图4-2-14低通滤波器的增益特性比较.txt

典型窗函数的归一化幅频对数特性

%不同窗函数设计低通滤波器0924.TXT
%Nomalized frequency (/pi)

%Magnitude
clear;
format long									%变量采样字长为双精度
wp=0.25;
M=25;
N=2*M+1;


win=boxcar(N);								%设定窗函数，矩形窗
b=fir1(M*2,wp,win);							  %数字滤波器设计
[h,w]=freqz(b,1,1000);
hold on;
plot(w/pi,20*log(abs(h)));




win=hamming(N);								%设定窗函数，矩形窗
b=fir1(M*2,wp,win);							  %数字滤波器设计
[h,w]=freqz(b,1,1000);
hold on;
plot(w/pi,20*log(abs(h)));

win=blackman(N);								%设定窗函数，矩形窗
b=fir1(M*2,wp,win);							  %数字滤波器设计
[h,w]=freqz(b,1,1000);
hold on;
plot(w/pi,20*log(abs(h)));
						%设定窗函数，巴特利窗
						
						
						win_tri= triang(N);								%设定窗函数，矩形窗
b=fir1(M*2,wp,win);							  %数字滤波器设计
[h,w]=freqz(b,1,1000);
hold on;
plot(w/pi,20*log(abs(h)));

win=hanning(N);								%设定窗函数，矩形窗
b=fir1(M*2,wp,win);							  %数字滤波器设计
[h,w]=freqz(b,1,1000);
hold on;
plot(w/pi,20*log(abs(h)));