clear fs=500; t=0:pi/200:pi/1.5; x=sin(t)+sin(3*t)+1; x_=x'; wp=1.5/500;%截止频率,以下的频率可以通过 ws=5/500;%被滤除 Rp=1; As=10; subplot(311); plot(t,x); title('sin(t)+sin(5*t)+4'); %N滤波阶数,Wn代表滤波器的截止频率 [N,wc]=buttord(wp,ws,Rp,As); [B,A]=butter(N,wc,'low'); [H,W]=freqz(B,A); y=filter(B,A,x); subplot(312); test=sin(t); plot(t,test); %plot(W,abs(H)); title('y=sin(x)'); subplot(313); plot(t,y) title('低通滤波');