Matlab FFT - sampling frequency

For the evaluation of ultrasound measurement data the frequency analysis should be carried out by means of Matlab. A sampling frequency is set in advance. How is this defined? Is this the maximum range in the frequency spectrum that I would like to expect and evaluate? That If I have a starting frequency of, say, 20000 Hz, maybe I'm still interested in the first harmonic excitation, could I choose 50000 Hz as the sampling frequency?

Many thanks!

Frank

Answer 1

[Honglei Chen]

It should match the sampling frequency used to obtain your digital signal, otherwise your interpretation of the signal is wrong. In other words it's a meta data of your measurement.

HTH