Noise floor calculation from fft ouput Options

[ksr]

Hi guys,

Can anyone explain me ,how to calculate noise floor value from fft output????

Thanks in Advance

[saratoga]

Hi guys,

Can anyone explain me ,how to calculate noise floor value from fft output????

FFT of what exactly? Usually the noise floor is calculated the same in the time and frequency domain: take the mean or standard deviation of the output when no signal is present.

[ksr]

[quote name='saratoga' date='Mar 30 2012, 20:22' post='791053']
[quote name='ksr' post='791032' date='Mar 30 2012, 05:03']Hi guys,

Thanks bro for your reply.The fft output of a single tone and multiple tone.For single tone and also for multiple tones ,am averaging all the peak amplitudes except the values at the given frequencies.I dont know whether my approach is wrong or right...

[Garf]

This won't work very well due to spectral leakage, which will increase the floor in frequencies near, but not at, the tone. Why do you need a tone anyway?

[ksr]

This won't work very well due to spectral leakage, which will increase the floor in frequencies near, but not at, the tone. Why do you need a tone anyway?

I tried calculating SNR, THD, NOISE FLOOR, but what ever i have studied theoretically and calculated practically doesn't seem to match with the spectra lab result.