Question

What is the difference between decimation in time and decimation in frequency

Answer 1

1. DITFFT stands for Decimation in Time Fast Fourier Transform and DIFFFT stands for Decimation in Frequency Fast Fourier Transform.
2. In DITFFT, input is bit reversed while the output is in natural order, whereas in DIFFFT, input is in natural order while the output is in bit reversal order.
3. DITFFT refers to reducing samples in time domain, whereas DIFFFT refers to reducing samples in frequency domain.
4. DITFFT splits the two DFTs into even and odd indexed input samples, whereas DIFFFT splits the two DFTs into first half and last half of the input samples.
5. DITFFT algorithm reduces the number of complex multiplications required from N^2 to N*logbase2(N), whereas DIFFFT algorithm reduces the number of complex multiplications from N^2 to (N/2)*logbase2 (N).
6. In DITFFT, butterflies are defined on the last pass of FFT, whereas in DIFFFT, they are defined on the first pass of FFT.