% first order of IIR lowpass filter
% Use bilinear meathod

clear;
fi=1;fs=10;Gc2=0.9;
wc=2*pi*fi/fs;
omegac=tan(wc/2);
alpha=(sqrt(Gc2)/sqrt(1-Gc2))*omegac;
a=(1-alpha)/(1+alpha);
b=(1+a)/2;
w=0:pi/300:pi;
Hw2=alpha^2./(alpha^2+(tan(w/2)).^2);
plot(w/pi,Hw2);
grid;
hold on;