fig5_4.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

%	Figure 5.4(a) & (b)
%	analogue Chebyshev filters
%	 
%
%	BM
%	June 98

clear
clf
colordef(1,'white')

f=0:5/128:5;

ripple = 2;			%passband ripple in dB
ii = 3;
[z,p,k]=cheb1ap(ii,ripple);
[num,den]=zp2tf(z,p,k);
h=freqs(num,den,f);
mag=20*log10(abs(h));
ph=angle(h)*180/pi;

subplot(121)
lm1 = line('Xdata',f,'Ydata',mag,'Linestyle','-','Color','y','Erasemode','Xor');
lm2 = line('Xdata',f,'Ydata',mag,'Linestyle','-','Color','r','Erasemode','None');
axis ( [ 0 4 -30 5 ]);
axis('square')
xlabel('frequency (rad/s)'),ylabel('gain (dB)');

subplot(122)
lp1 = line('Xdata',f,'Ydata',ph,'Linestyle','-','Color','y','Erasemode','Xor');
lp2 = line('Xdata',f,'Ydata',ph,'Linestyle','-','Color','r','Erasemode','None');
axis ( [ 0 4 -180 180 ]);
axis('square')
xlabel('frequency (rad/s)'),ylabel('phase (degrees)');

fprintf(1,'Figure 5.4: order 3 Chebyshev filter with ')
fprintf(1,'%d',ripple)
fprintf(1,' dB ripple\n')
fprintf(1,'          : press return for orders 4 to 7\n')
pause

for ii=4:7

	[z,p,k]=cheb1ap(ii,ripple);
	[num,den]=zp2tf(z,p,k);
	h=freqs(num,den,f);
	mag=20*log10(abs(h));
	ph=angle(h)*180/pi;

	set(lm1,'Xdata',f,'Ydata',mag);
	set(lm2,'Xdata',f,'Ydata',mag);
	set(lp1,'Xdata',f,'Ydata',ph);
	set(lp2,'Xdata',f,'Ydata',ph);

	pause(1);
end