1. International Journal of Electronics and Communication Engineering & Technology (IJECET),
INTERNATIONAL JOURNAL OF ELECTRONICS AND
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
COMMUNICATION ENGINEERING & TECHNOLOGY (IJECET)
ISSN 0976 – 6464(Print)
ISSN 0976 – 6472(Online)
Special Issue (November, 2013), pp. 261-268
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IJECET
©IAEME
Design of Omnidirectional Linearly Polarized Hemispherical DRA for
Wideband Applications
Jitendra Kumar1, Navneet Gupta2
Department of Electrical and Electronics Engineering, Birla Institute of Technology and Science, Pilani,
Rajasthan 333031, India
1jitu.kumar87@gmail.com, 2ngupta@pilani.bits-pilani.ac.in
ABSTRACT: A multi segmented hemispherical dielectric resonator antenna (HDRA) centrally
fed by coaxial probe for a broadband application is proposed. This paper discusses four
segments of dielectric material separated by air gaps. This multi segmented HDRA achieves a
10-dB impedance bandwidth of about 80%, while covering the frequency range from 2.8 to 5.2
GHz with improved radiation pattern. This DRA radiates like an electric monopole and
generates omnidirectional linearly polarized field. Ansoft HFSSTM is used to simulate the
dielectric resonator antenna (DRA) performance and the results are verified with another 3-D
EM solver CST-Microwave Studio. Both results are in close agreement with each other, which
shows the validity of proposed design.
KEYWORDS:Dielectric Resonator Antenna, Ultra Wideband, Omnidirectional, Linear
Polarization
I.
INTRODUCTION
In the past two decades, the DRAs have attracted the antenna designers in microwave and
millimeter wave band due to its features like high radiation efficiency, light weight, small size,
low profile, low temperature coefficient of frequency, zero conductor losses, wide impedance
bandwidth and suitable scale in microwave band [1,2]. Dielectric resonators (DRs) of low loss
dielectric material, having medium dielectric constant of 10< <20 are ideally suitable for
antenna applications and compromise can be made between size, operating frequency and
other antenna radiation characteristics. These antennas can also be easily integrated into
portable communication devices [5]. Hemispherical shaped dielectric resonator (DR) is one of
the most basic geometry of DRA. A variant of HDRA was introduced and characterized by D.
Guha et al. [6] in which they had proposed four element quarter hemispherical geometry for
DRA. However, the impedance bandwidth of proposed antenna is limited to 30%.
In order to further improve the bandwidth and other radiation characteristics, multi
segmented HDRA centrally fed by coaxial probe for broadband applications is proposed. This
DRA design uses the conventional technique of the finite ground plane using Teflon (lossy)
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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2. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
( =2.1) as a substrate layer followed by the four segments of dielectric material separated by
air gaps. An inexpensive Rogers R03210 (lossy)( =10.2) are used for segmented DR elements.
Two resonant modes in four segments structure have been successfully exploited at 3GHz and
4.8GHz.
(a)
(b)
Fig. 1: Four segmented HDRA: (a) Front view with different dimension, (b) Top view
with four DR elements
II.
DESIGN AND OPTIMIZATION
The antenna configuration and the geometry of the DRA are shown in Fig.-1. The fundamental
modes are divided into two modes: TE111 and TM101. Antenna design simulated on the Ansoft
HFSSTM [9] (based on finite element method) as well as on CST microwave studio [10] (based
on the finite integration method).
The theoretical resonant frequency and radiated Q-factor for fundamental modes is given as
[12]
= 4.7713 Re( r)/r
(1)
Where K0 is free space wave number and r is radius of the segmented hemisphere of DR
elements in cm
For TE111 Mode:
Re( r) = 2.8316  .
Q= 0.08+0.796 +0.01226 -3.10 
For TM101 Mode:
Re( r) = 4.47226  .
For  < 20
Q = 0.723+0.9324 -0.0956 -0.00403 -5.10 
For  > 20
Q = 2.621-0.547 +0.01226 -2.59*10 
(2)
(3)
(4)
(5)
(6)
A parametric study of the proposed DRA is carried out using Ansoft HFSSTM which is based on
finite element method. The SMA connecter’s probe length was optimized using Ansoft HFSSTM
for L= 9.1, 9.7, 10.3, 10.6, 10.9, 11.3, 11.6 and 11.9 mm from the upper layer of substrate and is
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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3. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
shown in Fig. -2. It is observed that a very well optimized probe length at L=10. 9mm has a
better impedance matching than another.
Fig. 2: Reflection coefficient of Omnidirectional DRA as a function of frequency for different
DRA’s Probe length of L=9.1, 9.7, 10.3, 10.6, 10.9, 11.3, 11.6 and 11.9mm from the upper layer
of substrate
The effect of the variation of radius (r) in the segmented hemispherical DR elements of the DRA
is also studied and is shown in Fig.-3. It is found that as ‘r’ increases, the range of the reflection
coefficientS11 decreases at 10-dB. Best optimized radius of DR elements is found at r=20mm.
Fig. 3: Reflection coefficient of Omnidirectional DRA as a function of frequency for different
radius r=20, 20.5, 21, 22, 23, 24 and 25mm of DR elements.
The characteristic impedance of the antenna is controlled by the length of the probe line of
SMA connector and height of the substrate. From the equations (1 to 5) and simulation results,
the following observations were made for the best optimum dimensions of DRA:
 Element#1= Element#2= Element#3= Element#4, all four DR elements have
radius of r=20mm.
 Air-gap (g) separator between the DR elements is 1mm.
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B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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4. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
 The dielectric substrate is of 1mm thickness and 35mm in radius.
Center fed probe of SMA connector is of length L=10. 9mm from the upper layer of substrate.
III.
RESULTS AND DISCUSSIONS
The reflection coefficient curve of the antenna is shown in Fig.-4 that is simulated onAnsoft
HFSSTM and CST microwave studio. The impedance bandwidth covers the frequency range
from 2.8 GHz to 5.2 GHz approximate for S11< -10dB, and shows good agreement with the both
results. An impedance bandwidth of 80% is obtained, which is wide enough for normal DRA
applications. It is also observed that two resonances at 3 GHz and 4.8 GHz exist in the
frequency band.
Fig.4:Comparison to Return loss of DRA on Ansoft HFSSTM& CST microwave studio
Fig. 5 shows the radiation pattern of DRA and it is observed that the proposed antenna has a
very good omnidirectional pattern at 3GHz.
(a)
(b)
Fig. 5: Omnidirectional gain at 3GHZ: (a) 3-D radiation Pattern, (b) Polar plot
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5. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
The proposed DRA is also studied for far field radiation pattern. Figure-6 shows the radiation
pattern in polar form at two different frequencies (3GHz and 4.8GHz), here it is clear observed
that the antenna radiation in the broadside direction also.
(a) (b)
(c)(d)
Fig. 6: Gain of proposed antenna: (a) HFSS result at 3GHz, (b) CST result at 3GHz, (c) HFSS
result at4.75GHz, (d) CST result at4.8GHz
As proposed DRA has broadside radiation pattern, the antenna efficiency is estimated from the
simulated far field gain. The proposed DRA achieves more than 98% antenna efficiency with
most of the band. The radiation patterns obtained at two frequencies are shown in Fig. 7, which
shows a set of representing the result of the gain verses theta angle for different values of Ø
(phi). It is observed that instead of Ø =90 degree, the plane makes no difference from Ø =0 &45
degrees for both resonant frequencies of DRA.
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6. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
Fig. 7: Cartesian plot of Gain Vs Theta
The results obtained from Ansoft HFSSTM were verified with another 3-D EM solver CST
Microwave studio and results are tabulated in Table-1.So from the application point of view we
can see the result obtained from both simulators are almost same.
AnsoftHFSSTM
CSTMicrowave Studio
I
II
I
II
3GHz
4.75GHz
3GHz
4.8GHz
-15dB
24 dB
-23dB
-19 dB
1.01
4.38
0.8
4.2
131.4
43.1
125.1
53.7
98.8%
99.2 %
98.2%
97.5%
57dB
42 dB
40dB
40 dB
Omnidirectional
Linear
Omnidirectional
Linear
Linear
Slant
Linear
Slant
Table 1: Comparison between different parameters of DRA obtained with Ansoft HFSSTM and
CST Microwave Studio simulations
Parameters
Resonance
Resonance Frequency
Return Loss
Gain (dB)
Beam Width (Degree)
Radiation Efficiency
Axial Ratio
Polarization
IV.
CONCLUSION
The centrally probe fed omnidirectional linear polarized DRA has been studied and
successfully design a multi segmented omnidirectional linear polarized wide band DRA. In this
work a modified design of four segmented hemispherical DRA with enhanced bandwidth and
improved radiation is achieved.
In the proposed design the DR element is separated by air gap that results in the improvement
of the bandwidth. The impedance bandwidth of this antenna is about 80% covering the
frequency range from 2.8 to 5.2 GHz for reflection coefficient less than -10dB which is more
than double compare to conventional HDRA. In comparison to conventional HDRA, this design
significantly reduces the size of the antenna also.
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
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7. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
V.
ACKNOWLEDGEMENT
The authors would like to thank Mr. Amitesh Kumar, from the Society for Applied Microwave
Electronics Engineering & Research (SAMEER), Kolkata, India for his help in getting simulation
work reported in this paper.
REFERENCES
[1]K. M. Luk and K. W. Leunge, Dielectric Resonator Antenna, (Eds. Baldock, U.K: Research
study press limited, London, 2003).
[2]S. A. Long, M. W. McAllister, and L. C. Shen, The resonant cylindrical dielectric cavity
antenna, IEEE Trans. Antennas Propaga, 31(5), 1983, 406–412.
[3]P. Rezaei, M. Hakkak and K. Forooraghi, Design of wide band dielectric resonator antenna
with two segment structure in Progress In Electromagnetic Research, PIER 66, 2006, 111-124.
[4]A.Petosa, A. Ittipiboon, Y. M. M. Antar, and D.Roscoe, Recent advances in dielectric resonator
antenna technology, IEEE Antenna and Propagation Magazine, 40(3), 1998, 35-48.
[5]Y. M. Pan, K. W. Leung, and K. Lu, Omnidirectional Linearly and Circularly Polarized
Rectangular Dielectric Resonator Antennas, IEEE Trans. Antennas Propagation, 60(2), 2012,
751-759.
[6]D. Guha, B.Gupta, C. Kumar, and M. M. Antar, Segmented Hemispherical DRA: New Geometry
Characterized and Investigated in Multi-Element Composite Forms for Wideband Antenna
Applications, IEEE Trans. Antennas Propagation, 60(3), 2012, 1605-1610.
[7]D. Guha, Bidisha Gupta, and Y. M. M. Antar, Hybrid Monopole-DRAs using Hemispherical/
Conical-Shaped Dielectric Ring Resonators: Improved Ultra-Wideband Designs, IEEE Trans.
Antennas Propaga. 60(1), 2012, 393 – 398.
[8]A.Rashidian, K. Forooraghi, and M. Tayfeh-Aligodarz, Investigations on two-segment
dielectric resonator antennas, Microwave and Optical Technology Letters, 45(6), 2005, 533–
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[9]An Introduction to HFSS: Fundamental, Principles, Concepts, and Use Ansoft Corporation,
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[10]CST GmbH 2010 CST MICROWAVE STUDIO(r) User Manual V. 10, Darmstadt, Germany
(www.cst.de).
[11]S. A. Long and M.W. McAllister: Resonant Hemispherical Dielectric Antenna, IET
Electronics Letters, 20(8), 1984, 657-659.
[12]A. Petosa: Dielectric Resonator Antenna Handbook, (Artech House, Norwood,
Massachusetts, USA; 2007).
BIOGRAPHY
Jitendra Kumar is currently working towards the Ph.D. degree in the
Department of Electrical and Electronics Engineering, Birla Institute of
Technology and Science, Pilani, (BITS-Pilani) Rajasthan, India. He received
the Associate degree in Electronics & Telecommunication from The
Institution of Electronics and Telecommunication Engineers (IETE), New
Delhi, India, in 2004 and M.Tech. degree in Microwave Electronics from
University of Delhi, South Campus, India, in 2008. His research interests are
dielectric resonator antennas and design of microwave planner and passive components.
International Conference on Communication Systems (ICCS-2013)
B K Birla Institute of Engineering & Technology (BKBIET), Pilani, India
October 18-20, 2013
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8. International Journal of Electronics and Communication Engineering & Technology (IJECET),
ISSN 0976 – 6464(Print), ISSN 0976 – 6472(Online), Special Issue (November, 2013), © IAEME
Dr. Navneet Gupta obtained M.Sc. (Physics-Electronics) in 1995 from H.N.B
Garhwal Central University (HNBGU), Srinagar, India with first rank in the
University. He received M.Tech in Materials Technology in 1998 from Indian
Institute of Technology (IIT-BHU) (formerly IT-BHU). He did his Ph.D. in the
field of Semiconductor Devices in 2005 from HNBGU. Presently, he is
Assistant Professor and Convenor-Departmental Research Committee in
Electrical and Electronics Engineering Department, Birla Institute of
Technology and Science, Pilani, (BITS-Pilani) Rajasthan, India. He has guided 1 Ph.D. student
and is currently guiding 4 Ph.D. candidates. He is on doctoral advisory committee for 6 Ph.D.
students. He completed 2 sponsored research projects from UGC and DST. His research
interests include Semiconductor Device Modelling, RF-MEMS, Material Selection and Antenna
Design. He is life member of several international and national professional bodies. He has
over 50 research publications (of which 21 are in reputed peer reviewed international and
national journals with good impact factors, and 29 in conference proceedings.). He has
published six books in the areas of engineering physics and electronics engineering. He
received the Bharat Jyoti Award in 2011 by IIFS, New Delhi, India, DST Young Scientist Award
(Fast track Scheme) in Physical Sciences in 2007 and Gold Medal in M.Sc. His biography is
included in Marquis Who's Who in World and Marquis Who's Who in Science and Engineering.
He is expert reviewer of over 5 International Journals. He reviewed three books of Oxford
University Press, Pearson Education and Tata McGraw Hill publishers.
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