International Journal of Engineering Trends and Technology (IJETT) – Volume 5 Number 6 - Nov 2013
Design of a Wideband Cylindrically Conformed
H-Shaped Slot Antenna for Space Communication
Shrikant Verma
Department of Electronics and communication,
Jabalpur Engineering College, Jabalpur
Abstract: A simple and compact wideband cylindrically
conformed H-shaped slot antenna is presented in this paper.
Proposed antenna is composed of an H-shaped slot on the ground
plane which is conformed on a cylindrical surface. Different
substrate materials has been analyzed and Rogers RT/duroid
5880 (Ɛr= 2.2) shows better results. Simulation results has been
observed for different curvature of conformal antenna. The
operating bandwidth of proposed conformal slot antenna exists
over Ku and K bands. An impedance BW (S11≤-10db) of 2.75 Ghz
(16-18.75 Ghz) and percentage BW of 15.77% is achieved.
Maximum gain of 23.86 dB at Ɵ= 51.34º at resonant frequency is
observed. Radiation results has been simulated by using FEM
based simulation software Ansoft HFSS Ver 13.
Index terms: H-shaped slot antenna, wideband, conformal
antenna, HFSS Ver 13.
I.INTRODUCTION
Wideband conformal antenna with minimum physical
protrusions are important in many radar and communication
applications for meeting stringent aerodynamic and scattering
requirements [1-2]. More and more conformal antennas are
used in communication, radar and navigation technology. The
possibilities of conforming them in a determined shape makes
them attractive for aircraft, automobiles or ships, where
aerodynamic may well be improved by adjusting the antennas
to the contour of the vehicles. Microstrip antennas are superior
to conventional antenna due to their low profile, compact size,
conformability to planar and non-planar surfaces, simple and
inexpensive structure, robustness, compatibility with MMIC
designs [3][10][11][13]. The slot antenna fed by microstrip
line is one type of microstrip antenna which has special
advantages such its simple structure, less conductor loss, and
better isolation between the radiating element and feeding
network [14-16]. The slot antennas can also provide the merits
of small size, low cost and easier integration with other
circuits and conformability to a shaped surface [17]. These
antennas also have some demerits like low power, low
ISSN: 2231-5381
efficiency and small bandwidth [10][11]. Lots of work has
been done to make these antenna suitable for wideband
applications. Another significance of using a wideband
antenna is the no. of antennas mounted on the surface of
aircrafts or high-speed vehicles can be reduced[1].
In this paper we proposed a conform microstrip patch antenna
which has a wide impedance bandwidth, compact size and thin
enough to avoid extra drag. Ideally an antenna having paper
thin structure would best suit for aerodynamic and mechanical
structures. These antennas neither disturb the aerodynamic
flow, nor it would protrude inwardly to disturb the mechanical
structure of missile, aircraft or other vehicle. A planar dual
band H-shaped slot antenna for WLAN is reported in [17]. Fig
1 shows the planar antenna structure. The cylindrically
conformed model of above discussed planar antenna is
presented in this paper with some minor modifications in the
design to enhance the radiation characteristics and simplicity
of the antenna. The antenna structure is simulated using FEM
based software HFSS Ver 13. Simulation is done with
different substrate material and different central angles,
which is made by the curvature of antenna at the center of
cylindrical surface, to achieve better radiation properties &
wider bandwidth. Sections II will discuss about the design
specifications of the proposed antenna. In section III the
simulation results of planar and conformal antenna are
discussed.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 Number 6 - Nov 2013
Fig 1. Geometry of planar H-shaped slot antenna.
TABLE 1 Geometry parameters of Antenna 1
________________________________________________
Parameters
Wg
Lg
s
h
d
L
W
a). side view
g
________________________________________________________
Value (mm)
23
32
7.5
1.6
9
24
17
1.1
_________________________________________________
II. ANTENNA DESIGN
The geometry and configuration of the planar H-shaped slot
antenna is shown in fig 1. The requirement of conformal
antenna ,which have to be wraped or mounted over the curved
surface of aircrafts or vehicles, is the substrate height shuold
keep as low as possible. Such antennas does not cause any
extra drag and aerodynamic flow can also be maintained. In
this paper we also proposed an structure with low profile and
reduced antenna height. The planar structure of antenna is
reported previously in [17]. With some minor modification in
the antenna geometry we proposed a wideband slot antenna.
Antenna height is kept constant at h=1.6mm. The proposed
antenna structure is composed of an H-shaped slot on the
ground plane with size of 23mm×32mm. The antenna is fed by
microstrip line at its top. The total external size of H-shaped
slot is W×L with the depression part’s size d×m. The antenna
parameters are given in Table1. The proposed conformal
antenna is designed in two steps. In first step we analyzed the
radiation characteristics of the modified planar H-shape slot
antenna with different substrate material. Then we conform
the antenna on the cylindrical suface of different radius. Hence
simulations are done with different curvatures. Proposed
conformal antenna designed in HFSS is shown below in fig 2.
ISSN: 2231-5381
b). Top view
Fig 2. Conformal antenna model designed in HFSS
III.SIMULATION RESULTS
The performance of the proposed antenna such as impedance
bandwidth, radiation pattern and gain are simulated by HFSS
Ver 13.
The simulated impedance bandwidth for different substrate
material and different central angle are shown in fig 3& 4.
Table 2 shows the impedance BW corresponding to different
subs trate material. Rogers RT/duroid 5880 (tm) shows wider
bandwidth hence this material is selected for the design.
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 Number 6 - Nov 2013
Fig 3. Variation of return loss with different substrate material.
Fig 4. Variation of return loss with different central angle.
The conformal antenna is simulated for different central angle
i.e. for different radius of the cylindrical surface on which the
slot antenna is wraped. Antenna with cylinder radius of 80 mm
to 100 mm (i.e. central angle of 13.17º to 16.46º) has been
simulated and results shown in fig 4. It can be seen from fig 4
that impedance bandwidth is approximately fixed but the
return loss varies. Minimum return loss of -49 dB is achieved
for 15.49º at 17.676 Ghz. Fig 5 shows comparison of RL b/w
planar and conformal antenna. Here it is clear that impedance
BW of both the antennas are approximately similar but a huge
difference can be seen in RL. Minimum RL for planar and
conformal antennas are -22dB and -49dB respectively.
TABLE 2. impedance bandwidth corresponding to different substrate
material.
Substrate material
Dielectric constant (Ɛr)
Impedance bandwidth
(Ghz)
Rogers RT/duroid
5880 (tm)
2.2
3.16
Rogers RT/duroid
6002 (tm)
2.94
3.09
Rogers RO4003(tm)
3.55
2.85
Quartz_glass
3.78
2.68
Fig 5. Comparison b/w return losses of planar and conformal antenna.
The simulated radiation pattern of planar and conformal
antennas are shown in fig.6. radiation patterns are simulated in
azimuth plane and elevation plane at resonant frequency
17.676 Ghz. Generally slot antennas are bidirectional radiators
i.e. they radiates both side of the slot. But here it can be seen
from fig 6 that maximum energy radiates in front direction of
slot. So the radiation pattern of proposed antenna
unidirectional.
E1-plane(ф=0º)
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 Number 6 - Nov 2013
E2-plane(ф=90º)
Fig 6. Simulated radiation patterns (Elevation and Azimuthal planes) at
17.676 Ghz.
IV.CONCLUSION
A wideband cylindrically conformed H-shaped slot antenna is
presented in this paper. Antenna design is simple, compact and
applicable. Impedance bandwidth of 2.75 Ghz (16-18.75 Ghz)
is achieved with minimum RL of -49 dB. This antenna shows
wideband characteristics and unidirectional radiation patterns
with low RCS. This antenna can be easily mounted on curved
surface of aircrafts, missiles and other vehicle. Overall, it can
be concluded that this type of antenna is excellent candidate
for various wideband radar and space applications.
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H-plane(Ɵ=90º)
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International Journal of Engineering Trends and Technology (IJETT) – Volume 5 Number 6 - Nov 2013
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