raisecos.m

北邮《通信原理基于Matlab的计算机仿真》书的源码 m文件 好不容易弄来的

%升余弦滚降系统示意图
clear all;
close all;
Ts=1;
N_sample = 17;
dt = Ts/N_sample;
df = 1.0/(20.0*Ts);

t = -10*Ts:dt:10*Ts;
f = -2/Ts:df:2/Ts;

alpha = [0,0.5,1];

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('f/Ts');ylabel('升余弦滚降频谱');
figure(2)
plot(t,xt);
axis([-10 10 -0.5 1.1]);xlabel('t/Ts');ylabel('升余弦滚降波形');