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標題: 通信原理實驗一源代碼及圖 [打印本頁]

作者: liuqq 時間: 2015-5-19 20:37
標題: 通信原理實驗一源代碼及圖

t0=0;

ts=0.000001;

t1=0.004;

fs=1/ts;

df=0.25;

t=t0:ts:t1;

%fs=1000000;

N=4000;

w=(0:N)*fs/(N+1)-fs/2;

m=cos(2*pi*2000*t);

figure

plot(w,m)

title('信號');

N=4000;

w=(0:N)*fs/(N+1)-fs/2;

Y1=fftshift(abs(fft(m)));

figure(2)

plot(w,Y1)

title('信號頻譜');

axis([-4000,40000,0,2000])

c=cos(2*pi*20000*t);

figure(3)

plot(w,c)

title('載波');

Y2=fftshift(abs(fft(c)));

figure(4)

plot(w,Y2)

title('載波頻譜');

axis([-40000,40000,0,100])

s=m.*c;

figure(5)

plot(w,s)

title('已調信號');

Y3=fftshift(abs(fft(s)));

figure(6)

plot(w,Y3)

title('已調信號頻譜');

axis([-4000,4000,0,2000])

y3= awgn(s,3);

subplot(4,1,1);

plot(t,y3);

title('加噪聲后的已調信號');

fsamp = 1e6; %采樣頻率為1MHz

fcuts = [16000 17500 22500 24000];

mags = [0 1 0];

devs = [0.05 0.01 0.05];

[n,Wn,beta,ftype] = kaiserord(fcuts,mags,devs,fsamp);

hh = fir1(n,Wn,ftype,kaiser(n+1,beta),'noscale');

s1 = fftfilt(hh,y3);

subplot(4,1,2);

plot(t,s1);

title('經帶通濾波后的已調制信號');

s2=c.*s1;

subplot(4,1,3);

plot(t,s2);

title('經乘法器后的已調制信號');

fsamp = 1e6; %采樣頻率為1MHz

fcuts = [3000 20000]; %通帶截止頻率為3000Hz，阻帶截止頻率為20000Hz

mags = [1 0];

devs = [0.01 0.05]; % 通帶波動1%，阻帶波動5%

[n,Wn,beta,ftype] = kaiserord(fcuts,mags,devs,fsamp);

hh2 = fir1(n,Wn,ftype,kaiser(n+1,beta),'noscale');

m0 = fftfilt(hh2,s2);

subplot(4,1,4);

plot(t,m0);

title('經低通濾波后的最后的解調調制信號');

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