Autonomous Wireless Sensors and RFID's: Energy harvesting ... · Autonomous Wireless Sensors...

Nov. 9, 2012

Apostolos GeorgiadisCentre Tecnologic de Telecomunicacions de Catalunya

(CTTC)Barcelona - Spain

Autonomous Wireless Sensors and RFID's: Energy harvesting Material and Circuit Challenges

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CTTC, Castelldefels – Barcelona

• Founded in 2001• Permanent research staff: 34 Ph.D., 24 M.Sc.

7 Assoc. Researchers• 3500-m2 building• 7 Research Areas: Hardware eng., Radio, Access,

Communications Subsystems, IP, Optical networking, IQe

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3 CTTC, Castelldefels – Barcelona, SPAIN

• Energy Harvesting and RFID

• Oscillator design including integrated CMOS oscillators (Fig. 1)

• Active antennas, phased arrays (Fig. 2), retro-directive arrays (Fig. 3)

• Substrate Integrated Waveguide (SIW) (Fig. 4)

• Efficient Power Amplifier

Active microwave circuit design

Fig. 1. CMOS VCO for UWB-FM

Fig. 2. C-band Coupled Oscillator Reflectrarray prototype

Fig. 3. S-band retro-directive array.Fig. 4. SIW circuits.

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Outline

• Introduction / Motivation

• Energy harvesting solutions and challenges

− Solar, Mechanical,

Thermal, Electromagnetic

• Flexible Materials

• Integration of Harvesting Modules

• Summary

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Introduction

• Ubiquitous sensor networks

− Monitoring (environment, wild-life), security, health…

− Conformal and low profile circuit topologies

− Low cost (manufacturing, material and maintenance)

• Autonomous operation

− Operating with high efficiency

− Minimize dissipated power / maximize harvested power

• Green networks

− Environmental friendly materials and fabrication (Spent batteries pose a significant waste management concern)

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Energy Harvesting

• Choice of harvesting module(s) is application

dependent

• Hybrid harvesting modules required to guarantee

sensor autonomy

• Transducer efficiency depends on available power

density

• Storage modules must also be considered

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Energy Harvesting

[1] Silicon Solar Inc., Flexible Solar Panels 3V, http://www.siliconsolar.com/flexible-solar-panels-3v-051282-p-500992.html.

[2] Perpetuum, http://www.perpetuum.com/.

[3] MicroPelt Inc., TEG MPG-D751. http://www.micropelt.com.

[4] A. Georgiadis, G. Andia, and A. Collado, "Rectenna Design and Optimization Using Reciprocity Theory and Harmonic Balance Analysis for Electromagnetic (EM) Energy Harvesting, " IEEE Antennas and Wireless Propagation Letters, Vol. 9, pp. 444-446, July 2010.

Energy Sources Harvested power

examples

Conditions

Light / Solar 60 mW 6.3 cm x 3.8 cm Flexible solar cell

AM1.5G Sunlight (100 mWcm-2) [1]

Kinetic

Mechanical

20 mW PMG-FSH Electromagnetic

transducer[2]

Thermal 0.52 mW Thermoelectric Generator TEG [3]

Electromagnetic 0.0015 mW Ambient power density

0.15 uWcm-2 [4]

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Energy Harvesting

Thad Starner, 'Human powered wearable computing', IBM systems journal, vol. 35, no. 3-4, 1996

Human Body SourcesTotal available power

from body

Available power for

harvesting

Body heat 2.8W - 4.8 W0.2-0.32 W

(neck brace)

Breathing band 0.83 W 0.42 W

Walking 67 W 5.0-8.3 W

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Solar Energy Harvesting

• Photovoltaic Effect

(Observed by Becquerel 1839)

• American Society for

Testing and Materials

(ASTM)

Reference Solar Spectra

• ETR Spectral Irradiance

Distribution is modeled as

black-body radiation

with T= 5800 K

• Atmosphere Absorption

bands visible

• Principles of thermodynamics and black-body radiation allow to

estimate performance limits of solar cells

(Shockley-Queisser Limit 1961)

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Solar Energy Harvesting

• wafer based solar cells (150 $/m2 – efficiency 20%)

• thin film solar cells

(30 $/m2 – efficiency 5-10%)

• third generation solar cells

(high efficiency, low cost)

Cost ($/m2)

20

40

60

80

100

0100 200 300 400 5000

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M. Green, Third Generation Photovoltaics,

Advanced Solar Energy Conversion,

Berlin Heidelberg: Springer-Verlag, 2006.

Challenges

High efficiency and low cost

Integration with other circuitry

Indoor conditions?

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Solar Energy Harvesting

• Solar cell efficiency, measured under AM1.5G at T = 25 C

Classification Efficiency (%) Voc (V) Js (mAcm-2) FF (%) Description

c-Si 25 0.706 42.7 82.8 UNSW PERL

mc-Si 20.4 0.664 38 80.9 FhG-ISE

GaAs (thin film) 28.1 1.111 29.4 85.9 Alta Devices

CIGS 19.6 0.713 34.8 79.2 NREL

CdTe 16.7 0.845 26.1 75.5 NREL

a-Si 10.1 0.886 16.75 67 Oerlikon Solar Lab

Dye Sensitised 10.9 0.736 21.7 68 Sharp

Organic polymer 8.3 0.816 14.46 70.2 Konarka

M.A. Green, K. Emery, Y. Hishikawa and W. Warta, ‘Solar cell efficiency tables (version 38),’

Progress in Photovoltaics: Research and Applications, vol. 19, pp. 565-572, May 2011

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12 Kinetic/Vibration Energy Harvesting

• Conversion of mechanical movements

to electrical energy

– Vibrations

– Displacements

– Forces or pressures

• Sources

– Traffic

– Human movement

– Heating, Ventilating and AC (HVAC)

– Air currents

– Water movement

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13 Kinetic/Vibration Energy Harvesting

• Transducer types:

Electromagnetic (inductive)

- Faraday’s law

Electrostatic (capacitive)

- Vary the capacitance or charge of a

variable capacitor

Piezoelectric

- Piezoelectric strain d tensor relating

Mechanical Stress T to Electric

Displacement D

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14 Kinetic/Vibration Energy Harvesting

• Vibration transducers modeled by

mass m, attached to a frame using a

spring k [*].

• Mechanical to electric conversion

losses included in d.

Pemax = m2A2/(8d)y(t) = Yo sin(wt) A = w2Yo

[*] C.B. Williams and R.B. Yates, ‘Analysis of a Micro-Electric Generator for Microsystems,’ in

Proc. 8th International Conference on Solid-state Sensors and Actuators and Eurosensors IX,

Stockholm, Sweden, pp. 369-372, June 25-29, 1995.

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15 Kinetic/Vibration Energy Harvesting

• Require low frequency high-Q resonators

• Application dependentApplication / Vibration source Vibration

frequency (Hz)

Acceleration

amplitude (ms-2)

Door Frame (after door closes) 125 3

Clothes Dryer 121 3.5

Washing Machine 109 0.5

HVAC vents in office building 60 0.2-1.5

Refrigerator 240 0.1

Small microwave over 121 2.25

External windows next to busy street 100 0.7

S. Roundy, "On the Effectiveness of Vibration-based Energy Harvesting,” Journal of Intelligent Material Systems and Structures, vol. 16 no. 10, pp. 809-823, Oct. 2005.

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16 Kinetic/Vibration Energy Harvesting

Challenges:

Self-tuning / Adaptive tuning, Wideband / Multiband

Description Frequency (Hz) Power

(mW)

REF

MEMS AlN Piezoelectric 325 0.085 [*]

JouleThief Piezoelectric 50, 60, 100, 120 1.2 [**]

PMG-FSH Electromagnetic 50, 60, 100, 120 20 [***]

[*] R. Elfrink, et al., "First autonomous wireless sensor node powered by a vacuum-packaged piezoelectric

MEMS energy harvester," in Proc. IEEE International Electron Devices Meeting (IEDM), pp.1-4, 7-9 Dec. 2009.

[**] JouleThief, AdaptivEnergy.

[***] PMG FSH, Perpetuum.

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Thermal Energy Harvesting

• Conversion of temperature differences to

electrical energy.

• Sources

• Waste heat from industrial plants

• Heating systems

• Automobiles, other vehicles

• Human body

• Three thermoelectric

phenomena.

• Seebeck

• Peltier

• Thomson

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Thermal Energy Harvesting

• The Seebeck coefficient is much higher for semiconductor

materials rather than metals and metal alloys, where it can

reach magnitudes of 1mV/K.

• Thermoelectric generators (TEGs) are formed by pairs of

coupled of N-doped and P-doped semiconductor pellets

connected electrically in series and placed between two

thermally conductive plates.

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Thermal Energy Harvesting

• Gulielmo Marconi

• ~ 1895

• Villa Griffone,

Bologna, Italy

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Thermal Energy Harvesting

• Thermoelectric

Figure Of Merit:

• High Seebeck Coefficient (α)

• High Electrical Conductivity (σ)

• Low Thermal Conductivity (λ)

S. Beeby and N. White, Energy Harvesting for

Autonomous Sensors, Artech House 2010.

ZT � α�σT

λ

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Thermal Energy Harvesting

Wrist watch: SEIKO thermic

~ 20-40 uW required to power a quartz digital wrist-watch

S. Beeby and N. White, Energy Harvesting for Autonomous Systems,

Norwood: Artech House, 2010.

S. Kotanagi, et al., “Watch Provided with Thermoelectric Generation Unit,”

Patent No. WO/1999/019775.

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Thermal Energy Harvesting

Challenge:

Increase conversion efficiency and maintain temperature

gradient

Conversion Efficiency limited by Carnot Efficiency

n < ( THOT – TCOLD ) / THOT

Example:

TCOLD = 293 K (20 C) and THOT = 303 K (30 C) => n < 3,3 %

TCOLD = 233 K (-40 C) and THOT = 293 K (20 C) => n < 20,48 %

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23 Thermal Energy Harvesting from Power Amplifiers

φ � n� 2 0.5n� � 4/ZT�����

Conversion efficiency

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24 Electromagnetic Energy Harvesting

• Conversion of ambient low power

electromagnetic sources to electrical power

• An Electric field of 1V/m in air corresponds to an EM power

density of 0.26 uW/cm2

• Key element: Rectenna

(Brown US3434678, 1969).

• Application dependent.

• Conversion efficiency

for available input power

of ~ -20 dBm is 10% - 20%.

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25 Electromagnetic Energy Harvesting

Challenges:

• Compact antenna elements, arbitrary polarization, broadband, multi-band designs

• EM simulation to model radiating element.

• Nonlinear optimization to model rectenna circuit and optimize rectifier taking into account the antenna properties.

• Antenna in receiving mode(Norton, Thevenin equivalent, Reciprocity)

• Measurement campaigns necessary

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26 Electromagnetic Energy Harvesting

Rectenna design example

• 2.40GHz - 2.48GHz ISM band

• Aperture coupled patch topology:

• Circuit and radiator layers are made of Arlon A25N 20mil thick

• Separated by a Rohacell51 layer of 6mm in order to achieve the desired bandwidth.

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27 Electromagnetic Energy Harvesting

Circularly polarized rectenna

O. A. Campana Escala, G. A. Sotelo Bazan, Apostolos Georgiadis, and Ana Collado, "A 2.45 GHz Rectenna with Optimized RF-to-DC Conversion Efficiency," PIERS, Marrakesh, Morocco, March 20-23, 2011.

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28 Electromagnetic Energy Harvesting • Joint antenna and rectifier optimization using

Thevenin equivalent of antenna in receive

mode.

A.Georgiadis, G. Andia-Vera, A. Collado “Rectenna design and optimization using

reciprocity theory and harmonic balance analysis for electromagnetic (EM) energy

harvesting,” IEEE Antennas and Wireless Propagation Letters,

vol. 9, pp. 444-446, 2010.

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• Open circuit voltage maybe calculated using reciprocity theory

• One may optimize in harmonic balance the efficiency at a desired direction of arrival.

Power Harvesting: Electromagnetic Energy

Slide 29

A.Georgiadis, G. Andia-Vera, A. Collado “Rectenna design and optimization using reciprocity theory and harmonic balance analysis for electromagnetic (EM) energy harvesting,” IEEE Antennas and WirelessPropagation Letters, vol. 9, pp. 444-446, 2010.

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• Circuit topologyimportantin low available powerconditions

• Trade-off betweenefficiencyand output voltage

Power Harvesting: Electromagnetic Energy

Slide 30

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31 Electromagnetic Energy Harvesting

• Challenge: determine available power

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Flexible Substrates

• Flexible substrates

− Paper

− Liquid crystalline polymer

(LCP)

− Textile

− Metal coated PET (polyethylene terephthalate)

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Flexible Substrates

Paper− Dielectric constant (*):

3.3 (@ 2 GHz)

− Loss tangent (*): 0.08 (@ 2 GHz)

− Can be made hydrophobic

− Inkjet printing

− Cost : very low

−Multilayer capability

Li Yang, et. al, ‘ RFID Tag and RF Structures on a Paper Substrate

Using Inkjet-printing Technology, IEEE Transactions on Microwave Theory

and Techniques, vol. 55, no. 12, pp. 2894-2901, Dec, 2007.

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Flexible Substrates

PET (Polyethylene Terephthalate)· Dielectric constant:

3.3 (@ 0.9 GHz)

· Loss tangent: 0.05 (@ 0.9 GHz)

· Thickness: 50 um – 100 um

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Flexible Substrates

Liquid crystalline polymer (LCP)· Dielectric constant: 2.9 (@ 10 GHz)

· Loss tangent: 0.0025 (@ 10 GHz)

· Water absorption < 0.04%

· Lamination < 282º C

· Multilayer capability

· Laser drilling (YAG, CO2)

· Low cost

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Flexible SubstratesTextile materials

• Substrates: natural or man-made fibers, Synthetic fibers:

Textile Aramid FleeceUpholstery

fabricVellux Cordura

PropertiesStrongHeat

resistant

Driesrapidly

Mixture of polyester

and polyacryl

Synthetic fibre covered

by thin layers of foam

Polyamidefiber

Dielectric constant

1,85 1,25

Loss tangent 0,015 0,019

P. Salonen, et. al, ‘Effect of Textile Materials on Wearable Antenna Performance: A Case

Study of GPS Antennas,’ IEEE AP-S, pp. 459-462, 2004.

C. Hertleer et. al. ‘Aperture-Coupled Patch Antenna for Integration Into Wearable

Textile Systems, IEEE AWPL vol. 6, p. 392-395, 2007.

F. Declercq, et al. ‘Permittivity and Loss Tangent Characterization for Garment Antennas

Based on a New Matrix Pencil Two-Line Method,’ IEEE T-AP vol. 56, no. 8,

pp. 2548-2554, Aug. 2008

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Flexible Substrates

Conductive Textiles· FlecTron, Zelt, ShiedIt, Global EMC

· ShieldIt has adhesive backing(can be glued, stitched, sewn, ironed to substrate)

· Surface Resistivity (0.02-0.05 Ohm/sq)

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Integration

Possibilities

• Smart textiles

• MEMS (sensors)

• Hybrid harvesting modules

• Organic electronics

Challenges

• Washability, Strechability, User comfort, Conformal shape

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Integration

Shad Roundy, Brian P. Otis, Yuen-Hui Chee, Jan M. Rabaey, Paul Wright, A 1.9GHz RF Transmit Beacon

using Environmentally Scavenged Energy IEEE Int. Symposium on Low Power Elec. and Devices, 2003,

Seoul, Korea.

M. Tanaka, R. Suzuki, Y. Suzuki, K. Araki, "Microstrip antenna with solar cells for microsatellites," IEEE

International Symposium on Antennas and Propagation (AP-S), vol. 2, pp. 786-789, 20-24 June 1994.

S. Vaccaro, J.R. Mosig, P. de Maagt , Two Advanced Solar Antenna “SOLANT”

Designs for Satellite and Terrestrial Communications, IEEE Transactions on Antennas and Propagation,

vol. 51, no. 8, Aug. 2003, p. 2028-2034

Solar / Electromagnetic

harvester

1.9GHz/-1.5 dBm

Transmitter

2.4x3.9 cm2

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Integration

• Textile /flexible foam passive and active circuit integration.

• Wearable smart fabric with sensing and communication (transmission) capabilities.

F.Declercq, A. Georgiadis and H. Rogier, ‘Wearable Aperture-Coupled Shorted Solar Patch Antenna

for Remote Tracking Applications,’ EuCAP, Rome, April 2011.

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Integration

Solar / Electromagnetic

harvester

• Ultra-wideband rectenna /

solar harvester

• Reconfigurable bands,

Multiband design

• Measurements under

bended conditions

• Propagation

environments

A. Georgiadis, A. Collado, S. Via and C. Meneses, "Flexible Hybrid Solar/EM Energy

Harvester for Autonomous Sensors", in Proc. 2011 IEEE MTT-S Intl. Microwave

Symposium (IMS), Baltimore, US, June 5-10, 2011.

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42 RF to DC conversion efficiency optimization: Dual-Band Case

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43 RF to DC conversion efficiency optimization: Broadband Case

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Integration

Solar powered

Active oscillator antenna

• Beacon signal generator

• Coplanar folded slot antenna

• Dissipates 9 mWMultiband design

• Solar cell capable to provideup to 60 mW

• 927 MHz operation

Francesco Giuppi, Apostolos Georgiadis, Selva Via, Ana Collado, Rushi Vyas,

Manos M. Tentzeris and Maurizio Bozzi , ‘A 927 MHz Solar Powered Active Antenna

Oscillator Beacon Signal Generator, ‘ RWW 2012, Santa Clara.

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Solar Beacon Signal Generator

• 927 MHz beacon signal

• Active antenna oscillator

• Solar powered

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Solar Beacon Signal Generator

• 920 MHz beacon signal

• Active antenna oscillator

• PET substrate

• Solar powered

A. Georgiadis, A. Collado, S. Kim, H. Lee, M. M. Tentzeris, ‘UHF Solar Powered Active Oscillator Antenna on Low Cost Flexible Substrates for Wireless Identification Applications,’ to appear at MTT-S IMS 2012.

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Solar Beacon Signal Generator

Frequency (M

Hz)

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Solar Passive RFID Tag

A. Georgiadis and A. Collado, ‘Improving Range of Passive RFID Tags Utilizing Energy Harvesting and High Efficiency Class-E Oscillators,’ to appear at EuCAP 2012

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• Proof of concept: RFID tag and wireless

power transmission

• Using Impinj reader

and RF signal generator

− Read rate improvement

− Saturation

Performance Evaluation

860 862 864 866 868 8700

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Freq (MHz)

Read rate (%)

Read rate (%)

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• Using Impinj reader and oscillator

• Measured 3 dBm less

reader power for

maximum read rate

Performance Evaluation

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51Signal Waveform Design for Improved Efficiency

• Improved RF to DC conversion efficiency when using chaotic signals.

Output power (dbm)

433 MHz chaotic generator

A. Collado, A. Georgiadis, "Improving Wireless Power Transmission Efficiency Using Chaotic Waveforms," to appear at IEEE MTT-S IMS 2012, Montreal, 17-22 June 2012.

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rectifier circuit with optimized efficiency at 433 MHz

• Total power of 1-tone signal selected to be equal to the chaotic signal total power in the bandwidth of the rectifier

Signal Waveform Design for Improved Efficiency

Output power (dbm)

A. Collado, A. Georgiadis, "Improving Wireless Power Transmission Efficiency Using Chaotic Waveforms," to appear at IEEE MTT-S IMS 2012, Montreal, 17-22 June 2012.

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− DC voltage for the 1-tone signal is 0.76V (46% RF to DC conversion efficiency)

− DC voltage for chaotic signal is 0.91 V (66% RF to DC conversion efficiency)

Signal Waveform Design for Improved Efficiency

Input power = -6.5 dBm

A. Collado, A. Georgiadis, "Improving Wireless Power Transmission Efficiency Using Chaotic Waveforms," to appear at IEEE MTT-S IMS 2012, Montreal, 17-22 June 2012.

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Energy Harvesting - Example

• Harvester output: 2.5V, 0.5mA (1.25mW)

• Required TX Pulsed transmission: 2.5 V, 20mA (50mW), with a pulse duration of T = 10 ms.

• Maximum duty cycle: DC = 100*1.25/50 = 2.5%

• Burst rate: T/DC = 0.01/0.025 = 0.4sec or 2.5Hz

• If harvester output is 10 uW => Burst rate 50 sec

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Power Management

Voltage Regulators –Storage Units

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Summary

• Energy Harvesting Technologies

• Low cost, flexible materials and fabrication techniques

• Hybrid harvesting systems and integration

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ACKNOWLEDGEMENT:

Work supported by

EU COST Action IC0803 RFCSET

http://www.cost-ic0803.org/

EU Marie Curie project

SWAP, FP7 251557

http://www.fp7-swap.eu/

http://fp7-swap.eu/

http://www.cost-ic0803.org/

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Questions?

Upcoming events:

IEEE MTT-S IMS2013, Seattle, June 2-7, 2013

Technical Area 32: RFID Technologies

Deadline for paper submission: 10 Dec 2012

www.ims2013.org

IEEE MTT-S Wireless Power Transfer Conference (WPTC )

Perugia, 15-16 May 2013

Deadline for paper submission: 12 Jan 2013

www.ieee-wptc2013.unipg.it