简介：Akindofnovelbinaryphasecodenamedsidelobesuppressioncodeisproposedinthispaper.Itisdefinedtobethecodewhosecorrespondingoptimalsidelobesuppressionfilteroutputstheminimumsidelobes.Itisshownthattheredoexistsidelobesuppressioncodesbetterthantheconventionaloptimalcodes-Barkercodes.Forexample,thesidelobesuppressioncodeoflength11withfilteroflength39hasbettersidelobelevelupto17dBthanthatofBarkercodewiththesamecodelengthandfilterlength.

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

简介：AcancelingrangesidelobesschemehasbeensuggestedbyYangGuangzheng,etal.,(1997)thistechnologyisbasedonthefactthatallsidelobeofgroupcorrelationfunctionofidealsetsarezero.Atfirst,thispapergivesthebestidealsets(i.e.thebestbiphasecodesetswhosemaximalsidelobenotmorethan2)forallcodelengthN≤12,whichhavebeenobtainedfrombinarysequencesbymeansofthebestcodessievingmethodsuggestedbyYangGuangzheng,etal.(1997)ComputersimulationforgroupcorrelationpropertyofbestidealsetsforcodelengthN=12onvariousconditionsismade.Simulationresultshowsthatthesidelobelevelofbestidealsetwithnoweightingiszero,underconditionofzero-Dopplershiftandhasultra-lowsidelobeonDopplerupto5kHzwithnoweightingandwhosetoleranceofphaseandamplitudedistortionisbiggertoo.

简介：Theeffectofsystemmismatchesonanadaptivelinearconstrainedgeneralizedsidelobecanceller(LC-GSC)isdiscussedinthispaper.Basedonthearraygainindex,twoclassicsystemmismatches,thedirectionofarrival(DOA)mismatchandthemismatchesarisingfromarraydisturbance,arestudied,respectively.Toobtaintheeffectivemethodsforcompensatingforthesystemmismatches,weanalyzetheperformanceoftheimprovedLC-GSCwiththediagonalloadingandadditionalconstraints(suchasthedirectionalconstraintsandderivativeconstraints).Thecomputersimulationsshowthatthetechniquesofdiagonalloadingandadditionalconstraintscaneffectivelycompensateforthesystemmismatches.Thelossofarraygainscanbecontrolledwithin3dBinthepresenceof20%ofarraydisturbancesorDOAmismatchwhenthesignal-to-noiseratioislessthan10dB.Theanalysisillustratesthattheproposedcompensationmethodsarevalidandfeasible.

简介：Thispapergivesthedirectivityfunctionofasectoralmul-ti-elementcylinderarray,analyzeitsphasefactor,explainindetailthesideloberejectionbyselectingthenumberofelements,bafflingandamplitudeweighting.Theyareparticularlyusefulfordirectionaltrackingofacousticalsignalandtargetlocating.

简介：Thispaperpresentsanewapproachforattenuatingcoherentnoisein3Dseismicdata.Anadaptivebeamformingwithgeneralizedsidelobecanceller(GSC)designmethodologyisutilizedhereasageneralformoflinearlyconstrainedadaptivebeamformingstructure.Itconsistsofafixedbeamformer,andasignal-blockingmatrixinfrontofanunconstrainedadaptivebeamformer.Considerationfofthecomplexityofthegeometryfor3Dseismicsurvey,the3DbeamformingwithGSCtechniqueisdevelopedwithtwokeypoints:(1)sortingalongazimuthsectionstosimplifytherelationshipbetweentraveltimeandoffsetfrom3Dto2D,and(2)dynamicbinningschemetoavoidthepossiblepoorfoldinginsomeazimuthsections.Bothsimulationresultandrealdataexampleshowthatthenewlydeveloped3DbeamformingwithGSCyieldsmorecredibleresultsatarelativelowcost,sufficientstabilityandgoodresolution.

简介：Atunablenegativecoefficientband-passmicrowavephotonicfilter(MPF)withimprovedmainlobe-to-sidelobesup-pressionratio(MSSR)byaSagnacinterferometer(SI)isexperimentallydemonstrated.ThenegativecoefficientcharacteristicofMPFisachievedbyusingthephasemodulationtechnology.Thecentralfrequencyoftheband-passMPFistunablecontinuouslybychangingthewavelengthseparationofmulti-wavelengthopticalcarriers.A38-tapnegativecoefficientband-passMPFwhoseMSSRisincreasedbyabout6.371dBisachievedinexperimentbyapodizingthetapcoefficientwiththeSagnacinterferometer.