarity at all levels of magnification [4]. There are only two
types of fractals, natural fractals and mathematical fractals.
Fractal geometries can be observed all around us in our daily
life, even though we are not aware of that, these are the natural
fractals. Examples of natural fractals are: coastlines, lightning,
earthquakes, plants, vegetables, rivers, clouds, galaxies all
these examples have fractal geometry. The mathematical
fractal geometry has been known for a century and these are
based in equations that undergo iterative process. Examples of
these mathematical structures are: von Koch snowflake, the
Mandelbrot set, Sierpinski carpet, the Lorenz attractor, and the
Minkowski curve. Here we are using sierpinski carpet fractal
concept and the antenna is designed up to third iteration.
4. ANTENNA DESIGN
In order to obtain multiband characteristics and good
performance fractal concept is applied to microstrip antenna.
In this work, sierpinski fractal geometry is applied to
microstrip antenna.
The Sierpinski carpet, also known as Sierpinski gasket was
named after the Polish mathematician Sierpinski who
described its main properties in 1916[5]. It is generated
according to the IFS method. A rectangular elementary shape
is iteratively shaped, rotated and translated, then removed
from the original shape in order to generate a fractal.
The multiband microstrip antenna design starts by designing a
rectangular microstrip antenna. A rectangular microstrip
antenna is designed using RogersRT/Duroid substrate of
height 0.794 mm and relative permittivity of 2.2. The length
and width of the microstrip are calculated using formulas from
antenna theory text book[1].The location of microstrip feed to
the patch is adjusted to match with its input impedance
(usually 50 ohm). In this paper microstrip antenna with both
edge feeding and inset feeding techniques are designed for a
resonant frequency of 7.4GHz. The dimensions of microstrip
antennas are as follows,
Design Considerations
 Dielectric substrate 2.2r
 Substrate height =0.794mm
 Frequency 4.70 f GHz

mm
f
c
W
r
16
1
2
2 0




 075.2121
2
1
2
1 2
1












W
hrr
reff



mm
h
W
h
W
hL
reff
reff
732.0
8.0258.0
264.03.0
412.0 


















mm
f
c
L
reff
eff 1.14
2 0


 mmLLL eff 2.132 
5. SIMULATION RESULTS
The microstrip antenna with microstrip feed and inset feed are
designed using ANSOFT HFSS by using the above formulas
and the designed antennas are as shown Figure.1(a) and (b)
respectively and the S11 graph for both microstrip feed and
inset feed are as shown in Figure.2
(a) (b)
Fig 1 (a) Microstrip antenna with microstrip feed (b)
Microstrip antenna with inset feed
Fig.2 S11 graph for both edge feed and inset feed
Microstrip antennas.
In order obtain multiband characteristics sierpinski carpet
fractal (SCF) concept is applied to microstrip antenna.The first
iteration is obtained by removing 1/3rd
slot from centre of the
patch, the second iteration is obtained by removing 1/3rd
dimension of first slot and the third iteration is obtained by
removing 1/3rd
dimension of slot in second iteration and edge
feeding, inset feeding are applied, and they are shown in
Figure.3&4 respectively.

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(a) (b) (c)
Fig.3 (a)Microstrip antenna with SCF concept for microstrip
feed 1st
iteration(b)2nd
iteration(c)3rd
iteration.
(a) (b) (c)
Fig.4 (a) Microstrip antenna with SCF concept for inset feed
1st
iteration(b)2nd
iteration (c)3rd
iteration
The S11 graph for first iteration with microstrip feed and inset
feed are as shown in Figure.5 and Figure.6 respectively.
Fig.5 S11 graph for 1st
iteration edge fed antenna
Fig 6 S11 graph for 1st
iteration inset fed antenna
The S11 graph for second iteration with microstrip feed and
inset feed are as shown in Figure.7 and Figure.8 respectively.
Fig 7 S11 graph for 2nd
iteration edge fed antenna
Fig 8 S11 graph for 2nd
iteration inset fed antenna
The S11 graph for third iteration with microstrip feed and
inset feed are as shown in Figure.9 and Figure.10 respectively.
Fig 9 S11 graph for 3rd
iteration microstrip fed antenna.
Fig 10 S11 graph for 3rd
iteration inset feed antenna.

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Table 1: Simulated results for edge feed
Iteration Frequency bands(GHz) Gain(dB)
Microstrip
antenna
7.4 2.6
1st
6.6,8.3,9.1,10.3,12.5,13.4,
14.2
3.4
2nd
4.1,6.9,8.6,12.6,14.1 4.1
3rd
3.8,6.8,8.5,9.5,12.7,13.9,
14.5
4.4
Table 2: Simulated results for inset feed
6. CONCLUSIONS
In this paper, a multiband microstrip antenna is designed by
applying sierpinski carpet fractal concept to microstrip
antenna. The antenna is designed both for edge feeding and
inset feeding techniques up to 3rd
iteration with a scale factor
of 1/3. From the results, we can observe that by applying
fractal concept to microstrip antenna, the antenna can be
operated in multiple bands and as the number of iterations
increased, the gain of the antenna is improved. By comparing
the results, for edge feed antenna and inset feed antenna, inset
fed antenna gives more gain. The size of microstrip patch is
also reduced to 33.9% of conventional microstrip antenna.
REFERENCES
[1] C.A.Balanis, "Antenna Theory - Analysis and Design",
2nd edition, John Wiley & Sons Inc., 1997.
[2] Rahul Batra and Prof. P. L. Zade, "Design of Sierpinski
Carpet Fractal Antenna for Wireless Communication",
International Conference on VLSI,Communication and
Networks (VCAN-2011), Alwar, Rajasthan, India.
[3] Howell, J. Q.,Microstrip Antennas,„„ IEEE
Trans.Antennas Propagation, Vol. AP-23, January
1975, pp.90–93
[4] Werner, D. H. and S. Ganguly, “An overview of fractal
antenna engineering research,” IEEE Antennas and
Propagation Magazine, Vol.45, No. 1, 38-57, 2003.
[5] C. Puente, J. Romeu, R. Pous, and A. Cardama, “On
the behavior of the Sierpinski multiband fractal
antenna,” IEEE Trans. Antennas Propagat.,vol. 46, pp.
517–524, Apr. 1998.
Iteration Frequency bands(GHz) Gain(dB)
Microstrip
antenna
7.4 2.2
1st
4.1,7.3,9.1,10.3,11.9,12.9,
14.6
2.9
2nd
4.2,7.2,8.9,10.2,11.2,12.5,
14.2
3.2
3rd
4.0,7.3,8.9,10.2,11.2,11.8,
12.4,14.1
3.7

Design and simulation of sierpinski carpet fractal antenna and comparision of different feeds

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