rcosine_filter.m

（Root Raised Cosine Filter）根升余弦滤波器的MATLAB代码

close all;
clear all;

Fd= 1; %输入信号的采样率
Fs = 8;  %输出信号的采样率
Delay = 3;  %滤波器的群时延
R = 0.5;   %滚降因子
[yf,tf] = rcosine(Fd,Fs,'fir',R,Delay);  %yf=b,tf=a;
%plot(yf)
freqz(yf,tf,512);
grid
xlabel('Time')
ylabel('Amplitude');
% impz(rrcfilter,1); % 另外一种画冲激响应的方法
x=rand(100,1);  %产生随机信号
xt=zeros(1,800);  %对输入信号后面补零
xt(1:8:end)=x;
y=filter(yf,tf,xt);  %经过升余弦滤波器
yt=y((length(yf)+1)/2:8:end);    %下采样，去除滤波器的抽头时延
%figure;stem(x(1:40),'.');
%hold on;stem(yt(1:40),'r');
%hold on;stem(yt(1:40),'r');
x_f=fft(x);
xt_f=fft(xt);
y_f=fft(y);
yt_f=fft(yt);
figure;
%stem(xt_f,'.');
%hold on;stem(y_f,'r');
subplot(211);
plot(abs(xt_f));
subplot(212);
plot(abs(y_f));