Ultra-wideband Microstrip Array Antenna for 5G …Ultra-wideband Microstrip Array Antenna for 5G...

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

Journal of Communications Vol. 15, No. 2, February 2020

©2020 Journal of Communications 198

mailto:[email protected]

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)



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



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



(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



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

medium, provided that the article is properly cited, the use is non-

commercial and no modifications or adaptations are made.

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



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.


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.




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