clear all; 
close all; 
t1=5; 
ts=t1/4; 
N=31; 
df=1.0/(2*ts); 
dt=ts/N; 
t=-10*ts:dt:10*ts; 
f=-2/ts:df:2/ts; 
alpha=[0.1,0.5,1]; 
for n=1:length(alpha) 
for k=1:length(f) 
if abs(f(k))>0.5*(1+alpha(n))/ts 
Xf(n,k)=0; 
elseif abs(f(k))<0.5(1-alpha(n))/ts 
Xf(n,k)=ts; 
else 
Xf(n,k)=0.5*ts*(1+cos(pi*ts/(alpha(n)+eps)*(abs(f(k))-0.5*(1-alpha(n))/ts))); 
end 
end 
xt(n,:)=sinc(t/ts).*(cos(alpha(n)*pi*t/ts))./(1-4*alpha(n)^2*t.^2/ts^2+eps); 
end 
figure(1) 
plot(f,Xf); 
axis([-1 1 0 1.2]);xlabel('升余弦滾降頻譜'); 
figure(2) 
plot(t,xt); 
axis([-10 10 -0.5 1.1]);ylabel('生余弦滾降波形')