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Noise floor calculation from fft ouput
ksr
post Mar 30 2012, 10:03
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Hi guys,

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

Thanks in Advance
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saratoga
post Mar 30 2012, 15:52
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QUOTE (ksr @ Mar 30 2012, 05:03) *
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.
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ksr
post Apr 2 2012, 05:59
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[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...
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Garf
post Apr 2 2012, 09:13
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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?
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ksr
post Apr 2 2012, 10:04
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QUOTE (Garf @ Apr 2 2012, 13:43) *
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.
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