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RadarSignaturesofSmallConsumerDrones
ChenchenJ.LiandHao LingTheUniversityofTexasatAustin
1
• The proliferation of small consumer drones has raisedmuch recent interest in their regulation and monitoring.
• One potential way to detect and identify these drones isusing a ground-based radar.
• Objective: To investigate the radar signatures of thesesmall drones.
2
MotivationandObjective
DJIPhantom 3DRSolo DJIInspire
• Carryoutlaboratorymeasurementofsmallconsumerdrones.• Examinetheirradarsignaturesintheformofinversesynthetic
apertureradar(ISAR)images.• ISARimagingprovidesnotonlyradarcrosssection(RCS),but
alsomapsthedominantscatteringin2-D.
ScientificQuestions:1. Willthesmallsizeandlowreflectivityofthedronebody
resultinaverylowRCS?2. Willthespinningpropellerbladesresultinsignificant
Dopplerartifacts[1]?
3
Approach
[1]P.Pouliguen etal., IEEETrans.AntennasPropagat.,2002.
• Vectornetworkanalyzer(VNA)S11 measurement.• Dronemountedandrotatedonaturntable.• Startwithbaselinescenarioandthendeviate.• CalibratedresultsintermsofabsoluteRCSusinga
calibrationsphere.• Hornmismatchandroomclutterarereducedby
subtractingthemovingaverage.• 3GHzofbandwidth.
– 5cmofdown-rangeresolution.
4
LaboratoryMeasurementSetup
• 2-Dimagegeneratedusing2-DinverseFouriertransformoffrequency/angledata.
• Angularswathchosenforequaldown-range/cross-rangeresolutionof5cm.
• SlideswathalongangletogenerateanISARmovie.
5
ISARImageFormation
Polar->Rect.2-DIFFT
Frequencyresponse
Freq
uency
RotationAngle(orTime)
ISARimage
Down-range
Cross-range
Swath
𝐼𝑚𝑎𝑔𝑒 𝑟, 𝑐𝑟 =1
𝐾,𝐾-.𝐸0 𝑓, ϕ
�
�𝑒4567𝑒45897𝑑𝑘,𝑑𝑘-
𝑤ℎ𝑒𝑟𝑒𝑘, =
4𝜋𝑓𝑐 cos ϕ
𝑘- =4𝜋𝑓𝑐 sinϕ
• DJIPhantom2(35cmdiagonal).• Azimuthscanatzero-elevationangle:resultsinatop-viewof
thedrone.• 12-15GHz,bladesstationary,VV-pol,nocamera.
6
BaselineScenario
θ"#θ$%
ISARmovieavailableat:http://users.ece.utexas.edu/~ling/DroneISARMovie.gif
• ISARimagesnapshotsatdifferentlookangleswithanoutlineofdroneoverlaid.
• MaximumRCSineachsnapshotislisted.
7
ISARSnapshots
Max=-13.8dBsm
EL=0°,AZ=8°
Max=-19.4dBsm
EL=0°,AZ=45°
Max=-9.3dBsm
EL=0°,AZ=90°
Max=-18.8dBsm
EL=0°,AZ=135°
Max=-16.3dBsm
EL=0°,AZ=172°
8
DeviationsFromBaseline
BaselineScenario
BladesSpinning
FrequencyChange
PolarizationChange
MountedCamera
ElevationScan
LargerDrones
• Nosignificantdifferencesbetweenbladesrotatingandstationary.
• Onaverage,RCSat3-6GHzabout~12dBlowerthan12-15GHz.
9
DeviationsFromBaseline
Max=-14.6dBsm
EL=0°,AZ=102°
Max=-15.3dBsm
EL=0°,AZ=102°
BladesStationary BladesSpinning
Max=-17.2dBsm
EL=0°,AZ=194°
Max=-27.5dBsm
EL=0°,AZ=194°
12-15GHz 3-6GHz
Rotatin
gBlades
Freq
uencyCh
ange
• HH-Pol:weakerbatteryreturn,strongermotorreturn.
• Cameracanonlybeseenatspecificlookangles.
10
DeviationsFromBaseline
Max=-12.0dBsm
EL=0°,AZ=60°
Max=-12.0dBsm
Camera
EL=0°,AZ=60°
WithoutCamera WithCamera
Max=-13.5dBsm
EL=0°,AZ=6°
Max=-15.3dBsm
EL=0°,AZ=6°
VV-Pol HH-Pol
PolarizationCh
ange
CameraMou
nted
• Elevationscan insteadofazimuthscan.• Capturestheshapeofthedroneinanotherimagingplane.• Insteadoftop-viewofthedrone,capturedtheside-view.• Inpractice,collectedbyflippingdroneonitssideandrotating.
11
DeviationsFromBaseline
Max=-9.0dBsm
EL=-90°,AZ=0°
Max=-9.3dBsm
EL=0°,AZ=90°
AzimuthScan ElevationScan
• Droneshapeandsizecaptured.
• MaximumRCSsmallerthanPhantom2duetobodyshape.
• SimilartrendsasPhantom2.
12
LargerDrones:3DRSolo3DRSolo(46cmdiagonal)
Max=-14.1dBsm
EL=0°,AZ=90°
12-15GHz
Max=-24.2dBsm
EL=0°,AZ=90°
3-6GHz
• Droneshapeandsizecaptured.
• Additionalfeaturefromthehorizontalframe.
• HighestmaximumRCSofthethreedrones.
• SimilartrendsasPhantom2and3DRSolo.
13
LargerDrones:DJIInspire1DJIInspire1(56cmdiagonal)
Max=-3.0dBsm
EL=0°,AZ=270°
12-15GHz
Max=-13.7dBsm
EL=0°,AZ=270°
3-6GHz
• OverallRCSlevelislow,butthedronesizeandshapecanbecaptured intheISARimagery.
• Non-plasticportionsdominatetheirradarsignatures(suchasmotors,batterypack,andcarbon-fiberframe).
• Dronepropellersdidnotcontributeasignificantreturnrelativetothedronebody(staticorspinning).
• Datacollectionwasunderidealizedconditions,butitshouldbefeasibletocollectsuchdatafromanactualdroneinflight.
• Next:Carryoutin-flightmeasurementofthesmalldrone.• ScientificQuestion:CanfocusedISARimagesbegenerated
fromthesesmalldronesinflight?
14
Recap
• PulsON 440(P440)ultra-wideband(UWB)radarbyTimeDomainCorporation.
• Emitsshortpulsesatapulserepetitionfrequencyof10MHz.
• Equivalentfrequencybandwidthfrom3.1to5.3GHzcenteredat4.3GHz.
15
In-SituMeasurementUsingaUWBRadar
• MeasurementsetuponthegroundincludesP440radar,circulator,andsinglehornantenna.
• Phantom3Adv.isusedsinceithasextractableGPSflightdata.• Collectrangeprofiles(at100Hz) asthedronefliesbyina
straightline.
16
In-FlightMeasurementSetup
• Motioncompensationisnecessarytoremovetranslationalmotionandretainonlytherotationalmotion.
• Imagesgeneratedthroughblindmotioncompensation(alignmentoftheRCScentroid).
• Baselineimagesalsogeneratedwithaidfrom“groundtruth,”GPSflightdata.
• Angleestimatebasedonϕ = cosGH(𝑅/𝑅LMN).Imagesformedusingsamek-spaceimagingasbefore.
17
MotionCompensation
Dow
n-ra
nge
(m)
Time (s)
0.5 1 1.5 2 2.5 3
7.5
8
8.5
9
9.5
10
10.5
11
-30
-25
-20
-15
-10
-5
0
Dow
n-ra
nge
(m)
Time (s)
0.5 1 1.5 2 2.5 3-2
-1.5
-1
-0.5
0
0.5
1
1.5
2
-30
-25
-20
-15
-10
-5
0
RawRangeProfiles AfterMotionComp.
• Imagesobtainedfromblindmotioncompensationareon-parwithimagesobtainedfromGPS-assistedmotioncompensation.
• Imagesarefocusedbutnarrowerbandwidthofradarandlimitednumberofscatterers onthedronemakeitchallengingtodiscerntheshape.
18
Phantom3Adv.ResultsGPS-AssistedMotionCompensation
AZ=270°
BlindMotionCompensation
AZ=270°
19
LargerDrone:DJIInspire1
ISARmovieavailableat:http://users.ece.utexas.edu/~ling/DroneISARMovie_Inspire.gif
20
ComparedtoLaboratoryMeasurement
AZ=270°
LabMeas.(3-6GHz)
Max=-13.7dBsm
EL=0°,AZ=270°
In-SituMeas.(3.1-5.3GHz)
Imagesafterblindmotioncompensationarecomparabletothoseobtainedinlaboratorymeasurement.
21
ComparedtoPhantom3
AZ=270°AZ=270°
In-situMeas.Phantom3In-situMeas.Inspire1
Sizedifference,fromPhantom3,isobserved.
• ISARimagescancapturethedroneshapeandsizedespiteitssmallsizeandlowreflectivity.
• SpinningpropellersdonotcontributesignificantDopplerclutter.
• Focusedimagescanbegeneratedfromin-flightmeasurement.
• Radarisapotentialcandidatefortrackingandclassificationofsmallconsumerdrones.
22
Conclusion
23
Acknowledgment
ColtonBostick ofUAVDirectandLennyTropiano ofFlyTheSkyDrone Productionsforprovidingdronesformeasurement.
AlanPetroffofTimeDomainCorporationfortechnicalsupportontheultra-widebandradar.
ThisworkwassupportedinpartbytheNationalScienceFoundationunderGrantECCS-1232152.
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