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Journal ArticleDOI

Aperture-Coupled Asymmetric Dielectric Resonators Antenna for Wideband Applications

TL;DR: In this paper, a compact dielectric resonator antenna (DRA) for wideband applications is proposed, which consists of two cylindrical DRA resonators that are asymmetrically located with respect to the center of a rectangular coupling aperture.
Abstract: A compact dielectric resonator antenna (DRA) for wideband applications is proposed. Two cylindrical dielectric resonators that are asymmetrically located with respect to the center of a rectangular coupling aperture are fed through this aperture. By optimizing the design parameters, an impedance bandwidth of about 29%, covering the frequency range from 9.62 to 12.9 GHz, and a gain of 8 dBi are obtained. Design details of the proposed antenna and the results of both simulation and experiment are presented and discussed.

Summary (2 min read)

Introduction

  • Two cylindrical dielectric resonators which are asymmetrically located with respect to the center of a rectangular coupling aperture are fed through this aperture.
  • By optimizing the design parameters, an impedance bandwidth of about 29%, covering the frequency range from 9.62 GHz to 12.9 GHz, and a gain of 8 dBi are obtained.
  • Since the first proposal in 1983 [1], dielectric resonator antennas (DRAs) have received increasing interest due to their many attractive features, such as high radiation efficiency, smaller size, the freedom to design their shape (rectangular, cylindrical, spherical, etc.) and their feeding structure, for example probe, microstrip line, slot or coplanar line.
  • To overcome this limitation, various bandwidth enhancement techniques have been developed over the last few decades.
  • A single slot here feeds the two DRs in such a way that more design freedom can be obtained, as the two DRAs can resonate at slightly different frequency resulting in a wider bandwidth.

II. ANTENNA GEOMETRY

  • The geometry of the proposed asymmetric wide band antenna is illustrated in Figure 1.
  • The feed microstrip line is placed symmetrically with respect to the coupling aperture.
  • If the slot is modeled as a shunt impedance connected to the feed line, then the stub can be visualized as a reactance canceller.
  • Practical experience has shown that the stub length should be close to λg/4 [8], and optimization started from this point.
  • Since the two DRAs are asymmetrically located with respect to the slot, then two nearby resonance frequencies are excited leading to wide bandwidth operation.

III. PARAMETRIC STUDY

  • In this section the influences of various parameters on the response of DRA antennas are discussed.
  • Figure 2 shows the simulated reflection coefficient as function of frequency for various slot lengths sl.
  • As the aperture length is reduced the (1) input resistance of the antenna decreases.
  • Figure 6 shows that moving the lower DRs along the length of the slot affects the bandwidth and matching, and a good compromise has been obtained for the position yd1 = - 2.3 mm.
  • Thus the off-set positioning has given one more degree of freedom for the design optimization.

VI. THE OPTIMIZED DESIGN

  • Based on the detailed parametric studies, the optimum dimensions obtained for the antenna are listed in Table 1, and used in the fabrication of the antenna shown in Fig.
  • Figure 9 illustrates the simulated and measured antenna gain in the broadside direction of the proposed antenna.
  • It should be noted that the simulated gain curve assumes an ideal feeding network, whereas the measured results include the insertion loss of the feeding network used, hence there are local discrepancies.
  • Figure 11 shows the simulated and measured normalized radiation patterns at resonance frequencies of 10.8 GHz and 12 GHz.
  • The electric and magnetic fields distributions are plotted on the xz and xy planes respectively.

V. CONCLUSIONS

  • A compact DRA for wideband applications has been demonstrated.
  • The use of DRs can enhance the performance of the antenna.
  • An impedance bandwidth of about 29%, covering the frequency range from 9.62 GHz to 12.9 GHz and a realized gain of 8 dBi are obtained.
  • CST: Microwave Studio based on the finite integration technique, 2011. [11].
  • Kwai-Man Luk, and Kwok-Wa Leung, Dielectric Resonator Antennas, by Research Studies Press ltd, Baldock, Hertfordshire, England, 2003.

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IEEE Antennas and Wireless Propagation Letters, vol. 13, May 2014, pp. 927-930; ISSN: 1536-1225
Aperture-Coupled Asymmetric Dielectric Resonators Antenna for
Wideband Applications
A.H. Majeed, A.S. Abdullah, F. Elmegri, K.H. Sayidmarie, R.A. Abd-Alhameed and J.M. Noras
Abstract: A compact dielectric resonator antenna (DRA)
for wideband applications is proposed. Two cylindrical
dielectric resonators which are asymmetrically located with
respect to the center of a rectangular coupling aperture are
fed through this aperture. By optimizing the design
parameters, an impedance bandwidth of about 29%,
covering the frequency range from 9.62 GHz to 12.9 GHz,
and a gain of 8 dB
i
are obtained. Design details of the
proposed antenna and the results of both simulation and
experiment are presented and discussed.
Index Terms: Dielectric Resonator Antenna (DRA), aperture
coupling, asymmetric shape.
I. INTRODUCTION
Since the first proposal in 1983 [1], dielectric resonator
antennas (DRAs) have received increasing interest due to
their many attractive features, such as high radiation
efficiency, smaller size, the freedom to design their shape
(rectangular, cylindrical, spherical, etc.) and their feeding
structure, for example probe, microstrip line, slot or
coplanar line. However, one major drawback of the DRA is
limited bandwidth. For a single-mode excitation, the
bandwidth is often below 10%, which is not sufficient for
many wideband applications. To overcome this limitation,
various bandwidth enhancement techniques have been
developed over the last few decades. One approach is to
utilize different features of the dielectric resonators (DRs),
such as structures of high aspect ratio [2], stacked multiple
DRs with different materials to merge multi-resonance
operation [3- 4], and inserting an air gap in the DR to lower
the Q-factor [5-6]. In [7] a single cylindrical DR is excited
by two crossed slots. The centers of the two slots are set at
different positions and taking into consideration the partial
independence of the slot modes from the DRA mode, a
wider bandwidth was attained.
In this paper, a novel wideband slot-fed asymmetric
dielectric resonator antenna is presented. A pair of
cylindrical DRs is placed adjacently and asymmetrically
with respect to the feeding rectangular aperture. A single
slot here feeds the two DRs in such a way that more design
freedom can be obtained, as the two DRAs can resonate at
slightly different frequency resulting in a wider bandwidth.
II. ANTENNA GEOMETRY
The geometry of the proposed asymmetric wide band
antenna is illustrated in Figure 1. The prototype antenna is
fabricated on 30mm
25mm FR4 substrate with relative
permittivity of
rs
=4.5, a loss tangent of 0.017, and a
thickness t = 0.8 mm. The feed microstrip line is placed
symmetrically with respect to the coupling aperture. The
microstrip line dimensions were calculated using empirical
formulas given in [7] resulting in length l
f
=22.5mm and
width w
f
=1.5mm. A rectangular aperture (slot) of length s
l
and width of s
w
is etched on the ground plane. The
dimensions of the aperture influence the resonant frequency
of the structure and the amount of the undesired radiation in
the back direction of the antenna. They also determine the
coupling between the radiating DRs and the microstrip line.
At the end of feed line there is a ‘stub’ of length l
stub
as
shown in Figure 1. If the slot is modeled as a shunt
impedance connected to the feed line, then the stub can be
visualized as a reactance canceller. Practical experience has
shown that the stub length should be close to λ
g
/4 [8], and
optimization started from this point. An alumina material of
alumina-96pct, with
rd
= 9.4, diameter D = 6mm and a
height h = 9 mm is used for the DR structure. The two DRs
are offset from the center of the slot (y
d
y
d1)
as shown in
Figure1 (a).
The resonant frequency of a single segment cylindrical
DRA (CDRA) excited in the HEM
11δ
mode can be written as
[9],
2
0.157871.1
2
)(
2h
a
h
a
a
c
GHzf
r
r
where a=D/2, with D the diameter of the CDRA, c the
velocity of light, h the height of the CDRA above ground
plane, and
r
the relative permittivity of the CDR material.
With dimensions D = 6mm, h = 9 mm and
r
=9.4, the
calculated resonance frequency according to Equation 1 was
found to be 10.63 GHz. The slot length and the
permittivities of the substrate and the DRA determine the
frequency of the slot resonance. The DRA modes depend on
the DR dimensions and permittivity, as well as on the
feeding mechanism. Since the two DRAs are
asymmetrically located with respect to the slot, then two
nearby resonance frequencies are excited leading to wide
bandwidth operation.
III. PARAMETRIC STUDY
In this section the influences of various parameters on the
response of DRA antennas are discussed. The antenna
structure is analyzed and optimized using Computer
Simulation Technology (CST) microwave studio suite 2011,
which is an electromagnetic simulator based on a finite
integration technique (FIT) [10]. Figure 2 shows the
simulated reflection coefficient as function of frequency for
various slot lengths s
l
. As the aperture length is reduced the
(1)

IEEE Antennas and Wireless Propagation Letters, vol. 13, May 2014, pp. 927-930; ISSN: 1536-1225
input resistance of the antenna decreases. This might be
thought of as decreasing the coupling factor between the
feed line and the antenna. The slot length also affects the
coupling to the DR, as can be seen from the fact that best
matching is obtained for a slot length of s
l
= 6.6 mm. This
analysis shows that slot length has most effect on the
reflection coefficient and the resonant frequency, but it also
affects the impedance bandwidth of the antenna to a lesser
extent.
Figure 3 shows the simulated reflection coefficient of the
DRA with slot width s
w
varied from 0.6 mm to 1.4 mm. It is
clear that the optimum impedance bandwidth is achieved at
a slot width of s
w
= 1.2 mm.
(a)
(b)
Fig. 1: Aperture-coupled asymmetric dielectric resonator antenna (a) top
view and (b) side view with design dimensions and parameters
Fig. 2: Simulated reflection coefficient as a function of frequency for
different slot lengths s
l
with s
w
=1.1mm, l
stub
=4mm, y
d
=3.75mm, y
d1
=-2.1mm.
The effect of the stub length l
stub
is shown in Figure 4,
where
it is clear that tuning the stub length can affect the
bandwidth and matching of the resonant modes. The design
is optimized at l
stub
=4mm, a value close to the estimated one
of λ
g
/4 = 4.08 mm.
Fig. 3: Simulated reflection coefficient as a function of frequency for
different slot widths s
w
with s
l
=6.6mm, l
stub
=4mm, y
d
=3.75mm, y
d1
=-
2.1mm .
The effect of the stub length l
stub
is shown in
Figure 4,
where it is clear that tuning the stub length can
affect the bandwidth and matching of the resonant modes.
The design is optimized at l
stub
=4 mm, a value close to the
estimated one of λ
g
/4 = 4.08 mm.
Fig. 4: Simulated reflection coefficient as a function of frequency for
various stub lengths l
stub
with s
l
=6.6mm, s
w
=1.2mm, y
d
=3.75mm, y
d1
=-
2.1mm .
The effects of asymmetric location of the two DRs were
investigated by moving one of the DRs along the length of
the slot. The results obtained by moving the upper DR are
shown in Figure 5, where it can be seen that the position of
the DR affects the bandwidth and matching. A good
compromise has been obtained for the position y
d
= 3.75
mm. Figure 6 shows that moving the lower DRs along the
length of the slot affects the bandwidth and matching, and a
good compromise has been obtained for the position y
d1
= -
2.3 mm. Thus the off-set positioning has given one more
degree of freedom for the design optimization. The two
values (y
d
= 3.75 mm and y
d1
= -2.3 mm) have been chosen

IEEE Antennas and Wireless Propagation Letters, vol. 13, May 2014, pp. 927-930; ISSN: 1536-1225
as they give best response in bandwidth and matching as
well as resulting in the same resonance frequency of 10.832
GHz.
Fig. 5: Simulated reflection coefficient as a function of frequency for
varying position of upper DR y
d
with s
l
=6.6mm, s
w
=1.2mm, l
l
=4mm, y
d1
=-
2.1mm.
Fig. 6: Simulated reflection coefficient as a function of frequency for
varying position of lower DR y
d1
with s
l
=6.6mm, s
w
=1.2mm, l
stub
=4mm,
yd=3.75mm .
VI. THE OPTIMIZED DESIGN
Based on the detailed parametric studies, the optimum
dimensions obtained for the antenna are listed in Table 1,
and used in the fabrication of the antenna shown in Fig. 7.
The antenna performance was measured with an HP8510C
vector network analyzer. The measured and simulated
reflection coefficients of the proposed antenna are shown in
Fig. 8. The differences between the measured and simulated
results, seen in a shift to higher frequency and general
increase in S
11 ,
may be attributed to the effects of fabrication
inaccuracies, and of the use of glue to fix the DRA, as has
been noticed previously [9]. The presented antenna here
achieves an impedance matching (S
11
< -10 dB band) from
9.62 GHz to 12.9 GHz, i.e. 29%.
Table 1: Dimensions of the optimized antenna.
parameter L
g
W
g
L
f
W
f
D h s
l
Optimum
value/mm
30 25 21 1.5 6 9 6.6
parameter sw Lstub yd yd1
Optimum
value/mm
1.2 4 3.75 -2.3
Fig. 7: Photograph of the fabricated antenna (a) front view and (b) back view
Fig. 8: Simulated and measured reflection coefficient of the proposed DRA
Figure 9 illustrates the simulated and measured antenna
gain in the broadside direction of the proposed antenna. It
should be noted that the simulated gain curve assumes an
ideal feeding network, whereas the measured results include
the insertion loss of the feeding network used, hence there
are local discrepancies. The figure shows that the calculated
gain varies between 5.47 dB
i
and 8 dB
i
with a maximum of
8 dB
i
at 12.8 GHz, while the measured gain varies between
6.34 dBi and 7.72 dBi across the pass band of 9.62-12.9
GHz and it can be said that on average the measurements
are comparable with the prediction.
Figure 10 shows the simulated and measured impedance
for the proposed antenna. The real parts are close to 50 ,
while the imaginary parts fluctuate around zero. The slight
differences between the simulated and measured
impedances are due to the fabrication inaccuracies.
Measurements of the far-field radiation patterns of the
prototype antenna were carried out in an anechoic chamber
using an elevation-over-azimuth positioner, with the
elevation axis coincident with the polar axis (θ=0
o
) of the
antenna’s co-ordinate system. The azimuth drive thus
generates cuts at constant .
The fixed transmitting antenna was a broadband horn
(EMCO type 3115) positioned 4 m from the antenna being
tested. The azimuth positioner was rotated from θ = -180
o
to
180
o
at increments of 5
o
for the selected measurement. Two
pattern cuts, = 0
o
and 90
o
were taken at two selected
operating frequencies for which the matching was optimal.
Figure 11 shows the simulated and measured normalized
radiation patterns at resonance frequencies of 10.8 GHz and
12 GHz. This shows the antenna has a wide radiation field
covering half of space. The field has a low cross-
polarization component and is mainly linearly polarized.

IEEE Antennas and Wireless Propagation Letters, vol. 13, May 2014, pp. 927-930; ISSN: 1536-1225
The back lobe in the radiation pattern is due to a small
amount of radiation from the slot.
Fig. 9: Comparison of simulated and measured antenna gain of the
proposed antenna
Fig. 10: Simulated and measured impedance of the proposed antenna
The magnitude of the electric and magnetic fields at 10.8
GHz and 12.3 GHz are shown in Figure 12. The electric and
magnetic fields distributions are plotted on the xz and xy
planes respectively. It is observed that the magnetic field
variations at 10.8 GHz along specific azimuth direction at
the base of each DRA, look quite similar and with intensity
increasing at higher frequency. Hence, looking carefully at
the variations of electric fields one can conclude that there is
significant evidence of the appearance of a TM
110
/HEM
11
mode of weakly uniform distribution at lower frequency
10.8 GHz and a TM
111
/HEM
112
mode of cycling field
distribution at the higher frequency of 12.3 GHz. The
asymmetry of such DRAs including the smallest ratio of
radius-to-height ratio (D/2h=1/3) supports the existence of
close modes to work over a wide bandwidth [11].
V. CONCLUSIONS
A compact DRA for wideband applications has been
demonstrated. The use of DRs can enhance the performance
of the antenna. The asymmetric location of the pair of DRs
can add another parameter for the designer to optimize the
design. In this study, an impedance bandwidth of about 29%,
covering the frequency range from 9.62 GHz to 12.9 GHz
and a realized gain of 8 dB
i
are obtained.
10.8 GHz
12 GHz
(a)
(b)
Fig. 11: Simulated and measured radiation pattern; (a) in xz plane, (b) in
yz plane; simulated Eθ: dashed line, simulated E: dotted line, measured
Eθ: 'o-o-o’, measured E: solid line.
Electric fields
Magnetic fields
(a)
10.8GHz (b)
12.3GHz
Fig. 12: Magnitude of electric (top, xz plane) and magnetic (bottom, xy
plane) fields distribution for (a) 10.8 GHz, (b) 12.3 GHz.
REFERENCES
[1] S. A. Long, M. W. McAllister, and L. C. Shen, “The Resonant cylindrical
dielectric cavity antenna,” IEEE Trans. Antennas Propag., Vol.AP-31,
No. 3, pp. 406–412, May 1983.
[2] A. Rashidian and D. M. Klymyshyn, On the two segmented and high
aspect ratio rectangular dielectric resonator antennas for bandwidth

IEEE Antennas and Wireless Propagation Letters, vol. 13, May 2014, pp. 927-930; ISSN: 1536-1225
enhancement and miniaturization,” IEEE Trans. Antennas Propag.,
Vol.57, No. 9, pp. 2775–2780, 2009.
[3] R. Chair, A. A. Kishk, K. F. Lee, and C. E. Smith, “Wideband flipped
staired pyramid dielectric resonator antennas,” Electron. Lett., Vol. 40,
No. 10, pp. 581–582, 2004.
[4] A. G. Walsh, S. D. Young, and S. A. Long, An investigation of stacked
and embedded cylindrical dielectric resonator antennas,” IEEE Antennas
Wireless Propag. Lett., Vol. 5, pp. 130–133, 2006.
[5] T. A. Denidni, Q. Rao, and A. R. Sebak, “Broadband L-shaped dielectric
resonator antenna,” IEEE Antennas Wirel. Propag. Lett., Vol. 4, pp. 453–
454, 2005.
[6] L. Z. Thamae and Z. Wu, “Broadband bowtie dielectric resonator
antenna", IEEE Trans. Antennas Propag., Vol.58, No. 11, pp. 3707-3710,
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[7] G. Almpanis, C. Fumeaux, and R. Vahldieck," Offset cross-slot-coupled
dielectric resonator antenna for circular polarization", IEEE Microwave
And Wireless Components Letters, VOL. 16, NO. 8, AUGUST 2006
[8] D. M. Pozar, "Microwave Engineering", 2nd edition, John Wiley & Sons,
New York, 1998.
[9] A. A. Kishk, A. Ittipiboon, Y. M. M. Antar, and M. Cuhaci, “Slot
excitation of the dielectric disk resonator,” IEEE Trans. Antennas
Propag.,Vol. 43, No. 2, pp. 198–201, Feb. 1995.
[10] CST: Microwave Studio based on the finite integration technique,
2011.
[11] Kwai-Man Luk, and Kwok-Wa Leung, Dielectric Resonator Antennas,
by Research Studies Press ltd, Baldock, Hertfordshire, England, 2003.
Citations
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TL;DR: In the class of printed broadband antennas with unbroken ground plane, the proposed antenna achieves minimum volume with good bandwidth and radiation properties, suitable for target scanning applications.
Abstract: A broadband and compact stacked microstrip patch antenna has been developed using stacked configuration. The antenna comprises two parasitic patches stacked above the driven patch fed by shifted microstrip feed and a step transformer between feed and patch to achieve broadband coupling. Cross polarization has been improved by inserting a vertical slot in the direction of feed. The antenna occupies very low volume of ${\mathbf{0}}.{\mathbf{36}}{\lambda _{{\mathbf{o}}}}\,\times\,{\mathbf{0}}.{\mathbf{39}}{\lambda _{{\mathbf{o}}}}\,\times\,{\mathbf{0}}.{\mathbf{096}}{\lambda _{\mathbf{o}}}$ (radiating elements volume), while overall dimensions with ground plane are ${\mathbf{0}}.{\mathbf{7}}{\lambda _{{\mathbf{o}}}}\,\times\,{\mathbf{0}}.{\mathbf{7}}{\lambda _{{\mathbf{o}}}}\,\times\,{\mathbf{0}}.{\mathbf{096}}{\lambda _{\mathbf{o}}}$ . The overall bandwidth achieved is 35% (4.9–7.05 GHz) and a peak gain of 8.2 dBi with average gain of 6 dBi. Antenna radiation patterns are quite unidirectional with ${\mathbf{F}}\text{/}{\mathbf{B}} > {\mathbf{21}}$ dB and significantly low cross-polarization levels, suitable for target scanning applications. In the class of printed broadband antennas with unbroken ground plane, the proposed antenna achieves minimum volume with good bandwidth and radiation properties.

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  • ...As a result, the coupling factor between the feedline and DR is also increases.(13) From Figure 5A, it is observed that as the slot width at port 1 increases from 1 mm to 1....

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Journal ArticleDOI
TL;DR: A comprehensive review of the state-of-the-art techniques and geometries which have been explored in the areas of dielectric Resonator Antennas (DRA) can be found in this article.
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  • ...The concept of multi-element DRAs is further explored in [33], where two cylindrical dielectric resonators that are asymmetrically located with respect to the center of a rectangular coupling aperture are fed through this aperture....

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Journal ArticleDOI
TL;DR: In this article, a new differential microstrip feeding method was proposed for dielectric resonator antenna (DRA) and array with low permittivity, where two parallel microstrip lines with differential signals were placed underneath the rectangular DRA to excite its fundamental $\text{TE}^{x}_{\delta 11}$ mode.
Abstract: A new differential microstrip feeding method is proposed for dielectric resonator antenna (DRA) and array with low permittivity. Two parallel microstrip lines with differential signals are placed underneath the rectangular DRA to excite its fundamental $\text{TE}^{x}_{\delta 11}$ mode. A single-port DRA element is first designed with a balun. The measured −10 dB bandwidth is achieved to be 22% around 2.4 GHz, and the in-band realized boresight gain is around 6 dBi. Then, a 2 × 2 differentially fed DRA array is developed, combining series and parallel feeding networks. An 18.7% bandwidth and an average gain of 12.3 dBi are achieved. The effectiveness of our proposed feeding method has been demonstrated by the good agreement between the measured and simulated results.

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References
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Journal ArticleDOI
TL;DR: In this article, an experimental investigation of the radiation and circuit properties of a resonant cylindrical dielectric cavity antenna has been undertaken, and a simple theory utilizing the magnetic wall boundary condition is shown to correlate well with measured results for radiation patterns and resonant frequencies.
Abstract: An experimental investigation of the radiation and circuit properties of a resonant cylindrical dielectric cavity antenna has been undertaken. The radiation patterns and input impedance have been measured for structures of various geometrical aspect ratios, dielectric constants, and sizes of coaxial feed probes. A simple theory utilizing the magnetic wall boundary condition is shown to correlate well with measured results for radiation patterns and resonant frequencies.

1,434 citations


"Aperture-Coupled Asymmetric Dielect..." refers background in this paper

  • ...S INCE the first proposal in 1983 [1], dielectric resonator antennas (DRAs) have received increasing interest due to their many attractive features, such as high radiation efficiency, smaller size, the freedom to design their shape (rectangular, cylindrical, spherical, etc....

    [...]

Book ChapterDOI
15 Apr 2005
TL;DR: Linearly and circularly polarized conformal strip-fed dielectric resonator antennas (DRAs) are studied in this article, where a parasitic patch is used to excite a nearly degenerate mode.
Abstract: Linearly and circularly polarized conformal strip-fed dielectric resonator antennas (DRAs) are studied in this article. In the latter case, a parasitic patch is used to excite a nearly degenerate mode. The hemispherical DRA, excited in its fundamental broadside TE111 mode, is used for the demonstration. In the analysis, the mode-matching method is used to obtain the Green's functions, whereas the method of moments is used to solve for the unknown strip currents. In order to solve the singularity problem of the Green's functions, a recurrence technique is used to evaluate the impedance integrals. This greatly increases the numerical efficiency. Measurements were carried out to verify the calculations, with good results. Keywords: circularly polarized antenna; dielectric antennas; mode-matching methods; moment methods; parasitic antennas; resonance

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  • ...The asymmetry of such DRAs including the smallest ratio of radius-to-height ratio supports the existence of close modes to work over a wide bandwidth [11]....

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TL;DR: In this article, various multisegment cylindrical dielectric resonator antenna geometries were considered including stacked, core-plugged, and embedded stacked, and the results showed impedance bandwidths up to 68.1% compared to 21.0% for a homogeneous DRA with the same size and resonant frequency.
Abstract: Various multisegment cylindrical dielectric resonator antenna geometries are considered including stacked, core-plugged, and embedded stacked. Results show impedance bandwidths up to 68.1% compared to 21.0% for a homogeneous DRA with the same size and resonant frequency.

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  • ...One approach is to utilize different features of the dielectric resonators (DRs), such as structures of high aspect ratio [2], stacked multiple DRs with different materials to merge multiresonance operation [3], [4], and inserting an air gap in the DR to lower the -factor [5], [6]....

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TL;DR: In this article, the resonance frequencies of the dielectric disk for the HEM/sub 11/ mode are computed numerically in the complex frequency plane and the actual resonance frequency and the Q-factor are obtained.
Abstract: Dielectric disk radiators which are excited by a narrow slot in the ground plane of a microstrip line are investigated. The resonance frequencies of the dielectric disk for the HEM/sub 11/ mode are computed numerically in the complex frequency plane. From the later results, the actual resonance frequency and the Q-factor are obtained. The dielectric disk is made of a high dielectric constant ceramic material with /spl epsivsub r/=22. The radiation patterns and reflection coefficients are measured and presented for several slot lengths and dielectric disk dimensions. The radiation patterns are also computed assuming a magnetic current element, which models the slot and excites the HEM/sub 11/ mode. Good agreement is obtained between the computed and measured results. The results presented here also demonstrate the viability of this type of antenna, which has high dielectric constants an efficient radiator provided the proper mode is excited. >

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  • ...The differences between the measured and simulated results, seen in a shift to higher frequency and general increase in , may be attributed to the effects of fabrication inaccuracies and of the use of glue to fix the DRA, as has been noticed previously [9]....

    [...]

  • ...The resonant frequency of a single-segment cylindrical DRA (CDRA) excited in the mode can be written as [9]...

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TL;DR: In this paper, a broadband inverted L-shaped dielectric resonator antenna (DRA) is proposed for multiband wireless communication applications as digital communication systems, personal communication systems (PCS), universal mobile telecommunication systems (UMTS), and wireless local area networks (WLANs), which offers a bandwidth of 38% (from 1.71 to 2.51 GHz) and stable broadside radiation patterns.
Abstract: In this letter, a broadband inverted L-shaped dielectric resonator antenna (DRA) is proposed. The DRA with the two equiangular-triangle across sections is built on a ground plane and excited by a coaxial probe to provide broadside radiation patterns. The simulated and measured results verify that the proposed antenna offers a bandwidth of 38% (from 1.71 to 2.51 GHz) and stable broadside radiation patterns. The proposed antenna is suitable for multiband wireless communication applications as digital communication systems (DCS; 1710-1880 MHz), personal communication systems (PCS; 1850-1990 MHz), universal mobile telecommunication systems (UMTS; 1920-2170 MHz), and wireless local area networks (WLANs; 2.4-2.485 GHz).

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  • ...One approach is to utilize different features of the dielectric resonators (DRs), such as structures of high aspect ratio [2], stacked multiple DRs with different materials to merge multiresonance operation [3], [4], and inserting an air gap in the DR to lower the -factor [5], [6]....

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Frequently Asked Questions (9)
Q1. What are the contributions in "Aperture-coupled asymmetric dielectric resonators antenna for wideband applications" ?

In this paper, two cylindrical dielectric resonators which are asymmetrically located with respect to the center of a rectangular coupling aperture are fed through this aperture, and an impedance bandwidth of about 29 %, covering the frequency range from 9.62 GHz to 12.9 GHz, and a gain of 8 dBi are obtained. 

Since the two DRAs are asymmetrically located with respect to the slot, then two nearby resonance frequencies are excited leading to wide bandwidth operation. 

In this study, an impedance bandwidth of about 29%, covering the frequency range from 9.62 GHz to 12.9 GHz and a realized gain of 8 dBi are obtained. 

The prototype antenna is fabricated on 30mm 25mm FR4 substrate with relative permittivity of rs=4.5, a loss tangent of 0.017, and a thickness t = 0.8 mm. 

The slot length also affects the coupling to the DR, as can be seen from the fact that best matching is obtained for a slot length of sl = 6.6 mm. 

With dimensions D = 6mm, h = 9 mm and r=9.4, the calculated resonance frequency according to Equation 1 was found to be 10.63 GHz. 

The resonant frequency of a single segment cylindrical DRA (CDRA) excited in the HEM11δ mode can be written as [9], 20.157871.1 2 )( 2h a h a a cGHzf r r where a=D/2, with D the diameter of the CDRA, c the velocity of light, h the height of the CDRA above ground plane, and r the relative permittivity of the CDR material. 

The effect of the stub length lstub is shown inFigure 4, where it is clear that tuning the stub length can affect the bandwidth and matching of the resonant modes. 

8. The differences between the measured and simulated results, seen in a shift to higher frequency and general increase in S11 , may be attributed to the effects of fabrication inaccuracies, and of the use of glue to fix the DRA, as has been noticed previously [9].