A design of radial line slot array antennas using the specification of panel antennas

TELKOMNIKA, Vol.17, No.6, December 2019, pp.3066~3072
ISSN: 1693-6930, accredited First Grade by Kemenristekdikti, Decree No: 21/E/KPT/2018
DOI: 10.12928/TELKOMNIKA.v17i6.12679 ◼ 3066
Received March 19, 2019; Revised July 2, 2019; Accepted July 18, 2019
A design of radial line slot array antennas using
the specification of panel antennas
Teddy Purnamirza*1
, Muhammad Ralibi2
, Imran M. Bin Ibrahim3
, Rika Susanti4
,
Halim Mudia5
, Depriwana Rahmi6
, Sutoyo7
, Mulyono8
1,2,4,6,7,8
Department of Electrical Engineering, Faculty of Science and Technology,
UIN Sultan Syarif Kasim Riau, Indonesia
3
Faculty of Electronic and Computer Engineering, Universiti Teknikal Malaysia Malaka, Malaysia
5
Department of Mathematic Education, Faculty of Teaching and Education,
UIN Sultan Syarif Kasim, Riau, Indonesia
*Corresponding author, email: tptambusai@uin-suska.ac.id
Abstract
RLSA antennas were suggested by several researches as Wi-Fi antennas in addition to panel
antennas. Therefore, this paper researched the possibility of this suggestion. We used the size of an
available in market 16 dBi panel antenna (225 mm2
) as the size for our developed RLSA antenna. Based
on this size, we developed 60 RLSA models using extreme beamsquint technique and simulated them.
We then chose a best model with a best performance. The best model was then fabricated and measured.
The simulation and measurement results show that the developed RLSA antenna has better performance
compared to the 16 dBi panel antenna in term of gain (0.25 dB higher) and bandwidth (570 MHz wider).
The RLSA antenna also tested as antenna for a Wi-Fi device and it showed good performance.
Keywords: extreme beamsquint technique, panel antennas, RLSA antennas
Copyright © 2019 Universitas Ahmad Dahlan. All rights reserved.
1. Introduction
RLSA antennas basically were developed for satellite communications [1-4]. Thereafter,
RLSA antennas were developed for other applications such as Wi-Fi [5-10]. However, since
Wi-Fi devices use small antennas, then RLSA antennas should also developed in small form.
The small RLSA antennas have much less number of slots compared to the normal RLSA which
is developed for satellite communications. The effect of small number of slots is the capability of
slots to radiate power into space is linearly reduced, so that increasing reflected power at
the perimeter of RLSA antennas, thus lead to the increase of reflection coefficients.
Several papers tried to overcome the problem of this high reflection coefficient.
Hirokawa and Akiyama used the technique of matching slot pair aiming to waste the remaining
power at perimeter antennas [11]. Zagriatski used long slots in order to reduce the remaining
power [12]. Based on author’s observation, the technique uses in these papers are not efficient
since the power is wasted so that the power does not contribute to antenas gain. In last decade,
there is no innovations in developing techniques to overcome the problem of high reflection
coefficient in small RLSA antennas. The researches were only about the theory and the design
of RLSA antenna using conventional techniques [13-20]
Purnamirza introduced a technique to reduce the reflection coefficient by using two
material of cavity, which are polypropylene and FR4. This technique successfully reduces
the reflection coefficient without wasting remaining power [21]. Purnamirza also introduced
a technique to reduce reflection coefficient by designing RLSA antennas using high beamsquint
values. This technique also successfully minimizes the reflection coefficient [22]. Due to this
success, Purnamirza recommended their technique to be implemented in designing small RLSA
antennas [23-25].
Based on this recommendation, we tried to design a small RLSA antenna for Wi-Fi
devices at frequency of 5.8 GHz. In order to show the competitively of the RLSA antenna, we
design the RLSA antennas with a same size with an antenna usually used as Wi-Fi antenna and
widely available in market, which is a 16 dBi panel antenna. In order to test the RLSA antenna
in real condition, we developed a test bed system by setting the RLSA antenna as an antenna

TELKOMNIKA ISSN: 1693-6930 ◼
A design of radial line slot array antennas ... (Teddy Purnamirza)
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for a Wi-Fi device. We observed and compared the performance of RLSA antenna and the 16
dBi panel antenna in order to show whether the RLSA antenna can compete the panel antenna,
and become one option antenna for Wi-Fi devices.
2. Research Steps
a. Determine the RLSA antenna specifications: We determined the antenna specification by
choosing one commonly Wi-Fi antenna out of several antennas available in market. In this
research we chose the specification of 16 dBi panel antenna, which is listed in Table 1.
b. Determine the antenna material: In this research, as shown by Figure 1 (a), we chose a
material of copper as the radiating element and background of the antenna. We also chose
polypropylenes as the dielectric material for the antenna. The material of copper and
polypropylenes were chosen based on the successfully of their using in previous researches
[21-26]. The values of all the material of antenna are listed in Table 2.
c. Determine the antenna size: The size of 16 dBi panel antenna is 190 mm x 190 mm = 36100
mm2. Using this size of 36100 mm2, the diameter of RLSA antenna can be calculated using
simple circle equation, which is (36100/phi) = 107 mm, as shown by Figure 1 (b).
Table 2. Design Parameters of RLSA Antenna [21-26]
Specifications Parameters Symbols Values
Cavity Thickness d1 8 mm
The thickness of radiating
element and background
d 0.001 mm
The permittivity of cavity r1 2.33
Beamsquint angle Φ from 600
to 890
Wavelength g 33.88 mm
Slot Length L 0.5 g
Slot width w 1 mm
Radius of antenna R 107 mm
Number of slot pair in first ring n from 10 to 14
Frequency centre f 5.8 GHz
d. Design the antenna: Using the radius of 107 mm, we designed the antenna as shown
by Figure 1.
e. Design the antenna feeder: We modified an ordinary SMA feeder by adding a header
(as shown by Figure 2 (a)). This header functions to convert the TEM coaxial mode into TEM
cavity mode, so that signals will spread radially within the cavity material, as shown
by Figure 2 (b). The definition of feeder structure parameters is shown by Figure 2 (a).
The material and the values of all feeder structure parameters are listed in Tables 3 and 4,
respectively.
Table 1. Antenna Specifications
Specifications Values
Gain 16 dBi
Bandwidth
125 MHz
(5725–5850 MHz)
Beamwidth 250
Impedance 50 Ohm
(a) (b)
Figure 1. (a) Antenna structure [23-26] and (b) design slots

◼ ISSN: 1693-6930
TELKOMNIKA Vol. 17, No. 6, December 2019: 3066-3072
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(a) (b)
Figure 2. (a) Definition of feeder structure parameters, and
(b) Signal propagation within antenna cavity [21]
Table 3. Materials of RLSA Antenna [21-26]
Specifications Parameters Material
Radiating element Copper
Background Copper
Cavity Polypropylenes
Head of Feeder Copper
Table 4. Design Parameters of Feeder [21-26]
Specifications Parameters Symbols Values
The height of disc h 3 mm
The radius of disc ra 1.4 mm
The lower air gap b1 4 mm
The upper air gap b2 1 mm
f. Drawing the antenna: Since the structure of RLSA antenna is complex with hundreds of
slots, so it is time consuming to draw this antenna manually in microwave simulation
software. Hence in order to speed the drawing process, we develop a VBA (Visual Basic
Applications) program. This program is embedded within the microwave simulation software.
This program is able to draw an RLSA antenna within seconds while it takes days with
manual drawing. Using this program we drew 150 models of RLSA antenna which vary in
values of beamsquint (Φ) and the number of slots in first ring (n).
g. Simulate the antenna. We simulated the 150 antenna models and we took the simulation
results of several performance parameters such as gain, bandwidth, S11 response,
beamwidth, efficiency and radiation pattern. A best antenna in term of performance was
chosen to be fabricated. The parameters of this antenna are n = 14 and Φ = 600. The best
model is shown by Figure 1 (b).
h. Fabricate the best antenna model and the feeder. The best antenna model and header
chosen in previous step were fabricated as shown in Figure 3.
(a) (b) (c)
Figure 3. Fabricated model (a) radiating element (b) background (c) feeder
i. Measure the fabricated prototype. We measured several performance parameters including
gain, radiation pattern, beamwidth, bandwidth and S11. The measurement was conducted
using an anechoic chamber and a network analyzer as shown by Figure 4.

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(a) (b)
Figure 4. Measurements (a) in anechoic chamber (b) by a network analyzer
j. Analysis and compare the simulation and measurement result. In order to verify the validity
of our design, we compared between the simulation result and the measurement result.
If they have good agreement, then meaning the design is the correct ones.
k. Test the prototype. We set a test bed in order to show the ability of the prototype in working
in a real communication systems.
3. Results and Analysis
Figure 5 shows the S11 response of the antenna both in simulation and measurement.
It is observed that the antenna has a bandwidth of about 720 MHz at the center of 5.8 GHz.
We can draw conclusion that the bandwidth is more than enough for Wi-Fi communications
which is only 150 MHz. The interesting result is the bandwidth is also much wider compared to
the bandwidth of the 16 dBi panel antenna which is only 125 MHz. Figure 6 shows the radiation
pattern of the antenna both in simulation and measurement. It is observed that the antenna has
beamwidth of about 280 and point to about 520 from boresight direction. We also got
the antenna gain of 16.25 dBi which is 0.25 dB higher than the panel antenna gain (16 dBi).
From Figures 5 and 6, we can observe that the simulation result matches
the measurement result, thus verifying the validity of our design. Slight differences between
the simulation and measurement result are due to the shift of cavity, radiating element and
background elements from the correct positions during the fabrication process. The differences
are also due to the inaccuracies during the installation of header at the correct position in SMA
Feeder. Based on above analysis, we summarized the specifications of RLSA antenna and
the panel antenna as shown by Table 5. From this table, we can conclude that the RLSA
antenna has better performance compared to panel antenna in term of gain and bandwidth.
Especially in term of bandwidth, the RLSA antenna has much wider bandwidth compared to
the panel antenna.
Figure 5. Reflection coefficient

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Figure 6. Radiation pattern
Table 5. The Specifications of Panel and RLSA Antenna
Specifications Panel Antenna RLSA antenna
Gain 16 dBi 16.25 dBi
Bandwidth 125 MHz (5725-5850 MHz) 720 MHz (5432 -6150 MHz)
Beamwidth 250
280
Impedance 50 Ohm 50 Ohm
We tested the RLSA antenna as the antenna for Wi-Fi Devices. We set up a test bed as
shown in Figure 7. The test bed consists of two transceivers. The first transceiver shown in
Figure 7 (a) consists of a laptop and a Wi-Fi access point connected using an Unshielded
Twisted Pair (UTP) cable. In the second transceiver shown in Figure 7 (b), we connected
the RLSA antenna to a Wi-Fi access point using a pigtail cable RG-147 SMA male to RP-SMA
male. The access point is connected to a laptop using a UTP cable. We carried out a Wi-Fi
communication (data, picture, audio and video streaming) between the two transceivers in
several conditions, those are for outdoor, indoor and different weather. The test result showed
that the communication link could be established well, thus verifying the good performance of
the RLSA antenna in actual implementation.
(a) (b)
Figure 7. Test bed systems: (a) first and (b) second transceiver

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4. Conclusions
We have designed, simulated, fabricated, and measured the RLSA antenna based
on the specification of a panel antenna that available in markets. The simulation and
measurement result shows that with same size, the RLSA antenna has better performance
compared to the panel antenna, especially in term of bandwidth. We also have tested the RLSA
antenna as an antenna for Wi-Fi devices. The test shows that the RLSA antenna performed
a good performance.
Acknowledgements
Firstly, we would like to thank to Lembaga Penelitian dan Pengabdian Masyarakat
(LPPM) Universitas Islam Negeri Sultan Syarif Kasim, Indonesia, for partially funding this
research. Secondly, Appreciation also goes to Advance Microwave Laboratory, Faculty of
Electronic and Computer Engineering, Universiti Teknikal Malaysia Malaka for their assistances
in conducting antenna measurements. Thirdly, we also thank to Computer Simulation
Technology Malaysia Sdn. Bhd, for giving a temporary license to use CST STUDIO SUITE™
Software for one month as simulation software in our research.
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