design-and-analysis-of-slot-fractal-antenna-using-koch-curve

@IJMTER-2015, All rights Reserved 638
Design and analysis of Slot Fractal Antenna Using Koch Curve
Naman Bhargava1
, Komal Tanwar2
, Suraj Nagpal3
Dept. of ECE, GIMT college, kanipla, kurukshetra, India
Abstract—In this paper, Slot fractal antenna using koch curve is proposed . The fractal geometry is used
in antenna design for achieving the desired miniaturization and multiband properties. In this proposed
antenna iterations are performed by applying koch curve in each side of the slot geometry. The design of
antenna is slotted with 2 times. The material used for substrate is FR4 with relative permittivity of 4.4 and
thickness is about 1.6mm.microstrip line probe is used to feed the antenna. This antenna is designed and
simulated by using HFSS software. The results show that the proposed antenna offers good performance
in multiband frequencies (2GHz to10GHz) which is suitable for wireless applications.
Keywords—antenna, fractal, koch curve, microstrip line probe
I.INTRODUCTION
The fractals are useful in designing multiband antenna and for miniaturization of an antenna In modern
wireless communication systems by increasing the electrical length into a antennas are needed with
smaller size and wider compact physical volume. Sharp edges, corners bandwidth. This has initiated
antenna research and discontinuities help to make antenna to in various directions; one of them is using
radiate efficiently. By increasing number of fractal shaped antenna elements. The microstrip iterations in
antenna design the resonant patch antenna consists of a radiating patch on frequency is decreased while
electrical length is one side of a dielectric substrate and a ground increased. Many fractal geometries have
been plane on the other side of the substrate. The found to be useful in developing new and patch can take
any possible shape and is made innovative design for antennas. It includes Koch of conducting material
such as copper or gold. curve, Sierpinski gasket geometry, Sierpinski Fractals have self-similarity and
space-filling carpet geometry, Hilbert curve and Minkowski properties which provide design of antennas
loop. Koch curve is one of the self-similar and with smaller size. Fractal geometry has unique space-
filling fractals which is used to obtain geometrical features occurring in nature. It can wideband,
multiband and/or miniaturized be used to describe the branching of tree leaves antennas. It
has highly rough and uneven shape and plants, lightning, coastline, snowflake and which helps to work
as a very efficient radiator. many more examples in nature. Fractal antenna A relation exists between
antenna dimensions design has two things such as initiator and and wavelength. It states that antenna size
generator. Initiator is the basic shape of the should be greater than quarter of wavelength geometry and it
can be any shape either triangle, unless antenna will not be efficient. Since rectangle or any other
quadrilateral. Generator antenna size is increased because of gain, is the shape which is obtained by scaling
the radiation resistance, and bandwidth are reduced. initiator and will be repeated either inside or
Hexagonal geometry is designed with substrate outside on the initiator to obtain subsequent of having
relative permittivity of 2.3 and stages to reach final fractal geometry. So thickness is about 2 mm and
iterations have generator is obtained from the initiator itself. done to improve the gain of the antenna. In
The selfsimilarity and space-filling properties of this paper a new fractal antenna which is designed by
applying Koch curve in an U-Slot geometry is proposed. FR4 material is chosen for the dielectric substrate
which has relative permittivity of 4.4 and thickness is about 1.6 mm[1]. This antenna is designed and

International Journal of Modern Trends in Engineering and Research (IJMTER)
Volume 02, Issue 06, [June – 2015] ISSN (Online):2349–9745 ; ISSN (Print):2393-8161
simulated by HFSS software. It is observed that in the second iteration of the antenna design has good
return loss than the base shape fig1 and first iteration1th fig2 and 2nd
time fig3.
II ANTENNA DESIGN
In this paper a new fractal antenna which is designed by applying Koch curve in an octagonal geometry
is proposed. FR4 material is chosen for the dielectric substrate which has relative permittivity of 4.4 and
thickness is about 1.6 mm. This antenna is designed and simulated by HFSS software. It is observed that
in the second iteration of the antenna design has good return loss than the base shape and first iteration.
The base shape of the proposed fractal antenna is constructed by applying Koch curve to the each three
sides of the slot geometry. And then one more slot is subtracted from the radiating patch. By this way base
shape is designed. Koch curve is one of the self-similar and space-filling fractals which is used to obtain
wideband/multiband and /or miniaturized antennas. It has highly rough and uneven shape
TableI: Antenna dimensions
III.SIMULATION RESULTS
The proposed fractal antenna is designed and simulated using HFSS software. The return loss should be
below -10 dB (S11 < -10 dB) and VSWR should be below 2 (VSWR < 2). Fig. 5 shows the return loss of
the base shape of the first iteration antenna. The graph is plotted between the return loss in dB and
frequency in GHz. Fig. 7 shows the graph of the return loss vs frequency for the first iteration of1th time
the fractal antenna. Fig. 9shows the graph of the return loss vs frequency for the first iteration of nd
which helps to work as a very efficient radiator. 2 time the proposed fractal antenna.
Fig1 Base shape Fig2 First iteration Fig 3 First iteration
of first iteration of 1 time of 2 time
PARAMETERS VALUES(mm)
Substrate
length*width
45*40
Substrate height 1.6
Ground length 45
Ground width 40
Feed line 20*3
Patch length
*width
19.575*22.4

Fig4:Base shape of first iteration
Fig5: return loss vs frequency of first iteration 2nd
time
Fig6: first iteration of 1th time
Fig7: return loss vs frequency of first iteration of 1th

Fig8:first iteration of 2nd
time
Fig9: return loss vs frequency of first iteration of
The simulated results of the antenna (base shape, first iteration and second iteration) are given by
following tabulations respectively. The Table II, III and IV shows the simulated results of the base shape,
first iteration and second iteration of the octagonal fractal antenna respectively.
TABLE II Simulated Results of FIRST ITERATION 1st
time
Selected
points
Frequencies
(GHz)
Return
losses
( dB)
m1 4.243 -21.759
m2 5.404 -18.443
m3 6.496 -15.675
m4 8.498 -13.098

TABLE III Simulated results of FIRST ITERATION OF 1th TME
m3 6.486 -26.728
m4 6.366 -14.703
m5 8.508 -17.819
TABLE IVSimulated results of FIRST ITERATION OF 2nd
TIMES
Selected
points
Frequencies
(GHz)
Return
losses
( dB)
m1 2.181 -12.720
m2 4.323 -27.946
m3 4.614 -26.935
m4 5.575 -21.385
m5 6.426 -15.677
m6 7.767 -18.031
m7 8.728 -16.352
According to the results it is observed that the first iteration of two times of the slot fractal antenna has
good return loss than the base shape and first iteration of one time. In the first iteration of one time the
return loss is obtained 38.902 dB at 4.24 GHz frequency range. In the first iteration of two times , the
return loss is obtained multiband frequency from 2GHz to 9GHz range. It is used for broadcasting.
IV. CONCLUSION
A slot fractal antenna using Koch curve is presented in this paper. The proposed structure has a dimension
of 45mm x 40 mm. The dimensions of the substrate and ground plane are kept constant and iterations are
done in radiating patch only. The simulated results are obtained using HFSS software. The proposed
antenna exhibits good performance in multiband frequencies (2 GHz and 10 GHz) which is suitable for
wireless applications such as media streaming and STM-1 (Synchronous Transport Module level 1).
Selected
points
Frequencies
(GHz)
Return
losses
( dB)
m1 2.191 -13.666
m2 4.243 -38.902

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