fig5_15.m

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

%	Fig5-15
%	1st/3rd/5th Order IIR bandpass Digital Filters
%	Butterworth - Bilinear - LP-> BP
%       JST June 2001

clear
clf

wc = [ 0.1 0.3];  % normalised frequency
wc = 2*wc;       % matlab scale
M = 256; 	 %no. of frequency samples

ii = 1;
[b1,a1] = butter(ii,wc);
[h1,w] = freqz(b1,a1,M);
h1(1) = 1e-100;
h1(256) = 1e-100;
mag = 20*log10(abs(h1));
f = 10000*w/pi/2;

plot(f,mag,'r-');
axis ( [ 0 5000 -50 0 ]);
grid
axis('square')
xlabel('frequency (Hz)'),ylabel('gain (dB)');


fprintf(1,'Figure 5.15: order 1 Bandpass filter\n')
fprintf(1,'           : press return for orders 2 to 5\n')
pause

for ii=2:5

	[b1,a1] = butter(ii,wc);
	[h1,w] = freqz(b1,a1,M);
	h1(1) = 1e-100;
	h1(256) = 1e-100;
	mag = 20*log10(abs(h1));

	hold on;
	plot(f,mag,'r-');
	hold off;
	pause(1);
end