Antenna System for Tracking of Unmanned Aerial Vehicle

93 Pages·2014·22.13 MB·English

Antenna System for Tracking of
Unmanned Aerial Vehicle
Lars-Eirik Dalbakk
Electronics System Design and Innovation
Submission date: June 2014
Supervisor: Egil Eide, IET
Norwegian University of Science and Technology
Department of Electronics and Telecommunications

Summary
Targettrackingisacriticalpartofanymobilecommunicationsystemwithadirectivere-
ceiverantenna. Somepopulartrackingmethodsusethedetectedphasedifferencebetween
signalsreceivedbyseveralantennastofindthesignal’sdirectionofarrival. Themeasured
direction of arrival is used to adjust the directive antenna’s radiation pattern towards the
transmitter. Thus,theradiolinkbetweenthereceiverandthetransmitteriskeptoptimalat
alltimes.
Thisthesispresentsthedesignandimplementationofatrackingsystem,thatisbasedon
thephasedifferencebetweenaQPSKmodulatedsignalreceivedattwodistinctantennas.
The objective of the tracking system were to improve the existing radio link at Andøya
Rocket Range, and have a range of 20 km. For this system, the direction of arrival was
measuredbetween60◦and120◦angleofarrival,allowingamaximumestimateddirection
ofarrivalerrorof2◦. ThetrackingalgorithmwasimplementedinNILabVIEW,withtwo
universalsoftwareradioperipheralsasreceivers.
Accuracy measurements of the tracking system were taken in an anechoic chamber, for
differentpowerspecifications. Withareceivedpowerof-45.9dBmandhigher,themea-
sureddirectionofarrivalerrorvariedbetween0◦to2◦,fulfillingtheaccuracyrequirement.
Atareceivedpowerof-56dBm,theerrorwasbetween2◦to7◦.Althoughitdidnotfulfill
theaccuracyrequirement,theestimationwasstillwithinthehalfpowerbeamwidthofthe
directive receiver antenna. Thus it was defined as the lower power limit for a function-
ing tracking system. Assuming that there are no interference or loss due to reflections
in the channel, the maximum range of the tracking system is 680 m. Hence, the range
requirementof20kmarenotfulfilled.
i
Sammendrag
Ma˚lfølgingerenviktigdelavethvertmobiltkommunikasjonssystemsombrukerdirektive
antenner. Noenpopulærema˚lfølgingsmetoderma˚lerfaseforskjellenmellometsignalsom
ermottattavtoellerflereantenner. Dersomfaseforskjellenerkjent,kanankomstvinkelen
tilsignaletberegnes. Fora˚oppna˚optimalradiolinkmellomsender-ogmottakerantennen,
ma˚ stra˚lingsdiagrammet til mottakerantennen rette seg inn etter den beregnede ankom-
stvinkelen.
Denne oppgaven presenterer et design av et ma˚lfølgingssystem, og hvordan det er im-
plementert. Ma˚lfølgingssystemet er basert pa˚ a˚ finne faseforskjellen mellom et QPSK
modulert signal som er mottatt av to antenner. Hensikten med ma˚lfølgingssystemet er a˚
forbedreeneksisterenderadiolinkpa˚ Andøyarakettskytefelt,slikatdetkanhaenrekke-
viddepa˚20km.Ankomstvinkelentilsignaletblema˚ltietomra˚depa˚60◦til120◦,hvor90◦
errettpa˚mottakerantennene.Detblestiltkravomatnøyaktighetentilma˚lfølgingssystemet
skulleværeinnenfor2◦. Ma˚lfølgingsalgoritmenbleimplementertiNILabVIEW,medto
USRPersommottakere.
Systemetsnøyaktighetblema˚ltforforskjelligmottatteffektietekkofrittrom. Ma˚lefeilen
var pa˚ mellom 0◦ til 2◦ med mottatt effekt pa˚ -45.9 dBm og høyere. Men med en mot-
tatteffektpa˚ -56dBmvarma˚lefeilenmellom2◦ til7◦. Selvomma˚lingeneikkevarhelt
innenforkravet,vardefremdelesinnenfor3-dB-ba˚ndbreddentilmottakerantennenikom-
munikasjonssystemet. Derfor ble -56 dBm mottatt effekt definert som minimumskravet
for at ma˚lfølgingssystemet skulle fungere. Hvis det antas at det ikke er noe tap i signal-
styrkepa˚ grunnavinterferensellerrefleksjoner,sa˚ errekkeviddentilsystemet680meter.
Deravbleikkekravetomrekkeviddepa˚ 20kminnfridd.
ii
Preface
Thisthesisissubmittedinfulfillmentoftherequirementsforthedegreeofmasterofsci-
ence (MSc) at the Department of Electronics and Telecommunications, Norwegian Uni-
versityofScienceandTechnlogy(NTNU).TheworkwascarriedoutintheperiodJanuary
2014toJune2014,underthesupervisionofAdjunctAssociateProfessorEgilEide.
Acknowledgment
IwouldliketothankmysupervisorEgilEide,forgivingmetheopportunitytoworkwith
antennasandcommunicationsystems,andforprovidingmewithinsighttoproblemsen-
counteredinthethesis.
IwouldalsoliketothankSeniorEngineerTerjeMathiesen,forhelpingmefindtheright
equipment,andforassistingmewithmeasurementsintheanechoicchamber. Andlastbut
not least, I would like to thank my fellow students and friends for valuable input during
thisperiod. IwouldespeciallyliketothankMathiasTømmerformanyenlighteningcon-
versatons.
Trondheim,Norway,June2014
Lars-EirikDalbakk
iii
iv
Table of Contents
Summary i
Sammendrag ii
Preface iii
TableofContents vi
ListofTables vii
ListofFigures xi
Abbreviations xii
1 Introduction 1
1.1 StructureoftheReport . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2 TheoreticalBackground 5
2.1 TheMobileRadioChannel . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.1 FreeSpacePropagation. . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2 MultipathFading . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1.3 PlaneEarthLossModel . . . . . . . . . . . . . . . . . . . . . . 8
2.2 SystemSensitivityLimit . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.3 EarthBulge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2.4 PhaseMeasurementErrorduetoNoise. . . . . . . . . . . . . . . . . . . 12
3 TrackingMethods 15
3.1 DirectionofArrival . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.2 Delay-And-SumMethod . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.3 MUSIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.4 CarrierRecoverybyCostasLoop. . . . . . . . . . . . . . . . . . . . . . 17
v
4 SystemDesign 19
4.1 ReceiverandTransmitterSystem . . . . . . . . . . . . . . . . . . . . . . 19
4.2 SignalPropagationandLinkBudget . . . . . . . . . . . . . . . . . . . . 22
5 SoftwareDevelopment 29
5.1 EquipmentandTools . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5.2 SoftwareDesignSetup . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
5.3 ChoiceofTrackingMethod . . . . . . . . . . . . . . . . . . . . . . . . . 33
5.4 LabVIEWCode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.4.1 CodeOverview . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
5.4.2 CodeImplementation . . . . . . . . . . . . . . . . . . . . . . . . 35
5.4.3 CodeVerification . . . . . . . . . . . . . . . . . . . . . . . . . . 40
6 TrackingSystemMeasurements 43
6.1 MeasurementSetup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
6.2 MeasurementsandResults . . . . . . . . . . . . . . . . . . . . . . . . . 47
7 Discussion 57
8 Conclusion 61
8.1 RecommendationsforFurtherWork . . . . . . . . . . . . . . . . . . . . 62
Bibliography 63
Appendix 65
vi
List of Tables
4.1 Radiolinkspecifications . . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.2 Link budget for the radio link with the 18 dBi reflector antenna as the
receivingelement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
4.3 Themostimportantpropertiesoftheradiolinkstothemainreceiveran-
tenna,andthetrackingantennainrealenvironment. . . . . . . . . . . . . 27
5.1 Softwaredevelopmentequipment. . . . . . . . . . . . . . . . . . . . . . 32
5.2 Measuredphasedifferenceofthesignalsindegrees . . . . . . . . . . . . 41
6.1 Linkbudgetfortrackingantennasintheanechoicchamber . . . . . . . . 46
6.2 MeasuredDOAofthesignalsindegreesasafunctionofreceivedpower
attheUSRPterminals. . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
8.1 Linkbudgetfortrackingantennasinrealconditions,with1Wtransmitted
power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
8.2 Linkbudgetfortrackingantennasinreflection-andinterferencefreecon-
ditions,with1Wtransmittedpower . . . . . . . . . . . . . . . . . . . . 71
8.3 Newlinkbudgetfortrackingantennasinreflection-andinterferencefree
conditions,with1Wtransmittedpower . . . . . . . . . . . . . . . . . . 72
8.4 SNRcalculationsforsignalswithdifferentreceivedpower. . . . . . . . . 73
vii
viii