通信原理实验一源代码及图 -

标题: 通信原理实验一源代码及图 [打印本页]

作者: liuqq 时间: 2015-5-19 20:37
标题: 通信原理实验一源代码及图

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('信号');

N=4000;

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

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

figure(2)

plot(w,Y1)

title('信号频谱');

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

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

figure(3)

plot(w,c)

title('载波');

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

figure(4)

plot(w,Y2)

title('载波频谱');

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

s=m.*c;

figure(5)

plot(w,s)

title('已调信号');

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

figure(6)

plot(w,Y3)

title('已调信号频谱');

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

y3= awgn(s,3);

subplot(4,1,1);

plot(t,y3);

title('加噪声后的已调信号');

fsamp = 1e6; %采样频率为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('经带通滤波后的已调制信号');

s2=c.*s1;

subplot(4,1,3);

plot(t,s2);

title('经乘法器后的已调制信号');

fsamp = 1e6; %采样频率为1MHz

fcuts = [3000 20000]; %通带截止频率为3000Hz，阻带截止频率为20000Hz

mags = [1 0];

devs = [0.01 0.05]; % 通带波动1%，阻带波动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('经低通滤波后的最后的解调调制信号');

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