U.S. patent application number 16/510216 was filed with the patent office on 2021-01-14 for multi-beam yagi-based mimo antenna system.
This patent application is currently assigned to King Fahd University of Petroleum and Minerals. The applicant listed for this patent is King Fahd University of Petroleum and Minerals. Invention is credited to Syed Shahan JEHANGIR, Mohammad S. SHARAWI.
Application Number | 20210013629 16/510216 |
Document ID | / |
Family ID | 1000005300477 |
Filed Date | 2021-01-14 |
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United States Patent
Application |
20210013629 |
Kind Code |
A1 |
SHARAWI; Mohammad S. ; et
al. |
January 14, 2021 |
MULTI-BEAM YAGI-BASED MIMO ANTENNA SYSTEM
Abstract
An orthogonally polarized Yagi-like MIMO antenna system and a
triangular printed wideband Yagi based MIMO antenna system,
respectively, and methods for making the antennas. The orthogonally
polarized Yagi-like MIMO antenna system includes two slot round
loop elements on a top side of a substrate. Each slot round loop
element has two input ports and two slot reflectors. For each slot
round loop element, one of the two input ports is placed
orthogonally to the other input port, and one of the two slot
reflectors is placed orthogonally to the other slot reflector. The
triangular printed wideband Yagi based MIMO antenna system includes
three round loop elements on a top side of a substrate and a
circular reflector on a bottom side of the substrate. Each of the
three round loop elements is placed at 120.degree. with respect to
other two round loop elements and has three parasitic
directors.
Inventors: |
SHARAWI; Mohammad S.;
(Dhahran, SA) ; JEHANGIR; Syed Shahan; (Dhahran,
SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
King Fahd University of Petroleum and Minerals |
Dhahran |
|
SA |
|
|
Assignee: |
King Fahd University of Petroleum
and Minerals
Dhahran
SA
|
Family ID: |
1000005300477 |
Appl. No.: |
16/510216 |
Filed: |
July 12, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01Q 13/0258 20130101;
H04B 7/10 20130101; H01Q 19/20 20130101; H04B 7/0413 20130101; H01Q
21/24 20130101; H01Q 7/00 20130101 |
International
Class: |
H01Q 21/24 20060101
H01Q021/24; H01Q 7/00 20060101 H01Q007/00; H01Q 13/02 20060101
H01Q013/02; H04B 7/10 20060101 H04B007/10; H04B 7/0413 20060101
H04B007/0413 |
Claims
1. An orthogonally polarized Yagi-like MIMO antenna system,
comprising: a substrate having a top side and a bottom side; and at
least one loop element on the top side of the substrate, wherein
one of the at least one loop element has at least two input ports,
wherein for the one of the at least one loop element having at
least two input ports, one of the at least two input ports is
placed in a direction that is orthogonal to another one of the at
least two input ports such that two of the at least two input ports
are placed orthogonally to each other, wherein each of the two
input ports placed orthogonally to each other associates with at
least one reflector, and wherein one of the at least one reflector
associated with the respective input port is placed in a direction
that is opposite to the respective input port.
2. The antenna system of claim 1, wherein, for the one of the at
least one loop element having at least two input ports, one of the
at least two input ports is coupled to the corresponding loop
element through a microstrip line that is on the bottom side of the
substrate.
3-5. (canceled)
6. The antenna system of claim 1, wherein each of the two input
ports placed orthogonally to each other is excited by a guide
wavelength 1.3.lamda.g in a loop resonance mode.
7. A method of constructing an orthogonally polarized Yagi-like
MIMO antenna system, the method comprising: forming at least one
loop element on a top side of a substrate, wherein one of the at
least one loop element has at least two input ports, placing, for
the one of the at least one loop element having at least two input
ports, one of the at least two input ports in a direction that is
orthogonal to another one of the at least two input ports such that
two of the at least two input ports are placed orthogonally to each
other, forming, for each of the two input ports placed orthogonally
to each other, at least one reflector, placing, for each of the two
input ports placed orthogonally to each other, one of the at least
one reflector associated with the respective input port in a
direction that is opposite to the respective input port.
8. The method of claim 7, further comprising: coupling, for the one
of the at least one loop element having at least two input ports,
one of the at least two input ports to the corresponding loop
element through a microstrip line that is on a bottom side of the
substrate.
9-11. (canceled)
12. The method of claim 7, further comprising: exciting the two
input ports placed orthogonally to each other by a guide wavelength
1.3.lamda.g in a loop resonance mode.
13. A triangular printed wideband Yagi based MIMO antenna system,
comprising: a substrate having a top side and a bottom side; three
loop elements on the top side of the substrate, wherein each of the
three loop elements is placed at 120.degree. with respect to other
two loop elements; and at least one reflector, wherein one of the
at least one reflector is placed on the bottom side of the
substrate.
14. The antenna system of claim 13, wherein each of the three loop
elements has two ends, wherein one end of the two ends is coupled
to an input port and the other end of the two ends is coupled to
the one of the at least one reflector that is placed on the bottom
side of the substrate.
15. The antenna system of claim 14, wherein the input port of each
loop element is excited by a guide wavelength 3.5.lamda.g in a loop
resonance mode.
16. The antenna system of claim 13, wherein each of the three loop
elements has at least one parasitic director and one of the at
least one parasitic director is placed on the top side of the
substrate.
17. A method of constructing a triangular printed wideband Yagi
based MIMO antenna system, the method comprising: forming three
loop elements on a top side of a substrate, wherein each of the
three loop elements is placed at 120.degree. with respect to other
two loop elements; and forming at least one reflector, wherein one
of the at least one reflector is placed on a bottom side of the
substrate.
18. The method of claim 17, further comprising: for each of the
three loop elements having two ends, coupling one end of the two
ends to an input port; and coupling the other end of the two ends
to the one of the at least one reflector that is placed on the
bottom side of the substrate.
19. The method of claim 18, further comprising: exciting the input
port of each loop element by a guide wavelength 3.5.lamda.g in a
loop resonance mode.
20. The method of claim 17, further comprising: forming at least
one parasitic director for each of the three loop elements, wherein
one of the at least one parasitic director is placed on the top
side of the substrate.
Description
BACKGROUND
Technical Field
[0001] The present disclosure is directed to antenna systems, and
more particularly, to a wideband compact single layer orthogonally
polarized Yagi-like MIMO antenna system and a wideband multi-beam
sectoral Yagi MIMO antenna system.
Description of Related Arts
[0002] The "background" description provided herein is for the
purpose of generally presenting the context of the disclosure. Work
of the presently named inventors, to the extent it is described in
this background section, as well as aspects of the description
which may not otherwise qualify as prior arts at the time of
filing, are neither expressly or impliedly admitted as prior arts
against the present disclosure.
[0003] The upcoming wireless communication standards demand for
higher data rates and more stable signal quality for various
applications such as browsing, navigation, video streaming,
monitoring, and online gaming. Multiple-input-multiple-output
(MIMO) technology is one of promising techniques for increasing
channel capacity or a data rate within limitations of power levels
and frequency bandwidth, therefore, it has drawn the attention of
many design engineers and researchers.
[0004] Channel capacity or data rate can also be increased by
employing diversity techniques such as spatial, polarization, and
pattern diversity. Polarization diversity is considered useful as
it can provide high isolated channels without increasing the size
of the antenna system. Therefore, it is considered promising for
compact wireless devices. The use of an orthogonally polarized MIMO
antenna inside a compact wireless device can reduce the number of
antennas, for example, a single dual-polarized element can be used
instead of two separate elements, and hence such antenna systems
can reduce the overall size of the antenna system without
compromising other performance metrics.
[0005] Compact MIMO antenna systems are of high demand in the
current 4G as well as in the forthcoming 5G wireless communication
devices because these antenna systems are compatible with various
small form factor handheld wireless devices and hence can be used
for a wide range of applications. By increasing the number of
independent channels and the number of antennas at the transmitter
and the receiver sides, these MIMO antenna systems can provide a
higher data rate, a higher channel capacity, a better coverage, and
an improved transmission quality within a multipath fading
environment. In addition, compact wideband MIMO antenna systems can
cover multiple bands without requiring extra hardware or complex
frequency re-configurability techniques.
[0006] Yagi-Uda antennas are widely known for their end-fire
directional radiation patterns, high gain, high directivity, high
FBR, and ease of fabrication. A classic Yagi-Uda antenna with a
dipole excitation has a narrow bandwidth. Yagi based directional
MIMO antennas can provide better diversity performance in terms of
very low channel correlation between the radiated fields. Such
directional antenna systems are of high interest in the future 5G
technologies.
[0007] However, due to the limited availability of space inside
compact wireless devices, the MIMO antenna systems require
extensive care in the design in terms of current coupling between
the adjacent ports as well as the correlation between the radiated
fields of the multiple elements inside a MIMO antenna system.
[0008] Accordingly, it is one object of the present disclosure to
provide MIMO antennas systems including a wideband compact single
layer orthogonally polarized Yagi-like MIMO antenna system and a
wideband multi-beam sectoral Yagi MIMO antenna system, and methods
for making the MIMO systems.
SUMMARY
[0009] The present disclosure presents a wideband compact Yagi-like
directional MIMO antenna system. A simple dual orthogonal feeding
technique is used to generate orthogonally polarized beams from a
single loop element using microstrip lines. This technique is quite
simple as compared to other complex techniques used in related
technologies to generate cross-polarized beams. The proposed design
is based on a single layer geometry as compared to the 3D
structures used in the related technologies. The common
omnidirectional orthogonal beams obtained from a typical slot
antenna are made directional by using compact multiple reflector
elements, as compared to complex back-lobe reduction techniques
used in the related technologies. A very simple bandwidth
enhancement technique is used as compared to the complex bandwidth
enhancement techniques use in the related technologies.
[0010] The proposed design introduces a wideband single layer
orthogonally polarized MIMO antenna system in a Yagi configuration
with directional beams and a compact size. The design is suitable
for compact handheld and other wireless devices. Due to the feature
of orthogonality, the directional beams are isolated in the far
field and give very low envelope correlation coefficient (ECC)
values less than 0.1 that ensures very good diversity
performance.
[0011] The present disclosure also presents a triangular printed
wideband Yagi-based MIMO antenna system. The proposed Yagi-based
MIMO antenna system introduces the generation of multiple beams
from a single Yagi port excitation for compact wireless access
points, as compared to the multiple beams achieved by using
multiple elements or ports in the related technologies. A simple
concept for splitting the single main end-fire directional beam of
a typical Yagi-Uda antenna into multiple beams is proposed. The
multiple beams from a single element are generated by a careful
excitation in loop resonance mode without compromising the Yagi
performance metrics such as high front-to-back ratio (FBR), gain,
directivity, efficiency, and bandwidth. The proposed Yagi-based
MIMO antenna system has high directional radiation characteristics
with a high FBR, gain, and directivity. It also ensures very good
MIMO performance in terms of port coupling and channel correlation
for compact wireless terminals.
[0012] Aspects of the disclosure also provide methods for
constructing an orthogonally polarized Yagi-like MIMO antenna
system and a triangular printed wideband Yagi-based MIMO antenna
system, respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] A more complete appreciation of this disclosure and many of
the attendant advantages thereof will be readily obtained as the
same becomes better understood by reference to the following
detailed description when considered in connection with the
accompanying drawings, wherein:
[0014] FIG. 1 shows a top view of a wideband compact Yagi-like
directional MIMO antenna system 100 according to an embodiment of
the disclosure;
[0015] FIG. 2 shows a setup of the two wideband compact Yagi-like
directional MIMO antenna systems 100 inside a wireless terminal 200
according to an embodiment of the disclosure;
[0016] FIG. 3A shows the simulated S-parameter curves of the
wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0017] FIG. 3B shows the measured S-parameter curves of the
proposed wideband compact Yagi-like directional MIMO antenna system
100 according to an embodiment of the disclosure;
[0018] FIG. 4A show the simulated realized gain and total radiation
efficiency curves for the input port 1 of the wideband compact
Yagi-like directional MIMO antenna system 100 according to an
embodiment of the disclosure;
[0019] FIG. 4B shows the simulated realized gain and total
radiation efficiency curves for the input port 3 of the wideband
compact Yagi-like directional MIMO antenna system 100 according to
an embodiment of the disclosure;
[0020] FIG. 4C shows the simulated realized gain and total
radiation efficiency curves for the input port 2 of the wideband
compact Yagi-like directional MIMO antenna system 100 according to
an embodiment of the disclosure;
[0021] FIG. 4D shows the simulated realized gain and total
radiation efficiency curves for the input port 4 of the wideband
compact Yagi-like directional MIMO antenna system 100 according to
an embodiment of the disclosure;
[0022] FIG. 5A shows the 3D gain pattern for the input port 1 of
the wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0023] FIG. 5B shows the 3D gain pattern for the input port 2 of
the wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0024] FIG. 5C shows the 3D gain pattern for the input port 3 of
the wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0025] FIG. 5D shows the 3D gain pattern for the input port 4 of
the wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0026] FIG. 6A shows the two dimensional normalized radiation
pattern in the horizontal X-Y plane for the input port 1 of the
wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0027] FIG. 6B shows the two dimensional normalized radiation
pattern in the horizontal X-Y plane for the input port 2 of the
wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0028] FIG. 6C shows the two dimensional normalized radiation
pattern in the horizontal X-Y plane for the input port 3 of the
wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0029] FIG. 6D shows the two dimensional normalized radiation
pattern in the horizontal X-Y plane for the input port 4 of the
wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure;
[0030] FIG. 7 shows a top view of a triangular printed wideband
Yagi based MIMO antenna system 700 according to an embodiment of
the disclosure;
[0031] FIG. 8 shows a setup of two triangular printed wideband Yagi
based MIMO antenna systems 700 inside a wireless terminal 800
according to an embodiment of the disclosure;
[0032] FIG. 9 shows the simulated and measured S-parameters curves
of the triangular printed wideband Yagi based MIMO antenna system
700 according to an embodiment of the disclosure;
[0033] FIG. 10A shows the simulated realized gain and total
radiation efficiency curves for the loop element 701 of the
triangular printed wideband Yagi based MIMO antenna system 700
according to an embodiment of the disclosure;
[0034] FIG. 10B shows the simulated realized gain and total
radiation efficiency curves for the loop element 702 of the
triangular printed wideband Yagi based MIMO antenna system 700
according to an embodiment of the disclosure;
[0035] FIG. 10C shows the simulated realized gain and total
radiation efficiency curves for the loop element 703 of the
triangular printed wideband Yagi based MIMO antenna system 700
according to an embodiment of the disclosure;
[0036] FIG. 11A shows the 3D gain pattern for the loop element 701
of the triangular printed wideband Yagi based MIMO antenna system
700 according to an embodiment of the disclosure;
[0037] FIG. 11B shows the 3D gain pattern for the loop element 702
of the triangular printed wideband Yagi based MIMO antenna system
700 according to an embodiment of the disclosure;
[0038] FIG. 1C shows the 3D gain pattern for the loop element 703
of the triangular printed wideband Yagi based MIMO antenna system
700 according to an embodiment of the disclosure;
[0039] FIG. 12A shows the two dimensional normalized radiation
pattern in the X-Y plane at .theta.=90.degree. for the loop element
701 of the triangular printed wideband Yagi based MIMO antenna
system 700 according to an embodiment of the disclosure;
[0040] FIG. 12B shows the two dimensional normalized radiation
pattern in the X-Y plane at .theta.=90.degree. for the loop element
702 of the triangular printed wideband Yagi based MIMO antenna
system 700 according to an embodiment of the disclosure;
[0041] FIG. 12C shows the two dimensional normalized radiation
pattern in the X-Y plane at .theta.=90.degree. for the loop element
703 of the triangular printed wideband Yagi based MIMO antenna
system 700 according to an embodiment of the disclosure;
[0042] FIG. 12D shows the two dimensional normalized radiation
pattern in the elevation plane computed at respective maximum .phi.
values for the loop elements 701 and 703 of the triangular printed
wideband Yagi based MIMO antenna system 700 according to an
embodiment of the disclosure; and
[0043] FIG. 12E shows the two dimensional normalized radiation
pattern in the elevation plane computed at maximum .phi. value for
the loop element 702 of the triangular printed wideband Yagi based
MIMO antenna system 700 according to an embodiment of the
disclosure.
DETAILED DESCRIPTION
[0044] In the drawings, like reference numerals designate identical
or corresponding parts throughout the several views. Further, as
used herein, the words "a," "an" and the like generally carry a
meaning of "one or more," unless stated otherwise. The drawings are
generally drawn to scale unless specified otherwise or illustrating
schematic structures or flowcharts.
[0045] Furthermore, the terms "approximately," "approximate,"
"about," and similar terms generally refer to ranges that include
the identified value within a margin of 20%, 10%, or preferably 5%,
and any values there between.
[0046] Aspects of this disclosure are directed to a system, device,
and method for multi-beam Yagi-based MIMO antenna systems. The
generalized concept of the present disclosure, with suitable
modifications, is applicable to various antenna systems, devices,
methods for wireless terminals. The present disclosure will be
described in detail herein with reference to the exemplary
embodiments of a wideband compact Yagi-like directional MIMO
antenna system and a triangular printed wideband Yagi based MIMO
antenna system, although the disclosure is not necessarily limited
to such topologies.
[0047] This disclosure exploits the features of the loop excitation
in a Yagi fashion to generate orthogonally polarized beams. A dual
feeding technique can be used to generate orthogonally polarized
beams from a single loop element. The proposed technique is simple
as compared to other complex orthogonally polarized techniques
presented in related technologies. The bandwidth can be increased
by exciting a certain guide wavelength (e.g., 1.3.lamda.g) in loop
resonance mode. This bandwidth enhancement technique is also very
simple as compared to the complex bandwidth enhancement techniques
presented in other technologies. The omnidirectional orthogonal
beams of the single loop element can be made directional by using
compact reflector elements such as a complementary slot reflector
(CSR) unlike the aforementioned complex back-lobe reduction
techniques that are commonly used in related technologies. The
present disclosure also introduces a single layer orthogonally
polarized MIMO antenna system in a Yagi configuration with
directional beams, wider bandwidth, and compact size. Due to the
directional orthogonal beams, the design has a very low correlation
between the fields and ensures very good diversity performance. The
proposed design is suitable for WiMAX integrated wireless devices,
wireless modems, and other compact handheld devices and smart
phones. The details of the proposed antenna system will be
described with corresponding figures.
[0048] According to embodiments of the disclosure, a proposed
wideband compact Yagi-like directional MIMO antenna system includes
at least one loop element.
[0049] FIG. 1 shows a top view of a proposed wideband compact
Yagi-like directional MIMO antenna system 100 according to an
embodiment of the disclosure. The antenna system 100 includes a
substrate 130 and two slot round loop elements 125 and 127. The
substrate 130 has a top side and a bottom side. The two slot round
loop elements 125 and 127 are placed on the top side of the
substrate and separated by a certain distance. Each slot round loop
elements has a radius 115 and a thickness 117. In the same or
another embodiment, the radius 115 is 9.3 mm and the thickness is
1.2 mm.
[0050] According to embodiments of the disclosure, in a proposed
wideband compact Yagi-like directional MIMO antenna system, one of
the at least one loop element can have at least two input ports and
one of the at least two input ports can be placed in a direction
orthogonal to another one of the at least two input ports.
[0051] Reference to FIG. 1, two input ports 120 and 121 are for the
slot round loop element 125, and two input ports 122 and 123 are
for the slot round loop element 127. For each slot round loop
element, one input port is placed in a direction orthogonal to the
other input port to generate orthogonally polarized beams from the
single slot round loop element. For example, for the slot round
loop element 125, the input port 120 is placed orthogonally to the
other input port 121. It is noted that the two ports have to be at
90.degree. degrees with respect to each other to achieve orthogonal
beams that are uncorrelated in the far-field. However, for any
other applications where orthogonality is not of the utmost
importance, the relative placement between the ports can be changed
keeping in view that the position of the CSR elements 107 and 108
(or 109 and 110) have to be optimized accordingly. Each input port
connects the corresponding slot round loop element through a
microstrip line on the back side of the antenna system 100. Each
microstrip line has a length 119 and a width 116. In the same or
another embodiment, the length 119 can be 9 mm and the width 116
can be 1.9 mm.
[0052] According to embodiments of the disclosure, in a proposed
wideband compact Yagi-like directional MIMO antenna system, two
input ports placed orthogonally to each other can be excited by a
certain guide wavelength (preferably 1.1-1.5.lamda.g) in a loop
resonance mode.
[0053] Still reference to FIG. 1, each input port is excited by a
guide wavelength 1.3.lamda.g in a loop resonance mode through a SMA
connector to increase the bandwidth of the antenna system 100. For
the input ports 120 and 122, the SMA connectors are attached at an
edge of the substrate 130. For the input ports 121 and 123, the SMA
connectors are attached through two vias 124.
[0054] According to embodiments of the disclosure, in a proposed
wideband compact Yagi-like directional MIMO antenna system, each of
the two input ports placed orthogonally to each other can associate
with at least one reflector element.
[0055] Still reference to FIG. 1, each slot round loop element has
two compact complementary slot reflector (CSR) elements and each
CSR element corresponds to one of the two input ports placed
orthogonally to each other. For example, the slot round loop
element 125 has a CSR element 107 for the input port 121 and a CSR
element 108 for the input port 120, and the slot round loop element
127 has a CSR element 109 for the input port 123 and a CSR element
110 for the input port 122. Each CSR element has a length 104 and a
width 111. In the same or another embodiment, the length 104 can be
14 mm and the width 111 can be 9.2 mm. In addition, in the
embodiment as shown in FIG. 1, the CSR elements are placed on the
top side of the substrate 130.
[0056] According to embodiments of the disclosure, in a proposed
wideband compact Yagi-like directional MIMO antenna system, for one
of the two input ports placed orthogonally to each other, one of
the at least one reflector element associated with the input port
can be placed in a direction opposite to the input port. Since one
of the two input ports can be placed orthogonally to the other one
of the two input ports, the reflector element opposite to the one
of the two input ports can also be placed orthogonally to the
reflector element opposite to the other one of the two input
ports.
[0057] Still reference to FIG. 1, each CSR element is placed
opposite to the input port associated with the CSR element. For
example, the CSR element 107 is placed opposite to the input port
121. Accordingly, for each slot round loop element, one CSR element
is placed orthogonally to the other CSR element. For example, for
the slot round loop element 125, the CSR element 107 is placed
orthogonally to the other CSR element 108. By placing two CSR
elements orthogonally around the slot round loop element, the
omnidirectional orthogonal beams of the slot round loop element are
made directional.
[0058] According to embodiments of the disclosure, in a proposed
wideband compact Yagi-like directional MIMO antenna system, the
substrate of the proposed antenna system can be realized by a
single layer or a multi-layer laminate with low loss and good RF
performance.
[0059] Still reference to FIG. 1, the substrate 130 of the antenna
system 100 is realized by a single layer Roger substrate RO4350.
The Roger substrate RO4350 can have a thickness of 0.76 mm, a
dielectric constant of 3.48, and a loss tangent of 0.004. The
substrate 130 has a length 101 and a width 102. In the same or
another embodiment, the length 101 can be 90 mm and the width 102
can be 35 mm. In addition, other dimensions, such as the location
and spacing of these CSR elements, can be fully optimized to
achieve directional horizontal and vertical polarized beams. In the
same or another embodiment, other dimensions can be 103 (8.5 mm),
105 (12.5 mm), 106 (36 mm), 126 (13.5 mm), 114 (20 mm), and 118
(4.5 mm).
[0060] In an embodiment, a plurality of the proposed wideband
compact Yagi-like directional MIMO antenna systems can be placed
together inside a wireless device to achieve better performance.
For example, FIG. 2 shows a setup of the two proposed wideband
compact Yagi-like directional MIMO antenna systems 100 inside a
wireless terminal 200.
[0061] It is noted that the geometry parameters of a proposed
wideband compact Yagi-like directional MIMO antenna system are
frequency dependent. Therefore, the geometry parameters can vary as
an operating frequency of the proposed antenna system changes. That
is, the exemplary geometry parameters of the embodiment as shown in
the FIG. 1 may vary in other embodiments. The results shown in
FIGS. 3-6 are based on the geometry parameters of the embodiment as
shown in the FIG. 1. However, the results may vary as the operating
frequency of the proposed antenna system changes in other
embodiments.
[0062] FIGS. 3A and 3B show the simulated and measured S-parameter
curves of the proposed wideband compact Yagi-like directional MIMO
antenna system 100, respectively, according to an embodiment of the
disclosure. The design parameters of the embodiment as shown in
FIG. 1 are modeled and simulated in HFSS.TM.. In FIG. 3B, it can be
seen that the proposed antenna system 100 has a measured bandwidth
of 620 MHz (3.26-3.88 GHz) when a return loss (e.g., S.sub.1,
S.sub.22, S.sub.33, and S.sub.44) is -10 dB. In addition, it can
also be seen that the minimum return loss is below -30 dB, the
minimum isolation between input ports 1 and 2 (S.sub.12|S.sub.21)
is around -10 dB, the minimum isolation between input ports 3 and 4
(S.sub.34|S.sub.43) is around 10 dB, the minimum isolation between
input ports 2 and 4 (S.sub.24|S.sub.42) is around -15 dB, the
minimum isolation between input ports 1 and 3 (S.sub.13|S.sub.31)
is around -20 dB, the minimum isolation between input ports 1 and 4
(S.sub.14|S.sub.41) is around -20 dB, and the minimum isolation
between input ports 2 and 3 (S.sub.23|S.sub.32) is around -20 dB.
Overall, a good agreement between the simulated and measured
results is observed.
[0063] FIGS. 4A-4D show the simulated realized gain and total
radiation efficiency curves of the proposed wideband compact
Yagi-like directional MIMO antenna system 100 according to an
embodiment of the disclosure. The design parameters of the
embodiment as shown in FIG. 1 are modeled and simulated in
HFSS.TM.. FIGS. 4A and 4B show the simulated realized gain and
total radiation efficiency curves for the input ports 1 and 3,
respectively. FIGS. 4C and 4D show the simulated realized gain and
total radiation efficiency curves for the input ports 2 and 4,
respectively. In FIGS. 4A and 4B, it can be seen that the proposed
antenna system 100 has a maximum gain of more than 3.5 dBi for the
input ports 1 and 3 at the center frequency of operation (3.6 GHz).
The total radiation efficiency has a minimum of 70% for Ports 1
& 3 and can reaches to 90% at 3.75 GHz for Ports 1 & 3.
[0064] FIGS. 5A-5D show the 3D gain patterns of the proposed
wideband compact Yagi-like directional MIMO antenna system 100
according to an embodiment of the disclosure. The design parameters
of the embodiment as shown in FIG. 1 are modeled and simulated in
HFSS.TM.. The operating frequency in this simulation is set to 3.6
GHz. FIGS. 5A and 5C show the 3D gain patterns for the input ports
1 and 3, respectively, while FIGS. 5B and 5D show the 3D gain
patterns for the input ports 2 and 4, respectively. It can be seen
that the maximums of these patterns are tilted towards different
directions and are apart from each other, indicating very low
correlation between the radiated fields for these ports. For
example, the maximum gain of the input port 1 tilts to 90.degree.
while the maximum gain of the input 3 tilts to 270.degree..
[0065] FIGS. 6A-6D show the two dimensional normalized radiation
patterns in the horizontal X-Y plane of the proposed wideband
compact Yagi-like directional MIMO antenna system 100 according to
an embodiment of the disclosure. The design parameters of the
embodiment as shown in FIG. 1 are modeled and simulated in
HFSS.TM.. The operating frequency in this simulation is set to 3.6
GHz. FIGS. 6A and 6C show the normalized radiation patterns for the
input ports 1 and 3, respectively. It can be seen that the maximums
of the beams are apart from each other by almost 150.degree. for
the input ports 1 and 3. Similarly, for the input ports 2 and 4,
the maximums of the beams are separated by 90.degree. as shown in
FIGS. 6B and 6D, respectively. For all the input ports, the
maximums of the beams are separated by a minimum of 30.degree..
This ensures that the orthogonal beams of the proposed MIMO antenna
system are highly uncorrelated, so that a good MIMO performance can
be obtained.
[0066] In an embodiment, to evaluate the diversity performance of
the proposed antenna system 100, the ECC values are computed for
all the ports from the measured 3D radiated fields. It is found
that the maximum ECC value is 0.0928 between all the ports of the
antenna system 100 and is below a standard ECC value of 0.5 that is
defined for a good MIMO performance. The minimum FBR of the
proposed MIMO antenna system 100 is more than 7 dB while the
minimum FBR reaches to 13.5 dB at 3.75 GHz, which also ensures high
directional radiation performance.
[0067] According to embodiments of the disclosure, a method of
constructing an orthogonally polarized Yagi-like MIMO antenna
system is presented. The method can form at least one loop element
on a top side of a substrate and one of the at least one loop
element can have at least two input ports. The method can couple
one of the at least two input ports to the corresponding loop
element through a microstrip line that is on a bottom side of the
substrate. The method can further place one of the at least two
input ports in a direction that is orthogonal to another one of the
at least two input ports. The method can excite an input port with
a certain guide wavelength such as 1.3.lamda.g in a loop resonance
mode. For each of the two input ports placed orthogonally to each
other, the method can place one reflector element in a direction
that is opposite to the respective input port, such that the
reflector element opposite to one input port is placed orthogonally
to the reflector element opposite to the other input port. The
method can place the two slot reflector on the top side of the
substrate.
[0068] The present disclosure also presents a triangular printed
wideband Yagi based MIMO antenna system. The triangular printed
wideband Yagi based MIMO antenna system can introduce the
generation of multiple beams from a single Yagi port excitation,
unlike the designs in related technologies, where multiple beams
are achieved by using multiple elements or ports. The triangular
printed wideband Yagi based MIMO antenna system of the present
disclosure can split the single main end-fire directional beam of a
typical Yagi-Uda antenna into multiple beams. The multiple beams
from a single element can be generated by exciting a certain guide
wavelength in a loop resonance mode without compromising the Yagi
performance metrics such as FBR, gain, directivity, efficiency, and
bandwidth. The triangular printed wideband Yagi based MIMO antenna
system has high directional radiation characteristics with a high
FBR, high gain, and high directivity. This ensures very good MIMO
performance in terms of port coupling and channel correlation for
compact wireless terminals.
[0069] The triangular printed wideband Yagi based MIMO antenna
system can be a single layer antenna with multi-beam elements as
compared to the multiple layer non-Yagi related MIMO antenna
systems that covers different sectors by employing complex 3D
structures in related technologies. The multiple beams can be
meticulously optimized such that the adjacent beams do not
interfere and degrade the performance of the neighboring beams. The
triangular printed wideband Yagi based MIMO antenna system can use
a simple microstrip line feeding as well as a simple and compact
ground plane reflector element to achieve high FBR as compared to
the related technologies where complex feeding and back-lobe
reduction techniques are used. The triangular printed wideband Yagi
based MIMO antenna system has a compact size, wide bandwidth, high
port isolation, and low field correlation with high gain and
efficiency values. The details of the triangular printed wideband
Yagi based MIMO antenna system will be described with corresponding
figures.
[0070] According to embodiments of the disclosure, a proposed
triangular printed wideband Yagi based MIMO antenna system can
include three loop elements on the same side of a substrate. The
design is targeted for MIMO sectoral applications. Each of the
three loop elements is placed at a certain angle with respect to
other two loop elements.
[0071] FIG. 7 shows a top view of a proposed triangular printed
wideband Yagi based MIMO antenna system 700 according to an
embodiment of the disclosure. The MIMO antenna system 700 includes
a substrate 730 and three round loop elements: 701, 702, and 703.
The substrate 730 has a top side and a bottom side. The three round
loop elements are placed on the stop side of the substrate 730 at
an angle 715 with respect to each other. Each round loop element
has a thickness 709 and a radius 707. In the same or another
embodiment, the angle 715 can be 120.degree., the thickness 709 can
be 1.8 mm, and the radius 707 can be 12.85 mm.
[0072] According to embodiments of the disclosure, in a proposed
triangular printed wideband Yagi based MIMO antenna system, each of
the three loop elements can associate with at least one parasitic
director.
[0073] Reference to FIG. 7, each round loop element of the proposed
antenna system 700 associates with three parasitic directors 721 on
the top side of the substrate 730. The parasitic directors of each
round loop element can increase the radiation pattern in a given
direction. In the same or another embodiment, each parasitic
director can have a length 706 of 14.4 mm. The spacing 705 between
the parasitic director and the corresponding round loop element can
be 3.35 mm.
[0074] According to embodiments of the disclosure, a proposed
triangular printed wideband Yagi based MIMO antenna system can
include at least one reflector, such that one end of a loop element
of the proposed antenna system can couple to one of the at least
one reflector.
[0075] Still reference to FIG. 7, the proposed antenna system 700
includes a circular parasitic reflector 720 (i.e., a ground plane)
on the bottom side of the substrate 730. In the same or another
embodiment, the spacing 716 between a round loop element and the
circular reflector 720 can be 3.2 mm.
[0076] Each round loop element has two ends, where one end of the
two ends is coupled to an input port and the other end of the two
ends is coupled to the circular reflector 720. For example, for the
round loop element 701, one end 719 is coupled to the corresponding
input port through an SMA connector through a via in the ground
plane, and the other end 718 is shorted to the circular reflector
720 (i.e., the ground plane) through a via. In the same or another
embodiment, a length 713 and a thickness 710 of the long leg can be
11 mm and 1.6 mm, respectively, and a length 714 and a thickness
711 of the short leg can be 3.6 mm and 1.5 mm, respectively. The
spacing 708 between the two loop legs can be 0.9 mm.
[0077] According to embodiments of the disclosure, in a proposed
triangular printed wideband Yagi based MIMO antenna system, the
substrate of the proposed antenna system can be realized by a
single layer or a multi-layer laminate with low loss and good RF
performance.
[0078] Still reference to FIG. 7, the substrate of the antenna
system 700 can be realized by a Roger substrate RO4350. The Roger
substrate RO4350 can have a thickness of 0.76 mm, a dielectric
constant of 3.48, and a loss tangent of 0.004. In addition, other
dimensions, such as a total radius 717 of the proposed antenna
system 700 and a spacing 704 between the parasitic director and
outer surface of the antenna system 700 can be fully optimized to
achieve high directional radiation performance. In the same or
another embodiment, the total radius 717 of the antenna system 700
can be 60 mm and the spacing 704 between the parasitic director and
outer surface of the antenna system 700 can be 8.2 mm.
[0079] In an embodiment, a plurality of the proposed triangular
printed wideband Yagi based MIMO antenna systems can be placed
together inside a wireless device to achieve better performance.
For example, a setup of two proposed triangular printed wideband
Yagi based MIMO antenna systems 700 inside a wireless terminal 800
is shown in FIG. 8.
[0080] It is noted that the geometry parameters of a proposed
triangular printed wideband Yagi based MIMO antenna system are
frequency dependent. Therefore, the geometry parameters can vary as
an operating frequency of the proposed antenna system changes. That
is, the exemplary geometry parameters of the embodiment as shown in
the FIG. 7 may vary in other embodiments. The results shown in
FIGS. 9-12 are based on the geometry parameters of the embodiment
as shown in the FIG. 7. However, the results may vary as the
operating frequency of the proposed antenna system changes in other
embodiments.
[0081] FIG. 9 shows the simulated and measured S-parameters curves
of the proposed MIMO antenna system 700 according to an embodiment
of the disclosure. The design parameters of the embodiment as shown
in FIG. 7 are modeled and simulated in HFSS.TM.. The proposed MIMO
antenna system 700 has a measured bandwidth of 950 MHz (5.4-6.35
GHz) when a return loss (e.g., S.sub.11, S.sub.22, and S.sub.33) is
-10 dB. The minimum return loss is around -26 dB. The proposed MIMO
antenna system 700 has a high measured isolation that is greater
than 28 dB within the entire band of operation between any two of
the three ports. FIG. 9 indicates that the simulation and
measurement results are in good agreement.
[0082] FIGS. 10A-10C show the simulated realized gain and total
radiation efficiency curves of the proposed MIMO antenna system 700
according to an embodiment of the disclosure. The design parameters
of the embodiment as shown in FIG. 7 are modeled and simulated in
HFSS.TM.. FIGS. 10A, 10B, and 10C show these curves for the round
loop elements 701, 702, and 703, respectively. The antenna system
700 has a maximum gain of 5 dBi and high radiation efficiency of
around 95% at the center frequency of operation (5.875 GHz).
[0083] FIGS. 11A-11C show the 3D gain patterns of the proposed MIMO
antenna system 700 according to an embodiment of the disclosure.
The design parameters of the embodiment as shown in FIG. 7 are
modeled and simulated in HFSS.TM.. The operating frequency is set
to 5.8 GHz. FIGS. 11A, 11B, and 11C show these patterns for the
round loop elements 701, 702, and 703, respectively. It can be seen
that the beams of the three elements are pointing towards different
directions and are apart from each other by 120.degree.. Therefore,
it is indicated that the patterns of the MIMO antenna system are
highly uncorrelated.
[0084] FIGS. 12A-12E show the two dimensional normalized radiation
patterns of the proposed MIMO antenna system 700 according to an
embodiment of the disclosure. The design parameters of the
embodiment as shown in FIG. 7 are modeled and simulated in
HFSS.TM.. The operating frequency is set to 5.8 GHz. FIGS. 12A,
12B, and 12C show these patterns for the round loop elements 701,
702, and 703, respectively, in the azimuth (X-Y) plane at
.theta.=90.degree., while FIG. 12D shows these patterns for the
round loop elements 701 and 703 in the elevation plane computed at
their respective maximum .phi. values, and 12E show these patterns
for the loop element 702 in the elevation plane computed at its
maximum .phi. values. As shown in FIG. 12A-12C, the main middle
beams of the round loop elements 701, 702, and 703 point to around
345.degree., 105.degree., and 210.degree., respectively. Therefore,
it can be seen that the main middle beam of each loop element is
apart from the main middle beams of the two adjacent round loop
elements by almost 120.degree. due to the geometry configuration of
the antenna system 700. In addition, for each round loop element,
the maximums of the two adjacent beams are separated from each
other by at least 70.degree.. For example, the respective maximums
of the three beams of the round loop element 703 point to around
135.degree., 210.degree., and 295.degree., respectively, as shown
in FIG. 12C. Therefore, it can be seen that the multiple beams of
each round loop element do not affect the performance of adjacent
beams. The minimum FBR of the proposed MIMO antenna system 700 in
both planes is 14 dB at 5.8 GHz, which also ensures high
directional radiation performance. The FBR is also calculated at
other frequencies and it is found that the minimum value is 14
dB.
[0085] According to embodiments of the disclosure, a method of
constructing a triangular printed wideband Yagi based MIMO antenna
system is presented. The method can form three loop elements on a
top side of a substrate and each of the three loop elements can be
placed at a certain angle such as 120.degree. with respect to other
two loop elements. The method can further form at least one
reflector and place one of the at least one reflector on a bottom
side of the substrate. Each of the three round loop elements can
have two ends. The method can couple one end of the two ends to an
input port and couple the other end of the two ends to one of the
at least one circular reflector that is placed on the bottom side
of the substrate. The method can excite an input port with a
certain guide wavelength (preferably 3.1-3.9.lamda.g) such as
3.5.lamda.g in a loop resonance mode. In addition, for each loop
element, the method can form at least one parasitic director on the
top side of the substrate.
[0086] While the circuit topologies, the control strategies, and
the methods illustrated above apply to a wideband compact Yagi-like
directional MIMO antenna system and a triangular printed wideband
Yagi based MIMO antenna system, all of these can be adapted to
other multi-beam MIMO antenna systems without deviating from the
scope of the present disclosure.
[0087] A number of implementations have been described.
Nevertheless, it will be understood that various modifications may
be made without departing from the spirit and scope of this
disclosure. For example, preferable results may be achieved if the
steps of the disclosed techniques were performed in a different
sequence, if components in the disclosed systems were combined in a
different manner, or if the components were replaced or
supplemented by other components. The functions, processes and
algorithms described herein may be performed in hardware or
software executed by hardware, including computer processors and/or
programmable circuits configured to execute program code and/or
computer instructions to execute the functions, processes and
algorithms described herein. Additionally, an implementation may be
performed on modules or hardware not identical to those described.
Accordingly, other implementations are within the scope that may be
claimed.
* * * * *