fast fourier transform frequency limit I'm a french student in engineering and I'm given a kind of mandatory technical project to work out on until February.

I must investigate the following article : https://www.osapublishing.org/DirectPDFAccess/C41EF419-AD7D-EDF3-A173E8B93A0B610C_350066/oe-24-19-22110.pdf?da=1&amp;id=350066&amp;seq=0&amp;mobile=no and implement the same kind of iterative algorithm on MATLAB.

Actually I'm not good at signal processing either that much, only have the basics, however I don't understand why they say "the inherent frequency interval limit (of fFT) can be overcome using discrete Fourier transform". In my opinion that is non-sense because fFT is basically just the same as dFT, you just have to sum the sampled values an other way with their odd and even indexes. Therefore I don't really understand what do they apply dFT for...

If someone could help me please he would be more than welcome !

Thank you
You are right. DFT and FFT are the same things; they produce the same outputs and they operate on the same samples. FFT is just a fast implementation of DFT with much less artihmetic operations. They only have roundoff error difference which is due to the different number of arithmetic operations involved. Therefore you either misunderstood the article or what they say is wrong.