Computational Electromagnetics and Antennas Research...
Transcript of Computational Electromagnetics and Antennas Research...
Department of Electrical Engineering and Materials Research Institute Pennsylvania State University University Park, PA 16802 [email protected]
Douglas H. Werner, Director Computational Electromagnetics and Antennas Research Lab
Metamaterial-Enabled and Bio-Inspired
Electromagnetic/Optical Devices
Overview
What are Metamaterials?
Electromagnetic/Optical Metamaterials and Metasurfaces
Tunable and Reconfigurable Metamaterials
Invisibility Cloaks and Illusion Devices
Body Area Networks and Wearable Antennas
Bio-inspired Electromagnetics/Optics
Electromagnetic Metamaterials (Greek prefix "meta" – "beyond")
Artificial materials that can be engineered to exhibit extraordinary electromagnetic properties that do not occur, or may not be readily found, in nature.
Metamaterial-enabled devices have a wide range of applications in the RF, THz, IR, and visible spectrum.
Conventional vs. Metamaterials
Properties derived from
constituent atoms.
Properties derived from
constituent units (artificial atoms),
which can be engineered.
Negative Refraction
Empty glass Positive refraction Negative refraction!
Beam Bender Invisibility Cloaks
Perfect Lens
Carpet Cloak
The metamaterial technology and transformation optics approach enables unprecedented design flexibility and novel device applications.
Optical Black Hole
Negative Index Materials
Chiral Metamaterial
Active Metamaterial
GA
PSO
WDO
Nature-inspired Optimization Algorithms
Numerical EM Solvers
Novel Antennas and Metamaterials
+ Robust & Global Optimization + Large Number of Parameters + Real- and Discrete-valued Search Spaces
+ Improve Existing Antennas + Develop New Antennas + Design and Verify by Modeling, Fabrication and Characterization
+ Custom In-house EM Solvers + Industry Standard Software + Proven Computationally Efficient Techniques
CMA-ES
CLONALG
Design and Optimization of Antennas
Groundbreaking Meta-Antennas Octave Bandwidth Negligible Loss Metahorn Antenna
Lightweight*,
low cost
alternative to
machined, heavy
corrugated horns
* Critical for Space
Applications
A wire-grid metamaterial gives low E-plane
sidelobes from 3.4 GHz to 7.0 GHz.
Metahorn
Conventional
Horn
Simulation Measurement
Broadband Square Metahorn with Polarization-
Independent Radiation Patterns 12 GHz 18 GHz
14 GHz 16 GHz
0 dB
-40 dB
Broadband Monopole Enabled by
Ultra-Thin Metamaterial Coating
the bandwidth to over an octave while preserving the
radiation pattern of a simple monopole.
Measurements
confirmed that the
metamaterial increased
Press Coverage:
Metamaterial Lenses for Multi-Beam Radiation - 3D Radiation Pattern Comparison
monopole
Radiation
Pattern
1
3
4
2
monopole
x
y
z
Radiation Pattern
A redistribution of the radiated energy in desired directions!
4.25 GHz 4.85 GHz 5.10 GHz
The simulated and measured E-plane realized gain patterns with and without the lens confirm the wave bending effect in the elevation plane.
Simulation without the lens (dashed blue lines), simulation with the lens (solid blue lines), measurement without the lens (dashed black lines), measurement with the lens (solid black lines).
Z. H. Jiang, M. D. Gregory, and D.
H. Werner, "Experimental
Demonstration of a Broadband
Transformation Optics Lens for
Highly Directive Multibeam
Emission," Phys. Rev. B, vol. 84,
pp. 165111/1-6, October 2011.
DIGITALLY-CONTROLLED ELECTRICALLY-STEERABLE METAMATERIAL LENS ANTENNA
Tuning Demonstration Prototype Lens and Display Board
The physics of effective zero-index metamaterials (infinite phase velocity) allow for a completely steerable lens to be constructed with only two metamaterial states: on and off.
Hexagonal Unit Cell Design
Ideal Implementation Scanning Behavior Conceptual Design
Digitally-controlled switches within each resonator turn the
metamaterial on and off.
TUNABLE CROSSED ELD WITH METAMATERIAL SUBSTRATE FOR CIRCULAR POLARIZATION
(Simulated) Simulated Reflection Phase from the Metamaterial Surface
• The development of WBAN technology started around 1995 based on the idea of using wireless personal area network (WPAN) technologies to implement communications on, near, and around the human body.
• The FCC has approved a 40 MHz spectrum allocation for medical BAN low-power, wide-area radio links at the 2360-2400 MHz band. This will allow off-loading MBAN communication from the already saturated standard Wi-Fi spectrum to a standard band*
Applications: • Health monitoring, patient tracking, telemedicine, wearable
computing, battlefield survival, personal multimedia, etc.
Type of communication: • On-body, Off-body, and In-body.
Existing frequency bands for BAN systems: • Very/Ultra high frequency (VHF/UHF): ~ 10 MHz • Medical Implant Communication Services (MICS): 402 – 405 MHz • Wireless Medical Telemetry Services (WMTS): 608 – 614 MHz,
1395 – 1400 MHz, and 1427 – 1429.5 MHz • BodyLAN: ~ 900 MHz • Bluetooth: 2400 – 2480 MHz • ZigBee: ~ 2400 MHz, 915 MHz, and 868 MHz • Wireless Local Area Network (WLAN): 2400 & 5200 MHz • Ultra-wide band (UWB): 3.1 – 10.76 GHz
Body Area Network (BAN) Technology
ASSIST sensor node * Low-Rate Wireless Personal Area Networks (LR-WPANs) Amendment 4, IEEE Standard 802.15.4j, 2013.
Integrated Antenna Being Bent Integrated Antenna Conformed to Body
Reflection at Input Port of the Antenna
Measurement
Measurement
Robust to environment change!
Robust to structural deformation!
Measurements show that the antenna input impedance is very robust to bending and human body loading.
Metasurface-enabled Wearable Antenna --- 2.4 GHz MBAN band antenna measurement
0.1V/m
0.48W/kg
0.001W/kg
SAR E-field
Observing field distribution on human body – majority of the field is propagating on the back, right leg, head, and chest.
Metasurface-enabled Wearable Antennas --- MBAN band CP Wearable Antenna
x-y plane
RHCP
LHCP
x-z plane
RHCP LHCP
2.38 GHz
10V/m
y x
z
Stripline feed
Coupling aperture
Antenna
*J.B. Pendry et al., Science 312, 1780 (2006).
Invisibility and Cloaking: Science Fiction on the Verge of Becoming Reality…
Uniform-Thickness Cloak Uncloaked PEC
Cloaked PEC
D.-H. Kwon and D. H. Werner, “Two-dimensional Electromagnetic Cloak Having a Uniform Thickness for Elliptic Cylindrical
Regions,” Appl. Phys. Lett. 92, pp. 113502/1-3, 2008.
*Schurig et al., Science 314,
977 (2006). *Liu et al., Science 323, 366
(2009).
16
Lai et al., PRL 102, 253902 (2009)
Electromagnetic Illusion Created by Metasurfaces Using a single layer metasurface to achieve illusion.
PEC cylinder
Dielectric cylinder 1 (εr = 2) Dielectric cylinder 2 (εr = 20)
PEC cylinder with metasurface coating to mimic free space
Dielectric cylinder 1 with metasurface coating to mimic dielectric cylinder 2
Metasurfaces made of periodic metallic patterns
Super-Resolution / TO Lenses
Extreme-Angle Broadband Metamaterial Flat
Lens by Transformation Optics
The lens works by an
index of refraction tapering
from 1 at the edges to 4 in
the focal plane.
Transformation Optics Gradient Index Flat Lens
Biconvex Lens Layered TO
Flat Lens Many TO designs
require impractical
material
properties, but this
uses a quasi-
conformal
mapping to create
a design with
broadband, low-
loss, gradient-
index materials.
Isotropic µ = -1 Metamaterial for MRI Enhancement at 8.5MHz for Prostate Cancer Detection
Low-frequency performance is made possible by ring
resonators loaded with capacitors and inductors.
With the lens (green),
the lens resolves two
magnetic sources that
cannot be distinguished
without the lens (blue).
The lens also
increases the received
magnetic field by a
factor of 20 or more.
Normal Incidence 45 degree
Bulk TO
Flat Lens
C. Scarborough, et al., Appl. Phys. Lett., 101, 014101 (2012).
Fractal Geometry in Electromagnetics
Fractals in Nature
Sea Urchin
Leaf Growth
Lightning
Broccoli
Fractals in Electromagnetics
Sierpinski Monopole
Multiband Antenna
10 µm
Fractal Cross-Dipole
Frequency Selective Surface
Multiband Filter for the Mid-IR*
* J.A. Bossard, et al., IEEE Trans. Antennas Propagat., 54, pp. 1265-1276 (2006).
Bio-Inspired Electromagnetics:
Broadband Reflectors Found in Nature
* A.R. Parker, J. R. Soc. Interface, 2, pp. 1-17 (2005).
‘Chirped’ Gold
Beetle Shell
“Random”
Stack
“Chirped”
Stack
“Quarter-Wave”
Stacks
Butterfly
Chrysalis
‘Chaotic/Random’ Silvery Fish
εr1 εr2 εr1 > εr2
Dielectric Multilayers/Superlattices
Fractal Random Multilayers
Sta
ge
0
Sta
ge
1
Sta
ge
2
Sta
ge
3
Generator 1 Generator 2 Generator 3
Fractal random Cantor bar can
produce dielectric multilayer stacks
that appear ‘chaotic’
Sta
ge
0
Sta
ge
1
Sta
ge
2
Sta
ge
3
Sta
ge
4
Optimized fractal random dielectric
multilayer with broadband reflectivity in
the Mid-IR
SiO2
a-Si SiO2
27.9
µm
air R
T
2.5 3 3.5 4 4.5 5 5.5 6-90
-80
-70
-60
-50
-40
-30
-20
-10
0
Wavelength (m)
Sca
tte
rin
g M
ag
nitud
es (
dB
)
|RTE
|
|TTE
|
Normal Incidence
Super-Octave Absorbers for the Infrared
* J. A. Bossard, et al., ACS Nano (2014).
Absorptivity vs. Wavelength and Angle
polyimide
Pd metal
Si substrate
A
Measured
GA Optimized Unit Cell Geometry
Simulated
A
200 nm 600 nm
>90% Absorptivity
>1 Octave Bandwidth
>±45º Angular Stability
Polarization Independent
Optical Metamaterial Filters and Mirrors
Broadband Dispersion Engineered Photonic Metamaterial Filter
Transmission band: 3 ~ 3.5 μm Mean in-band insertion loss: < 1dB Mean out-of-band transmission: ~ -10.1dB In-band group delay variation: ~ 12fs
S. Yun, et al., Appl. Phys. Lett., 96, 223101 (2010).
Angle-tolerant Mid-IR All-Dielectric FSS Filter
Q. Hao, et al., Appl. Phys. Lett., 97, 193101 (2010).
Optical Complementary Metallic Membranes
All-Dielectric ZIM Perfect Mirror
468nm patterned a-Si on 0.5mm fused silica
Solid: Measurements Dots: Simulations
2.05 μm
S. Yun, et al., Appl. Phys. Lett., 102, 171114 (2013).
Z. Jiang, et al., Scientific Reports, 3, 1571 (2013).
Photonic Integrated Circuits Based on
Transformation Optics Devices
Transformation optics devices that perform diverse, simple functions can be integrated together to build complex photonic systems for optical communications, imaging, computing, and sensing.
Coordinate Transformation
At least 50 Awards and Recognitions have been received by the students and post-docs in CEARL since 1998 which include several prestigious Best Paper Awards given by international journals/societies, Feature Articles (selected for cover art) in highly rated international journals, as well as numerous Student Research Competition Awards given by international professional societies such as the IEEE, the University, the College and the Department.
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Conference,
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2008 IEEE APS
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We have at least 550 published journal articles and conference proceedings: IEEE Trans. on Nanotechnology Nature Materials Optics Express Physics Review B JOSA B ACS Nano Journal of Applied Physics Applied Physics Letters New Journal of Physics IEEE Antennas and Propag. Mag. IEEE Trans. on Antennas and Propag. IEEE Antennas and Wireless Propagation Letters …
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