Ambient RF-energy harvesting at 900 MHz

97 Pages·2016·6.82 MB·English

by  Fredrik S Brynhildsvoll

Ambient RF-energy harvesting at 900
MHz
Fredrik S Brynhildsvoll
Master of Science in Electronics
Submission date: July 2016
Supervisor: Morten Olavsbråten, IET
Co-supervisor: Torolv Skjølsvik, Nordic Semiconductor
Johannes Skaar, IET
Norwegian University of Science and Technology
Department of Electronics and Telecommunications

i
Preface and acknowledgments
ThisthesisiswrittenasapartofthedegreeofMasterofScience(MSc)attheDepartmentofElec-
tronics and Telecommunications, Norwegian University of Science and Technology (NTNU). The
work was carried out in the spring of 2016 under the supervision of associate professor Morten
Olavsbråten (NTNU) and Torolv Skjølsvik (NordicSemiconductor). The assignment was given by
NordicSemiconductor.
FirstIwouldliketothankMortenOlavsbråtenforallthehelpintheworkofthisthesis. Many
hourshavegoneintodiscussingpossibleapproachesandsimulationresults,andIamverythank-
fulforallthetimespentonthis.
Second I want to thank Torolv Skjølsvik for giving me the opportunity to work with this RF-
harvestingsystem.Yourinsightinotherenergyharvestingsystemshasbeenvaluable.Itisashame
thattherewasnotenoughtimetoseethisharvesterrealised,sinceIknowthatyouwouldappreci-
ateitasmuchasIwould.
IwouldalsoliketothankProfessorJohannesSkaarforthehelpintheworkleadinguptothis
thesis.
Lastly I would like to thank my cohabitant Martine Lund Andresen for holding the fort in the
writingofthisandmynewbornsonBirkforgivingmesomuchjoyandenergyinthesefinalweeks.
Trondheim,July2016
FredrikSundtBrynhildsvoll
ii
Acronyms
ADS Advanceddesignsystem
FET Field-effecttransistor
GSM900 GSMfrequencybandfrom890-960MHz
JFET Junctiongatefield-effecttransistor
MESFET Metal–semiconductorfield-effecttransistor
MOSFET Metal-oxide-semiconductorfield-effecttransistor
RBW Resolutionbandwidth
RF Radiofrequency
RFID Radio-frequencyidentification
WLAN Wirelesslocalareanetwork
iii
Abstract
InthisthesisaRF-energyharvestingsystemabletoharvestambientpowerat900MHz(GSMband)
issimulated. Especiallytheefficiencyatlowpowerisofinterest(-19to-23dBmrectifierinput). A
rectifier and a boost converter is simulated in Advanced Design System (ADS) to determine the
efficiency and output voltage. A power managing circuit able to turn the load (nRF52 chip from
NordicSemiconductor)onwhensufficientpowerisaccumulatedisalsopresented.
Simulations show that a 3-stage rectifier is optimal to maximize efficiency. The efficiency is
32.4%and19.6%atinputpowersof-19dBmand-23dBm. Theoutputvoltagesare435mVand
184mVrespectively.
Theboostconverterissimulatedwithinputpowersfrom-24dBmto-30dBm(outputofrecti-
fier). Itisabletochargeacapacitorto2.5Vatallsimulatedinputpowers. Theefficiencywith2V
outputvoltageis61.7%and52.2%withinputpowersof-24dBmand-30dBm. Sincethelossin
theoscillationnetworkisnotincludedtheseefficienciesareoverestimated.
Thetotalefficiencyis20.0%and10.2%atinputpowersof-19dBmand-23dBm. Itisshown
that the harvester can provide power to the nRF52 chip at input powers down to -21 dBm if the
oscillation network consumes less than 733 nW. With this power consumption, estimates of the
charge time reveal that the load can broadcast air temperatures at intervals of 84 seconds when
the input power is -19 dBm. The interval is 188 seconds and 977 seconds (∼17 minutes) at input
powersof-20dBmand-21dBmrespectively.Iftheoscillationlossislessthan367nWtheharvester
canoperatedownto-22dBm.
iv
Sammendrag
IdennemasteravhandlingensimuleresetRF-energihøstingssystemsomeristandtilåhøsteom-
givende energi ved 900 MHz (GSM bånd). Av spesiell interesse er effektiviteten ved lave effekter
(-19dBmtil-23dBmrefererttilinngangenavlikeretteren). Enlikeretterogenspenningsforsterk-
endekrets(boostconverter)ersimulertiAdvancedDesignSystem(ADS)foråfastslåeffektivitetog
utgangsspenning.Enkretssomgjørenergitilgjengeligforlasten(nRF52mikrokontrollerfraNordic
Semiconductor)nårnokenergierakkumulert,presenteresogså.
Simuleringer viser at tre steg i likeretteren er optimalt for å maksimere effektiviteten. Da er
effektiviteten 32.4 % og 19.6 % ved inngangseffekter på henholdsvis -19 dBm og -23 dBm. Ut-
gangsspenningene er henholdsvis 435 mV og 184 mV ved de samme effektene. Den spennings-
forsterkendekretsenersimulertmedinngangseffekterfra-24dBmtil-30dBm(tilsvarerutgangen
pålikeretterenmedtresteg). Deneristandtilåoppladeenutgangskondensatortil2.5Vvedalle
simulerte inngangseffekter. Effektiviteten med 2 V utgangsspenning er 61.7 % og 52.2 % med in-
ngangseffekterpåhenholdsvis-24dBmog-30dBm. Sidentapidetoscillerendenettverketikkeer
tattmedieffektberegningeneerdetteetoverestimatavdenfaktiskeeffektiviteten.
Totalsystemeffektiviteter20.0%og10.2%vedinngangseffekterpå-19dBmog-23dBm. Det
er vist at høstesystemet kan forsyne lasten ved inngangseffekter ned til -21 dBm dersom effekt-
forbruketidetoscillerendenettverketermindreenn733nW.Meddetteforbruketviserestimater
avoppladningstidenatlastenkankringkastelufttemperaturermedintervallerpå84sekunderved
eninngangseffektpå-19dBm. Intervalleneer188sekunderog977sekunder(∼17minutter)med
inngangseffekterpåhenholdsvis-20dBmog-21dBm. Dersomdetoscillerendenettverketbruker
mindreenn367nWkanhøstesystemetforsynelastenmedinngangseffekterstørreenn-22dBm.
Contents
Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
Abstract. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
1 Introduction 1
1.1 DevelopmentofRF-harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1.1 Wirelessenergytransfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Harvestingsystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 SpecificationsforRF-harvesting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.4 CommerciallyavailableRF-harvestingsystems . . . . . . . . . . . . . . . . . . . . . . . 3
1.5 Thesisstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 TheoreticalBackground 5
2.1 Transientanalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Transistortypes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.3 Theoreticalpowerdensity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.4 Matchingandamplification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3 Theharvestingsystem 13
3.1 Rectifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2 Boostconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.1 Simpleboostconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.2.2 Selfoscillatingboostconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.2.3 Commerciallyavailableboostconverters . . . . . . . . . . . . . . . . . . . . . . . 20
3.3 Storagecapacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
3.4 Powermanagingcircuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4 Spectrummeasurements 27
v
vi CONTENTS
5 Simulations 33
5.1 Rectifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.1.1 Capacitorvalues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.1.2 HSMS-2850linearcircuitmodel . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.1.3 Maximumtheoreticalvoltagegain . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.1.4 Inputimpedanceoftherectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
5.1.5 Simulationswithsetinputimpedance . . . . . . . . . . . . . . . . . . . . . . . . 40
5.2 SimpleDC-DCboostconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.2.1 Selectionofcomponents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
5.2.2 Boostconvertersimulationresults . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
5.2.3 Lossanalysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
5.3 Rectifierandboostconverterperformance . . . . . . . . . . . . . . . . . . . . . . . . . . 52
5.3.1 Chargetimewithrectifier,boostconverterandpowermanagingcircuit. . . . . 52
5.4 Numberofrectifierstagestomaximizeefficiency . . . . . . . . . . . . . . . . . . . . . . 55
6 Discussion 57
6.1 Rectifier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.2 Simpleboostconverter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
6.3 Rectifierandboostconverterperformance . . . . . . . . . . . . . . . . . . . . . . . . . . 63
6.4 Numberofrectifierstagestomaximizeefficiency . . . . . . . . . . . . . . . . . . . . . . 64
7 Conclusion 65
Bibliography 68
A Completecircuitdiagramwithcomponents 73
B Rectifiersimulationstofindinputimpedance 75
C Rectifiersimulationwithinputimpedancesetto1000Ω 77
D Boostconvertersimulationdataandsimulationparameters 81
E Simulationdataofrectifierandboostconverter 83
F Gainoflog-periodicantenna 84
List of Figures
1.1 SystemoverviewoftheRF-harvestingsystem . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1 CrosssectionofaN-channelMOSFET . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.2 CrosssectionofaMESFETtransistor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 JFETcross-sectionsandsymbols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 Matchingnetworkinsertedbetweentheantennaandtherectifier. . . . . . . . . . . . . 11
3.1 SystemoverviewoftheRF-harvestingsystempresented . . . . . . . . . . . . . . . . . . 13
3.2 FullwaveVillardvoltagedoubler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.3 Simpleboostconvertertopology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.4 Idealcurrentsandvoltagesintheboostconverter . . . . . . . . . . . . . . . . . . . . . . 17
3.5 Boostconverterwithloss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.6 Selfoscillatingboostconverter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3.7 Powermanagingcircuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.1 Measuredpowerspectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4.2 Locationofspectrummeasurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
5.1 Rectifiersimulationsetup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.2 HSMS-2850equivalentlinearcircuitmodel . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.3 Rectifiermaximumvoltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
5.4 8-stagerectifierefficiencyandinputimpedanceimpedance . . . . . . . . . . . . . . . 37
5.5 8-stagerectifieroutputvoltageandinputimpedance . . . . . . . . . . . . . . . . . . . . 38
5.6 3-stagerectifierefficiencyandinputimpedanceimpedance . . . . . . . . . . . . . . . 39
5.7 3-stagerectifieroutputvoltageandinputimpedance . . . . . . . . . . . . . . . . . . . . 40
5.8 Theveninequivalentofrectifier . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
5.9 Efficiencyofn-stagerectifiers(1000Ω) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
vii