How to remove noise from the signal analyzed by fft

i analyzed tide signal want find to the actual frequency but fft product many noise

i want remove it

matlab have which code can remove noise

thanks

Answer 1

[Star Strider]

Probably the easiest way to deal with a noisy signal (considering that the nature of the noise is not stated here) is to use the Signal Processing Toolbox sgolayfilt function. I usually choose a 3-degree polynomial, and then adjust the window length until I get the result that I want.

Take the fft of the smoothed signal to determine the frequency. It will have the same length and sampling frequency of the original data.

[peter huang]

thanks~

[Star Strider]

As always, my pleasure!