FFT accuracy and 'Noise Floor'
Hi all,
I have a question regarding the accuracy of FFT (I think). I'm trying to reconstruct a function with an exponential tail (hence the function amplitude changes some 25 orders of magnitude). I have the code below to illustrate what I try. For each of the trials I have a similar noise floor of 1e-15, no matter the sampling rate (see figure). I believe the accuracy is gets killed by the fact that the regions with very low amplitude has to be constructed by subtracting harmonics with a relatively higher amplitude (e.g. ~1e-3 - ~1e-3 =~1e-15). I know it is pretty hopeless, but I'd be glad if anyone has any suggestions to help me lower the noise floor.
Cem
a=0:0.001:0.999; funct=sin(2*pi*a(1:500)); funct=[funct,funct(end)*exp(-1*(1:500)/10)]; semilogy(a,funct) hold all semilogy(a,ifft(fft(funct)))
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