close all, clear all, clc
% Chebyshev II Lowpass Filter
SR = 10E3; % 10 kHz sample rate
SR2 = SR/2;
Fp = 2E3; % Passband ends at 2 kHz
Fs = 3E3; % Stopband begins at 3 kHz
Wp = Fp/SR2;
Ws = Fs/SR2;
Rp = 0.5;
Rs = 30;
[N, Wn] = cheb2ord(Wp, Ws, Rp, Rs);
[B, A] = cheby2(N, Rs, Wn);
[H, w] = freqz(B, A);
subplot(2,1,1), plot(w/pi*SR2, abs(H)), grid
subplot(2,1,2), plot(w/pi*SR2, angle(H)), grid