Through-Wall Radar Imaging

1November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYThrough-WallRadarImagingRFAllianceConferenceEWandAntennaCommunicationApplicationsRobertJ.BurkholderResearchProfessorTheOhioStateUniversityElectroScienceLaboratoryDept.ofElectricalandComputerEngineering(113.132.110.12)-2016/3/29Download2November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYOutline1.Introductiontothrough-wallradarimaging2.Wallmodelingandmitigation3.New“snapshot”imagingsystemApplications:–Covertsurveillance–Hiddenobjectdetection–Buildinglayouts–Non-destructivetesting–SearchandrescueSceneunderinterrogation“VisiBuilding”(113.132.110.12)-2016/3/29Download3November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORY1.IntroductiontoThrough-WallRadarImageProcessing•Radarimagingofagivensceneisessentiallyaninverseproblem.•Asetofdataiscollected,usuallybysteppingthrougharangeoffrequenciesandantennapositions.•Aforwardmodelisassumedtorelatetheobserveddataandthescene.•Informationisextractedfromthescene,oravisualimageisobtained,byapplyinganinversionordeconvolutionalgorithm.•Theresolutionoftheimageisdependentonthesamplingofthedata,theaccuracyoftheforwardmodel,thedeconvolutionalgorithm,andnoise.SceneunderinterrogationSetofsensorsorasinglemovingsensor(113.132.110.12)-2016/3/29Download4November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYIntroduction(cont’d.)•The“reflectivitydensity”σdisdefinedasthescatteringfromaninfinitesimalpointinthesceneofinterest.•Forwardmodel:Thereceivedsignalplusnoise(orclutter)asafunctionoffrequencyf(ortime)isgivenasanintegralovertheentirescenebeingscannedas:whereGistheGreen’sfunctionfortheenvironmentofinterest.Basicinverseimagingfunction:dffSrrfGrnnnd)(),,()(~1nthsensoratrnSceneunderinterrogationσdG)(')'(),',()(fNdVrrrfGfSdnn(113.132.110.12)-2016/3/29Download5November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYExample:FreeSpaceGreen’sFunctionforMonostaticScattering•Conjugate-phase,orconventionalback-projectionalgorithm:•Theimagingfunction|σd|peaksatastrongscattererwhen•Notethatthemagnitudetermmayormaynotbeusedtocompensateforthespreadingloss.dferrfSrnrrkjnndn||22)()(~2|'|2|'|4),',(nrrkjnrrerrfGnSceneunderinterrogationσdG|'|nrr'rr(113.132.110.12)-2016/3/29Download6November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORY2.WallModelingandMitigation(113.132.110.12)-2016/3/29Download7November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYPeriodicWalls•Planewavetransmissionthroughaperiodicstructuregivesrisetoadiscretesetofplanewaves(Floquetmodes)propagatingatanangleθmdefinedby,•Modesarepropagatingif•Periodicmomentmethodorfiniteelement/boundaryintegralmethodusedtocomputetransmissionandreflection.kdmm2sinsin,...2,1mθIncidentplanewaveFloquetplanewavesSpeculartransmittedplanewaveCinderblockwallθmdcfk/21|sin|m(113.132.110.12)-2016/3/29Download8November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORY3-LayerAnalyticModelforCinderblockWalls**C.L.Holloway,P.L.Perini,R.R.DeLyser,andK.C.Allen,“AnalysisofCompositeWallsandTheirEffectsonShort-PathPropagationModeling,”IEEETrans.AntennasandPropagation,vol.46,no.3,pp.730–738,August1997.•Theperiodicinnerlayerisreplacedbyanequivalenthomogeneousdielectriclayer.(113.132.110.12)-2016/3/29Download9November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYComparisonBetween3-LayerModelandPeriodicModelsforTransmission•Cinderblockwall,normalincidence•3-layermodelisaccurateuptoabout900MHzinV-poland1500MHzinH-pol•PhasedistortionisminorforH-polupto2GHzFirstFloquetmodecut-offSecondFloquetmodecut-offFirstFloquetmodecut-offSecondFloquetmodecut-offVerticalpolarizationHorizontalpolarizationTransmission(dB)Phase(deg)(113.132.110.12)-2016/3/29Download10November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYCinderblockWallTransmissionExperiment•Hornantennas3feetfromwall.•Numericalandanalyticresultsassumeplanewaveincidence.•Cinderblocksappeartocauseenhancedtransmissionatsomefrequencies.Thismaybeanear-fieldfocusingeffect.V-polH-pol16”4”7.6”05.05.4jr(113.132.110.12)-2016/3/29Download11November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYLatetimedampedsinusoidforcinderblockVerylittleringinginlatetimefor3-layermodelVIE-PMMsolutionEarlytimeagreesDownrangeEffectsofCinderBlock•Cinderblockcausesdownrangeringingintheimagedomain.CinderblockwallEquivalent3-layermodel•Backscatter,Verticalpolarization•Infinite2Dgeometry(113.132.110.12)-2016/3/29Download12November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYWallModelingforMitigation•Forwardmodel:•Model-basedimagingfunction:)('|'|4),'(),()()(2|'|222kNdVrrekrkTekRkSnrrkjdwkrjwnnwnrrkjkrjwnwddkeekRkSkTrnw||2212)()(),()(~σdwRwTθnWallreflectionScatteringfrominteriorNoise/clutterRemovesdistortionRemoveswallscattering(113.132.110.12)-2016/3/29Download13November6,2009THEOHIOSTATEUNIVERSITYELECTROSCIENCELABORATORYSimulatedImagesofTwoPointScatterers•1.8to2.2GHz,verticalpolarization•-12°to12°azimuthscan•Pointsat(x,y)=(2,1)and(3,2)•NormalizedlinearcolorscaleθPointlocationsFreeS