Hello!
DFT and FFT are both for discrete signals.
Or maybe you wanted to say that with DFT you can calculate any number of
frequencies arbitrarily while FFT calculates a fixed and predetermined set
of frequencies? OK, but the frequency set is not continuous. All the frequencies
are equally spaced and their number is a power of 2.
But: for a fixed time input (power of 2 number of samples), you can calculate
a corresponding fixed sample of frequencies with either method, it's exactly
the same. If we have N time samples, we can calculate N dfrequencies.
It will take N^2 multiplications with DFT and NLog2(N) with FFT.
Example for 1024 samples: 1 million multiplications for DFT and only 10 000
for FFT.
Dora.
Aya2002 said:
the difference between the Fourier Transform and the Discrete Fourier Transform is that the first for continues frequency and the second for discrete frequency while the fft is an algorithm that is faster than the dft.
regards