F1 = 1000;      F2 = 1200;
Fe = 9.725e3;   Te = 1/Fe;

t = 1:440;
E_F1 = sin(2*%pi*F1*t*Te);
E_F2 = sin(2*%pi*F2*t*Te);

trameFSK = [E_F1 E_F2 E_F1 E_F2 E_F1 E_F1 E_F2 E_F2];

num_pBande    = [1, 0, -1];
den_pBande_f1 = [26, -40, 24];
den_pBande_f2 = [22, -30, 20];

num_pBas = [1, 1];
den_pBas = [29, -27];


SF1 = filter(num_pBande, den_pBande_f1, trameFSK);
SF2 = filter(num_pBande, den_pBande_f2, trameFSK);

SR1 = abs(SF1);
SR2 = abs(SF2);

SD1 = filter(num_pBas, den_pBas, SR1);
SD2 = filter(num_pBas, den_pBas, SR2);

SD = SD2 - SD1;

plot(SD);