dl presentation uw...pulse shaping with transitions n possible to design extremely deep nulls n each...
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the Future of RF Systems that Never Plug-in
Prof.GregoryD.Durgin,GeorgiaTechSchoolofECEDistinguishedLectureofIEEECRFID
WirelessoreverF
IEEE CRFID n Council within the IEEE n Conference Series
q IEEE RFID (April 2019 in Phoenix, US) http://2018.ieee-rfid.org
q IEEE RFID-TA (Sep 2018 in Macau SER, China) http://2018.ieee-rfid-ta.org
n Educational outreach, distinguished lectures n IEEE Virtual Journal on RFID n IEEE Journal on RFID launched in 2017 n 21 member IEEE societies
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Personal History n Ph.D. at the end of 2000 from Virginia Tech (Mobile
& Portable Radio Research Group) n American researcher visiting Morinaga Laboratory
(Osaka University) for 1 year n Professor in GT School of ECE (2003-present),
research program at http://www.propagation.gatech.edu q Backscatter Radio q Wireless Channel Modeling
n Faculty Director of Opportunity Research Scholars (ORS) Program
n YouTube™ Channel: profdurgin
q Wireless Power Transfer q Radiolocation
Big Questions to be Answered
Information: What is the Minimum Power Required for Wireless Data Exchange? Energy Harvesting: How much RF power can be converted to usable electronic functions? Computation: What is the minimal amount of power required to perform computation?
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MINIMUM-POWER RF ENERGY HARVESTING
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Trends in Electronics: UHF RFID This trend is driving the current buzz around the Internet of Things (IoT) and related technologies. This energy efficiency doubles every 46 months. The 100m tag will likely occur around 2020. Or will it?...
P. Nikitin, KVS Rao, S. Lam, “UHF RFID Tag Characterization: Overview And State-of-the-Art”. AMTA Conference, Seattle, Oct 2012.
How to Rectify RF Power Lots of different circuits, but they all have the same limitation … diodes. Diodes must turn-on before rectification, so they have a power “overhead” Curvature of a Schottky Diode:
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C.R. Valenta, G.D. Durgin. “Survey of Energy-harvester Conversion Efficiency in Far-field, Wireless Power Transfer Systems.” IEEE Microwave Magazine. vol 14, no 4, June 2014. 10 pages.
Survey of RF Harvesting Efficiencies
ï30 ï20 ï10 0 10 20 30 40 50 60 700
20
40
60
80
100
Input Power (dBm)
Effic
ienc
y (%
)
900 MHz2.4 GHz5.8 GHzAbove 5.8 GHz
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C.R. Valenta, G.D. Durgin. “Survey of Energy-harvester Conversion Efficiency in Far-field, Wireless Power Transfer Systems.” IEEE Microwave Magazine. vol 14, no 4, June 2014. 10 pages.
Example RF Thermoelectric Generator
q Convert RF-heat-DC q Converts more efficiently
than diodes at low power q Outputs much higher DC
voltage than input RF
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All on the Same Graph
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Play a Game: What to Passivize
headlampfailure
wiper fluidlevel
magnetometer
reflectionsensing
windshielddrop sensor
door ajarsensor
localizedthermostat
corrosivitysensor
tire pressuresensor
antennarelay
proximitywaypoint
brake fluidlevel
steering fluidlevel
oil levelsensor
transmissionfluid
batteryvolts
tire balancesensor
glass break
hoodopen
mirroradjust
seatbeltin use
passengersensors
windowlevel
taillampfailure
interiormic
externalmic
batteryamps
enginetemp
biometricdata
hand gripsensor
transparenttoll RFID
passivebuttons
passivetouchscreen
tachometer(engine)
CO safetysensor
wipercondition
componentalmanac
qualityof oil
paint jobalmanac
tachometer(belts)
gasolinetank
treadware
noise-cancelmics
indicatorLEDs
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Key Points n Conventional chip-making has stalled RF energy
harvesting n There is still a lot of room for improvement n Unconventional approaches are promising (tunnel
diodes, MIM diodes, spin diodes, RFTGs, etc.) n Intermediate forms of energy-conversion
(thermal, acoustic, mechanical, light, etc.) can outperform Schottky diodes at low power levels
n Lots of cool applications
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MINIMUM-POWER WIRELESS DATA EXCHANGE
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How UHF RFID Systems Work n Harvest an incident RF Wave n Very low power consumption n Power and communications channel both present
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RF Tag
RF Reader
1
8
23
4
6
75
Generate
Locate
RadiatePropagate
Harvest
Scatter
Receive
Sense
Quantum Tunneling Tag (QTT) Use RF negative-resistance devices (like tunnel diodes) as reflection amps Bank energy and bias the circuitry so conservation of energy still holds Eliminates the need for RF signal-generator circuitry, which dominates power consumption at low transmit power levels
Demonstration of Actual Data n 5.8 GHz carrier n Low-powered
transmitter (-20 dBm) n TR separation distance
of 7 m n Transmit and Receive
antenna gains of 6 dBi n 250 kbits/sec transition n About 35 dB of
reflection amplifier gain
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QTT Links @ Georgia Tech Campus
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Scattering on top of Information n Ambient Communications: Like backscatter
radio, except q Not scattering back to source, but to another location q Requires detection in the presence of massive jamming
n Remote telemetry for all sorts of sensor applications
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Key Issue n Enormous potential self-jamming n Inability to cancel self-jamming severely limits
range; need hardware pre-filtering before demod n Key insight: use design of modulation, recording,
channel, line, etc. codes
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Uncoded BPSK Spectral Sketch
frequency (log-scale)
Pow
er (l
og-s
cale
) BPSK Spectrum
fb
Orange Noise
1 0
Rb-3Rb 2Rb-2Rb 3Rb-Rb 0
real
BPSK PulseFourier
Transform
Manchester/FM0 Spectrum
frequency (log-scale)
Pow
er (l
og-s
cale
)
Manchester Spectrum
fb
Orange Noise
2Rb
-6Rb
4Rb
-4Rb
6Rb
-2Rb imag
Pulse Fourier Transform
1 0
Manchester Coding
Pulse Shaping with Transitions n Possible to design extremely deep nulls n Each transition is a degree of freedom that can be
used to deepen the null (remove O(f^n) content) n Set of n-transitions that maximizes DC nulls
results in a “perfect” pulse
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Pulse Shaping with Transitions
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Perfect Pulses
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Modulation with Perfect Pulses
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Example PP Modulation onto FM
26 (Signal-to-Interference)
Summary n Emergence of long-range backscatter and ambient
communications n New paradigm for communications and
networking n Exploring the Uses of Perfect Pulses
q Ambient/backscatter communications q Wireless Power Transfer (continuous power tracking) q Low-bit Quantizers q Other Signal Processing…
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SUPPLEMENTAL SLIDES
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Helmet Shock Sensor System: 5.8 GHz backscatter tags equipped with low-powered, accelerometer/gyrometer MEMs sensors that track real-time head trauma events on a sports field Communications: provides more than 200 packets of 6-axis motion data per second at 30m range Power: oin cell battery provides potentially months of operation
https://www.youtube.com/watch?v=_DGn6HPooRk
Wireless Motion Capture Hybrid Microwave Inertial Reflectometry (HIMR) uses phase measurements + inertial data from sensor link to pinpoint a backscatter tag Tests on a 5.8 GHz tag on a high-speed robotic positioning arm produce position estimates with mean and standard deviation errors of less than 2mm
Demonstration n 5.8 GHz backscatter
setup n Tag sends 200 packets
per second of 3-axis accelerometer data
n Motion track capable of moving tag up to speeds of 1.6 m/s
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HIMR Estimate vs. Ground Truth
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Detection of Card Skimming Devices
Electromagnetic Integrity and Security Assay (ELISA) System
M.Morys, M. Akbar, G.D. Durgin, “Malevolent Object Detection Using Microwave RFID Tags,” IEEE RFID 2013
How ELISA Works Sensitized microwave antenna (upper right) with load-modulated IQ signal returned to a nearby reader (lower right). Constellation remains constant excepting temporary changes during human equipment usage. Any dielectric components or small wires (e.g. a small foreign electronic device) placed nearby will distort the constellation.
M.Morys, M. Akbar, G.D. Durgin, “Malevolent Object Detection Using Microwave RFID Tags,” IEEE RFID 2013
Measured Performance As a short, thin wire is moved away from the loop antenna, the backscatter amplitude and phase changes, as measured by “Normalized Symbol Distance”. Highly reliable measurement, nearly impossible to spoof. Other tamper detection applications possible.
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Hope Diamond Security System System: ELISA-based security system that works through ceilings, walls Communications: backscatters 5.8 GHz FSK temperature, humidity data with custom protocol Power: Coin cell and passive tags designed and built
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Electro-thermal Model of an Antenna + Load
VAcos(2πft)
RARL
+
_VL
+_
+_
Antenna Load
RARL
+
_VL
+_
+_
Antenna Load
(a) thermal noise reception (b) thermal noise + signal reception
Thermodynamic Limit of CW RF Harvesting