Re: FFT - Spectrum Analyzer

[Sergei Steshenko]

----- Original Message -----
> From: Damian Harty <address@hidden>
> To: "address@hidden" <address@hidden>
> Cc: 
> Sent: Monday, June 11, 2012 5:13 PM
> Subject: RE: FFT - Spectrum Analyzer
> 
[snip]
> ...but Fourier is predicated on the whole signal having the characteristics 
> of 
> the observed portion.
[snip]
> Regards,
> 
> Damian Harty 
> Senior Research Fellow
> Coventry University
> +44(0)24 7688 8924
> +44(0)7799 414832
> 

Yes and no.

Actually, no.

I mean Fourier (without the "Fast") transform is defined through integral from 
minus infinity to plus infinity.

DFT (i.e. Discrete Fourier Transform) is a transform defined on a _finite_ set 
of N samples. Anf no integral is involved, but a sum of products.

FFT (i.e. Fast Fourier Transform) is a way to implement DFT in a smarter way 
which reduces computational complexity from O(N ^ 2) to N * log(N).

So, regarding FFT, your "Fourier is predicated on the whole signal" statement 
is wrong WRT DFT/FFT.

Regards,
  Sergei.