Bai13_Mach Loc Dien Thu Dong

TRNG HBK TP

Nguyen Duy Khanh

TN MACH IEN I

BAO CAO TH NGHIEM

BAI 13: MACH LOC IEN THU ONGI. Mach loc thong cao R-L:

1. Mach th nghiem:

Dung may phat song chon song sin co bien o 2V, tan so 1Khz, offset la 0, tao nguon kch thch cho ngo vao cua mach.

(Dao ong ky chon Time/Base (Time/Div) = 0,2 ms hoac 0,1 ms)2. Xac nh cac ac tuyen bien tan, pha tan:

- ac tuyen bien - tan:

- ac tuyen pha tan:

3. Tan so cat cua mach loc:

ac tuyen bien o cua mach (K(j()( cho ta thay ay la mang 2 ca co tnh loc ien. Tan so cat cua mach loc la tan so ma o mach chuyen t dai thong sang dai chan, c xac nh khi (K(j()( = (K(j()(max. Khi o o suy hao bien o se co gia tr tng ng vi K(j() = -3,03dB va tan so cat xac nh c la fc = 1,58Khz.

Theo ly thuyet: v (K(j()(max = 1

=> (C =

=> fC = = = 1,591 Khz.

Ta thay tan so cat o c ten th nghiem gan bang vi tnh toan theo ly thuyet. Co sai so rat nho trong th nghiem.

4. o lech pha cua hai tn hieu vao va ra cua mach loc tai tan so cat, nhan xet:

Tai tan so cat fc = 1,58Khz, ta xac nh c o lech pha nh sau:

b = 2,743

Y0 = 1,996

Goc lech pha c xac nh bang cong thc:

Sin ( = = = 0,7276 => ( = 46,70Theo ly thuyet: tai ( - (C = 2(f ta co:

.j(L;

Vi (CL = 2(.1,591.103.10.10-3 = 99,965 ( 100

Gia s

=>

.j(L = => ( = 450

= => ( = -450

T gian o vec t ta thay tn hieu ra nhanh pha 450 so vi tn hieu vao.

=> Ket qua Ly thuyet va thc nghiem phu hp nhau.

5. Thiet ke bo loc thong cao, dung mach R-L, co tan so cat fC = 3Khz, biet gia tr L = 2mH.

fC = => R = 2fCL = 2.3.103. .2.10-3 = 37,68 (

II. Mach loc thong dung R-C:

1. Mach th nghiem:


2. Ve gian o Bode, xac nh cac ac tuyen bien tan va pha tan, tan so cat cua mach loc.

- ac tuyen bien tan:

- ac tuyen pha tan:

3. Tan so cat cua mach loc.

- Theo ly thuyet: Ham truyen mach co dang:

K(j() = = =

ac tuyen bien o theo tan so cho ta ay la mot mach loc thong thap, va tan so cat cua mach loc cung c xac nh t:

((CRC)2 = 1 => (C = => fC = = = 159,2 Hz.

- o bang thc nghiem: khi K(j() = -3,02dB, tan so cat o c 160Hz.

=> Ket qua Ly thuyet va thc nghiem phu hp nhau.

4. o lech pha cua hai tn hieu vao va ra cua mach loc tai tan so cat, nhan xet:

b = 1,998V

Y0 = 2,82V

Goc lech pha c xac nh bang cong thc:

Sin ( = = = 0,7085 => ( = 45,10Theo ly thuyet: tai (C = 2(fC = 2(.160= 1005 ( 1000 (rad/s)

=> = = 100

Gia s

= =

=

Ta ve c gian o vec t:

Qua gian o ta thay tn hieu ra cham pha hn 450 so vi tn hieu vao.=> Ket qua Ly thuyet va thc nghiem phu hp nhau.

5. Thiet ke bo loc thong thap, dung mach R-C, co tan so cat fC = 1,7Khz, biet gia tr C = 0,01(F.

fC = => R = = = 9,366.103 ( = 9,366 K(

III. Mach loc thong dai R-L-C:

1. Mach th nghiem:


2. Ve gian o Bode, xac nh cac ac tuyen bien tan va pha tan cua mach loc. Xac nh tan so trung tam, bang thong va he so pham chat cua mach loc.

- ac tuyen bien tan:

- ac tuyen pha tan:

* Theo ly thuyet:

Ham truyen at ien ap cua mach:

K(j() =

Va ta co:

(K(j()( =

(K(j()( se at cc ai tai (C = c goi la tan so trung tam cua mach loc thong dai. Khi o gia tr (K(j()( at cc ai la 1. Bang thong cua mach loc c xac nh khoang ma (K(j()( ( 0,707.

BW = (2 - (1 = = = 9090,91

- He so pham chat:

Q = = 2,19

f0 = = 3183 Hz = 3,183 Khz.

- Hai tan so cat la nghiem cua phng trnh:

=

=> 2L2 = - = 0 [ - ][ + ] = 0

- = 0

=>

+ = 0

(2LC - ( - 1 = 0

(2LC + ( - 1 = 0

(loai)

(loai)

= 2,458.104 (rad/s); = 7,75.104(rad/s)

=> f1 = 2,467 Khz; f2 = 3,912 Khz

* Ket qua thc nghiem:

- mach nay ta xac nh c 2 gia tr tan so cat:

f1 = 2,51Khz; f2 = 3,98Khz.

- Tan so trung tam: f0 = 3,16 Khz.

- Bang thong:

BW = (2 - (1 = 2(( f2 - f1) = 2((3,98 2,51).103 = 9236,3 (rad/s)

- He so pham chat:

Q = = 2,15

* Ta nhan thay ke qua ly thuyet va thc nghiem la tng oi nh nhau, co sai so nho do phep o.

6. Dung dao ong ky xac nh o lech pha cua hai tn hieu vao va ra cua mach loc tai tan so cat, nhan xet:

* Tai fC1 = 2,51Khzo c:

b = 2,724;

Y0 = 1,999

Goc lech pha: sin( = = 0,733=> ( = 47,20

* Tai fC2 = 3,98 Khz o c:

b = 2,972;

Y0 = 1,998

Goc lech pha: sin( = = 0,672 => ( = 42,20

* Tai fC0 = 3,16 khz o c:

b = 4;

Y0 = 0,2

Goc lech pha: sin( = = 0,05=> ( = 2,8660

Theo ly thuyet, tai fC0 th ien ap vao trung pha vi ien ap ra, nhng thc te o c lec nhau 2,8660. Nguyen nhan do sai so phep o. o lech pha tai 2 tan so cat gan bang nhau.

7. Thiet ke bo loc thong dai, dung mach R-L-C, f = 1200Hz ( 2700Hz, biet gia tr C = 0,022(F.

- Xac nh bang thong:

BW = (2 - (1 = 2((f2 f1) = 2((2700 1200) = 9420 (rad/s)

- Xac nh tan so trung tam:

f0 = = =1950 Hz

- Xac nh L:

f0 = => L = = 0,3H

- Xac nh R:

BW = => R = = = 768,4 (

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Bai13_Mach Loc Dien Thu Dong