Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
https://doi.org/10.1007/s10762-024-00979-w
REVIEW
Q‑Band MIMO Antennas with Circular Polarization
for Spatial and Polarization Diversity
Nada Alaa1 · Rania A. Elsayed1 · Asmaa E. Farahat2 · Khalid F. A. Hussein2 ·
Walid S. El‑Deeb1
Received: 25 October 2023 / Accepted: 7 March 2024 / Published online: 25 March 2024
© The Author(s) 2024
Abstract
The present work proposes three MIMO antennas with different configurations for
the future applications of wireless communications in the Q-band of the frequency
to realize both spatial and polarization diversities. A circularly polarized (CP)
printed antenna operating over two frequency bands at 37.8 and 50 GHz is utilized
as a single element to construct the proposed MIMO antennas. Two-element MIMO
antenna systems arranged in two configurations, side-by-side and face-to-face, are
proposed to achieve spatial diversity. Also, a four-element MIMO antenna system
is designed to achieve polarization diversity in addition to spatial diversity. The
proposed MIMO antenna systems are designed with the aid of the CST simulator.
The three MIMO antennas are fabricated and their performance is experimentally
evaluated regarding the circular polarization, impedance matching, antenna gain,
envelope correlation coefficient (ECC), and diversity gain (DG). The experimental
results for the single-element as well as the MIMO antennas come in good agreement with simulation results showing high performance. Both the numerical and
experimental investigations reveal that the mutual coupling between any two ports
of the proposed MIMO antennas is below −25dB. Also, for any two ports it is shown
that the ECC is below 1 × 10−7 and the diversity gain is higher than 9.99. The impedance matching bandwidths (for ||S11 || < −10dB) are shown to be 1.53 and 1.88 GHz
at 37.8 and 50GHz, respectively, and the corresponding 3-dB axial ratio bandwidths
are 700 and 130MHz, respectively.
Keywords Circular polarization · Dual-band · MIMO · Patch antenna · Polarization
diversity and spatial diversity
Extended author information available on the last page of the article
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1 Introduction
Multiple input multiple output (MIMO) antenna systems employ multiple radiating elements at the transmitter and the receiver. In MIMO system, the transmitter sends data over different multipath propagation then the receiver combines
these data through multipath. The main constraint in MIMO antenna system is
the uncorrelated multipath which can be provided by using antenna elements
acting independently. The MIMO technique provides uncorrelated multipath
propagation to attain different diversity schemes. A variety of diversity schemes
can be realized such as spatial (space) [1], polarization [2], frequency, pattern
(angular) [3–5], and transmit/receive diversity. Employing a dual-band antenna
system is preferred to employing two antenna systems operating at two different
frequencies because it provides a more compact solution especially for mobile
handsets. On the other hand, the circular polarization is preferred for a mobile
handset antenna because it allows receiving the power of the incoming signal
whether it is circularly polarized (CP) or linearly polarized (LP) without being
affected by the misalignment between the transmitting and the receiving antennas. The forthcoming generations of mobile handset need advanced features
such as wide bandwidth, high data rate, multiple frequency operation, compact
size, and light weight [6–8].
Recently, many research papers [9, 10] focus on the design of mobile handset
MIMO antennas for millimeter-wave communications. The work of [11] presents
a two-port triple-band MIMO antenna of two elements where each has a single
stub that can be embedded in the feed line. There are four symmetric square slots
and two cuts in the ground plane to realize circular polarization. The obtained
radiation patterns are quasi-omnidirectional. In [12], a dual-band dual-polarized
(DBDP) MIMO antenna is designed by using square patch with three rectangular slits and a decoupling mechanism is embedded in the ground structure to
enhance the isolation. The non-diagonal slit is responsible for circular polarization. This design is based on the single-feed dual-band antenna and the dual
polarization is realized by using an orthogonal feed. There is another category
based on using stacked structure that consists of two elements operating at two
different frequency bands. In [13], a penta-band MIMO antenna is introduced by
adding meander line-shaped radiator with L-shaped matching stub, and ground
plane having semi-circle-shaped slot, and inverted L-shaped stub. The proposed
four-element MIMO has circular polarization in only two bands. The isolation
technique used in design is the inverted L-shaped decoupling structure. In [1],
circularly polarized four-element MIMO dielectric resonator antenna (DRA)
operating at two frequency bands is studied. We aim to achieve some objectives
such as bandwidth enhancement by using a ring-shaped ceramic radiator, dual
bands by using incorporation of a rectangular aperture lead, circular polarization by using conversion of rectangular to Z-shaped slot, and reduction of mutual
coupling by using space diversity. The work of [14] illustrates the DRA technique
for two-port dual-band MIMO antenna with circular polarization. For exciting
HE modes, two probes placed orthogonal, that is, an azimuthal angular distance
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395
of 90◦, to each other are used. Moreover, to realize the required quadrature timephase between these modes, the length of two probes must be tuned. The two ring
DRAs are excited by using two arc-shaped feed lines with four conformal probes.
In [15], a dual-band circularly polarized dielectric resonator antenna is used to
implement two-port MIMO antenna that consists of a moon-shaped aperture. To
stimulate ring-shaped DRA, L-shaped microstrip line with a serial step impedance transformer is used. Modification from cylindrical to ring-shaped dielectric resonator provides wide impedance bandwidth. Aperture is helpful to excite
the dual orthogonal hybrid modes for circular polarization waves. Polarization
diversity is supportive to reduce the mutual coupling between ports. A broadband
antenna operating over the 38 GHz frequency band is proposed in [16], using circular patch antenna loaded by three patches between circular radius and feed-line
and perpendicular pair of elliptical slots inside the circular patch. This antenna
has small size with 7-dB gain and 90% radiation efficiency. In [17] and [18], a
compact multiband antenna operating at 28, 38, and 55 GHz is introduced. The
antenna has an umbrella-shaped patch with high gain and efficiency. A wideband,
high-gain, low-profile, and high-efficiency fractal antenna operating at 39 GHz is
investigated in [19]. The antenna is designed on a Rogers RT/duroid 5880 with a
compact size of 15 × 15 × 0.79 mm.
This work introduces two-element as well as four-element MIMO antenna
systems to achieve spatial diversity as well as polarization diversity for millimeter wave (mm-wave) applications. A dual-band circularly polarized (DBCP)
microstrip patch antenna is used as a single element to construct the proposed
MIMO antennas. The single element is designed as a main patch and a parasitic patch. The main patch has circular geometry with two square slots at the
center and two notches on the circumference. The parasitic patch consists of four
parasitic elements indirectly fed by capacitively coupling to the main patch. To
produce circular polarization, the structure of the single element antenna is symmetric about an axis that is inclined to the feed line at angle of 45◦ . For impedance matching, the main patch is fed through a microstrip line with tapered
geometry.
Two-element MIMO antenna systems are proposed to produce spatial diversity: face-to-face and side-by-side arrangements. The four-element MIMO
antennas are proposed to produce both spatial and polarization diversity at the
same time. If the elements have the same sense of polarization, then spatial
diversity is obtained, whereas polarization diversity is obtained if the elements
have different senses of polarization. The proposed MIMO antenna systems
have two operational frequency bands centered at 38 and 50 GHz and produce
circular polarization over the two frequency bands. The diversity schemes provided by these MIMO antennas are investigated by the CST simulator where
the envelope correlation coefficient (ECC) and the diversity gain (DG) are
investigated and demonstrated.
The presentation of this work is organized as follows. Section 2 presents the
design of the single-element dual-band CP antenna. Section 3 introduces the proposed MIMO antennas with the different configurations. Section 4 describes the fabrication process and the experimental setup for measurements. Section 5 presents
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the simulation and experimental results with elaborate discussions for performance
assessment. Section 6 introduces a summary of this work and some comparisons to
the achievements of the other published papers. Finally, Section 7 gives the conclusions related to the present work.
2 Design of Single‑Element Antenna
The geometry of the CP patch antenna proposed as a single element for the
two-element and four-element MIMO antenna systems is depicted in Fig. 1.
This antenna consists of a circular patch that acts as the main radiator which
is reactively loaded by four parasitic patches as seen in Fig. 1a. To produce
circular polarization, two square slots are made near the patch center and two
notches are etched at the patch edge to get the line of symmetry of the antenna
structure having a slope of 45◦ with the center line of the feeding microstrip
line. Also, the ground structure is defected by etching two square slots as
shown in Fig. 1b. Thus, the overall patch and defected ground geometry have a
line of symmetry making 45◦ with the center line of the microstrip line feeder.
This symmetry produces two degenerate radiating modes (resonances) of the
cavity between the circular patch and the ground plane. The radiated fields of
the two modes have nearly equal magnitudes, orthogonal orientations, and inphase quadrature; these conditions produce a circularly polarized field in the
far zone of the antenna. The antenna’s geometrical parameters should be set to
the appropriate values to satisfy these conditions. The antenna impedance is
matched at the desired frequencies by the tapered microstrip line feeder. The
dimensions of the tapered region of this line, WT , LT , and WF , should be set
to get the antenna impedance matched to 50Ω source at the required frequencies. The parasitic elements help to get the antenna impedance matched over
a higher frequency band. The Y-shaped slits at the corners of the parasitic elements improve the axial ratio and increase its 3-dB bandwidth. The geometric
symmetry of the antenna around an axis inclined to the feed line at an angle
of 45◦ produces right-hand circularly polarized (RHCP) field in the far zone.
If this geometry is mirrored about the centerline of the microstrip feeder, lefthand circularly polarized (LHCP) fields are produced in the far zone. It will be
shown, later, that two antennas of opposite senses of polarization can be used
in a four-element MIMO antenna configuration to provide polarization diversity in addition to the spatial diversity.
The optimal dimensions of this antenna are listed in Table 1. It should be noted
that these dimensions have been obtained through an extensive parametric study
that has been achieved using the CST simulator. The proposed MIMO is designed
using a substrate material of the type Rogers RO3003. The substrate has a thickness h = 0.25mm , loss tangent tan𝛿 = 0.001, and dielectric constant 𝜀r = 3.
In this section, two-element and four-element configuration of MIMO antenna
systems are proposed to produce spatial and polarization diversity. The design of
the proposed MIMO antennas are presented in the following subsections.
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(a)
(b)
(c)
(d)
Fig. 1 Structure of the dual-band circularly polarized single-element patch antenna. a Top view. b Bottom view. c Detailed view of the patch. d Close view at one notch on the patch circumference
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Table 1 Optimum values of the dimensions of the single-element antenna proposed for different MIMO
antenna configurations
Dimension
RP
LP
WF
LF
WT
LT
WG
G
WE
WS
LC
WY
LY
DY
Value (mm)
1.17
2.9
0.6
11.05
0.1
7.6
0.6
1.414
0.13
0.2
0.4
0.13
0.2
0.18
3 Proposed MIMO Antenna Systems
In this section, the designs of the proposed MIMO antennas are described in
detail. Two-element MIMO antennas arranged in side-by-side and face-to-face
configurations are designed to produce spatial diversity. Also, four-element
MIMO antenna system is designed to produce both spatial and polarization diversity. The following two subsections are dedicated for the description of the different types of the proposed MIMO antenna configurations.
3.1 Two‑Port MIMO Antenna Configurations for Spatial Diversity
Two configurations are proposed to construct two-element MIMO antennas by using
the CP patch described in Section 2. In the first configuration, the patch antennas are
arranged side-by-side, whereas in the other configuration, the two patch elements
are arranged face-to-face as shown.
For two-element MIMO antenna, the ECC can be expressed as follows [20]:
ECC1,2
| ∗
|2
∗
S22 |
|S11 S12 + S21
|
|
=
2
2
2
2 ∗
(1 − ||S11 || − ||S12 || )(1 − ||S21 || − ||S22 || )
For two-element MIMO antenna, the DG can be expressed as follows [20]:
√
DG = 10 1 − |ECC|2
(1)
(2)
Each of the proposed two-element MIMO antenna configurations may have different performance from the other and both are investigated in the present work.
The next two subsections are dedicated to describe the designs of the proposed twoelement MIMO configurations.
3.1.1 Two‑Element MIMO Antenna in Side‑by‑Side Configuration
In the two-element side-by-side MIMO antenna configuration, the patch antennas
are arranged as shown in Fig. 2. If the two elements in this MIMO antenna configuration have the same sense of polarization, then spatial diversity is produced. If an
element is LHCP whereas the other element is RHCP, then polarization diversity is
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RHCP
399
RHCP
1
2
(b)
(a)
Fig. 2 Design of the two-element side-by-side MIMO antenna using two elements of the dual-band circularly polarized antenna. a Top view. b Bottom view
2
1
RHCP
RHCP
(a)
(b)
Fig. 3 Design of the two-element face-to-face MIMO antenna using two elements of the dual-band circularly polarized antenna. a Top view. b Bottom view
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produced. In this MIMO antenna, the elements are printed on the same substrate.
The overall physical dimensions of the two-element side-by-side MIMO antenna
are L1 = 19mm and W1 = 18.5mm . The spacing between the antenna elements is
DS = 6.1mm.
3.1.2 Two‑Element MIMO Antenna in Face‑to‑Face Configuration
In the two-element face-to-face MIMO antenna configuration, the patch antennas
are arranged as shown in Fig. 3. If the two elements in this MIMO antenna configuration have the same sense of polarization, then this MIMO antenna produces spatial
diversity. If an element is LHCP whereas the other element is RHCP, then polarization diversity is produced. In this MIMO antenna, the elements are printed on the
same substrate. The overall physical dimensions of the two-element face-to-face
MIMO antenna are L2 = 32mm and W2 = 10mm . The spacing between the antenna
elements is DF = 4.66mm.
3.2 Four‑Element MIMO Configuration for Both Spatial and Polarization Diversity
Four elements of the dual-band CP antenna, described in Section 2, are arranged as
shown in Fig. 4 to implement the proposed MIMO antenna system. To obtain polarization diversity in addition to the spatial diversity by such four-element MIMO
antenna, elements 1 and 4 are RHCP, whereas elements 2 and 3 are LHCP. In this
way, both spatial and polarization diversities are obtained. The separation distances
between the elements are DS = 6.1mm and DF = 4.66mm . The total dimensions of
the four-element MIMO antenna are L3 = 32mm and W3 = 18.5mm.
4 Fabrication and Experimental Setup for Measurements
Prototypes are fabricated for experimental evaluation of the proposed single-element
and MIMO antennas’ performance. The reflection coefficient at the antenna input
ports and the radiation patterns are measured and compared to the simulation results.
4.1 Fabricated Prototypes
Prototypes are fabricated for the single-element, two-element side-by-side MIMO,
two-element face-to-face MIMO, and four-element MIMO antennas whose designs
are presented in Figs. 1, 2, 3, and 4, respectively. The fabricated prototypes are presented in Fig. 5. The elements of the MIMO antennas are fed at each port through
1.85-mm coaxial end launchers from Southwest Microwave Inc. The purpose of fabricating these prototypes is the experimental evaluation of the antenna performance
for comparison with the simulation results.
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401
3
1
RHCP
LHCP
LHCP
RHCP
2
4
(a)
(b)
Fig. 4 Design of the four-element MIMO antenna system using four dual-band circularly polarized patch
antennas. a Top view. b Bottom view
4.2 Measurement of the Self and Mutual Scattering Parameters
The self and mutual scattering parameters are measured with the aid of the VNA
model Rhode and Schwartz ZVA67. The end-launch connectors of type 1.85mm
from Southwest Microwave Inc. are used to connect the antennas under test to the
VNA for measurement as shown in Figs. 6 and 7.
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Fig. 5 Fabricated prototypes of the proposed antennas. a Single element. b Two-element side-by-side
MIMO antenna. c Two-element face-to-face MIMO antenna. d Four-element MIMO antenna
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403
Fig. 6 Measurement of the S-parameter, S11, of the fabricated single-element antenna. a The antenna
connected to the VNA cable via the end-launch connector. b Experimental setup showing the antenna
connected to port 2 of the VNA
Fig. 7 Measurement of the S-parameters, S11, S22, and S21, of the two-element side-by-side fabricated
prototypes. a Two fabricated elements arranged side-by-side and connected to the VNA cables via the
end-launch connectors. b Experimental setup showing two-element MIMO antenna connected to ports 1
and 2 of the VNA
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VNA Cables
(2)
(1)
Fig. 8 The fabricated two-element face-to-face MIMO antenna is prepared for measuring the self and
mutual scattering parameters, S11, S22, and S21
Matched Loads
VNA Cables
(1)
(3)
(2)
(4)
Fig. 9 The fabricated four-element MIMO antenna is prepared for measuring the self and mutual scattering parameters, S11, S22, and S21. The VNA cables are connected to ports 1 and 2 and matched loads are
connected to ports 3 and 4 of the MIMO
The fabricated prototypes of the two-element (face-to-face) and the four-element
antennas are prepared for measuring the self and mutual the S-parameters, S11, S22,
and S21, as seen in Figs. 8 and 9, respectively.
4.3 Measurement of the Radiation Patterns
The gain and radiation patterns of the proposed single-element and MIMO antennas
are measured by the aid of the VNA. The experimental setup is presented in Fig. 10
showing the reference gain linearly polarized horn antenna mounted on the polarization rotator, the antenna-under-test (AUT) mounted on the directional rotator. The
horn antenna model LB-018400 is employed to perform measurements over the frequency range of 18–40 GHz while the horn antenna model LB-12–10-A is employed
to perform measurements over the frequency range of 40–60 GHz. The AUT and the
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405
VNA (ZVA67)
Antenna under
Test
Reference Horn
Antenna
Antenna Rotator
Fig. 10 Gain and radiation pattern pattern measurement setup showing the AUT and reference horn
antenna connected to ports 1 and 2 of the VNA, respectively
0
|S 11 | (dB)
-10
-20
Simulation
Measurement
-30
-40
30
35
40
45
50
55
Frequency (GHz)
Fig. 11 Results of simulation and measurement of the reflection coefficient magnitude, ||S11 ||, at the feeding port of the single-element antenna over a broad frequency band
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reference-gain horn antenna are connected to ports 1 and 2 of the VNA, respectively.
The ratio of the received power to the transmitted power is assessed by the magnitude of the transmission coefficient,||S21 ||, between AUT and the reference antenna.
5 Results and Discussions
The simulation results and experimental measurements are presented and discussed in this section. The main concern of such presentations is the performance
evaluation of the single-element antenna as well as the MIMO antennas with the
different configurations proposed in the present work.
5.1 Performance Evaluation of the Single‑Element Antenna
The frequency dependence of ||S11 || at the feeding port of the single-element dualband circularly polarized antenna, described in Section 2, is investigated by simulation as well as experimental measurement at the frequencies ranging from 34 to
54 GHz. Figure 11 shows that the measurements are very close to the simulation
results. It is shown that the antenna impedance is perfectly matched to 50Ω over
the two frequency bands at 38 and 50 GHz.
6
6
5
5
4
4
AR (dB)
AR (dB)
Simulation
Measurement
3
3
2
2
1
1
Simulation
Measurement
0
36.5
37
37.5
38
Frequency (GHz)
(a)
38.5
0
49.6
49.8
50
50.2
50.4
Frequency (GHz)
(b)
Fig. 12 Results of simulation and measurement of the AR over (a) the lower frequency band and (b) the
higher frequency band
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0
0
0 dB
30
60
-40
-60
90
90
-60
Simulation
Measurement
90
Simulation
Measurement
120
120
150
30
-20
60
60
-40
90
0 dB
30
30
-20
60
407
120
150
120
150
150
180
180
(a)
(b)
Fig. 13 Total field radiation patterns of the single-element antenna at 37.8GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
0
0
30
0 dB
-20
60
30
30
90
-60
90
-60
90
Simulation
Measurement
Simulation
Measurement
120
120
150
60
-40
-40
90
30
-20
60
60
0 dB
150
120
120
150
150
180
180
(a)
(b)
Fig. 14 Total field radiation patterns of the single-element antenna at 50GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
The variations of the AR of the single-element antenna with the frequency
around the frequencies 37.8 and 50GHz are presented in Fig. 12a and b, respectively. As shown in these figures, the experimental measurements show excellent
agreement with the simulation results. The 3dB-AR bandwidth at 37.8 and 50GHz
are 700 and 300 MHz, respectively.
The total far-field radiation patterns of the single-element antenna at 38 and
50 GHz are depicted in Figs. 13 and 14, respectively. The radiation patterns produced at the two frequencies show that this single-element antenna is a good candidate to construct MIMO antenna systems with high performance.
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0
|S 11 | (dB)
-10
-20
Simulation
Measurement
-30
-40
30
35
40
45
50
55
Frequency (GHz)
Fig. 15 Results of simulation and measurement of ||S11 || at port 1 of the two-element side-by-side MIMO
antenna over a broad frequency band
-20
|S 21 | (dB)
-30
-40
-50
-60
Simulation
Measurement
-70
-80
30
35
40
45
50
55
Frequency (GHz)
Fig. 16 Results of simulation and measurement of the mutual coupling coefficient, ||S21 ||, of the two-element side-by-side MIMO antenna
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0
30
409
0
30
0 dB
30
0 dB
-5
-5
60
60
60
60
-10
-10
-15
90
-15
-20
90
=0o
=90 o
120
30
150
120
-20
90
90
=0o
120
120
=90 o
150
150
150
180
180
(a)
(b)
Fig. 17 Total field radiation patterns of the two-element side-by-side MIMO antenna at 37.8GHz when
fed at (a) port 1 and (b) port 2
0
0
30
30
30
0 dB
-5
60
60
60
-10
-10
-15
-15
90
-20
=0o
120
=90
150
30
-5
60
90
0 dB
120
-20
90
90
=0o
120
120
=90 o
o
150
150
150
180
180
(a)
(b)
Fig. 18 Total field radiation patterns of the two-element side-by-side MIMO antenna at 50GHz when fed
at (a) port 1 and (b) port 2
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0
0
0 dB
30
30
0 dB
30
-5
-5
60
60
60
60
-10
-10
90
90
-15
90
-15
EL
120
120
EL
150
90
ER
ER
120
30
150
150
120
150
180
180
(a)
(b)
Fig. 19 Radiation patterns of the CP field components ( ER and EL ) of the two-element side-by-side
MIMO antenna (port 1) at 37.8 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
0
30
0
0 dB
30
30
-5
60
60
-10
90
-10
-15
90
ER
120
120
EL
150
30
-5
60
60
0 dB
90
-15
90
ER
120
120
EL
150
150
150
180
180
(a)
(b)
Fig. 20 Radiation patterns of the CP field components ( ER and EL ) of the two-element side-by-side
MIMO antenna (port 1) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
5.2 Performance Evaluation of the Two‑Element MIMO Antennas
The purpose of the next two subsections is to investigate the performance of the
two-element MIMO configurations proposed in Section 3.1 regarding the impedance matching at each port, radiation patterns, coupling coefficient between the
two ports, ECC, and DG.
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411
0
0
0 dB
30
30
0 dB
30
-5
60
-5
60
60
60
-10
90
-10
-15
90
ER
120
120
EL
150
30
90
-15
ER
120
150
90
120
EL
150
150
180
180
(a)
(b)
Fig. 21 Radiation patterns of the CP field components ( ER and EL ) of the two-element side-by-side
MIMO antenna (port 2) at 37.8 GHz. a 𝜙 = 0◦ b. 𝜙 = 90◦
0
0
0 dB
30
30
30
-5
60
60
-10
90
-10
-15
90
ER
120
120
90
-15
150
90
ER
120
120
EL
EL
150
30
-5
60
60
0 dB
150
150
180
180
(a)
(b)
Fig. 22 Radiation patterns of the CP field components ( ER and EL ) of the two-element side-by-side
MIMO antenna (port 2) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
5.2.1 Two‑Element Side‑by‑Side MIMO Antenna
In this section, the performance of a MIMO antenna system composed of two
elements of the antenna described in Section 2 is investigated by simulation as
well as experimental measurement. The two elements are placed side-by-side, as
presented in Figs. 2 and 5b, to produce spatial diversity. The frequency dependence of the reflection coefficient at port 1 is presented in Fig. 15. By comparison between Figs. 15 and 11, it is shown that the frequency response of ||S11 || of
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0
|S 11 | (dB)
-10
-20
-30
Simulation
Measurement
-40
30
35
40
45
50
55
Frequency (GHz)
Fig. 23 Results of simulation and measurement of ||S11 || at port 1 of the two-element face-to-face MIMO
antenna over a broad frequency band
the two-element MIMO antenna is almost identical to that of the single-element
antenna.
The isolation between the two elements of this MIMO antenna can be measured by the magnitude of the coupling coefficient, ||S21 ||, whose frequency response
is shown in Fig. 16. The magnitude of this coefficient is maintained below − 24
dB over the entire frequency range of investigation showing good performance of
the proposed side-by-side MIMO antenna. Also, it is shown that the simulation
-10
|S 21 | (dB)
-20
-30
-40
-50
Simulation
Measurement
-60
-70
30
35
40
45
50
55
Frequency (GHz)
Fig. 24 Results of simulation and measurement of the mutual coupling coefficient, ||S21 ||, of the two-element face-to-face MIMO antenna
13
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
30
0
0 dB
30
30
0
0 dB
60
60
60
-10
-10
-15
-15
90
-20
90
-20
=90
120
o
150
90
=0o
=90 o
=0o
120
30
-5
-5
60
90
413
120
150
150
120
150
180
180
(a)
(b)
Fig. 25 Radiation patterns of the total field radiated by the two-element face-to-face MIMO antenna at
37.8GHz when it is fed using (a) port 1 and (b) port 2
results and experimental measurements of ||S11 || and ||S21 || show good agreement
with each other.
The radiation patterns of the two-element side-by-side MIMO antenna at 37.8
GHz when excited at ports 1 and 2 are presented in Fig. 17a and b, respectively. The
far-field patterns produced at 50 GHz when this MIMO antenna is fed at ports 1 and
2 are presented in Fig. 18a and b, respectively. Irrespective of the port of excitation
of this MIMO antenna, the values of the maximum gain achieved at 37.8 and 50
GHz are 7 and 6.8 dBi, respectively.
30
0
0 dB
30
30
-5
60
60
60
-10
-10
-15
-15
-20
90
=0o
=90 o
120
150
30
-5
60
90
0
0 dB
120
150
-20
90
90
=0o
=90 o
120
150
120
150
180
180
(a)
(b)
Fig. 26 Radiation patterns of the total field radiated by the two-element face-to-face antenna at 50GHz
when it is fed using (a) port 1 and (b) port 2
13
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
0
0
0 dB
30
30
0 dB
30
-5
-5
60
60
60
60
-10
90
-10
-15
90
ER
120
120
90
-15
90
ER
120
120
EL
EL
150
30
150
150
150
180
180
(a)
(b)
Fig. 27 Radiation patterns of the CP field components ( ER and EL ) of the two-element face-to-face
MIMO antenna (port 1) at 37.8 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
0
30
0
0 dB
30
30
-5
60
60
-10
90
-10
-15
90
ER
120
120
90
90
-15
ER
120
120
EL
EL
150
30
-5
60
60
0 dB
150
150
150
180
180
(a)
(b)
Fig. 28 Radiation patterns of the CP field components ( ER and EL ) of the two-element face-to-face
MIMO antenna (port 1) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
When the side-by-side MIMO antenna is fed using port 1, the patterns of
the CP field components at 37.8 and 50 GHz are presented in Figs. 19 and 20,
respectively. When the same MIMO antenna is fed using port 2, the CP field
patterns at 37.8 and 50 GHz are presented in Figs. 21 and 22, respectively. It is
seen that the radiated field is dominated by RHCP component at both the lower
and higher frequencies. However, the cross-polarization level of the radiated
field at 50GHz is significantly higher than that of the radiated field at 37.8GHz .
13
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
0
0
0 dB
30
415
30
0 dB
30
-5
-5
60
60
60
60
-10
-10
90
-15
90
90
-15
120
120
EL
150
90
ER
ER
120
30
150
150
120
EL
150
180
180
(a)
(b)
Fig. 29 Radiation patterns of the CP field components ( ER and EL ) of the two-element face-to-face
MIMO antenna (port 2) at 37.8 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
0
30
0
0 dB
30
30
-5
60
60
60
-10
-10
-15
90
ER
120
120
90
-15
90
ER
120
EL
150
30
-5
60
90
0 dB
120
EL
150
150
150
180
180
(a)
(b)
Fig. 30 Radiation patterns of the CP field components ( ER and EL ) of the two-element face-to-face
MIMO antenna (port 1) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
This means that the proposed two-element side-by-side MIMO antenna produces more perfect circular polarization at 37.8 GHz that that produced at 50
GHz. This MIMO antenna produces the same type of polarization when fed
using port 1 or port 2. Therefore, it can be employed to obtain spatial diversity
but not polarization diversity.
13
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
Fig. 31 Dependence of the ECC of the two-element MIMO antenna on the frequency around (a) 37.8
GHz and (b) 50 GHz
Fig. 32 Dependence of the DG of the two-element MIMO antenna on the frequency around (a) 37.8
GHz and (b) 50 GHz
5.2.2 Two‑Element Face‑to‑Face MIMO Antenna
The MIMO antenna system performance, which is composed of two elements of the
CP antenna described in Section 2, is investigated by simulation as well as experimental measurement. The two elements are placed face-to-face, as presented in
Figs. 3 and 5c, to produce spatial diversity. The frequency dependence of the reflection coefficient at port 1 is presented in Fig. 23. By comparison between Figs. 23
and 11, it is shown that the frequency response of ||S11 || of the two-element MIMO
antenna is almost identical to that of the single-element antenna. Also, it is shown
that the experimental measurements of ||S11 || come in good agreement with simulation results.
13
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
417
0
|S 11 | (dB)
-10
-20
-30
Simulation
Measurement
-40
30
35
40
45
50
55
60
Frequency (GHz)
Fig. 33 Variation of ||S11 ||, at port 1 of the four-element MIMO configuration with the frequency over a
broad frequency band
Fig. 34 Variation of the mutual
coupling coefficients, ||S21 ||, ||S31 ||,
and ||S41 ||, of the four-element
MIMO antenna with the frequency
The isolation between the two elements of this MIMO antenna can be measured by the magnitude of the coupling coefficient, ||S21 ||, whose frequency response
is presented in Fig. 24. The magnitude of the coupling coefficient is maintained
below − 20 dB over the entire frequency range of investigation showing good performance of the face-to-face MIMO antenna system. As seen, the measurements
of ||S21 || are close to the results obtained by simulation.
The total field radiation patterns of the face-to-face MIMO antenna at 37.8 GHz
when fed at ports 1 and 2 are presented in Fig. 25a and b, respectively. The far-field patterns produced at 50 GHz when it is fed at ports 1 and 2 are presented in Fig. 26a and b,
respectively. Irrespective of the port of excitation of this MIMO antenna, the values of
the peak gain achieved at 37.8 and 50 GHz are 7.6 and 6.55 dBi, respectively.
13
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
-20
-30
|S 21 | (dB)
-40
-50
-60
-70
Simulation
Measurement
-80
-90
30
35
40
45
50
55
Frequency (GHz)
Fig. 35 Variation of the coupling coefficient, ||S21 ||, between ports 1 and 2 of the four-element MIMO
antenna
0
0
30
0 dB
30
30
0 dB
-5
-5
60
60
60
60
-10
-10
-15
-15
90
-20
120
90
120
=0o
90
-20
120
90
120
=0o
=90 o
150
30
=90 o
150
150
150
180
180
(a)
(b)
Fig. 36 Radiation patterns of the total field radiated by the four-element MIMO antenna (port 1) at (a)
37.8GHz and (b) 50 GHz
The patterns of the circularly polarized field components produced by the faceto-face MIMO antenna in the far zone at 37.8 and 50 GHz, are shown in Figs. 27
and 28, respectively, when the MIMO antenna is excited at port 1, and Figs. 29
and 30, respectively, when fed at port 2. It is seen that the far field is mainly
RHCP at both the lower and higher frequencies. However, the cross-polarization
level of the radiated field at the upper band of frequencies is significantly higher
13
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
419
0
0
0 dB
30
0 dB
30
30
-5
-5
60
60
60
60
-10
-10
-15
90
-15
-20
120
30
90
120
=0o
=90
90
-20
120
150
=90
150
120
=0o
o
150
o
150
180
180
(a)
(b)
Fig. 37 Radiation patterns of the total field radiated by the four-element MIMO antenna (port 2) at (a)
37.8GHz and (b) 50 GHz
0
30
0
0 dB
30
30
0 dB
-5
60
60
60
60
-10
-10
-15
90
-15
-20
120
90
120
=0o
=90
150
30
-5
90
-20
120
120
=0o
o
=90
150
90
150
o
150
180
180
(a)
(b)
Fig. 38 Radiation patterns of the total field radiated by the four-element MIMO antenna (port 3) at (a)
37.8GHz and (b) 50 GHz
than that of the far field at the lower band of frequencies. This means that the
proposed two-element face-to-face MIMO antenna produces more perfect circular
polarization at 37.8 GHz that that produced at 50 GHz. This MIMO antenna produces the same type of polarization when fed at port 1 or port 2. Therefore, it can
be employed to obtain spatial diversity but not polarization diversity.
13
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
0
0
0 dB
30
0 dB
30
30
-5
-5
60
60
60
60
-10
-10
-15
-15
90
-20
120
90
120
=0o
=90
30
90
-20
120
120
=0o
=90 o
o
150
90
150
150
150
180
180
(a)
(b)
Fig. 39 Radiation patterns of the total field radiated by the four-element MIMO antenna (port 4) at (a)
37.8GHz and (b) 50 GHz
0
30
0
0 dB
30
30
-5
60
60
60
-10
-10
-15
90
ER
120
120
EL
150
30
-5
60
90
0 dB
90
-15
90
ER
120
120
EL
150
150
150
180
180
(a)
(b)
Fig. 40 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 1) at 37.8 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
5.2.3 ECC and DG of the Two‑Element MIMO Antennas
The ECC and DG obtained by the side-by-side and face-to-face MIMO antenna
configurations are presented in Figs. 31 and 32, respectively, over the operating frequency bands. It is seen that the ECC is very small (< 10−3) and the DG is almost 10
over both the frequency bands indicating excellent diversity properties.
13
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
0
0
0 dB
30
60
60
60
-10
-10
-15
90
ER
120
90
90
-15
ER
120
120
EL
EL
150
30
-5
-5
120
0 dB
30
30
60
90
421
150
150
150
180
180
(a)
(b)
Fig. 41 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 1) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
0
0
30
0 dB
30
30
60
60
60
-10
-10
-15
90
ER
120
120
-15
90
90
ER
120
EL
150
30
-5
-5
60
90
0 dB
120
EL
150
150
150
180
180
(a)
(b)
Fig. 42 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 2) at 37.8 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
5.3 Performance Assessment of the Four‑Element MIMO Antenna
The four-element MIMO antenna system presented in Fig. 4 is designed to obtain
both spatial and polarization diversity. Elements 1 and 4 produce RHCP radiation,
whereas elements 2 and 3 produce LHCP radiation.
13
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
0
0
0 dB
30
60
60
60
-10
-10
-15
90
ER
120
120
90
-15
90
ER
120
150
150
120
EL
EL
150
30
-5
-5
60
90
0 dB
30
30
150
180
180
(a)
(b)
Fig. 43 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 2) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
0
0
30
0 dB
30
30
60
60
60
-10
-10
90
-15
ER
120
120
90
-15
150
90
ER
120
120
EL
EL
150
30
-5
-5
60
90
0 dB
150
150
180
180
(a)
(b)
Fig. 44 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 3) at 37.8 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
5.3.1 Mutual Effects between the Elements of the Four‑Element MIMO Antenna
The frequency response of ||S11 || is presented in Fig. 33. The mutual S-parameters
of this MIMO antenna are presented in Figs. 34 and 35. By comparing the frequency response of ||S11 || of the four-element MIMO antenna presented in Fig. 42
to that of the single-element antenna presented in Fig. 11, it is seen that they are
13
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
0
0
0 dB
30
423
30
0 dB
30
-5
60
-5
60
60
60
-10
90
-10
90
-15
ER
120
120
90
90
-15
ER
120
120
EL
EL
150
30
150
150
150
180
180
(a)
(b)
Fig. 45 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 3) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
0
30
0
0 dB
30
30
-5
60
60
60
-10
-10
90
-15
ER
120
120
EL
150
30
-5
60
90
0 dB
90
-15
90
ER
120
120
EL
150
150
150
180
180
(a)
(b)
Fig. 46 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 4) at 37.8 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
almost identical. This indicates that the mutual coupling between the elements of
the MIMO antenna is very weak, which is emphasized by the frequency responses
of the mutual S-parameters presented in Figs. 43 and 44. It is shown that the magnitudes of the mutual S-parameters among the various ports are below −24dB;
such low values of the mutual coupling show good isolation between the elements
and, hence, excellent diversity is provided by this MIMO antenna.
13
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
0
0
0 dB
30
0 dB
30
30
-5
-5
60
60
60
60
-10
-10
90
-15
90
ER
120
90
ER
120
120
90
-15
120
EL
EL
150
30
150
150
150
180
180
(a)
(b)
Fig. 47 Radiation patterns of the CP field components ( ER and EL ) of the four-element MIMO antenna
(port 4) at 50 GHz. a 𝜙 = 0◦. b 𝜙 = 90◦
1
10-3
1
Port 1&2
Port 1&3
Port 1&4
0.6
0.4
0.2
0
36.5
Port 1&2
Port 1&3
Port 1&4
0.8
ECC (dB)
ECC (dB)
0.8
10-3
0.6
0.4
0.2
37
37.5
Frequency (GHz)
38
38.5
0
49.5
50
50.5
Frequency (GHz)
(a)
(b)
Fig. 48 Variation of the ECC of the four-element MIMO antenna with the frequency around (a) 37.8
GHz and (b) 50 GHz
5.3.2 Radiation Patterns of the Four‑Element MIMO Antenna
The radiation patterns of the total field produced by the four-element MIMO antenna
when excited at ports 1, 2, 3, and 4 are presented in Figs. 36, 37, 38, and 39, respectively, at the lower and higher operational frequencies of the proposed MIMO antenna.
The radiation patterns of the CP field components radiated by the four-element MIMO antenna when fed at port 1 at the two operating frequencies 37.8
and 50 GHz are presented in Figs. 40 and 41, respectively. The radiation patterns
obtained when the antenna is fed at port 2 at the same frequencies are shown in
Figs. 42 and 43. Also, the radiation patterns at both frequencies are calculated
13
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
10
425
10
9.999
9.995
DG (dB)
DG (dB)
9.998
9.997
9.996
9.99
9.995
Port 1&2
Port 1&3
Port 1&4
9.994
9.993
36.5
37
37.5
Frequency (GHz)
(a)
38
Port 1&2
Port 1&3
Port 1&4
38.5
9.985
49.5
50
50.5
Frequency (GHz)
(b)
Fig. 49 Variation of the DG of the four-element MIMO antenna with the frequency around (a) 37.8 GHz
and (b) 50 GHz
Fig. 50 Surface current distribution over the patches of the face-to-face MIMO antenna system at (a) 28
GHz and (b) 38 GHz
when the antenna is fed through port 3 and port 4 as illustrated in Figs. 44 and
45, and, Figs. 46 and 47, respectively. It is shown that when port 1 or 4 is used
to feed the MIMO antenna, the far field is dominated by RHCP component. On
the other side, the far field is dominated by LHCP component when port 2 or
3 is used for feeding the MIMO antenna. It is shown that the cross-polarization level at the higher frequency band is significantly higher than that obtained
at the lower frequency band. This means that the four-element MIMO antenna
13
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
Fig. 51 Surface current distribution over patch 1 of the face-to-face MIMO antenna system at (a) 28 GHz
and (b) 38 GHz
Fig. 52 Surface current distribution over the patches of the side-by-side MIMO antenna system at (a) 28
GHz and (b) 38 GHz
Fig. 53 Surface current distribution over patch 1 of the side-by-side MIMO antenna system at (a) 28
GHz and (b) 38 GHz
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
427
Fig. 54 Surface current distribution over the patches of the four-port MIMO antenna system at (a) 28
GHz and (b) 38 GHz
Fig. 55 Surface current distribution over patch 1 of the four-port MIMO antenna system at (a) 28 GHz
and (b) 38 GHz
produces more perfect circular polarization at 37.8 GHz than that produced at 50
GHz. Nevertheless, this MIMO antenna provides polarization diversity in addition to the spatial diversity, where the latter type of diversity is produced owing
to the distance between the elements having the same sense of polarization.
5.3.3 ECC and DG of the Four‑Element MIMO Antenna
The frequency responses of the ECC and DG of the four-element MIMO antenna
are presented in Figs. 48 and 49, respectively, over the operating frequency bands.
It is seen that the ECC is very small (< 10−3) and the DG is almost 10 over both the
frequency bands indicating excellent diversity properties.
13
428
13
Table 2 Comparisons among the perfromance measures of the proposed MIMO antennas and those of other MIMO antennas in previously published papers
Ref
Freq. (GHz)
S11 BW (GHz)
Peak G
(dBi)
ARBW (dB)
Isolation S21 (dB)
ECC
(dB)
[9]
28
10
7.3
2.4
< −31
< 0.5
[10]
28
0.5
7.3
–
− 25
≈0
45
1.8
7.03
No. of elements
Patch dimensions
(mm2)
≈ 10
4
3×3
> 9.99
2
4
4×5
4
4.9 × 5.8
51
0.8
7.2
56
1
8.03
28
0.6
7.38
–
− 30
≈0
≈ 10
38
0.6
8.13
–
-40
≈0
≈ 10
[22]
28
0.4
6.9
–
− 20
0.1
9.9
2
3.15 × 3.15
[23]
28
5
9.5
–
< −40
< 0.01
> 9.9
4
13 × 15
38
2.1
11.5
–
< −40
< 0.01
> 9.9
[24]
28
3.52
7.1
–
− 32
≈0
≈ 10
4
10 × 10
[25]
28
2.4
8.4
–
> −25
≈0
≈ 10
4
4.23 × 2.94
38
2
6.02
–
> −25
≈0
≈ 10
37.8
1.499
7.01
0.708
− 29
4 × 10−7
2 side-by-side
2.9 × 2.9
50
1.855
7.83
0.113
− 41.2
8 × 10
37.8
1.47
7.61
0.776
− 30
5 × 10−8
50
1.86
6.58
0.168
− 29.2
2 × 10−5
37.8
1.474
7.83
0.708
− 29
2 ×10−7
50
1.854
7.9
0.129
− 44
−6
Present work
8 ×10
> 9.99
−6
2 face-to-face
4
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
[21]
DG
(dB)
Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
429
5.4 Surface Current Distribution
The surface current distribution over each patch surface has been calculated for all the
proposed MIMO configurations. In Fig. 50, the surface current over the face-to-face
MIMO antenna system is graphed when port 1 is excited showing very weak coupling
between the two antennas. The direction of the current on patch 1 is calculated and
plotted in Fig. 51 at both operating bands 28 and 38 GHz. It is clear from Fig. 51 that
the antenna exhibits a first-order mode at 28 GHz and second-order mode at 38 GHz.
For the side-by-side MIMO system configuration, the surface current distribution over the elements of the MIMO antennas is shown in Fig. 52 over the two bands
28 and 38 GHz showing very weak coupling at both frequency bands when port 1 is
excited. The direction of the surface current is plotted in Fig. 53 on patch 1 at 28 and
38 GHz. By noticing the current distribution on the main patch, it can be seen that a
single-order mode is obvious at 28 GHz and second-order mode is shown at 38 GHz.
Finally, the surface current distribution is calculated for the four port MIMO
antenna system and demonstrated in Fig. 54 when port 1 is excited, showing low
coupling between elements.
The surface current distribution on patch 1 is illustrated in Fig. 55 using arrows to
show current direction.
6 Comparison with Previous Work
Comparisons between the performance of the proposed MIMO antennas and
that of other MIMO antennas presented in recently published papers are listed
in Table 2. These comparisons show some advantages of the proposed MIMO
antennas relative to those presented in the other publications. The main advantage of the proposed MIMO antennas is that they provide two bands of circular
polarization. Another important advantage over the other published papers is
that the proposed four-element MIMO antenna provides two types of diversity
(spatial and polarization), whereas the other antennas offer only spatial diversity.
The other advantages are the smaller size and high isolation among the multiple ports. However, the main drawback of the proposed MIMO antennas relative
to other published designs is the narrow bandwidth. Nevertheless, the two frequency bands achieved by the proposed MIMO antennas can be considered wide
enough for operation in applications of future wireless communication.
7 Conclusion
A novel CP low-profile printed antenna has been designed to produce circular polarization over two frequency bands around 37.8 and 50GHz. Two-element side-by-side
and face-to-face MIMO antenna configurations have been proposed to attain spatial
diversity. A four-element MIMO antenna has been proposed to achieve both spatial
and polarization diversity at the same time. The proposed dual-band CP single-element, two-element MIMO, and four-element MIMO antennas have been fabricated
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Journal of Infrared, Millimeter, and Terahertz Waves (2024) 45:393–432
for experimental study. Both the numerical and experimental investigations have
shown that the mutual coupling between any two ports of the proposed MIMO
antennas is below −25dB. Also, for any two ports it has been shown that the ECC is
below 1 × 10−7 and the diversity gain is higher than 9.99. The impedance matching
bandwidths (for ||S11 || < −10dB) have been shown to be 1.53 and 1.88 GHz at 37.8
and 50GHz, respectively, and the corresponding 3-dB axial ratio bandwidths have
been shown to be 700 and 130MHz, respectively.
Author Contributions Nada, Rania Performed Simulations Walid, khalid design idea Asmaa performed
fabrication and measurements.
Funding Open access funding provided by The Science, Technology & Innovation Funding Authority
(STDF) in cooperation with The Egyptian Knowledge Bank (EKB).
Data Availability Data sharing not applicable to this article as no datasets were generated or analyzed
during the current study.
Declarations
Competing Interests The authors declare no competing interests.
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License,
which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long
as you give appropriate credit to the original author(s) and the source, provide a link to the Creative
Commons licence, and indicate if changes were made. The images or other third party material in this
article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line
to the material. If material is not included in the article’s Creative Commons licence and your intended
use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/
licenses/by/4.0/.
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Authors and Affiliations
Nada Alaa1 · Rania A. Elsayed1 · Asmaa E. Farahat2 · Khalid F. A. Hussein2 ·
Walid S. El‑Deeb1
* Asmaa E. Farahat
e_asma_e@yahoo.com
Nada Alaa
engnadaalaa@gmail.com
Rania A. Elsayed
en_rania_helika@yahoo.com
Khalid F. A. Hussein
fkhalid@eri.sci.eg
Walid S. El-Deeb
wseldeeb@ucalgary.ca
1
Electronics and Communications Engineering Department, Faculty of Engineering, Zagazig
University, Zagazig, Egypt
2
Microwave Engineering Department, Electronics Research Institute, Cairo 11843, Egypt
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