lowpassfilter.m

用矩形窗设计线性相位FIR低通滤波器,给了源代码

%用矩形窗设计线性相位FIR低通滤波器(wc=pi/4 N=21)
N=21;wc=pi/4;
bandwidth=4*pi/N;
n=[0:1:N-1];
hdn=ideal_lp(wc,N);
win_boxcar=boxcar(N)';
hn=hdn.*win_boxcar;
[db,mag,pha,w]=myfreqz(hn,1);
subplot(2,2,1);stem(n,hdn);title('理想冲激响应');
axis([0,N-1,-0.1,0.3]);xlabel('n');ylabel('hdn(n)');
subplot(2,2,2);stem(n,win_boxcar);title('boxcar窗');
axis([0,N-1,0,1.1]);xlabel('n');ylabel('w(n)');
subplot(2,2,3);stem(n,hn);title('设计出的滤波器冲激响应');
axis([0,N-1,-0.1,0.3]);xlabel('n');ylabel('h(n)');
subplot(2,2,4);plot(w/pi,db);title('幅频响应－dB');grid
axis([0,1,-100,10]);xlabel('w/pi');ylabel('dB');