I have a big issue, basically my goal is to create a low-pass butterworth filter around 0-35Hz with a sampling frequency of 5000Hz. My Matlab code is
Fs=5000; Wp=30/(Fs/2); Ws=45/(Fs/2); Rp_db=-20*log10(.95); Rs_db=-20*log10(.05); [order,wn] = buttord(Wp,Ws,Rp_db,Rs_db);
with the cutt-off frequency 0.135 (33,75 Hz).
Why does the sampling frequency affect so much the filter result? Thanks in advance