Stats

  • Locked Locked
  • Replies 1
  • Subscribers 126
  • Views 17942
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

Actual SNR value from FFT on transient analysis data

jdp721

Hi.

We know that SNR can be found using FFT on transient analysis data from Cadence (using calculator or Spectrum in plot), as well as Matlab (after importing data into it).

I am doing this for a delta-sigma modulator, and have taken all precautions like f_in = (D/N)*f_s : D = prime integer and N = no of points of FFT...

Now comes the question (rather, confusion):

In some references (ref 1, ref 2 etc.), it is stated that:

"FFT acts as a narrowband spectrum analyzer with a bandwidth of fs/N that sweeps over the spectrum. This has the effect of pushing the noise down by an amount equal to the process gain..."
"...For correct frequency domain measurements it is also necessary to apply corrections for FFT processing gain...theoretical noise floor for N-point FFT is 10log(N/2) dB below the quantization noise due to processing gain of the FFT"


So my question, do we really need to subtract 10log(N/2) dB from the SNR computed using FFT in Cadence? 

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.