filter.txt

低通滤波器 提供1种滤波器

function Hz_ejw=FIR_DF_HM(U1,U2,T,sum)
wp=U1*T;ws=U2*T;
kuan=ws-wp;
M=sum;
n=[0:1:M-1];
wc=(ws+wp)/2;
hd=H_D(wc,M);
window=hamming_m(M);
h_z=hd.*window;
Hz_ejw=DFT(h_z);
k=1:sum;w=(2*pi/sum)*k;
figure(1); subplot(223)
plot(w,abs(Hz_ejw));grid on
axis([2*pi/sum,pi,-0.2,1.2*max(abs(Hz_ejw))]);
title('海明窗函数低通滤波器')
function hd=H_D(wc,N)
M=(N-1)/2;
for k=-M:M
if k==0
hd(k+M+1)=wc/pi;
else
hd(k+M+1)=sin(wc*k)/(pi*k);
end
end
function wn=hamming_m(M)
n=0:M-1;
wn(n+1)=0.54-0.46*cos((2*pi*n)/(M-1));

function Xk=DFT(xn)
% 离散傅立叶变换,xn为原序列,Xk为DFT变换后的序列
N=length(xn);
n=0:N-1;
k=0:N-1;
WN=exp(-j*2*pi/N);
nk=n'*k;
WNnk=WN.^nk;
Xk=xn*WNnk;