滤波器和衰减器的电路设计

???¨?÷???????÷?????·?è?? ???????¨?÷?°?ó????·¨???è?? ???¨?÷???????????????????·???????¨???????????í?????ü?????????????????¨?????·?????????????¨???????????????????????ó???????????????ó??????????????×è?????¨????×è???????????????????????????????¨?÷???ù±????ó?????¨1???¨????????????????????×è?????????????????ó?????¨????????×è???????????????±???????¨2???¨??????????×è????????????????±???×è???????? ???¨?÷??·??à?????? ???¨?÷??1?????????¨?÷ 2?????????¨?÷?? ???????¨?÷??·?????RC???¨?÷??LC???¨?÷??RC???¨?÷??·?????1 ???¨RC???¨?÷ 2 ???¨RC???¨?÷ 3 ???¨RC???¨?÷ LC???¨?÷??·?????1 ???¨LC???¨?÷ 2 ???¨LC???¨?÷ 3 ??×èLC???¨?÷ 4
???¨LC???¨?÷ ???????¨?÷??·?????1 ???????¨???¨?÷ 2 ???????¨???¨?÷ 3 ???????¨???¨?÷ 4 ??????×è???¨?÷ ???°???¨?÷??·??????è??·?·¨?????????????°??????·???·¨???????¤×÷????·???·¨?¨????×???·¨?????°???è???ò?????×?????????????????¨?÷?????????¨???????í???????¤?¨??????±????ó?????¨??????????????????×è?????????????ú×??????¨???????????????ó???ó??????????×????í?????ù????·???·?·¨???ü???????????í?????¨?????à?ü?????????????????ó?ù??×???·?·¨??????????????????????·?·¨?è???????????¨?÷???????????¨???????í???¤?¨??????·????ü???ù???????????????????¨?÷?è?????ó?? 1.RC???¨?÷[??±í??] ±í?? RC???¨?÷   ???¨???¨?÷ ???¨???¨?÷ ???¨???¨?÷ ?à?????¨?÷ ???· (a) (b) (c) (d) ?? ?? ?? ?? ?? ·? ±? fc??1/6.28RC fc??1/6.28RC fL??1/[6.28C2(RL+RB)] fH??(RL+RB)/6.28C1RLRB   ?? ·? ±? fc??1/3.2RC fc??1/3.2RC fL??1/3.2C2(RL+RB) fH??(RL+RB)/[3.2C1RLRB ???????? ??????fc=10kHz R=1k?? ?ò3·?±???????????: C??1/6.28fcR =1/6.28??10??10 ??10 ??0.015??F ????fc=1kHZ R=3k?? ?ò3·?±???????????: C??1/6.28fcR =1/6.28??10??10 ??10 ??0.015??F ??????fH=200kHz,fL=15kHz ????×è????10??????×è????5k?? ??????????????????×è?????? ?à??RL=10k??,RB=5k??,??°?3·?±????????????ò C??(RL+RB)/6.28fHRLRB=(10+5)??10/6.28??200??10??10??5??10=240pF C2??1/6.28??15??10??(10+5)10??680pF ???? RC???¨?÷?????????????????????????ò?????¨?÷???????????÷?????????????????????????ù??????±???????C????±?????×èR???????????¨???¨?÷ ???¨???¨?÷????±?????×èR????±???????C???????????÷?????????????????????????ù??????????????·??????¨?????¨?÷ fL????????????????fH?????????????????¨??fH>10fL??????????±???×é?????·?????????????? ????????RC???¨?÷????????????????????°????????????????????????à????RC???¨?÷??????????????????????RC???¨?÷????????????????·?±?????????????16dB ×??÷ ??????????????????R??RL??RB??????C??C1??C2????F??fc??fL??fH??Hz 2.LC???¨?÷ LC???¨?÷???????????????????¨???ü??????L??????C?ù×é??????????????????????????????????
?????????????????????ò??LC???¨???¨?÷????±???????????±????????????¨???¨?÷??L??C???????ò???ü?à·????¨????LC???¨?÷?????à???????¨K??LC???¨?÷??????m??????LC???¨?÷?? K?????¨?÷??????±?×è??Z1????±?×è??Z2????????????????????±?????????K??????K??????????×è???ù????????K=RZ1??Z2??±í??????????K?????¨?÷?¨???¨?????¨?????¨????×è???????¨?????ú???°??????????±í??a?????????????????????à?¨Np)?ò·?±??¨dB???¨1dB=0.12Np)??b???à??????????????????????±í????????K?????¨?÷?????????÷???±?????¨1?????¨?????°??×è??Zc??????±??????ó???????ì??×è???????§?????¨2?????????????????¨???????????±??????·??????±????????????m?????¨?÷?ò????m????K??×é?????ì?????¨?÷?? m?????¨?÷????K?????¨?÷??±??????????????????????¨a??K?????¨?÷????±???????????????±????????????????????ü?????????????ü???????????????????????????????????÷?ò?????ó???ò???????????????????¨???????±???????????
??¨a??K??T?????¨?÷??±??????¨b?????¨?¨?÷??????T??????m?????¨?÷?????í????????K??????????m?????¨?÷ ??C??m?????¨???¨?÷????????????m??????1???????????¨K???¨?÷??m???ú?????ò????×è???ó???????ú???ú???±???????????????ó?????????ó???????±??????????K???¨??m=1?????¨?÷???????????ò?????????????????÷??????????m????K???????????????¤?????????????????ü???????????? ?? 1 ??2????T??????m?????¨?÷??O??O???????ü????°???????????????°?????T????????m?????¨?÷??????O??O???????ù×ó?ò??????????×è???ù??Z????m??Z????m??????L??????m?????¨?÷???°??×è??????3????Z????m??????±??????é?????±m=0.6?±??Z????m???¨?????ù±?????????פ??????L???¨?÷???????¨?÷???×????±???
?????????¨?÷?????????°????????????×è???????? ??2 ??3