loc thich nghi

N TT NGHIP Trang i

Phn A : Gii thiu

PHN A :

GII THIU

N TT NGHIP Trang ii

Phn A : Gii thiu

LI CM N Nhm thc hin ti xin c gi li cm n chn thnh n qu Thy

c trong khoa in in T, v nht l qu Thy c thuc b mn in T

Vin Thng ging dy v truyn t kin thc chuyn ngnh cho ngi

thc hin n trong thi gian va qua.

c bit nhm thc hin xin gi li cm n su sc ti thy Ng Quc

Cng v s tn tnh hng dn cng nh to nhng iu kin thun li

nht cho ngi thc hin n c th thc hin v hon thnh tt ti

ny.

Nhm thc hin n cng khng qun cm n cc bn trong lp trao

i, g p ngi thc hin hon thnh ti ny mt cch tt p v ng

thi gian.

Mc d c nhiu c gng v n lc thc hin, nhng do kin thc cng

nh kh nng bn thn cn nhiu hn ch nn trong qu trnh thc hin ti

khng th trnh khi nhng sai phm, thiu s tRt mong nhn c s gp

, ch dn t ni qu thy c v cc bn sinh vin.

Nhm sinh vin thc hin ti

N TT NGHIP Trang iii

Phn A : Gii thiu

B GIO DC V O TO CNG HO X HI CH NGHA VIT NAM

TRNG H S PHM K THUT TP.HCM C LP-T DO-HNH PHC

QUYT NH GIAO TI

H v tn sinh vin : V Phong Ph MSSV : 10117050

Minh Ton MSSV : 10117070

Ngnh : Cng ngh in t -Vin Thng

ti : LC THCH NGHI V NG DNG THC THI TRN KIT

TMS320C6713

1. C s ban u : ................................................................................................................................

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2. Ni dung cc phn thuyt minh v tnh ton: ................................................................................................................................

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3. Cc bn v : ................................................................................................................................

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4. Gio vin hng dn :

ThS. Ng Quc Cng

5. Ngy giao nhim v : . //2014.

6. Ngy hon thnh nhim v : ././2014.

Gio vin hng dn Ngy thng.nm 2014

Ch nhim b mn

N TT NGHIP Trang iv

Phn A : Gii thiu

NHN XT CA GIO VIN HNG DN . ......................................................................................................................................

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TP.HCM, Ngy thng .nm 2014

Gio vin hng dn.

N TT NGHIP Trang v

Phn A : Gii thiu

NHN XT CA GIO VIN PHN BIN .........................................................................................................................................

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Tp.HCM, Ngy.thng.nm 2014 TP.HCM, Ngy.thng.nm 2014

Gio vin phn bin 1 Gio vin phn bin 2

N TT NGHIP Trang vi

Phn A : Gii thiu

Abstract Echo and noise are common occurrence in today's telecommunication systems.

Noise problems in the environment have gained attention due to the tremendous

growth of technology that has led to noisy engines, heavy machinery, high speed wind

buffeting and other noise sources.

This acoustic echo is actually the noise which is created by the reflection of

sound waves by the wall of the room and the other things exist in the room.

This problem will cause the bad quality of voice signal and thus talkers could

not hear clearly the content of the conversation, even thought lost the important

information.

The problem of cancellation the noise and echo provides an echo free

environment for speakers during conversation .

In last few years various adaptive algorithms are developed for noise

cancellation.

In this thesis we present an implementation of LMS (Least Mean Square), and

RLS (Recursive Least Square) algorithms on MATLAB platform with the intention to

compare their performance in noise cancellation. We simulate the adaptive filter in

MATLAB with a noisy tone signal and white noise signal and analyze the performance

of algorithms in terms of MSE (Mean Squared Error), percentage noise removal,

computational complexity and stability.

In this project , the concept of echo cancellation system and and noise

cancellation system are studied, simulated and implemented in Matlab and TI

TMS320C6713 DSK.

The obtained results shows that RLS has the best performance but at the cost of

large computational complexity and memory requirement.

N TT NGHIP Trang vii

Phn A : Gii thiu

Li ni u Ngy nay x l tn hiu s ngy cng pht trin mnh m v ang lm thay i c

tnh cch mng trong rt nhiu lnh vc, t nhng lnh vc tng qut nht nh phn

tch tn hiu, lc s, lc thch nghi n vic p dng cc thut ton FFT, LMS, RLS

thit k, lp trnh to nn cc thit b phn cng ng dng trong cc lnh vc c th.

S dng cc thut ton thch nghi LMS, RLS trit nhiu, kh tp m tr

nn ph bin v c ng dng rng ri trong thc t nh vo s hot ng hiu qu

ca n m cc mch lc tng t trc y khng kh nng p ng.

Chnh v th chng minh kh nng hot ng hiu qu ca cc thut ton

thch nghi, nhm thc hin chn ti ny tm hiu l thuyt ca b lc s, b

lc thch nghi, cc thut ton thch nghi, m phng v ng gi cc thut ton thch

nghi bng MATLAB. Nhm thc hin cng tm hiu kh nng hot ng ca cc thut

ton thch nghi trong cc ng dng thc t trn mi trng KIT DSP TMS320C6713.

Ni dung n gm c 3 phn :

Phn A : Gii thiu

Phn B : Ni dung

o Chng 1: Tng quan v lc s.

o Chng 2: B lc thch nghi.

o Chng 3: ng dng lc thch nghi.

o Chng 4 : Gii thiu phn mm CCS v KIT TMS320C6713

o Chng 5 : Kh nhiu, trit echo trn KIT TMS320C6713.

o Chng 6 : Kt lun.

Phn C : Ph lc v ti liu tham kho.

N TT NGHIP Trang viii

Phn A : Gii thiu

MC LC

Trang

PHN A :GII THIU .................................................................................................... i

LI CM N ................................................................................................................. ii

QUYT NH GIAO TI ...................................................................................... iii

NHN XT CA GIO VIN HNG DN ........................................................... iv

NHN XT CA GIO VIN PHN BIN ............................................................... v

ABSTRACT ................................................................................................................... vi

LI NI U ............................................................................................................... vii

DANH MC T VIT TT ......................................................................................... ix

LIT K BNG ............................................................................................................. xi

LIT K HNH ............................................................................................................. xii

PHN B :NI DUNG ................................................................................................... 14

CHNG 1: TNG QUAN V LC S ................................................................... 15

1.1 M u ............................................................................................................. 15

1.2 Gii thiu v b lc s ..................................................................................... 17

CHNG 2: B LC THCH NGHI .......................................................................... 19

2.1 Mt s khi nim c bn. ................................................................................. 19

2.1.1 Bin ngu nhin. ........................................................................................... 19

2.1.2 Qu trnh ngu nhin. ................................................................................... 19

2.1.3 c tnh tng phn ca qu trnh ngu nhin ri rc theo thi gian. ........... 20

2.1.4 Tng quan ca cc tn hiu. ....................................................................... 21

2.2 Gii thiu v lc thch nghi. ............................................................................ 21

2.3 Cc cu trc lc thch nghi. ............................................................................. 22

2.3.1 Kh nhiu. .................................................................................................... 22

2.3.2 Nhn dng h thng. ..................................................................................... 23

2.3.3 B d on thch nghi. ................................................................................. 23

2.4 Cc thut ton lc thch nghi. .......................................................................... 24

2.4.1 Thut ton LMS. ........................................................................................... 24

2.4.2 Thut ton RLS. ........................................................................................... 27

CHNG 3 : NG DNG LC THCH NGHI ......................................................... 33

3.1 L thuyt kh nhiu thch nghi. ....................................................................... 33

N TT NGHIP Trang ix

Phn A : Gii thiu

3.1.1 Cc ch kh nhiu kiu thch nghi. ......................................................... 33

3.1.2 Cc thut ton cp nht cho cc b lc. ....................................................... 35

3.2 Cc thut ton thch nghi. ................................................................................ 36

3.3 Gii thiu Echo v trit echo dng thut ton thch nghi. ............................... 43

3.3.1 Cc loi ting vng. ...................................................................................... 44

3.3.2 Qu trnh trit ting vng. ............................................................................ 44

CHNG 4 : GII THIU PHN MM CCS V KIT TMS320C6713 .................. 49

4.1 Gii thiu v phn mm CCS (Code Composer Studio). ................................ 49

4.2 Gii thiu v kit TMS320C6713. .................................................................... 50

4.2.1 S khi v cc c trng ca kit TMS320C6713. .................................. 52

4.2.2 Hot ng c bn. ......................................................................................... 53

4.2.3 Bn nh. .................................................................................................. 53

4.3 Cc thnh phn ca kit TMS320C6713. .......................................................... 54

CHNG 5 : KH NHIU,TRIT ECHO TRN KIT TMS320C6713 .................... 59

5.1 Kh nhiu thch nghi bng thut ton LMS trn kit TMS320C6713. ............. 59

5.2 Kh nhiu thch nghi bng thut ton RLS trn kit TMS320C6713. .............. 62

5.3 Trit Echo dng thut ton LMS trn KIT TMS320C6713. ........................... 64

5.4 Trit echo s dng thut ton RLS trn kit TMS320C6713. ........................... 67

CHNG 6 :KT LUN ............................................................................................. 69

6.1 Kt qu t c. ................................................................................................ 69

6.2 Tn ti v hng pht trin ca ti. ................................................................ 69

6.2.1 Nhng mt cn tn ti : ................................................................................... 69

6.2.2 Hng pht trin. ............................................................................................. 70

PHN C :PH LC V TI LIU THAM KHO ................................................... 71

Ph lc A. ................................................................................................................... 72

1. Hng dn bin dch Simulink sang code C. ...................................................... 72

2. Hng dn ci t CCS V3.3 trn Windows XP. ............................................... 79

Ph lc B : Code Matlab. ........................................................................................... 82

Ti liu tham kho ...................................................................................................... 91

N TT NGHIP Trang x

Phn A : Gii thiu

DANH MC T VIT TT

AEC Acoustic Echo Canceller

AF Adaptive Filters

ANC Active Noise Canceller

CCS Code Composer Studio

CPLD Complex Programmable Logic Device

DSP Digital Signal Processing

EMIF Extrenal Memory InterFace

ERL Echo return loss

ERLE Echo Return Loss Enhancement

FIR Finite Impulse Response

IIR Infinite Impulse Response

LMS Least-Mean-Squared

MSE Mean-Squared Error

NLMS Normalized Least-Mean-Squared

RLS Recursive Least-Squares

N TT NGHIP Trang xi

Phn A : Gii thiu

LIT K BNG

Bng 3.1: Bng cc thng s thut ton LMS v RLS.42

Bng 3.2: Bng so snh thng s ERLE gia thut ton LMS v RLS...47

Bng 5.1: Bng thng k gi tr bin thu c khi thay i thng s variance..62

N TT NGHIP Trang xii

Phn A : Gii thiu

LIT K HNH

Hnh 1.1: Qu trnh hot ng ca mt b lc s...................................................... 15

Hnh 1.2: p ng xung, p ng bc v p ng tn s ca b lc ..................... 17

Hnh 2.1: Cu trc b lc thch nghi c bn.............................................................. 22

Hnh 2.2: Cu trc b lc thch nghi cho kh nhiu ................................................. 22

Hnh 2.3: Cu trc b lc thch nghi cho nhn dng h thng .................................. 23

Hnh 2.4: Cu trc cho b d on thch nghi ........................................................ 23

Hnh 2.5: ng biu din cht lng lm vic ca 1 h s .................................... 25

Hnh 2.6: Gin cp nht trng s .......................................................................... 28

Hnh 3.1: Cu trc kh nhiu thch nghi ................................................................... 33

Hnh 3.2: S thut ton LMS ............................................................................... 37

Hnh 3.3: Kh nhiu tch cc s dng thut ton LMS ............................................ 38

Hnh 3.4: S thut ton RLS ................................................................................ 40

Hnh 3.5: Kh nhiu tch cc s dng thut ton RLS ............................................. 41

Hnh 3.6: So snh thng s MSE gia LMS v RLS ................................................ 42

Hnh 3.7: C ch hnh thnh Echo ............................................................................ 43

Hnh 3.8: S to Echo trong DSP ......................................................................... 43

Hnh 3.9: Hot ng ca mt b trit ting vng ...................................................... 44

Hnh 3.10: S h thng trit ting vng ............................................................... 45

Hnh 3.11: S nguyn l s dng lc thch nghi trit echo .................................. 45

Hnh 3.12: Trit echo s dng thut ton LMS ......................................................... 46

Hnh 3.13: Trit echo s dng thut ton RLS .......................................................... 46

Hnh 3.14:Biu so snh ERLE gi thut ton RLS v LMS ............................... 48

Hnh 4.1: Lu pht trin phn mm to ra m i tng t ngn ng C ............. 50

Hnh 4.2: Board DSK 6713 ....................................................................................... 51

Hnh 4.3: Cc thnh phn i km vi DSK TMS320C6713 ..................................... 51

Hnh 4.4: S khi DSK C6713 ............................................................................. 52

Hnh 4.5: Bn nh v t chc b nh ca DSK C6713 ....................................... 54

Hnh 4.6: H thng DSP vi tn hiu v, ra tng t ................................................ 55

N TT NGHIP Trang xiii

Phn A : Gii thiu

Hnh 4.7: Giao tip ca Codec trn DSK .................................................................. 56

Hnh 4.8: S khi TLV320AIC23 codec ............................................................. 57

Hnh 5.1: M hnh kh nhiu thch nghi dng thut ton LMS ................................ 59

Hnh 5.2: M hnh chi tit khi Noise Channel ........................................................ 59

Hnh 5.3: M hnh kt ni kit TMS320C6713 h thng ANC .................................. 60

Hnh 5.4: Tn hiu ng vo h thng trit nhiu thch nghi dng thut ton LMS ... 60

Hnh 5.5: Dng sng tn hiu ng vo cng vi nhiu dng thut ton LMS ........... 61

Hnh 5.6: Dng sng tn hiu thu c sau khi trit nhiu dng thut ton LMS .... 61

Hnh 5.7: S h thng lc nhiu s dng thut ton RLS .................................... 62

Hnh 5.8: Dng sng tn hiu ng vo cng vi nhiu dng thut ton RLS ........... 63

Hnh 5.9: Dng sng tn hiu thu c sau khi trit nhiu dng thut ton RLS ..... 63

Hnh 5.10: M hnh kt ni kit TMS320C6713 h thng AEC ................................ 64

Hnh 5.11: H thng to ting vng .......................................................................... 64

Hnh 5.12: H thng trit ting vng dng thut ton LMS ..................................... 65

Hnh 5.13: Dng sng tn hiu ng vo h thng trit Echo dng thut ton LMS .. 65

Hnh 5.14: Dng sng tn hiu echo dng thut ton LMS ...................................... 66

Hnh 5.15: Dng sng tn hiu thu c sau khi trit Echo dng thut ton LMS ... 66

Hnh 5.16: S h thng trit echo s dng thut ton RLS ................................. 67

Hnh 5.17: Dng sng tn hiu Echo dng thut ton RLS ....................................... 67

Hnh 5.18: Dng sng tn hiu thu c sau khi trit echo dng thut ton RLS..... 68

N TT NGHIP Trang 14

Phn B : Ni dung

PHN B :

NI DUNG

N TT NGHIP Trang 15

Chng 1 : Tng quan v lc s.

CHNG 1:

TNG QUAN V LC S

1.1 M u

Lc s l qu trnh rt quan trng ca x l tn hiu s, v chnh nhng kh nng

phi thng ca cc b lc s lm cho chng tr nn rt ph bin nh ngy nay. Cc

b lc s gm c hai ng dng chnh : phn tch tn hiu v phc hi tn hiu. Phn tch

tn hiu c p dng khi tn hiu mong mun b giao thoa vi cc tn hiu khc hay b

cc loi nhiu tc ng vo n. Cn phc hi tn hiu l khi tn hiu m ta mong mun

hay cn nh gi, xt nghim b sai lch i bi nhiu yu t ca mi trung tc ng

vo; lm cho n b bin dng gy nh hng n kt qu nh gi.

C hai kiu lc chnh: Tng t v s. Chng khc nhau hon ton v cu to vt

l v cch lm vic. Mt b lc tng t s dng cc mch in tng t c to ra

t cc thit b nh l in tr, t in, hay opamp, C cc chun k thut tt tn

ti trong mt thi gian di cho vic thit k mt mch b lc tng t. Cn mt b lc

s th s dng mt b x l s hot ng tnh ton s ho trn cc gi tr c ly

mu ca tn hiu. B x l c th l mt my tnh mc ch chung nh mt PC, hay

mt chp DSP chuyn dng. Cc qu trnh hot ng ca mt b lc s c th hin

nh hnh 1.1 sau:

Hnh 1.1: Qu trnh hot ng ca mt b lc s.

Ni chung cc cng vic ca b lc s c th c thc hin bi b lc tng t(

Analog Filter). Cc b lc tng t c u im l gi thnh r, tc ng nhanh, di

N TT NGHIP Trang 16


ng( Dynamic Range) v bin v tn s u rng. Tuy nhin cc b lc s th c

cc cp thc hin hn hn cc b lc tng t, v d nh: cc b lc s thng thp

c th c li( Gain) 1+/-0.0002 t DC n 1000Hz v li s nh hn 0.0002

cc tn s trn 1001Hz. Tt c cc hot ng din ra ch trong khong 1Hz. iu ny

khng th thc hin c cc b lc tng t. V v vy cc b lc s s dn dn

thay th cho cc b lc tng t vi cc u im c th nh sau:

1) Mt b lc s th c kh nng lp trnh c, cn mt b lc tng t, mun

thay i cu trc th phi thit k li b lc.

2) Cc b lc s d dng thit k, d kim tra v d thi hnh trn mt my tnh mc

ch chung hay mt trm lm vic.

3) c im cc mch lc tng t l b nh hng bi s tri v ph thuc nhiu

vo nhit . Cc b lc s th khng c cc vn ny, v rt n nh vi c thi

gian v nhit .

4) Cc b lc s c th x l cc tn hiu tn s thp rt chnh xc. Tc ca

cng ngh DSP ngy cng tng ln, lm cho cc b lc s c kh nng x l cc tn

hiu tn s cao trong min m tn( Radio Frequency), m trong qu kh l lnh

vc c quyn ca cng ngh tng t.

5) Cc b lc s linh hot hn nhiu trong x l tn hiu, vi nhiu cch khc nhau

hay chnh l s x l thch nghi.

6) Cc b x l DSP nhanh c th x l cc t hp phc tp, phn cng tng i

n gin, v mt tch hp rt cao.

nng cao cht lng ca cc b lc tng t, ta ch trng khc phc hn ch

ca linh kin nh chnh xc, n nh, s ph thuc vo nhit v .v.v. Cn i

vi cc b lc s, vn d bn thn n c nhiu u im nn ta ch ch trng n cc

hn ch ca tn hiu v cc phng php thit k v thut ton chng trnh x l tn

hiu.

Trong chng ny, chng ta s tm hiu v mt s l thuyt c s v lc tn hiu,

lm tin cho vic thit k mt b lc s thch nghi.

N TT NGHIP Trang 17


1.2 Gii thiu v b lc s

Trong x l tn hiu s, ta thng ni tn hiu vo v ra ca mt b lc u

min thi gian, bi v tn hiu thng c to ra bng cch ly mu cc thi im

cch u nhau. Tuy nhin, ta cng c th ly mu cc v tr cch u nhau trong

khng gian hay trong mt s phm tr khc, nhng thng thng nht l ly mu trong

min thi gian v min tn s. Trong x l tn hiu s th t min thi gian ta c th

lin h tng qut n cc phm tr khc. V d hnh 1.2 sau s m t iu . Mi b

lc tuyn tnh u c mt p ng xung, mt p ng bc v mt p ng tn s. Mi

p ng ny u cha y thng tin v b lc, nhng di mi dng khc nhau.

Nu mt trong ba p ng c xc nh th hai p ng kia cng s c tnh ra trc

tip. C ba p ng ny u rt quan trng, v chng m t b lc cc hon cnh khc

nhau.

Vi p ng xung l u ra ca h thng khi u vo l xung n v, p ng

bc l u ra ca h thng khi u vo l bc nhy n v( hay xung bc thang). V

hm bc nhy l tch phn ca hm xung n v, nn p ng bc chnh l tch phn

ca p ng xung. T ta c hai cch tm p ng bc thang:

a mt s ng bc nhy vo b lc v xem kt qu u ra hay;

Ly tch phn ca p ng xung.

Cn p ng tn s ly t bin i Fourier ca p ng xung.

Hnh 1.2: p ng xung, p ng bc v p ng tn s ca b lc.

N TT NGHIP Trang 18


Phng php trc tip nht thc hin lc s l dng php tch chp ca tn hiu

vo vi p ng xung ca b lc s, khi p ng xung c xem l ct li cho vic

thit k ca b lc. Mt phng php khc thc hin lc s l dng phng php

quy. Khi b lc c thc hin bng php tch chp, mi mu trong tn hiu ra c

tnh ton bng cch t hp c trng s cc mu trong tn hiu vo. Cc b lc kiu

quy m rng thm qu trnh trn bng cch s dng c cc tr s tnh c t tn

hiu ra, bn cch cc im ly t tn hiu vo, thay v dng mt li lc, cc b lc

quy c xc nh bi mt dy h s quy. Cc b lc quy cn c gi l cc b

lc c p ng xung di v hn IIR, cn cc b lc thc hin theo phng php chp

th gi l cc b lc c p ng xung di hu hn FIR.

C nhiu cch con ngi biu din thng tin qua tn hiu nh trong cc kiu

iu ch hay m ha tn hiu: AM, FM, PCM,Cn cc tn hiu sinh ra trong t nhin

th ch c hai cch biu din l theo min thi gian hay l min tn s. Thng tin

c th hin trong min thi gian c m t bng ln ca s kin ti thi im

xut hin. Mi mu trong tn hiu cho thy ci g xut hin thi im y v ln

ca n. Tri li, thng tin c biu th trong min tn s c tnh cht gin tip hn v

mi mu tn hiu n c khng th th hin c thng tin y m phi trong mi

quan h nhiu im ca tn hiu.

T ta thy tm quan trng ca p ng bc v p ng tn s; p ng bc

m t s bin i ca thng tin trong min thi gian bi h thng cn p ng tn s

cho thy s bin i ca thng tin trong min tn s. Vi mi ng dng khc nhau th

tm quan trng ca hai loi p ng cng khc nhau.

N TT NGHIP Trang 19

Chng 2 : B lc thch nghi.

CHNG 2:

B LC THCH NGHI

Cc b lc thch nghi( Adaptive Filter) c s dng tt nht trong cc loi b

lc, cc tn hiu c iu kin hay cc thng s h thng thay i rt chm v b lc

c iu chnh b cho s thay i ny. Thut ton LMS l mt thut ton d

tm c s dng cung cp mt k hoch qun l tt vic iu chnh cc h s b

lc, ngoi ra cn c mt s thut ton khc cng c kh nng thch nghi nh: RLS,

NLMS,Mi thut ton c cc u, khuyt im khc nhau; chng ta s tm hiu r

iu qua cc phn sau y.

2.1 Mt s khi nim c bn.

2.1.1 Bin ngu nhin.

Khi ta thc hin mt th nghim ngu nhin, tp hp tt c cc kt qu( loi tr

nhau) c th xy ra gi l khng gian mu ca th nghim ngu nhin .

S kin l tp hp c th gm mt hay nhiu kt qu trong mt khng gian mu.

Nh vy bin ngu nhin l php nh x cc s kin sang cc gi tr thc ( hay

phc).

2.1.2 Qu trnh ngu nhin.

Qu trnh ngu nhin l tp hp cc hm s c cc thng s ( thng l thng s

thi gian), m c thuc tnh thng k no . Mt qu trnh ngu nhin c th c

biu din bi mt tp hp cc bin ngu nhin.

Mt qu trnh ngu nhin c gi l dng cht ( Strictly Stationary) nu cc

thuc tnh thng k ca n khng thay i khi dch chuyn i mt khong thi gian no

. Chng hn, i vi qu trnh ngu nhin ri rc theo thi gian c biu din bi

chui tn hiu theo thi gian u(n), u(n-1),, u(n-M+1) gi l dng cht khi hm mt

ng xc sut ( Joint Probability Density Function) ca n ti cc thi im quan

st n, n-1,, n-M+1 l khng i khi n thay i ( M khng i).

N TT NGHIP Trang 20


2.1.3 c tnh tng phn ca qu trnh ngu nhin ri rc theo thi gian.

Thc t cho thy kh c th xc nh hm mt ng xc sut ca tp hp cc

thi im quan st trong qu trnh ngu nhin. Do chng ta cn quan tm n cc

c tnh thng k tng phn ( Partial) ca n.

Xt mt qu trnh ngu nhin ri rc theo thi gian nh trn ta nh ngha k vng

v hm gi tr trung bnh ca bin ngu nhin trong qu trnh ngu nhin nh sau:

K vng ca i lng ngu nhin l trung bnh theo xc sut cc gi tr c th

nhn ca i lng ngu nhin , k hiu l E.

Cn hm gi tr trung bnh (n):

(n) = E[u(n)] (2.1)

Trong , E l ton t k vng thng k, v hm t tng quan ca qu trnh ngu

nhin c nh ngha:

r( n, n-k) = E[u(n)u*(n-k)]; k = 1, 2,, (2.2)

Trong , du * l k hiu ca lin hp phc.

Khi mt qu trnh ngu nhin l dng cht th lc ta c :

Hm gi tr trung bnh ca qu trnh ngu nhin lun lun bng hng s

, vi mi n.

Hm t tng quan ch cn ph thuc vo s khc nhau trong khong thi

gian quan st gia thi im n v n-k, chnh l k: r( n, n-k) = r(k).

Tuy nhin hai phng trnh trn khng m bo rng qu trnh ngu nhin

l dng cht. Nhng nu, hai phng trnh trn c m bo, ta ni rng

qu trnh ngu nhin ri rc theo thi gian l dng theo ngha rng.

N TT NGHIP Trang 21


2.1.4 Tng quan ca cc tn hiu.

Trong vic x l tn hiu, chng ta lun cn phi so snh cc tn hiu vi nhau;

Mt phng php so snh hay dng nht l tng quan( Correlation) s c m

t sau y:

nh ngha tng quan cho( Cross_Correlation):

Gi s c hai dy x(n) v y(n), ti thiu mt trong hai dy c nng lng hu hn.

Tng quan cho ca x(n) v y(n) c nh ngha nh sau:

rxy(n) =

m

nnmymx ,...,1,0)()( (2.3)

nh ngha t tng quan( Auto_Correlation):

Trong nh ngha tng quan cho nu ta c x(n) y(n) th ta c nh ngha t

tng quan. Vy hm t tng quan c nh ngha nh sau:

rxx(n) =

m

nnmxmx ,...,1,0)()( (2.4)

rxx(n) l hm t tng quan ca dy x(n).

2.2 Gii thiu v lc thch nghi.

Trong cc b lc s quy c( FIR v IIR), cc thng s ca qu trnh lc dng

xc nh cc c trng ca h thng coi nh bit, cc thng s ny c th bin i

theo thi gian, nhng bn cht ca s bin i th coi nh bit. Trong nhiu bi ton

thc tin, mt s thng s c th c bt nh ln do d liu th nghim trc v qu

trnh khng c thch hp. Mt s thng s c th bin thin theo thi gian nhng bn

cht chnh xc ca s bin thin th khng th tin on c. Trong cc trng hp

, chng ta cn phi thit k b lc c kh nng t nm bt, c th thch nghi vi

hon cnh hin thi.

Cc h s (Coefficient) ca mt b lc thch nghi c hiu chnh b li cc thay

i trong cc tn hiu vo, tn hiu ra hoc trong cc thng s ca h thng. Thay v b

cng nhc, mt h thng thch nghi c th nm bt cc c trng ca tn hiu v d

N TT NGHIP Trang 22


d

x

e

y B lc

thch nghi

+

-

theo cc bin i chm. Mt b lc thch nghi c th rt hu ch cho s bt nh v cc

c trng ca mt tn hiu hoc khi cc c trng thay i. Hnh 2.1 sau th hin

mt cu trc c bn ca b lc thch nghi.

Hnh 2.1: Cu trc b lc thch nghi c bn.

Trong ng ra y ca b lc thch nghi c so snh vi tn hiu mong mun

(Desire) d cho ra tn hiu sai s ( Error ) e, tn hiu sai s ny c hi tip v

iu chnh b lc thch nghi.

Cc h s ca b lc thch nghi c iu chnh, hay ti u h a, s dng cc thut

ton thch nghi nh LMS, RLS da trn tn hiu sai s e. phn cc thut ton ca b

lc thch nghi chng ta s ni r v thut ton ny.

2.3 Cc cu trc lc thch nghi.

Mt s cc cu trc thch nghi c s dng cho cc ng dng khc nhau trong

lc thch nghi. Mi ng dng c mt cu trc thch nghi c th tng ng. Sau y

chng ta ch xt ba trng hp c th l: th nht, cu trc thch nghi cho kh

nhiu( Noise Cancellation); th hai, cho h thng nh v( System Identification) v

th ba, cho cc b tin on( Predictor) thch nghi.

2.3.1 Kh nhiu.

Hnh 2.2 sau y th hin cho cu trc ng dng kh nhiu.

d + n +

e y y

n e

Hnh 2.2: Cu trc b lc thch nghi cho kh nhiu.

B lc thch nghi

N TT NGHIP Trang 23


y

x d e

+

-

Tn hiu mong mun d, b sa i bi nhiu cng n, khng tng quan. Nhiu

n c th n t vi ngun ging nh n nhng b thay i bi iu kin mi trng.

Ng ra y c thch ng vi nhiu n, khi iu ny xy ra, tn hiu sai s e tin n gn

tn hiu mong mun d, ton b ng ra l tn hiu sai s e ny.

2.3.2 Nhn dng h thng.

Hnh 2.3 sau y th hin mt cu trc thch nghi c dng cho ng dng nhn

dng hay m hnh mu. Cng mt tn hiu vo, c a n hai h thng song song l

h thng cha xc nh v b lc thch nghi. Tn hiu sai s e l s khc nhau gia p

ng ca h thng cha bit d v p ng ca b lc thch nghi y. Tn hiu sai s ny

c phn hi v b lc thch nghi v c dng cp nht( Update) cc h s cho

b lc cho n khi ton b ng ra y = d. Khi iu ny xy ra, hot ng x l thch

nghi c kt thc, v e tin gn n 0. Trong s kt hp ny, b lc thch nghi lm

mu cho h thng cha xc nh.

Hnh 2.3: Cu trc b lc thch nghi cho nhn dng h thng.

2.3.3 B d on thch nghi.

Hnh 2.4 sau y s minh ha cho cu trc ca mt b d on thch nghi, m c th

cung cp mt s c lng ca u vo.

u vo IN1 = d(n) e(n)

y(n)

IN2 y(n)

Hnh 2.4: Cu trc cho b d on thch nghi.

B lc thch nghi

H thng cha bit

B lc

thch nghi

Khi tr

N TT NGHIP Trang 24


2.4 Cc thut ton lc thch nghi.

2.4.1 Thut ton LMS.

Thut ton LMS, thng c gi l mt thut ton Stochastic Gradient; n

thng c s dng cho cc b lc thch nghi, bi v cc l do sau y:

N l c bn u tin.

N rt n gin.

Trong thc t n lm vic rt tt.

N yu cu t php ton.

N cp nht cc h s rt n gin, nn n thch nghi lin tc cho b lc.

N nh du s thay i chm trong thng tin tn hiu s rt tt.

Thut ton ny i km vi mt b lc FIR hiu chnh c. Cc h s hay trng

s ca b lc FIR thch nghi c th hiu chnh da trn mt mi trng thay i nh

mt tn hiu vo. Cng c th s dng b lc IIR thch nghi, nhng cc im cc ca

mt b lc IIR trong qu trnh thch nghi c th cp nht n cc gi tr nm ngoi

vng trn n v, lm cho b lc khng n nh.

Tn hiu vo b lm tr ca b lc tuyn tnh kt hp c o v cng li cho

tn hiu ra y(n):

y(n) =

1

0

)(),(N

k

knxknw (2.5)

Phng trnh ny c vit li di dng vector l:

y(n) = W(n)XT(n) = X(n)W

T(n) (2.6)

Trong :

W(n) = [w(0,n) w(1,n) w(N,n)] (2.7)

X(n) = [x(0,n) x(1,n) x(N,n)] (2.8)

S m T biu th cho ma trn chuyn v.

S o cht lng lm vic ca mt b lc l da trn tn hiu sai s:

e(n) = d(n) y(n) (2.9)

N TT NGHIP Trang 25


Cc h s ca b lc c hiu chnh sao cho ti thiu ha mt hm sai s trung

bnh bnh phng. l hm E[e2(n)], vi E biu th l gi tr k vng hay l ton t

k vng thng k:

E[e2(n)] = E[d

2(n)]- 2E[d(n)y(n)] + E[y

2(n)] (2.10)

Nu ta xt khi ch c mt h s th phng trnh(2.27) tr thnh:

E[e2(n)] = E[d

2(n)]- 2E[d(n)x(n)]w(0) + E[x

2(n)]w

2(0) (2.11)

Nu d(n) v x(n) hon ton c lp vi nhau, ta c:

E[d(n)x(n)] = E[d(n)]E[x(n)] (2.12)

Nu cc tn hiu d v x hon ton khng i theo thi gian, cc gi tr mong i

ca tch ca chng cng s khng i theo thi gian. Trong trng hp , phng

trnh(2.13) c vit li l:

E[e2(n)] = A - 2 w(0) + Cw

2(0) (2.13)

Vi A = E[d2(n)]; = E[d(n)y(n)]; C = E[x2(n)] = E[x(n)]E[x(n)]

=E[y(n)/w(0)]E[x(n)]

w(0) = E[y(n)]E[x(n)]/C = E[y(n)x(n)]/C = E[y(n)d(n)]/C = /C; do , s o cht

lng lm vic cho mt h s l:

w(0) = /C (2.14)

m n biu th gi tr ti E[e2(n)] l cc tiu. biu din kt qu trn ta th hin

hnh v(2.11) sau y.

E[e2(n)]

min

0 /C w(0)

Hnh 2.5: ng biu din cht lng lm vic ca 1 h s.

H s c cp nht theo cch sau:

w(0,n+1) = w(0,n) - )0(dw

d E[e

2(n)] (2.15)

N TT NGHIP Trang 26


y, l mt hng s xc nh tc hi t. Du tr trong phng trnh(2.15)

gn lin vi chiu ca bc. T hnh 2.5 ta thy nu gi tr hin ti ca h s bn tri

ca tr cc tiu /C, bc phi l dng( tng ln). Mt khc, nu gi tr hin ti ca

h s bn phi ca tr cc tiu /C, bc phi l m( gim xung).

Trng hp ny s xc nh vng c dc dng ca hm cht lng. Nh vy,

chiu ca bc t l vi phn m ca dc.

Ngi ta thng dng phng trnh sau y i din cho thut ton LMS:

W(n+1) = W(n) + 2 e(n)X(n) (2.16)

Phng trnh (2.16) cho ta mt phng tin n gin nhng mnh m v hiu qu

cp nht cc h s, khng cn ly trung bnh hoc vi phn v s c dng thc

hin cc b lc FIR thch nghi. Phng trnh ny thng c vit li vi = 2

trong cc chng trnh, tc l:

wk(n+1) = wk(n) + e(n)x(n-k) (2.17)

Thut ton LMS rt ph hp cho mt s ng dng, gm kh tp m v kh di

vang thch nghi, tin on v cn bng.

Cc bin th khc ca thut ton LMS c s dng, nh: LMS du sai s,

LMS du d liu, v LMS du du.

1) Trong thut ton LMS du sai s, th phng trnh (2.17) tr thnh:

wk(n+1) = wk(n) + sgn[e(n)]x(n-k) (2.18)

Vi sgn l hm du c nh ngha nh sau:

[e(n)] =

0)(,1

0)(,1

nekhi

nekhi (2.19)

2) Trong thut ton LMS du d liu, phng trnh (2.17), tr thnh:

wk(n+1) = wk(n) + e(n)sgn[x(n-k)] (2.20)

3) Trong thut ton LMS du du, phng trnh (2.17), tr thnh:

wk(n+1) = wk(n) + sgn[e(n)]sgn[x(n-k)] (2.21)

V c khai trin ra nh sau:

N TT NGHIP Trang 27


wk(n+1) =

khckhinw

knxnekhinw

k

k

,)(

)](sgn[)](sgn[,)(

(2.22)

Thut ton LMS c hon thnh kh hu dng trong cc b cn bng thch

nghi, kh tp m trong in thoi, .v.v.Cc phng thc khc, nh l thut ton RLS s

c trnh by phn sau. Thut ton ny c th t ra c hi t nhanh hn thut

ton LMS c bn, nhng phi tr gi cho s tnh ton nhiu hn. RLS da trn vic bt

u vi gii php ti u v sau khi dng mi mu vo cp nht p ng xung nhm

duy tr qu trnh ti u h a. S bc cn thit v trc tip c nh ngha qua mi

mu thi gian.

Cc thut ton tr nn hu dng khi khng c tn hiu tham chiu thch hp. B

lc c thch ng trong mt ci cch nh phc hi vi c tnh ca tn hiu b

mt t trc khi n b lc. Thay v ly dng sng yu cu lm mu, nh trong cc

thut ton LMS hay RLS, c tnh ny c dng trong qu trnh thch nghi ca b lc.

Khi c c tn hiu yu cu, quy c tin gn nh LMS c th c s dng, cn nu

khng th dng kin thc bit trc v tn hiu.

2.4.2 Thut ton RLS.

Thut ton Recusive Least-Squares( RLS) c xem nh trng hp c bit ca

b lc Kalman. Thut ton RLS l mt cng c quan trng cho vic xc nh cc h

s ca b lc thch nghi tuyn tnh. Thut ton RLS tng phc tp, s lng cc

php ton, v tin cy. Do , RLS a ra hi t nhanh hn v li t hn, nhng

i li yu cu ph tn cho nhiu s tnh ton hn.

Khi thut ton LMS tm li ti thiu h a, n ch ngh n gi tr li hin ti,

cn trong thut ton RLS, mi li c xem l li ton cc t lc bt u n im

d liu hin thi. Thut ton RLS da trn vic bt u vi gii php ti u v sau khi

dng mi mu vo cp nht p ng xung nhm duy tr qu trnh ti u h a. S

bc cn thit v trc tip c nh ngha qua mi mu thi gian. iu ny c ngha

l thut ton RLS s dng nhng thng tin t tt c cc mu u vo qu kh c

lng ma trn t tng quan ca vector d liu u vo. gim nh hng

N TT NGHIP Trang 28


ca cc mu u vo t qu kh cch xa, ta s dng yu t trng s nh gi s nh

hng ca mi mu.

Trng s ny c th hin trong hm chi ph sau y:

2

1

( ) ( , ). | ( ) |n

i

n n i e i

(2.23)

Trong , e(i) l s khc bit gia tn hiu mong mun d(i) so vi tn hiu ng ra

y(i), c to thnh t tp tn hiu ng vo (ti thi im i) u(i),u(i-1), u(i-M+1)

e(i) = d(i) y(i) = d(i) wH(n)u(i) , 1 i n (2.24)

u(i) l tp vector ng vo ca tn hiu ti thi im i,

u(i) = [u(i),u(i-1),,u(i-M+1)]T. (2.25)

w(n) l tp vector trng s ti thi im n, xc nh bi

w(n) = [w0(n),w1(n),, wM-1(n)]T

. (2.26)

Gin cp nht trng s:

u(i) u(i-1) . u(i-M+2) u(i-M+1)

.

y(i)

Hnh 2.6: Gin cp nht trng s

H s trng s ( n,i ) c gi tr 0 < ( n,i ) 1 , i=1,2, n

Mt hnh thc c bit ca vector trng s thng c s dng l trng s m

( , )n in i

i=1,2n (2.27)

V vy hm chi ph c biu din li nh sau:

Z-1

W0*(n)

W1*(n)

Z-1

W(M-2)*(n) W(M-

N TT NGHIP Trang 29


2

1

( ) . | ( ) |n

n i

i

n e i

(2.28)

Ma trn t tng quan ( )n c biu din : 1

( ) . ( ). ( )n

n i H

i

n u i u i

(2.29)

Vector tng quan cho Z(n) gia tp tn hiu u vo v tn hiu ng ra mong mun

tng ng c biu din l :

*

1

( ) . ( ). ( )n

n i

i

z n u i d i

(2.30)

Cc bc th c hi n thut ton RLS: Khi to thng s thut ton RLS:

ng dng thut ton RLS ta phi khi to vng lp qui bng cch chn

gi tr bt u P(0) sao cho khng c im k d trn ma trn tng quan ( n). Ta c

th lm c iu ny bng cch ly nghch o ca n.

0

01 1( ) [ . ( ). ( )]i H

i n

n u i u i

(2.31)

Vi vector u(i) c c t mt khi ban u ca d liu t -n0 i 0

Ma trn tng quan c vit l:

1

( ) . ( ). ( ) . .n

n i H n

i

n u i u i I

(2.32)

Vi I l mt ma trn n v mxm , hng s v tr nh.

Vi n = 0, ta c (0) = I

Gi tr khi to P(n) chnh l nghch o ca ma trn tng quan, ta c:

P(0) =-1 I. .

Trong thi gian khi to, hm u(n) c vit

1/2( 1)/2. , 1( )

0, 0, 1

M n Mu n

n n M

(2.33)

Gi tr khi to ca vector trng s c thit lp W^(0) = 0

Vic tnh ton cc tiu hm chi ph :

N TT NGHIP Trang 30


2 2

w( )

1

( ) min . . || ( ) || . | ( ) |n

n n i

n

i

n w n e i

(2.34)

Mi trng thi gian thi tc th c cp nht, n = 1,2,...

1

1

. ( 1). ( )( )

1 . ( ). ( 1). ( )HP n u n

k nu n P n u n

(2.35)

^( ) ( ) w ( 1). ( )Hn d n n u n (2.36)

^ ^ *w ( ) w ( 1) ( ). ( )n n k n n (2.37)

1 1( ) . ( 1) . ( ). ( ). ( 1)HP n P n k n u n P n (2.38)

b) Cp nht qui cho tng trng s li:

Gi tr nh nht ca tng trng s li, min ( )n ,c tnh :

^

min ( ) ( ) ( ).w ( )H

dn n z n n . (2.39)

Trong , ( )d n c tnh

2 2

1

( ) . | ( ) | . ( 1) | ( ) |n

n i

d d

i

n d i n d n

(2.40)

^ * ^ *min ( ) [ (n-1)-z (n-1).w (n-1)]+d(n).[d (n)-u (n).w (n-1)]-z (n).k(n). (n)H H H

dn (2.41)

Dng vector li k(n) th hin :

1 1 ^( ). ( ) ( ). ( ). ( ) [ (n).z(n)] . ( ) w ( ). ( )H H H Hz n k n z n n u n u n n u n

Ta rt gn li c :

* ^ *

min min

* ^

min

*

min

( ) ( 1) ( ). ( ) w ( ). ( ). ( )

( 1) ( ).[d(n)-w (n).u(n)]

. ( 1) ( ). ( )

H

H

n n d n n n u n n

n n

n n e n

(2.42)

Vi e(n) l li d on tip theo.

V y l nhng gi tr thc , ta c : * *( ). ( ) ( ). ( )n e n e n n

N TT NGHIP Trang 31


H s chuyn i:

Ta c:

^ *

^

( ) ( ) [w (n-1)+k(n). (n)] . ( )

( ) w ( 1). ( ) ( ). ( ). ( )

(1 ( ). ( )). ( )

H

H H

H

e n d n u n

d n n u n k n u n n

k n u n n

H s chuyn i : ( )

( ) 1 ( ). ( )( )

He nn k n u nn

(2.43)

H s chuyn i ( )n c xc i nh duy nht bi vector li k(n) v vector d

liu vo

Bng cp nht :

2 2

1( ) [ ].u(n)

( 1) | ( ) |k n

n u n

2 2

^*

^ ^ *

^ ^ 2

( ) ( ) w ( 1). ( )

w ( ) w ( 1) ( ). ( )

( ) . ( 1) | ( ) |

n d n n u n

n n k n n

n n u n

Vi 2^ ( )n l d on ca bin li ,

2^ 1( ) ( )n P n

c. Phn tch s hi t ca thut ton RLS:

Vi (0) 0, (0) 0.u

Thut ton RLS tnh ton chnh xc bng phng php Least Squares cho n M.

Khi =1 , ta c th vit ^ 1w ( ) ( ). ( )n n z n , n M

1

( ) ( ). ( )n

H

i

n u i u i

*

1

( ) ( ). ( )n

i

z n u i d i

, e0 li php o. W0 l vector tham s hi quy.

*

0 0

1

( ) ( ).w ( ). ( )n

i

z n n u i e i

^ 1 *

0 0

1

w ( ) w ( ). ( ). ( )n

i

n n u i e i

Ly k vng w^(n) :

N TT NGHIP Trang 32


(2.44)

Ta thy :

+ Ma trn tng quan ( )n c xc nh duy nht bi trnh t ca cc vector ng vo

u(1),u(2),u(n).

+ Li o lng e0(i) c lp vi vector ng vo u(i).

+Li o lng e(i) c gi tr 0.

V vy , ta vit c : E[w^(n)]=w0 , n M.

Nhn xt : S hi t ca thut ton RLS c ngha khi n M. khng ging LMS ,s hi

t ca RLS t c m khng cn n .

^ 1 *

0 0

1

1 *

0 0

1

[w (n)]=w [ (n). ( ). ( )]

=w [ { (n). ( ). ( ) | ( ), 1,2,....., }]

n

i

n

i

E E u i e i

E E u i e i u i i n

N TT NGHIP Trang 33

Chng 3 : ng dng b lc thch nghi.

CHNG 3 :

NG DNG B LC THCH NGHI

Chng ny tip cn cc tng c bn thit k mt b lc thch nghi cho ng

dng kh nhiu, trit ting vng da trn cc l thuyt c gii thiu cc chng

trc.

Kh nhiu v trit tin vng da trn vic tr nhiu t tn hiu nhn c, mt

hot ng c iu khin theo kiu thch nghi nhm mc ch ci tin hot ng( tng

t s tn hiu trn nhiu) ca h thng. Khi s hot ng ca h thng c iu khin

bi mt qu trnh x l thch nghi, n c th t c mt hot ng h thng cao vt

tri hn so vi kh nhiu khng thch nghi.

3.1 L thuyt kh nhiu thch nghi.

3.1.1 Cc ch kh nhiu kiu thch nghi.

V c bn, mt b kh nhiu thch nghi c mt cp ng vo, cc h thng iu

khin thch nghi lp khp kn. Ton b cu trc ca h thng c xc nh nh hnh

3.1 sau y.

Hnh 3.1: Cu trc kh nhiu thch nghi.

Trong thc t, hai ng vo ca h thng c xut pht t mt i cm bin: mt

b cm bin chnh v mt b cm bin tham kho. B cm bin chnh nhn mt tn

hiu mang thng tin s(n) b thay i bi nhiu cng v0(n). Tn hiu s(n) v nhiu

N TT NGHIP Trang 34


cng l khng tng quan vi nhau. B cm bin tham kho nhn mt nhiu v1(n) m

khng tng quan vi tn hiu s(n) nhng tng quan vi nhiu v0(n) ng vo b

cm bin chnh, theo mt chiu hng cha xc nh:

E[s(n)v1(n-k)] = 0 ; vi mi k (3.1)

E[v0(n)v1(n-k)] = p(k) (3.2)

y, trc khi cc tn hiu nhn gi tr thc v p(k) l mt php tng quan

cho cha bit cho tr k.

Tn hiu tham kho v1(n) c x l bng mt b lc thch nghi cung cp tn

hiu ng ra y(n). Ng ra b lc c tr cho tn hiu chnh d(n), l p ng mong

mun ca b lc thch nghi. Tn hiu li c nh ngha nh sau:

e(n) = d(n) y(n) (3.3)

Tn hiu li quay vng c s dng iu chnh a ra cc h s ca b lc

thch nghi, v vng lp iu khin thc hin lc v php tr c khp kn. Ch rng

s(n) tht ra l mt phn ca tn hiu li e(n). By gi, b lc thch nghi c gng ti

thiu ha gi tr trung bnh bnh phng ca tn hiu li e(n). Tn hiu mang thng tin

s(n), v bn cht khng b thay i bi b kh nhiu thch nghi. K t y, ti thiu

ha gi tr trung bnh bnh phng ca e(n) l tng ng vi vic ti thiu ha gi tr

nhiu ra v0(n) y(n). Vi s(n) cn li, v bn cht khng thay i, n theo sau vic ti

thiu ha gi tr trung bnh bnh phng ca tn hiu li, thc ra l tng t khi ti a

ha hot ng ca h thng( t s tn hiu trn nhiu) ca h thng.

Hiu qu s dng kh nhiu thch nghi, ph thuc b cm bin tham kho c

t trong trng nhiu ca b cm bin chnh vi hai mc tiu c trng lin quan:

1) Thnh phn s(n) ca ng ra b cm bin chnh l khng th nhn ra ng ra b

cm bin tham kho.

2) Ng ra b cm bin tham kho l tng quan rt cao vi thnh phn nhiu ca

ng ra b cm bin chnh. Ngoi ra, s thch nghi ca cc h s b lc c th c iu

chnh phi l iu kin thun li gn nht.

N TT NGHIP Trang 35


3.1.2 Cc thut ton cp nht cho cc b lc.

T iu kin cc b lc lm mu cc thi im khc nhau, cc b lc phi khc

nhau cc thi im khc nhau, v vy cc b lc phi thch nghi. Trong thc t cho

mc ch ny, c nhiu thut ton c a ra nh ta gii thiu chng trc c

th hot ng rt tt cho s thch nghi ca cc b lc. Thc t trong iu kin kh

nhiu th thut ton LMS c s dng u tin. L do cho iu ny l cc th tc tnh

ton ca chng l tng i nh v d dng thc hin trong cc kiu khc nhau ca

vic thc hin cc ng dng.

Cc nhn t quan trng ca cc thut ton:

+ Tc hi t: lin quan n cch thc m cc thut ton dng chuyn i

nhanh cc thng s b lc nhm ti u h a cc gi tr ca chng.

+ Cc th tc tnh ton: s cc hot ng tnh ton cn cp nht mi thng s

b lc.

+ Li iu chnh: lin quan n c bao nhiu sai khc t gi tr ti u ca chng.

+ nh du: lin quan n cch thc m cc thut ton s ko theo s khc nhau

ca cc gi tr thng s.

+ thit thc: lin quan n hot ng thut ton cp nht cc thng s khng

b gi to bi s nh hng nh nh l nhiu.

+ n nh: Mt thut ton c cho l n nh nu sai s bnh phng trung

bnh hi t n gi tr cui cng.

+ Cc thuc tnh s ha: cc thut ton nn n nh trong qu trnh s ha c

ngha l t li lng t ha. Cc li lng t ha ny xy ra khi cc thut ton

c thc hin trn cc DSP, m lun lun c di t hu hn.

Trong thc t, cc thut ton c cp nht tc ly mu v hot ng tnh

ton nhanh. N khng th thc hin c cc thut ton m l chm cho cc

h thng thi gian thc. Nhn t khc m nh hng hon ton rt mnh l cc

c tnh phn cng, c thc hin cho vic thc hin cc h thng thi gian

thc.

N TT NGHIP Trang 36


3.2 Cc thut ton thch nghi.

Phn ny ta s nhc s lc li hai thut ton LMS v RLS thng c s dng

trong thut ton kh nhiu thch nghi.

Nhim v ca thut ton thch nghi l cp nht cc h s b lc bng vic ti

thiu ha li trung bnh bnh phng. Cc thut ton thch nghi c th b tch ra cc

kiu ring m da trn tiu chun chng c c s dng cp nht cc h s b lc

c thch nghi khng.

Thc hin gii thut LMS .

Bc 1 : Tnh ng ra ca b lc.

1

0

( ) w( ). ( ) w ( ). ( )N

T

i

y n n x n i n x n

Bc 2 : c lng sai s ,

e(n) = d(n) y(n)

Bc 3 : Cp nht trng s nhnh ca b lc ,

w(n+1) = w(n) + x(n)e(n).

N TT NGHIP Trang 37


Lu thut ton LMS

Sai

ng

Hnh 3.2: S thut ton LMS

Bt u

c tham s , iterations,

khi w(0),x(0)

n =1

c tn hiu ng vo tn

hiu x(n) v tn hiu d(n)

Tnh ton ng ra b lc y(n)

c lng sai s e(n)

Cp nht trng s nhnh

n =

iteration

Kt thc

N TT NGHIP Trang 38


Hnh 3.3 m t cc kt qu thu c bng cch p dng cc thut ton LMS lc

nhiu c cha cc tn hiu u vo s (n), tn hiu mong mun: d (n) = s (n) + n2 (n) v

tn hiu li, Tham s kch thc bc c chn l 0,0002 v b lc thch nghi c

chiu di l 5. Ta c th c nhn thy trong mu xanh da tri tn hiu ng vo s(n),

tn hiu u vo. Mu xanh l cy l tn hiu u vo cng vi nhiu v mu l tn

hiu li , tn hiu sau khi qua b lc e(n).

L=5; = 0.0002

Hnh 3.3 Kh nhiu tch cc s dng thut ton LMS

Phn tch hnh trn, Ta c th c nhn thy rng cc thut ton LMS hiu sut b lc

khng tt, c tn hiu li ng ra e (n) c s khc bit so vi tn hiu ban u s (n),

9900 9910 9920 9930 9940 9950 9960 9970 9980 9990 10000-3

-2

-1

0

1

2

3

4

Iterations

Bie

n d

o

Khu nhieu tich cuc su dung thuat toan LMS

Tin hieu ngo vao s(n)

Tin hieu + nhieu d(n)

Tin hieu ngo ra e(n)

N TT NGHIP Trang 39


Thc hin gii thut RLS.

Bc 1 : Tnh vector li k(n).

1

1

. ( 1). ( )( )

1 . ( ). ( 1). ( )HP n u n

k nu n P n u n

Bc 2 : Tnh ng ra ca cc b lc s dng cc trng s nhnh trc

v vector ng vo hin ti.

( ) w( 1). ( )y n n u n

Bc 3 : c lng sai s (error estimation)

( ) ( ) ( )e n d n y n

Bc 4 : Cp nht vector trng s nhnh w(n).

w( ) w( 1) ( ). ( )Hn n k n e n

Bc 5 : Cp nht Gi tr khi to P(n) chnh l nghch o ca ma trn

tng quan, ta c:

.

1 1( ) . ( 1) . ( ). ( ). ( 1)HP n P n k n u n P n

N TT NGHIP Trang 40


Lu thut ton RLS

ng

Sai

ng

Hnh 3.4: S thut ton RLS

Hnh 3.5 m t cc kt qu ca vic p dng cc thut ton RLS trong vic loi b

ting n. C th ni rng thut ton c hiu sut tt trong khi lm vic nh mt ANC.

ng mu xanh da tri i din cho tn hiu ban u vo s (n), ng mu xanh l

Bt u

c tham s iterations,

khi w(0),x(0),k(0),

n =1

c tn hiu ng vo tn

hiu x(n) v tn hiu d(n)

Tnh vector trung gian

Tnh vector li

Tnh ng ra b lc

c lng sai s

Cp nht trng s nhnh

Tnh ma trn nghch o

n =

iteration

Kt thc

n =n+1

N TT NGHIP Trang 41


cy tng trng cho tn hiu cng vi nhiu d (n) = s (n) + n2(n) v dng mu i

din cho tn hiu li e(n), n gn vi tn hiu gc u vo s (n).

L=5 ; =1;

Hnh 3.5: Kh nhiu tch cc s dng thut ton RLS

Thut ton RLS l mt cng c quan trng cho vic xc nh cc h s ca b

lc thch nghi tuyn tnh. Thut ton RLS tng phc tp, s lng cc php ton, v

tin cy. Do , RLS a ra hi t nhanh hn v li t hn, loi b nhiu tt hn.

9900 9910 9920 9930 9940 9950 9960 9970 9980 9990 10000-4

-3

-2

-1

0

1

2

3

Iterations

Bie

n do

Khu nhieu tich cuc su dung thuat toan RLS

Tin hieu ngo vao s(n)

Tin hieu + nhieu d(n)

Tin hieu ngo ra e(n)

N TT NGHIP Trang 42


Bng 3.1 : Bng cc thng s thut ton LMS v RLS

Thng s MSE (mean-squared error) hay cn gi l hm chc nng J(n ) nh gi

chnh lch tn hiu ngun so vi tn hiu error. Thut ton hi t khi MSE n nh.

- LMS

2(n) [s(n) e(n)]J (3.4 )

- RLS

2(n) [s(n) e(n)]J (3.5)

Hnh 3.6: So snh thng s MSE gia LM v RLS

RLS c tc hi t nhanh hn rt nhiu so vi LMS. RLS hi t vi khong 2000

ln lp. LMS hi t vi khong 20000 ln lp.

Thut ton

Cng sut

tn hiu ng

vo Px

Cng sut

nhiu.

Pn

Cng sut tn

hiu ng ra

Pe

Mean

MSE

LMS 0.5 0.2493 0.5032 0.0439

RLS 0.5 0.2486 0.5003 0.0016

N TT NGHIP Trang 43


3.3 Gii thiu Echo v trit echo dng thut ton thch nghi.

Echo l mt s phn x m thanh n ngi nghe trong mt khong thi gian sau

m thanh gc. Ni chung, echo c mt khong delay tng i di.

V vy m trong hiu ng echo, m thanh thc v m thanh to ra c tch bit r

rng, con ngi c th nhn bit s khc bit. C ch ca echo c th c biu din

di y.

Hnh 3.7: C ch hnh thnh ECho

Theo hnh trn th tn hiu i t ngun n ngi nghe theo hai hng. Hng

u tin th tn hiu i trc tip t ngun n ngi nghe. Hng th hai th tn hiu i

n tng v b phn x ngi nghe. Qu trnh th hai din ra trong thi gian lu

hn so vi qu trnh u, v vy ngi nghe s nghe hai m thanh trong khong thi

gian khc nhau. Cng sut tn hiu ca qu trnh th hai s b suy hao do qu trnh

phn x.

Hnh 3.8: S to Echo trong DSP

N TT NGHIP Trang 44


3.3.1 Cc loi ting vng.

C 2 loi ting vng trong mng vin thng: ting vng in t (ting vng lai) v

ting vng m.

Ting vng in t l do s mt phi hp tr khng ti cc im khc nhau dc theo

knh truyn. Ting vng lai c tao ra cc kt ni lai m thu bao 2 dy c kt

ni n chuyn mch in thoi 4 dy trong cc h thng vin thng.

Ting vng m hc l do s phn x cc sng m thanh v khp ni m hc gia

speaker v microphone trong cc in thoi hands-free, in thoi di ng v cc h

thng vin thng.

3.3.2 Qu trnh trit ting vng.

C 2 gii pht gii quyt vn ny, gim Echo (Echo Suppression) v kh

Echo (Echo Cancellation). Lun vn ny ch tp trung vo vn trit ting vng bng

cch s dng cc thut ton thch nghi (Acoustic Echo Cancellatio - AEC).

Qu trnh trit ting vng s dng cc b gii thut thch nghi LMS, RLS v mt l

thuyt cng ging nh qu trnh trit khiu thch nghi trnh by phn trn.

Hnh 3.9: Hot ng ca mt b trit ting vng

N TT NGHIP Trang 45


Hnh 3.10: S h thng trit ting vng

Trong :

(1): Tn hiu gc: x(n)

(2): Tn hiu tr k chu k mu v bin b suy gim: ax(n-kT)

(3): Khi echo: l khi tng hp gia khi (1) v khi (2):y(n)

(4): Khi x l: dng gii thut LMS trit i tn hiu tr.

(5): Tn hiu sau khi qua s l l gn ging vi tn hiu gc:x(n).

3.3.3 S dng lc thch nghi trit echo.

Tn hiu echo c a vo b lc thch nghi to ra mt bn sao ca Echo u ra

y (n) ,tn hiu cng ting vng d(n) tr i y(n) ,tn hiu li e (n) thu c t s khc

bit gia chng.

e(n) = d(n) y(n)

Hnh 3.11: S nguyn l s dng lc thch nghi trit echo.

Tn hiu gc

Tn hiu gc c

lm tr

echo X l Tn hiu gc

(1) (3) (4)

(2)

(5)

N TT NGHIP Trang 46


Thut ton LMS l mt trong nhng thut ton c s dng nhiu nht bi v n

rt d dng v n nh. Nhc im duy nht l tc hi t rt l chm .

Nhn vo hnh ta thy rt r khuyt im ny, ng mu tn hiu ng ra e(n)

phi n vng lp th 1500 mi dn hi t v gi tr 0,tn hiu echo ng ra cng c

lc nhng thi gian p ng rt lu.Chng ta s xem xt thut ton RLS sau.

Hnh 3.12: Trit echo s dng thut ton LMS

Thut ton RLS l mt cng c quan trng cho vic xc nh cc h s ca b

lc thch nghi tuyn tnh. Thut ton RLS tng phc tp, s lng cc php ton, v

tin cy. Do , RLS a ra hi t nhanh hn v li t hn, nhng i li yu cu

ph tn cho nhiu s tnh ton hn. Nhn vo hnh ta thy ng mu tn hiu e(n)

hi t v gi tr 0 trong nhng vn lp u tin, tn hiu echo c loi b ng ra rt

nhanh.

Hnh 3.13 : Trit echo s dng thut ton RLS

N TT NGHIP Trang 47


3.3.4 Mt s yu t nh hng n cht lng trit ting vng.

C mt s yu t khc nhau nh hng n hiu sut cht lng b lc trit ting

vng nh l cu trc b lc , thut ton, tc d hi t,tc x l ca chip DSP.

Tc hi t: T l hi t cn phi nhanh hn c tnh

b lc mong mun. Tc hi t gim lm cho h thng khng n nh.

B lc IIR v FIR l cu trc c bn thit k b lc trit ting vng.

B lc FIR c coi l tt hn thc hin v s n nh v kh nng tnh ton tt

hn. S hi t tc c th c ci thin bi s hi t nhanh (thut ton RLS hi t

nhanh hn LMS).

nh gi cht lng ca thut ton trit ting vng ngi ta s dng thng s

ERL(echo return loss) v (echo return loss enhancement) nh gi hiu sut.

ERL : l t s gia cng sut ca tn hiu gi n loa v cng sut ting vng tr li

ca echo, c o bng dB.

2

10 10 2

[ ( )]ERL 10log ( ) 10log ( )

[ ( )]

x

d

P E x n

P E d n

(3.6)

ERLE :c xc nh bi t s gia cng sut tn hiu gi i v cng sut tn hiu li

cn li ngay sau khi trit ting vng, n v tnh dB.

2

10 2

( ) [ ( )]ERLE=10log 10log( )

( ) [ ( )]

d

e

P n E d n

P n E e n

(3.7)

Bng 3.2: So snh thng s ERLE gia thut ton LMS v RLS.

Thut ton Average ERLE (dB)

LMS 31,52

RLS 39,22

Trong thc t mt mch trit ting vng tt,c Erle trong khong 30 dB - 40dB l

c coi l l tng.

N TT NGHIP Trang 48


.

Hnh 3.14 : Biu so snh ERLE gi thut ton RLS v LMS

Gi tr dB dc theo trc y v s lng mu vt dc theo trc x.

Biu ca Erle cho thy rng cc Erle cho thut ton LMS, RLS u t gi tr yu

cu.

Thng s ERLE s dng thut ton RLS ln hn thut ton LMS, iu c ngha

thut ton RLS tt hn LMS.

Kt lun :

Trong lun n ny, chng ti nghin cu lm th no hy b ting vng (AEC).

Mt trong nhng vn quan quan trng trong vin thng ,h thng in thoi l

lm sao loi b c ting vng. Cc thut ton thch nghi RLS, LMS c s dng

lao b Echo trnh by trong lun n ny nh l mt gii php phn mm gii quyt

cho cc vn ca ting vng trong mi trng vin thng.

AEC l phng php thng thng gii quyt cc vn ting vng. theo l tng

iu kin AEC c th t c echo hy b hon ton.

N TT NGHIP Trang 49

Chng 4 : Gii thiu phn mm CCS v Kit TMS320C6713

CHNG 4 :

GII THIU PHN MM CCS V KIT TMS320C6713

4.1 Gii thiu v phn mm CCS (Code Composer Studio).

Code Composer Studio l mi trng pht trin tch hp (IDE) xy dng ng

dng cho cc b x l tn hiu s DSP, cc vi iu khin v cc vi x l ca hng

Texas Instruments (TI).

Code Composer Studio bao gm b cc cng c s dng pht trin v g ri

cc ng dng. N bao gm cc b bin dch cho mi h ca TI, trnh son tho m

ngun, mi trng xy dng d n, g ri, profiler, m phng v nhiu c trng

khc. CCS h tr g ri thi gian thc v m phng dng ha.CCStudio IDE

cung cp mt giao din ngi dng duy nht thc hin qua cc giai on pht

trin ng dng. Cc cng c v giao din quen thuc cho php ngi s dng lm

quen nhanh chng v thm cc chc nng cho ng dng nh cc cng c.

Cc bc c bn thc hin trn CCStudio bao gm bin dch C, hp dch, lin

kt, g ri, m phng v emulator. u tin CCStudio dch m C thnh m di

dng m gi nh hoc dng i s cho DSP c th m ta la chn (ui .asm).

Bc tip theo l dch m assembly thnh m i tng di dng nh phn

(hoc ngn ng my) c th i vi DSP la chn (ui .obj). Trnh lin kt thc

hin lin kt cc file i tng to to thnh mt file i tng duy nht bng

cch gn cc a ch tuyt i trong b nh cho DSP c th (ui .out). File thc

hin ny c th ti v chy trc tip trn b DSP.

Sau khi to ra file thc hin, chng ta phi kim tra v g ri bng cch s

dng phn mm m phng v emulator.

N TT NGHIP Trang 50


Hnh 4.1: Lu pht trin phn mm to ra m i tng t ngn ng C

4.2 Gii thiu v kit TMS320C6713.

DSP Starter Kit TMS320C6713 l kit pht trin cho php ngi s dng thit

k v th nghim cc ng dng cho chip x l tn hiu s TMS320C6713

ca Texas Instruments. DSK ny c th c s dng nh mt thit k tham kho

cho giao tip gia DSP vi cc thnh phn ph bin nh SDRAM, FLASH v cc

b m ha/gii m codec. Trn Kit c b JTAG emulator cho php g ri chng

trnh t Code Composer Studio thng qua cng USB ca my tnh. DSK c cha

cc thnh phn cn thit lm vic vi DSP ca TI.DSK cng c th s dng vi

phin bn y ca Code Composer Studio v mt b JTAG emulator ngoi.

N TT NGHIP Trang 51


Hnh 4.2: Board DSK 6713

Hnh 4.3: Cc thnh phn i km vi DSK TMS320C6713

N TT NGHIP Trang 52


4.2.1 S khi v cc c trng ca kit TMS320C6713.

Hnh 4.4: S khi DSK C6713

C6713 trn DSK c 264kB b nh trong, bt u ti 0x00000000 v 16MB b nh

SDRAM ngoi, c nh x qua CE0 bt u ti 0x80000000. DSK cng bao gm

512kB b nh FLash (256kB sn sng cho ngi s dng), c nh x qua CE1 bt

u ti 0x90000000.

Mt s c trng:

DSP TMS320C6713 hot ng tn s 225MHz

Mt b codec stereo AIC23

16 Mbytes DRAM ng b

512 Kbytes b nh Flash (cu hnh mc nh 256 Kbytes)

4 LED v DIP switches

Cu hnh board bng lnh thng qua cc thanh ghi ca CPLD

Khe cm m rng

JTAG emulation

Ngun cp +5V

Chip DSP trn DSK giao tip vi cc ngoi vi trn kit thng qua b giao tip b

nh ngoi EMIF (Extrenal Memory InterFace) c rng 32 bit. SDRAM, Flash

v CPLD c kt ni vi bus. Cc tn hiu EMIF cng c kt ni vi card

m rng thng qua cc connector kt ni vi card ca hng th ba.

N TT NGHIP Trang 53


DSP giao tip vi cc tn hiu audio tng t thng qua b codec AIC23 v bn

jack audio 3.5mm (microphone input, line input, line output, headphone output). Ti

mt thi im, b codec c th la chn microphone hoc line input l u vo. Li ra

tng t c iu khin cho c line output (khuch i c nh) v headphone

(khuch i c th iu chnh). McBSP0 c s dng gi cc lnh ti b giao tip

iu khin codec trong khi McBSP1 c s dng cho d liu audio s.

CPLD (Programmable logic device) c s dng kt ni logic cc thnh

phn trn kit. CPLD giao tip ngi dng thng qua vic cho php cu hnh kit bng

cch c v ghi ti cc thanh ghi ca n.

DSK c 4 LED v 4 DIP switch cung cp cho ngi s dng cc tng tc, phn hi

n gin.

Code Composer giao tip vi DSK thng qua mt b JTAG emulator nhng sn s

dng cng USB. DSK cng c th c s dng vi mt b emulator ngoi qua kt ni

JTAG ngoi.

4.2.2 Hot ng c bn.

DSK c thit k lm vic vi phn mm pht trin Code Composer Studio

(CCStudio). Code Composer giao tip vi Kit thng qua b JTAG emulator on-board.

Sau khi ci t phn mm CCStudio, lm theo cc bc sau kt ni DSK vi my

tnh:

Kt ni DSK vi my tnh thng qua cable USB chun

Ni ngun vi DSK

Khi ng CCStudio trn my tnh

4.2.3 Bn nh.

H C67xx c khng gian a ch ln.Chng trnh v d liu c th t v tr bt

k trong khng gian nh.Cc a ch c rng 32 bit. Bn nh ch ra khng gian

a ch chung ca DSP 6713 bn tri v cc mc ch s dng c th ca DSK bn

phi. Mc nh, b nh trong nm a ch u ca khng gian a ch.Cc phn ca

b nh trong c th cu hnh li bng phn mm.EMIF c 4 vng a ch ring r c

gi CE0-CE3. SDRAM chim CE0 trong khi b nh Flash v CPLD chia s CE1. CE2

v CE3 dnh cho cc kt ni m rng.

N TT NGHIP Trang 54


Hnh 4.5: Bn nh v t chc b nh ca DSK C6713

4.3 Cc thnh phn ca kit TMS320C6713.

4.3.1 CPLD(Programmable Logic).

CPLD c s dng thc thi cc chc nng c th ca DSK. Vic thit k

phn cng thng s dng tp hp cc khi chc nng khc nhau v tn dng kh

nng tch hp cao ca DSP, trnh s dng cc thnh phn logic bn ngoi. CPLD

thc thi cc chc nng logic khc nhau loi b cc thit b thm vo h thng.

V d, CPLD kt ni nhiu cc tn hiu reset khc nhau n t cc nt reset v theo

di ngun v to ra mt tn hiu reset chung.

C6713 DSK s dng mt CPLD Altera EPM3128TC100-10. EPM3128TC100-

10 hot ng in p 3.3V, 100 chn dng ng v QFP, cha 128 macrocells,

80 chn vo/ra, thi gian tr 10 ns t chn ny n chn kia. Thit b da trn

EEPROM v c th cu hnh trong h thng thng qua giao tip JTAG. File m

ngun ca CPLD c vit theo chun cng nghip VHDL v i km vi DSK.

4.3.2 AIC23 Codec.

DSK s dng mt b codec stereo AIC23 ca Texas Instruments cho cc tn

hiu audio vo/ra. B codec ly mu cc tn hiu tng t trn microphone hoc

line input v chuyn i chng thnh tn hiu s DSP c th x l c. Khi

DSP hon thnh vic x l, n s dng b codec chuyn cc mu thnh tn hiu

N TT NGHIP Trang 55


tng t trn ng line output v headphone ngi s dng c th nghe

c.in p ln nht ca tn hiu li vo c xc nh bi mch ADC trong

codec, gi tr ny l 6 Vpp vi codec trn Kit.

Hnh 4.6: H thng DSP vi tn hiu v, ra tng t

B codec giao tip vi DSP s dng hai knh ni tip, mt iu khin

cc thanh ghi cu hnh bn trong codec v mt gi v nhn cc mu audio s.

McBSP0 c s dng nh knh iu khin mt hng. N c lp trnh gi

t iu khin c rng 16 bit ti AIC23 di nh dng SPI. 7 bit cao ca t iu

khin xc nh thanh ghi c iu chnh v 9 bit thp cha gi tr thanh ghi. Knh

iu khin ch c s dng khi cu hnh codec, n trng thi ngh khi d liu

audio ang c truyn.

McBSP1 c s dng nh knh d liu hai hng.Tt c d liu audio i qua

knh ny.Rt nhiu nh ng d liu c h tr da trn s thay i rng

mu, ngun tn hiu clock v nh dng d liu ni tip. Cc v d DSK ni chung

s dng rng mu 16 bit vi codec ch ch, n to ra tn hiu ng b

khung tc ly mu ng m khng cn s can thip ca DSP.

Codec c tn s xung nhp h thng 12MHz. B chia bn trong codec to ra cc

tn s ly mu ph bin nh 48KHz, 44.1KHz v 8KHz. Tc ly mu c t

bi thanh ghi SAMPLERATE ca codec.

N TT NGHIP Trang 56


Hnh 4.7: Giao tip ca Codec trn DSK

AIC23 l b code stereo audio, n thc hin tt c cc chc nng i

hi ca ADC, DAC, b lc thng thp, oversampling.

4.3.3 SDRAM.

DSK s dng 128 megabit b (16 megabytes) nh SDRAM giao tip qua EMIF

32 bit. SDRAM c nh a ch ti a ch bt u CE0 (c a ch 0x8000

0000).B iu khin SDRAM c tch hp l mt phn ca EMIF v phi c

cu hnh bng phn mm hot ng thch hp. Xung nhp EMIF c tnh t

xc lp PLL nn c cu hnh bng phn mm tn s 90MHz. Con s ny da

trn trn mt xung nhp ni ca PLL l 450MHz thu c tn s hot ng

225MHz nh b chia 2 v 90MHz nh b chia 5.

Khi s dng SDRAM, b iu khin phi c xc lp lm ti mi hng

ca mng nh mi 15.6 micro giy duy tr d liu. Vi tn s xung nhp 90Mhz

ca EMIF, thi gian ny tng ng vi 1400 chu k bus.

N TT NGHIP Trang 57


Hnh 4.8: S khi TLV320AIC23 codec

4.3.4 B nh FLASH.

Flash l loi b nh khng mt ni dung khi mt ngun. Khi c n ging nh

mt b nh ROM. Flash c th c xa theo cc khi ln c c gi l cc

sector hoc trang. Mt khi mt khi c xa mi t c th c lp trnh

thng qua mt chui lnh c bit.Sau ton b khi phi c xa li ln na

thay i ni dung.

DSK s dng 512Kbyte b nh Flash ngoi lm ty chn khi ng. N c a

ch bt u ca CE1 (a ch 0x9000 0000). Flash c ni to ra b nh 256K 16

bit h tr ty chn khi ng 16-bit ca DSK. Tuy nhin, phn mm i km vi

DSK coi b nh Flash l b nh 8 bit (b qua 8 bit cao) ph hp vi ch

khi ng mc nh ca 6713. Trong cu hnh ny, ch c 256 Kbytes c th s

dng khi khng thay i phn mm.

N TT NGHIP Trang 58


4.3.5 LED v Switch.

DSK c 4 led truy nhp c bng phn mm (D7-D10) v DIP switch cung

cp cho ngi s dng cch vo/ra n gin. C Led v switch c truy nhp

thng qua thanh ghi USER_REG ca CPLD.

4.3.6 Giao tip card m rng.

DSK cung cp ba connector m rng c th c s dng cm cc card.

Connector kt ni vi b nh, thit b ngoi vi v HPI.

N TT NGHIP Trang 59

Chng 5 :Thc hin kh nhiu,trit echo trn KIT TMS320C6713

CHNG 5 :

KH NHIU,TRIT ECHO TRN KIT TMS320C6713

5.1 Kh nhiu thch nghi bng thut ton LMS trn kit TMS320C6713.

Hnh 5.1: M hnh kh nhiu thch nghi dng thut ton LMS

Hnh 5.2: M hnh chi tit khi Noise Channel

N TT NGHIP Trang 60


Tin hnh bin dch, np code ln kit TMS320C6713. Quan st dng sng tn hiu

vo ra.

Hnh 5.3: M hnh kt ni kit TMS320C6713 h thng ANC

Tn hiu ng vo c ly t my pht sng v microphone

Hnh 5.4: Tn hiu ng vo h thng trit nhiu thch nghi dng thut ton LMS.

N TT NGHIP Trang 61


Tn hiu ng vo input ca b lc LMS, tn hiu cng nhiu c a vo ng

Desired ca b lc LMS.

Hnh 5.5: Dng sng tn hiu ng vo cng vi nhiu dng thut ton LMS.

Kt qu: Tn hiu nhiu sau khi i qua b lc LMS ging vi tn hiu ban u.

Hnh 5.6: Dng sng tn hiu thu c sau khi trit nhiu dng thut ton LMS.

Nhn xt

Tn hiu thu c gn chnh xc so vi tn hiu ban u. Thay i gi tr variance trong

khi nhiu Gause cng ln th tn hiu thu c cng nhiu.

N TT NGHIP Trang 62


Hm PDF ca bin ngu nhin Gauss, z, c cho bi:

2 2( ) /21( )2

zp z e

Bng 5.1: Bng thng k gi tr bin thu c khi thay i thng s variance

5.2 Kh nhiu thch nghi bng thut ton RLS trn kit TMS320C6713.

Hnh 5.7: S h thng lc nhiu s dng thut ton RLS.

Mean

( )

Variance

( 2 )

Gi tr bin

tn hiu ng vo

(V)

Gi tr bin

tn hiu thu c

(V)

Suy hao

0 0.05 5.04 2.48 -6.16

0 0.2 5.04 2.6 -5.75

0 0.4 5.04 2.76 -5.23

0 0.6 5.04 2.24 -7.04

0 0.8 5.04 2.84 -4.98

0 1 5.04 2.4 -6.44

N TT NGHIP Trang 63


Tn hiu ng vo input ca b lc RLS, tn hiu cng nhiu ( 2 =1) ti ng vo

Desired ca b lc RLS

Hnh 5.8: Dng sng tn hiu ng vo cng vi nhiu dng thut ton RLS

Kt qu :Tn hiu nhiu sau khi i qua b lc RLS , ging vi tn hiu sng sin ban

u.

Hnh 5.9: Dng sng tn hiu thu c sau khi trit nhiu dng thut ton RLS

Kt lun:

- Kt qu thu c sau khi qua b lc RLS tt, tn hiu nhiu b loi b.

- B lc thch nghi rt tt trong qu trnh kh nhiu

N TT NGHIP Trang 64


5.3 Trit Echo dng thut ton LMS trn KIT TMS320C6713.

Hnh 5.10: M hnh kt ni kit TMS320C6713 h thng AEC.

Hnh 5.11: H thng to ting vng

N TT NGHIP Trang 65


Hnh 5.12: H thng trit ting vng dng thut ton LMS

Tn hiu ng vo c ly t my pht sng, v microphone

Hnh 5.13: Dng sng tn hiu ng vo h thng trit Echo dng thut ton LMS.

N TT NGHIP Trang 66


Tn hiu ng vo input ca b lc LMS, tn hiu echo c a vo ng Desired ca

b lc LMS.

Hnh 5.14: Dng sng tn hiu echo dng thut ton LMS.

Kt qu: Tn hiu nhiu sau khi i qua b lcLMS ging vi tn hiu ban u.

Hnh 5.15: Dng sng tn hiu thu c sau khi trit Echo dng thut ton LMS.

Kt lun:

- Kt qu thu c sau khi qua b lc LMS tt, tn hiu echo b loi b.

- B lc thch nghi dng thut ton LMS rt n gin nhng hiu qu trong qu

trnh kh echo .

N TT NGHIP Trang 67


5.4 Trit echo s dng thut ton RLS trn kit TMS320C6713.

Hnh 5.16: S h thng trit echo s dng thut ton RLS.

Tn hiu ng vo s ng sin c ly t my pht sng, v Tn hiu echo c vo ng

Desired ca b lc RLS.

Hnh 5.17: Dng sng tn hiu Echo dng thut ton RLS

N TT NGHIP Trang 68


Kt qu : Tn hiu ng vo ging vi tn hiu ng ra ,bin c suy gim so vi ban

u.

Hnh 5.18: Dng sng tn hiu thu c sau khi trit echo dng thut ton RLS.

Kt lun:

- Kt qu thu c sau khi qua b lc RLS tt, tn hiu echo b loi b.

- B lc thch nghi rt tt trong qu trnh kh echo .

N TT NGHIP Trang 69

Chng 6 : Kt lun

CHNG 6 : KT LUN

6.1 Kt qu t c.

Sau qu trnh thc hin nghin cu ti, nh m thu c mt s kt qu sau :

- Tm hiu l thuyt b lc s, lc thch nghi, echo, kit DSP TMS320C6713.

- Tm hiu cc thut ton thch nghi, nguyn tc hot ng, cch thc cp nht

trng s.

Thut ton LMS:

n gin, d thc hin, tnh ton khng phc tp.

Tc hi t chm.

Thut ton RLS:

Tng s lng cc php ton, tnh ton phc tp.

Tc hi t nhanh, tin cy cao.

- M phng cc h thng trit nhiu tch cc - ANC (active noise canceller) v h

thng kh echo AEC (acoustic echo canceller) s dng cc thut ton LMS,RLS

bng Matlab t kt qu tt.

- Da vo kt qu m phng nh gi, kim chng li c u im ca thut ton

RLS so vi LMS qua thng s MSE v ERLE.

- Thc hin cc thut ton thch nghi trn Kit DSP TMS320C6713 t c mt s

kt qu nht nh.

6.2 Tn ti v hng pht trin ca ti.

6.2.1 Nhng mt cn tn ti :

- Cc m hnh m phng trn Matlab, Kit DSP TMS320C6713 ch dng li mc

tm hiu, nh gi, cha ph hp vi cc ng dng ca h thng thc t.

- Thit k b lc thch nghi da trn ngn ng Matlab khi bin dch sang ngn ng

C, vic ny s lm tn ti nguyn b nh ca Kit DSP TMS320C6713.

N TT NGHIP Trang 70

Chng 6 : Kt lun

- Thc hin thut ton RLS trn kit DSP TMS320C6713 cha t c kt qu nh

mong mun.

6.2.2 Hng pht trin.

- Tip tc tm hiu, nghin cu chuyn su hn, ti u ho thut ton xy dng,

hon thin m hnh kh nhiu, trit echo qu hn.

- Pht trin ln thnh h thng x l a knh ngha l c nhiu hn 1 ngun m kh

nhiu. Mc ch nhm t c hiu qu kh nhiu trong khng gian rng hn.

- nh hng pht trin c th xy dng trin khai cc h thng ln c tnh ng

dng trong thc t, v d nh lc nhiu tn hiu in tim, h thng trit nhiu trong

xe hi, tai nghe trit nhiu tch cc, cc thit b thu tn hiu trong y t, trit echo

trong cc hi nghi trc tip,

N TT NGHIP Trang 71

Phn C: Ph lc v ti liu tham kho

PHN C : PH LC V

TI LIU THAM

KHO

N TT NGHIP Trang 72


PH LC

Ph lc A.

1. Hng dn bin dch Simulink sang code C.

Simulink l mt mi trng ng dng dng m phng v thit k cc m hnh

c s cho ng hc cng nh cc h thng nhng nhiu lnh vc khc nhau nh

giao tip, iu khin, x l tn hiu s, x l video, hnh nh. Vi mt giao din giao

ha trc quan t th vin cc block chc nng ca chng trnh, bn c th thit k,

m phng, thc thi chng trnh v kim tra h thng cc thi im khc nhau v

cui cng s l kt qu ca chng trnh c th hin bng th v biu bng. u

tin bn m Simulink ca Matlab ln v tin hnh ghp ni cc khi theo mc tiu ca

ti. i vi nhng phin bn Matlab khc nhau th v tr ly cc khi c thay i

cht t, chng ti ang trnh by y l Matlab 2010a. V phn mm Code

Composer Studio V 3.3 (CCS V3.3) build v load ln KIT TMS320C6713.

By gi chng ti ang tin hnh thit k mt h thng Pht Thu tn hiu cc bc

tin hnh nh sau:

1.1 Ghp ni cc khi.

-Chn khi I/O v Board C6713DSK: Target Support Package / Texas Intruments

C6000 / C6713DSK.

-Chn cc khi Gain, Digital filer , C6713 ADC, C6713 DAC trong mc Libraries v

sau kt ni li nh hnh bn di.

N TT NGHIP Trang 73


- Thit lp thng s bng cch nhp i vo cc khi

+ Khi ADC

N TT NGHIP Trang 74


+ Khi Gain.

+ Khi DAC.

1.2 Thit lp cu hnh cc thng s trc khi build.

Sau khi chy m phng thnh cng trn Simulink th bn c th bin dch sang

CCS nh sau:

- Ln u tin bn g ticcs tch hp phin CCS vi Matlab

N TT NGHIP Trang 75


- Sau g ccsboardinfo kt ni CCS vi Matlab

-M ca s Simulink mun bin dch ln

Vo Simulation chn Configuration Parameter.

Hoc nhn t hp phm Ctrl + E.

N TT NGHIP Trang 76


1.3 Build simulink sang ANSI C code .

Nhn vo biu tng Increment Build hoc nhn t hp phm Ctrl+B.

-Sau khi build xong , s t ng m ca s lm vic CCS V3.3. vi y th vin

,code C ca chng trnh dch t simulink sang.

N TT NGHIP Trang 77


-By gi ta c th load file .out np ln Kit TMS320C6713.

N TT NGHIP Trang 78


-Kt ni thit b ngoi vi vo KIT C6713

N TT NGHIP Trang 79


2. Hng dn ci t CCS V3.3 trn Windows XP.

Tin hnh ci t chng trnh.

- Chn Next tip tc qu trnh ci t

- Sau khi tha mn yu cu v cu hnh,chn Next tip tc

N TT NGHIP Trang 80


- Chn Accept tip tc

- Chn Typical Install hoc Custom Install

- Cui cng chn Finish kt thc.

Composer studio setup.

-Chn C6713 Device Cycle Accurate Simulator

Khi khng c KIT C6713 chng ta c th thit lp ch m phng v lm

vic bnh thng.

N TT NGHIP Trang 81


-Ta kch chn code

- Giao din Code Composer Studio trn Windows XP

N TT NGHIP Trang 82


Ph lc B : Code Matlab. 1. Kh nhiu thch nghi s dng thut ton LMS.

% ANC - LMS algorithm

% R - number of repetitions

% I - iterations

% sigmax - standard deviation of the input signal x

% Wo - plant/system to be identified

% sigman - standard deviation of the noise n

% mi - step-size parameter

% M - misadjustment

% ind - sample index

% MSE - Mean-squared error

% MSEmin - Minimum Mean-squared error

% K - Auxiliar vector to store the error btween the

% orignal signal and the error signal.

% E - Auxiliar vector to the error

%Px - cong suat tin hieu ngo vao

%Pe - cong suat tin hieu error

%Pn - cong suat nhieu

clear all;

close all;

R=10;

I=50000;

%Length of the adaptive filter

L=5;

N=L-1;

mi= 0.0002;

MSE=zeros(I,1);

E=zeros(I,1);

K=zeros(I,1);

for r=1:R

%input signal

n = (1:I)';

s = sin(0.075*pi*n);

%noise source signal

v = 0.8*randn(I,1);

%noise

loc thich nghi

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