fig5_14.m

来自「数字信号处理Matlab演示文件,其中各个文件加放置了不同的matlab子文件」· M 代码 · 共 50 行

%	Fig5-14
%	4th to 10th Order IIR Digital Filters
%	Butterworth - Bilinear
%	BM August 1996; Revised July 98
%       JST updated May 2001

clear
clf

wc = 0.1;	%normalised frequency
wc = wc*2;	%matlab scale
M = 256;	%no. of frequency samples

ii = 2;
[b1,a1] = butter(ii,wc);
[h1,w] = freqz(b1,a1,M);
h1(M) = 1e-100;
mag = 20*log10(abs(h1));
f = w/pi/2;

plot(f,mag,'r-');
%lm1 = line('Xdata',f,'Ydata',mag,'Linestyle','-','Color','y','Erasemode','Xor');
%lm2 = line('Xdata',f,'Ydata',mag,'Linestyle','-','Color','r','Erasemode','None');
axis ( [ 0 0.5 -100 0 ]);
grid
axis('square')
xlabel('frequency (rad/s)'),ylabel('gain (dB)');


fprintf(1,'Figure 5.14: order 2 Butterworth filter\n')
fprintf(1,'           : press return for orders 4 to 10\n')
pause

for ii=4:2:10

	[b1,a1] = butter(ii,wc);
	[h1,w] = freqz(b1,a1,M);
	h1(M)=1e-100;
	mag = 20*log10(abs(h1));

	hold on;
	plot(f,mag,'r-');
	hold off;
%	set(lm1,'Xdata',f,'Ydata',mag);
%	set(lm2,'Xdata',f,'Ydata',mag);
	
	pause(1);
end