Ultra-wideband Microstrip Array Antenna for 5G …Ultra-wideband Microstrip Array Antenna for 5G...
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Ultra-wideband Microstrip Array Antenna for 5G
Millimeter-wave Applications
Efri Sandi, Rusmono, Aodah Diamah, and Karisma Vinda Department of Electrical Engineering, Faculty of Engineering, Universitas Negeri Jakarta, Jakarta Timur, Indonesia
Email: [email protected]; [email protected]; [email protected]; [email protected]
Abstract—In this paper, a design of ultra-wideband microstrip
array antenna using a stepped line cut and U-slot combination
for 5G millimeter-wave applications is proposed. The feeding
technique used in the proposed design is a proximity coupling
technique to improve bandwidth performance. The proposed
antenna bandwidth performance is compared with the
conventional antenna array design to determine the bandwidth
increase. Numerical and simulation results show a significant
increase in bandwidth performance compared to conventional
design. The proposed antenna design can operate at frequency
band 28 GHz with a bandwidth 4.47 GHz and gain 8.71dB.
These results prove that the proposed antenna design can be
used for 5G technology applications in the millimeter-wave
band. Index Terms—Stepped line cut, U-slot, Ultra-wideband, 5G
Antenna, Proximity coupled fed.
I. INTRODUCTION
The development of cellular communication
technology is currently entering the 5th
generation (5G)
which has the challenge of achieving high speed, power
efficiency and system reliability [1]. One important part
of developing 5G technology is the development of
antenna designs to support 5G network performance. 5G
cellular technology requires antennas that have high
performance, Multiple Input-Multiple Output (MIMO)
and beamforming [2-3] transmission systems. 5G
technology requires a large spectrum to achieve the
desired performance. That requires the development of an
antenna that can support a wide bandwidth or ultra-
wideband antenna [4].
In developing the 5G antenna design, the size and
dimensions of The design of the 5G antenna was
developed at the millimeter-wave frequency according to
the Federal Communication Commission (FCC)
recommendations. The FCC proposes a new rule (FCC
15-138) for wireless broadband frequencies, namely as 28
GHz frequency bands, 37 GHz frequency band, 38 GHz
frequency band, and 64-71 GHz frequency band which
are targeted by researchers to be applied for 5G wireless
cellular network [5]. Due to the air and rain attenuation in
Manuscript received April 25, 2019; revised January 1, 2020.
This work was supported by PTUPT and PUPT UNJ 2019, the
Ministry of Research, Technology and Higher Education the Republic
of Indonesia Corresponding author email: [email protected]
doi:10.12720/jcm.15.2.198-204
the range of 28 GHz and 38 GHz are relatively small, so
this frequency band is considered to be used for 5G
technology [6].
In developing antennas for 5G technology applications,
microstrip antenna types are widely used because of
physical size, low profile, and easy to fabricated. But the
disadvantages of microstrip antennas are the narrow
bandwidth and the relatively small gain. For this reason,
various techniques have been studied to improve
bandwidth dan gain performance of the microstrip
antenna, such as using metamaterial structure technique,
patch-slot modification, and defected ground structure
(DGS).
In this study, the development of a slot antenna is
developed by adding a stepped line cut technique. The
slot antenna has the advantage of being able to produce
two-way radiation patterns with higher bandwidth [7].
The addition of slots on the antenna is able to produce a
coupling effect that affects the Q factor, which is
inversely proportional to the bandwidth of the antenna.
In previous study, the design of antenna arrays with
the U-slot method was able to increase a bandwidth up to
300 MHz for the frequency range 14.4 GHz to 15.4 GHz
[8], attain 20-30% impedance as well as gain bandwidths
without parasitic patches on another layer or on the same
layer [9], and can improves bandwidth 11.3% [10].
Furthermore, a combination of the stepped line cut
method and defected ground structure is capable of
producing bandwidth 4.29 GHz [11], using the stepped
cut four corners method able to increase bandwidth up to
63.61% [12], and a combination of the stepped line cut
and triangular slot method in the patch is able to produce
bandwidth up to 2.9 GHz for ultra-wideband antenna
applications [13].
The U-slot, along with the finite ground plane, is used
to achieve an excellent impedance matching to increase
the bandwidth [14]. The U-slot introduces a capacitive
component to counteract the large input inductance when
a thick substrate is used [9]. Then, by using a stepped line
cut, the size of the antenna has been reduced, and
bandwidth has also been sufficiently improved [11]. Thus,
the development of microstrip antennas for 5G
applications using a combination of U-slot and stepped
line cut is expected to provide more bandwidth
performance improvement than the results of previous
studies. Thus this ultra-wideband 5G antenna will be the
basis for the development of MIMO beamforming
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antennas in future research.
The outline of this paper is as follows. After the
introduction in section I, the design of proximity coupling
for the proposed antenna are described in section II.
Section III shows the combination method proposed for
5G antenna application, including numerical analysis,
assessment and provides numerical experiments that
validate our proposal. Section IV summarizes the main
conclusion of this work.
II. DESIGN OF PROXIMITY COUPLING
The Microstrip antenna had a patch on one side of the
substrate. It is required to feed the Microstrip antenna
through the ground plane. The various type of feeding
configurations such as microstrip line, coaxial probe,
aperture coupling & proximity coupling [13]. The
proximity coupling technique is also able to increase
bandwidth. In the literature, the broadband modified
rectangular microstrip antenna using proximity feeding
technique can improve the bandwidth performance up to
200 MHz (22%) with the center frequency of 900 MHz
[14]. The main advantage of this feed technique is that it
eliminates spurious feed radiation and provides high
bandwidth (13%) due to the overall increase in the
thickness of the microstrip patch antenna [14].(Fig. 1)
Fig. 1. Proximity coupling [13]
Feeding techniques are important in determining the
design process of the microstrip antenna. The various
type of feeding configuration consists of the microstrip
line, coaxial probe, aperture coupling & proximity
coupling [15].
TABLE I: PERCENTAGE OF BANDWIDTH ENHANCEMENT USING VARIOUS
TYPE OF FEEDING CONFIGURATIONS
No. Feeding Configurations Percentage of Bandwidth
Improvement
1. Microstrip Line 2 – 5 %
2. Coaxial Probe 2 – 5 %
3. Aperture Coupling 2 – 5 %
4. Proximity Coupling 13%
The type of microstrip feeding technique that will be
used in this study is the proximity coupling. Proximity
coupling uses two-layer substrates with the microstrip
line on the lower layer and the patch antenna on the upper
layer. The substrate parameters of the two layers can be
selected to increase the bandwidth [16].
A. Calculation the Width of Microstrip Feed Line
The width of the microstrip feed line can be discovered
after determining the equation according to the conditions,
𝑢 =𝑊𝐹
ℎ , that given by Hammerstad [16]:
𝑊𝐹
ℎ=
8𝑒𝐴
𝑒2𝐴−2 (1)
where the value 𝐴 is determined by the equation:
𝐴 =𝑍0
100[
𝜀𝑟+1
2]
0.5
+𝜀𝑟−1
𝜀𝑟+1[0.23 +
0.11
𝜀𝑟] (2)
B. Calculation the Length of Microstrip Feed Line
The length of the microstrip feed-line can be
determined by the equation:
𝐿𝐹 =1
4𝜆𝑔 (3)
where 𝜆𝑔 is determined by the equation :
𝜆𝑔 =𝜆0
√𝜀𝑒𝑓𝑓 (4)
𝜀𝑒𝑓𝑓 =εr+ 1
2+ [
εr− 1
2(
1
√1+12ℎ
𝑊𝐹
)] (5)
This method is advantageous to reduce harmonic
radiation of microstrip patch antenna implemented in a
multilayer substrate [16]. The feed line terminates in an
open-end underneath the patch. The open-end of the
microstrip line can be terminated in a stub, and the stub
parameters can be used to improve the bandwidth [17].
III. PATCH ANTENNA ARRAYS DESIGN WITH
STEPPED LINE CUT AND U-SLOT
The proposed antenna has been simulated using
Computer Simulation Technology Studio Suite 2016, and
the performance of the antenna has been analyzed in
terms of bandwidth, return loss, VSWR, gain, and
resonant frequency.
The first step of this study is designing a conventional
microstrip antenna. The antenna consists of two
substrates, where the patch antenna on the upper layer
and the microstrip line on the lower layer. The patch and
the ground using a copper layer with a height of 0.035
mm. The height (h) of Rogers RT 5880 substrate is 0.787
mm.
And then, the antenna is designed to be conventional
microstrip antenna arrays using this equation [18]. (Fig.
2):
𝑑 =1
2 𝜆𝑔 (6)
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Ls
Ls
Fig. 2. Optimal distance on two patches [18]
Array techniques can be used to improve the quality of
the gain and directivity of the microstrip antenna. The
function of patches distance is to avoid mutual coupling
or the emergence of voltage in antenna due to adjacent
antenna currents [19], [20].
The geometry of a conventional microstrip antenna
arrays designed has been shown in Fig. 3(a) and 3(b). The
dimensions of the antenna are as follow: periodic length
𝐿𝑠 = 20.24 mm, periodic width 𝑊𝑠 = 22.61 mm of the
substrate with length 𝐿𝑝 = 2.9 mm, and width 𝑊𝑠 = 4.3
mm of the patch. The antenna design, as shown in Fig. 3,
is operational at 28.46 GHz. The antenna has a bandwidth
of 3.39 GHz and gains 7.84 dB.
Ws (a)
Ws
(b)
Fig. 3. Conventional microstrip antenna arrays (a) upper layer (b) lower
layer.
Then, the conventional microstrip antenna arrays are
modified with Stepped Line Cut and U-slot.
A. Calculation of U-Slot Method
This slot patch method is done by cutting a part of the
antenna patch with U-shaped. The dimensions of U-Slot
methods have been shown in Fig. 4.
Fig. 4. Dimensions of U-slot method
Slots E and F thickness are define as [21]:
𝐸 = 𝐹 = 𝜆0 / 60 (7)
Slot D length is defined as :
𝐷 = 𝐶
𝑓𝑙𝑜𝑤 √𝜀𝑒𝑓𝑓− 2 (𝐿 + Δ𝐿 − 𝐸) (8)
Slot C is defined as :
C ≥ 0,3 𝑥 𝑊𝑝 (9)
B. Calculation of Stepped Line Cut Method
In the stepped line cut method, several corners of the
rectangular patch are cut to produce the desired
bandwidth. In this method, the angle of the patch can be
cut in the form of steps based on geometry calculations
[22], [23]. The geometry details of the stepped line cut
methods have been shown in Fig. 5.
Fig. 5. Geometry details of stepped line cut methods [23]
𝑊1 = 𝑊𝐿 − 𝑊𝐻
2= ∑ 𝑊𝑅𝑛
𝑛=𝑛
𝑛=1
(10)
𝐿1 = 𝐿𝐿 − 𝐿𝐻
2= ∑ 𝐿𝑅𝑛 (11)
𝑛=𝑛
𝑛=1
Wp
Lp
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𝐿𝑠
𝑑𝐵
𝑑𝐵
When the steps dimension is the same, then WR = WR1
= WR2 = … = WRn and LR = LR1 = LR2 = … = LRn, and it
can be determined by the equation:
𝑊𝑅 =𝑊1
𝑛 (12)
𝐿𝑅 =𝐿1
𝑛 (13)
𝑅1 = 𝑛 𝑥√𝐿𝑅2 + 𝑊𝑅
2 (14)
where,
n = amount of steps
R1 = slop of steps
WR = width of steps
LR = length of steps
Based on the formulas, the microstrip antenna arrays
design with combination stepped line cut, and U-slot has
been shown in Fig. 6.
𝑊𝑠
Fig. 6. Antenna arrays with a stepped line cut and U-slot
The dimensions of the antenna are as follow periodic
length 𝐿𝑠 = 19.86 mm, periodic width 𝑊𝑠 = 23.41 mm of
the substrate with length 𝐿𝑝 = 2.9 mm, and width 𝑊𝑝 =
5.1 mm of the patch. The antenna is operational at 28
GHz band and has better bandwidth and gain
performances.
Fig. 7. Detail dimension of stepped line cut and U-slot
TABLE II: THE DIMENSION OF THE STEPPED LINE CUT AND U-SLOT
Stepped Line Cut
(mm) U-Slot (mm)
WR LR C D E F
0.3 0.3 1.4117 1 0.1783 0.3
A comparison of antenna bandwidth performances has
been shown in Fig. 8. The conventional antenna arrays
have bandwidth 3.39 GHz. For some applications, the
value of the conventional antenna arrays bandwidth was
large enough, but for 5G mm-wave application still need
to improved. In this observation, the modified antenna
with stepped line cut and U-slot is effective in enhancing
the bandwidth up to 4.47 GHz.
Frequency (GHz)
(a)
Frequency (GHz)
(b)
Fig. 8. Bandwidth Enhancement (a) Conventional microstrip antenna arrays, (b) Microstrip antenna arrays with Stepped Line Cut and U-Slot.
TABLE III: SIMULATION ANTENNA PERFORMANCE COMPARISON
Performance
Parameters
Antenna Array
Conventional Design Stepped Line Cut
and U-slot
Bandwidth (GHz) 3.39 4.47
Return Loss (dB) -15.05 -20.52
Gain (dB) 7.84 8.71
As shown in Table III, modifying antenna with stepped
line cut and U-slot doesn’t only enhance the bandwidth,
but also gain. The modified antenna has a better value of
return loss compare to the conventional antenna design.
(a)
𝐿𝑝
𝑊𝑝
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(b)
Fig. 9. Radiation Pattern (a) Conventional microstrip antenna arrays, (b) Microstrip antenna arrays with a stepped line cut and U-slot.
Then, the microstrip antenna design with stepped line
cut and U-slot is fabricated for further measurement and
validate our proposal as shown in Fig. 10.
(a)
(b)
(c)
(d)
Fig. 10. Fabrication result of microstrip antenna arrays with stepped line
cut and U-slot (a) proposed antenna, (b) upper antenna layer, (c) feeding
antenna layer, (d) ground antenna.
The comparison of simulation and measurement results
of the proposed design method, as shown in Fig. 11.
dB
Simulation ….. Measurement
(a) dB
Theta/ Degree
Simulation ….. Measurement (b)
Fig. 11. Comparison of simulation and measurement microstrip antenna
arrays with a stepped line cut and U-slot (a) S-parameter (b) 2D
Radiation pattern plot.
The comparison of simulation and measurement results
shows that there is no significant difference, so it can be
concluded that the proposed design method can be used
as a solution to increase the microstrip antenna bandwidth
for ultra-wideband 5G millimeter-wave frequency. Thus
the results of this study can be used as basis for future
studies to develop 5G antenna beamforming with high
bandwidth performance.
IV. CONCLUSIONS
The combination of U-slot techniques and a stepped
line cut method proved to be able to increase bandwidth
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and gain performance of the microstrip antenna for 5G
millimeter-wave application. The proposed design
method was improved the antenna bandwidth up to 4.47
GHz or increase 31.8% compared to conventional design
methods. The simulation and measurement result of the
proposed design can be used as the basis for further
development to enhance the performance of 5G
millimeter-wave antennas and other applications.
CONFLICT OF INTEREST
The authors declare no conflict of interest.
AUTHOR CONTRIBUTIONS
E.S, A.D, and K.V conducted the research; E.S, R, and
A.D analyzed the data; E.S and A.D wrote the paper. All
authors had approved the final version.
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Copyright © 2020 by the authors. This is an open access article
distributed under the Creative Commons Attribution License (CC BY-NC-ND 4.0), which permits use, distribution and reproduction in any
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Efri Sandi was born in Rumbai, Riau
Province, Indonesia, in 1975. He
received the B.S. degree from
Universitas Negeri Padang (UNP),
Indonesia, in 1999, the M.S. degree from
Universitas Trisakti, Indonesia, in 2004,
and his Ph.D degree from Universitas
Indonesia, in 2017, all in electrical
engineering. He joined to the Department of Electrical
Journal of Communications Vol. 15, No. 2, February 2020
©2020 Journal of Communications 203
Engineering Universitas Negeri Jakarta since 2008 as a lecture.
Since 2019 he has been appointed as head of electronic
engineering education program in engineering faculty
Universitas Negeri Jakarta. He also worked as a
telecommunications consultant for several telecommunications
companies in Indonesia since 2005. His research interests
include antenna and propagation, mobile communication and
radar application.
Email: [email protected]
Rusmono was born in Jakarta, DKI
Jakarta Province, Indonesia, in 1959. He
received the B.S. degree from electronic
engineering education IKIP Jakarta,
Indonesia, in 1984, and the B.S degree
from electrical engineering Universitas
Indonesia, in 2000, the M.S. degree and
Ph.D degree from IKIP Jakarta, in 1995
and 2009, all in educational technology.
He joined to the Department of Electrical Engineering
Universitas Negeri Jakarta since 1985 as a lecture. Since 2016
he has been appointed as secretary of the research institute
Universitas Negeri Jakarta. He also worked as an instructional
design consultant for several university and companies in
Indonesia since 1995. His research interests include
instructional design in electrical engineering, curriculum design
in electrical engineering and communication system.
Email: [email protected]
Aodah Diamah was born in Jakarta,
Indonesia, in 1978. She received the B.S.
degree from Universitas Indonesia (UI),
Indonesia, in 2001 and the M.S. degree
from Monash University, Australia, in
2004. She received her Ph.D degree from
University of Canberra, Australia, in
2017, all in electrical engineering. She
joined to the Department of Electrical Engineering Universitas
Negeri Jakarta since 2005 as a lecture. Since 2019 she has been
appointed as Quality Assurance (GP3M) of graduate program
Universitas Negeri Jakarta. Her research interests include
computer programing, algorithm analysis and antenna
propagation.
Email : [email protected]
Karisma Vinda was born in Jakarta,
Indonesia, in 1997. She received the B.S.
degree from Universitas Negeri Jakarta
(UNJ), Indonesia, in 2019 with majoring
electrical engineering. She joined to the
antenna and microwave research group
in Department of Electrical Engineering
Universitas Negeri Jakarta since 2016 as
a research assistant. Currently, she continuing M.S degree in
electrical engineering with majoring telecommunication system.
Her research interests include antenna and propagation,
communication system and radar application.
Email: [email protected]
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©2020 Journal of Communications 204