function  y=bp(x,fs)
fs=fs/2;

 
Wp=[8/fs 15/fs];% 7Hz <-> 15Hz  =1
Ws=[2/fs 20/fs];%10   <0.5 =0, >20 =0


Wn=0;
[N,Wn]=CHEB1ORD(Wp,Ws,5,30);
[B,A] = CHEBY1(N,0.5,Wn);
 y = filtfilt(B,A,x);
% y=x;
% figure
% FREQZ(B,A,64,128);
