Wireless Pers Commun
DOI 10.1007/s11277-014-1798-8
A New Compact Microstrip Integrated E-Array Patch
Antenna with High Gain and High Aperture Efficiency
R. Pavithra · D. Mohanageetha · E. A. Mary Anita ·
M. Subramaniam
© Springer Science+Business Media New York 2014
Abstract This paper describes a new compact single-feed, single-layer microstrip E-shaped
patch antenna. It is an integrated array antenna and it is designed for a frequency range around
2.45 GHz ISM band. It is a symmetrical antenna suitably designed for WLAN application.
This prototype was fabricated on a FR4 substrate with a relative permittivity of 4.7 and about
0.8 mm thickness. The aperture efficiency and gain of about 72 % and 6.7 dBi was obtained.
It can be achieved by numerical algorithms for electromagnetic solutions like finite element
method (FEM) and the method of moments (MOM) by using electromagnetic simulation
software. For validation purpose CAD FEKO 6.1 suite is used. The bandwidth and gain
achieved in the array antenna is 15 % greater than the single patch antenna.
Keywords Microstrip antenna · Circular polarization · Gain · Directivity
1 Motivation
The continuous technological development of WLAN technology (Wireless Local Area Net-
work) leads to several constraints in terms of size, bandwidth, gain, polarization and many
other antenna performance parameters. Since WLAN antennas are deployed in a wide range
of topological situations, a major design constraint is the space occupied by the antenna.
Single elements can also be used in Wireless application [1], which will occupy only less
space. But due to the requirement of higher directivity, and possibly even some degree of
flexibility, an array antenna is chosen [2]. A possible solution is to design the antenna as an
array switching between several sub arrays. In order to meet the challenges and requirements
presented by these sophisticated wireless systems, there is a need to develop a dedicated
antenna design and these antennas are in urgent demand for these type of applications [2,3].
Utilization of optimization schemes to solve electromagnetic problems [1,2] specifically
antenna designs, has been reported with very encouraging results. The basic idea of this
R. Pavithra (B) · D. Mohanageetha · E. A. Mary Anita · M. Subramaniam
Sri Krishna College of Technology, Coimbatore, Tamilnadu, India
e-mail: pavithra7579@gmail.com
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approach is to specify the design requirements for the problem and to solve the critical
problems [4] which will meet the goals and requirements.
2 Introduction
Microstrip patch antennas are widely used in many applications [5] because of its low profile
structure, light weight and conformity. A microstrip patch excited by microstrip transmission
line feed [6] is used, so that the microstrip line is connected directly to the edge of the
microstrip patch. The edge impedance should be matched with the impedance of the feed
line for maximum power transfer [5]. A method of impedance matching between the feed line
and radiating patch is achieved by introducing a single or multi-section quarter-wavelength
transformers [7]. This feed arrangement has the advantage that the feed can be etched on the
same substrate to provide a planar structure [5], so that they can be easily fabricated. The
conductingstrip is chosen to be much smaller in width than the patch size which leads to
decreasing in undesired radiation.
The two main issues such as bandwidth and space occupied can be readily solved by
optimization. For good antenna operation a higher bandwidth is desirable which is actually
only a fraction i.e. only a few percent. As in present age of communication the data to be
sent is increasing and hence there is an increase in demand for Bandwidth [2]. So increasing
the bandwidth of antennas become important technically as well as commercially. Stacking
and coupled patches can also be used for bandwidth improvement but they increase the
complexity. The better way is to choose E-shaped or slotted patch [1].
In this paper, a conventional method of using parasitic patches is described in order to
increase the bandwidth and gain [4]. These parasitic patches are located on the same side
as that of the main patch. Aperture Coupled microstrip antenna can also be used, with the
parasitic patches which is stacked on the top of the main patch [8]. But this method typically
enlarges the size of the antenna in terms of antenna height or in terms of antenna plane
(geometry). A novel wideband three patch microstrip array is proposed in this paper. The
two parallel slots of each antenna are incorporated into the patches of the antenna so that the
considerable increase in bandwidth is obtained [9].
3 Integrated Antenna Array
3.1 Antenna Design
A compact integrated E-shaped patch array is designed and its performance is estimated. It
achieves around 72 % aperture efficiency [10]. The idea is to make E-shaped patch element
as a radiator and a kind of splitter, ending up with a two-dimensional array [11] in a series
fed topology. In this technique, identical E-shaped patches are mirrored to form an array like
structure in order to achieve the wider bandwidth. The bandwidth obtained for a 10 dB return
loss is 30 % more than the conventional single patch antenna [1]. It is shown that even the
initial structure of the array achieves a much wider bandwidth. This structure also achieves
a gain of 6.7 dBi. Element A is a feed-split element. It contains the primary feed, takes care
of some of the radiation, and further distributes the rest of the power to the other elements.
Elements B and C are identical and they are only radiating patches. These three patches are
connected in series by 4 mm wide microstrip lines. The entire structure is symmetrical with
respect to the horizontal axis. The elements B and C are mirrored with respect to A in order to
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A New Compact Microstrip Integrated E-Array Patch Antenna
minimize the length of the transmission lines connecting them with element A, while keeping
the correct phase. The main excitation is a 50 coaxial feed connected to patch A.
A single-layered structure with FR4 substrate is so far not able to deliver the required
bandwidth. In this method, the rectangular patches are connected to the center feeding element
by a bending microstrip line [10]. This leads to impedance mismatching and unwanted
radiation at the bending. Hence, the bending microstrip line is completely avoided and straight
microstrip lines are used in this work. The minimal height of the first array was chosen
as 8 mm which is determined by the MoM optimization framework in order to achieve a
15 % bandwidth. The medium between substrate and ground plane is air. To maximize the
available area for element B and C, these straight microstrip lines are located at the edges of
the feeding/split element A. The array was thus prototyped on a 180 mm × 210 mm ground
plane.
3.2 Simulation and Measurement
The single element antenna is designed [1] and the performance were analysed. It is mea-
sured that the directivity is 7 dBi and gain obtained is 3.8 dBi. The bandwidth obtained was
210 MHz. In WLAN, the requirement of the gain and directivity is still more. Therefore, the
microstrip integrated array is proposed. The simulated prototype configuration of the inte-
grated array patch is shown in Fig. 1. The relative bandwidth calculated with Feko Solver is
15.0 % respectively. The radiation patterns in E-plane (co-polar) and H-plane (cross-polar) at
2.45 GHz are calculated. The radiation patterns show excellent agreement for the co polarized
and cross polarized fields in phase components are shown in the Fig. 2. Due to the asym-
metric nature of the antenna, higher cross polarization has been observed. The graphs are
normalized with respect to the maximum value of the co-polar component. The cross-polar
component is more than −20 dB lower than the co-polar component in the main beam direc-
tion for both E-plane and H-plane. The main beam in the E-plane has a shift to the right of
about 5◦ . Using Optfeko Solver 6.1 the broadside gain and directivity measured at 2.45 GHz
are 6.7 and 12 dBi, respectively. Table 1 shows the parameter optimization range and optimal
parameter value.
The patch and the ground plane of this configuration were assumed to be a perfect electric
conductor (PEC) with a thickness of about 35 µm. The substrate and the ground plane were
quite large during the optimization process in order to reduce the total number of unknowns
Fig. 1 Configuration of the new
E-shaped integrated array
antenna
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Fig. 2 The simulated results for Far field radiation pattern in E-plane and H plane of the new E-shaped
integrated array antenna
for the MoM solver. The maximal aperture efficiency achieved by measurement is 72 %
respectively. The aperture efficiency of this type of array can be improved in several ways.
In cases where a lower bandwidth is tolerable, the primary technique is to decrease the
thickness of the air layer. It was found that the air layer thickness can be reduced to a
value of 1.6 mm with an increasing bandwidth of 10 % so that the aperture efficiency can be
improved.
Miniature antennas with wideband performance are in high demand for modern wireless
communications. Portable devices, such as mobile phones or notebook computers, com-
municate through different wireless techniques including the cellular network, Wi-Fi links,
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A New Compact Microstrip Integrated E-Array Patch Antenna
Table 1 Summary of the
Parameter Parameter optimization Optimal parameter
optimization dimensions of the
name range (mm) value (mm)
integrated array antenna (all
length dimensions in millimeters)
F (5, 25) 5
B (20, 32) 32
L1 (4, 30) 28
L2 (30, 60) 50
L3 (6, 12) 8
L4 (8, 20) 18
L5 (10, 24) 24
L6 (6, 12) 16
L7 (10, 44) 24
L8 (20, 70) 54
L (90, 210) 188
W (110, 224) 136
Table 2 The results of the
Thickness (mm) Radiated power (dBw) Return loss (dB)
optimized substrate thickness of
height h = 1.4 mm, h =
1.4 −43.09 −0.284
1.6 mm and h = 1.8 mm
1.6 −11.09 −25.24
1.8 −45.21 −10.35
Fig. 3 The simulated results for Gain at = 0◦ and = −5◦ of the new E-shaped integrated array antenna
GPS, Zigbee, and UWB. These multifunctional gadgets require small wideband antennas to
accommodate all the channels. Moreover, diversity or MIMO techniques are employed for
enhancing the quality of reception.
The optimization is done in terms of the height of the substrate. The array is simulated
for three different substrate thickness, (d = 1.4, 1.6 and 1.8 mm) and a comparative study is
made. From the results, it is seen that the thickness of 1.6 mm gives better performance in
terms of Radiated Power and Return Loss, is shown in Table 2.
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Fig. 4 The simulated results for power and reflection coefficient of the new E-shaped integrated array antenna
The measured gain at = 0◦ and = −5◦ is plotted in Fig. 3. The Fig. 3 shows the
measured gain of 6.72 dBi and more reduced side lobe. Since it is a directional antenna, the
power delivered is not equal in all the directions, so that the gain may vary. It is seen that,
for a variation in the angle of 5◦ , the gain is reduced to 6.38 dBi.
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A New Compact Microstrip Integrated E-Array Patch Antenna
Fig. 5 The simulated results for VSWR and efficiency of the new E-shaped integrated array antenna
The shape of the co-polar level of the antenna is not sensitive to the thickness of the
substrate, but the H-plane cross-polar level increased when the thickness is increased. The
simulated result of the return loss responses for the h = 1.6 mm thickness is shown in
Fig. 4. The value of S11 > −10 dB for better matching. Figure 4 shows that the value
of S11 = −27.6 dB and this return losses could be due to the tolerance in the design of
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this antenna prototype. For brevity, the return-loss responses for other thicknesses are not
included. Because for a thickness of h = 1.6 mm gives a better result when compared to all
other thickness. The single element antenna [1] was also designed with a substrate thickness
of t = 1.57 mm, which is around t = 1.6 mm.
Thus, the integrated array antenna design achieves more gain and bandwidth and gives
less radiated power in the order of 0.9 mw as required for wireless application as shown in
Fig. 4. The bandwidth parameter is activated once both AR and reflection magnitude satisfy
the fitness function. The weight of the bandwidth parameter is chosen such that the bandwidth
is given a higher priority than the other parameters when the AR and reflection magnitude
satisfy the given specified criteria of design.
A −10 dB S11 bandwidth of around 340 MHz is obtained through measurements. Only
some slight differences in the results are attributed to alignment issues for the multilayer
design. Figure 5 is showing the S-parameter response at bore sight, which is determined
from the return loss. The VSWR value is around 1.012 dB at 2.6 GHz is shown in Fig. 5. The
maximum aperture efficiency of about 72 % is obtained was shown in the Fig. 5.
Microstrip patch antennas have been widely researched in recent times due to their attrac-
tive features including easiness in integration [12] with other circuit elements. These antennas
are one of the most innovative topics in antenna theory and design [6] and are increasingly
finding application in a wide range of modern communication systems. For current mobile
communication, the diversity scheme has already been implemented to mitigate the fad-
ing effects of multipath scenario. In a multipath rich wireless medium, multiple antennas
are deployed at both the transmitter and receiver side achieves high data rate [7] without
increasing the total transmission power.
4 Conclusion
Due to the increase in the demand in the wireless technology, a novel microstrip integrated
array antenna is proposed. An analysis based on the concept of array antenna was discussed.
This antenna is designed to work in ISM band with the centre frequency of 2.4 GHz. From the
results, the proposed antenna will perform in a betterway in terms of gain and HPBW. The
measured Gain is, 6.7 dBi, which is very much essential for the effective loss less transmission
and the HPBW is about 73◦ , in which directivity is more than the single patch antenna. It also
provides a good bandwidth improvement in the order of 340 MHz, which is 15 % greater than
the single element E-shape antenna [1]. Further optimization need to be done for the E-shape
array patch antennas. The simulation shows that when the transversal distance between the
top microstrip layer and the edge of the finite ground plane is about three times the array
thickness, a good trade off between gain and bandwidth is obtained. A new E-shape array
antenna was designed with high gain and aperture efficiency in the order of 6.7 dBi and 72 %,
respectively was achieved for the entire ISM band.
5 Future Work
Wireless telecommunications is a promptly evolving industry, and the abrupt changes to the
antenna system are often necessary to accommodate the system needs and PSO in particular
has a widespread recognition for these strengths. Further, the multiband handset antenna
can be able to achieve the hybrid PSO–MoM program through an antenna array design
that efficiently utilized a small space and gives excellent multi-band performance. Hence, the
overall optimization plays a supreme role in the present and future designs of antennas to meet
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A New Compact Microstrip Integrated E-Array Patch Antenna
the ever demanding needs of wireless communication systems. Further several optimization
techniques can also be used for the design, and an analysis based on the concept of array
antenna can be simulated. The simulations show that when the transversal distance between
the top microstrip layer and the edge of the finite ground plane is about 3 times the array
thickness, a good tradeoff between gain and bandwidth has been obtained.
References
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R. Pavithra obtained her B.E. degree from Anna University in 2010,
M.E. Degree in Communication systems from Anna University, Chen-
nai in 2013. She has got 1 year of teaching experiance. At present,
she is working as Assistant Professor in Department of Electronics
and Communication, Sri Krishna college of Technology, Coimbatore,
Tamilnadu, India. She has published more than five research papers in
International and national jouranals and conferences. Her areas of inter-
est are Antenna Designing, Wireless Networks and Image processing.
She is a life member of ISTE and a member of IEEE.
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D. Mohanageetha obtained her B.E. degree from Bharathiar Univer-
sity in 1996, M.E. Degree in Communication systems from Madurai
Kamaraj University, Madurai in 2000 and Ph.D. from Anna Univer-
sity, Chennai in 2011. She has got 17 years of teaching experiance.
At present, she is working as Professor in Department of Electronics
and Communication, S.A. Engineering College, Chennai, Tamil nadu,
India. She has published more than 20 research papers in International
and national journals and conferences. Her areas of interest are optical
networks, MEMS, EMI/EMC and image processing. She is a life mem-
ber of ISTE and member of IEEE.
E. A. Mary Anita holds a B.E. in Electrical and Electronics Engineer-
ing and M.E. in Computer Science and Engineering, both from Govern-
ment College of Engineering, Tirunelveli, India and a Ph.D. in Infor-
mation and Communication from Anna University, Chennai. Her main
research interests are in the field of wireless networks, security and pri-
vacy. She has published several papers in international conferences and
journals and has been reviewer of several international journals.
M. Subramaniam was born in Mettur Dam, India, in 1974. He
received his B.E. degree in Computer Science and Engineering from
University of Madras, India, in 1998, M.E. degree in Software Engi-
neering and Ph.D. degree in Computer Science and Engineering from
CEG, Anna University, India, in 2003 and 2013, respectively. He
started his career as Lecturer in the Department of Computer Science
and Engineering (DCSE) at Thangavelu Engineering College, Chennai,
in June 1998. Then he worked as a Lecturer in the DCSE at SSN Col-
lege of Engineering College, Chennai, from July 1999 to April 2004.
He worked as Assistant Professor in the DCSE at MNM Jain Engineer-
ing College (April 2004–March 2008), and as Associate Professor and
HoD/DCSE at Tagore Engineering College, Chennai, from March 2008
to June 2011. Then he worked as a Professor in the the DCSE Karpaga
Vinayaga College of Engineering and Technology, from June 2011 to
February 2014. He is presently working as a Professor in the Depart-
ment of Information Technology, S.A. Engineering College, Chennai-
77 (INDIA). His research focus is Computer and Wireless Sensor Networks, Computer Vision, Digital Image
Processing and Artificial Intelligence. He is an active life member of the Computer Society of India (CSI)
and the Indian Society for technical Education (ISTE), IAENG and CSI. He is also a peer reviewer for IEEE
and has reviewed a few technical articles for the TNSM. He also reviews papers for International Journal of
Communication Systems.
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