FFT vi truncate the signal freq.

[student_1]

Hello,

I noticed that the FFT vi truncate my signal. see attachments.

I am basically removing noise from a signal (I have both the in-phase -I- and out of phase -Q- signals...)

(Ignore the curve fitting vi, that's just to remove the DC component from the signal, this is irrelevant to this discussion).

Regards,

Ali

[student_1]

I think I discovered the problem, I will post here once I solve it.

[RavensFan · Accepted solution]

You are losing your timing information for the data going to the PSD graph.  It is operating on arrays.  The FFT functions assume a dT or dF of 1.  So when things are put into the graph, you are seeing values up to 0.5 since Nyquist limits you to 1/2 of the sample frequency.  The PSD2 graph does not have this problem because the blue DDT wire maintains the timing data.

If you build your array into a waveform datatype and bundle in the dT value, your data should look like the other graph.

[student_1]

That's right, I do not know how I did not notice it although I already used this VI in another place in the same program. Thank you.