dl presentation uw...pulse shaping with transitions n possible to design extremely deep nulls n each...

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

Copyright Prof. Gregory D. Durgin 2

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?


MINIMUM-POWER RF ENERGY HARVESTING


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:


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


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


All on the Same Graph


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


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


MINIMUM-POWER WIRELESS DATA EXCHANGE


How UHF RFID Systems Work n  Harvest an incident RF Wave n  Very low power consumption n  Power and communications channel both present

Copyright Prof. Gregory D. Durgin14

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


QTT Links @ Georgia Tech Campus


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

Copyright Prof. Gregory D. Durgin18

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


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


Pulse Shaping with Transitions


Perfect Pulses


Modulation with Perfect Pulses


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…


SUPPLEMENTAL SLIDES


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


HIMR Estimate vs. Ground Truth


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.


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


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

dl presentation uw...pulse shaping with transitions n possible to design extremely deep nulls n each...

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