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% exam6_13.m - MATLAB script for example 6-13
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Wp = [100  200]/500;  Ws = [50  250]/500;
Rp = 3;  Rs = 30;
[N, Wn] = buttord(Wp, Ws, Rp, Rs);
[b, a] = butter(N, Wn);
freqz(b, a, 128, 1000);