Butterworth Filters
w = logspace(-1,1,201); colors = ['b' 'g' 'r' 'm' 'k']; for m=1:5 order = 2*m; [z p k] = buttap(order); [bp ap] = zp2tf(z,p,k); hh = freqs(bp,ap,w); ha = abs(hh); semilogx(w,ha,colors(m),'LineWidth',2); hold on; end xlabel('frequency (\omega/\omega_o)'); ylabel('magnitude response'); axis([0.1 10 0 1.05]); grid; hold off;
![](Butterworth_01.png)