1. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
INTERNATIONAL JOURNAL OF ELECTRONICS AND
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Volume 4, Issue 2, March – April, 2013, pp. 15-22
IJECET
© IAEME: www.iaeme.com/ijecet.asp
Journal Impact Factor (2013): 5.8896 (Calculated by GISI) ©IAEME
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SELF-AFFINE RECTANGULAR FRACTAL ANTENNA WITH UC-
EBG STRUCTURE
Jagadeesha.S1, Vani R.M2, P.V Hunugund3
1
Department of Electronics & Communication, S.D.M Institute of Technology, Ujire-
574240, India
2
University of science & Instrumentation centre, Gulbarga University, Gulbarga- 5851006,
India
3
Dept. of PG Studies and Research in Applied electronics,Gulbarga University, Gulbarga-
5851006,India
ABSTRACT
In this paper, a probe-fed self-affine fractal antenna, which has a novel
configuration, is proposed and investigated for low profile and multi-band performance in
wireless communication systems. Fractal antenna is characterized by space filling and
self-similarity properties which results in considerable size reduction and multiband
operation compared to conventional microstrip antenna. The proposed self-affine
rectangular fractal antenna shows multiband behavior due to self-affinity in their
geometrical structure. Fractal is implemented on rectangular patch of dimension 40mm x
30mm embedded on ground plane of dimension 60mm x 60mm.The antenna is designed
on a substrate of dielectric constant €r=4.4 and thickness 1.6mm. The base antenna is
designed and simulated for 2.3 GHz. Further the base antenna is modified to first iteration
fractal antenna and then to second iteration fractal antenna. Along with fractal design the
EBG structures are also added to the proposed antennas. The antenna with first iteration
and EBG is resonating at 1.9 GHz giving a bandwidth of 91 MHz. The antenna with
second iteration and EBG shows multiple frequency resonances at 1.27GHz 1.6 GHz, 2.7
GHz, 3.44GHz, and 3.8GHz The antenna with second iteration indicates size reduction of
52.67% and gives over all bandwidth of 259 MHz. The proposed antenna is simulated
using IE3D and simulated results are in good agreement with measured results.
Keywords: self-affined antenna, Fractal antenna, multi-frequency, size reduction, wireless
application.
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
I INTRODUCTION
The emergence of antennas with fractal geometries has been a very valuable tool
for solving two of the major limitations of classical antennas: the single band performance
and the dependence of the operating wavelength on size. The self-similar properties of
certain fractals result in antenna with fractal properties having multiband behavior. On the
other hand, the highly convoluted shape of these fractals makes possible the reduction in
size of certain antennas [1].
The most recent multiband antenna development is based upon the exploitation of
the self-similarity property of fractal shapes and a number of new antenna designs have
been reported in the literature. Fractals are a class of geometrical shapes which have no
characteristic size (irregular patterns). These are composed of multiple iterations of a
single elementary shape and are used to describe a family of complex shapes that possess
an inherent self-similarity and self-affinity in their geometrical structure. A self-similar set
is one that consists of scaled down copies of itself, i.e., a contraction which reduces an
image by same factors horizontally and vertically. A Self-affine set, on the other hand, is a
contraction which reduces an image by different factors, horizontally and vertically. Thus,
it can provide additional flexibility in the antenna design, since by selecting the scale
factors appropriately; resonances can be spaced by different factors [2]. The space-filling
property of fractals tends to fill the area occupied by the antenna as the order of iteration is
increased. Higher order fractal antennas exploit the space-filling property and enable
miniaturization of antennas [3]. The total volume of multi-resonant structure can be
considerably reduced by optimizing the shape of fractal geometries in designing multi-
band antennas. Many studies on the complex fractal structure have been carried out
rapidly after the concept of fractal geometry, which provides isotropic self-similarities in
large or small scales focused on antenna design and appears to be self-affine properties in
signal processing and material surfaces has been introduced by Mandelbrot [4].
Method of improving the antenna performance is by using the electromagnetic
band gap (EBG) structure on microstrip antenna. EBG structures are periodic lattices,
which can provide effective and flexible control over the propagation of the EM waves
within a particular band. It has been shown that this structure can lower input return loss
and widen the impedance bandwidth by suppressing the unwanted surface waves [5].This
feature applied in field of antennas helps improve performance of antenna, such as
increasing the gain of antenna[6].
In this paper we propose self-affine rectangular fractal antenna with first and
second iterations. Along with fractal the uniplanar compact electromagnetic band gap
(UC-EBG) periodic structures are surrounding the antennas. The study has been made to
know the bandwidth, gain and size reduction of proposed antennas.
II DESIGN OF SELF-AFFINE RECTANGULAR PATCH ANTENNA WITHOUT EBG
Self-affine fractal antenna is considered in this paper which reduces an image by
different factors; horizontally and vertically thus it can provide additional flexibility in
antenna design. The iteration factor which represents the construction of fractal geometry
generation is chosen to be one fourth and iteration number is two. The antenna is designed
on a dielectric substrate of relative dielectric constant r=4.4 and thickness 1.6mm. The
shape of zeroth iteration is shown in fig 1(a), is a conventional rectangle antenna of
dimension 40mm x 30mm is mounted on substrate having a ground plane of dimension
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
60mmx60mm. The multiband antenna with fractal geometry is created by the initial
model. The suitable feed location is obtained at (-4mm, -8mm) from the origin through
optimization technique. The input impedance of the antenna was calculated using IE3D
software package. Fractal geometry of reference and its first and second iterations with
scaling factor of four are as shown in figure 1(a) to 1(c). The photographs of base, First
and Second iteration antennas are as shown in fig 2(a) to 2(d). Fractal antennas are
optimized resulting in the following parameters h=1.6mm, L=40mm, W=30mm,
g=60mm,Wg=60mm,L1=7.55mm,W1=10mm,L2=10mm,W2=7.55mm,L3=2.5mm,W3=4.
06mm, L4=4.06mm,W4=2.5mm.Dp=(-4mm,-8mm)
The return loss characteristics and radiation patterns of the fractal antenna are as shown in
fig: 2 and fig: 3 respectively.
Fig 1(a) Fig 1(b) Fig 1(c)
Geometry of reference First iteration fractal Second iteration fractal
antenna antenna antenna
Fig 2(a) Fig 2(b) Fig 2(c) Fig 2(d)
Fabricated reference Fabricated antenna Fabricate antenna Fabricated antenna
Antenna with top with bottom view with first iteration with second iteration
The characteristics of all proposed antennas were simulated by using IE3D
software and verified experimentally by using vector network Analyzer model Rhode and
schewarz, German make ZVK model No.8651. For all cases, the simulated results
obtained and are compared to the experimental results and are shown in fig 3(a) to 3(c).
The measured parameters are shown in purple coloured lines while simulated ones are
shown in dark block coloured lines. From the figure it is observed that there is a good
agreement of simulated results with measured results. Self-affined rectangular fractal
antenna with zero iteration is resonating at 2.32 GHz and 3.55GHz. The antenna with first
iteration gives resonance at 1.9 GHz. Similarly the antenna with second iteration is
resonating at 1.27 GHz, 1.62 GHz, 2.72 GHz, 3.46GHz and 3.82GHz i.e it gives multiple
frequencies. The results of proposed fractal antenna with different iterations are shown in
Table 1.The overall bandwidth is 245 MHz with second iteration. The radiation patterns of
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
all iterations were studied through simulation and it is shown in fig 4(a) to 4(d). All the
radiation patterns are broadside patterns. Practical radiation patterns are as shown in fig
5(a) & 5(b). Simulated radiation pattern well agreement with measured results.
Fig 3(a) Fig 3(b) Fig 3(c)
Return loss characteristic Return loss characteristic Return loss characteristic of
of reference Antenna of antenna with first iteration antenna with second iteration
Fig 4(a) Fig 4(b) Fig 4(c) Fig 4(d)
Radiation pattern Radiation pattern Radiation pattern Radiation pattern
@ 2.3 GHz for @ 1.91GHz for @ 1.27GHz for @ 1.6GHz for
conventional first iteration second iteration Second iteration
antenna antenna without EBG without EBG
Table: 1 Results of proposed antennas without EBG Structure
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Fig: 5(a) Fig: 5(b)
Practical Radiation pattern H-plane Practical Radiation pattern H-plane
copolar at1.91GHz for first iteration Copolar 1.6 GHz for second iteration
for First iteration
III. DESIGN OF SELF -AFFINE RECTANGULAR FRACTAL ANTENNA WITH EBG
STRUCTURE
Fig 6(a) to 6(c) shows the geometries of rectangular fractal antenna with EBG structure.
Geometry of designed Self-affine rectangular fractal antenna with zero, first and second iterations
are surrounded by UC-EBG of Six numbers with size 9mmX9mm.The total area occupied by the
base shape patch is 40mmx30mm. The gap between EBG Structures them is 1mm. Optimized
dimensions obtained are h=1.6mm, La=40mm,Wa=30mm,Lg=60mm,Wg=60mm, L1=7.5mm,
W1=10mm, L2=10mm, L3=2.5mm, W3=4.06mm, L4=4.06mm, W4=2.5mm, Dp= (-4mm, -8mm).
The photograph of all designed antenna with self-affine rectangular fractal withUC- EBG are
shown in fig 7(a) to 7(c)
Fig: 6(a) Fig: 6(b) Fig: 6(c)
Geometry of reference First iteration fractal Second iteration fractal
antenna with UC-EBG antenna with UC-EBG antenna with UC-EBG
cells cells cells
Fig: 7(a) Fig: 7(b) Fig: 7(c)
Photograph of fabricated Photograph of Fabricated Fabricated antenna with
antenna top view with antenna bottom view second iteration UC_EBG
first iteration with first iteration structure
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Simulated and measured return loss characteristics of antenna are shown in 8(a) to
8(d). The agreements between measured and simulated results are good. The results are
summarized in Table 2.The results indicate that the proposed antenna performance with
periodic UC- EBG structures is improved in terms of band width and size reduction. The
reference antenna with zero iteration is resonating at 2.32GHz and 3.51GHz. The antenna
with first iteration gives resonance at 1.9GHz, while the second iteration is resonating at
1.27GHz, 1.6 GHz, 2.7GHz, 3.44GHz, and 3.8GHz respectively. The overall bandwidth is
enhanced to 259 GHz with second iteration.
Fig: 8(a) Fig: 8(b)
Return loss characteristics of Return loss characteristic of antenna
reference antenna UC-EBG with first iteration with UC-EBG
Fig: 8(c)
Return loss characteristic of second iteration with UC-EBG
Table: 2 Results of proposed antennas with UC-EBG structure
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7. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Radiation patterns have been studied for the fractal antennas with UC-EBG
structure and it is shown in fig 9(a) & 9(b) all are gives broad side pattern. Measured
radiation pattern also shown in fig 10(a) & 10(b) which also gives broadside. The
bandwidth of the antenna with first iteration with UC-EBG is 91MHz with corresponding
size reduction of 33.34%. Further there is an increment in overall band width of about
259MHz and corresponding size reduction of 52.67% after second iteration. In summery
there is increment in overall bandwidth of self-affine fractal antenna with periodic UC-
EBG structure in comparisons with self-affine antenna without UC-EBG structure.
Fig: 9(a) simulated radiation patterns Fig: 9(b) Simulated radiation pattern of
of proposed with first iteration periodic proposed antenna with second iteration
UC-EBG structure @1.9GHz periodic EC-EBG structure @ 1.6GHz
Fig: 10(a) Practical radiation pattern of Fig: 10(b) Measured radiation of proposed
proposed antenna with first iteration with antenna with second iteration UC-EBG
Periodic UC-EBG structure @ 1.9GHz structure @ 1.6GHz
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8. International Journal of Electronics and Communication Engineering & Technology (IJECET), ISSN
0976 – 6464(Print), ISSN 0976 – 6472(Online) Volume 4, Issue 2, March – April (2013), © IAEME
Table: 3 Results shown to compare proposed antennas without and with UC-EBG
structure
IV. CONCLUSION
This paper outlines a new concept of self- affined rectangular fractal antenna with iteration
factor of ¼ and order two are applied to fractal geometry with and without UC-EBG structure.
Measured value of resonant frequencies and bandwidth of these antennas have been found to agree
well with the simulated ones. The Antenna gives multifrequency operations and reduced size. The
size reduction obtained is 52.67% with bandwidth of about 259MHz after second iteration.
Measured radiation characteristics of proposed antenna with and without UC-EBG are well
agreement with simulated radiation characteristics and they are broadside patterns.
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