294-300 - AJBAS Journal

Australian Journal of Basic and Applied Sciences, 8(4) Special 2014, Pages: 294-300
AENSI Journals
Australian Journal of Basic and Applied Sciences
Journal home page: www.ajbasweb.com
Design Compact Monopole Antenna with Modified Trapezoidal Shaped Ground Plane
for 8.5 GHz Application
H. Nornikman, W.Y. Sam, F.A.M. Mohd, Z.A.A.A. Mohamad, H.A. Badrul, A.O. Mohd
Centre of Telecommunication Researchand Innovation (CeTRI), Department of Telecommunication Engineering, Universiti Teknikal
Malaysia Melaka (UTeM), Hang Tuah Jaya, 76100 Durian Tunggal, Melaka, Malaysia.
Article history:
Received 20 November 2013
Received in revised form 24
January 2014
Accepted 29 January 2014
Available online 5 April 2014
shaped; radar application; reflection
loss; antenna gain
In this work, a monopole antenna with the trapezoidal shaped ground plane had been
fabricated.This antenna is using the technology of microstrip for radar application. The
aim of this work is to improve the gain compared with common microstrip and favored
reflection coefficient bandwidth by inserting a rectangular break at the circular patch
and designs a trapezoidal shape ground plane. The resonant frequency of the antenna is
8.5 GHz and the return loss is better than – 10.00 dB. The design and simulation
process are using Computer Simulation Technology (CST) Microwave Studio
simulation software. The results of measurement and fabrication process are compared
with the simulation result. The result is important in designing an antenna that can
operate in radar application using an Ultra-wideband spectrum.
© 2014 AENSI Publisher All rights reserved.
To Cite This Article: H. Nornikman, W.Y. Sam, F.A.M. Mohd, Z.A.A.A. Mohamad, H.A. Badrul, A.O. Mohd., Design Compact Monopole
Antenna with Modified Trapezoidal Shaped Ground Plane for 8.5 GHz Application. Aust. J. Basic & Appl. Sci., 8(4): 294-300, 2014
Nowadays, due to high demand of the compact size and high gain antennas. The high gain and the compact
size had been the important characteristic in designing the antennas. To achieve the compact size of the antenna
design, a microstrip patch antenna had been used as it had an advantage of smaller cost and also light weight.
Microstrip patch antenna consists of a radiating patch on one side of dielectric substrate which has a ground
plane on the other side. The patch is generally square, rectangular, monopole (Ahmad, B.H., et. al., 2013),
circular (Zani, M.Z.M., et. al., 2010), triangular, elliptical or unique shape such as Minkowski (Malek, F., et. al.,
2012), Sierpinski carpet (Saidatul, N.A., et. al., 2009), Koch Fractal (Ismahayati, A. et. al, 2011) and others.
The design of the directional monopole antenna must meet requirement of the small size for ease of use
when been used for patient monitoring since it application is for the breast cancer imaging by using the
microwave frequency (Nilavalan, et. al., 2007). The requirement design for the antenna is the antenna size, ultra
wideband radiation for short pulse transmission, best impedance and operating bandwidth (Shannon, C. J., et.
al., 2005). There are so many guides on designing the radar based of directive antenna application, and type of
high gain antennas for the application. An example of the high gain type is such as the horn and the Vivaldi
antenna (Lizhong, S., et. al., 2011), while the compact antenna such as the patch antennawith slot (Wang, H., et.
al. 2008, Abd Aziz, et. al, 2013)). But it confronts a lake in its size and the limitation of the bandwidth and
operating frequency (Klemm, M, et. al., 2005, Lu, Y., et. al., 2009).
The size of the antenna is the main attributes to be considered when designing the antenna for the breast
cancer imaging using microwave based. Dramatically, the purpose of this paper is to design the compact and
tolerable high gain with a favored reflection coefficient bandwidth to use in the application. The design of the
trapezoidal ground plane and the parasitic element are precisely done so that the surface current will spread out
to the direction needed. This process will increase the density of the radiation to favored path. The circle break
and the ground plane will also increase the antenna bandwidth of the reflection coefficient.
From the literature review, it is also shown many types of the directional monopole antenna that had been
designed previously. (Locatelli, A., et. al., 2007) had been designed a directional planar ultra-wideband (UWB)
antenna for radar applications.This antenna is focusing to increase the directivity, develop UWB antenna,
acceptable return loss and gain between frequency of 6.0 GHz and 8.00 GHz.
(Mokhtaari, M., et. al., 2008) had been introduced the compact UWB antenna using directional monopole at
the patch and a combination of parabolic-shaped ground plane technique to get the high directivity and high gain
Corresponding Author: H. Nornikman, Centre for Telecommunication Research and Innovation (CeTRI), Faculty of
Electronics, and Computer Engineering, Universiti Teknikal Malaysia Melaka (UTeM), Hang
Tuah Jaya 76100 Durian Tunggal, Melaka, Malaysia.
Tel: +6013-2994948, E-mail: [email protected]
H. Nornikman et al, 2014
Australian Journal of Basic and Applied Sciences, 8(4) Special 2014, Pages: 294-300
antenna. The return loss of this antenna is better than 9.500 dB in the frequency range of 3.100 GHz and 12.600
GHz. The proposed of this parabolic-shaped is to operate as a reflector in UWB frequency range.
(Golezani, et. al., 2012) presented modified directional wide band monopole antenna for radar and also
microwave imaging applications. This antenna also used the symmetrical parabolic-shape ground plane with
some curve modification in the design. The advantages of this symmetrical parabolic-shaped is symmetrical and
optimum convergence of the radiation pattern of the antenna. This antenna operates in the frequency range
between 4.00 GHz and 9.00 GHz with high directional radiation pattern and ultra-bandwidth (UWB) effect.
A radar operates by radiate the electromagnetic energy and detected the echo return from reflecting object
(Toomay, J., et. al., 2004). One of the microwaves imaging application is detecting the breast cancer.
Microwave breast imaging is based on the electrical property contrast between malignant breast tissues and
healthy (Stang, J. P., et. al., 2008, Hariyadi, et. al., 2011). Thesetwo antennas are able to detect the tumors such
as breast cancer in the human body. This proposed antenna works at a frequency of 8.50 GHz for radar
applications with requirement of better – 10.00 dB of return loss.
There are many researches that focused on the radar applicationin the antenna design such as in these
following papers: (Romano, N., et. al, 2009, Hainovich, A. M., et. al, 2008, Beer, S. et. al. 2010, Arima, T. et.
al, 2013).
2. Antenna Design:
The structure of the monopole antenna with the modified trapezoidal shaped ground plane is designed using
CST Microwave Studio software. This antenna consists three main parts – patch antenna with feedline,
substrates and the ground plane. On the front side of the antenna is a semicircular shape patch with the
rectangular shape feedline. The radius of semicircular patch is 7.00 mm from calculating work while 8.00 mm
of dimension after the optimization stage. Fig. 1. Shows the schematic diagram of a monopole antenna with
modified trapezoidal shaped ground plane in different views.
Fig. 1: Schematic diagram of monopole antenna with modified trapezoidal shaped ground plane, (a) front view,
(b) back view, (c) side view.
At back side is a modified trapezoidal shape of ground plane. Planar use to compose of a semicircular
monopole, fed by a 50 Ω microstrip line printed on an FR4 substrate. This ground plane and parasitic element
are designed to make the surface currents of radiating elements to move toward the desired direction. The
ground plane also is deformed to improve the directivity and the gain of the antenna. The right side of the
ground is cut to remove the radiation in the undesired direction. The cut segment is in trapezoid shape and a
semicircular break.
The technique that use is broken circle shaped and the deformed design of the ground plane to improve the
reflection coefficient, bandwidth and gain of this compact antenna. The requirement reflection coefficient
bandwidth of the antenna must more than 0.5 GHz at 8.5 GHz and gain of the antenna is reached over 1.3 dB of
gain at the desired frequencies. Fig. 2 and Table 1 shows the proposed antenna specifications and antenna
H. Nornikman et al, 2014
Australian Journal of Basic and Applied Sciences, 8(4) Special 2014, Pages: 294-300
Fig. 2: The dimension of monopole antenna with modified trapezoidal shaped ground plane.
Table 1: Dimension ofMonopole Antenna with Modified Trapezoidal Shaped Ground Plane.
Actual dimension from calculattion
Impedance matching width, w
Length of ground plane, A
Width of ground plane, B
Radius circle, R
Circle break dimension, a and b
a = 13.4
Height of trapezium, h1 and h3
Length of trapezium, L
Height of break, h2
Optimization dimension (mm)
a = 15.4
b = 1.5
This section focused on the resonant frequency, return loss, radiation pattern and also the gain performance
of the monopole antenna with the modified trapezoidal shaped ground plane. Fig. 3 shows the return loss of the
monopole antenna with the modified trapezoidal ground plane. The bandwidth of this antenna is 562 MHz
between 8.047 GHz and 8.628 GHz.Even though the actual maximum resonant frequency is 8.335 GHz with
return loss - 12.253 dB, but for radar application, the desired resonant frequency is at 8.5 GHz with return loss 11.230 dB. Besides that, the results from the radiation pattern (simulation) is shown in Fig. 4. The pattern shows
that it has the directional antenna design.
Fig. 5 shows the fabricated directional monopole antenna with the trapezoidal ground plane. This fabricated
antenna is using the same material and the same substrate like his simulation design. This antenna is used FR-4
substrate because of lightweight and low cost. Fig. 6 shows the return loss of the directional monopole antenna
with trapezoidal ground plane (measured by network analyzer).
Table 2 represents the comparison result between simulation and measurement of the antenna.The gain of
the fabricated antenna is 1.860 dB while the simulation result is 2.324 dB.During calibration with spectrum
analyzer, the results obtained are better than simulation. Return loss that obtained is - 14.376 dB at a frequency
of 8.5 GHz. The bandwidth for measuring antenna is 1.86 dB. Fig. 7 shows the measured radiation pattern for
monopole antenna with modified trapezoidal ground plane.
H. Nornikman et al, 2014
Australian Journal of Basic and Applied Sciences, 8(4) Special 2014, Pages: 294-300
Fig. 3: Return loss of the monopole antenna with modified trapezoidal ground plane.
Fig. 4: Radiation pattern of the monopole antenna with modified trapezoidal ground plane (simulation).
Fig. 5: Fabricated monopole antenna with modified trapezoidal ground plane, (a) front view and (b) ground
plane view.
H. Nornikman et al, 2014
Australian Journal of Basic and Applied Sciences, 8(4) Special 2014, Pages: 294-300
Fig. 6: Return loss of the directional monopole antenna with trapezoidal ground plane (measured by network
Table 2: Comparison Result Between Simulation and Measurement.
Resonant frequency
Return loss
Fig. 7: The radiation pattern of the monopole antenna with modified trapezoidal ground plane (measured).
This simulated and the fabricated antenna can increase its parameters performance by applyingother
techniques such as stacked patch, coplanar waveguide-fed or integrate split ring resonator (SRR) structure of the
patch antenna. This proposed microstrip antenna capabilityto integrate with other devices such as an oscillator
(Yoo, S. -S.,et. al, 2011),amplifier (Othman, A. R., et. al., 2013, Othman, A. R., et. al, 2010), RF filters
(Zakaria, Z., et. a.l, 2013, Zakaria, Z.., et. al, 2012, Zahari, M. K.., et. al, 2013), and also RF switch (Shairi, N.
A., et. al. 2013, Misran, M. H.., et. al. 2011) to generate a complete system of the RF front-end transceiver.
H. Nornikman et al, 2014
Australian Journal of Basic and Applied Sciences, 8(4) Special 2014, Pages: 294-300
The monopole antenna for radar Application was fabricated and simulated successfully. Comparison
between simulation and fabrication also been done to show the performance of the antenna. The ground plane of
the antenna is designed in order to achieve a directional radiation and high gain. Using break on the circular
patch and the top semi-circular element as a parasitic element, also deforming the ground plane, very good
reflection coefficient bandwidth is obtained. For measurements confirm that a reflection coefficient is better
than – 10.00 dB at 8.5 GHz, gain of the antenna has reached over 1.3 dB. We have achieved our objective in
design and fabricate the directional monopole antenna for radar application. We manage to get the desire gain,
bandwidth and return loss from the simulation and measurement process.
H. Nornikman would like to thank UTeM and the MyBrain15 program for sponsoring this study. The
authors would also like to thank UTeM for sponsoring this work under the PJP grant.The authors would like to
thank Universiti Teknikal Malaysia Melaka (UTeM) for their support in obtaining the information and material
in the development of our work and we also want to thank the anonymous referees whose comments led to an
improved presentation of our work.
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