VII. MACH TAO XUNG VUONG
1. Tach s6ng bien dQ
Tach song bien d¢ duqc thlfc hi¢n nha cae ffi<;lch chinh ltru dung pharr ti'r phi tuycn ho~c cae ffi'.lch dung pharr tu luyen tfnh tham s6. Trong pharr nay ta chi khao sat cae m<;l-ch tach song dung dial, con cae lo~i m~ch tach song khac se duqc nghicn cuu a cae giao trinh chuyen nganh khac.
C6 hai iO<;li m~ch tach song dung m<;l-ch chinh hm: m<;l-ch tach s6ng n6i tiep va m~ch t:kh song song song. Trong m<;l-ch tach song noi tiep, diot tach song mac n6i tiep v(jj tai. Con trong m~ch tach song song song, diot tach song mac song song v6"i Iii.
1.1. M~ch tach s6ng noi tiep Sado m<;lch: Sado m<;lch:
D "'
R
!-Ilnh 5.21. Tach song hiefl Ji; 1101 tie'p dllng diot
Nguyen 1y Hkh song:
- Khi di~n up U" dllang thl diat D dugc phan cl!c thu~n, thong. T~ C dugc n<;lp di¢n. n<;lp di¢n.
- Khi di~n rip U" [lm thi diat D bj phan cl!c nguqc, tat. Tl,I C se phong di¢n
qua di¢n tra R.
SI! ph6ng va n<;ip cua t~ di9n thea guy lu~t bien d6i cua bien d¢ song mang
nen bien d¢ tin hi~u am tan duqc kh6i phl,lc l<;ii.
D1ng song tach song nhu sau:
Udh
t
t
t
Trang do:
- UtI!> la tIn hi¢u dieu che bien de) duCJc dua vao dau vao eua m~ch tach
s6ng (U,).
- Id Ia dong di¢n chiiy qua diot tach song 0 ho~c la di¢n ap tin hi¢u ra khi chua c6 lqc.
- U, la di;\ng di¢n ap tin hi¢u da dUCJc 19c bi.') c.ac thanh phan song mang cao
d.n boi tu C.
1.2. M~ch tach s()ng song song
So do m<;lch:
c
--.. ---il ~-+-------
u'l D?R 1 U,
/Iillll 5.23. Mqch tach s6ng bien d(i song song dllllg {hot
Nguyen ly tach song va d<:tng song lUang ttl nhu m~ch tach song n6i tic'p.
2. Tach s6ng ddn bien
Tach song dan hien co nhieu phuong phap khac nhau. Sau da.y ta se kh<\o sat phuang phap tach song dan bien bang b¢ nhao t~n s6.
i
So do kh6i tach song:
SSIl
F+f
t ft ft
~
B6 tach Be) lQc thong
song nhftn thap . Dao dQng song mang i I iL __ 1C-.-_.
Hin" 5.24. Sa (Il,) klu)'i tdell song dm! bien
Tlo tach
hi¢u song
Be) tach s6ng nhin Iii me)t be) nhan dung ct~ nhin tin hi~u dieu che dan bien
SSB co tal1 s6 F + f v6i tin hi¢u s6ng mang c6 tan s6 F, dau fa cua be) lach song Iii tin hi¢u co cac thanh phan tan sola f va 2F + f.
Sau d6, tin hi¢u dau fa be) nhan duqc dua qua me)t b¢ IQc th6ng thap de IQc lay thiinh philn tin hi¢u co t<'in s6 la f, con thanh phan tin hi¢u co tan s6 la 2F + r
bi lo<.ti boo
Nhlt v{ty, (:Jau ra cua bo IQc th6ng thap Ia tin hi~u ftm tfln co thICmg baa bien d() gi6ng v6i duong baa clla song mang cao Uin SSB.
Cac m<.tch tach song bien de) dW1C Stl dl,Jng a phia thu tin hi¢u d~ tach hiy
tin hi~u du dlIqc dieu che bien de) (rong cac h¢ thong phal thanh va tfuyen hinh.
VI. MACH TACH SONG D1EU TAN. D1EU PHA TiN HIEU '!'lION(; TV Tach song tin hi~u dicu tan Iii qua trinh bien d6i de) l¢ch 1<1n s611ic thai (so v(ji tan s6trung blnh) cua tin hi¢u da dUQ'c dieu tan thanh bien thien di¢n up a dfiu ra.
T,kh s6ng tin hi¢u dieu pha Iii qUi.l Idnh bien deli do 19ch pha (so '.loi pha dao d¢ng song mang chuan) tin hi¢u da dieu che pha thanh bien thien di¢n ap tin hi¢u fa.
Tach song tun so va tach song pha thuang duqc thl.rc hi¢n thea m()t trang nhfrng nguyen uk sau day: