Electromagnetic Effect of Rectangular Spiral Metamaterial ...
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Journal of Modeling and Simulation of Antennas and Propagation, Vol. 2 (1), 13-21, 2016
ISSN: 2377-1674, Published online: www.unitedscholars.net/archive
Electromagnetic Effect of Rectangular Spiral
Metamaterial on Microstrip Patch Antenna
Performance
Chnar Hussein Aziz1
and Asaad M. J. Al-Hindawi2
1, 2 Communication Engineering Department, Sulaimani Polytechnic University, Sulaymaniyah, Iraq
[email protected] , [email protected]
ABSTRACT
This paper studies the electromagnetic effect, during
the process of covering metamaterials, on the
performance of a microstrip rectangular patch antenna
fed by a microstrip line for three ranges of operating
frequencies. The metamaterial cell is selected to be
double layers of rectangular spiral shape spaced by 1.5
mm FR4 epoxy substrate. The studied patches are
chosen to be three different sizes and designed to operate
at a resonance frequency of 2.4, 8.5 and 17 GHz
separately. Afterwards, each antenna is covered by
studied metamaterial cells of different numbers
according to the antenna area. The studied patch antenna
covered with metamaterial is simulated using a HFSS
simulator. The obtained results indicate that the effect of
the metamaterial cell leads to an increase in the number
of resonance frequencies for each patch antenna while
the band width of antenna patch of 8.5GHz increases to
44.64%.
Keywords: Microstrip patch antenna, Metamaterial,
Refractive index, Permittivity, Permeability.
1. INTRODUCTION
Today’s need for more multifunctional systems
yields to the necessity for small mobile terminals,
including cell phones, handheld portable wireless
equipment for internet connection, short- and long-
range communication devices, RFIDs (radio
frequency identification), etc. Similarly, small
equipment and devices used for data transmission
and navigation (GPS systems) require small
antennas. These applications and continuing growth
of wireless devices will continue to challenge the
community to create smaller and more
multifunctional antennas [1]. The development of a
4G to 5G wireless communication industry has
grown by orders of magnitude, fuelled by digital
and RF circuit fabrication improvements, new large
scale circuit integration, and other miniaturization
technologies which make portable radio equipment
smaller, cheaper, and more reliable [2].
New artificial materials, such as metamaterial, are
introduced to design microstrip antennas for
enhancing the performance and reducing the profile
[3]. Metamaterials (MTMs) are artificial media
characterized by constitutive parameters generally
not found in nature whose values can be engineered
to specified values. The first structure that has been
used to prove the existence of metamaterial was a
Split Ring Resonator SRR structure invented in
2001 by Shelby Smith and Schultz at the University
of California. SRR is a metallic ring with a split
introduced in its structure and works like an LC
resonant structure. These SRRs can be arranged in
an array to form a material that exhibits negative values
of both mu and epsilon and thus negative values of
the refractive index, n. This structure shows a
magnetic resonance at a particular frequency. The
position of this resonance frequency can be
changed by changing different geometrical
parameters of SRR [4].
Li B., Wu B., and Liang C.-H. (2006)
presented a new method to improve the gain of a
circular waveguide array antenna with metamaterial
structure. The electromagnetic characteristics of
metamaterial and circular waveguide antenna with
metamaterial structure are studied by using a
Aziz et al, Journal of Modeling and Simulation of Antennas and Propagation, ISSN: 2377-1674, Vol. 2 (1), 13-21, 2016
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numerical simulation method. Furthermore, they
are compared with those of a conventional circular
waveguide antenna. The simulation and
experimental results show that this method is
effective and that metamaterial structures can
congregate the radiation energy. Therefore, the gain
of the antenna increases while the side lobe level
decreases [5].
C. Sabah and S. Uckun (2009) presented the
frequency behaviour, in detail, of the multilayer
structure comprised of double-negative (DNG) and
dielectric slabs. The multilayer structure consists of
N pieces DNG and dielectric slabs with different
material properties and thicknesses. The incident
electric field is assumed to be a monochromatic
plane wave with any arbitrary polarization. The
DNG layers are realized using the parameters of
Lorentz/Drude type metamaterials. The transfer
matrix method is used in the analysis to find the
characteristics of the reflected and transmitted
powers. Finally, the computations of the powers for
two structures are demonstrated in numerical
results, for the application to design efficient filters
at the microwave, millimetre wave, and optical
frequency regions [6].
AsitK.Panda and Ashutosh Mohanty(2011)
proposed a new conjugate omega shaped structure
for the realization of the left hand material. This
new metamaterial (MTM) is designed and
simulated using CST MWS. The effective
permittivity & permeability are extracted from the
transmission & reflection data obtained by the
normal incident on the purposed structure. It is
shown that the purposed MTM exhibits DNG
material property and a negative refractive index in
a dual transmission band with a wider band in
frequency ranges of 3.35-6.37GHz and 12.53-
16.7GHZ. The conjugate omegas structures are
pseudo-chiral in nature, where both electric
magnetic polarization are due to induced electric
and magnetic fields [7].
P.K. Singhal and BimalGarg (2012) proposed
an “Interconnected Circular SRR’s” shaped
metamaterial structure at a height of 3.2mm from
the ground plane. The proposed metamaterial
structure enhances bandwidth by 173%, reduces
average area by 40%, increases directivity by
1.068dBi and reduces return loss by 16.513dB. The
proposed metamaterial structure along with the
patch antenna exhibits a 33.293dB return loss at
2.37GHz operating frequency and has an
impedance bandwidth from 2.3887 to 2.3118GHz.
The design and optimization of the Rectangular
micro strip patch antenna (RMPA) with and
without proposed metamaterial structure were
carried using CST Microwave Studio. Double-
Negative (permittivity and permeability) properties
of the proposed metamaterial structure have also
been verified in this work by using the Nicolson-
Ross-Weir (NRW) approach [8]
Mimi A. W. Nordin , Mohammad T. Islam ,
and Norbahiah Misran(2013) proposed a new
compact ultra wide band (UWB) patch antenna
based on the resonance mechanism of a composite
right/left-handed (CRLH) transmission line (TL).
The radiating element of the antenna is made from
three left-handed (LH) metamaterial (MTM) unit
cells placed along one axis. Each unit cell combines
a modified split-ring resonator (SRR) structure with
capacitively loaded strips (CLS) [9].
Wei Liu and etal (2014) presented a
metamaterial-based broadband low-profile
mushroom antenna [10]. The proposed antenna is
formed using an array of mushroom cells and a
ground plane and feed by a microstrip line through
a slot cut onto the ground plane. The proposed
dielectric-filled ( =3.38) mushroom antenna with
a low profile of 0.06λ0 (λ0 is the operating
wavelength in free space) and a ground plane of
1.10λ0×1.10λ0, attains 25% measured bandwidth
with (|S11<-10dB|) 9.9dBi average gain at 5-GHz
band.
The present paper introduces a study of the
electromagnetic response of metamterial cells on
the performance of a microstrip rectangular patch
antenna (band width and radiation pattern). Three
frequency bands of operating frequencies 2.4, 8.5
Aziz et al, Journal of Modeling and Simulation of Antennas and Propagation, ISSN: 2377-1674, Vol. 2 (1), 13-21, 2016
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and 17GHz have been chosen to test the designed
antennas.
2. ANTENNA DESIGN
Microstrip Patch Antenna Structure
The configuration of the studied patch antenna
illustrated in Figure 1, is feed by a microstripline
and is of rectangular shape. Three microstrip patch
antennas are designed separately to operate at 2.4,
8.5 and 17GHz and their dimensions are shown in
Tables 1, 2 and 3 respectively. The substrate
material is chosen to be Rogers RT/duroid 5880
with epsilon=2.2. The frequency responses of the
designed patch antennas to the return losses are
plotted in figures 2, 3 and 4 respectively.
Fig.1: Rectangular edge –feed patch antenna structure.
Table (3): Calculated dimensions of edge–feed rectangular
patch antenna at 17GHz.
Fig. 2: S11 parameter for the designed patch antenna at 2.4GHz.
Element Value (mm)
Patch dimension along x 15
Patch dimension along y 10.5
Substrate thickness 1.5748
Substrate dimension along x 25
Substrate dimension along y 32.5
Ground dimension along x 25
Ground dimension along y 32.5
Edge feed width 1
Edge feed length 7
Feed width 6
Feed length 11
Fig.1: Structure of edge–feed rectangular patch antenna.
Table 1: Calculated dimensions of edge–feed
rectangular patch antenna at 2.4 GHz.
Element Value ( mm)
Patch dimension along x 49.41
Patch dimension along y 41.36
Substrate thickness 1.5748
Substrate dimension along x 83.6
Substrate dimension along y 134.365
Ground dimension along x 83.6
Ground dimension along y 134.365
Edge feed width 1.885
Edge feed length 23.418
Feed width 4.852
Feed length 38.075
Table 2: Calculated dimensions of edge–feed
rectangular patch antenna at 8.5GHz.
Element Value (mm)
Patch dimension along x 6.9756
Patch dimension along y 4.8243
Substrate thickness 1.5748
Substrate dimension along x 16.4244
Substrate dimension along y 14.2731
Ground dimension along x 16.4244
Ground dimension along y 14.2731
Edge feed width 1.2731
Edge feed length 3.336
Feed width 4.3460
Feed length 1.3908
Aziz et al, Journal of Modeling and Simulation of Antennas and Propagation, ISSN: 2377-1674, Vol. 2 (1), 13-21, 2016
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Structure of metamaterial unit cell
The designed structure of the metamaterial unit
cell is rectangular double spiral rings. It is
simulated using HFSS simulation tool and the
simulation results are calculated. The simulation
setup used for HFSS computations is described in
figure 5, where the unit cell of metamaterial is
surrounded by an air medium and the z polarized
incident electromagnetic plane wave propagates
along the y direction.
Hence, the direction of the magnetic field vector
is along the x axis and this is perpendicular to the
resonator plane. Perfect Electric Conductor (PEC)
boundary conditions are applied along the
boundaries perpendicular to the z-axis and the
Perfect Magnetic Conductor (PMC) boundary
conditions are applied along the boundaries
perpendicular to the x-axis. The remaining two
boundaries are assigned to be the input-output wave
ports, as seen in Figure 5.
The simulated spectra for transmission and
reflection is shown. Characteristics of the
proposed structure were found as a result of
simulation using HFSS in order to analyse and
calculate the effective permittivity and
permeability and then effective refractive index
of the new material using Nicolson Ross-Weir
(NRW) approach [11][12][13] as follows:
(1)
(2)
(3)
Where represents a free-space wave number and
and is substrate thickness between the spirals
rings.
Table 4 shows the dimensions of the proposed unit
cell metamaterial while figure 6 describes the
structure of the unit cell of metamaterial.
Fig. 6: Proposed unit cell of metamaterial structure.
Fig. 5: Setup for HFSS simulations.
Fig. 4: S11 parameter for the designed patch antenna at
17GHz.
Fig. 3: S11 parameter for the designed patch antenna at
8.5GHz.
Table 4: Dimensions of unit cell metamaterial.
Metamaterial
elements
Width
(mm)
Length
L(mm)
Thickness
h(mm)
Space
between
turns
(mm)
Material
The most
outer Ring 4.4 4.4 0.03 ------- Copper
Substrate 5 5 1.5 ------- FR4_epoxy
Spiral 0.4 ------- 0.03 ------- Copper
Turns ------- ------- ------- 0.1 Copper
Aziz et al, Journal of Modeling and Simulation of Antennas and Propagation, ISSN: 2377-1674, Vol. 2 (1), 13-21, 2016
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The simulated spectra for transmission (S21) is
shown.
The simulated spectra for transmission (S21) and reflection (S11) characteristics of the proposed
metamaterial structure are given in Figure 7. In
figure 7, blue and red lines indicate the magnitude
of S21 and S11 respectively. It is clear from the
figure that the structure resonates at ten different
frequencies during the range (1-20) GHz.
Figure 8 shows the retrieved effective
permittivity and permeability of the metamaterial
unit cell using matlab codes. From the figure 8,
simultaneous negative permeability and negative
permittivity occur during the range (1-20) GHz
except for small frequency ranges.
Figure 9 shows the negative refractive index of
the metamaterial unit cell using matlab codes. From
the figure 9, the negative refractive index occurs
during the range (1-20) GHz except for small
frequency ranges.
4. RESULTS AND DISCUSSION
The studied patch antennas are covered by a
different number of metamaterial cells and the
simulated results are explained as follows.
1. Microstrip patch antenna of resonance frequency
2.4GHz covered by 99 cells of metamaterial
according to patch area.
Figure 10 shows the return loss characteristics,
S11, of a metamaterial cover patch antenna. From the
Figure 10 and in comparison with S11 of ordinary
patch antenna, figure 2 concludes that there is a
down shift and increase in the number of resonant
frequency during (1-5) GHz range of frequency.
Fig.7: HFSS predicted scattering parameters S11 and S21for
the unit cell of proposed metamaterial.
Fig. 8: Evolution of real part of permeability and
permittivity according to the frequency.
Fig. 9: Evolution of real part of refractive index according
to the frequency.
Fig.10: Return loss characteristics for the patch antenna
covered by metamaterial at 2.4GHz.
Aziz et al, Journal of Modeling and Simulation of Antennas and Propagation, ISSN: 2377-1674, Vol. 2 (1), 13-21, 2016
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2. Microstrip patch antenna of resonance frequency
8.5GHz covered by 35 cells of metamaterial.
Figure 11 shows the return loss characteristics of a
metamaterial covered patch antenna.
Fig. 11: Return loss characteristics for the patch antenna
covered by metamaterial at 8.5GHz
From the figure 11 and in comparison with S11 of
the ordinary patch antenna in Figure 3, it is
concluded that there is an increase in band width.
The bandwidth of the antennas is from (8.98-14.14)
GHz and the resultant percentage is 44.64% with
respect to center frequency.
3. Microstrip patch antenna of resonance frequency
17GHz covered by 20 cells of metamaterial.
Figure 12 shows the return loss S11 characteristics
of a metamaterial cover patch antenna. From the
Figure 12 and in comparison with S11 of ordinary
patch antenna Figure 4, it is concluded that there is
an increase in the number of resonant frequencies.
4. The effect of metameterial cells on radiation
pattern and antenna gain is studied and is shown in
the following figures (13,14 and 15). It is clear that
this increases the lobbing in antenna radiation
pattern.
Figure (13-a) shows the radiation pattern and
gain of an ordinary patch antenna with a resonant
frequency of 2.4 GHz. Figure (13-b), figure (13-c)
and figure (13-d) show the radiation pattern and
gain of an ordinary patch antenna with 99 MTM
cells for three different resonant frequencies (2.12,
3.52, 4.40) GHz respectively. The antenna gain
increases at the frequencies 2.12 and 3.52 GHz.
Figure (14-a) shows the gain of an ordinary
patch antenna with a resonant frequency of 8.5 GHz
and the best three gains when the antenna is
covered with 35 MTM cells for three different
resonant frequencies (10.06, 11.5, 12.34 GHz) as
shown in figure (14-b), figure (14-c) and figure (14-
d) respectively. On the contrary, the antenna gain
decreases.
Figure (15-a) shows the gain of an ordinary patch
antenna with a resonant frequency of 17 GHz and
the three best gains achieved when the antenna is
covered with 20 MTM cells for three different
resonant frequencies (14.96, 21.08, 23.12 GHz) as
shown in figure (15-b), figure (15-c) and figure (15-
d) respectively. Here, the gain is also decreased.
Figure 13-a: Antenna alone at 2.4GHz.
Figure 13-b: Antenna covered with 99 MTM cells at
2.12GHz.
Fig. 12: Return loss characteristics for the patch antenna
covered by metamaterial at 17GHz.
Aziz et al, Journal of Modeling and Simulation of Antennas and Propagation, ISSN: 2377-1674, Vol. 2 (1), 13-21, 2016
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Figure 13-c: Antenna covered with 99 MTM cells at
3.52GHz.
Figure 13-d: Antenna covered with 99 MTM cells at
4.4GHz.
Figure 14-a: Antenna alone at 8.5GHz.
Figure 14-b: Antenna covered with 35 MTM cells at
10.06GHz.
Figure14-c: Antenna covered with 35 MTM cells at
11.5GHz.
Figure 14-d: Antenna covered with 35 MTM cells at
12.43GHz.
Figure 15-b: Antenna covered with 20 MTM cells
at 14.96GHZ.
Figure 15-a: Antenna alone at 17GHZ.
Aziz et al, Journal of Modeling and Simulation of Antennas and Propagation, ISSN: 2377-1674, Vol. 2 (1), 13-21, 2016
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5. CONCLUSION
This paper studies the electromagnetic response
of metamaterial cells on the performance of a
microstrip patch antenna (band width and radiation
pattern). Three frequency bands of 2.4, 8.5 and
17GHz have been chosen to test the designed
antennas. The simulated results indicate that the
studied rectangular patch antennas covered by
different metamaterial cells resonate with multiple
resonant frequencies except for the case of the
patch reading 8.5GHz. The bandwidth increases to
44.64%. The radiation pattern of the antenna is
divided into multiple lobes and leads to a decrease
in antenna gain except for the case of the patch
operating at a low frequency of 2.4GHz.
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Figure 15-c: Antenna covered with 20 MTM cells at
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Figure 15-d: Antenna covered with 20 MTM cells at
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