Design of a 2*2 Microstrip Phased Array Antenna for Radar Applications
SHANTHA SELVA KUMARI. R., MRIDULA. S.
Department of Electronics and Communication Engineering,
Mepco Schlenk Enginnering College,
Sivakasi,
INDIA
Abstract: - Micro-strips patch antennae used in array configurations are more beneficial than single antenna
element by augmenting the directivity (dB) radiation pattern, and lowering the substrate's permittivity to overcome
its drawbacks, which include poor gain, low efficiency, narrow bandwidth limited directivity. It also facilitates
beam-steering capability which is obtained by enabling phase difference) between the antennas. Beam scanning
capability is used in radar and GNSS technologies. This paper proposes a 2*2 microstrip phased array antenna by
using rectangular microstrip patch antenna on an FR-4 dielectric substrate for beam scanning. The resonant
frequency of the antenna is at 2.52GHz frequency with a good Voltage Standing Wave Ratio (VSWR) value of
1.1325. The design has been simulated in Ansys HFSS software. The simulation results exhibit antenna better
performance of the proposed antenna compared to state-of-art designs present in the literature. The compactly
designed Rectangular Micro-strip Patch Antenna array shows a low S-parameter (–24.127858 dB), high gain
(13.689104 dB), directivity (14.055125 dB), and efficiency of 91.917%.
Key-words: - Phased Array Antenna, beam scanning, directivity, efficiency, gain, VSWR, S-Parameter.
Received: August 17, 2022. Revised: September 29, 2023. Accepted: November 22, 2023. Published: December 31, 2023.
1 Introduction
Nowadays, wireless communication has become an
increasingly prevalent mode of communication,
replacing traditional wired technology. The antenna
device, which makes it possible to send and receive
wireless signals, is at the heart of wireless
communication. Since its inception as a massive
metallic device, antenna design has seen numerous
evolutions, driven by the diverse spectrum of
wireless communication applications. In recent years
there has been substantial increase in the popularity
of microstrip Patch Antennae, in particular, due to
their obvious advantages over conventional designs
in terms of compact form factor, mechanical
resilience, low cost, low power consumption, and
ease of manufacture, [1]. Satellite communication
requires higher gain so a single patch antenna cannot
be used. An array antenna has to be employed to
achieve a certain gain. However, beam steering must
also be considered which scans a wide range of
angles. Nowadays, phased array microstrips are
widely employed in radar and satellite
communication since they provide higher gain, beam
scanning, etc. The array antenna is designed the
energy radiated in the major or main lobe (ML) is
high the direction can be manipulated by adjusting
the signal phase fed to the antenna, [2]. These phased
antennas are designed to provide accurate landing for
the airplanes, as they can transmit data at required
angles.
In this paper, a microstrip phased array antenna
that resonates at 2.52GHz is designed and discussed.
A single inset-fed rectangular patch antenna is
designed with various parameters observed, which is
then evaluated and designed to develop the 2*2 array
acquired to obtain a good return loss. The gain and
radiation pattern have been examined for varying
degrees at 15.84dBi.
2 Microstrip Patch Antenna
A Rectangular Micro-strip Patch Antenna has three
distinct layers, as shown in Figure 1. It consists of
conducting ground and patch layers below and above
the substrate plane. Substrate (dielectric) with less
(dielectric constant) must be selected to get good
performance. The (substrate thickness) should be
as low as it rises the surface wave affecting the entire
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performance. There are numerous forms of patches
namely rectangular, square, circular, and so on, [3].
For some design limitations, a rectangular patch
performs better than circular one. Numerous feeding
techniques are available to insert electromagnetic
energy into the antenna. The microstrip patch
supports a variety of new application sectors because
of its unique qualities, including mobile
communication, computer network systems, radar
applications, global positioning systems, smart IoT
devices, and so on, [4].
Fig. 1: Microstrip patch antenna
The major parameters namely VSWR, scattered
parameter, and radiation pattern verifies the operation
of an antenna. Energy transferred from source to load
is measured using VSWR. A good antenna must have
VSWR < 2, [5]. The radiation pattern is a graphical
representation of the far field which has information
about directivity, ML, and beam width. The input-
output relation can be described using scattered
parameters.
3 Phased Antenna Array and Beam
Steering
An arrangement of multiple single antenna elements
constitutes an array. The antenna element, amplitude
and (phase excitation) of each antenna and
geometry of the array are the factors controlling
radiation pattern. When the radiation pattern of
eeveryantenna adds up with na earby antenna to
derive a major beam, it is referred ato s phased
antenna array, [6]. The final electric field () is
given by, [7]: (1)
Where the single antenna field strength antenna
and AF the array factor can be written as:
(2)
Here, where d is the distance
between array elements and is the phase
difference. The directivity can be increased by either
increasing N or d. The first maxima occurs at n=0,
(3)
By changing, beam steering can be referred as the
manipulation of the direction of the ML without
disturbing the antenna where varies from
to.
4 Literature Review
Even though numerous significant research projects
have been carried out since its inception, the last few
years have seen an increase in the popularity of this
issue among researchers as a result of the publication
of numerous unique designs. A small compact
lightweight Rectangular Micro strip Patch Antenna
(RMPA) has been presented in, [8]. The proposed
antenna operates at a 2.45 GHz ISM band suitable for
Wireless LAN applications. The design is simulated
using CST Studio Suite 2015 software. The proposed
single-element RMPA shows low return loss (RL)
and gain of – 47.20 dB and 3.18 dB respectively.
In [9], the impulse properties of the antennas
used to play a crucial role in the very short-range
radar systems performance such as antipersonnel
landmine detection is achieved using ground
penetrating radar. The radar typically uses two
separate antennas, one for transmission and one for
reception. These antennas are typically close together
for mobility and proximity detectability reasons. To
accomplish their wideband performance such as
return loss, isolation, radiation patterns, polarization,
and impulse creation, a variety of design strategies
are applied. In [10], an RMPA with a sizable patch
was introduced. Despite having a high directivity, it
has a very low gain, a large return loss, and a low
voltage standing wave ratio (VSWR). An alternative
design with a taller form factor has been presented in,
[11]. Despite having a better gain than, [10], their
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design has a worse directivity and a middling return
loss.
Another RMPA with a large substrate, [12], and
noticeably high directivity and gain was proposed by
Shimu and Ahmed. However, it also exhibits
minimal return loss, and 5 because of its greater
dimension, its manufacturing cost would also be
higher. A more compact RMPA design with a
smaller patch size has been put forth in, [13]. The
gain and directivity are high, and the return loss
performance is also very good. Its VSWR
performance, however, is rather poor, and there is a
considerable gap between simulation and real-world
performance.
In [14], a microstrip patch phased array antenna
for GNSS augmentation has been proposed. The 2*3
phased array radiates at 1.278GHz which is the
center frequency of Galileo E6 band with a VSWR of
1.253, scanning angle of 49 and a gain of 11dBi.
The various parameters like S parameters, radiation
pattern, beam scanning, etc. have also been
measured.
In [15], designed a D-band phased array in
proximity coupled fed at 130-160GHz using CST
MWS software along with Ansys HFSS for
equalization. The designed antennas had a high peak
gain of 26.05dB; a high efficiency of 88.33%, and
good steering angles in the range -13.5 to 13.7 In
[16], a tri-band slotted bowtie ultra-wideband
antenna was designed on Sio2 laminate in Ansys
HFSS software. The maximum gain obtained was
17.53dB with directivity 18.2dBi, bandwidth 68.13%
and radiation efficiency of 71% with resonance
frequencies as 7.1, 11.1, and 13.1 THz.
5 Proposed Antenna Design
The antenna array is done by designing a single
rectangular patch with specific height and dielectric
constant so that 2.52 GHz resonant frequency (
can be achieved. For designing a rectangular patch
antenna, length (L) and width (W) have to be
calculated. The formula for calculating width and
length can be written respectively as, [17] [18]:
(4)
(5)
(6)
(7)
(8)
Where is the effective or efficient dielectric
constant is the efficient length and c is the light
speed. (Width) and (length) of the ground
plane can be calculated as:
(9)
The inset-fed single microstrip patch antenna is
designed on an FR-4 substrate for a good return loss.
The various parameters used are listed in Table 1.
Table 1. Dimensions of microstrip patch antenna
Parameters
Dimensions
Dielectric constant,
4.4
Substrate thickness,
1.6mm
Width of patch, W
71mm
Length of patch, L
54mm
Thickness of the patch,
0.032mm
Width of the ground plane,
220mm
Length of ground plane,
203mm
Microstrip feed width,
3.4mm
After analyzing the design of a single patch
antenna, a 2*2 array is constructed where the spacing
is equal between adjacent antennas. These antennas
are provided with ground maintaining 50 ohm
matching, [19], whereas some dimensions are
slightly optimized to get better results. The 2*2
antenna array design is shown in Figure 2.
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Fig. 2: Designed 2*2 phased array antenna
6 Results and Discussion
The patch array antenna is designed using Ansys
HFSS software. Figure 1 shows the single patch
antenna design which is designed and various
parameters are observed. It resonates at 2.7638GHz
frequency with an s parameter of -22.1541dB as
observed from the graph shown in Figure 3. The
VSWR value is illustrated in Figure 4 showing a
value of 1.1693 at the resonant frequency.
Fig. 3: S-parameter of single rectangular patch
Fig. 4: VSWR of single rectangular patch
Figure 5 shows the single rectangular patch’s
radiation pattern which shows that the ML has a
magnitude of 6.15dBi.
Fig. 5: Radiation pattern of the single rectangular
patch antenna
The antenna array is designed where all the ports
are given simultaneous excitation without any phase
change. All the antennas must resonate at the same
frequency. The S-parameter of the antenna is -
24.1279dB and is shown in Figure 6.
Fig. 6: S-parameter of the 2*2 array antenna
From Figure 6, it is inferred that the antenna
array resonates at 2.52GHz. The 2*2 array antenna’s
polar representation of radiation pattern without
phase manipulation is shown in Figure 7 indicating
that the ML magnitude is 11.35dBi and the direction
of ML is 0.
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Fig. 7: Radiation pattern of array antenna
The gain and current distribution for the 2*2
array antenna are shown in Figure 8 with the gain
value of 13.689dB at 2.52GHz.
(a)
(b)
Fig. 8: Radiation pattern of the array antenna (a) 3D
gain (b) current distribution
To find the scan angle’s range, the ports are
excited at the same amplitude with different phase
combinations. While simulating, the ML magnitude
and direction are examined from various angles. The
results show that the directivity and gain are
maximum at 14.055dB and 13.689dB respectively.
The gain plot for various angles is given in Figure 9.
Fig. 9: Polar gain plot for 2*2 array Antenna
The E-field and H-field pattern for the 2*2 array
antenna is shown in Figure 10. From the shown
simulation results, it is proven that for particular
phase combinations, the antenna’s main beam steers
to a particular direction up to a scanning range.
(a)
(b)
Fig. 10: (a) E-field pattern (b) H-field pattern of 2*2
array antenna
Table 2 gives the performance comparison of the
proposed antenna with the state of the art, [20], [21],
[22] and [23]. The gain of the antenna is improved.
Whereas the efficiency is less than the circular patch
proposed in [19] but better than other works available
in the literature.
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Table 2. Comparison with the state-of-art
VSWR
Gain
Efficienc
y %
Khattak19 (circular
patch)
1
13.5 dB
98
Zhang20 (MIMO
DRA)
1.244
7.02
dBi
85.5
Jebabli21 (1*4)
1.278
13 dB
86.73
Benlakehal22 (1*2)
-
11.77
dBi
87.63
Hrudananda23(circul
ar patch)
-
10.26
dBi
84.16
Proposed (2*2)
1.133
13.69
dB
91.91
7 Conclusion and Future Work
As in various communication fields like radar, and
satellites, beam steering not only increases the
integrity of the overall system but provides high
performance. In this paper a 2*2 phased array
antenna using microstrip patch with a scan angle of
47degrees is designed. The array antenna resonates at
2.52GHz with a VSWR of 1.1325. The S-parameter
values are below -10dB which is a threshold value
indicating a good resonance. Other parameters like
radiation pattern, gain, and directivity are also
evaluated for a better understanding of the antenna’s
performance. These antennas can be used as radars as
it has an efficiency of 91.91%. It can also be used for
ensuring accurate landing for airplanes. The
performance of the antenna can be further increased
by enhancing the number of antennae. Further,
studies will be done to improve the scan angle’s
range as well as gain, efficiency, and other
operational parameters.
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Contribution of Individual Authors to the
Creation of a Scientific Article (Ghostwriting
Policy)
- Mridula S. carried out the design, Simulation, and
Manuscript writing.
- Shantha Selva Kumar. R, guided in Problem
formation, Troubleshooting, and Manuscript
organization.
Sources of Funding for Research Presented in a
Scientific Article or Scientific Article Itself
No funding was received for conducting this work.
Conflict of Interest
The authors have no conflicts of interest to declare.
Creative Commons Attribution License 4.0
(Attribution 4.0 International, CC BY 4.0)
This article is published under the terms of the
Creative Commons Attribution License 4.0
https://creativecommons.org/licenses/by/4.0/deed.en_
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