ITU-T Kaleidoscope 2010
Beyond the Internet? - Innovations for
future networks and services
ON THE DESIGN OF ULTRA WIDE
BAND ANTENNA BASED ON FRACTAL
GEOMETRY
Pranoti S. Bansode
University of Pune.
Dr.Rajkumar
Defense Institute of Advanced Technology(DU),Pune.
Presented by
Pranoti S.Bansode
pranoti2009@yahoo.com
Pune, India, 13 – 15 December 2010
Ultra wideband(UWB)
Definition: Ultra-wideband is a radio
technology that can be used at very low
energy levels for short-range high-bandwidth
communications by using a large portion of
the radio spectrum.
UWB radio transmissions can legally
operate in the range from 3.1 GHz up to 10.6
GHz, at a limited transmit power of 41dBm/MHz.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Unique features
Ultra short pulses
High data rate
Low duty cycle operation
High energy efficiency
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Abstract
Ultra wide band circular
fractal antenna which is fed
with coplanar waveguide.
This fractal antenna has
been designed and
fabricated on FR4 substrate
εr=4.3 and thickness
h=1.53mm with initial
diameter of solid circular
disc of 15mm.
Substrate dimensions have
been 44mm*40mm.
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Coplanar waveguide(CPW)
Coplanar waveguide consist of a center
strip with two ground planes located
parallel to and in the plane of the strip.
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The 50 Ohm impedance is matched by
adjusting the gap between stripline and
ground plane
Advantages:
- It has lower dispersion characteristics at
higher frequencies.
- Broader impedance bandwidth.
- It have best ability to taper into a pin.
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The experimental result of circular fractal
antenna exhibits the ultra wide band
characteristics from 3.295GHz to 13.365GHz
correspondence to 120.88% impedance
bandwidth.
The resonant frequency of simple circular disc
monopole antenna is 4.31GHz which is shifted
to 3.71GHz in circular fractal antenna.
This indicates the size reduction of an
antenna.
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This antenna exhibits the properties,
-Miniature size.
-Low resonance.
-wide band phenomenon.
-Omni directional radiation pattern.
Advantages:
Light weight, Low profile, low cost & ease
of fabrication, easy to integrate with RF
devices and MIC/MMIC.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Fractal Antenna
A fractal is a rough or fragmented geometric
shape that can be split into parts, each of
which is (at least approximately) a reducedsize copy of the whole."
Features:1) It has a fine structure at arbitrarily small
scale.
2)It is self-similar.
3) It has a simple and recursive definition.
4)Fractal antennas are multi-resonant and
smaller in size.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Properties of fractal Antenna
1.Self similarity:
It helps to achieve multiband characteristics.
2.Infinite Perimeter:
Pune, India, 13 – 15 Dec 2010:
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3.Fractal in Telecommunication systems:
Here, Five different antennas for
five different Frequencies
In Fractal, Five different
frequencies in only One antenna..
Pune, India, 13 – 15 Dec 2010:
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Antenna Design
Descartes Circle Theorem:
If four mutually tangent circles have
curvatures Ki (i=1,2,..4)Descartes theorem
says,
To find the radius of the fourth circle tangent
to the three given touching circles then the
equation is written as,
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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The fractal antenna has been constructed
based on Descartes circle theorem the
dimension of each iteration can be calculated
with the help of following table.
Initiator 0th
1st
2nd
3rd
4th
Iteration Iteration Iteration Iteration Iteration
No. of
circles
generated
1
2
2
4
4
Radii
1
1/2
1/3
1/6
1/11
Pune, India, 13 – 15 Dec 2010:
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Iterationwise Geometry:
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Resonant frequency of the simple
microstrip antenna can be calculated
by,
Where Vo is the velocity of light.
The effective radius reff can be
calculated by the following expression,
Pune, India, 13 – 15 Dec 2010:
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0.5mm
The impedance
matching have been
achieved by adjusting
the width 3.2mm of
the inner conducting
and optimizing the
gap between the
0.7mm 40mm
ground plane and
feed width to
3.2mm
g=0.7mm i.e. 70Ω for
wide bandwidth.
44mm
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Result by Optimizing the gap between
patch and ground.
To achieve the ultra wide band
characteristic the gap between patch and
ground has been optimized to h=0.5mm.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Result by Optimizing the ground
length.
The length of ground plane GL=14.17mm
and width of the ground plane GW=19.7mm.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Result by taking Iterations in the
design.
As we increases the no. of iterations in a
design the first resonant frequency is shifts
to the lower side and higher frequencies gets
added in it.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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The first resonant frequency of conventional
simple circular disc monopole antenna is at
4.31 GHz.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Result of disc monopole antenna:
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The first resonant
frequency of circular disc
fractal antenna is at 3.75 GHz
So, it shows that as no. of
iterations increases frequency
shifts to the lower side and
higher frequencies gets add.
This indicates the size
reduction of an antenna.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Result of circular fractal antenna:
Pune, India, 13 – 15 Dec 2010:
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Current distribution
Current distribution of the proposed
antenna is mainly along the circumference
of the circular disc.
The current density is low in
the middle area of the solid
circular disc monopole antenna
Therefore, the current will
not be affected if the middle
area metallization of the solid
circular disc monopole antenna
is removed by circular or other
geometrical pattern.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Removing some portion of
metallization from solid
circular disc increases the
effective path of the surface
current.
In this antenna, the
effective length of current
path is increased by
inscribing circle patterns
inside solid circular disc using
Descartes circle theorem.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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Radiation pattern
It is the mathematical function or a
graphical representation of the radiation
properties of the antenna as a function of
space co-ordinates.
The radiation in azimuth as well as
elevation plane has been measured at
selective frequencies.
The H plane pattern is nearly Omni
directional and monopole like radiation
pattern in E plane and it is stable
throughout the band.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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H-Plane radiation pattern
The H plane
pattern is nearly
Omni directional.
The radiation
patterns in H-plane
have been measured
at frequencies 4.2
GHz 7.0 GHz,8.775
GHz and 10.1 GHz.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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E-Plane radiation pattern :
Monopole like radiation
pattern in E plane.
The radiation patterns
in E-plane have also
been measured at
frequencies 6.6 GHz,
8.325 GHz and 9.525
GHz as shown in
Figure.
Pune, India, 13 – 15 Dec 2010:
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Conclusion
It is observed as iterations increases, first
resonant frequency shifts to the lower
frequency side, thus yielding size reduction of
the antenna.
The measurement results exhibits the excellent
UWB characteristics in the wide range from
3.295 GHz to 13.365 GHz corresponds 120.88
% impedance bandwidth and good radiation
pattern.
The Ultra wide band characteristics achieved by
using CPW fed and Fractal concept.
Pune, India, 13 – 15 Dec 2010:
ITU-T Kaleidoscope 2010 – Beyond the Internet? Innovations for future networks and services
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UWB Applications:
Wireless communication systems:
-LAN & PAN
-Roadside info-station
-Short range radios
-Military communication
Radar and sensing:
-Vehicular radar
-Medical imaging
-Surveillance
Pune, India, 13 – 15 Dec 2010:
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References :
[1]L. Yang and G. B. Giamalkis, “Ultra wide band Communications,”
“IEEE signal processing magazine, Nov. pp. 26-28, 2004.
[2]
C. P. Baliarda, 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, (1998).
[3]
R.V. Haraprasad, Y. Purushottam, V.C. Misra, and N.Ashok,,”
Microstrip fractal patch antenna for multiband communication,”
Electron Lett. Vol. 36, pp. 1179-1180, 2000.
[4]
N. P. Agrawall, G. Kumar, K. P. Ray,” Wide-Band Planar
Monopole Antennas,” IEEE Transactions on Antennas and
Propagation, Vol. 46, no. 2, pp.294-5, February 1998.
[5]
M. Hammoud, P. Poey, F. Colombel,” Matching the Input
Impedance of a Broadband Disc Monopole,” Electronics Letters,
Vol. 29, no. 4, pp. 406-7, 18th February 1993.
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Thank you!!!
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