mophonghttt_ch4

1052/10/2012Nguyn c Nhn

M phng tn hiu bng gc v thng di: Tn hiu bng gc (baseband): c ph tn tp trung quanh tn

s 0.

Tn hiu thng di (passband): c ph tn tp trung quanh mttn s sng mang fc.


s 0.


Tn hiu bng gc c th c chuyn ithnh tn hiu thng di qua qu trnh itn ln (up-conversion)

Tn hiu thng di c th c chuyn ithnh tn hiu bng gc qua qu trnh itn xung (down-conversion)

Tn hiu thng di sP(t) c xy dng thai tn hiu bng gc sI(t) v sQ(t) (trongiu ch s)

2/10/2012Nguyn c Nhn 106


s 0.


Tn hiu bng gc c th c chuyn ithnh tn hiu thng di qua qu trnh itn ln (up-conversion)

Tn hiu thng di c th c chuyn ithnh tn hiu bng gc qua qu trnh itn xung (down-conversion)

Tn hiu thng di sP(t) c xy dng thai tn hiu bng gc sI(t) v sQ(t) (trongiu ch s)

M phng tn hiu bng gc v thng di: Tn hiu thng di c th c vit:

nh ngha tn hiu s(t): tn hiusP(t) c th vit li

Tn hiu s(t): c gi l tn hiu tng ng bng gc hoc lp v phc ca tn hiu

thng di sP(t)

Cha cng thng tin nh sP(t)

s(t) l tn hiu phc




thng di sP(t)


s(t) l tn hiu phc

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thng di sP(t)


s(t) l tn hiu phc

M phng tn hiu bng gc v thng di: Trong min tn s:

H s m bo c hai loi tn hiu c cng mc cng sut.

M phng tn hiu bng gc v thng di: Trong min tn s:

H s m bo c hai loi tn hiu c cng mc cng sut.2

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M phng tn hiu bng gc v thng di: M hnh thng di:


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M phng tn hiu bng gc v thng di: M hnh tng ng thng thp:

M phng tn hiu bng gc v thng di: M hnh tng ng thng thp:

Thu c h thng tng ng bng gc:s dng cc tn hiu bng gc

Tn hiu pht tng ng bng gc: Knh tng ng bng gc vi p ng xung kim

gi tr phc h(t) vi Tn hiu thu tng ng bng gc: R(t) Nhiu Gaussian cng gi tr phc: N(t)

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Thu c h thng tng ng bng gc:s dng cc tn hiu bng gc

Tn hiu pht tng ng bng gc: Knh tng ng bng gc vi p ng xung kim

gi tr phc h(t) vi Tn hiu thu tng ng bng gc: R(t) Nhiu Gaussian cng gi tr phc: N(t)


Cc tn hiu l thc

St vi h thng thc

Tn s ly mu cao hn

M hnh tng ng thng thp: Cc tn hiu l phc

M hnh gn v n gin hn

Tn s ly mu thp hn

Trong cc trng hp thc t, x l tn hiu s c thc hin trn tn hiuc chuyn i bng gc.

M hnh tng ng bng gc l thun tin hn trong mphng h thng.

H thng tuyn tnh:


Cc tn hiu l thc

St vi h thng thc

Tn s ly mu cao hn


M hnh gn v n gin hn

Tn s ly mu thp hn



H thng tuyn tnh:

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Cc tn hiu l thc

St vi h thng thc

Tn s ly mu cao hn


M hnh gn v n gin hn

Tn s ly mu thp hn



H thng tuyn tnh:

Qu trnh ly mu v ni suy: Trong m phng h thng truyn tin trn h thng my tnh s

i hi s chuyn i m hnh thi gian lin tc thnh m hnhri rc v thi gian.

Theo nh l ly mu Nyquist (hoc Shannon): nu Bs l rngbng tn ca tn hiu bng gc s(t) tn s ly mu fs 2Bs.

Qu trnh ly mu: s(t) ss(t) = s(nTs)vi

trong : Ts chu k ly mu, fs = 1/Ts tn s ly mu

Tn s ly mu c la chn ph hp gim thiu li chngph m trnh tng thi gian m phng.







( ) ( ) ( )ss t s t p t ( ) ( )sn

p t t nT

( ) ( ) ( )s s s

n

s t s nT t nT

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Qu trnh ly mu v ni suy: Trong mt s trng hp m phng h thng trn cc rng

bng tn khc nhau chuyn i tc mu Tng mu (upsampling): ti bin gia phn tn hiu bng hp v bng rng

s(kTs) s(kTu) = s(kTs/M) Gim mu (downsampling): ti bin gia phn tn hiu bng rng v bng

hp s(kTs) s(kTd) = s(kMTs) Qu trnh ni suy: quan trng trong k thut a tc

B ni suy hm sinc

B ni suy tuyn tnh

Trong MATLAB s dng hm interp:

y = interp(x,r) thc hin ly li mu gi tr trong vect x ti rln tc ly mu ban u.





B ni suy hm sinc

B ni suy tuyn tnh



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B ni suy hm sinc

B ni suy tuyn tnh



Ngun tn hiu tng t: Tn hiu n tn:

hoc

Tn hiu a tn: vi0( ) cos(2 )k kx t A f t 0( ) exp(2 / )exp( )sx k A jkf f j


hoc

Tn hiu a tn: vi0( ) cos(2 )k kx t A f t 0( ) exp(2 / )exp( )sx k A jkf f j

1( ) ( )

M

k n kn

x t x t

( ) cos(2 )n k n n k nx t A f t 1

( ) exp(2 / )exp( )M

n n s n

n

x k A jkf f j

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hoc

Tn hiu a tn: vi

Ngun tn hiu s: Ngun thng tin ri rc thng c gi tr trong bng alphabet.

Tn hiu s: l dng sng mang thng tin s.

C 3 tham s chnh: Kiu ngun (alphabet): danh sch cc k hiu thng tin c th m ngun to

ra. VD: A = {0,1}; cc k hiu c gi l bit

Vi M k hiu (M = 2n): A = {0, 1,..., M-1} hoc A = {1, 3, ..., (M-1)} Cc symbol c th c gi tr phc: A = {1, j}

Xc sut u tin pht: tn s xut hin tng i ca mi k hiu m ngunto ra.

VD: ngun sinh ra cc bt 0 v 1 c xc sut bng nhau

Tc k hiu (symbol rate): s lng k hiu thng tin m ngun sinh ratrong mt n v thi gian (baud rate)









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Ngun tn hiu ngu nhin: Cc ngun tin trong thc t l ngu nhin to cc tn hiu

ngu nhin trong m phng.

To bin ngu nhin phn b u: .

S dng hm rand trong MATLAB





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>> x = rand(5,10) - To ma trn 5x10 cc s ngu nhin phn b u trong khong [0,1]

To cc s ngu nhin phn b u trong khong [a, b] :>> x = a + (b-a) * rand(m,n)To cc s nguyn ngu nhin phn b u trn tp 1:n :>> x = ceil(n.*rand(100,1));

Ngun tn hiu ngu nhin: To bin ngu nhin phn b u: .V d: To vect hng 1000 s ngu nhin phn b u trong khong [0,1], hin th 10 s u tin>> x = rand(1,1000);>> x(1:10)

ans =

0.4330 0.8424 0.1845 0.5082 0.4522 0.3256 0.3801 0.8865 0.7613 0.8838

>> hist(x,10)

Ngun tn hiu ngu nhin: To bin ngu nhin phn b u: .V d: To vect hng 1000 s ngu nhin phn b u trong khong [0,1], hin th 10 s u tin>> x = rand(1,1000);>> x(1:10)

ans =

0.4330 0.8424 0.1845 0.5082 0.4522 0.3256 0.3801 0.8865 0.7613 0.8838

>> hist(x,10)

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

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Ngun tn hiu ngu nhin: To bin ngu nhin phn b chun:

S dng hm randn trong MATLAB .



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To cc s ngu nhin phn b chun c trung bnh bng 0 v lch chun bng 1 :

>> x = randn(m,n)

To cc s ngu nhin phn b chun c trung bnh bng m v phng sai v :

>> x = m + sqrt(v) * randn(m,n)

Ngun tn hiu ngu nhin: To bin ngu nhin phn b chun:V d: To vect hng 1000 s ngu nhin phn b chun c trung bnh 0 v lch chun bng 1, hinth 10 s u tin>> x = randn(1,1000);>> x(1:10)

ans =

-0.6028 -0.9934 1.1889 2.3880 2.2655 2.3011 -0.2701 0.5028 -0.1192 -0.0019

>> hist(x,10)

Ngun tn hiu ngu nhin: To bin ngu nhin phn b chun:V d: To vect hng 1000 s ngu nhin phn b chun c trung bnh 0 v lch chun bng 1, hinth 10 s u tin>> x = randn(1,1000);>> x(1:10)

ans =

-0.6028 -0.9934 1.1889 2.3880 2.2655 2.3011 -0.2701 0.5028 -0.1192 -0.0019

>> hist(x,10)

-4 -3 -2 -1 0 1 2 3 40

50

100

150

200

250

300

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-4 -3 -2 -1 0 1 2 3 40

50

100

150

200

250

300

Ngun tn hiu ngu nhin: To s nguyn ngu nhin phn b u:

S dng hm randint trong MATLAB:


S dng hm randint trong MATLAB:To ma trn mxn cc s 0 v 1 c xc sut bng nhau

>> x = randint(m,n);

V d:

>> x = randint(1,10)

x =

0 0 1 1 1 0 1 1 0 0

To ma trn mxn c cc gi tr phn b u trong di t 0 n 7

>> x = randint(m, n, [0, 7]); hoc

>> x = randint(m,n, 8);

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S dng hm randint trong MATLAB:To ma trn mxn cc s 0 v 1 c xc sut bng nhau

>> x = randint(m,n);

V d:

>> x = randint(1,10)

x =

0 0 1 1 1 0 1 1 0 0

To ma trn mxn c cc gi tr phn b u trong di t 0 n 7

>> x = randint(m, n, [0, 7]); hoc

>> x = randint(m,n, 8);

Ngun tn hiu ngu nhin: To symbol ngu nhin theo danh sch alphabet nh trc:

S dng hm randsrc trong MATLAB:

To ngun li ngu nhin:

S dng hm randerr trong MATLAB





To ma trn mxn cc s -1 v 1 c xc sut bng nhau>> x = randsrc(m,n);V d:>> x = randsrc(1,10)

x =

-1 1 1 -1 -1 -1 -1 1 1 1

To ma trn mxn c cc gi tr phn b u trong tp {-3,-1,1,3}>> x = randsrc(10,10,[-3 -1 1 3]); hoc>> x = randsrc(10,10,[-3 -1 1 3; .25 .25 .25 .25]);

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To ma trn mxn cc s -1 v 1 c xc sut bng nhau>> x = randsrc(m,n);V d:>> x = randsrc(1,10)

x =

-1 1 1 -1 -1 -1 -1 1 1 1

To ma trn mxn c cc gi tr phn b u trong tp {-3,-1,1,3}>> x = randsrc(10,10,[-3 -1 1 3]); hoc>> x = randsrc(10,10,[-3 -1 1 3; .25 .25 .25 .25]);

M ha ngun: Qu trnh chuyn i A/D:

Qu trnh PCM: Lng t ha u

Lng t ha khng u

Analogsignal

Digitalsignal



Lng t ha khng u

Sampler Quantizer CoderAnalogsignal

Digitalsignal

sampling quantization coding

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Lng t ha khng u

M ha ngun: MATLAB code cho qu trnh PCM lng t ha u:

function [code,xq,sqnr] = uniform_pcm(x,M)% Uniform PCM encoding of a sequence% x = input sequence% M = number of quantization levels% code = the encoded output% xq = quantized sequence before encoding% sqnr = signal to quantization noise ratio in dB% Written by Nguyen Duc Nhan - 2012

Nb = log2(M);Amax = max(abs(x));delta = 2*Amax/(M-1);Mq = -Amax:delta:Amax;Ml = 0:M-1;

xq = zeros(size(x));xcode = xq;for k = 1:Mind = find(x > Mq(k)-delta/2 & x Mq(k)-delta/2 & x Mq(k)-delta/2 & x

M ha ngun: Qu trnh PCM lng t ha khng u: V d theo lut

%% nonuniform PCM processmu = 255;M = 32; % number of quantization levels[y,amax] = mulaw(x,mu); % compress the signal[code,yq,sqnr] = uniform_pcm(y,M); % codingxq = invmulaw(yq,mu); % expand the signalxq = xq*amax;sqnr = 20*log10(norm(x)/norm(x-xq)); % in dB

M ha ngun: Qu trnh PCM lng t ha khng u: V d theo lut

%% nonuniform PCM processmu = 255;M = 32; % number of quantization levels[y,amax] = mulaw(x,mu); % compress the signal[code,yq,sqnr] = uniform_pcm(y,M); % codingxq = invmulaw(yq,mu); % expand the signalxq = xq*amax;sqnr = 20*log10(norm(x)/norm(x-xq)); % in dB

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1

-0.5

0

0.5

1

Time (ms)

Amplit

ude

Vi du ve nonuniform PCM

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1

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ude


Lng t ha khng u

Tn hiu lng t ha sau khi nn

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0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1

-0.5

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Amplit

ude


0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2-1

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Time (ms)

Amplit

ude


Lng t ha u

Lng t ha khng u

M ng: Kiu m ha to dng ph v mt s c tnh xc nh ca

xung tn hiu h tr cho qu trnh ng b.

Gm 2 bc: Sp xp logic

Chuyn i thnh dng sng

V d:





V d:

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V d:

M non-return-to-zero (NRZ)

M Manchester

M NRZ-AMI

M ng: To chui xung vung:

Trong mi chu k xung, hm xungvung c nh ngha nh sau:

function [t,y] = rectpulse(Tw,Rp,Ns,Np)% Chuong trinh vi du tao chuoi xung vuong% Tw - the pulsewidth% Rp - the repetition rate of pulse Tp < 1/Rp% Ns - the number of samples% Np - the number of pulses (the length of pulse train)% t - the time vector output% y - the vector output of the pulse samples% written by Nguyen Duc Nhan

Tp = 1/Rp; % pulse periodTimewindow = Np*Tp; % time windowts = Timewindow/(Ns-1); % sampling timet = 0:ts:Timewindow; % time vectorNsp = round(Tp/ts); % number of samples within Tp

y = zeros(size(t));for k = 1:Ns

if mod(t(k),Nsp*ts) [t,y]=rectpulse(0.5e-6,1e6,256,8);

>> plot(t,y);

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M ng: To chui xung vung:

Trong mi chu k xung, hm xungvung c nh ngha nh sau:

function [t,y] = rectpulse(Tw,Rp,Ns,Np)% Chuong trinh vi du tao chuoi xung vuong% Tw - the pulsewidth% Rp - the repetition rate of pulse Tp < 1/Rp% Ns - the number of samples% Np - the number of pulses (the length of pulse train)% t - the time vector output% y - the vector output of the pulse samples% written by Nguyen Duc Nhan

Tp = 1/Rp; % pulse periodTimewindow = Np*Tp; % time windowts = Timewindow/(Ns-1); % sampling timet = 0:ts:Timewindow; % time vectorNsp = round(Tp/ts); % number of samples within Tp

y = zeros(size(t));for k = 1:Ns

if mod(t(k),Nsp*ts)

M ng: M NRZ:

function [t,y,code] = nrzcode(d,R,Ns,type)% Chuong trinh vi du ve ma duong truyen NRZ% d - the data sequence% R - the data rate% Ns - the number of samples% t - the time vector output% y - the vector output of the pulse samples% type - the type of code (unipolar - 'unipol' or polar - 'pol')% written by Nguyen Duc Nhan

Tb = 1/R; % bit periodNb = length(d); % number of bitsTimewindow = Nb*Tb; % time windowts = Timewindow/(Ns-1); % sampling timet = 0:ts:Timewindow; % time vectory = zeros(size(t));code = [];

if nargin = Nb

n = Nb;endswitch (type)

case 'unipol'y(k) = d(n);code(n) = d(n);

case 'pol'y(k) = 2*d(n)-1;code(n) = 2*d(n)-1;

endend

M ng: M NRZ:

function [t,y,code] = nrzcode(d,R,Ns,type)% Chuong trinh vi du ve ma duong truyen NRZ% d - the data sequence% R - the data rate% Ns - the number of samples% t - the time vector output% y - the vector output of the pulse samples% type - the type of code (unipolar - 'unipol' or polar - 'pol')% written by Nguyen Duc Nhan

Tb = 1/R; % bit periodNb = length(d); % number of bitsTimewindow = Nb*Tb; % time windowts = Timewindow/(Ns-1); % sampling timet = 0:ts:Timewindow; % time vectory = zeros(size(t));code = [];

if nargin = Nb

n = Nb;endswitch (type)

case 'unipol'y(k) = d(n);code(n) = d(n);

case 'pol'y(k) = 2*d(n)-1;code(n) = 2*d(n)-1;

endend

0 20 40 60 80 100 120 140 1600

0.2

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Time (ps)

Amplit

ude

h = [ 0 0 1 1 0 0 1 1 1 1 1 1 0 1 0 1 ]

0 20 40 60 80 100 120 140 160-1

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Time (ps)

Amplit

ude

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0.4

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Time (ps)

Amplit

ude

h = [ 0 0 1 1 0 0 1 1 1 1 1 1 0 1 0 1 ]

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Time (ps)

Amplit

ude

M ng: M AMI:

function [t,y,code] = amicode(d,R,Ns,type)% Chuong trinh vi du ve ma AMI% d - the data sequence% R - the data rate% Ns - the number of samples% t - the time vector output% y - the vector output of the pulse samples% type - the type of code (NRZ - 'NRZ' or RZ - 'RZ')% written by Nguyen Duc Nhan...

y = zeros(size(t));code = [];...

s = 1;for k = 1:Nb

if d(k) == 0code(k) = 0;

elses = s+1;if mod(s,2)==0

code(k) = 1;else

code(k) = -1;end

endend...

M ng: M AMI:

function [t,y,code] = amicode(d,R,Ns,type)% Chuong trinh vi du ve ma AMI% d - the data sequence% R - the data rate% Ns - the number of samples% t - the time vector output% y - the vector output of the pulse samples% type - the type of code (NRZ - 'NRZ' or RZ - 'RZ')% written by Nguyen Duc Nhan...

y = zeros(size(t));code = [];...

s = 1;for k = 1:Nb

if d(k) == 0code(k) = 0;

elses = s+1;if mod(s,2)==0

code(k) = 1;else

code(k) = -1;end

endend...

code = 0 0 1 -1 0 0 1 -1 1 -1 1 -1 0 1 0 -1

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ude

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ude

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ude

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ude

M ha knh: Tng hiu nng ca knh truyn:

Pht hin li

Sa li

Gm 2 loi chnh: M khi

M xon

V d m khi: M ha: T m

Khong cch Hamming ti thiu:

i vi m khi tuyn tnh: khong cch ti thiu bng vi trng s nh nhtca m


Pht hin li

Sa li


M xon




Trong : u chui d liu c k bit, G ma trn to m c kxn, c t m c m ha c n bit (n>k)

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Pht hin li

Sa li


M xon




Trong : u chui d liu c k bit, G ma trn to m c kxn, c t m c m ha c n bit (n>k)

M ha knh: V d m khi:

% Chuong trinh vi du ve ma hoa kenh% Block codingk = 4;for i=1:2^4for j=k:-1:1if rem(i-1,2^(-j+k+1))>=2^(-j+k)u(i,j)=1;

elseu(i,j)=0;

endend

end% Define G, the generator matrixg = [1 0 0 1 1 1 0 1 1 1;

1 1 1 0 0 0 1 1 1 0;0 1 1 0 1 1 0 1 0 1;1 1 0 1 1 1 1 0 0 1];

% generate codewordsc = rem(u*g,2);% find the minimum distancew_min = min(sum((c(2:2^k,:))'));

M ha knh: V d m khi:


elseu(i,j)=0;

endend


1 1 1 0 0 0 1 1 1 0;0 1 1 0 1 1 0 1 0 1;1 1 0 1 1 1 1 0 0 1];


c =

0 0 0 0 0 0 0 0 0 01 1 0 1 1 1 1 0 0 10 1 1 0 1 1 0 1 0 11 0 1 1 0 0 1 1 0 01 1 1 0 0 0 1 1 1 00 0 1 1 1 1 0 1 1 11 0 0 0 1 1 1 0 1 10 1 0 1 0 0 0 0 1 01 0 0 1 1 1 0 1 1 10 1 0 0 0 0 1 1 1 01 1 1 1 0 0 0 0 1 00 0 1 0 1 1 1 0 1 10 1 1 1 1 1 1 0 0 11 0 1 0 0 0 0 0 0 00 0 0 1 0 0 1 1 0 01 1 0 0 1 1 0 1 0 1

u =

0 0 0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

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elseu(i,j)=0;

endend


1 1 1 0 0 0 1 1 1 0;0 1 1 0 1 1 0 1 0 1;1 1 0 1 1 1 1 0 0 1];


c =

0 0 0 0 0 0 0 0 0 01 1 0 1 1 1 1 0 0 10 1 1 0 1 1 0 1 0 11 0 1 1 0 0 1 1 0 01 1 1 0 0 0 1 1 1 00 0 1 1 1 1 0 1 1 11 0 0 0 1 1 1 0 1 10 1 0 1 0 0 0 0 1 01 0 0 1 1 1 0 1 1 10 1 0 0 0 0 1 1 1 01 1 1 1 0 0 0 0 1 00 0 1 0 1 1 1 0 1 10 1 1 1 1 1 1 0 0 11 0 1 0 0 0 0 0 0 00 0 0 1 0 0 1 1 0 01 1 0 0 1 1 0 1 0 1

u =

0 0 0 00 0 0 10 0 1 00 0 1 10 1 0 00 1 0 10 1 1 00 1 1 11 0 0 01 0 0 11 0 1 01 0 1 11 1 0 01 1 0 11 1 1 01 1 1 1

iu ch tn hiu tng t: iu ch bin AM:

Tn hiu bn tin:

Tn hiu sng mang:

Qu trnh iu ch: l mt qu trnh nhn

su iu ch (modulation index):


Tn hiu bn tin:

Tn hiu sng mang:



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Tn hiu bn tin:

Tn hiu sng mang:




% Chuong trinh vi du ve dieu che AM%% Set parameters% MessageA = 1; % amplitudef = 440; % frequency [Hz]phi = -pi/4; % Phase [rad]

% Carrierm = 0.5; % modulation indexAc = A/m; % amplitudefc = 5e3; % frequency [Hz]phi_c = 0; % Phase [rad]

N = 2^9; % number of samplesT0 = 0; % start time [s]Tf = 5e-3; % end time [s]Ts = (Tf-T0)/(N-1); % sampling periodfs = 1/Ts; % sampling frequency [Hz]

%% Amplitude Modulation% Generate sinusoidt = T0:Ts:Tf; % time vectorx = A*cos(2*pi*f*t+phi); % message signalxc = Ac*cos(2*pi*fc*t+phi_c); % carrier signal

% Modulationy = (1+x/Ac).*xc;

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-3

-2

-1

0

1

2

3

Time (ms)

Amplit

ude

Vi du ve dieu che AM






% Modulationy = (1+x/Ac).*xc;

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-3

-2

-1

0

1

2

3

Time (ms)

Amplit

ude


0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

Time (ms)

Amplit

ude


M = 50%

2/10/2012Nguyn c Nhn 132





% Modulationy = (1+x/Ac).*xc;0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

Time (ms)

Amplit

ude


M = 100%


iu ch SSB (Single side band): S dng b lc hoc dng khai trinHilbert


iu ch SSB (Single side band): S dng b lc hoc dng khai trinHilbert

%% SSB Modulation% Generate sinusoidt = T0:Ts:Tf;x = A*cos(2*pi*f*t+phi);% Modulationy = ssbmod(x,fc,fs,phic);

% Demodulationxr = ssbdemod(y,fc,fs,phic);

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-1.5

-1

-0.5

0

0.5

1

1.5

Time (ms)

Amplit

ude

Vi du ve dieu che SSB

2/10/2012Nguyn c Nhn 133

%% SSB Modulation% Generate sinusoidt = T0:Ts:Tf;x = A*cos(2*pi*f*t+phi);% Modulationy = ssbmod(x,fc,fs,phic);

% Demodulationxr = ssbdemod(y,fc,fs,phic);

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5-1.5

-1

-0.5

0

0.5

1

1.5

Time (ms)

Amplit

ude

Vi du ve dieu che SSB

iu ch tn hiu tng t: iu ch tn s FM:

Trong MATLAB: s dng hm fmmod vfmdemod cho iu ch FM



Ch s iu ch:

rng bng tn:



2/10/2012Nguyn c Nhn 134

rng bng tn:

% Modulationy = pmmod(x,fc,fs,phic);% Demodulationxr = pmdemod(y,fc,fs,phic);

iu ch tn hiu tng t: iu ch pha PM:

Sng mang:

Tn hiu iu ch:

Trong MATLAB s dng cc hm pmmod vpmdemod cho iu ch PM.


Sng mang:

Tn hiu iu ch:


Ch s iu ch:

2/10/2012Nguyn c Nhn 135


Sng mang:

Tn hiu iu ch:


%% Phase Modulationt = T0:Ts:Tf;x = A*cos(2*pi*f*t+phi);% Modulationy = pmmod(x,fc,fs,phic);% Demodulationxr = pmdemod(y,fc,fs,phic);

iu ch tn hiu s: iu ch tuyn tnh:

c biu din bi:

s(t) l tuyn tnh vi bn Cc nh dng iu ch khc nhau c xy dng bng vic chn

cc danh sch alphabet ph hp

Hm p(t) xc nh dng xung u ra tn hiu c iu ch p(t) c th l hm xung vung hoc hm xung sinc


c biu din bi:




2/10/2012Nguyn c Nhn 136


c biu din bi:




iu ch tn hiu s: iu ch pha ASK:

S dng hm pammod v pamdemod trong MATLAB to ra k hiu phctng ng bng gc.

biu din dng sng iu ch c sng mang c th s dng hm ammodtrong iu ch AM vi cc mc c ly mu:




% Signal generatordm = randint(1,1000,4);% PAM modulations = pammod(dm,4);% PAM demodulationr = pamdemod(s,4);

% Data sequenceh = [0 1 0 1];% NRZ modulation[t,y,code]=nrzcode(h,1e6,512);% AM demodulationts = t(2)-t(1); % sampling timefs = 1/ts; % sampling freq.fc = 10e6; % carrier freq.yd = ammod(y,fc,fs); 0 5 10 15 20 25 30 35 40

-1

-0.5

0

0.5

1

Time (ns)

Amplit

ude

Vi du ve dieu che ASK

2/10/2012Nguyn c Nhn 137




% Data sequenceh = [0 1 0 1];% NRZ modulation[t,y,code]=nrzcode(h,1e6,512);% AM demodulationts = t(2)-t(1); % sampling timefs = 1/ts; % sampling freq.fc = 10e6; % carrier freq.yd = ammod(y,fc,fs); 0 5 10 15 20 25 30 35 40

-1

-0.5

0

0.5

1

Time (ns)

Amplit

ude

Vi du ve dieu che ASK

iu ch tn hiu s: iu ch pha PSK:

iu ch M-PSK:


iu ch M-PSK:

BPSK QPSK

B iu ch

B gii iu chTn hiu BPSK:

2/10/2012Nguyn c Nhn 138

Tn hiu BPSK:

Tn hiu QPSK:

Dng sng QPSK:


Trong MATLAB s dng hm pskmodv pskdemod cho iu ch PSK kthp vi modem xy dng objectca b iu ch v gii iu ch:

% Create a random digital messageM = 4; % Alphabet sizex = randint(5000,1,M); % Message generator% Use QPSK modulation to produce y.h = modem.pskmod(M,pi/4);h.symbolorder = 'gray';y = modulate(h,x);

% Transmit signal through an AWGN channel.ynoisy = awgn(y,15,'measured');

% Create scatter plot from noisy data.h = scatterplot(ynoisy,1,0,'xb');hold on;scatterplot(y,1,0,'or',h);% Demodulate ynoisy to recover the message.h = modem.pskdemod(M,pi/4);h.symbolorder = 'gray';z=demodulate(h,ynoisy);


Trong MATLAB s dng hm pskmodv pskdemod cho iu ch PSK kthp vi modem xy dng objectca b iu ch v gii iu ch:




-1 -0.5 0 0.5 1

-1

-0.5

0

0.5

1

Quad

rature

In-Phase

Scatter plot

-1.5 -1 -0.5 0 0.5 1 1.5-1.5

-1

-0.5

0

0.5

1

1.5

Quad

rature

In-Phase

Scatter plot

/4 - QPSK

2/10/2012Nguyn c Nhn 139




-1 -0.5 0 0.5 1

-1

-0.5

0

0.5

1

Quad

rature

In-Phase

Scatter plot

-1.5 -1 -0.5 0 0.5 1 1.5-1.5

-1

-0.5

0

0.5

1

1.5

Quad

rature

In-Phase

Scatter plot

QPSK


iu ch PSK m ha vi sai: s dng hm dpskmod v dpskdemod


iu ch PSK m ha vi sai: s dng hm dpskmod v dpskdemod

% Create a random digital messageM = 2; % Alphabet sizex = randint(5000,1,M); % Message% Use DPSK modulation to produce y.y = dpskmod(x,M);

% Demodulate to recover the message.z = dpskdemod(y,M);

-1.5 -1 -0.5 0 0.5 1 1.5-1.5

-1

-0.5

0

0.5

1

1.5

Quad

rature

In-Phase

Scatter plot

x = 0 1 1 0 0 0 1 0 0 0 0 1 0 1 1 1 0 1 0 1

0 2 4 6 8 10 12 14 16 18 2000.51

1.52

Symbol index

Amplit

ude

Bieu dien bien do cua tin hieu dieu che DPSK

0 2 4 6 8 10 12 14 16 18 20-101234

Symbol index

Phas

e (rad

)


2/10/2012Nguyn c Nhn 140

% Create a random digital messageM = 2; % Alphabet sizex = randint(5000,1,M); % Message% Use DPSK modulation to produce y.y = dpskmod(x,M);

% Demodulate to recover the message.z = dpskdemod(y,M);

-1.5 -1 -0.5 0 0.5 1 1.5-1.5

-1

-0.5

0

0.5

1

1.5

Quad

rature

In-Phase

Scatter plot

0 2 4 6 8 10 12 14 16 18 2000.51

1.52

Symbol index

Amplit

ude


0 2 4 6 8 10 12 14 16 18 20-101234

Symbol index

Phas

e (rad

)


iu ch tn hiu s: iu ch QAM: kt hp gia ASK v PSK

iu ch tn hiu s: iu ch QAM: kt hp gia ASK v PSK

B iu ch B gii iu ch

2/10/2012Nguyn c Nhn 141

Rectangular QAM Circular QAM

iu ch tn hiu s: iu ch QAM:

S dng hm qammod v qamdemod trong MATLAB

iu ch tn hiu s: iu ch QAM:

S dng hm qammod v qamdemod trong MATLAB

close all;% Create a random digital messageM = 16; % Alphabet sizex = randint(5000,1,M);

% Use 16-QAM modulation to produce y.y=modulate(modem.qammod(M),x);


% Create scatter plot from noisy data.h = scatterplot(ynoisy,1,0,'xb');hold on;scatterplot(y,1,0,'or',h); hold off;

0 2 4 6 8 10 12 14 16 18 20

2

3

4

Symbol index

Amplit

ude

Bieu dien bien do cua tin hieu dieu che 16-QAM

5 10 15 20-2

0

2

Symbol index

Phas

e (rad

)


-4 -2 0 2 4

-4

-3

-2

-1

0

1

2

3

4

Quad

rature

In-Phase

Scatter plot

2/10/2012Nguyn c Nhn 142

close all;% Create a random digital messageM = 16; % Alphabet sizex = randint(5000,1,M);

% Use 16-QAM modulation to produce y.y=modulate(modem.qammod(M),x);


% Create scatter plot from noisy data.h = scatterplot(ynoisy,1,0,'xb');hold on;scatterplot(y,1,0,'or',h); hold off;

0 2 4 6 8 10 12 14 16 18 20

2

3

4

Symbol index

Amplit

ude


5 10 15 20-2

0

2

Symbol index

Phas

e (rad

)


iu ch tn hiu s: iu ch FSK:

iu ch FSK

iu ch FSK pha lin tc (CPFSK)

iu ch MSK: mt kiu CPFSK


iu ch FSK

iu ch FSK pha lin tc (CPFSK)

iu ch MSK: mt kiu CPFSK

2/10/2012Nguyn c Nhn 143

S dng hm fskmod v fskdemod cho iu ch FSK

S dng hm mskmod v fskdemod cho iu ch MSK


% Chuong trinh vi du ve MSKclose all;% ParametersNs = 8; % number of samples per symbol

x = randint(1000,1); % Random signal

% Use MSK modulation to produce y.y = mskmod(x,Ns,[],pi/2);

h = scatterplot(y,1,0,'xb');hold on;scatterplot(y,Ns,0,'or',h); hold off;

% Transmit signal through an AWGN channel.yn = awgn(y,25,'measured');

% Plot eyediagrameyediagram(yn,16);

-0.5 0 0.5-1.5-1

-0.50

0.51

1.5

Time

Amplit

ude

Eye Diagram for In-Phase Signal

-0.5 0 0.5-1.5-1

-0.50

0.51

1.5

Time

Amplit

ude

Eye Diagram for Quadrature Signal







-1 -0.5 0 0.5 1-1

-0.8-0.6-0.4-0.2

00.20.40.60.81

Quad

rature

In-Phase

Scatter plot

-0.5 0 0.5-1.5-1

-0.50

0.51

1.5

Time

Amplit

ude


-0.5 0 0.5-1.5-1

-0.50

0.51

1.5

Time

Amplit

ude


2/10/2012Nguyn c Nhn 144







-1 -0.5 0 0.5 1-1

-0.8-0.6-0.4-0.2

00.20.40.60.81

Quad

rature

In-Phase

Scatter plot

-0.5 0 0.5-1.5-1

-0.50

0.51

1.5

Time

Amplit

ude


-0.5 0 0.5-1.5-1

-0.50

0.51

1.5

Time

Amplit

ude


To dng ph: Mt ph cng sut SY(f) ca tn hiu ra y(t):

Trong SX(f) l PSD ca tn hiu vo x(t) v H(f) l hm truyn ca h thng (hay b lc)

Bng vic la chn cn thn H(f) tng cng hoc kh ccthnh phn ph chn lc ca tn hiu vo.

Khi SX(f) v H(f) xc nh xc nh c SY(f) Ngc li: bit SY(f) l PSD u ra mong mun ca PSD u

vo SX(f) xc nh c H(f) V d b lc butterworth:

2( ) ( ) ( )Y XS f S f H f






2( ) ( ) ( )Y XS f S f H f

2/10/2012Nguyn c Nhn 145






22

1( )1 ( / ) nb

H f

n bc ca b lc

b rng bng tn 3 dB

To dng ph: Tnh ton PSD ca mt tn hiu:

function [f,Pf] = spectrocal(t,x)% Vi du chuong trinh tinh toan spectrum% t - time vector% x - input samples% f - frequency vector% Pf - estimated PSD of x% written by Nguyen Duc Nhan

Ns = length(x);Ts = t(2)-t(1);

f = (-Ns/2:Ns/2-1)/(Ns*Ts); % freq. vectorPf = fft(x,Ns);Pf = fftshift(Pf)/Ns;Pf = abs(Pf).^2;

0 50 100 150 200 2500

0.2

0.4

0.6

0.8

1

Sample index

Amplit

ude




0 50 100 150 200 2500

0.2

0.4

0.6

0.8

1

Sample index

Amplit

ude

-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.510-8

10-6

10-4

10-2

Frequency

PSD

2/10/2012Nguyn c Nhn 146




-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.510-8

10-6

10-4

10-2

Frequency

PSD >> t = 0:255;

>> x = zeros(1,length(t));>> x(1:20) = 1;>> plot(t,x);grid;>> [f,Xf] = spectrocal(t,x);>> semilogy(f,Xf);grid;

To dng ph: Tnh ton PSD ca mt tn hiu:

function y = butterwflt(x,n,B,Ts)% Function bo loc butterworth% B - filter bandwidth% Ts - sampling time% n - filter order% y - filtered outputNs = length(x);% Frequency domainf = [0:Ns/2-1 -Ns/2:-1]/(Ns*Ts);Xf = fft(x);Hf = 1./(1+(f./B).^(2*n)); % transfer func.Yf = Xf.*Hf;% Convert into time domainy = ifft(Yf);

0 50 100 150 200 2500

0.2

0.4

0.6

0.8

1

1.2

Sample index

Amplit

ude


-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.510-8

10-6

10-4

10-2

Frequency

PSD

0 50 100 150 200 2500

0.2

0.4

0.6

0.8

1

1.2

Sample index

Amplit

ude

2/10/2012Nguyn c Nhn 147


-0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.510-8

10-6

10-4

10-2

Frequency

PSD

>> y = butterwflt(x,1,0.2,1);>> [f,Xf]=spectrocal(t,y);>> semilogy(f,Xf); grid;>> figure(2);>> plot(t,x,t,y); grid;

To dng xung: Mi xung n dng sng trong cc h thng truyn dn s

thng c yu cu tha mn 2 iu kin quan trng v: Bng thng

Chuyn tip qua 0 (zero crossings)

Nyquist chng minh rng: mt xung p(t) c zero crossing michu k Tb = 1/Rb nu khai trin P(f) p ng cc rng buc sau:

Mt h P(f) p ng tiu chun Nyquist l h raised cosine:






( )b bk

P f kR T

2bf R

2/10/2012Nguyn c Nhn 148






2 2,

( ) cos ,4

0,

b

b

Rb

T

P f T f

2bf R 2 2b bR f R

2bf R Trong l tham s bng tn tri (h s rolloff) v P(f) b gii hn bng ti +(Rb/2).

To dng xung: p ng xung kim ca h raised cosine:

2sincos2( )

1 4b

b

R ttp tR tt

2sincos2( )

1 4b

b

R ttp tR tt

0 0.2 0.4 0.6 0.8 1 1.20

0.2

0.4

0.6

0.8

1

f/Tb

P(f)

0 0.5 1 1.5 2 2.5 3-0.4-0.2

00.20.40.60.81

t/Tb

p(t)

0

0.25

2/10/2012Nguyn c Nhn 149

0 0.2 0.4 0.6 0.8 1 1.20

0.2

0.4

0.6

0.8

1

f/Tb

P(f)

0 0.5 1 1.5 2 2.5 3-0.4-0.2

00.20.40.60.81

t/Tb

p(t)

0.5

To dng xung: V d b lc raised cosine: function y = raisedcosflt(x,Rb,Ts,beta)

% Function bo loc raised cosine% x - input samples% Rb - filter bandwidth% Ts - sampling time% beta - rolloff factor% y - filtered outputNs = length(x);Tb = 1/Rb;beta = beta*Rb;% Frequency domainf = [0:Ns/2-1 -Ns/2:-1]/(Ns*Ts);Xf = fft(x);Yf = zeros(size(Xf));ind = (abs(f)(Rb/2+beta));Yf(ind) = Xf(ind).*0;% Convert into time domainy = ifft(Yf)./Tb;

0 0.5 1 1.5 2 2.5 3 3.5 4x 10-6

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Time (s)

Amplit

ude

function y = raisedcosflt(x,Rb,Ts,beta)% Function bo loc raised cosine% x - input samples% Rb - filter bandwidth% Ts - sampling time% beta - rolloff factor% y - filtered outputNs = length(x);Tb = 1/Rb;beta = beta*Rb;% Frequency domainf = [0:Ns/2-1 -Ns/2:-1]/(Ns*Ts);Xf = fft(x);Yf = zeros(size(Xf));ind = (abs(f)(Rb/2+beta));Yf(ind) = Xf(ind).*0;% Convert into time domainy = ifft(Yf)./Tb;

0 0.5 1 1.5 2 2.5 3 3.5 4x 10-6

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Time (s)

Amplit

ude

0 0.5 1 1.5 2 2.5 3 3.5 4x 10-6

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Time (s)

Amplit

ude

0.5

2/10/2012Nguyn c Nhn 150

function y = raisedcosflt(x,Rb,Ts,beta)% Function bo loc raised cosine% x - input samples% Rb - filter bandwidth% Ts - sampling time% beta - rolloff factor% y - filtered outputNs = length(x);Tb = 1/Rb;beta = beta*Rb;% Frequency domainf = [0:Ns/2-1 -Ns/2:-1]/(Ns*Ts);Xf = fft(x);Yf = zeros(size(Xf));ind = (abs(f)(Rb/2+beta));Yf(ind) = Xf(ind).*0;% Convert into time domainy = ifft(Yf)./Tb;

0 0.5 1 1.5 2 2.5 3 3.5 4x 10-6

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

Time (s)

Amplit

ude 0.25

To dng xung: Trong MATLAB c th s dng cc hm cho qu trnh lc trong

signal processing toolbox:

V d s dng hm filter:

Mt s kiu b lc sn c: B lc butterworth: [b,a] = butter(n,Wn)

B lc bessel: [b,a] = besself(n,Wo)

B lc chebyshev: [b,a] = cheby1(n,R,Wp) v [b,a] = cheby2(n,R,Wst)

B lc raised cosine: y = rcosflt(x,Fd,Fs)








y = filter(b,a,x) Trong a, b l cc vect cha cc h s ca b lc

y(n) = b(1)*x(n) + b(2)*x(n-1) + ... + b(nb+1)*x(n-nb)- a(2)*y(n-1) - ... - a(na+1)*y(n-na)

2/10/2012Nguyn c Nhn 151








B lc phi hp (matched filters): Xt bi ton thu c hoc khng thu c mt xung c dng

p(t) t tn hiu quan st y(t):

X l y(t) quyt nh c hay khng c p(t) trong khong chu k T.

X l y(t) thu c:

Xc sut li trung bnh nh nht khi b lc c hm truyn:

p ng xung: p ng xung phi hp vi p(t).

( ) ( )( ) or

( )

p t N ty t

N t




X l y(t) thu c:



( ) ( )( ) or

( )

p t N ty t

N t

N(t) nhiu cng c trung bnh 0.

0( ) ( )Tz y h T d

2/10/2012Nguyn c Nhn 152




X l y(t) thu c:



*( ) ( ) exp( 2 )H f KP f j fT( ) ( )h t p T t

0 0( ) ( ) ( ) ( )T Tz y h T d y p d

B lc phi hp (matched filters): B lc phi hp cho mt tn hiu iu ch tuyn tnh s dng

dng xung p(t):

Khi p(t) c dng xung vung n v z l tch phn ca tn hiuu vo.

Qu trnh ly tch phn c bt u thc hin ti u mikhong chu k b lc integrate-and-dump (I&D).


dng xung p(t):




dng xung p(t):



2/10/2012Nguyn c Nhn 153

Qu trnh ng b trong m phng: Xem xt s nh hng ca ng b n hiu nng ca h

thng.

C cc cch tip cn khc nhau: Dng cu trc

Dng m t thng k

Ti b thu, qu trnh ng b bao gm:

Khi phc sng mang

Khi phc ng h (tn hiu nh thi)

Clock@


thng.


Dng m t thng k


Khi phc sng mang


S(t)N(t)

C(t)

d(t)LPF Decision ( , )eP

Clock@

( , )eP GeneralsystemS(t)

N(t)

2/10/2012Nguyn c Nhn 154


thng.


Dng m t thng k


Khi phc sng mang


M phng mch vng kha pha PLL: PLL c m t bi ptr. vi phn phi tuyn

B lc vng bc 2:

M phng mch vng kha pha PLL: PLL c m t bi ptr. vi phn phi tuyn

B lc vng bc 2:

VCOK2 (rad/s)/volt

Loop filterK1F(s)

32 sin 2 ( )cK f t t

2 cos 2 ( ) ( )cA f t t N t

( )t ( )t ( )e t

S khi PLL c bn

2/10/2012Nguyn c Nhn 155

K1K3F(s)

sinA( )t

2Ks

( )t

( )t ( )e t

( )v tM t tng ng trong min pha

M phng mch vng kha pha PLL: Hm truyn b lc vng:

PLL m rng:

t cc hng s:

2

1 1

1( ) sF ss

110

Vi

B lc th ng


PLL m rng:

t cc hng s:

2

1 1

1( ) sF ss

110

1 3 1 2( ) ( )[ ( ) ( )]v t K K y t y t 1 2 3 1 2

( ) ( )[ ( ) ( )]t K K K y t y t 1 2 3 1 2

( ) ( ) ( ) ( ) ( )[ ( ) ( )]t t t t K K K y t y t 1 2 3 1 2( ) sin ( ) ( )[ ( ) ( )]e t A t K K K y t y t

1 1( ) ( ) ( ) ( )y t e t y t

ViB lc th ngB lc tch cc

2/10/2012Nguyn c Nhn 156


PLL m rng:

t cc hng s:

1 1( ) ( ) ( ) ( )y t e t y t

1 2 3( ) sin ( ) ( ) ( ) ( )y t A t c y t c y t c y t 1 2 3 2

11

K K Kc

1 2 321

K K Kc

13

1

c

31. Vit chng trnh MATLAB to chui bit ngu nhin phn b u c di 128 bit. Sau thc hin chuyn i chui bit ny thnh ccgi tr thp phn trong di t [0,15]. Gi : Chuyn i vector hng thnh ma trn mx4, sau dng hm bi2de chuyn

i sang dng thp phn.32. Xy dng cc function nn v gii nn tn hiu theo lut A c dng

cu trc sau:function [y,amax] = alaw(x,A) v function x = invalaw(y,A)

33. Vit chng trnh m ha tn hiu x = 2cos(4t) ti tn s ly mu fs =20 Hz s dng qu trnh PCM theo lut A vi 8 mc lng t. Hy xcinh t m u ra ca 5 mu u tin. V biu din tn hiu gc banu, tn hiu c ly mu v tn hiu c lng t ha trn cngmt hnh. (S dng cc function xy dng ca bi tp trn)

34. Xy dng function chuyn i chui bit d liu u vo thnh mng RZ n cc.

S dng function ny m ha RZ v biu din dng sng ca chuibit [0 1 1 0 1 0 1 0] ti tc 1 Mbit/s.







2/10/2012Nguyn c Nhn 157







35. Vit chng trnh MATLAB xc nh cc t m u ra ca b m hakhi c tc 4/7. Bit ma trn to m c dng:

36. Vit function to chui xung tam gic u ra. Bit trong mt chu kdng xung c biu din bi hm sau:

37. Cho tn hiu tng t c m t bi cng thc sau:

Vit chng trnh thc hin iu ch bin tn hiu bng sng mangfc = 300 Hz. V dng sng tn hiu bn tin ban u v tn hiu ciu ch.Gii iu ch tn hiu trn bng k thut ph hp v v dng sng tnhiu sau khi c gii iu ch.

1 0 0 0 1 1 10 1 0 0 1 1 00 0 1 0 1 0 10 0 0 1 0 0 1





1 0 0 0 1 1 10 1 0 0 1 1 00 0 1 0 1 0 10 0 0 1 0 0 1

w w1 ( ) ,( )0,

t T Tp t

0 pt T Vi Tw = Tp/2

Tp chu k xungt khc

( ) 2cos(20 + /4)+cos(30 )s t t t

2/10/2012Nguyn c Nhn 158





( ) 2cos(20 + /4)+cos(30 )s t t t

38. To chui bit ngu nhin c di 5000 bits. Chuyn i chui bitny thnh dng sng m ng NRZ lng cc ti tc 100Mbit/s. S dng b lc raised cosine c rng bng tn 300 MHzv h s rolloff bng 0.5 lc chui tn hiu NRZ ny. V biudin dng sng tn hiu trn 10 chu k bit trc v sau khi lc tnhiu. V biu mt ca tn hiu sau khi lc trn ca s 2 chu kbit. (S dng hm eyediagram v mu mt).

39. Tng t bi tp 38, s dng b lc butterworth c tn s ctkhong 250 MHz lc tn hiu. (S dng cc hm butter v filtertrong signal processing toolbox).

40. To chui k t ngu nhin c di 1000 k t thc hin iubin BPSK. Hy vit chng trnh biu din dng sng ng baophc ca tn hiu iu bin BPSK ti tc 10 Mb/s bi cc xungraised cosine c m t bi hm sau:

V dng ph ca tn hiu c iu bin.




V dng ph ca tn hiu c iu bin.2/10/2012Nguyn c Nhn 159




V dng ph ca tn hiu c iu bin.

2( ) 1 os tp t cT

0 t T

mophonghttt_ch4

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