Simulation of 38 GHz 2x1 rectangular patch antenna array. Polarization : Linear Horizontal BW : 600 MHz - 1 GHz Applicable 5 G technology

1. 1
Abstract—
This paper presents a 2x1 rectangular antenna
array that is designed to operate at KA band. The
antenna is design such as its patch parameter,
spacing, power divider and feeding technique has
been optimized in order to fulfill requirements of
high gain and directivity. The array is designed to
operate at frequency of 38GHz using a RT/Duroid
5870 substrate at thickness of 0.127mm,
permittivity, ɛr of 2.2 and copper thickness of
0.035mm. A bandwidth of 1 GHz (2.7%) were
achieved for 2x1 array antenna with VSWR less
than 2:1. The antenna has also achieved 80%
total efficiency with 9.75 dBi gain. Horizontal
linear polarization is achieved. Hence, the
proposed antenna design is suitable for 38 GHz
mmWave non-mobile communication.
Keywords—Reflection coefficient, 5G, Gain,
Directivity, Millimeter Wave, Quarter Wave.
I. INTRODUCTION
Technology in communication evolved rapidly of
which it has become a challenge toward the
modern wireless communication industries. The
trend of Forth Generation (4G) Communication
has come to its peak where the utilization of its
bandwidth is almost saturated and it can’t longer
cope with the demand (capacity, data rate, etc) of
current devices. This introduce to a new
technology called Fifth Generation (5G)
Communication which offers a wider bandwidth,
higher speed, high capacity, data rate and low
latency. However, the standard for 5G has yet to
be defined as the technology is still in
development stage. Figure 1 shows some of the
candidate bands for 5G communication from
20Ghz to 90GHz [1]
Figure 1 Candidate Band for 5G
The microstrip antenna have a beneficial physical
characteristic such as it is light in weight, low cost,
mechanically robust when mount on a rigid
surface. Despite its advantages, the microstrip
antenna has several advantages such as narrow
bandwidth and low efficiency. [2]
II. METHODOLOGY
This section will discuss the theory of calculation
of each antenna parameter. The initial step of
designing a microstrip rectangular patch antenna
is by determining the patch dimension (the width
and length). This calculation will take into account
the type of substrate used, its dielectric constant,
substrate height and the centre frequency. The
design microstrip patch antenna will then match
to a matching feedline (50Ω and 100Ω) using a
quarter-wave transformer, however the exact
dimension was tuned by sweep and optimize by
CST software. Details of the calculation as follows:
A) The width (W) and length (L) of the
microstrip patch:
Where the effective dielectric constant is given by:
And
ΔL = 0.412h [(ε݁ +0.300) (W/ℎ+0.264)] /[(ε݁ -0.258)
(W/ℎ+0.800)]
Design of a 38 GHz Rectangular Patch
Microstrip Patch Antenna for 5G Applications
MOHAMAD AIZWAN BIN ABD AZIZ (2018457046)
SULAIM BIN AB QAIS (2018867974)
Faculty of Electrical Engineering
Universiti Teknologi MARA Shah Alam Malaysia

2. 2
III. ANTENNA DESIGN
In this section, the design antenna is develop
based on the calculations performed in part II.
The main parameters of the antenna are defined
in Table 1. Performance and evaluation of the
single patch and array antenna is subsequently
conducted using CST Studio Suite Simulation.
Frequency 38GHz
Substrate RT/Duroid 5870
Dielectric Constant 2.2
Substrate Height 0.127mm
Copper thickness 0.035mm
Table 1 Antenna Specification
Figure 2 Parameter for a single patch antenna
Figure 3 Parameter for a 2x1 array patch antenna
IV. RESULTS AND DISCUSSIONS
In this section, several parameters will be
discussed such as but not limited to S11, Z11 gain,
directivity, VSWR and radiation pattern at
frequency of 38GHz. This section will also discuss
and compare the parameters between a single
patch and 2x1 array patch antenna. The results
obtained using a CST Studio Suite Simulation
optimize function.
Directivity and Gain
An antenna that radiates equally in all directions
would have effectively zero directionality, and
the directivity of this type of antenna would be 1
(or 0 dB). It is a measure of how 'directional' an
antenna's radiation pattern is. Antenna directivity
refers to the peak of the directivity. In other
words, directivity is a measurement how much
the antenna focus compared to the isotropic
antenna that radiated in all directions. Antennas
for cell phones should have a low directivity
because the signal can come from any direction,
and the antenna should pick it up.
Figure 7 Directivity of 38 GHz single patch antenna

3. 3
Figure 8 Directivity of 38 GHz dual patch antenna
Antenna gain is more commonly quoted than
directivity in an antenna's specification sheet
because it takes into account the actual losses that
occur. A transmitting antenna with a gain of 3 dB
means that the power received far from the
antenna will be 3 dB higher (twice as much) than
what would be received from a lossless isotropic
antenna with the same input power. Gain will be
lower than directivity. An ideal antenna will have
the directivity and gain equal which result in 100%
efficiency.
Figure 9 Gain of 38 GHz single patch antenna
Figure 10 Gain of 38 GHz dual patch antenna
Figure 7,8,9 and 10 shows that the directivity and
the gain of single and dual patch antenna results.
The directivity and gain of the dual patch are about
3dB higher, means that the dual patch antenna
can give higher directivity and gain. From result we
can get 6.59dB gain for single patch antenna and
9.75 dB gain for dual-patch array antenna. Lower
directivity is useful for unknown signal direction
application such as mobile phone application that
can accept signal from all direction. As for high
directivity antenna, it is suitable for one direction
communication.
Efficiency
The single patch antenna design gives -0.9043 dB
(81.2%) and dual-patch patch antenna give -
0.9499 (80%) efficiency at 38 GHz. Efficiency
shows how much power radiated as a far field
signal compared to input power. Mobile phone
antennas, or WIFI antennas in consumer
electronics products, typically have efficiencies
from 20%-70% (-7 to -1.5 dB). Thus, both designed
antennas would have better efficiency than most
of consumer product at 38 GHz. Antenna
efficiency losses are typically due to:
i) conduction losses (due to finite
conductivity of the metal that forms
the antenna)
ii) dielectric losses (due to conductivity
of a dielectric material near an
antenna)
iii) impedance mismatch loss

4. 4
Antenna S11 and VSWR
S11 represents how much power is reflected from
the antenna. The remainder of the power was
"accepted by" or delivered to the antenna. This
accepted power is either radiated or absorbed as
losses within the antenna. Since antennas are
typically designed to be low loss, ideally the
majority of the power delivered to the antenna is
radiated.
VSWR represent how much the standing wave.
This measurement is directly related to S11. When
S11 is high then VSWR will be high.
Figure 11 show S11 response of 38 GHz single patch antenna
Figure 12 VSWR response of 38 GHz single patch antenna
Figure 13 S11 response of 38 GHz dual patch antenna
Figure 14 VSWR response of 38 GHz dual patch antenna
Looking into low S11 and low VSWR does not
mean that the antenna is radiated. It only
showing that less reflected power coming back by
assuming most of the power radiated. The power
loss can be due to other factor such as copper
loss or absorption. Thus, designer needs to look
into the efficiency and do the radiation test.
Bandwidth
Bandwidth can be taken from S11 plot (<10 dB)
or VSWR plot (<2:1). Bandwidth can be
represented in frequency range or in percentage
as formula below. Figure show bandwidth of
single patch antenna having 619 MHz (1.63%) and
2x1 array antenna having 1.06 GHz (2.7%).
Figure 15 Impedance of 35 GHz single patch antenna

5. 5
Figure 16 Impedance of 35 GHz dual patch antenna
Figure 15 and 16 show the simulation impedance
of both designed antennas. These antennas
functioning between 30 to 70 ohm input
impedance.
Figure 17 axial ratio of 35 GHz single patch antenna
Figure 18 axial ratio of 35 GHz dual patch antenna
Axial ratio and Polarization
Axial ratio is the parameter majorly used to
describe the polarization nature of circularly
polarized antennas. The Axial Ratio (AR) is
defined as the ratio between the minor and
major axis of the polarization ellipse. Linear
polarization has >20dB axial ratio. Polarization
mismatch or polarization diversity can be waste.
Antenna is considered as elliptical polarization if
having axial ratio between 3dB to 20 dB, and as
circular polarization if having <3 dB axial ratio.
Both simulated patch having an axial ratio of 40
dB. Thus, conclude both antennas are linearly
polarized antenna.
V. CONCLUSION
The array is designed to operate at frequency of
38GHz using a RT/Duroid 5870 substrate at
thickness of 0.127mm, permittivity, ɛr of 2.2 and
copper thickness of 0.035mm. A bandwidth of 1
GHz (2.7%) were achieved for 2x1 array antenna
with VSWR less than 2:1. The antenna has also
achieved 80% total efficiency with 9.75 dBi gain.
Horizontal linear polarization is achieved. Hence,
the proposed antenna design is suitable for 38 GHz
mmWave non-mobile communication.
VI. RECOMMENDATIONS
There are some differences between important
parameter between calculation and simulation
especially the matching line between 100 ohm
line and patch. There is some hypothesis on this
that may need to discover in future as below:
i ) Most of the calculation is approximate.
ii) Limitation of the formula that did not cover for
very high frequency such mmWave.
Rectangular patch antenna for mmWave need to
use thinner substrate with lower permittivity to
achieve the desire response.

6. 6
VII. REFERENCES
[1] Naser Al-Falahy a,b,∗, Omar Y.K. Alani a
‘Millimetre wave frequency band as a candidate
spectrum for 5G network architecture : A survey’
Article history 15 November 2018
[2] Norfishah Ab Wahab, Zulkifli Bin Maslan, Wan
Norsyafizan W. Muhamad, Norhayati Hamzah
‘Microstrip Rectangular 4x1 Patch Array Antenna
at 2.5GHz for WiMax Application’ Faculty of
Electrical EngineeringUniversiti Teknologi MARA
Malaysia, Conference Paper · July 2010
[3] Bevelacqua, P. (2019). Directivity - Antenna-
Theory.com. [online] Antenna-theory.com.
Available at: http://www.antenna-
theory.com/basics/directivity.php [Accessed 9
Dec. 2019].
[4] Bevelacqua, P. (2019). Antenna Gain. [online]
Antenna-theory.com. Available at:
http://www.antenna-theory.com/basics/gain.php
[Accessed 9 Dec. 2019].
[5] Bevelacqua, P. (2019). Directivity - Antenna-
Theory.com. [online] Antenna-theory.com.
Available at: http://www.antenna-
theory.com/basics/directivity.php [Accessed 9
Dec. 2019].
[6] Sharma, S., Tripathi, C. and Rishi, R. (2017).
Impedance Matching Techniques for Microstrip
Patch Antenna. Indian Journal of Science and
Technology, 10(28), pp.1-16.