Post on 28-Jan-2020
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Transparent Antennas: From 2D to 3D
Transparent Antennas: From 2D to 3D
K. W. LeungState Key Laboratory of Millimeter Waves &
Department of Electronic Engineering,City University of Hong Kong
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I. 2D transparent antenna
Meshed conductor Transparent conductor
II. 3D transparent antenna
Optical application Decoration Light cover
Outline
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I. 2D Transparent AntennaI. 2D Transparent Antenna
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Based on the theory of microstrip antenna.
Meshed conductors or transparentconductors on acrylic or glass substrates.
Integrated with planar clear substratessuch as window glass or with solar cells.
2D transparent antenna
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Transparent Antenna UsingMeshed Conductor
Transparent Antenna UsingMeshed Conductor
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Working principle: optical signal passthrough the opening, microwave signaltransmitted or received by conductor.
Not fully transparent.
Meshed conductor
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Proposed by Wu & Ito in 1992.Microstrip antenna & ground plane made with parallel wiresWires: silver-plated copper of cross section 0.2 0.1 mm2
Glass substrate.
Early transparent antenna
M. S. Wu and K. Ito, “Basic study on see-through microstrip antennas constructed on a window glass,” in Proc.IEEE AP-S Int. Symp., pp. 499–502, 1992. 8
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Measured return loss vs. frequency
Measured bandwidth (VSWR < 2): 1.5%.
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Measured radiation patterns
Broadside radiation patterns obtained for both planes.Front-to-back ratio ~ 9 dB.Cross polarization level < -13 dB in the boresight direction ( = 0).
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Measured gain
Measured gain at 925 MHz: ~ 2.5 dBd (relative gain tostandard dipole antenna: 2.15 dBi).
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Transparent Antenna Using Transparent Conductor
Transparent Antenna Using Transparent Conductor
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Proposed by Simons & Lee in 1997.(a) Microstrip Line Feed: a=53mm, b=37mm, d=8 mm, w=2 mm (6 GHz).(b) Probe Feed: a = 9 mm, b = 7 mm (19 GHz).
(a) (b)
The first transparent antennas using conductive film
R. N. Simons and R. Q. Lee, “Feasibility Study of Optically Transparent Microstrip PatchAntenna”,NASA Technical Memorandum, 1997. 21
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Transparent conductive materials (TCO)
TCO found since the 1950s
Quickly developed over the past decades.
Products include paper-thin LCD, plasma, touch screen monitors on ATMS, etc.
Common TCO’s:Indium tin oxide (ITO), silver coated polyester film (AgHT) and fluorine-doped tin oxide (FTO).
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ITO
AgHT
FTO
Transparent conductive materials (TCO)
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The surface resistance is given by:
Rs=1/(Ne qμe t)
where μe is the electron mobility, Ne is the free electron density,q is electron charge, andt is the film thickness.
Resistance of ITO film
T.Yasin, R. Baktur, and C. Furse, "A study on the efficiency of transparent patch antennas designed fromconductive oxide films," IEEE International Symposium on Antennas and Propagation, pp3085 - 3087, 2011.24
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Effect of electron mobility on radiation efficiency
Given an electron mobility, higher transparency leads to lower efficiency.
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Transparent monopole antenna
The trapezoidal radiator is made of ITO film.The ground is made of copper.
Ning Guan, Hirotaka Furuya, David Delaune, and Koichi Ito, “Antennas Made of Transparent ConductiveFilms, PIERS.Vol. 4 No. 1 2008 pp: 116-120. 28
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Measured radiation patterns
The resistance does not affect the radiation pattern significantly.
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Method of improving the efficiency
H. J. Song, T. Y. Hsu, D. F. Sievenpiper, H. P. Hsu, J. Schaffner and E. Yasan, “A Method for Improving theEfficiency of Transparent Film Antennas”, IEEE Antennas and Wireless Propagation Letters, Vol.7, pp.753-756,2008. 33
Symmetrical half structure of coplanar waveguide fed patch antenna
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Surface current distribution at 2.2 GHz
To improve efficiency,
apply a highly conductivecoating or metallization inthe form of a very narrowstrip.
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Simulated efficiency for different strip widths
Copper patch has the highest efficiency as expectedAgHT-4 film (4.5 /sq, = 2.2 105 S/m) without adding silver strip
38% efficiencyAgHT-4 film with silver strip (1-mm strip width) along the edge:
68% efficiency equivalent to a conductor patch with 0.4 /square
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II. 3D Transparent AntennaII. 3D Transparent Antenna
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Based on theory of dielectric resonator antenna (DRA).
3D transparent antenna
• The DRA is an antenna that makes use of a radiating mode of a dielectric resonator (DR).
• It is a 3-dimensional device of any shape,e.g., hemispherical, cylindrical, rectangular,triangular, etc.
• Resonance frequency determined by the its dimensions and dielectric constant r.
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Some DRs :
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Glass is used as the dielectric material
Well-known fact:Refractive index of glass: n ~ 1.5 r ~ 2.25
This r is too low for designs of DRAs
But something has been overlooked …..
3D transparent antenna
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n ~ 1.5 (r ~ 2.25) is for optical frequency only r can be very different at microwave frequency
Dielectric constant of the glass DRA
1 2 3 4 5 60
2
4
6
8
Frequency (GHz)
Dielectric constant
K9 glassTeflonAir
Measured dielectric constants of air, Teflon, and K9 glassby using Agilent 85070D Dielectric Probe Kit.
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K-9 Glass
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Transparent Dielectric Resonator Antennas for Optical Applications
Transparent Dielectric Resonator Antennas for Optical Applications
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Hemispherical transparent DRA
Solar Cell
r, n
TransparentHemispherical DRA
Ground Plane
R
d
x
z
g
ConformalExcitation Strip
Coaxial Probe
l s
Substrate (rs)
Transparent Hemispherical DRA
x
y
ws
ConformalExcitation Strip
GroundedSubstrate
R
Rc
Solar Cell
Conformal strip for exciting the transparent DRA made of Pyrex.DRA serves as light-focusing lens for a solar cell panel.Underlaid solar cell panel to save the footprint.DRA provides protection for the solar cell panel.
E. H. Lim and K. W. Leung, “Transparent dielectric resonator antennas for optical applications,” IEEETrans. Antennas Propagat., vol. 58, No. 4, pp. 1054-1059, April 2010. 39
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Solar cell r = 1.5, tan = 10 from the paper shown below
Prototype
Design parametersR = 28 mm, r = 7, g = 2 mm, d = 1.57 mm, ws = 12 mm, and ls =19 mm.
30J. Dheepa, R. Sathyamoorthy, A. Subbarayan, S. Velumani, P. J. Sebastian, and R. Perez, “Dielectric properties ofvacuum deposited Bi2Te3 thin films,” Solar Energy Mater. Solar Cells, vol. 88, no. 2, pp. 187–198, Jul. 2005.39
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Prototype
3139
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1.6 1.8 2 2.2 2.4-40
-30
-20
-10
0
Frequency (GHz)
HFSS SimulationExperiment
1.6 1.8 2 2.2-50
0
50
100
Frequency (GHz)
Inpu
t Im
peda
nce
|S11| (dB)
Simulated and measured S11 and input impedances
Resonance frequency: Measured 1.94 GHz Simulated 1.89 GHz (2.65% error)
Impedance bandwidth: measured 16.5%, simulated 22.8%
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1.6 1.8 2 2.2 2.4-6
-3
0
3
6
9
Frequency (GHz)
Gain (dBi)
Measured antenna gain
The gain is ~5.3dBi around the resonance.
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-40 -30 -20 -10 0 -40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
30
150
60
120
90 90
120
60
150
30
180
o o
o o
o o
o o
o oo
dB
co-polcross-pol cross-pol
E-plane H-plane(a) (b)
Simulation 1.89GHzExperiment 1.94GHz
(x < 0, = 180 )o (y < 0, = 270 )o (y > 0, = 90 )o(x > 0, = 0 )o
0o 0o
Simulated and measured radiation patterns
Measured (1.87 GHz), simulated (1.92 GHz).In the boresight direction, co-pol fields > X-pol fields bymore than 22dB.
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Prism
A rgonB lue Laser
Parallel L ight
Solar C ell
D R A
400m m 420m m
R otator
Experimental setup for the optical part
Parallel light beams generated by a laser source.(wavelength 488 nm, light power 130 mW)DRA placed on a rotator.Solar cell output measured at different illumination angles ().
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Voltage (V)
0 10 20 30 40 50 60 70 80 900
0.5
1
1.5
2
2.5
Illumination Angle
With hemispherical DRAWithout hemispherical DRA
Current (mA)
0 10 20 30 40 50 60 70 80 900
0.5
1
1.5
2
2.5
Illumination Angle
With hemispherical DRAWithout hemispherical DRA
Output voltages and currents of solar panel with and without the hemispherical DRA: Rc = 15mm.
Larger outputs < 30o because of DRA focusing effect.At = 0o, output voltage and current increased by 13.5%
and 27.2%, respectively.
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Non-focusing transparent DRA
Solar Cell
r, n
TransparentRectangular DRA
Ground Plane
W
d
x
z
g
Excitation Strip
Coaxial Probe
l s
Substrate (rs)H
TransparentRectangular DRA
y
x
ws
Excitation Strip
W
W
Rc
GroundedSubstrate
Solar Cell
Transparent rectangular DRA is used.
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1.6 1.8 2 2.2 2.4-40
-30
-20
-10
0
Frequency (GHz)
HFSS SimulationExperiment
1.6 1.8 2 2.2-40
0
40
80
Frequency (GHz)In
put I
mpe
danc
e
|S11| (dB)
Simulated and measured S11 and input impedances
Resonant frequency: Measured 1.91GHzSimulated 1.86GHz (error 2.7%)
Impedance bandwidth: Measured 17.6 %, Simulated 15.8%.
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1.6 1.8 2 2.2 2.4
-6
-3
0
3
6
Frequency (GHz)
Gain (dBi)
Measured antenna gain
Measured antenna gain: ~4 dBi at resonance.
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-40 -30 -20 -10 0 -40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
30
150
60
120
90 90
120
60
150
30
180
o o
o o
o o
o o
o oo
dB
co-polcross-pol cross-pol
E-plane H-plane(a) (b)
Simulation 1.86GHzExperiment 1.91GHz
(x < 0, = 180 )o (y < 0, = 270 )o (y > 0, = 90 )o(x > 0, = 0 )o
0o 0o
Simulated and measured radiation patterns
Measured (1.91 GHz), simulated (1.86 GHz).In the boresight direction, co-pol fields > X-pol fields by more than 25 dB.
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Voltage (V) Current (mA)
0 10 20 30 40 50 60 70 80 900
0.5
1
1.5
2
2.5
0
0.4
0.8
1.2
1.6
2
Illumination Angle
With rectangular DRWithout rectangular DR
Output voltages and currents of solar panel withand without the rectangular DRA: Rc = 15mm.
The rectangular DRA does not increase the solar cell outputs No focusing effect.
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Transparent Dielectric Resonator Antennas Used as Decorations
Transparent Dielectric Resonator Antennas Used as Decorations
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DRA can be of any shape. Can it be made like a swan?
Yes!
It leads to probably the most beautiful antenna in the world …….
44 K. W. Leung, E. H. Lim and X. S. Fang, "Dielectric resonator antennas: From the basic to the aesthetic,"Proceedings of the IEEE, vol. 100, no. 7, pp2181-2193, Jul. 2012.
Broadside Transparent Swan-DRA (K9 glass)
Bought from commercial market, not tailor-made
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Advantages of aesthetic transparent DRA
Home or office decorations
Save space
Turn antennas into artworks
Excellent invisible antennas
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27
103
115
13
57
13 34
33
z
x
z
y
3
133
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Antenna Configuration
Side view Front view
Dimension in mm
Substrate: εrs= 2.33, thickness 1.57 mm, size 1414 cm2
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Antenna Configuration
2
32 130
51
140
z
-y10
y
x
140
Back view Top view
Dimension in mm
Coupling slot: at center of swan length (130 mm) Slot size: length 32 mm, width 2 mm 47
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Measured reflection coefficient
Resonance frequency: 1.83 GHzImpedance bandwidth: 31.6 % (1.57 - 2.16 GHz)
1.6 1.8 2 2.2 2.4
-20
-10
0
Frequency (GHz)
Reflection coefficient |S | (dB)11
Verification of swan resonance, not slot resonance
(1) Reflection coefficient
49
50
1.6 1.8 2 2.2 2.4 2.60
2
4
6
8
Frequency (GHz)
Gain (dBi)
• Maximum gain: 7.4 dBi (1.84 GHz)• Much higher than that of the slot antenna
(2) Antenna gain
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Measured radiation patterns at 1.8 GHz
-40 -30 -20 -10 0
30
150
60
120
90
120
60
150
30
180
0oo
o o
o
o o
o o
o oo
dB
90 90
150180
o
o
o
oo
dB-40 -30 -20 -10 0
30
150
60
90
120
60
150
30
180
0 oo o
o o
o o
o o
o oo
dB
H-plane (x-z plane)E-plane (y-z plane)-y
120
+y -x +x
Cross-pol Cross-pol
Co-pol
(a) (b)
Broadside radiation patterns observed.Co-pol > X-pol by more than 20 dB in the boresight
direction for both E and H planes
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Application:Wireless video system
Transmitter
Receiver
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Transmitter
DVD Player
Swan-DRA
Modulator
SlotMicrostripline
Transmitter
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Receiver
Antenna
Demodulator
LCD monitor 55
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Video
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Slot-coupled Apple-DRA
K. W. Leung, E. H. Lim and X. S. Fang, "Dielectric resonator antennas: From the basic to the aesthetic,"Proceedings of the IEEE, in press. 67
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z
x
50
50 2 25
75 75
20
49
y
x
11
75
Made of K-9 glass. Slot-coupled at the center. Design parameters:
Coupling slot: length L = 25 mm, width W = 2 mm.Substrate: εrs= 2.33, thickness d = 1.57 mm, size 55cm2.Microstrip feedline: width Wf = 4.7 mm, stub length Ls = 9 mm.
Antenna Configuration
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-40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
0oo
o o
o
o o
o o
o oo
dB
90 90
150180
o
o
o
oo
dB-40 -30 -20 -10 0
30
150
60
90
120
60
150
30
180
0 oo o
o o
o o
o o
o oo
dB
H-plane (x-z plane)E-plane (y-z plane)-y
120
+y -x +x
Cross-pol Cross-pol
Co-pol
(a) (b)
Broadside radiation patterns are observed.For both E plane and H plane, co-pol fields > X-pol fields by more than 20 dB in the boresight direction.
Measured radiation patterns of the Apple-DRA at 1.8 GHz
60
Transparent Omnidirectional Building-shaped DRA
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Probe-fed at the center.Design parameters:
DRA: Height 93 mm, square bottom of 21×21 mm2.Circular ground plane: Diameter of 19 cm.Coaxial probe: Length 19 mm, radius 0.635 mm.
z
x
23 12 14 25 14 5
14 9
14 93
21
y
1.27
19190
Antenna Configuration
62
Measured reflection coefficient
• Resonance frequency: 2.89 GHz• Impedance bandwidth: 36.5% (2.48 -3.59 GHz)
2 2.5 3 3.5 4-30
-20
-10
0Reflection coefficient |S | (dB)11
Frequency (GHz)
)4/( rlcf
)4/(3 rlcf
where f : resonance frequency of probe, c : speed of light in air, εr : dielectric constant of K9 glass.
Fundamental mode:
First higher-order mode
Verification of DRA resonance, not probe resonance
Estimation of probe resonance frequency (l = 19 mm)
= 1.5 GHz (εr = 6.85)
= 4.5 GHz (εr = 6.85)
63
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Omnidirectional radiation pattern
Measured radiation patterns（2.48 GHz）
-40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
90 90
150180
o
o
o
oo
dB-40 -30 -20 -10 0
30
150
60
90
120
60
150
30
180
o o
o o
o o
o o
o oo
dB
120
-x +x
0o= 0o=
x-z plane 60o=
Col-pol
Cross-polCross-pol
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Measured radiation patterns（2.89 GHz）
-40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
90 90
150180
o
o
o
oo
dB-40 -30 -20 -10 0
30
150
60
90
120
60
150
30
180
o o
o o
o o
o o
o oo
dB
120
-x +x
0o= 0o=
x-z plane 60o=
Col-pol
Cross-pol
Cross-pol
Stable radiation pattern
66
Measured radiation patterns（3.59 GHz）
-40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
90 90
150180
o
o
o
oo
dB-40 -30 -20 -10 0
30
150
60
90
120
60
150
30
180
o o
o o
o o
o o
o oo
dB
120
-x +x
0o= 0o=
x-z plane 60o=
Col-pol
Cross-pol
Cross-pol
Influenced by a higher-order DRA mode
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Transparent Dielectric Resonator Antennas Used as a Light Cover
Transparent Dielectric Resonator Antennas Used as a Light Cover
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Hollow hemispherical DRA used as a light cover
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Advantages of light-cover antenna
Indoor antennas widely found in modern buildings
Light-cover antennas can be mounted on ceilings
Lighting and antenna systems combined - save space
Both systems installed in one go - save cost & work
Excellent invisible antennas - avoid uneasy feeling ofradiation
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r
Hollow region
Ground plane
Transparent hollow hemispherical DRA
Feedline Coupling slot
x
z
d
a2 a1
To power supplyLED
rs
Antenna configuration
Made of K-9 glass. Slot-coupled at the center. Design parameters:
Hollow hemispherical DRA: a1 = 21.8 mm, a2 = 9.6 mm.Coupling slot: length L = 26 mm, width W = 1.8 mm.Substrate: εrs= 2.33, d = 1.57 mm, a size of 1515cm2.Microstrip feedline: Wf = 4.8 mm, Ls = 10.8 mm.
Coupling slot
Feedline
Transparent hollow hemispherical DRA
Ly
x
Wf
W
Ls
LED
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Measured and simulated S11
Measured bandwidth (without LED): Lower band (TE111 mode): 20.96% (2.22-2.74 GHz)Upper band (TE112 mode): 10.4% (5.49-6.09 GHz)Measured bandwidth (with LED): Lower band: 20.96% (2.22-2.74 GHz), Upper band: 10.2% (5.49-6.08GHz).
Reflection coefficient |S | (dB)11
Frequency (GHz)2 3 4 5 6
-30
-20
-10
0
TE111
TE311
TE112
Simulation (without LED)Measurement (without LED)Measurement (with LED)
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Field distribution
TE111 mode: 2.45 GHz TE112 mode: 5.86 GHz
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Measured (2.48 GHz), simulated (2.48 GHz).Broadside radiation patterns are observed for both planes.Co-polarized fields > cross-polarized fields by more than
18 dB in the boresight direction.
Lower-band radiation patterns
-40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
90 90
150180
o
o
o
oo
dB-40 -30 -20 -10 0
30
150
60
90
120
60
150
30
180
o o
o o
o o
o o
o oo
dB
120
H-plane (y-z plane)E-plane (x-z plane)-x +x -y +y
Simulation (without LED)
Measurement (without LED)
Measurement (with LED)
0o= 0o=Co-pol
X-pol X-pol
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Upper-band radiation patterns
Measured (5.8 GHz), simulated (5.8 GHz).Broadside radiation patterns are observed for both planes.Co-polarized fields > cross-polarized fields by more than
20 dB in the boresight direction.
-40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
90 90
150180
o
o
o
oo
dB-40 -30 -20 -10 0
30
150
60
90
120
60
150
30
180
o o
o o
o o
o o
o oo
dB
120
E-plane (x-z plane)
-x +x
Simulation (without LED)
Measurement (without LED)
Measurement (with LED)
0o=0o= Co-pol
X-pol X-pol
H-plane (y-z plane)
-y +y
75
Maximum lower-band gainWithout LED: 5.26dBi (2.44GHz), with LED: 5.43dBi (2.48GHz)Maximum upper-band gainWithout LED: 7.08dBi (5.9GHz), with LED: 6.76dBi (5.88GHz)LED only has negligible effect on the DRA performance.
Measured and simulated antenna gains
2 2.5 3 3.5 4 4.5 5 5.5 6-4
-2
0
2
4
6
8
10
12
Frequency (GHz)
Antenna gain (dBi)
Simulation (without LED)Measurement (without LED)Measurement (with LED)
76
Side view Top view
Omnidirectional rectangular glass DRA
77
Perspective view Bottom face
Omnidirectional rectangular glass DRA
78
79
Measured and simulated S11
Measured bandwidth (without LED): 28.8% (1.992.66 GHz)
1.8 2 2.2 2.4 2.6 2.8 3-30
-20
-10
0
Frequency (GHz)
|S11| (dB)
HFSS SimulationMeasurement (without LEDs)Measurement (with LEDs)
Probe mode DRA TM mode
80
Measured (2.40 GHz), simulated (2.40 GHz).Omnidirectional radiation patterns are observed.Co-polarized field > cross-polarized field by 20 dB or more.
Measured and simulated radiation patterns
( = 180 ) ( = 60 )oo ( = 0 )o
Co-pol
-40 -30 -20 -10 0
30
150
60
120
9090
120
60
150
30
180
o
o o
o
o o
o o
o oo
dB
0o
X-pol
-40 -30 -20 -10 0
30
210
60
240
90270
120
300
150
330
180
o
o o
o
o o
o o
o oo
dB
0o
X-pol
81
Measured antenna gain : 1.8 dBi (@2.4 GHz)
Measured and simulated antenna gains
1.8 2 2.2 2.4 2.6 2.8 3-4
-3
-2
-1
0
1
2
3
4
Frequency (GHz)
Gain (dBi)
HFSS SimulationMeasurement (without LEDs)Measurement (with LEDs)
82
Circularly polarized (CP) glass antenna design
In general, why CP antennas are needed?
Faraday effect
Fading effect
Alignment between transmit and receiveantennas can be relaxed.
83
84
Problem:
Copper strip not transparent
Solution:
Use transparent AgHT-coated glass strip
Drawback:
Lossy => reduction in efficiency
85
86
2.2 2.3 2.4 2.5 2.6 2.70
0.2
0.4
0.6
0.8
1
Frequency (GHz)
Efficiency
Copper patchITO glass without LEDsITO glass with LEDs
87
88
Integration of glass DRA with table lamp
89
Integration of glass DRA with table lamp
Save space
Excellent invisible antenna
Table-lamp antenna applied to a wirelessvideo system.
It is used in the transmitter.
It can also be used in the receiver.
90Modulator
Feeding probe
LEDs
Ground plane
Light-cover &Glass antenna
91
Video
9292
• 2D transparent antenna based on patch-antenna theory hasbeen briefly explained.
• Meshed or transparent conductors are normally used for 2Dtransparent antennas.
• 3D transparent antenna based on DRA theory has beenpresented.
• The transparent DRA can be used as a focusing lens,decoration, or light cover.
Conclusion
93
Thank you !Thank you !
94
Q & AQ & A