butterwarth filter.m

It a filter. Buterwarth filter. very important tool in gsm

wp = 0.2 * pi; % Panband frequency is rad
ws=0.3*pi; % Stopband frequency is rad
Rp = 1;
As = 15;
T = 1;
OmeagaP = (2/T)*tan(wp/2);
OmeagaS = (2/T)*tan(ws/2);
N = ceil((log10((10^(Rp/10)-1)/(10^(As/10)-1)))/(2*log10(OmeagaP/OmeagaS)));
OmeagaC = OmeagaP/ ((10^(Rp/10)-1)^(1/(2*N)));
wn = 2*atan((OmeagaC*T)/2);
wn=wn/pi;  % Butterworth in pi units
[b,a]= butter(N,wn);
[bp,B,A]= dir2cas(b,a)