Bai Tap Lon Mon Thu Phat

8/3/2019 Bai Tap Lon Mon Thu Phat

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BI TP LN MN THIT B THU PHT V TUYN IN

MC LC

LI M U .......... 01

PHN : TNG QUAN V THIT B THU PHT .......... 02I.Tng quan v my pht v tuyn in. .......... 02

1. Khi nim: .......... 02

2. S khi .......... 03

3. Phn loi my pht: .......... 04

4. Cc ch tiu k thut ca my pht .......... 05

II. My thu .......... 07

1.Cc tham s k thut .......... 072.Phn loi my thu .......... 07

3. My thu khuch i thng: .......... 08

4. My thu i tn .08PHN II. PHN TCH S KHI,S TNG PHI HP TR KHNG

ANTEN CA MY THU PHT VT JSS-720 .......... 10

I. Phn tch phn pht .......... 10

1. Khi pht ca JSS 720 bao gm cc khi: .......... 102. Nhim v cc khi: .......... 10

3. Phn tch .......... 10

II. Phn tch phn thu .......... 14

1. Phn thu gm cc khi: .......... 14

2. Nhim v cc khi: .......... 14

3.Phn tch .......... 14

III. i su phn tch b phi hp tr khng anten JSS-720. .......... 171.Khi qut: .......... 17

2.S khi ca b iu hng: .......... 19

IV. KT LUN. .......... 26

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2/26


LI M U

Ngy nay cng vi s pht trin mnh m ca thng tin v tuyn th thit b v

tuyn in(VT) ng mt vai tr rt quan trng trong vic truyn ti tin tc i xa.Thit b thu pht c s dng rt rng ri trong nhiu lnh vc thng tin nh vic pht

thanh truyn b cc thng tin i chng, cc thng tin qun s c bit thit b thu

pht c s dng trn cc tu thuyn nhm phc v cho mc ch an ton v cu nn

trn bin.

Thng tin lin lc trc khi c truyn i xa n phi c iu ch dch ln

min tn s cao c khi nng t bc x ra khng gian. Thit b thc hin x l tin tc,

iu ch v bc x sng in t gi l my pht v tuyn in. Thit b lm chc nngngc li gi l my thu v tuyn in.

M hnh truyn sng trong khng gian t do ca h thng thng tin VT :

nghin cu k hn sau y chng ta s nghin cu tng quan v thit b v

tuyn in v i su phn tch chi tit s khi ca my thu pht VT JSS-720.Phn

tch chi tit s phi hp tr khng.

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My pht vtuyn in

My thu v tuynin

Mi trng truyn


3/26


PHN : TNG QUAN V THIT B THU PHT

I.Tng quan v my pht v tuyn in.

1. Khi nim:

My pht v tuyn in l mt thit b v tuyn in to ra dao ng cao tn a

vo anten bc x ra khng gian t do di dng sng in t truyn thng tin i

xa.

2. S khi

+> Khi dao ng: To ra mt tn s chun a vo khi iu ch

+> Ngun tin gm: Ngun tin tng t v ngun tin s. N to ra tin tc m pha thu

yu cu.

+> Khuch i tin tc: Khuch i bin tin tc ln a ti khi iu ch.

+> iu ch: Trn hai tn s t khi dao ng ti v t ngun tin ti cho ra tn s pht.

+> Khuch i ra anten: C nhim v: - m bo cng sut bc x ra khng gian.

- Lc hi bc cao.

- Phi hp tr khng.

tng hiu qu ca vic pht sng v tuyn in ngi ta a ra s khi phc tp

hn nh sau:

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Dao ng iu ch

K tintc

K raanten

Ngun tin


4/26


+> Khi tng hp tn s v to tn s pht: C nhim v to ra nhiu tn s pht theoyu cu t tn s chun ca b dao ng thch anh.

+> Tin khuch i cng sut: C nhim v khuch i bin tn hiu t khi iu

ch ti c bin ln trc khi bc x ra khng gian.

+> Khuch i cng sut: C nhim v lc hi, phi hp tr khng vi mch ra Anten.

3. Phn loi my pht:

C nhiu cch phn loi khc nhau tu theo mc ch s dng

a.Phn loi theo nhm cng tc c cc loi sau:

- My pht lin tc: Cc sng siu cao tn lun lun bc x ra khng gian.

- My pht khng lin tc: Ch bc x ra khng gian khi c tin tc.

b.Phn loi theo tn s pht:

Trong di tn v tuyn in ngi ta chia ra cc di tn:

-sng di: 30KHz 300KHz.

-Sng trung: 300KHz 3000KHz

-Sng ngn: 3MHz 30MHz

-Sng cc ngn: 30MHz 300MHz

-Sng siu ngn: 300MHz 3000Mhz

-Sng SHF: 3GHz 30GHz

Theo cch ny ta c my pht sng trung, sng ngn, sng cc ngn.

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T/Htn sto

tn s

K/tintc

iu

ch

K/ra

anten

TinK/cng

sut

K/cng

sut

Daongthch

anh

Ngun tin


5/26


c.Phn loi theo cng sut pht bao gm:

-Cng sut thp.

-Cng sut trung bnh.

-Cng sut ln.d.Phn loi theo phng php iu ch gm:

- iu bin

- iu tn

- iu fa

- Kt hp

- Xung

4. Cc ch tiu k thut ca my phta. Ch tiu v in:

+ Cng sut pht ca my pht: l cng a ra anten bc x ra khng gian. Cng

sut ny quyt nh c li thng tin ca thit b gi l cng sut c ch P t. Cng sut tn

hao Pa, cng sut tiu th P0 (tiu th nng lng ca ngun ).

+ Hiu sut ca my pht:

0

tP

P

=

2% 20% =

+ Di cng tc: L kh nng lm vic ca my pht (bc x ra anten) trong mt di tn

s, on tn s no .

+ n nh tn s pht: y l ch tiu quan trng nht ca my pht n m bo

c qu trnh thng tin lin lc nhanh chng, thu hp c rng di tn khng gy

can nhiu cho cc i pht khc. n nh tn s ph thuc ch yu vo tng to dao

ng ch ca my pht do nng cao n nhca tn s dao ng ch ngi ta

dng thch anh.

+ chnh xc ca tn s: L s sai lch gia b ch th tn s pht vi tn s bc x

thc t ca anten ca my pht ra khng gian. N ph thuc vo c cu ch th ca

my pht :

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6/26


+ Sng hi: L cc tn s hi bc x ra khng gian cng vi thnh phn tn s c bn

ca my pht, tn s hi s gy nhiu cho cc i pht khc v gy nhiu cho i xung

quanh.

+ Tham s iu ch gm:+/ Di tn iu ch: L gi tn s thc hin iu ch tin tc trong my pht. Tu theo

tng loi tin tc m s dng tn s iu ch thch hp.

+/ Phi m bo su iu ch: Tc l s dng di tn v tn s thch hp, thng s

dng cho phng php iu ch n bin.

+/ c tuyn tn s iu ch: ng cong biu din s ph thuc h s iu ch theo

tn s.

+/ Mo phi tuyn iu ch:Mo phi tuyn do tnh cht phi tuyn ca cc phn t phi tuyn gy nn. Mch khuch

i c c im l chn p tp m nn ta da vo trit tiu cc thnh phn khng

c li. Trong mch khuch i h s khuch i cng khng ng u vi cc tn hiu

khc nhau.

b. Cc ch tiu k thut v kt cu:

Ph thuc vo iu kin, mc ch s dng thit b ngi ta xt n ch tiu:

+/ Trng lng th tch+/ Kh nng chu va p

+/ Kh nng chu nhit , m

+/ Thun li cho vic thao tc s dng

+/ H s an ton c kh ca thit b

+/ Gi thnh ca thit b

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7/26


II. My thu

1.Cc tham s k thut

a. nhy trong my thu:

nhy l kh nng thu c tn hiu nh nht u vo m my thu cho ra c mctn hiu tin tc b ch th bnh thng. y l ch tiu quan trng nht nh gi

cht lng ca my thu. nhy ph thuc rt ln vo cc tng u vo v ph thuc

vo h s phm cht ca cc linh kin. n v nh gi nhy l mv hoc v

b. n nh tn s:

n nh tn s ca my thu c nh gi bng di tn f ca my thu, f cng

nh th n nh tn s cng cao.

c. chnh xc ca tn s:c nh gi bng sai lch tn s gia tn s trn b ch th ca my thu v tn s

cng hng u vo ca my thu .

d. Di tn cng tc:

Di tn cng tc l thng s nh gi kh nng lm vic ca my thu trong mt on

tn s cng tc nht nh.

e. Ch cng tc:

Ch cng tc l kh nng my thu c th thu c cc loi tn hiu cc ch iuch khc nhau.

f. Ngun cung cp:

Ngun cung cp gm in p s dng, cng sut ngun tiu th.

Ngoi ra cn mt s thng s khc nh kch thc, kt cu lm vic,nhit , m.

2.Phn loi my thu

a. Phn loi theo di tn s cng tc gm:

+ My thu sng di

+ My thu sng trung

+ My thu sng ngn

+ My thu sng cc ngn

+ My thu sng siu cao tn

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8/26


+ My thu ton sng

b. Phn loi theo ch thu gm:

+ My thu iu bin: gm my thu n bin v my thu a bin

+ My thu iu tn+ My thu iu pha

c. Phn loi theo tn hiu tin tc gm:

+ My thu hnh

+ My thu thanh

+ My thu ch(Telex)

+ My thu nh

+ My thu Fax3. My thu khuch i thng:

+ Mch vo l khung cng hng cng hng tn s cn thu, thng l khung daong LC.

+ Khi tch sng: tch tn s cn thu ra khi tn s cao tn.

+ Khi khuch i cng sut: Khuch i bin tn hiu thu ln a ra loa.

Nhc im ca my thu ny l: n nh km, di tn lm vic hp, tp m ln v

nhiu.

u im: n gin, r tin, khng i hi cng ngh.

4. My thu i tn:

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Tchsng

Mchvo

K/cngsut


9/26


+ Mch vo: C nhim v chn lc tn s cn thu. Tn hiu c chn a vo khi

K/ cao tn, y khng quan trng h s khuch i m iu quan trng l t s S/N.

+ Khi i tn: Trn tn s t khi khuch i cao tn vi tn s khi dao ng ni

OSC a ra tn s khng i Ftt tn s ny c a qua khi khuch i na, tng

khuch i ny quyt nh nhy ca my thu.

+ Khi tch sng: Phc hi li tin tc a vo b khuch i cng sut a ra loa,tch mt phn tn hiu a vo b t iu chnh khuch i.

+ Mch t iu chnh khuch i c nhim v bo m tn hiu n b tch sng l

ln v trong gii hn b tch sng c hiu qu. B t iu chnh khuch i thc

hin iu ny bng cch cm nhn mc tn hiu u vo ti b khuch i cao tn,

cng nh tn hiu vo b khuch i tin tc v iu chnh h s khuch i ca b

khuch i duy tr n mc n nh.

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K/cao tn

itn

K/trungtn

OSC

Tchsng

K/cngsut

AGC

Mchvo

S khi


10/26


PHN II. PHN TCH S KHI,S TNG PHI HP TR KHNG

ANTEN CA MY THU PHT VT JSS-720

I. Phn tch phn pht1. Khi pht ca JSS 720 bao gm cc khi:

+ Khi to tn hiu n bin SSB

+ Khi tng hp tn s v to tn s pht

+ Khi khuch i cng sut

+ Khi iu hng Anten

2. Nhim v cc khi:

+ Khi to tn hiu n bin SSB: Tn hiu ny c to ra bng cch iu ch tn hiuAF( tn hiu m thanh) vi tn s sng mang 455kHz. N c dng cho mch bin i

tn s bin i thnh tn s pht.

+ Khi khuch i cng sut: Khuch i bin tn hiu ln a ra Anten, loi

b tp m ra khi tn hiu.

+ Khi iu hng Anten: C nhim v bc x tn hiu ra ngoi khng gian, phi hp

tr khng vi tng khuch i cng sut.

3. Phn tcha, Khi to tn hiu n bin SSB

Dao ng thch anh to ra tn s 20MHz sau c a qua b chia 4 v a vo

mch vng kho pha PLL to ra tn s 455kHz.

+ Nguyn l to tn s 455kHz bng mch vng kho pha PLL.

S khi mch vng kho pha:

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11/26


Khi khng c tn hiu vo th tn hiu hiu chnh Ud =0 v tn hiu ra ca b tch sng

pha l tch (Uv x Ud ). Mch VCO dao ng ti tn s dao ng ring f = 455kHz. Khic tn hiu vo b tch sng pha s so pha tn s tn hiu vo vi tn hiu so snh. u

ra ca b tch sng pha xut hin tn hiu Ud m tr s tc thi ca n t l vi hiu pha

(hiu tn s) ca hai tn hiu vo thi im ng thi c cc thnh phn tn sfv fr

v fv + fr . Tn s tng b loi b nh mch lc thng thp cn tn s thp c

khuch i ln v c dng iu khin tn s dao ng ca VCO. Tn s dao ng

ca VCO c thay i sao cho fv fr tin ti 0 ngha l fv = fr hoc fr =N fv vi N

l h s chia ca b chia tn. y fv = 5MHz vy h s chia6

9110N= . Tn s 455kHz

c trn vi tn s AF ( tn s m thanh) to ra tn hiu n bin SSB.

455kHz

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Lc thngthp vK/

MchChia tn

VCO (f0)

fv

fr

tn hiu sai s

Ud

fr

Ud

fr

f

SSB

Uv , fv


12/26


Tn hiu d liu t b iu khin qua cng COM c khuch i m bo bin

tn hiu ln sau a vo b chuyn mch m tn (AF SW). CPU s iu khin

chuyn mch pht i cc tn hiu d liu v cc tn hiu ph: Tone, Alarm, Fs-In.

Tn hiu ra t chuyn mch AF c a ti b iu ch n bin (LSB MOD) iu ch vi sng mang fc = 455kHz to tn hiu SSB. Tn hiu sng mang fc to ra t

b dao ng ch bng thch anh DTCXO 20MHz. Tn hiu sau iu ch a qua b lc

bng (BPF) ly mt di bin tn. Qu trnh iu ch n bin ny nhm mc ch:

+ Gim rng di tn i mt na.

+ Cng sut ca my pht gim.

+ Tp m u thu gim do bin tn ca tn hiu hp hn.

B iu ch nhiu ch (VCA) xc lp ch lm vic ca my pht, c iuchnh bi tn hiu Gain-Cont t CPU. B iu ch ny thc hin iu ch tn hiu n

bin t b lc bng a ti vi sng mang chun fc = 455kHz to ra tn hiu sng

mang ph vi tn s 455kHz.

m bo cht lng ca tn hiu ngun nh:

+ Lc b tn s nh

+ m bo su iu ch

+ Gim nh yu cu vi cc mch lc,

b, Khi tng hp tn s v to tn s pht

Tn hiu mang tin tc c tn s 455kHz s c a ln tn s sng mang rt cao, vic

ny c thc hin nh cc b trn (MIX). u tin tn s sng mang 455kHz c

trn vi tn s fL1 = 70MHz to ra tn s 70.455MHz. Sau khi c khuch i v

qua b lc bng a ti b trn th hai, ti y n c trn vi tn s fL2 to tn

s pht f0. Tn s fL2 bin i trong mt khong t 70.055MHz n 97.955MHz lm

cho f0 bin i trong di tn t 1.6MHz n 27.5MHz. y chnh l di tn lm vic

ca my pht. Tn s fL2 ph thuc vo cc h s chia M,N ca cc b vng kho pha

(PLL).

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13/26


Tn s f0 sau khi qua b lc c a ti khi khuch i cng sut to cng

sut ln a ra Anten..

c,B khuch i cng sut gm:4 khi chc nng:

+ Tin khuch i (DRIVE AMP): Khng yu cu v h s khuch i m ch lm tngt s tn hiu trn tp m (S/N).

+ B chia tn hiu (POWER SPLITTER): Chia tn hiu t b tin khuch i thnh ba

ng tn hiu ring bit ti 3 b khuch i cng sut.

+ Cc b khuch i cng sut: Thc hin khuch i cng sut. Cc mch ny m

bo h s khuch i a ra cng sut ln.

+ B tng hp cng sut(POWER COMBINER): Tng hp cng sut t 3 b khuch

i cng sut.Mc ch ca vic s dng ba b khuch i cng sut ring r trong khi khuch i

cng sut l gim bt yu cu v h s khuch i, kh nng chu ti, phm cht

ca cc phn t khuch i do lm gim gi thnh thit b.

Tn hiu sau khi khuch i vi cng sut ln s c a ra Anten bc x

ra khng gian. phi hp tr khng gia anten v b khuch i cng sut phi dng

mch phi hp tr khng. Mt khc, my pht lm vic nhiu tn s khc nhau, Anten

ch lm vic vi mt tn s cng hng ring nh vy i hi phi c mch ra Anten b cc thnh phn cm hoc dung m bo cho anten lun lm vic ch cng

hng. B phi ghp Anten (ANTENNA TUNER) thc hin cc yu cu trn ca my

pht.

d,ANTENNA TUNER gm cc thnh phn sau:

+ SENSOR: y l t hp nhiu IC c xy dng t nhng mch thut ton, triger,

cc phn t tch cc, cm bin c nhim v so snh pha ca tn hiu dng v p nhm

pht hin s sai pha.

+ AUTOMATIC ANTENNA TUNER: Da trn s sai pha gia dng v p nhn c

t SENSOR t ng iu khin s phi ghp cuae anten anten lm vic ch

cng hng.

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14/26


II. Phn tch phn thu

* S NRD-740

1. Phn thu gm cc khi:

+ Mch vo

+ Mch K/ cao tn

+ Mch i tn

+ Mch K/ trung tn

+ Mch tch sng

+ Mch khuch i cng sut2. Nhim v cc khi:

+ Mch vo: c nhim v chn lc tn s cn thu. Tn hiu c chn a vo khi

K/ cao tn, y khng quan trng h s khuch i m iu quan trng l t s S/N.

+ Khi i tn: trn tn s t khi khuch i cao tn vi tn s khi dao ng ni

a ra tn s khng i Ftt tn s ny c a qua khi khuch i na, tng khuch

i ny quyt nh nhy ca my thu.

+ Mch K/ trung tn: Khuch i tn hiu ln.+ Khi tch sng: Tch tn hiu cn thu ra khi sng mang cao tn.

+ Khi khuch i cng sut: Khuch i cng sut tn hiu ln a ra loa.

3.Phn tch

Tn hiu t anten i vo my thu, trc tin n i qua mch TEST th xem my

sn sng lm vic cha, sau c a qua mch bo v ARRESTER v

BKRELAY mch ny c tc dng bo v my thu khi m tn hiu t my pht ln c

a ti anten nhng khng vo my thu do lc ny rle c ngt ra khi anten. V

my thu lm vic di tn rt rng do m bo nhy my thu mch vo ca

my thu ngi ta chia thnh 8 mch vo di rng, khi cn thu on tn s no mch

iu khin s ng mch vo tng ng vi on tn s , ng m cc mch vo

ta s dng chuyn mch bng diot.

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15/26


- S chuyn mch s dng diot:

Bnh thng ta cp cho catt ca hai diot mt in p m hoc l 0V do cc

diot khng thng nn mch vo ng, khi cp in p dng cho catot hai diot thng

nn mch vo m cho tn hiu i qua ( ngi ta tnh ton sao cho bin in p cu

tn hiu vo phi nh hn bin in p mt chiu cp cho catot ca diot). Tn hiu t

chuyn mch diot c a vo b lc thng thp 35MHz mch lc ny ch cho qua tn

s nh hn hoc bng tn s 35MHz, sau c a ti mch khuch i cao tn

mch ny ch c tc dng nng cao t s S/N.

Tn hiu ra ca b khuch i cao tn c trn ln th nht vi tn s dao ng

ni(70.455 ~ 100.454999MHz) t b dao ng LOOP1 tn hiu sau b trn c a

vo mch lc c tn s 70.455MHz, vic chn lc tn hiu cn thu do dao ng

ni t LOOP1 tn s ny qua b khuch i trung tn loi b tn s nh ng thi

chng nhiu-pha inh sau c trn ln th hai vi tn s 70MHz t LOOP2 a tn

s trung tn cao xung thp tr v tn s ban u 455KHz, tn hiu i tip qua rle, qua

mch lc thng thp 455KHz c di thng 12KHz.

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D2

Ur

L

C1

D1

Uv

C2


16/26


ng thi tn hiu 455kHz c a vo mch lc tp m. Tip theo tn hiu c a

vo b lc bng gm 4 di tn: 0.3KHz, 1KHz, 3KHz, 6KHz. Tn hiu 455KHz a

qua 4 b khuch i trung tn ( bn b khuch i trung tn ny nhm tng h s

khuch i v tng nhy ca my thu) tn hiu ra t b khuch i trung tn th ba i

qua mch khuch i sng mang (CAR AMP) i vo b gii iu ch (DEMO) cng

vi tn hiu t b khuch i trung tn th ba. Tn hiu gii iu ch c a vo b

SQLMUTE qua b iu chnh to nh (volume) iu chnh tn s theo mun v qua b

khuch i m thanh a ra loa.

+ LOOP1: To dao ng ni quyt nh tn s cn thu, to tn hiu TESTL1.

+ LOOP2: To ra tn s dao ng ni th hai, to ra tn hiu TESTL2.

+ CPU: iu khin qu trnh lm vic ca cc khi trong my thu.

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455KHz

12Khz


17/26


III. i su phn tch b phi hp tr khng anten JSS-720.

1. Khi qut:

mt trong nhng yu t quyt nh n cht lng ca my pht l vic phihp tr khng gia tng KCS v anten anten c th bc x tt nht sng in t

ra khng gian. khi anten lm vic ch cng hng.

nu my pht s dng mt tn s th ch cn s dng mt anten pht. do nu

my pht s dng nhiu tn s pht th my pht s phi s dng nhiu anten

pht nn s gy lng ph v cng knh.

Vn t ra l s dng my pht nhiu tn s ch s dng mt anten pht khc

phc nhc im trn chnh l phng php m rng di tn lm vic ca antenpht hay iu hng anten pht.

khc phc nhc im trn ngi ta s dng mt mch ghp anten mch ny

ghp gia tng khuych i cng sut v anten.

s khi:

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18/26


S tng ng ca anten:

T s tng ng ca anten ta nhn thy rng anten gm c ba thnh phn:

phn cm LA , thnh phn in dung CA , v thnh phn tn hao RA

trong ba thnh phn trn th thnh phn RA khng ph thuc vo tn s ch c hai thnh

phn LA v CA lph thuc vo tn s t vo anten.

Tr khng ca anten l:

ZA=RA + j(XL XC)

trong

CX

LX

A

A

C

L

1=

=

Khi anten cng hng tn s 0 th ta c:

LC

XXAA

CL

1

0==

=

Khi cng hng th anten bc x cng sut ra khng gian l ln nht

khi lch tn s cng hng ring ca anten 0 th khi anten c th mang tnh

dung hoc tnh cm khi anten bc x cng sut ra khng gian thp. trong trng hp

ny mch ghp s c tc dng b thnh phn cm nu anten mang tnh dung v b

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19/26


thnh phn dung nu anten mang tnh cm anten c th cng hng vi bt k thnh

phn no ca tn s pht.

mch ghp anten gi l tng ra ca my pht.

Mch ra yu cu phi m bo cong sut ra v hiu sut ra cao. hiu sut ra ca mch ras quyt nh hiu sut ca ton my pht v cng sut ca tng ra chim 90% cng sut

ton my pht.

iu khin cc mch ra ny thi trong my thu pht JSS-720 ngi ta s

dng cc b vi iu khin v cc cm bin v pha cm bin v

ti cm bin v t s sng ng.

Sau y ta s phn tch cc b cm bin s dng trong my thu pht JSS 720.

2.S khi ca b iu hng:

B iu hng anten gm cc b phn chnh sau:

+ Mch cm bin

+ Mch iu khin

+ Mch bo v

+ Mch phi hp tr khng

Trong khun kh bi tp ln ny ta s ch phn tch chi tit mch cm bin

(sensor) ca b phi hp tr khng.

Mch cm bin bao gm cc b cm bin : cm bin pha ,cm bin SWR (Standing

Ware Ratio), cm bin tr khng ti.

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Cm bin Mch phi hp

iu khin Bo v

Kim tra dnganten

anten

NFC 801/802


20/26


a, B cm bin v pha (phase sensor )

s khi ca b cm bin pha:

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21/26


v nguyn tc so snh pha gia dng in v in p th chng ta phi

chuyn v cng mt i lng dng in hoc in p sau a vo so snh. y

ngi ta chuyn v in p, nguyn l hot ng ca cm bin nh sau:

trn ng dy tn hiu dn t my pht ra anten ngi ta t mt cm bin dng, trn

cun th cp ca cm bin dng ta mc mt in tr R1 ly tn hiu in p a vo

chn 4 v 5 ca IC1 nu dng trn ng tn hiu cng ln th in p a vo IC1

cng tng theo( ngoi tr trng hp chp ti khi s khng c dng cun th cp

ca bin p dng) IC1 c tc dng so snh in p cm bin c t cm bin dng vi

mt mc in p ngng nht nh. khi in p vo ln hn mc ngng th in p ra

chn 15 ca IC1 s mc thp ngc li th cho ra mc cao.

ly pha ca in p ngi ta trch mt phn in p t ng tn hiu qua mch

phn p vi cc thnh phn R10, R11, R12, R18 v t C23 v a vo chn 4 v 5 ca

IC4. IC4 hot ng cng tng t nh IC1.

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22/26


u vo ca IC1 v IC4 c mc thm cc t C1 v t C24 ngn mch thnh phn

cao tn. Cc dit CD2 v CD4 c tc dng nh mt mch ghim mc 0v, cc it CD3

v CD1 bo v qu ti cho IC1v IC4 tc l khi in p cm bin ln hn 5v th it

CD1 v CD3 thng v s hn dng vo IC.Vic so pha c thc hin nh D plipplop:

tc l u ra ca IC1(chn 15 ) a vo chn D ca plipplop cn u ra ca IC10 a

vo chn CE (Chip Enable ) ca plipplop.

mc in p u ra ca IC3 s cho bit tr khng ca mch ra anten mang tnh cm hay

tnh dung.

Nu in p u ra IC3 mc cao th s mang tnh cm.

nu in p du ra ca IC3 mc thp th tr khng s mang tnh dung.in p ny s c bin i A/D ri a v vi x l.

Ngoi tn hiu so pha th vi iu khin cn a ra tn hiu tt b so pha (phase sensor

off ) bnh thng tn hiu ny mc thp th b so pha hat ng bnh thng nhng

khi n c a ln mc cao th s lm cho Transistor TR3 thng, TR1 v TR2 kho

lm cho in p u vo IC4 rt nh dn ti u ra 15 mc tch cc cao lm cho chn

CE (Chip Enable ) ca D plipplop cng mc cao nn lm cho D plipplop ngng lm

vic.b, B cm bin t s sng ng (SWR ) :

Khi khng phi hp tr khng gia tng PA v Anten, th c sng phn x. S

phn x nhiu hay t c c trng bi t s song ng SWR-Standing Wave Ratio.

S mch:

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23/26


Mch ny lm nhim v cm bin v t s in p sng ng SWR(bng cch so

pha ca dng pht i v dng phn x) thng qua hai tn hiu Vf v Vr. Trong Vf l

tn hiu a ra tng trc(sng pht i; Vr l tn hiu phn hi v tng sau(song phn

x).

Cm bin Vf: tn hiu ra anten qua cm bin dng T2 chuyn t dng thnh p i

qua diode CD5 , so snh tn hiu cm bin v in p ly t C11 v C13.vi tn hiu

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24/26


cm bin o pha ly t bin p dng T2.Tn hiu ny c ua dn b so snh

IC5A thng qua R22,L59.

Cm bin Vr: tn hiu ly t diode CD5.CD5 so snh tn hiu cm bin v in

p ly t C12 v C14.vi tn hiu cm bin o pha ly t bin p dng T2.Tn hiu

ny c ua dn b so snh IC5B thng qua R23,L60.

C9,C10,R33,R34,C59,C60 lm nhim v lc thnh phn bin i.

Sauk hi i qua IC5A v IC5B tn hiu s c ly ra t chn 7&1 ca 2 IC ny

v chng c a ti vi x l thng qua 2 mch lc bao gm C39,L53,C33(v

C41,L55,C35).

c, B cm bin ti (LOAD):

S mch:

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25/26


Mch bao gm cm bin dng T3,diode CD7 ,CD8; in tr R26~R31; t in

C16~C20; cun cm L7~L9.B cm bin ny s cm bin v cho ta bit v tr khng ca anten (ti)

nguyn l ca b cm bin ny l n so snh v ln ca dng v p ra anten.

hot ng ca mch nh sau:

u ra ca cun th cp ca bin p dng s c mc vi in tr R27,

R26 ly p in p ny s c nn ly in p 1 chiu a vao b so snh IC3.

Trn ng dy tn hiu ngi ta trch ra in p v qua dit nn ly in p mt

chiu a vao chn o ca b so snh.

u ra ca b so snh s cho bit tr khng ca anten ln hn 50 hay nh hn 50

.

Nu chn load mc cao th tr khng ca anten nh hn 50 .

Nu chn load mc thp th tr khng ca anten ln hn 50 .

trang:25


26/26


IV. KT LUN.

Nh vy,qua vic phn tch s h thng ta thy i hi khi lng cc kin

thc tng quan, cch thc lin h gia c s l thuyt v thc tin .Qu trnh phn tchl qu trnh tng hp li cc kin thc cc phng php nghin cu.Yu t nh hng

nhiu trong qu trnh phn tch mt h thng chnh l mt kin thc c bn, khi nm

chc iu trnh t phn tch c p dng l chia nh theo tng khi ,thc hin phn

tch chc nng nhim v ca khi ,ri thc hin lin kt cc khi con trong ton

b h thng c cch nhn tng th nht.

c th gii thch ti sao mch hay khi li lm nhim v g, ti sao dung phn

t ,hay ti sao li s dng gii php ny m khng s dng phng n khc?th ihi ngi phn tch phi mc ni cc phn lin h trn cc nguyn tc c bn,thc hin

pht trin khi c s h tr ca cc linh kin thay th.

Qu trnh phn tch s khi cng nh i su phn tch chi tit mt module c th

trong my v tuyn JSS-720 gip em c c phng php phn tch mt h thng

c chinh xc,nhng r do hn ch v mt kin thc cung nh ti liu tham kho do

khng trnh khi nhng sai st trong qu trnh tm hiu v phn tch, rt mong c

s gp ca thy c v bn b bi phn tch c chnh xc v hon chnh hn.

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