Proceedings of Asia-Pacific Microwave Conference 2007
Left Handed
Metamaterial
Design for
Antenna Application
Microstrip
T. C. Han, M. K. A. Rahim, T.Masri, M.N.A Karim
Faculty of Electrical Engineering, Universiti Teknologi Malaysia (UTM)
81300 UTM Skudai, Johor, Malaysia
cheehan.tan wgmail.com, mkamalIwtke.utm.my, ithelaha wyahoocom.my, nazril801 wyahoocom
Abstract-The speculation and invention of Left-Handed Meta
Material (LH MTM) had sparked the interest of many
researchers globally and was said to help increase the gain and
directivity of the microstrip antenna. This paper discusses the
design, simulation, fabrication and measurement of LH MTM in
order to proof the claims. As of the structure design, the
combination of the Square Rectangular Split Ring and the Thin
Wire Structure was used for fabrication purposes on an FR-4
Board using the Wet Etching Technique. From the simulation,
the gain of the antenna had increased to 1.2 dB while in the
measurement, 2 dB and 4 dB of increment were observed in the
maximum power received of the antenna for the E-Field and HField respectively. This had proven that the focusing effect of the
LH MTM really enhance the gain of the antenna. On the other
hand, the Return Loss (Sil) had improved by 9.62 dB and 12.29
dB in the simulation and measurement results respectively.
Therefore, we could also conclude that LH MTM also
contributed to the betterment of the matching of the antenna.
I. INTRODUCTION
In year 1967, Victor Vesalago, a Russian Physicist made a
theoretical speculation on the existence of substances with
simultaneously negative permittivity and permeability, which
serves as the origin of all research on LH MTMs. However,
there was not much progress until year 1999 when Prof J.B
Pendry proposed his design of Thin-Wire (TW) structure that
exhibits the negative value of permittivity, £ [1] and the Split
Ring Resonator (SRR) with a negative permeability, [t value.
Following this interesting discovery, Dr. Smith from Duke
University combined the 2 structures and became the first to
fabricate the LH MTM in his lab.
Subsequently, with the paths paved by the pioneers, more
and more researchers emerged to study this peculiar material
in many fields. Among them was a study on specific reduction
rate in a muscle cube with SRR [2]. The significance of this
study was to reduce the electromagnetic waves that reached
the human brain when communicating via mobile phones. In
the experiment, the muscle cube was a substitute of a human
brain and the SRR were designed to function at 900 MHz and
1800MHz (the well known cellular phone's frequency band).
By the end of the experiment, it was evident that the S21 was
reduced in the specific frequencies. On the other hand, many
researches were done to improve the response of microstrip
antennas in particular since this type of antenna is desired for
its low cost properties but with the compromise in the gain
and directivity. According to some studies done [3]-[4], the
LH MTM could actually increase the directivity of the
microstrip antennas by locating a LH MTM cover in front of
the propagating face of the antenna. Furthermore, there was
also a study for filter applications by utilizing the microstrip
technology as well [5]. Through this particular experiment, it
proved that SRR is also a frequency selective device and
could be treated as a filter.
As a result, a few paramount objectives of this study were
set that were:
*
*
To investigate the microstrip antenna properties
(Return Loss, Gain, Directivity, Half Power Beam
Width, Cross Polar Isolation, etc.) of the antenna during
the presence of LH MTM.
To verify some all the claims such as the Double
Negative Parameters (DNG Parameters), Negative
Refractive Index (NRI) and Backward Wave
Propagation stated in the books and papers through
simulation and measurement processes.
II. METAMATERIAL DESIGN AND SIMULATION
A research on LH MTM was carried out to understand the
fundamentals of the newly discovered substance. Then, the
CST Microwave Studio was chosen as the ultimate software
to simulate the structure showed in Figure 1 as this software is
desirable for a 3D platform in simulating a full wave
simulation. This structure was obtained from [5] and the
boundary conditions were set similar to a waveguide setup
explained in [6].
After obtaining the S-parameters from the software, they
were exported to MathCAD to calculate the effective values
of permittivity and permeability by utilizing the NicolsonRoss-Weir (NRW) Approach [7] and the results obtained are
shown in Figure 2 and 3. The equations used in this paper
were:
2jkd(72 1)
2jkd(2 -1)
SiI
(7+ 1)2 -(1_1)2
4t7
El =::: PIr +J 2S1ld
1-4244-0749-4/07/$20.00 w2007 IEEE.
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(1)
(2)
Eventually, a microstrip antenna was design to operate at
the Left Handed frequency range where both values of
permittivity and permeability were negative. In this paper, the
frequency of 3.9GHz was chosen for the microstrip antenna's
operating frequency and the antenna's specifications are
shown in Table 1. Subsequently, after the antenna was
simulated and the desired result as in Figure 4 was obtained,
the integration of the LH MTM and the microstrip antenna
was simulated using the CST Microwave Studio. Figure 5
illustrates the set up of the antenna with the LH MTM. Then,
the distance between the LH MTM and the antenna was
altered to obtain the optimum distance in achieving the perfect
matching for the antenna - where the SII was swept from a
distance of 0 mm to 35 mm as shown in Figure 6 - and that
was translated into the increased gain of the antenna. From the
simulated results, the distance of 30 mm proved to present the
best matching results.
TABLE I
MICROSTRIP ANTENNA SPECIFICATIONS
Operating Frequency
Length (L)
Width (W)
Feed
Feed Location
Magnitude
3.9
15.7116
15.7116
Coaxial
X=7.8, Y=5.2
Unit
GHz
mm
mm
-
mm
CST
71sa|
os~
CST
__
Fig. 4 Simulation result ofthe Return Loss (SI,) ofthe microstrip antenna
CST
Computer,%mulation
'
eibn
I
Fig. 1 3D perspective view of the proposed structure re,,alizable on FR-4
Board
Effective DNG Parameters
800
800
600
-600
400
-
-400
200
200
I
Fig. 5 3D view of the integration of LH MTM and microstrip antenna
ReG(p)
=.=...
0
S-Parameter lagnitude in dB
1-200
-200
-40012
3
4
J-400
5
66
-e- - --
f
-- - --
--
--
--
-----------
.. r
-5
Frequency (GIz)
Fig. 2 Graph of the negative parameters obtained from MathCAD
-10
-
-15
.-
Eff-ti,e DNG P.-etm
.
IF
-22.82
3.6416
3.7
8
(
4
Frequency J GHz
Re
(r)
R
(Gr)
Fig. 6 Simulated SI, with variation in the distance between LH MTM and
antenna
I
Fig. 3 Zoomed in graph of the negative parameters
Finally, the radiation patterns of the microstrip antenna
with and without the integration of the LH MTM were also
simulated and shown in Figure 7 and 8. In order to illustrate
the difference between the response of the microstrip in the
presence of the LH MTM or instead, Table II has been
constructed. In that particular table, it was obvious that the SII,
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Gain and Directivity had soared and produced encouraging
results for further fabrication processes.
Farfield 'fartild f 3.9317) [1I' DirectivitAbsiThetal
CST
aCS
,D
~~~~~~~~~c-P,,W,mdllktion
gq
tmo
T30
l
30
Phi= 90
shown in Figure 11 and 12. From those figures, it was obvious
that the maximum power received by the antenna had
increased dramatically about 2dB for the E-Field and 4dB for
the H-Field. However, the magnitude of side lobes were
increased due to the imperfect matching that the setup of the
structure.
Phi 270
Return Loss (Si 1) dB
0
-2 -
-8 -
-10
-12
-14
-16
-18
-20
180
Frequency
Fig. 7 Radiation pattern of the microstrip antenna without the LH MTM
Fig. 9 Measured SI, of the microstrip antenna without the LH MTM
Farfield 'farfield
3
[f 3.8111 Directivity Abs(Thetal
Return Loss (S1 1) dB
0
30
0
-5
Z10
-15
-20
-25
-30
F35
3.8
Main lobe magnitude
Frequency
Side lobe level
dB)
=
X
dBi'
120
OJ.a deg.
Main lobe direction
Angular width 13
8.6
52.4 deg.
Frequency
0
-9.2 dB
180
Fig. 8 Radiation Pattern of the microstrip antenna with the LH MTM
Fig. 10 Measured SI, of the microstrip antenna with the LH MTM at the
distance of 25mm
TABLE II
SIMULATION RESULTS COMPARISON
Parameters
I
2
3
Return Loss (SI _l)
4
HPBW
Gain
Directivity
Without LH
MTM
(3.9GHz)
-13 dB
4.509 dB
6.9 dBi
87.90
With LH MTM
(3.83GHz)
-22.8 dB
5.728 dB
8.6 dBi
52.40
(a)
aPM
III.
FABRICATION RESULTS AND DISCUSSIONS
The fabrication process was done on an FR-4 Board. The
measurement of the SI, of the Patch Antenna with the
presence of LH MTM was done with the assistance of the
network analyser. The results obtained are shown in Figure 9
and Figure 10 and they showed an increment of 12dB in the
Sil.
In addition, the radiation patterns of the microstrip antenna
with and without the LH MTM were also measured and
Fig.
(b)
Measured E-Field Polar Plot for the (a) Antenna only and (b) Antenna
with LH MTM
11
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IV. CONCLUSIONS
The design, simulation and fabrication processes of the LH
MTM were presented and all the objectives within the scope
of the project were met. All fabrication work was done
manually in the Wireless Communication Centre, UTM.
From the whole project, it was proven that LH MTM was
indeed a peculiar substance with the double negative
parameters that could enhance the performance of a microstrip
antenna. This was because whenever the polarity of the
permittivity and permeability were reversed, a lot of other
theories follow suit and as a result, new modified theories
were being created. As in this paper, the two most obvious
results of the negative parameters that were presented were
the negative refractive index and the backward wave
propagation.
In addition, the presence of LH MTM could improve the
gain and directivity of a microstrip antenna as well as
reducing the Return Loss of the antenna. This was proven true
by means of the simulation and measurement results. Besides,
the modified NRW Approach was proven to yield reliable
results from the outcome of the whole project.
(a)
(b)
Fig. 12 Measured H-Field Polar Plot for the (a) Antenna only and (b) Antenna
with LH MTM
For the ease to compare the measurement results acquired
from the experiments, Table III was prepared and showed
very interesting results especially in the improved Return Loss
and the maximum power received in both the electric and
magnetic field. Besides, the reduced value of the Half Power
Bandwidth (HPBW) hinted the increase in Directivity.
[1]
[2]
[3]
[4]
[5]
TABLE III
MEASUREMENT RESULTS COMPARISON
[6]
2
Parameters at
4.24 GHz
Return Loss (S1I)
Max Power Received
Without
LH MTM
-18.6 dB
-33 dBm
With LH
MTM
-30.9 dB
-31 dBm
3
Max Power Received
-34 dBm
-30 dBm
20 dB
17 dB
26 dB
30 dB
800
850
500
500
1
4
5
6
7
8
9
(E-Field)
(H-Field)
Cross Polar Isolation
(E-Field)
Cross Polar Isolation
(H-Field)
HPBW (E-Field)
HPBW (H-Field)
Back Lobe Magnitude
(E-Field)
Back Lobe Magnitude
(H-Field)
-48 dBm
-44 dBm
-45 dBm
-42 dBm
[7]
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with Split Ring Resonators, IEEE, 2005
Hu Jun, Yan Chun-sheng, Lin Qing-chun, New Patch Antenna with
MTM Cover, J Zhejiang University SCIENCE A 7(1), 89-94, 2006
Shah Nawaz Burokur, Mohamed Latrach and Sergre Toutain,
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1.
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Qun Wu, Fan Yi-Meng, Ming-Feng Wu, Jian Wu, Le-Wei Li, Design
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