International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
Bandwidth and Gain Enhancement of Star-Triangular Fractal
Monopole Antenna
Harmandeep Singh #1, Simarpreet Kaur *2
#1
Assistant Professor, Dept. of CSE, F.C.E.T, Ferozepur, Punjab, India
Assistant Professor, Dept. of ECE, F.C.E.T, Ferozepur, Punjab, India
#2
Abstract-- STF antenna with slotted semi-elliptical
ground plane is considered and is modified to get
better outcome. The analysis present that optimization
of design parameters gives better results such as
Bandwidth (BW), Return loss, VSWR and Gain. The
simulation of proposed antenna is done using High
Frequency Structure Simulator (HFSS) based upon
Finite Element Method technique (FEM) i.e. Adaptive
mesh generation and is applicable over 1-30 GHz
frequency range.
novel antenna resulted in improved bandwidth and
reduced size [11].
In 2007, slotted ground was used along with
modified Sierpinski patch to improve bandwidth of
antenna [12]. Another monopole antenna was
designed for portable wireless devices having WLAN
and Wi-Max functions in 2010 [13].
In 2011, an E-shaped fractal antenna was designed
with probe feed and performance characteristics like
impedance bandwidth, return loss, far-field
characteristics, radiation pattern, efficiency and
Keywords— Antenna, Star Triangular Fractal, current distribution were investigated for this antenna
[14].
Monopole Antenna, Bandwidth
In 2013, Vorya & Nooshin considered STF (Star
Triangular Fractal) structure and reformed it so that it
can be implemented for Super Wideband applications
I. INTRODUCTION
Nowadays, technology demands wideband antennas [15]. It has been proved that results can be improved
with high directivity and miniaturized size. by varying the ground length and outer ring radius of
Application of Metamaterial into the field of antennas STF [16]. Sierpinski gasket has been incorporated in
is a successful approach. Metamaterials results in STF design and is compared with simple STF antenna
broad frequency spectrum and high radiated power [1], [17].
In this work, Star Triangular Fractal (STF) is
[2]. Defected ground structure (DGS) is also proved
to be a good approach to increase the bandwidth of designed as antenna and is upgraded to enhance the
antenna [3], [4]. Implementation of fractal geometries bandwidth and gain of antenna.
This paper consists of various Sections. Section II
in antenna design is also a successful technique in this
describes
the Design of STF Antenna, which consists
area. The term Fractal (means “fragmented” or
of
Reference
antenna design and proposed modified
“broken”) was created by a French Mathematician, B.
antenna
designs,
is followed by next Section,
B. Mandelbrot, from a Latin word “fractus”. These
composed
of
Methodology
chosen for designing and
structures are self-similar at various scales [5].
simulation
of
antenna.
After
that, the results of
Incorporation of fractals into antenna design field has
provided evidence to be very beneficial. Fractal reference and modified antennas are discussed. The
structures are of two types: deterministic (man-made work has been concluded in last Section.
geometries) and random (natural geometries) [6].
In 2000, certain properties of fractal antennas were
II. ANTENNA DESIGN AND CONFIGURATION
proved, like multiband characteristic of fractals is
The
proposed structure of STF antenna is described
because of their recursive structure and infinite long
in
Fig.
1,
consisting of three recursions of STF design,
curve can be enclosed in a very small area etc. [7], [8].
keeping
the
scaling factor at 0.5.
In 2002, Steven discussed the relationship between
multiband behavior and self-similar fractal gap
structure of Sierpinski gasket. It was proved that
certain portions of the self-similar gap structure can be
removed from the Sierpinski gasket without affecting
the multiband behavior [9].
In 2003, it was studied that the resonant properties
i.e radiation resistance, bandwidth, efficiency and
resonant frequency decreases by increase in total
Fig. 1 First three iterations of STF design
length of wire of antenna [10].
In 2006, a novel ultra wide-band printed slot Koch
fractal antenna was compared with the conventional
micro-strip fed slot antenna and it was found that
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
A. Reference Antenna
The STF antenna is designed, with the help of
parameters described below, using Ansoft HFSS as
shown in Fig. 2.
Fig. 3 Geometry of proposed modified STF Antenna
with higher outer ring radius
Fig. 2 Structure of Reference STF Antenna
The dimensional description of designed STF
antenna is revealed in the Table 1.
2) Model 2:
Model 2 STF antenna is designed by reducing the
area of model 1, shown in Fig. 4. The area reduction
in the outer ring is carried out with the help of
hexagon of radius 7.6 mm and circle of radius 7 mm,
rest of the parameters are kept same.
III. TABLE I
DIMENSIONAL DESCRIPTION OF ANTENNA
Parameter Description
L
Length of antenna
W
Width of antenna
R
Radius of external circle
r
Radius of inner circle
Lfl
Length of feed line
Wf
Width of feed line
Lgp
Length of ground plane
ht
Height of elemental triangle
wt
Width of elemental triangle
Ls
One face of primary slot
Value
20 mm
20 mm
7.2mm
6.8 mm
4.8 mm
1.9 mm
3.5 mm
10.3 mm
12 mm
1.7 mm
In the following work, certain changes in the
geometry of antenna have been incorporated to
analyze the effect on bandwidth coverage, VSWR and
gain enhancement.
A. Proposed Modified Design
1) Model 1:
In this design, the radius of outer ring is varied and
other parameters are kept same as given in Table 1.
The radius of outer circle is taken to be 7.8mm and
radius of inner circle is 6.8mm. The simulated
behavior of new antenna is examined and compared
with the reference STF antenna. Fig. 3 describes the
geometry of Model 1.
ISSN: 2231-5381
Fig. 4 Design of proposed modified STF antenna with
reduced area
3) Model 3:
In this design, double area is reduced as compared
to model 2, represented in Fig. 5. The area reduction is
carried out by the same process as in model 2.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
Fig. 6 S11 of Reference model and Model1
Fig.5 Design of proposed modified STF antenna with
double area reduction
IV. METHODOLOGY
The proposed fractal structure is designed and
simulated using FR4 substrate of dimensions 20 x 20
x 1 mm3 with tangent loss 0.02 and relative
permittivity 4.4. The type of ground considered is
semi-elliptical, with width 20 mm, length 3.5 mm,
having a notch of 2.4 x 1.16 mm2, at feed location, for
better impedance matching. The length and width of
feed line is selected to be 4.8 x 1.9mm2 to attain 50Ω
characteristic impedance.
The STF antenna is simulated with the help of
Finite Element Method based Ansoft numerical solver
High Frequency Structure Simulator (HFSS), which
divides the problem region into number of sub-parts
and each sub-part is described by a set of element
equations. For the final calculation, Systematic
recombination of all sets of element equations is
converted into a global system of equations.
The gain has also increased and is reasonable over
the entire range of frequencies represented in Fig. 7.
Fig. 7 Gain of Reference model and Model1
V. RESULTS AND DISCUSSION
A. Comparison between Reference Model & Model
1
The Model 1 is developed by raising the area of
outer ring radius of reference model. After the
simulation of Model 1, performance is analyzed and
compared with the reference antenna. It has been
found that the new antenna results in a much better
return loss and bandwidth than Reference model,
shown in Fig. 6.
Fig. 8 VSWR of Reference model and Model1
Fig.8 shows the VSWR parameter of reference
model and model 1 STF antenna. The value of VSWR
is varying between 1 and 2 over required operating
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
bands. It is clear that the VSWR parameter for model
1 is better as compared to reference antenna.
The comparison between Reference model and
Model 1 is shown below in Table 2.
VI. TABLE II
COMPARISON BETWEEN REFERENCE MODEL &
MODEL 1
Model
Reference
Model
Model 1
Frequency
Bands (GHz)
(4- 9.25)
(13- 14.9)
(18.7-20.7)
(22.8- 30)
(4.35- 10.13)
(12.35- 30)
Gain (dB)
(4.32- 3.06)
(5.03- 5.88)
(4.75-4.36)
(4.97- 4.90)
(5.27- 3.00)
(4.6- 6.43)
Fig. 10 Gain of Model 1, Model 2 and Model 3
B. Comparison between Model 1, Model 2 & Model
3
The area of model 2 and model 3 is reduced as
compared to model 1 but, as we can see in the Fig. 9
& Fig. 10, the results of models with area reduction
are somewhat better than model 1. In model 2,
triangles are cut from the outer ring. In model 3,
double area is reduced as compared to model 2 by the
implementation of same technique applied for model 2.
Fig. 9 shows the S11 parameter of model 1, model 2
& model 3. It can be seen that reducing the area of
patch does not degrade the bandwidth and return loss
of antenna, rather, it is improved.
Fig. 11 VSWR of Model 1, Model 2 and Model 3
VSWR of model 1, model 2 and model 3 is
described by Fig. 11. The value of VSWR is ranging
between 1 and 2 over the required frequency bands.
The Comparison of Model 1, Model 2 and Model 3
is tabulated below in the Table 3.
VII. TABLE III
COMPARISON BETWEEN MODEL 1, MODEL 2 &
MODEL 3
Model
Model 1
Fig. 9 S11 of Model 1, Model 2 and Model 3
Fig. 10 represents the gain of model 1, model 2 and
model 3. It can be observed that the gain of model 1,
model 2 and model 3 is good over the required
operating bands and is shown in Table 3.
Frequency Bands (GHz) Gain (dB)
(4.35- 10.13)
(5.27- 3.00)
(12.35- 30)
(4.6- 6.43)
Model 2 (4.28-10.07)
(4.92- 3.42)
(12.20- 30)
(4.52- 6.54)
Model 3 (4.28- 10.04)
(5.16- 2.9)
(12.25- 30)
(4.41- 6.53)
The proposed modified STF antenna is said to
occupy centimeter band, as the wavelength ranges
from (1-10) cm for super high frequency range.
VII. CONCLUSIONS
The proposed modified STF antenna is presented
and simulated over wide bandwidth (1-30) GHz using
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International Journal of Engineering Trends and Technology (IJETT) – Volume 27 Number 1- September 2015
adaptive mesh technique. It has been shown in the
work that by changing the geometrical parameters of
antenna, improvement in the performance can be
achieved. The proposed STF antenna is applicable
over Super High frequency range applications i.e. WiFi, Wireless USB, Satellite Communication and
WLAN etc., as antenna is applicable over frequency
ranges (4.3-10.05) GHz & (12.20-30) GHz. This work
can be carried out in future by using different feed
techniques, modifying the ground or patch structure
etc. to improve the performance parameters.
[17]
S. Kaur, Rajni, and G. Singh, “On the Bandwidth
Enhancement of Modified Star-Triangular Fractal Antenna,”
in Proc. ICRCWIP, 16th- 17th Jan. 2015.
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