简介：根据双站合成孔径雷达飞行平台的运动特点，分析了随机扰动误差对双站正侧视SAR成像的影响，推导出了载体平台沿理想航线方向扰动和横向扰动情况下的图像位移准则和分辨率准则，以及振动情况下控制图像对比度损失的限制条件，并对这些结果进行了分析，得出了相关结论，这对双站SAR的工程实践具有重要的指导意义。

简介：Specklefilteringofsyntheticapertureradar(SAR)imageswhilepreservingthespatialsignalvariability(textureandfinestructures)stillremainsachallenge.ManyalgorithmshavebeenproposedfortheSARimagerydespeckling.However,simulatedannealing(SA)methodisoneofexcellentchoicescurrently.AcriticalprobleminthestudyonSAistoprovideappropriatecoolingschedulesthatensurefastconvergencetonear-optimalsolutions.Thispapergivesanewnecessaryandsufficientconditionforthecoolingschedulesothatthealgorithmstateconvergesinallprobabilitytothesetofgloballyminimumcoststates.Moreover,itconstructsanappropriateobjectivefunctionforSARimagedespeckling.AnexperimentalresultoftheactualSARimageprocessingisobtained.

简介：ThereisdifficultyfordistinguishingofriverandshadowinSyntheticApertureRadar(SAR)images.AmethodofriversegmentationinSARimagesbasedonwaveletenergyandgradientisproposedinthispaper.Itmainlyincludestwoalgorithms:coarsesegmentationandrefinedsegmen-tation.Firstly,Theriverregionsarecoarselysegmentedbythewaveletenergyfeature,andthenrefinedsegmentedaccuratelybythegradientthresholdwhichisgotadaptively.Theexperimentalresultsshowthevalidityofthemethod,whichprovidesagoodfoundationfortargetsdetectionabovetheriver.

简介：ThemathematicalmodelofspaceborneSARsystemsanditscomputersimulationsaredescribed.Resultsofcomputersimulationsaboutrangemigration,rangemigrationcorrection,azimuthweightingandsignalgeneration/processingaregiven.ThissoftwarecanbeusedtosimulatethedynamicprocessesinspaceborneSARsystems,todevelopnewsignalprocessingtechniquesandtoevaluatetheperformanceofthedesignedsystem.

简介：ThispaperstudiesSyntheticApertureRadar(SAR)imagescontaminatedbythecoherentspecklenoisewiththemultiresolutionanalysisofwavelettransform.ThisstudyshowsthattheinfluencesofthespeckleondifferentfrequencycomponentsoftheSARimagearedifferent,andthattheSARimageandthespecklehavedifferentmannersofsingularity.So,thispaperpresentsadenoisingmethodofwaveletanalysistoreducethespeckle.Someexperimentsapprovethatthismethodnotonlysuppressesthespeckleeffectively,butalsopreservesasmuchtargetcharacteristicsoftheoriginalimageaspossible.ItshowsthatthisdenoisingmethodofwaveletanalysisoffersaveryattractivealternativetosuppressthecoherentspecklenoiseoftheSARimage.

简介：Whentheclassicalconstantfalse-alarmrate(CFAR)combinedwithfuzzyC-means(FCM)algorithmisappliedtotargetdetectioninsyntheticapertureradar(SAR)imageswithcomplexbackground,CFARrequiresblock-by-blockestimationofcluttermodelsandFCMclusteringconvergestolocaloptimum.Toaddresstheseproblems,thispaperpro-posesanewdetectionalgorithm:knowledge-basedcombinedwithimprovedgeneticalgorithm-fuzzyC-means(GA-FCM)algorithm.Firstly,thealgorithmtakestargetregion’smaximumandaverageintensity,area,lengthoflongaxisandlong-to-shortaxisratiooftheexternalellipseasfactorswhichinfluencethetargetappearingprobability.Theknowledge-baseddetectionalgorithmcanproducepreprocessresultswithouttheneedofestimationofcluttermodelsasCFARdoes.AfterwardtheGA-FCMalgorithmisimprovedtoclusterpre-processresults.IthasadvantagesofincorporatingglobaloptimizingabilityofGAandlocaloptimizingabilityofFCM,whichwillfurthereliminatefalsealarmsandgetbetterresults.TheeffectivenessoftheproposedtechniqueisexperimentallyvalidatedwithrealSARimages.

简介：ThisletterstudiesonthedetectionoftexturefeaturesinSyntheticApertureRadar(SAR)images.ThroughanalyzingthefeaturedetectionmethodproposedbyLopes,animprovedtexturedetectionmethodisproposed,whichcannotonlydetecttheedgeandlinesbutalsoavoidstretchingedgeandsuppressinglinesoftheformeralgorithm.ExperimentalresultswithbothsimulatedandrealSARimagesverifytheadvantageandpracticabilityoftheimprovedmethod.

简介：MultistageVectorQuantization(MSVQ)canachieveverylowencodingandstoragecomplexityincomparisontounstructuredvectorquantization.However,theconventionalMSVQissuboptimalwithrespecttotheoverallperformancemeasure.Thispaperproposesanewtechnologytodesignthedecodercodebook,whichisdifferentfromtheencodercodebooktooptimisetheoverallperformance.Theperformanceimprovementisachievedwithnoeffectonencodingcomplexity,bothstorageandtimeconsuming,butamodestincreaseinstoragecomplexityofdecoder.

简介：OptimizationofantennaarraypatternusedinaspaceborneSyntheticApertureRadar(SAR)systemisconsideredinthisstudy.Arobustevolutionaryalgorithm,Non-dominatedSortingGeneticAlgorithms(theimprovedNSGA-Ⅱ),isappliedonaspaceborneSARantennapatterndesign.Thesystemconsistsoftwoobjectivefunctionswithtwoconstraints.Paretofrontsaregeneratedasaresultofmulti-objectiveoptimization.AfterbeingvalidatedbyatestproblemZDT4,thealgorithmsareusedtosynthesizespaceborneSARantennaradiationpattern.ThegoodresultswithlowAmbi-guity-to-SignalRatio(ASR)andhighdirectivityareobtainedinthepaper.

简介：SyntheticApertureRadar(SAR)imagingofoceansurfacefeaturesisstudied.ThesimulationoftheturbulentandvorticalfeaturesgeneratedbyamovingshipandSARimagingofthesewakesiscarriedout.Theturbulentwakedampingtheoceansurfacecapillarywavesmaybepartiallyresponsibleforthesuppressionofsurfacewavesneartheshiptrack.Thevortexpairgeneratingachangeinthelateralflowfieldbehindtheshipmaybepartiallyresponsibleforanenhancementofthewavesneartheedgesofthesmootharea.Thesehydrodynamicphenomenaaswellasthechangesofradarbackscattergeneratedbyturbulenceandvortexaresimulated.AnSARimagingmodelisthenusedonsuchoceansurfacefeaturestoprovideSARimages.Comparisonoftwoships'simulatedSARimagesshowsthatthewakefeaturesaredifferentforvariousshipparameters.

简介：Wavelet-fractalbasedSAR(syntheticapertureradar)imageprocessingisoneoftheadvancedtechnologiesinimageprocessing.Themainconceptofanalysisisthatafterwavelettransformation,multifractalspectrumofthesignalisdifferentfromthatofnoise.ThisdifferenceisusedtoalleviatethenoiseproducedbySARimage.ThemethodtodenoiseSARimageusingtheprocessbasedonwavelet-fractalanalysisisdiscussedindetail.Essentially,thepresentmethodfocusesonadjustingtheHlderexponentαofmultifractalspectrum.Aftersimulation,αshouldbeadjustedto1.72-1.73.Themorethevalueofαexceeds1.73,thelessdistinctivetheedgesofSARimagebecome.Accordingtotheauthorsdenoisingisoptimalatα=1.72-1.73.Inotherwords,whenα=1.72-1.73,asmoothanddenoisedSARimageisproduced.

简介：Withamultiplicativespecklemodel,thispapershowsthemulti-lookpolarimetricsyntheticapertureradar(SAR)dataobeysageneralizedK-distribution.Tovalidatethisdistributionmodel,themulti-lookintensityK-distributionisparticularlytested.Therelationshipbetweentheheterogeneitycoefficientofthesceneandtheproperstatisticalmodelisexperimentallyestablished.Inaddition,basedontheresultsofthestatisticalanalysis,anadaptiveclassificationschemeispresented,andtheimprovedclassificationshowstheimportanceofthestatisticalanalysis.

简介：分析了一种合成孔径雷达有源干扰的新技术——随机脉冲卷积干扰。该干扰技术可以获得雷达距离压缩处理的部分增益，干扰效果明显优于等信噪比情况下的射频噪声压制干扰；它降低了干扰机实现压制干扰的输出功率，大大提高了干扰效率；通过控制随机脉冲的延迟时间和延迟范围，可以控制干扰带的位置和宽度，实现对己方重要分布目标的保护；仿真分析结果验证了该方法的有效性和可行性。

简介：线性调频连续波合成孔径雷达（LFMCWSAR）是一种新近提出来的成像雷达体制，它结合调频连续波与合成孔径成像技术，具有体积小、重量轻、成本低、分辨率高等一系列优点。然而，由于受系统的影响，调频信号的频率和时间并不完全满足线性关系。在详细分析了LFMCW的调频非线性对距离分辨率及FMCWSAR成像质量的影响之后，提出使用分段线性拟合的方法估计调频信号的非线性，并提出了非线性的校正方法，研究了存在非线性时的FMCWSAR成像算法，并给出了仿真结果，验证了该方法的有效性。

简介：Todealwiththenon-Gaussiannoiseinstandard2-DSARimages,thederampedsignalinimagingplane,andthepossiblesymmetricdistributionofcomplexnoise,thefourth-ordercumulantofcomplexprocessisintroducedintoSARtomography.WiththeestimatedARparametersofARMAmodelofnoisethroughYule-Walkerequation,thesignalseriesofheightispre-filtered.Then,throughESPRIT,thespectrumisobtainedandtheapertureinheightdirectionissynthesized.Finally,theSARtomographyimagingofsceneisachieved.Theresultsofprocessingonsignalwithnon-Gaussiannoisedemonstratetherobustnessoftheproposedmethod.Thetomographyimagingofthescenesshowsthatthehigher-orderspectrumanalysisisfeasibleintheapplication.

简介：Bistaticforward-lookingsyntheticapertureradar(SAR)hasmanyadvantagesandapplicationsowingtoitstwodimensionalimagingcapability.Therecouldbevariousimagingconfigurationsbecauseofthegeometricflexibilityofbistaticplatforms,resultinginkindsofmodelsbuiltindependentlyamongwhichtherecouldbesomesimilareventhesamemotionfeatures.Comprehensiveresearchonsuchsystemsinamorecomprehensiveandgeneralpointofviewisrequiredtoaddresstheirdifferenceandconsistency.PropertyanalysisofbistaticforwardlookingSARwitharbitrarygeometryisachievedincludingstripmapandspotlightmodesonairborneplatform,missile-borneplatform,andhybridplatformofboth.Emphasisisplacedonazimuthspacevarianceofsomekeyparameterssignificantlyaffectingthesubsequentimagingprocessing,basedonwhichthefrequencyspectraarefurtherdescribedandcomparedconsideringrespectivefeaturesofdifferentplatformsforfrequencyimagingalgorithmdeveloping.Simulationresultsconfirmtheeffectivenessandcorrectnessofouranalysis.

简介：ThepaperpresentsanalgorithmofautomatictargetdetectioninSyntheticApertureRadar(SAR)imagesbasedonMaximumAPosteriori(MAP).Thealgorithmisdividedintothreesteps.First,itemploysGaussianmixturedistributiontoapproximateandestimatemulti-modalhistogramofSARimage.Then,basedontheprincipleofMAP,whenaprioriprobabilityisbothunknownandlearnedrespectively,thesamplepixelsareclassifiedintodifferentclassesc={target,shadow,background}.Last,itcomparestheresultsoftwodifferenttargetdetections.Simulationresultspreferablyindicatethatthepresentedalgorithmisfastandrobust,withthelearnedaprioriprobability,anapproachtotargetdetectionisreliableandpromising.

简介：Thecoherenceisameasurefortheaccuracyoftheinterferometricphase,andthesyntheticapertureradar(SAR)interferometriccoherenceisaffectedbyseveralsourcesofthedecorrelationnoise.ForthecircularSAR(CSAR)imaginggeometry,thesystemresponsefunctionisintheformoftheBesselfunctionwhichbringsahighsidelobe,andthehighsidelobeofCSARwillbeanimportantfactorinfluencingtheinterferometriccoherence.Theeffectofthehighsidelobeonthecoherenceisanalyzedanddeduced.BasedontheinterferometriccharacteristicsoftheslightdifferenceintheviewinganglesandthepotentialpixeloffsetintheinterferometricSAR(InSAR)images,arelationbetweentheradarimpulseresponseandthecoherencelossfunctionisderived.Fromtherelationalmodel,thecoherencelossfunctionduetothehighsidelobeofCSARisthendeduced,andcomparedwiththatoftheconventionalSAR.ItisshownthatthehighsidelobeofCSARfocusingsignalwillseverelyaffectthebaselinedecorrelationandcoregistrationdecorrelation.SimulationresultsconfirmthetheoreticalanalysisandquantitativelyshowthebaselineandcoregistrationdecorrelationdegradationduetothehighsidelobesofCSAR.

简介：Range-Doppler(RD)methodandReverse-Range-Doppler(RRD)methodarecombinedtogethertoachieveautomaticgeocodingofSyntheticApertureRadar(SAR)imagequicklyandaccuratelyinthepaper.TheRDmethodisfirstlyusedtolocatethefourcornersoftheimage,thentheotherpixelsoftheimagecanbelocatedbyReverse-Range-Doppler(RRD)method.Resamplingisperformedatlast.Theapproachhasanadvantageoverprevioustechniquesinthatitdoesnotrequiregroundcontrolpointsandisindependentofspacecraftattitudeknowledgeorcontrol.ItcancompensatetheshiftduetotheassumedDopplerfrequencyinSARimagepreprocessing.RRDsimplifiestheprocessofRD,thereforespeedsupthecomputation.TheexperimentalresultsshowthataSARimagecanbeautomatedgeocodedin30susingthesingleCPU(3GHz)with1Gmemoryandanaccuracyof10misattainablewiththismethod.

简介：ConventionalSyntheticApertureRadar(SAR)systemscannotobtainhigh-resolutionandwide-swathilluminationareaduetothewell-knownminimumantennaareaconstraint.SinglePhaseCenterMultiBeam(SPCMB)techniquecanovercomethislimitationbyaddingspatialsamplingthroughmultiplereceiversinazimuthdirection.Unfortunately,thisapproachwillleadtoanincreaseofazimuthambiguities(interbeamambiguities),becauseeachreceivebeam’smainlobeoverlapswiththeotherones’sidelobes.ThispaperprovesthatthefrontpartofSPCMBSARsystemscanbeconsideredtobeahybridfilterbank.Therefore,theazimuthsignalcanbereconstructedandtheinterbeamam-biguitiescanbeeffectivelysuppressedbyawell-designedhybridfilterbank.