信息与通信数字信号处理课设报告Word下载.docx
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Vm0=2;
ka=0.25;
n=-t0/2:
1/fs:
t0/2;
w=0:
1/(N-1):
1;
x=5*cos(200*pi*n);
%调制信号
y=Vm0*(1+ka*x/Vm0).*cos(2*pi*fc*n);
h=Vm0*cos(2*pi*fc*n);
figure
(1)
subplot(2,2,1)
plot(n,x)
title('
调制信号'
);
subplot(2,2,2)
plot(n,y)
已调波信号'
subplot(2,2,3)
plot(n,h)
载波信号'
axis([-0.01,0.01,-5,5]);
H=fft(h);
subplot(2,2,4)
plot(w,abs(H))
载波频谱'
axis([0,1,0,500]);
N=length(x);
X=fft(x);
Y=fft(y);
2*pi/(N-1):
2*pi;
figure
(2)
subplot(2,1,1)
plot(w,abs(X))
axis([0,1,0,3000]);
调制信号频谱'
subplot(2,1,2)
plot(w,abs(Y))
axis([0,1,0,1200]);
已调波信号频谱'
y1=y-2*cos(800*pi*n);
y2=Vm0*y1.*cos(2*pi*fc*n);
wp=40/N*pi;
ws=60/N*pi;
Rp=1;
As=15;
T=1;
OmegaP=wp/T;
OmegaS=ws/T;
[cs,ds]=afd_butt(OmegaP,OmegaS,Rp,As);
[b,a]=imp_invr(cs,ds,T);
y=filter(b,a,y2);
figure(3)
解调波'
axis([0,1,0,1000]);
解调信号频谱'
x=3*cos(200*pi*n)-2*cos(250*pi*n);
N=length(X);
axis([0,pi/4,0,3000]);
axis([pi/6,pi/4,0,1200]);
y1=y-2*cos(2000*pi*n);
axis([0,pi/6,0,1000]);
%抑制载波双边带调制y=amod(x,t,fs,t0,fc,Vm0,ka)要求fs>
%x调制信号,t0采样区间,fs采样频率,
y=Vm0*x.*cos(2*pi*fc*n);
axis([pi/6,pi/4,0,2000]);
axis([0,pi/6,0,3000]);
axis([0,pi/6,0,2000]);
%单边带调制y=amod(x,t,fs,t0,fc,Vm0,ka)要求fs>
%x调制信号,t0采样区间,fs采样频率,
N=length(n);
x2=hilbert(x1,N);
y=(Vm0*x1.*cos(2*pi*fc*n)-Vm0*x2.*sin(2*pi*fc*n))/2;
plot(n,x1)
X=fft(x1);
axis([pi/6,pi/4,0,3000]);
title(‘解调波频谱’)
x1=3*cos(200*pi*n)-2*cos(250*pi*n);