单管调频接收电路几例

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1、单管调频接收电路几例（英文）--MicropowerFMBro时间:2010-03-2200:00来源:作者:点击:119次　It'sbeenquiteawhilesinceIbuiltasuper-regenerativereceiverfortheFMbroadcastbandandI'vebeenmeaningtoplaywithadifferentsourcefeedbacktopology,sothislittleradiowasthrowntogetherontheSaturdayoftheAP

2、EClongweekend.Thetopologyisyourclassicgrounded-gateFETVHFHartleyoscillator.Thedrainresonatorinductanceiscentre-tappedwithfeedbacktothesourcethroughasmallcapacitance.Bytappingdowntowardsthecold-endofthecoilthefeedbackisn'tascriticalasyourusualsource-drainca

3、pacitorfeedbackandittendstobefarlessdifficulttogettoworkacrossabroadrangeoffrequencies.TheRFCtoanRCsourcecircuittoimplementself-quenchingisverytraditionalforsuper-regenerativedetectors.Thequenchgetsfrequency-modulatedsomewhatbythedraincurrent,soitvarieswit

4、hsignalstrengthandtherecoveredmodulation,thisistypicalforself-quenchedcircuits(simplicityhasitsprice). Thedetectoraloneprovidessufficientaudiotodriveacrystalearpieceinaveryquietroom,givingatrue"singletransistor"FMreceiver.Alargishresistor(~10k)preventsthes

5、ourcecircuitfromseeingtoomuchofthefairlylargecapacitanceofthepiezoelement(about14nF)andpullingthequenchwelldownintotheaudiorange.Someadditionalaudiovolumecanbeachievedbyredesigningthequenchcircuittoutilizethepiezocapacitancedirectly,butthesourceresistanceh

6、astobedroppedquitealottoachieveaviablequenchfrequencyandthegaininsensitivityisn'tasfantasticasonemighthope.Still,giveitatry,asingleactivedeviceFMradio,pulling<100uAismightyimpressive!Thedetectorcanoperatewiththesourceresistanceapproaching1M,evenatextremely

7、feeblecurrentsitisstillverysensitive.Bestover-allperformancewasachievedwith10Kand6.8nFinthesourcecircuit.Idecidedtoaddastageofaudiogain,retainingtheuseofahighimpedanceearpiecetokeepthecurrentconsumptionassmallaspossible.Ipickedasuper-betatransistor,theMPSA

8、18,fortheaudioamplifier,andusedasimpleself-biastopology.Thiswasalltokeepthetotalreceivercurrentconsumptionverysmallandmaximisethebatterylife.Theaudioqualityisquiteacceptable(theusualsuper-regen'slope-detectio