MINIATURISATION OF PATCH ANTENNA USING NOVEL FRACTAL GEOMETRY

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International Journal of Electronics and Communication Engineering & Technology
(IJECET)
Volume 7, Issue 1, Jan-Feb 2016, pp. 63-74, Article ID: IJECET_07_01_007
Available online at
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ISSN Print: 0976-6464 and ISSN Online: 0976-6472
© IAEME Publication
MINIATURISATION OF PATCH ANTENNA
USING NOVEL FRACTAL GEOMETRY
Padmavathi C
Department of Electronics & Communication Engineering, ACED
Alliance University, Bangalore, Karnataka, India
ABSTRACT
In the Field of low profile antenna micro strip patch antennas have
attracted many researchers due to small size and low cost of fabrication. One
of trending member of new designs is Fractal antenna. Fractal shapes are
recursive/repetitive self-similar geometries, due to this self-similarity they can
provide high gain, multiband, wideband solutions and design miniature
antenna. Fractal shapes are widely used in computing, analysis and design;
recent trends suggest positive outcomes of using fractal shapes in
electromagnetics and communication system. In this paper Jerusalem cube
fractal shape is introduced in probe fed conventional patch antenna for L1
band. A dual band antenna resonating at 1.41 GHz (L) and 3.37 (S) GHz,
band is constructed using said fractal shape. The comparison of Return loss,
Gain, VSWR, % miniaturisation and radiation patterns are shown with
conventional patch antenna. Analysis is done on RT duroid 5880 with
dielectric constant εr = 2.2. The novel fractal antenna is designed, simulated
using an soft HFSS 13.0.
Key words: Fractal Antenna, Jerusalem Cube Fractal, Miniaturisation, Patch
Antenna
Cite this Article: Padmavathi C. Miniaturisation of Patch Antenna Using
Novel Fractal Geometry. International Journal of Electronics and
Communication Engineering & Technology, 7(1), 2016, pp. 63-74.
http://www.iaeme.com/IJECET/issues.asp?JType=IJECET&VType=7&IType=1
1. INTRODUCTION
Advancements in Wireless communication have paved the way for many researchers
to make the system smarter and smarter. In most of RF and Microwave applications
antenna plays an important role, As per the IEEE std.145-1983 the antenna is
considered as means for radiating or receiving radio waves. Theoretically they are the
transducers which convert RF signal into Electromagnetic waves and viceversa.
Antenna in early days used to be voluminous and high profile.

Padmavathi C
Technically, the need is for wider bandwidths, higher gain, smaller size and
multiband abilities in antennas. Cost too, is a factor of consideration. Hence low
profiles and less complexity in fabrication are areas of interest in antenna research.
Printed antennas have capabilities of answering all these demands. In addition, printed
antennas can be smaller in size and can be used for smallest applications to the largest
ones. These printed antennas are widely used in mobile and satellite communication,
the patch antenna allows modifications in their design which can make them suitable
for wideband and multiband applications and also help in miniaturisation. These
micro strip patch antenna are light weight, low cost, easy to design / manufacture, on
the other side these antenna are low profile, low power handling capabilities, low
efficiency and are not suitable for high bandwidth applications these limitations is
overcome by Fractal antenna.
The method to design patch antenna with better properties is to use fractal shapes
in design [9]-[12]. Fractal is an object achieved by recursive arrangement of a shape
or pattern keeping it same at every scale, they are space filling contours and offers
longer electrical length in smaller spaces this help in antenna miniaturisation, offering
multiple resonant frequencies. The term fractal means uneven or broken, the
geometries are complex and cannot be defined using Euclidean geometries and
mathematically infinite structure. The conventional methods available for antenna
miniaturisation does not maintain good characteristics after certain percentage of
miniaturisation and losses its performance. Fractals can help enhancing antenna
performance in terms of Gain, Return Loss, Side Lobes Reduction, etc. If we can
prepare an antenna with enhanced transmission / reception of GPS signals, it would
help in betterment of number of devices. The research in Fractal Antennas is still in its
emerging phase.
Very promising results are seen for further studies in enhancement of antenna
characteristics. Along with Gain and Return Loss enhancement, using fractals not
only creates other frequency bands but shifts the original frequency down. This can be
widely utilized in antenna miniaturization. Literature shows more use of Koch and
Sierpinski models of fractal shapes in monopole, dipole and patch antennas. Wide
scope of combining more than one GPS frequency or combine GPS with classical
GSM or ISM application is there using fractal shapes. Some of the fractals like Koch
curve and Sierpinski gaskets are, even at present, widely used to create multiband and
wideband antennas. Using Sierpinski Carpet fractal, up to 14 % of miniaturization in
conventional L1 band antenna (1.575 GHz) was achieved. Up to 19 % of
miniaturization is achieved using another fractal shape of Koch Curve / Koch
Snowflake.
In this paper an antenna which resonates at L5 (1.17 GHz) GPS frequency band is
designed. The primary model for implementing the fractal is designed using
conventional patch antenna designing parameters. The results show clear resonance at
L5 band with positive gain value and a reasonably good radiation pattern. The co-ax
probe feeding method is tested and results are extracted. In this paper a dual band
antenna which resonates at L and S band with Probe fed technique along with up to
20% miniaturization is achieved using Jerusalem Fractal with promising Return Loss
as well as Gain values. Radiation patterns and VSWR plots are also extracted for each
individual antenna.

Miniaturisation of Patch Antenna Using Novel Fractal Geometry
2. MICROSTRIP PATCH ANTENNA
Micro strip patch antenna is a printed metal patch on ground dielectric substrate, patch
radiates depending on its length, width, feed location, gain, radiation pattern,
dielectric constant of substrate. The patch antenna operating frequencies range from
900 MHz or lower to 30-40 GHz and have three layers top metallic layer is the patch
which radiates, bottom metallic layer is the ground, and middle layer is dielectric. The
resonating frequency of antenna depends on length of patch and dielectric constant of
substrate along with other parameter [16].
Figure 1 Micro strip patch antenna
The patch is made of conducting radiating materials such as gold, copper etc. The
Radiating metallic patch and the probe feed lines are usually photo etched on the
dielectric substrate. Micro strip patch antenna radiate mainly because of the fringing
fields effect between the patch edge and the ground plane. For a rectangular patch, the
length L of the patch is usually 0.3333λ0<L<0.5 λ0, where λ0 is the free space
wavelength. The patch is selected to be very thin such that t << λ0 (where t is the
thickness of patch). The height h of the dielectric substrate is usually 0.003 λ0 ≤ h ≤
0.05 λ0. The dielectric constant of the substrate (εr) is typically in the range 2.2 ≤ εr ≤
12.
2.1. Conventional Rectangular Patch – Co-ax Feed
Since the length of the patch and operating frequency has a direct relation, any of
them has to be defined in the beginning. We will try making an Antenna for L5 band
applications i.e. 1.17 GHz of operating frequency. The antenna Design Equations are
f0 = 1.17 GHz
0=c/ 0 = 256 mm
εr = 4.4 for Material FR4
h = 1.56 mm, height of substrate
For Width of Patch,
= = = 78.023 mm
For effective relative permitivity in the medium
εreff = +
Substituting the values we get, εreff = +
εreff = 2.7+1.52=4.22

Padmavathi C
For the actual wavelength in the medium, λ = = 124.61mm
Effective length can be found as Leff = = 62.40mm
Difference due to fringing field can be expressed as
ΔL = 0.412h = 0.641mm
The actual patch length
L = Leff - 2ΔL = 61.11mm
Ground plane dimensions are
LG = 6(h) + L = 70.47mm, WG = 6(h) + W = 87.38mm
2.2. Simulations of coventional rectangular patch antenna
(a) (b)
(c)
Figure 2 Antenna for L5 Frequency with Co-ax Feed (a) Top view (b) Side view (c) Angular
view

Figure 3 Return loss of the reference antenna for L5
From Fig.3 it is seen that the antenna resonates at 1.172 GHz which is the L5 band
used for aeronautical navigation along with L1 and L2. The return loss value at the
said frequency is less than -35 dB which shows good VSWR.
Figure 4 Gain plot of the reference antenna for L5
From Fig.4 the positive gain value of 1.89 dB is seen.
Figure 5 Radiation Pattern at L5 frequency

Padmavathi C
3. DESIGN OF ANTENNA
3.1. The Jerusalem Cube Fractal
The Fractal Jerusalem curve is not widely used in printed antenna design is mostly
used in 3D modelling. A novel dual band antenna is conceptualised, simulated and
compared using Jerusalem cube fractal shape on patch. The fractal shape is simple
and easy to design compared with other fractals, the fractal shape is made on a square
or a rectangular patch, the whole patch is made into 9 parts and + cross sign is cut out
of the centre square, this is repeated up to number of levels. In this fractal design, a
cross sign is used, the curve is applied at the edges of conventional patch antenna as
slots in shape of cross used in Jerusalem fractal.
Figure 6 Jerusalem Fractal up to three levels
3.2. Dual Band Novel Fractal antenna Design
The specifications of the antenna are given as F0 = 1.57 GHz (L1 Band), resonating
Frequency, εr = 2.2 for Material Rogers RT / Duroid 5880, h = 1.56 mm, height of
substrate, L = 59.1 mm (W=L, since square antenna), length of the edge of square
patch LG = 80 mm (WG = LG), length of the edge of square ground plane, Length of
each segment in Jerusalem Fractal L1 = 10 mm, Feed Location fx = 11 mm from
centre for impedance matching, The width of single side of cross is 3.33mm, the feed
location is 14.6mm to ensure maximum power transfer, and size of slot is cut from the
patch in square of 10mm*10mm
(a)

(b)
Figure 7 (a) Conventional Patch Antenna (b) Jerusalem Slots on Patch Antenna
(a) (b)
(b)

Padmavathi C
(c)
Figure 8 (a) Conventional Antenna (b) Antenna with Jerusalem Slots (c) Patch Antenna using
Jerusalem Fractal as slots
From Fig.9 it reveals the antenna resonates at L (1.412 GHz) band and S (3.377
GHz) band.
Figure 9 Return Loss plot of Jerusalem Fractal Antenna
Figure 10 Gain plot for Jerusalem Fractal Antenna

(a) For 1.412 GHz
(b) For 3.377 GHz
Figure 11 Radiation Patterns at individual resonant frequencies on Jerusalem Fractal Antenna
The radiation patterns show that both the frequencies show symmetric response
over the theta. Only for 3.377 GHz, the Phi = 90 plot is different in nature from others
and shows response similar to an isotropic antenna.
Figure 12 VSWR plot of the Jerusalem Fractal Antenna
The VSWR plot shown above is in synch with the Return Loss plot. Since the RL
value of the first resonant frequency was high, the VSWR plot shows 3.31. However,
for the second resonant frequency, it shows only 1.56 value of VSWR which can be
considered as good.

Padmavathi C
Figure 13 Comparison of Return Loss of Conventional (L1) band and Jerusalem Fractal
Antenna (L and S) band
The return loss plot shows clear shift in frequency from 1.57 GHz of conventional
antenna to 1.412 GHz of Jerusalem fractal. The 1.5 GHz shift in frequency can
provide a miniaturization of considerable level.
Figure 14 Gain comparisons of Conventional Antenna and Jerusalem Fractal
Fig.14 shows that gain value of both the bands is considerably good compared to
that of the conventional antenna.
Table 1 shows the summary of the Return Loss, Gain, and VSWR and
Miniaturization level of both the antennas.
Table 1 Results and Miniaturization of Jerusalem Fractal Antenna
Antenna Type Results
Return Loss
(dB)
Total gain
(dB)
VSWR
Miniaturisation
(%)
Conventional Antenna (1.57
GHz)
-20.00 7.35 1.5650
0
Jerusalem Fractal Band 1
(1.412 GHz)
5.41 6.42 1.4120
20%
(Dual Band Antenna)
Jerusalem Fractal Band 2
(3.377 GHz)
-13.15 4.31 3.3770

4. CONCLUSION
The novel antenna is designed and simulated using HFSS 13.0. Coaxial probe feeding
is used in designing of an antenna. In the paper the dual band antenna resonating at L
and S Band using Jerusalem fractal as slots in patch for miniaturisation is proposed.
The work shows the positive results of using this fractal shape on conventional patch
antenna. The results show that dual band antenna had better gain and improved
miniaturisation characteristics suitable for GPS and navigation applications. There lies
immense scope of trying further various fractal geometries into patch antenna.
Selective geometries cam be evaluated to achieve further better results compared to
present ones. Also, present antennas can be tuned for further optimization of results.
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Padmavathi C
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MINIATURISATION OF PATCH ANTENNA USING NOVEL FRACTAL GEOMETRY

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