mạch lọc
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Mạch lọcTRANSCRIPT
Chng7
Mch lc in
Tm tt L thuyt
Mch lc in l mt mng bn cc thc hin bin i ph ca tn hiu theo mt quy lut ton hc no. Mch lc thng dng tht l mch lc thun khng LC. Mch lc LC li chia thnh loi k v loi m.L thuyt mch lc thun khng thng xut pht t MBC hnh hnh 7.1a). nhn c cng thc c dng ton hc thun tin, ngi ta k hiu tr khng nhnh ngang l , nhnh dc l 2Z2. T mch lc hnh 7.1a) to ra mch loc i xng hnh Thnh 7.1b) v lc i xng hnh ( hnh 7.1c). L thuyt chung lc thun khng xy dng cho mch hnh 7.1a) xut pht t cng thc hng s truyn c tnh gC ca MBC
(7.1) T (7.1) tm c iu kin c lc l Z1v Z2 phi khc tnh.
Trng hp tch tng tr hai nhnh l mt hng th lc l lc loi k. Lc
Z1Z2=R02=K2=const. (7.2) Trong c th nguyn ca in tr, gi l in tr danh nh ca mch lc, k hiu l R0 hoc K.
Trong cng thc 7.1 th gC/2 l hng s truyn c tnh ca mch lc hnh hnh 7.1a) , thng gi l mt na t lc. Mc lin thng hai na t c mt t hnh T hoc (, c hng s truyn c tnh l gC.
+Lc thng thp (hay lc tn s thp) loi K c nhnh ngang l in cm, nhnh dc l in dung nh hnh 7.2. (di thng 0((C, di chn (C(() Cc cng thc tnh cc thng s ca mch lc thng thp:
in tr danh nh: (7.2) Tn s ct: (7.3) H s suy gim c tnh trong di chn:
(7.4) H s pha c tnh: Trong di thng:] (7.5) Trong di chn: bC = (.
Tng tr c tnh: (7.6) Ch : Mch lc c tng tr c tnh ph thuc vo tn s nn ni chung l khng th m bo HHPT. V vy nh ngha mt cch tng i trong cac bi tp s gii l: ch HHPT l ch ti thun tr Rt=R0. S mt ho hp ph ti c c trng bi h s ti: (7.7)+Lc thng cao (hay lc tn s cao) loi K c nhnh ngang l in dung, nhnh dc l in cm nh hnh 7.3. (di thng (C( (, di chn 0 ( (C ) Cc cng thc tnh cc thng s ca mch lc thng cao:
in tr danh nh: (7.8)
Tn s ct: (7.9) H s suy gim c tnh trong di chn:
(7.10) H s pha c tnh: Trong di thng:] (7.12) Trong di chn: bC = -(.
Tng tr c tnh: (7.13) +Lc thng di(hay lc di thng) loi K c nhnh ngang l khung cng hng ni tip, nhnh dc l khung cng hng song song, hai nhnh c cng tn s cng hng (0 (Hnh 7.4). (di thng (C1((C2, di chn 0 ( (C1, (C2 ( ( )
Cc cng thc tnh cc thng s ca mch lc thng di loi k:
in tr danh nh: (7.14)
Tn s ct:
(7.15) Di thng: ((=(C2-(C1= (7.16) Tn s trung tm (7.17) H s suy gim c tnh trong di chn:
(7.18) (7.19) (7.20) H s pha c tnh: bc= (7.21) Tng tr c tnh: (7.22) +Lc chn di (hay lc chn di hay lc di chn) loi K c nhnh ngang l khung cng hng song song, nhnh dc l khung cng hng ni tip hnh 7.5 (di thng 0((C1 v (C2((, di chn (C1((C2). Cc cng thc tnh cc thng s ca mch lc chn di loi K:
in tr danh nh: (7.23)
Tn s ct (ging lc thng di) :
(7.24) Di chn: ((=(C2-(C1= (7.25) Tn s trung tm (7.26) H s suy gim c tnh trong di chn: (7.27)
(7.28) H s pha c tnh: bc= (7.29) Tng tr c tnh: (7.30) Lc loi M:
Kt cu ni tip (hnh 7.6a)
(7.31) Kt cu song song (hnh 7.6b)
(7.32) Cc tham s:
(7.33) Tn s ct gi nguyn cc cng thc nh lc loi k.
Tn s t bin ca aC (tn s ((, ti aC= () =0 (7.34) Suy gim c tnh trong di chn: (7.35) Pha c tnh trong di thng: (7.36) Tng tr c tnh:
(7.37) (7.38) Mch lc RC.
Lc RC thng thp (hnh 7.7) Tn s ct: (7.39) H s suy gim c tnh:
(7.40)
(7.41.) Ti tn s ct shaC=2,2, tc aC=1,53 nepe
Ghp hai na t hnh 7.7a) c mt t lc hnh T hnh 7.7b) hoc mt t lc hnh ( hnh 7.7c). t lc hnh ( s dng s t tn hao nng lng hn t lc hnh T v dng hnhT i qua hai in tr mc ni tip. Lc RC thng cao (hnh 7.8) Tn s ct: (7.42) H s suy gim c tnh: (7.43) Khi (7.44)
Ti tn s ct shaC=2,2, tc aC=1,53 nepe.
Ghp hai na t hnh 7.8a) c mt t lc hnh T hnh 7.8b) hoc mt t lc hnh ( hnh 7.8c). Mc lin thng mt t lc thng thp v mt t lc thng cao c lc RC thng di.
bi tp
7.1.Mch lc thng thp c tn s ct l 15Khz, in tr ti 500(. Hy xc nh:
a) Cc thng s vt l ca mch lc.
b) V s hnh , hnh T v hnh ( ca mch lc, in trn hnh v tr s cc thng s vt l ca mch. c) H s suy gim c tnh tn s 10 Khz, 20 Khz v 25 Khz.
d) H s pha c tnh tn s 5 Khz, 10 Khz v 20 Khz.
e) Tng tr c tnh tn s 5 Khz, 10 Khz.
7.2. Mch lc thng thp tn s ct fC=12 Khz.
a) tn s no th h s suy gim c tnh t 2,172 nepe?
b) tn s no th h s pha c tnh t 90,20?
7.3.Mch lc thng thp loi k c tn s ct 8 Khz. Hy xc nh h s suy gim c tnh tn s 12 Khz v 18 Khz, h s pha c tnh tn s 2,5 Khz v 6 Khz.
7.4.Mch lc thng thp c tn s ct l 500 Hz, in tr ti 600(. Hy xc nh:
a) Cc thng s vt l ca mch lc.
b) V s hnh , hnh T v hnh ( ca mch lc, in trn hnh v tr s cc thng s vt l ca mch. c) H s suy gim c tnh tn s 1000 Hz v 1500 hz.
d) H s pha c tnh tn s 120 Hz v 320 Hz.
e) Tng tr c tnh tn s 120 Hz v 320 Hz.
7.5. t lc thng thp hnh T c in tr danh nh l 450 (, tn s ct 1200 Hz.
a) Xc nh cc thng s vt l ca t lc.
b) tn s no th h s suy gim c tnh ca t lc l 2,585 nepe?
c) tn s va tm c mun c h s suy gim c tnh l 7,755 nepe th phi kt cu mch lc nh th no?
d) Tnh h s suy gim c tnh ca mch lc va kt cu tn s 2000 Hz.
7.6. t lc thng thp hnh T c in tr danh nh l 450 (, tn s ct 1200 Hz. Hy xc nh:
a) Tng tr c tnh tn s 250 Hz.
b) tn s no th tng tr c tnh ca t lc l 320 (?
c) Nu in tr ti l 520 ( th nn kt cu t lc nh th no m bo phi hp tr khng vi ti? Khi tn s no s c phi hp tr khng hon ton?
7.7. t lc thng thp hnh ( c in tr danh nh l 450 (, tn s ct l 1500 Hz.Hy xc nh:
a) tn s no th tng tr c tnh ca mch lc l 600( b) tn s no th h s pha c tnh c tr s 1,46 rad.
7.8.Cho mch lc hnh 7.9.Hy xc nh:
a) Tn s ct ca mch lc. b) in tr danh nh R0 ca mch lc.
c) H s suy gim c tnh tn s 2000 Hz v 2500 hz.
d) H s pha c tnh tn s 500 Hz v 920 Hz.
e) Tng tr c tnh tn s 500 Hz
f) V mch lc hnh ( tng ng v in tr s cc thng s mch trn hnh .
7.9.Cho mch lc hnh 7.10.Hy xc nh:
a) Tn s ct ca mch lc. b) in tr danh nh R0 ca mch lc.
c) H s suy gim c tnh tn s 4000 Hz v 6 000 hz.
d) H s pha c tnh tn s 1000 Hz v 1800 Hz.
e) Tng tr c tnh tn s 500 Hz
f) V t lc hnh T v hnh ( tng ng ; in tr s cc thng s mch trn hnh .
7.10.Cho mch lc hnh 7.11.Hy xc nh:
a) Tn s ct ca mch lc. b) in tr danh nh R0 ca mch lc.
c) H s suy gim c tnh tn s 1000 Hz v 2500 hz.
d) H s pha c tnh tn s 350 Hz v 1200 Hz.
e) Tng tr c tnh tn s 250 Hz
f) V hnh T tng ng v in tr s cc thng s mch trn hnh .
7.11. Mch lc thng cao c tn s ct l 800 Hz,in tr ti 250(.Hy xc nh:
a) Cc thng s vt l ca mch lc.
b) V s hnh , hnh T v hnh ( ca mch lc, in trn hnh v tr s cc thng s vt l ca mch. c) H s suy gim c tnh tn s 150 Hz, 500 Hz v 1000 Hz.
d) H s pha c tnh tn s 250 Hz, 1000 Hz v 1500 Hz.
e) Tng tr c tnh tn s 1200 Hz.
7.12. Mch lc thng cao c tn s ct l 500 Hz.
a) tn s no th h s suy gim c tnh c tnh ca mch lc t 3 nepe.b) tn s no th h s pha c tnh c tr s -1,46 rad.
7.13. Mch lc thng cao c tn s ct l 200 Hz.
a) tn s no th h s suy gim c tnh c tnh ca mch lc t 35,86 dB.b) tn s no th h s pha c tnh c tr s - 600.
7.14.Cho mch lc hnh 7.12.Hy xc nh:
a) Tn s ct ca mch lc. b) in tr danh nh R0 ca mch lc.
c) H s suy gim c tnh tn s 90 Hz v 180 hz.
d) H s pha c tnh tn s 100 Hz v 320Hz.
e) Tng tr c tnh tn s 300 Hz
f) V mch lc hnh T tng ng v in tr s cc thng s mch trn hnh .
7.15. Cho mch lc hnh 7.13. Hy xc nh:
a) Tn s ct ca mch lc. b) in tr danh nh R0 ca mch lc.
c) H s suy gim c tnh tn s 200 Hz.
d) tn s no th h s suy gim t 3,5 nepe.
e) tn s no th h s pha c tnh c tr s l - 700f) V mch lc hnh T v hnh ( tng ng ; in tr s cc thng trn cc hnh .
7.16. Mch lc thng di loi k c tn s ct fC1=8 Khz, fC2= 12,5 Hz, in tr ti 850 (. Hy xc nh:
a) Cc thng s vt l ca mch lc.
b) V s hnh , hnh T v hnh ( ca mch lc, in trn hnh v tr
s cc thng s vt l ca mch. c) H s suy gim c tnh cc tn s 5 Khz v 20 Kz.
d) H s pha c tnh cc tn s 5 Kz, 9 Khz, 11,111 Khz v 20 Khz.
e) Tng tr c tnh cc tn s 9 Khz v 11,111 Khz
7.17. Cho mch lc hnh 7.14.
a) y l mch lc loi g,ti sao?
b) V s hnh hnh ( tng ng ca mch lc v in trn tr s cc thng s vt l ca mch lc trn .c) Tnh h s suy gim c tnh cc tn s 4,5 Khz v 16,082 Kz.
d) H s pha c tnh cc tn s 4 Kz, 7,5 Khz, 9,65 Khz v 18,092Khz.
e) Tng tr c tnh cc tn s 7,5 Khz v 9,65 Khz.
7.18. Mch lc di chn loi k c in tr danh nh l 1000 (, cc tn s ct l 6,25 Khz v 10,24 Khz.a) Cc thng s vt l ca mch lc.
b) V s hnh , hnh T v hnh ( ca mch lc, in trn hnh v tr s cc thng s vt l ca mch. c) V nh tnh dng c tnh bin tn s aC v pha tn s bC (theo l thuyt). d) Tnh h s suy gim c tnh cc tn s 7,5 Khz v 8,533 Kz.
e) Tnh h s pha c tnh cc tn s 4 Kz; 7,5Khz; 8,533 Khz v 16 Khz.
7.19. Mch lc thng thp loi m hnh T c m=0,5; kt cu ni tip, c to t mch lc loi K tng ng c in tr danh nh R0 =1000(, tn s ct fC=1Khz
a) Tnh cc thng s vt l ca mch lc
b) V s mch lc v in tr s cc thng s mch trn s . c) Tnh tn s t bin (( ca c tnh bin tn s (tn s c aC ( ( ) d) Tnh suy gim c tnh tn s 1100 Hz v 1160 Hz
7.20. Mch lc thng thp loi m hnh T c m=0,5, kt cu song song, c to t mch lc loi K tng ng c in tr danh nh R0 =1000(, tn s ct fC=1000 Hz
a) Tnh cc thng s vt l ca mch lc
b) V mch lc v in tr s cc thng s mch trn s
c) Tnh tn s t bin (( ca c tnh bin tn s (tn s c aC ( ( ) d) Tnh suy gim c tnh tn s 1100 Hz v 1160 Hz
7.21. Vi mch lc hnh 7.15
a) y l lc loi no?Ti sao?
b) Tnh tn s ct ca mch lc.
c) tnh h s suy gim aC ca mch lc in vo bng 7.1, t v th tng ng. (Nn lp trnh tnh theo cng thc 7.40). Bng 7.1
( rad/s0102030405060708090100
aC nepe
7.22. Cho mch lc hnh 7.16
a) y l mch lc loi no,ti sao?
b) Xc nh cc tn s ct ca mch lc.
c) Tnh h s suy gim aC ca mch lc in vo bng 7.2, t v th tng ng.
Bng 7.2
(rad/s0255075100125150175200225250275300
aCnepe
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Hnh 7.3
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