>> %design a Butterworth filter and suppose the sampling frequency is 4000HZ>> fs=4000;>> [n,Wn]=buttord(1000/(fs/2),1200/(fs/2),1,100);>> [b,a]=butter(n,Wn);>> freqz(b,a,512,fs);就帮你用了最简单的巴特沃兹滤波器。