# system identification: MATLAB tfestimate gives different results for different Fs

So I have an experimental data; A is a chirp signal (sweep sine wave) and B is the response of the system. I identify the system as follows in MATLAB:

figure
Ts= 1e-4;
Fs = 1/Ts;
[T,f]=tfestimate(A,B,[],[],[],Fs);
semilogx(f,20*log10(abs(T)));
grid


But when I change Ts to different values (e.g. 1e-2), the plot changes. For instance

This is with Ts = 1e-2

This is with Ts = 1e-4

Can anyone help me figure out what the correct value of Ts is, so my reported eigenfrequencies are correct?

• why not use the actual sample rate? – Stanley Pawlukiewicz Dec 27 '18 at 19:16
• Please also respond to the comments on the same question you posted on Reddit instead of reposting the question at multiple places. – fibonatic Dec 27 '18 at 23:06
• what is your B ? – Ahmad Bazzi Dec 28 '18 at 13:07