Vol. 4, No. 9 September 2013
ISSN 2079-8407
Journal of Emerging Trends in Computing and Information Sciences
©2009-2013 CIS Journal. All rights reserved.
http://www.cisjournal.org
Aperture-Coupled Hexagonal Shaped Dielectric Resonator Antenna for
Wideband Applications
1
Abdulkareem S. Abdullah, 2 Asmaa H. Majeed
Department of Electrical Engineering, College of Engineering, University of Basrah, Basra, Iraq
ABSTRACT
In this paper, an elliptical slot fed hexagonal shaped dielectric resonator antenna (DRA) with wideband operations is
presented. The Elliptical slot represents the coupling mechanism between the resonator and the micro strip line, and the
micro strip feed line is positioned at right angle to the center of the slot for efficient coupling. The DRA and slot are both
resonant structures, and together yield double resonant structures with low cross polarization levels and identical radiation
pattern. With proper design, the two resonances can be merged to achieve wide bandwidth. A comprehensive parametric
study is carried out to analyze the characteristics of the proposed antenna. Simulation results show that the proposed DRA
has a 10 dB impedance bandwidth of 47.53% from 2.2446 GHz to 3.8098 GHz.
Keywords: Micro strip antenna, Dielectric resonator, Aperture-coupling, Wide-band application
1. INTRODUCTION
Dielectric resonator antennas (DRAs) have
received much attention in the last two decades due to
several attractive characteristics such as high radiation
efficiency, light weight, and low profile [1]. DRAs have
different commonly used shapes such as cylindrical,
rectangular, spherical and hemispherical. DRAs with
simple geometry and low permittivity give very narrow
bandwidth which is less than 10% [2]. The shape of the
DRA plays an important role in bandwidth enhancement
[2-3], and nowadays lots of researches have been reported
on the bandwidth enhancement of DRAs. Stacking the
different DRAs and modifying the shapes gives a
reasonable increase in bandwidth. [4-5]. DRAs are easy to
excite through different feeding mechanisms such as
coaxial probe, aperture-coupled, micro strip line, and coplanar waveguide (CPW) feed [6-7]. In aperture-coupled
method, the substrate is placed on the back side of the
ground plane to provide isolation between the antenna and
the feed circuit. It can also prevent the radiation due to the
surface wave generation if placed on the same side of the
DRA. As the micro strip line can be extended by a
distance beyond slot, this extension behaves like an open
stub. By adjusting the length of the stub, the impedance
match to micro strip line can be improved [8].
mm). The ground plane is printed on the substrate with a
dimension of 75x55mm2, which is small enough to meet
the circuit boards for many wireless communication
applications. A ceramic material of Rogers TMM10 (ε r =
9.2, tanδ = 0.0022) with dimensions of D L = 22.7mm and
a height of h 1 =11.5 mm is used for the DRA structure,
which is offset from center point. An elliptical shape slot
with large slot radius S L and small slot radius S w is etched
on the ground plane as a feeding mechanism for coupling
and bandwidth enhancement. The slot dimensions are
taken in terms of λ o , where λ o is the free space
wavelength in mm. A 50Ω micro strip feed line with L f =
48.25 mm and L w = 3.98 mm is used for impedance
matching. At the tip of micro strip feed line, a 50Ω
coaxial SMA connector is connected for feeding
microwave power.
P
P
P
P
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
3. PARAMETRIC STUDY
Parametric study of the proposed antenna is
carried out by using Computer Simulation Technology
(CST) microwave studio suite TM 2010 [9]. It is an
electromagnetic simulator based on finite integration
technique (FIT).
P
P
In this paper, a novel wideband elliptical slot-fed
hexagon dielectric resonator antenna is presented. The
shape and size of the slot have significant impact on the
coupling between feed line and dielectric resonator. The
improvement in bandwidth is due to the flexibility offered
by the slot length and coupling slot size. The simulation
results demonstrate that the proposed DRA achieves an
impedance bandwidth of 47.53%.
2. ANTENNA GEOMETRY
The geometry of the proposed wideband regular
hexagonal shaped DRA is shown in Fig. 1. It consists of a
regular hexagonal dielectric resonator and an elliptical
slot-fed mechanism which is printed on a substrate of
Rogers R04232 (ε r = 3.2, tanδ=0.0018, thickness t = 1.64
R
(a)
R
675
Vol. 4, No. 9 September 2013
ISSN 2079-8407
Journal of Emerging Trends in Computing and Information Sciences
©2009-2013 CIS Journal. All rights reserved.
http://www.cisjournal.org
Sw
DL
Lf
SL
LL
Microstrip
feeding
y
x
Fig 3: Comparison of return loss plots at various
small slot radius Sw
(b)
Fig 1: Regular hexagon shape DRA (a) Side view
Fig.4 shows the return loss as a function of
frequency for different stub lengths L L. It can be seen
from the figure that tuning the stub length only slightly
affects the matching of the resonant modes. It was found
that the design is optimized at L L =3.9mm
R
(b) Top view
R
R
R
To achieve the optimum impedance bandwidth, a
parametric study of feeding mechanism was carried out.
Fig.2 shows the simulated return loss of the DRA by
varying the large slot radius of DR (S L ) from 9mm to
10mm. It is clear that the optimum impedance bandwidth
is achieved at large slot radius of 9.25mm.
R
R
Fig 4: Comparison of return loss plots at various
stub length LL
4. THE OPTIMIZED DESIGN
According to the above parametric studies, the
optimized design dimensions of the DRA are given as
follows: D L = 22.7 mm, h 1 = 11.5 mm, S L = 9.25 mm, S w
= 4mm, L f = 48.25 mm and L w =3.98mm. The Proposed
antenna is resonating at frequency covering 2.2446 GHz
to 3.8098 GHz .The return loss obtained is about -51.26
dB as shown in Fig. 5.
R
R
Fig 2: Comparison of return loss plots at
various large slot radius SL
R
R
R
R
R
R
R
R
R
Fig.3 shows the simulated return loss of the DRA
with different small slot radius (S w ). The different values of
(S w ) change the position of the resonant frequency, which
has an influence on the bandwidth of the DRA. It is found
that, the matching condition of the slot-DR is deteriorated
with the decreasing of small slot radius. However, since the
back lobe will be enhanced due to the increasing of small
slot radius, the small slot radius should be chosen properly
considering the matching bandwidth and acceptable back
lobe. The design is optimized at small slot radius of 4mm.
R
R
R
R
Fig 5: Simulated return loss plot of the proposed
DRA.
676
R
Vol. 4, No. 9 September 2013
ISSN 2079-8407
Journal of Emerging Trends in Computing and Information Sciences
©2009-2013 CIS Journal. All rights reserved.
http://www.cisjournal.org
Fig.6 shows the gain of the proposed antenna. It
is noted from the figure that the maximum gain varies
between 5.11dB and 7.366dB across the pass band
(2.2446-3.8098) GHz and is maximum of 7.366dB at
3.4GHz.
(a)
Fig 6: Simulated gain versus frequency of the
proposed DRA.
Fig.7 shows the simulated E and H plane
radiation patterns at different frequencies (2.7GHz,
3.293GHz, and 3.65GHz). It is seen from the radiation
patterns that the antenna is linearly polarized with
broadside radiation.
5. CONCLUSION
A hexagonal shaped dielectric resonator antenna
has been investigated numerically. The proposed DRA
consists of a hexagonal shaped dielectric resonator
antenna excited by an elliptical slot fed mechanism.
Parametric studies have been carried out to optimize the
antenna design. The results show that the designed
antenna offered good impedance bandwidth from 2.2446
GHz to 3.8098 GHz (47.53% of S 11 ≤ -10 dB). It also
provides a maximum gain of 7.366 dB at 3.4 GHz. The
presented antenna is suitable for wideband wireless
communication.
R
(b)
R
(c)
Fig 7: E and H plane patterns at (a) 2.7GHz
(b) 3.293GHz and c) 3.65GHz
677
Vol. 4, No. 9 September 2013
ISSN 2079-8407
Journal of Emerging Trends in Computing and Information Sciences
©2009-2013 CIS Journal. All rights reserved.
http://www.cisjournal.org
operation”, IEEE Transactions on antennas and
propagation, vol.53, no.10, October 2005.
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