FFT

[Sharmi]

Hi,

I am trying to view the FFT of a single frequency complex signal split up into I and Q channels.

I set the frequency of the original signal to 1GHz and amlitude to -20dBM. However when I view the FFt for the two channels I am getting the spikes at 500 in the X-axis and the amplitude is at 0.  Could someone tell me why is this happening

For fft the X axis should be frequency , I was not sure which graph to select so I selected the waveform graph. But the X axis for this graph is time.

Is there any other graph that I can use to view FFT. 

Thanks so much,

Sharmi

[altenbach]

Show us some code, because there are many ways to do what you describe. Are you operating on arrays or waveforms or dynamic data? How do you set the frequency? Which FFT are you using?

If you do the FFT on a plain 1D array, you don't have timing information and dt=1, the transform is df=1 by default. All you need to do is calculate df based on the known dt and apply it to the graph of the transform, for example. Are you combining the I and Q data into a single complex array?

The x-axis is whatever you want ot to be. Just because the default x-label is time does not mean you cannot change it to anything you want.

[Sharmi]

Hi,

Please find attached the codes and the results.

Please let me know your comments.

Thanks,

Sharmi