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iWAT2014: Metamaterials-based Antennas
1
Metamaterials-based Antennas
Zhi Ning Chen
Professor
National University of Singapore
Advisor
Institute for Infocomm Research, Singapore
Metamaterial Antennas:
From Physics To Designs
Acknowledgements:
Dr Xianming Qing
Dr Liu Wei
Dr Lau Pui Yi
Dr Sun Mei
Dr Amir Khurrum Rashid
Mr Goh Chean Khan
iWAT2014: Metamaterials-based Antennas
3
Professor, Department of Electrical and Computer Engineering National University of Singapore Fellow, IEEE Distinguished Lecturer, IEEE AP-S Associate Editor, IEEE Trans AP Member, IEEE AP-S Fellow Committee Advisor & Principal Scientist, Institute for Infocomm Research Agency of Science, Technology and Research, Singapore Founding General Chairs, iWAT, IS 3T-in-3A, APCAP, IMWF
Current research interest: applied electromagnetic, metamaterials, and antennas for microwave, mmW, submmW, and THz systems.
140 keynotes & invited talks, 400 papers, 4 books, 31 patents, 28 licenses
CHEN Zhi Ning, PhDs 陈志宁
iWAT2014: Metamaterials-based Antennas
4
In this talk,
Background Brief History Review
Potentials & Challenges in Antenna Engineering
State-of-the-art Designs
Rethinking Strategy
Metamaterial-based Antennas
Case study
Comments
iWAT2014: Metamaterials-based Antennas
5
Background Information:
Brief Historic Review
Artificial Molecules in
NIM by Pendry in 20002
tt
ww
hh dd
Artificial dielectric
by Kock in19481
Experimental NIM
by Smith in 2001 Transmission-line based NIM
by Eleftheriades in 2002
1. The term artificial dielectric was originated by Winston E. Kock in 1948 when he was employed by Bell Laboratories.
2.J. B. Pendry, “Metamaterials and the Control of Electromagnetic Fields”
iWAT2014: Metamaterials-based Antennas
6
Background Information: Brief Historic Review
Pioneering Work: Negative Index
“Negative Refraction Makes a Perfect Lens” by JB Pendry, Phys. Rev. Lett., 85, 3966 (2000).
In 2000, Sir Pendry published a short but explosive paper in PRL
explaining the theoretical possibility of a perfect lens.
iWAT2014: Metamaterials-based Antennas
7
Background Information: Brief Historic Review
Working in Quadrant III
r
r
Most materials
in nature
Metals in optical bands
Ferro-magnetic
materials
0
: permittivity
: permeability
Unknown materials
(Mate-materials)
Notes: This idea proposed 40 years earlier by the Russian scientist Victor Veselago,
who suggested that a material with a negative refractive index–never seen in
nature–could produce an almost magical lens capable of creating images at a
resolution finer than the wavelength of light being used. After that, the work related
to metamaterials have been majorly focused double-negative materials.
iWAT2014: Metamaterials-based Antennas
8
Background Information: Brief Historic Review
Updates of Publications since 2000
21 66 213
403
689
1560
2160
3000
4250
4530
5260
6600
7700
8360
10 48 108 221
403
898
1200
1650
2070
2380
2760
3400
4060
4420
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013
matematerials matematerial antenna
1 March 2014 by Google Scholar
Metamaterials: 44,812
Metamaterial Antennas: 23,628
Meta-Ant/MetaM: 53%
iWAT2014: Metamaterials-based Antennas
9
Background Information:
Potentials in EM Engineering
Cloaking devices
Antennas
Absorber Superlens
Frequency ranging from microwave, THz to optical:
1. Shielding,
2. Low-reflection materials (absorber),
3. Novel substrates/superstrate,
4. Antennas/sensors,
5. Electronic switches,
6. “Perfect lenses,”
7. Resonators, and
8. etc.
iWAT2014: Metamaterials-based Antennas
10
Background Information:
Potentials in Antenna Engineering
To improve antenna design by:
Lowering antenna profile (conformal/flexible)
Reducing antenna volume/weight/cost
Widening bandwidth (impedance/phase/gain)
Enhancing gain (efficiency/directivity)
Suppressing mutual coupling
Widening operating frequency tuning range
Achieving controllable beam (shaping/steering/lobe)
iWAT2014: Metamaterials-based Antennas
11
Background Information:
Potentials in Antenna Engineering: Features
Double Negative (DNG)
Material (<0 & <0)
1960’s & 2000’s
Artificial Complex Impedance Surface
Zs =jL/(1- 2LC)
1940’s, 1970’s, 1990’s & 2000’s
Left-hand/negative index of
refraction (NIR)
Much less than a wavelength
with backward propagation
Narrow bandwidth
Electromagnetic bandgap (EBG) surface with
pass/stop bands
Tunable impedance surface (TIS) with
controllable reflection phase of 0-180o
On order of one half wavelength or more
Narrow/moderate operating bandwidth
DNI lens for high directivity
Zeroth order resonant antenna
with reduced size
Series-fed array with improved
beam-squint
Shell of antenna element
Patch antenna: directivity/efficiency
Dipole with reflector: directivity/ efficiency/
low profile
Waveguide/reflector/horn antenna:
directivity
FSS
me
ta
fea
ture
s
ap
plic
ati
on
s
Left/right handed scanning leaky wave antennas
iWAT2014: Metamaterials-based Antennas
12
Background Information:
Challenges in Antenna Engineering: General
Electrical:
Bandwidths: performance of interest
Gain: directivity & efficiency
Others: polarization, isolation, beamwidth, etc.
Mechanical:
Size: volume/conformal/low-profile
Integration: with other circuits
Others: robustness, lightweight, etc.
Commercialization (mass production):
Cost (materials/process/fabrication & installation)
iWAT2014: Metamaterials-based Antennas
13
Background Information:
Challenges in Antenna Engineering: Analysis
Antennas Metamaterials
Bandwidths: impedance/gain Difficult but Possible
Gain: directivity & efficiency Yes & Difficult
Size: volume/conformal/low-profile Promising*
Integration: with other circuits Promising
Cost: mass production
(fabrication & materials)
Possible
Overall Promising
*overall size against gain and bandwidth
iWAT2014: Metamaterials-based Antennas
14
Background Information:
State-of-the-arts in Antenna Engineering: Example
Used as superstrate (cover/lens/radome)
dipole/monopole/inverted-L/patch antenna:
high directivity & beam control
Used as substrate (with ground plane)
dipole/monopole/inverted-L antenna:
low profile & high directivity
patch antenna:
high directivity & efficiency & low coupling
•artificial surfaces with controllable reflection phase
•artificial magnetic conductors (AMC)
•electromagnetic bandgap (EBG) surfaces
iWAT2014: Metamaterials-based Antennas
15
Background Information:
State-of-the-arts in Antenna Engineering
(incomplete)
Suppression of inter-element mutual coupling: MIMO
Low profile of antennas: Cellular base-stations
Miniaturization of antennas (e.g. zero/negative-order resonator):
Portable devices
High gain for antennas with planar lens: horns/patch
High gain of antennas with zero-index loading: Vivadi@60GHz
Composite Right/Left-handed TL/LW antennas: Beam-steering
arrays
Zero-phase-shift-line loop antennas: RFID
Controllable active metasurface arrays: Satellite
Notes: Many metamaterials-based technologies have been explored for antenna
design. The incomplete list shows the technologies and their applications which have
been claimed by the researchers in their publications and some startups.
iWAT2014: Metamaterials-based Antennas
16
Background Information:
State-of-the-arts in Antenna Engineering
Hype or Reality?
Suppression of inter-element mutual coupling: MIMO?
Low profile of antennas: Cellular base-stations ? ?
Miniaturization of antennas (e.g. zero/negative-order resonator):
Portable devices ? ?
High gain for antennas with planar lens: horns/patch
High gain of antennas with zero-index loading: Vivadi@60GHz
Composite Right/Left-handed TL/LW antennas: Beam-steering
arrays ?
Zero-phase-shift-line loop antennas: RFID
Controllable active metasurface arrays: Satellite ? ?
Notes: However, we have not had any chance to see metamaterials-based products in
market so far although we have investigated on all antenna companies we can find
out. We studied the metamaterials related patents and the description of the products
which claimed that the designs are based on metamaterials.
iWAT2014: Metamaterials-based Antennas
Rethinking
Metamaterial
Antennas: ?
17
Metamaterial
Publications: 23,628
Notes: The observation raises a critical question how many ideas published in
scientific and even engineering journals have been successfully translated into
engineering designs such as antennas which really enhance the performance of
designs in conventional ways or/and invent new methods for engineering design. In
the other words, we need the translation from the physical concepts to engineering
designs. How to bridge this gap?
iWAT2014: Metamaterials-based Antennas
18
Rethinking:
Antenna Engineering: Case Study
Low profile of antennas: Cellular Base-stations
Key Parameters Requirements
Operating Frequency, MHz 1710-2690 (~45%) (VSWR<1.6)
Size, wavelength@1710MHz 0.8x0.8x0.10
Gain, dBi with efficiency >90% >7.0 at 1710 MHz; >11 at 2690 MHz
HP-Beamwidth >555 degree
Polarization dual-linear , 45 degree
Isolation of polarization >25 dB
Front-to-Back ratio >22 dB
Any solutions???
No way for any conventional methods.
Metamaterial-based solutions?
iWAT2014: Metamaterials-based Antennas
Rethinking
Metamaterial
Publications
Why and How?
Metamaterial
Antennas
? Inherent weakness of metamaterials (especially DNG) in terms of
bandwidth, efficiency, size, etc.
(not due to DNG itself but existing approaches to realize DNG, using strong
resonant structures)
? Too physical, enigmatic for engineers to understand/apply in design.
(good to describe physical phenomena using engineering languages such as
RCL, S-parameters rather than index, even permittivity or permeability etc)
? A real magic
(ought to tell engineers real success stories of metamaterials in antenna design
which have greatly enhanced performance, not potentials only.) 19
iWAT2014: Metamaterials-based Antennas
Rethinking
Definition of Metamaterials in Electromagnetics
20
“meta”: beyond
Metamaterials are artificial materials engineered to provide
properties not readily available in nature.
These materials usually gain their properties from structures rather
than composition, using the inclusion of small inhomogeneities to
enact effective macroscopic behavior.
Notes: We may have to review the definition of Metamaterials and not limit us to
DNG only.
From the definition mentioned above, the three key words have been highlighted in
red. In the other words, all EM structures can be considered as metamaterials if they
have all three key features.
iWAT2014: Metamaterials-based Antennas
21
r
r
Transparent Dielectric
(Most materials in nature)
Electrical Plasma
(Metals in optical bands)
Negative Index Materials
(Unknown materials:
double-negative or
backward-wave, or
left-handed materials)
0
1
1
??
??
near-zero refractive index ( )
Magnetic Plasma
(Ferro-magnetic materials)
rrn
Translation from Physical Concepts to Engineering
Z. N. Chen, “Metamaterials-based Antennas: Translation from Physical Concepts to Engineering Technology,”
Comments of FERMAT, February 2014 at www.e-fermat.org
Rethinking
Why ONLY Quadrant III?
Notes: Based on this thinking, we have a chance to explore the opportunities in other
quadrants besides Quadrant III. For example, we can even look at Quadrant I for the
structures which feature the magic properties that we have yet found in nature.
iWAT2014: Metamaterials-based Antennas
Rethinking
Work on All Quadrants!
22
r
r
Transparent Dielectric
(Most materials in nature)
Electrical Plasma
(Metals in optical bands)
Negative Index Materials
(Unknown materials:
double-negative or
backward-wave, or
left-handed materials)
0
1
1
??
??
near-zero refractive index ( )
Magnetic Plasma
(Ferro-magnetic materials)
rrn
zones of interest in Q I
a. 0≤r<1;
b. 0≤ r <1;
c. either r or r >>1;
d. both r and r >>1.
Z. N. Chen, “Metamaterials-based Antennas: Translation from Physical Concepts to Engineering Technology,”
Comments of FERMAT, February 2014 at www.e-fermat.org
Notes: Let us work on structures in all Quadrants not only Quadrant III, As well as
other structures featuring unique EM properties such as anisotropicity, chirality and
so on.
iWAT2014: Metamaterials-based Antennas
Rethinking
Promising Translation from Physical Concepts to
Engineering Technologies
23
Notes: The situation of metamaterials related R&D&C likes what is shown in the
photo: the sun is rising to bring hopes to us although the beach and sea is still in dark
due to the blockage of the mountains.
The photo was taken by Zhi Ning Chen in La Londe-les-Maures, Toulon, France in June 2013
iWAT2014: Metamaterials-based Antennas
Rethinking
Metamaterial-concept-based Antennas by Us
24
meta
Double Negative Material
(<0 & <0)
Artificial Complex Impedance Surface
Zs =jL/(1- 2LC)
featu
re
Left-hand/Negative index of refraction-
NIR
Zero-phase-shift lines
EBG surface with pass/stop bands
Tunable impedance surface (TIS)
Ap
plica
tio
ns
Zero-phase-shift-line antennas
•Electrically large near-field RFID antennas
•Omni-directional CP antennas
High permittivity dielectric
•Broadband low-profile dipole arrays
High impedance surface
•Thin Fabry-Perot cavity antennas
•Broadband planar antenna
Composite right/left-handed leaky wave antennas
•Consistent-gain array
•Broadband boresight radiation array
Zero-index antennas
•Gain-enhanced antipodal slot antennas
•High-gain patch antenna
iWAT2014: Metamaterials-based Antennas
Rethinking :
Metamaterial-concept-based Antennas for Industry
25
Electrically Large: Zero-phase-shift lines UHF near-field RFID reader antennas
Omni-directional CP antennas
High-gain: zero-index
Antipodal tapered slot antennas
Patch antennas
Low-profile: High-permittivity/High Capacitive Surface/AMC High-permittivity structure loaded broadband dipole array
High-capacity structure loaded broadband antenna
UHF near-field RFID AMC-loaded reader antennas
iWAT2014: Metamaterials-based Antennas
Zero-phase-shift-line-based Antennas: Electrically Large
UHF Near-field RFID Reader Antennas
26
Zero-phase-shift unit
@915 MHz Patented
Original solid loop
Qing, XM, Goh CK, and ZN Chen, A Broadband UHF Near-Field RFID Antenna, IEEE Trans. AP, vol.58, no.12, Dec 2010, pp.3829-3838
iWAT2014: Metamaterials-based Antennas
Zero-phase-shift-line-based Antennas: Electrically Large
Near-field UHF RFID Reader Antennas
27 Maximum area up to 280×280mm (500x500 mm)
Zero-phase-shift unit
x
y
RF in
250
250
Via to top layer
Bottom layer
Top layer
Parallel line
matching stubs
1.3
1.3
20.5
Unit: mm
2
2
2
22
2
2
22
2
10
73.3
6
6
6
30.7 30.730.730.7 30.6 31.3
31.3
31.3
31.3
31.3
31.3
31.3
31.3
31.3
31.3
31.3
31.3
31.332.3
26.326.326.326.3
41.85 34.35
33.133.133.133.1 33.1
33.133.133.133.1 33.1
33.133.1
33.3 24.9
33.433.1
74.1
68.3
L1=230.6
L2=103.6
o
L3=5
Distributed
capacitor
Straight line
Current
Current
-125 -100 -75 -50 -25 0 25 50 75 100 125-50
-40
-30
-20
-10
0
|HZ|, A
/m (
dB
)
X, mm
L2=60.5 mm
L2=103.6 mm
L2=146.7 mm
-125 -100 -75 -50 -25 0 25 50 75 100 125-50
-40
-30
-20
-10
0
|HZ|, A
/m (
dB
)
Y, mm
L2=60.5 mm
L2=103.6 mm
L2=146.7 mm
Patented
iWAT2014: Metamaterials-based Antennas
Zero-phase-shift-line-based Antennas: Electrically Large
Omni-directional Circularly Polarized Antennas
28
44 mm
35.25 mm
Feeding network
Feed point
44 mm
Segmented loop
Dipole
27.1 mm
Feed point
Segmented loop
Feed pointSubstrate
II
II
x
y
0
17.7
3 m
m Feeding 1
Feeding 2
Segmented
Loop Dipole
r1∠0°1∠0°
E1
(0°)
P
E2
(90°)
Patented
-50
-40
-30
-20
-10
0
0
30
60
90
120
150
180
210
240
270
300
330
-50
-40
-30
-20
-10
0
2.45 GHz
-50
-40
-30
-20
-10
0
0
30
60
90
120
150
180
210
240
270
300
330
-50
-40
-30
-20
-10
0
2.45 GHz
xy-plane yz-plane
2.40 2.42 2.44 2.46 2.48 2.50-10
-5
0
5
10
Gain
(dB
ic)
Frequency(GHz)
WLAN (2.4-2.5 GHz)
iWAT2014: Metamaterials-based Antennas
30
Zero-Index Antennas: High Gain
Antipodal Tapered Slot Antenna
@60-GHz
Substrate
y
x
z
Ws
L
S
g
ay
ax
L1
z = 0
z = h
Metal
Proposed ZIM unit cell on a dielectric substrate.
40 50 60 70 80 90 100-45
-40
-35
-30
-25
-20
-15
-10
-5
0
S p
ara
mete
r (d
B)
Frequency (GHz)
|S11
|
|S21
|
40 50 60 70 80 90 100-10
-5
0
5
10
eff
Frequency (GHz)
Re(eff
)
Im(eff
)
Characteristics of the ZIM unit
cell: (a) S-parameter data and (b)
retrieved effective permittivity.
x
y z
Wr
Wg
a1
a2
S b1 b2
L1
af1 af2
Wp
Ws
bf
L
top metal bottom metal
10 mm
16
.7 m
m
M. Sun, Z. N. Chen and X. Qing, “Gain Enhancement of 60-GHz Antipodal Tapered Slot Antenna Using Zero-Index Metamaterial”,
IEEE Trans. AP, vol.61, no.4, Apr 2013, pp. 1741 - 1746
iWAT2014: Metamaterials-based Antennas
31
Field distribution of the antenna at 60 GHz (xy plane, z = h/2):
(a) withoutZIM cells and (b) with ZIM cells.
50 52 54 56 58 60 62 64 66 68 70-45
-40
-35
-30
-25
-20
-15
-10
-5
0
|S1
1| (d
B)
Frequency (GHz)
with ZIM
original
50 52 54 56 58 60 62 64 66 68 700
3
6
9
12
15
Pea
k G
ain
(d
Bi)
Frequency (GHz)
with ZIM (silver)
original
with ZIM (PEC)
50 52 54 56 58 60 62 64 66 68 700
3
6
9
12
15
Gai
n i
n x
-dir
ecti
on
(d
Bi)
Frequency (GHz)
with ZIM
original
Rethinking: Case study
Gain-enhanced Antipodal Tapered Slot Antenna
iWAT2014: Metamaterials-based Antennas
32
Rethinking: Case study
High & Anisotropic Permittivity Structure Loaded
Low profile Broadband MIMO Antenna
No. Parameters Specifications
1. Operating Frequency 1.71-2.65GHz (43%) for VSWR<1.5
2. Antenna size: mm 200x300x38 ([email protected])
3. Gain >12dBi
4. Cross-Polarization >25dB in all direction
5. Sidelobe Level >15dB
6. Backlobe Level -25dB
7 H-Plane Beamwidth 20°~25° (10dB)
iWAT2014: Metamaterials-based Antennas
33
Rethinking: Case study
High & Anisotropic Permittivity Structure Loaded
Low profile Broadband MIMO Antenna
>30
>6
high permittivity >30 and high reflective index >6
Permittivity is also anisotropic along x, y, z directions!
iWAT2014: Metamaterials-based Antennas
34
Rethinking: Case study
High & Anisotropic Permittivity Structure Loaded
Low profile Broadband MIMO Antenna
Comparisons of impedance matching and gain for single dipole antenna
(Air, high permittivity material, HAPS)
2.0 2.5 3.0 3.5 4.0 4.5 5.0-40
-30
-20
-10
0
|S1
1|, d
B
Frequency, GHz
Dipole printed on PCB with r=4.4
Dipole loaded with dielectric r=36
Dipole loaded with HPS
10%
40%70%
2.0 2.5 3.0 3.5 4.0 4.5 5.0-6
-3
0
3
6
9
12
Dipole printed on PCB with r=4.4
Dipole loaded with dielectric r=36
Dipole loaded with HPS An
ten
na G
ain
, d
Bi
Frequency, GHz
9.3 dBi
iWAT2014: Metamaterials-based Antennas
35
Rethinking: Case study
High & Anisotropic Permittivity Structure Loaded
Low profile Broadband MIMO Antenna
No. Parameters Specifications
1. Operating Frequency 1.71-2.65GHz (43%) for VSWR<1.5
2. Antenna size: mm 200x300x38 ([email protected])
3. Gain >12dBi
4. Cross-Polarization >25dB in all direction
5. Sidelobe Level >15dB
6. Backlobe Level -25dB
7 H-Plane Beamwidth 20°~25° (10dB)
Patented
iWAT2014: Metamaterials-based Antennas
Rethinking: Case Study
High-capacity-loaded Low-profile Broadband WLAN Antenna
Boresight realized gain and |S11| of mushroom antenna and conventional patch array
Antenna Impedance bandwidth
(|S11| < −10 dB)
Realized gain
(dBi)
SLL
(dB)
F/B
(dB)
mushroom
antenna 4.61-6.29 GHz, 30% 8.1 ~ 11.0 −6 ~ −11.2 7.5 ~ 14.6
Patch array 5.43-5.87 GHz, 8% 10.3 ~ 11.2 −12 ~ −12.3 12 ~ 12.3
Slot-fed patch array
Slot-fed wideband
mushroom antenna
3 4 5 6 7 8-10
-5
0
5
10
15
|S11
|, proposed antenna
|S11
|, patch array
gain, proposed antenna
gain, patch array
Bo
resi
gh
t re
ali
zed
gain
(d
Bi)
Frequency (GHz)
-50
-40
-30
-20
-10
0
|S1
1| (d
B)
36 W Liu, Z. N. Chen and X. Qing, “Metamaterial-Based Low-Profile Broadband Mushroom Antenna”, IEEE Trans. AP, vol.62, no.3,
Mar 2014, pp. 1165 - 1172
iWAT2014: Metamaterials-based Antennas
Rethinking: Case Study
AMC-loaded Low-profile Near-Field RFID Antennas
37
Pending for patent
Impinj Antenna
Cavity-backed dual-loop antenna
67 mm
55 mm
30 mm
AMC-loaded cavity backed antenna
iWAT2014: Metamaterials-based Antennas
38
Fast development of wireless applications strong increasing
demand for high-performance antennas.
Metamaterial, as a concept, has opened a new window
for innovative antenna design!
Hot topics:
New methods to invent DNG structures for engineering
Translate the physical concepts to technology for applications
Miniaturization / compact
Broadband / multiband
Diversity / co-existence
Tunable / switchable
Super gain
Low cost / cost effective
My Comments
iWAT2014: Metamaterials-based Antennas
Debate Session@iWAT2014:
My Opinion
39
Translation from Physical Concepts to Engineering
Z. N. Chen, “Metamaterials-based Antennas: Translation from Physical Concepts to Engineering Technology,”
FERMAT, February 2014, www.fermat.org
2.metamaterial: possibility but aspirant
•Medicine to solve all “headache” (existing
technical challenges)??
•Unique features for specific challenges
1.metamaterial: a concept not technology but
possibility:
•Everything possible (Q I,II& IV to Quadrant III)
•Thinking out-of-the-box
•Why limited to Quadrant III
iWAT2014: Metamaterials-based Antennas
Debate Session@iWAT2014:
My Opinion
40
Translation from Physical Concepts to Engineering
Z. N. Chen, “Metamaterials-based Antennas: Translation from Physical Concepts to Engineering Technology,”
FERMAT, February 2014, www.fermat.org
3.metamaterial: opportunity-suggestion
•Scientists: exploring physical issues for crazy
ideas
•Engineers: understand and translate the ideas
for tech
4. My views
•Scientists: opportunity when things
unclear/unknown
•Engineers: opportunity when things clear/well-
known
iWAT2014: Metamaterials-based Antennas