structured filter banks as adaptive frequency exciser for suppressing narrow-band interference

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1、StructuredFilterBanksasAdaptiveFrequencyExciserforSuppressingNarrow-BandInterferenceChineseJournalofElectronicsVo1.15,No.3,July2006Low-DelayTree-StructuredFilterBanksasAdaptiveFrequencyExciserforSuppressingNarrow.BandInterference木XIEXuemeiandSHIGuangming(Sch

2、oolofElectronicEngineering,XidianUniversity,Xi'an710071,China)Abstract?--——Theadaptivefrequencyexciserbasedonsubbandtransformisofparticularinterestbecauseofitsexcellentinterference-suppressionperformance.InthisP8.-per.weproposeanovelmethodfordesigningPerfect

3、—reconstruction(PR)tree.structuredfilterbanksactingasadaptive~equencyexcisers.Theyareusedforsuppress-ingnarrow-bandinterferencesinDirectsequencespreadspectrum(DSSS)systems.Particularattentionispaidtoalowsystemdelayrequirementwhichiscriticalindelay-sensitivea

4、pplications.Thisisachievedbydecreasingthefilterlengthwiththedepthincreaseofthetreeandbyemployingthefilterbankswithlow-delayproperty.Thenumericalanalysisandsimulationresultshaveshownthat,withthecomparableBiterrorrate(BER)performance,thedelayoftheadaptive~eque

5、ncyexciserbyusingtheproposedmethodis8igniflcantlylowerthanthatoftheconventionaldesign.Keywords——Filterbank,Treestructure,Low-delay,Adaptive~equencyexciser,Narrow-bandinterference.I.IntroductionNaxrow.bandinterferencesalwaysappearinDirectse.quencespreadspectr

6、umfDSSS1basedcommunicationsys—terns.AlthoughtheDSSSiscapableofreducingthenarrow-bandinterfe?rencenaturallybydespreadinginthereceiver,ithasbeenfoundt钏thattheperformanceofaDSSSreceivercanbegreatlyimprovedbyfilteringtheinterferencepriortodespreading.Oneofthemet

7、hodsforfilterdesigninthisre.gardisbasedonspectralanalysisofthereceivedsignalbytransform-domainprocessing【钏.Amongtheproposedtrans—formapproaches,theadaptivesubbandtransformdescribedinRefs.【1,2】isofparticularinterestbecauseofitsexcellentin.terferencesuppressin

8、gperformance.Fig.1showsasimplifiedDSSSbasedcommunicationsys.ternwheretheblocknamedadaptivefrequencyexciserisemployedtosuppressnarrow-bandinterfefencespriortodspreading.Theadaptivefrequencyexcise