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% MATLAB script for Illustrative Problem 5.1.  
df=0.01; 
fs=10; 
ts=1/fs; 
t=[-5:ts:5]; 
x1=zeros(size(t)); 
x1(41:51)=t(41:51)+1; 
x1(52:61)=ones(size(x1(52:61))); 
x2=zeros(size(t)); 
x2(51:71)=x1(41:61); 
[X1,x11,df1]=fftseq(x1,ts,df); 
[X2,x21,df2]=fftseq(x2,ts,df); 
X11=X1/fs; 
X21=X2/fs; 
f=[0:df1:df1*(length(x11)-1)]-fs/2; 
plot(f,fftshift(abs(X11))) 
figure 
plot(f(500:525),fftshift(angle(X11(500:525))),f(500:525),fftshift(angle(X21(500:525))),'--')