Inverse filter to obtain the excitation signal. Here we make critical assumptions. 1) the excitation
signal can be removed from the original signal and 2) that this excitation signal when fed into a filtered loop
will respond as the original signal did. Therefore, in order to obtain the excitation signal, we delay the original
signal, run it through our filter, and subtract the resulting signal from the original to obtain the excitation signal.
Figure 11 shows the result obtained for this example.
Plot of the computed excitation signal over the original signal
The following code segment computes the excitation signal and writes it out to disk.
% find the excitation signal.
% FUND_F corresponds to the fundamental freq
N = round(fs/FUND);
del_y = [zeros(N,1);y(1:end-N)];
filt_y = filter(stmb,stma,del_y);
% filt_y = filter(B,A,del_y);
e_sig = y-filt_y;