带通与带阻滤波器

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1、第10單元帶通與帶拒濾波器之設計與製作帶通與帶拒濾波器之設計與製作BandPassFilterDesignTransformationformLowPasstoBandPassFrequencyElementsTransformationformLowPasstoBandPassBandPassFilterDesignShuntElementbecomesParallel-ResonantSeriesElementbecomesSeries-ResonantBPFFrequencyandImpedanceScalingForParallel-Reso

2、nantBranches:ForSeries-ResonantBranches:WhereR=TheFinalLoadImpedanceB=3-dBBandwidthfo=TheCenterFrequencyLn=normalizedInductorCn=normalizedCapacitorSummaryoftheBandpassFilterDesignProcedure1.TransfertheBandpassrequirementsintoequivalentlow-passrequirements.2.Refertothelow-passat

3、tenuationcurvesprovidedinordertofindaresponsethatmeetstherequirementsofstep1.3.Findthecorrespondinglow-passprototypeandwriteitdown.4.Transformthelow-passnetworkintoabandpassconfiguration.5.Scalethebandpassconfigurationinbothimpedanceandfrequency.BPFDesignExampleEx.DesignaBPFwit

4、hthefollowingrequirementfo=75MHzBW3dB=7MHzBW45dB=35MHzPassbandRipple=1dBRS=50ohmsRL=100ohmsSol:參考13-22頁之右圖可知，n=3時之Chebyshev可滿足設計之需求。參考相關書本可得低通濾波器之雛形電路圖。將前面所得之低通濾波器之雛形電路圖轉成帶通濾波器之雛形電路。Low-PassPrototypeBand-PassPrototype參考14-4頁可得二階帶通濾波器帶通濾波器可由低通與高通濾波器串連而成簡易二階RLC被動帶通濾波器BandRejectio

5、nFilterDesignDesignapproachsimilartobandpassfilterTransformationformLowPasstoBandRejectionShuntElementbecomesShuntSeries-ResonantCircuitsSeriesElementbecomesSeriesParallel-ResonantCircuitBRFFrequencyandImpedanceScalingForSeries-ResonantBranches:ForParallel-ResonantBranches:Wher

6、eR=TheFinalLoadImpedanceB=3-dBBandwidthfo=TheCenterFrequencyLn=normalizedInductorCn=normalizedCapacitor70MHz帶通濾波器帶通濾波器之頻率響應量測結果帶通濾波器之輸出入返回損耗量測結果帶通濾波器之介入耗損量測結果900MHz帶拒濾波器帶拒濾波器之頻率響應量測結果帶拒濾波器之輸出入返回損耗量測結果帶拒濾波器之介入耗損量測結果濾波器類型之比較LoadedQInitialslopeattenuationRippleresponseLinearphase巴

7、特沃斯(Butterworth)mediummediumNoGood柴比雪夫(Chebyshev)HighHighYesPoor貝索(Bessel)LowLowNoBestCharacterType