[UpdateBook.vn]-Ky Thuat Dieu Che Trong Thong Tin Vo Tuyen

7/30/2019 [UpdateBook.vn]-Ky Thuat Dieu Che Trong Thong Tin Vo Tuyen

1/22

N TRUYN DN V TUYN GVHD: THS. NGUYN V ANH QUANG

LI NI U

Vo u th k 20 Marconi thnh cng trong vic lin lc v tuyn qua i Ty

Dng, Kenelly v Heaviside pht hin mt yu t l tng in ly hin din tng

pha trn ca kh quyn c th dng lm vt phn x sng in t. Nhng yu t

m ra mt k nguyn thng tin v tyun cao tn i quy m.Chin tranh th gii ln th hai l mt bc ngot trong thng tin v tuyn.

Thng tin tm nhn thng - lnh vc thng tin s dng bng tn s cc cao (VHF)

c nghin cu lin tc sau chin tranh th gii - tr thnh hin thc nh s pht

trin cc linh kin in t dng cho VHF v UHF, ch yu l pht trin ngnh

raa.Vi s gia tng khng ngng ca lu lng truyn thng, tn s ca thng tin v

tuyn vn ti cc bng tn siu cao (SHF) v cc cao (EHF). Vo nhng nm

1960, phng php chuyn tip qua v tinh c thc hin v phng php chuyn

tip bng tn x qua tng i lu ca kh quyn xut hin. Do nhng c tnh u

vit ca mnh nh dung lng ln, phm vi thu rng, hiu qu kinh t cao, thng tin v

tuyn c s dng rt rng ri trong pht thanh truyn hnh qung b, v tuyn o

hng, hng khng, qun s, quan st kh tng, lin lc sng ngn, thng tin v tinh -

v tr v.v... Tuy nhin, can nhiu vi lnh vc thng tin khc l iu khng trnh khi,

bi v thng tin v tuyn s dng chung phn khng gian lm mi trng truyn dn.

Chnh v th iu ch tn hiu l mt phn khng th thiu c trong truyn dn

ca thng tin v tuyn. iu ch gip chng ta c th truyn i thng tin hoc tn hiumong mun v nhn c nhng tn hiu m mnh mun c.

n c chia lm ba phn :

CHNG 1: GII THIU CHUNG V IU CH

CHNG 2: MT S LOI IU CH

CHNG 3: M PHNG TN HIU VI MATLAB

Do thi gian khng nhiu nn trong khi tm hiu chng em cn nhiu thiu st

mong thy c v cc bn gp bi lm hon chnh hn.Xin chn thnh cm n !

SVTH: VN BNH HNG PHONG 1


2/22


MC LC

1.3.2 Phn loi theo s thay i ca cc tham s sng mang ............................................. 5Tn s tc thi cho bi : ..................................................................................................10

Hnh 2.12 iu ch pha 2PSK ..................................................................................................14



3/22


DANH MC HNH NH

1.3.2 Phn loi theo s thay i ca cc tham s sng mang ............................................. 5Tn s tc thi cho bi : ..................................................................................................10

Hnh 2.12 iu ch pha 2PSK ..................................................................................................14



4/22


DANH MC T VIT TT

T vit tt Ngha ca cc t Chc nng

BER Bt Error Rate S bt b li

FSK Frequency Shift Keying iu ch tn s s

AM Amplitude Modulationiu ch bin

tng t

ASKAmplitude Shift Keying

iu ch bin s

QAM Quature Amplitude Modulation iu bin cu phng

PSK Phase Shift Keying iu ch pha s

BASK Binary Amplitude Shift Keying iu ch kha dchbin nh phn

OOK On off keying iu ch kha on-off

STR Symbol Timing Recovery B khi phc ng b

BPSK Binary Phase Shift Keyingiu ch kha dch

pha nh phn

BFSK Binary Frequency Shift Keyingiu ch kha dch

tn nh phn

QPSK Quadrature Phase Shift Keying iu ch kha phacu phng

FM Frequency Modulationiu ch tn s tng

t

DFM Differential Frequency ModulationPh ca tn hiu iu

tn s



5/22


CHNG 1 GII THIU CHUNG V IU CH

1.1 Khi nim iu ch

iu ch (modulation) ni chung l lm bin i cc c tnh ca mt tn hiu

theo mt tn hiu khc. Trong h thng thng tin tn hiu b bin i theo sng mang

(carrier). C th nh ngha iu ch l s bin i cc thng s ca tn hiu mang tintheo sng mang.

1.2 Mc ch iu ch

Mc ch chnh ca iu ch l gn tn hiu mang tin (thng l bng gc) vo tn hiu

song mang c ph thch hp hn, to thnh tn hiu thng di :

- Lm cho tn hiu mang tin tng xng vi cc c im ca knh truyn.

- Kt hp cc tn hiu li vi nhau (s dng ghp knh phn tn s) ri truyn i

qua mt mi trng vt l chung.- Bc x tn hiu dng cc anten c kch thc ph hp thc t.

- nh v ph v tuyn nhm gi cho giao thoa gia cc h thng di mc cho

php.

1.3 Phn loi iu ch

1.3.1 Phn loi theo tn hiu a vo iu ch

- iu ch tng t : tn hiu iu ch l tn hiu tng t.

- iu ch s : tn hiu iu ch l tn hiu s.

1.3.2 Phn loi theo s thay i ca cc tham s sng mangiu ch bin : l tc ng tn hiu iu ch vo sng mang lm cho bin

ca sng mang thay i theo quy lut ca tn hiu iu ch. iu ch bin tng t

c gi l AM (Amplitude Modulation). iu ch bin s c gi l ASK

(Amplitude Shift Keying).

iu ch tn s: l tc ng tn hiu iu ch vo sng mang lm cho tn s ca

sng mang thay i theo quy lut ca tn hiu iu ch. iu ch tn s tng t cgi l FM (Frequency Modulation). iu ch tn s s c gi l FSK (Frequency

Shift Keying).

iu ch pha: l tc ng tn hiu iu ch vo sng mang lm cho pha ca sng

mang thay i theo quy lut ca tn hiu iu ch. iu ch pha tng t c gi l

PM (Phase Modulation). iu ch pha s c gi l PSK (Phase Shift Keying).

iu ch QAM (Quature Amplitude Modulation): l phng php iu ch kt

hp c iu ch bin ASK v iu ch pha PSK. Vi iu ch ny th khi tn hiu

iu ch tc ng vo sng mang th c bin v pha ca sng mang u thay i

theo quy lut ca tn hiu iu ch.



6/22


CHNG 2 MT S LOI IU CH

2.1 iu ch tn hiu tng t

2.1.1 iu ch tn s (FM)

FM l vit tt ca ( Fryquency Moducation : iu ch tn s ) l iu ch theo phng

thc lm thay i tn s ca tn hiu cao tn theo bin ca tn hiu m tn, khong tn sbin i l 150KHzSng FM l sng cc ngn i vi tn hiu Radio, sng FM thng pht di tn t

76MHz n 108MHz

Hnh 2.1 Mch iu ch tn s FM

Vi mch iu ch tn s th sng mang c bin khng i, nhng tn s thay

i theo bin ca tn hiu m tn, khi bin tn hiu m tn tng th tn s cao tn

tng, khi bin m tn gim th tn s cao tn gim. Nh vy sng mang FM c tn

s tng gim theo tn hiu m tn v gii hn tng gim ny l +150KHz v -150KHz ,

nh vy tn s sng mang iu tn c di thng l 300KHZ.

Th d nu i ting ni vit nam pht trn sng FM 100MHz th n truyn i

mt di tn t 99,85 MHz n 100,15 MHz.

Hnh 2.2 Dng sng ca mch iu ch tn s FM.

a Tn hiu iu ch; b Sng mang; c Tn hiu sau khi iu ch

u v nhc im ca sng FM.

Sng FM c nhiu u im v mt tn s, di tn m thanh sau khi tch sng iu

tn c cht lng rt tt, cho m thanh trung thc v c th truyn m thanh Stereo ,

sng FM t b can nhiu hn s vi sng AM.



7/22


Nhc im ca sng FM l c ly truyn sng ngn, ch truyn c c ly t vi

chc n vi trm Km , do sng FM thng c s dng lm sng pht thanh trn

cc a phng.

2.1.2iu ch bin (AM)

iu ch AM l qu trnh iu ch tn hiu tn s thp( nh tn hiu m tn, tnhiu video ) vo tn s cao tn theo phng thc => Bin i bin tn hiu cao tntheo hnh dng ca tn hiu m tn => Tn hiu cao tn thu c gi l sng mang.

Hnh 2.3 Tn hiu vo v ra ca mch iu ch AM

Tn hiu m tn c th ly t Micro sau khuch i qua mch khuch i m

tn, hoc c th ly t cc thit b khc nh i Cassette, u a CD .

Tn hiu cao tn c to bi mch to dao ng, tn s cao tn l tn s theoquy nh ca i pht.

Tn hiu u ra l sng mang c tn s bng tn s cao tn, c bin thay i

theo tn hiu m tn.

2.1.2.1 Qu trnh pht tn hiu i pht .

Hnh 2.4 Qu trnh pht sng Radio AM



8/22


Tn hiu sau khi iu ch thnh sng mang c khuch i ln cng xut hng

ngn Wat sau c truyn ra Anten pht .

Sng in t pht ra t Anten truyn i trong khng gian bng vn tc ca nh

sng, sng AM c th truyn i rt xa hng ngn Km v chng truyn theo ng

thng, v cng c cc tnh cht phn x, khc x nh nh sng.2.1.2.2 ng truyn t i pht n my thu cch na vng tri t.

Vi cc i pht xa cch chng ta na vng tri t nh i BBC pht t Anh

Quc, sng in t truyn theo ng thng gp tng in ly chng phn x xung tri

t ri li phn x ngc ln nhiu ln mi n c my thu, v vy tn hiu i ti

my thu rt yu v sng khng n nh

c th truyn tn hiu i xa, cc i pht thng pht bng sng ngn c tn sng

mang t 4 MHz n khong 23 MHz .

Hnh 2.5 ng truyn sng ca cc i pht xa my thu2.1.2.3 u v nhc im ca pht thanh trn sng AM

u im : ca sng AM l c th truyn i xa ti hng nghn Km

Nhc im : ca sng AM l d b can nhiu, di tn m thanh b ct sn do c

im ca mch tch sng iu bin, do cht lng m thanh b hn ch.



9/22


2.1.3 iu ch cu phng QAM

iu bin cu phng QAM l phng php m ha d liu trn mt tn s sng

mang n. S m ha d liu bng cch thay i c bin v pha cua sng mang. QAM

dng mt dng sng sine v mt dng sng cosine vi cng b phn to tn s

chuyn i thng tin. Cc sng ny c gi ng thi ln knh truyn, bin misng cha tin c gi.

Hnh 2.6 M hnh iu ch QAM

Trong b iu ch QAM, nhnh thc hin bin sng cosine cn gi l nhnh phase,

bin cosine gi l phase hay I. nhnh thc hin bin sng sine gi l nhnh cuphng, bin sine gi l cu phng hay Q.

Tnh trc giao gia sng sine v cosine cho php truyn d liu ng thi trn

knh. Xem xt mt chu k n mi sng, nguyn l trc giao c th trnh by nh m

hnh 2.6.

ng dng iu ch QAM

- 64-QAM v 256-QAM thng s dng trong truyn hnh cp, k thut s v

cc ng dng modem cp.

- H thng truyn thng c thit k t c mc rt cao v hiu qu

quang ph thng thng s dng cc chm sao QAM rt dy c.

2.1.4 iu ch pha ( PM)

L tc ng tn hiu iu ch vo sng mang lm cho pha ca sng mang thay i

theo quy lut ca tn hiu iu ch. iu ch pha tng t c gi l PM (Phase

Modulation).

Nu gc pha thay i theo tn hiu thng tin ta c iu ch pha.

( ) ( )0 cosPM o pe t A t m g t = + trong mp l di pha cc i


Thitlp bitu vo

Tmgi tr(x,y)

my pht sngcosine

my pht sng sine

X

X

Gi tr x

Gi tr y

Nhnh I

Nhnh Q+ Dng

sng ra


10/22


Tn s tc thi cho bi :

( ) ( )( )

/i cdg t

t d t dt mpdt

= = +

Nu g(t) c dng cos mt th

( ) sin

( ) cos sin

i c p m m

PM c c p m

t m t

e t A t m

=

=

So snh hai cng thc trn xem mp l ch s iu ch pha, tng ng vi mr trong

FM, ta c th xc nh c bng thng ca tn hiu PM. L di tn tng ng

ca PM

( )2 m p m

p p ep

BW m ra

m

= =

=

2.2 iu ch tn hiu s

2.2.1 iu ch kha dch bin nh phn (BASK)

Trong h thng BASK, bin ca sng mang tn s fc c chuyn i gia hai

gi tr ty thuc vo tn hiu bng gc, bin ca sng mang bao gm hai mc A0 v

A1 biu din cho hai k t 0 v 1 tng ng. Trong thc t, dng sng BASK gm ccxung mark biu din k t 1 v space biu din k t 0. Lc ny BASK cn c

gi l biu din kha on-off OOK v k hiu BASK c biu din nh sau :

+

=

tfT

tA

tfT

tA

tf

00

00

2cos

2cos

)(

B iu ch OOK c th c thc hin nh l mt kha chuyn mch n gin,kha sng mang on hay off ty tn hiu mang tin l 1 hay 0 hoc l mt b iu ch

cn bng, nhn sng mang vi tn hiu OOK n cc bng gc. B tch sng OOK c

th l kt hp hay khng kt hp. Trng hp ny tch sng kt hp c th dng mt

b lc phi hp, u ra ca b lc phi hp t cc i khi u vo c tn hiu v bng

0 khi u vo khng c tn hiu. Hoc dng b tch sng tng quan, yu cu l phi

c b khi phc sng mang CR. Tn hiu sau c ly mu v quyt nh ngng

vi ng h ly ra t b khi phc ng h STR.

Kiu tch sng khng kt hp c s dng ph bin hn, c cu thnh hai

knh tng quan tch thnh phn ng pha v vung pha ca tn hiu, sau bnh


Cho s 1

Cho s 0


11/22


phng thnh phn ng pha v vung pha ri sau cng li. S sp xp ny khc

phc c yu cu v ng b pha sng mang. Kiu ny phc tp nhng vi s pht

trin ca cng ngh VLSI, chng tr nn nh, nh v r hn so vi b lc v tch

ng bao trong cc thit k truyn thng.

Hnh 2.7 iu ch on-off: dng sng, b iu ch, ph

a Tn hiu bng gc

b Ph in p ca tn hiu bng gc

c B iu ch OOK

d Tn hiu OOK thng di

e Ph in p ca tn hiu OOK thng diThi im quyt nh b quyt nh bn thu l f(nT 0) v in p quyt nh l:

=0

)( 10kE

nTf

Trong E l nng lng chun ha cha trong k t 1 v k l hng s, c th t

bng 1.

Trng hp s dng b lc phi hp, xc xut li c tnh nh sau:

=

21

1

1

2

11

2

1

N

EerfPe

Trong N l PSD ca nhiu, erf(x) l hm li

t ( )2121

EEE += l nng lng trung bnh theo thi gian trn mt k t, vi OOK

th E0=0, ta c:

= 2

1

0211

21

NEerfPe


Chn s 1Chn s 0


12/22


Hnh 2.8a B thu dng b lc phi hp;b B thu tng quan

c B thu tch sng ng bao; d B thu 2 knh

2.2.2 iu ch pha cu phng QPSKKhi thit k h truyn thng ngoi mc tiu quan trng l xc sut li bit phi

thp cn c mc tiu l s dng c hiu sut rng bng. Kha dch vung pha l

trng hp ring ca hp knh sng mang vung gc, mi dng sng mang thng

tin 2 bit nn cn tt c 4 dng sng ng vi 4 pha c hiu sut bng tn cao.

Hnh 2.9 Dng sng ng vi tn hiu 01 10 10 00

2.2.3 iu ch tn s vi tn hiu s (FSK)



13/22


Khi tn hiu iu ch l tn hiu s th iu ch tn s c gi l FSK

(Frequency Shift Keying: kha dch tn s). Hin nay c nhiu kiu iu ch FSK: 2

FSK, 4 FSK, 8 FSK ...

Hnh 2.10 S khi mch iu ch 2FSK

- LO1 v LO0: hai b dao ng c lp: LO1 to ra sng mang c tn s f1, LOo to

ra sng mang c tn s fo.

- Mo v M1: cc cng truyn dn c iu khin bi tn hiu iu ch.

- : b cng c nhim v kt hp cc sng mang fo v f1 to thnh tn hiu 2FSK.

Nguyn l hot ng ca mch hnh 4.14 nh sau: Mch dao ng LO0 to ra

tn hiu sng mang c tn s fo a n ng vo ca cng truyn dn Mo. Mch dao

ng LO1 to ra sng mang c tn s f1 a n ng vo ca cng truyn dn M1. Tn

hiu iu ch c a n iu khin cc cng truyn dn Mo v M1. Khi tn hiuiu ch l bit 0 th cng truyn dn M1 khng c iu khin nn khng cho tn hiu

sng mang f1 i qua, cng truyn dn Mo c iu khin nn cho tn hiu sng mang

fo i qua. Khi tn hiu iu ch l bit 1 th cng truyn dn Mo khng c iu khin

nn khng cho sng mang fo i qua, cng truyn dn M1 c iu khin cho sng

mang f1 i qua. Mch cng kt hp cc tn hiu ng ra ca cc cng truyn dn Mov M1. Kt qu l ng ra ca mch cng ta thu c sng mang iu ch 2 FSK

gm hai tn s fo v f1 ng vi cc bit s liu a vo iu ch.



14/22


Hnh 2.11 Dng sng iu ch 2FSK

a) Tn hiu iu ch, b) Sng mang f0 ,

c) Sng mang f1, d) Sng mang sau iu ch

2.2.4 iu ch pha hai trng thi (2 PSK)

Hnh 2.12 iu ch pha 2PSKa) S khi ca mch iu ch 2 PSK. b) Dng sng ca iu ch 2 PSK.

c) Biu pha ca iu ch pha 2 PSKiu ch pha hai trng thi l iu ch m sau khi iu ch sng mang iu

ch c hai trng thi pha so vi pha ca sng mang cha iu ch.

S liu nh phn cn iu ch trc ht c a vo mch chuyn m bin

i t m NRZ n cc sang NRZ lung cc. Sau , s liu c a n b nhn M

nhn vi sng mang 2. cos( )A t o + to ra t mch to dao ng sng mang.

ng ra ca b nhn ta thu c mt tn hiu m thnh phn chnh l d(t)

2. cos( )A t to + + v mt s thnh phn pht sinh khng mong mun. Cc tn hiuny c a qua mch lc bng loi b cc thnh phn khng cn thit. Kt qu,

ng ra ta thu c mt tn hiu iu ch 2 PSK:

U t d t A t o( ) ( ) . cos( )= +2 . Trong : d(t) l s liu s cn iu ch, o: pha ban

u ca sng mang, A 2 : bin ca sng mang.

V b nhn M nhn tn hiu iu ch d(t) vi sng mang 2. cosA t theo min

pha nn c th vit li U(t) nh sau:U t A t t o( ) .cos( )= + +2



15/22


Trong t l gc lch pha do s liu iu ch gy ra ti thi im iu ch ( t = 0

hoc t = ). D dng nhn thy rng khi s liu iu ch l bit 0 th d(t) = -1 v sng

mang sau iu ch l:U t A t o( ) .cos( )= + +2 0 .

Khi s liu iu ch l bit 1 th d(t) = 1 v sng mang sau iu ch l:

U t A t o( ) .cos( )= + +2

Nh vy sng mang sau iu ch pha c hai trng thi l ng pha vi sng mang

cha iu ch (khi iu ch bit 0) v ngc pha vi sng mang cha iu ch (khi iu

ch bit 1). Pha thu s da vo s chuyn pha ca sng mang thc hin gii iu

ch.

2.2.5 iu ch ASK

iu ch ASK l iu ch bin p dng cho tn hiu iu ch l tn hiu s.

Hnh 2.13 iu ch ASK

- S(t): tn hiu iu ch (tn hiu s)- LO: mch dao ng to sng mang (Local Ocsilator)

- A.sint: sng mang c to ra t mch dao ng LO

- M: B nhn

- BPF: b lc thng bng (BPF: Band Pass Filter)

- S(t).Asint: sng mang c iu ch bin .

Hnh 2.14 Dng sng ca iu ch ASK



16/22


a) Tn hiu iu ch b) Sng mang c) Sng mang sau iu ch

Tn hiu iu ch S(t) l tn hiu s c a n u vo th nht ca b nhn

M. Sng mang A.sint to ra t b dao ng LO c a n u vo th hai ca b

nhn. B nhn M s nhn tn hiu iu ch S(t) vi tn hiu sng mang A.sint. u

ra ca b nhn ta thu c thnh phn c bn l S(t).Asint v mt s thnh phnkhc (v d A.sin2t, S(t).A sin3t ...). Tn hiu ny c a qua b lc thng gii loi b cc thnh phn khng mong mun. Kt qu u ra ca b lc ta thu c

tn hiu iu ch bin (ASK) l S(t).Asint.

iu ch ASK c u im l mch in iu ch v gii iu ch u rt n

gin. Tuy nhin c nhc im rt ln l kh nng chng nhiu thp v nhiu d dng

tc ng vo vng bin (vng mang tin ca sng mang iu ch ASK).



17/22


CHNG 3 M PHNG TN HIU IU CH VI MATLAB

3.1 M phng tn hiu iu ch s

Cc bn m phn mm m phng Matlab v chy chng trnh, khi bn th s

xut hin ra mn hnh chnh ca chng trnh m phng tn hiu iu ch.

Hnh 3.1 Giao din m phng tn hiu iu ch

Mn hnh xut hin bn hy nhp cc gi tr bin sng mang, tn s sng

mang v chui nh phn. Bt u iu ch cc tn hiu pha di.

Hnh 3.2 iu ch ASK



18/22


iu ch ASK (Amplitude Shift Keying) l iu ch bin s vi cc gi tr cho sn

Hnh 3.3 iu ch FSK

iu ch FSK (Frequency Shift Keying)l iu ch tn s svi tn s sng mang th

nht l 3 v tn s sng mang th hai l 4 v chui nh phn l 1 1 0 0 1 1 0 1 0

Hnh 3.4 iu ch OOK



19/22


iu ch On Off keying (OOK) l iu ch kha on-off vi bit 0 tn hiu iu ch

ging vi bit 0 ca tn hiu nh phn, bit 1 ca tn hiu iu ch OOK ging vi tn

hiu sng mang.

Hnh 3.5 iu ch PSK (Phase-shift keying)



20/22


Hnh 3.6 iu ch DPSK

iu ch DPSK (differential phase- shift keying) iu ch pha svi sai l k thut

iu ch khng ng b(khng cn xc nh pha sng n).

Hnh 3.7 iu ch QAM

iu ch QAM (Quadrature Amplitude Modulation) iu ch bin cu phng

Hnh 3.8 Kt thc chng trnh iu ch s



21/22


3.2 M phng tn hiu iu ch tng t

Hnh 3.9 Tn hiu iu ch AM

Hnh 3.10 Tn hiu iu ch PM



22/22


Hnh 3.11 Tn hiu iu ch FM

TI LIU THAM KHO

[1] Cc h thng thng tin hin nay Proakis J.G v Salehi M

Bin Dch TS. Nguyn Quc Bnh KS. Nguyn Huy Qun

[2] Tm tt bi ging in t thng tin - Th.S. Nguyn Trng Hi

[3] L thuyt tn hiu - Th.S L Xun K

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[UpdateBook.vn]-Ky Thuat Dieu Che Trong Thong Tin Vo Tuyen