- #1
O.J.
- 199
- 0
Hello,
I have a very basic FFT question. Correct me if I am wrong, but the FFT is a fast implementation of the DFT (which is essentially the same as Discrete Time Fourier series). The DFT is periodic in time and frequency. Thus if you input a time domain made of 4 times samples for example to the FFT block, it will give u a frequency spectrum 4 point output. Both these, the input and output are considered periodic. Also, doesn't the FFT treat its input as periodic?
Shouldnt a cosine input to our FFT block (as long as its sampled above the nyquist) always give us two impulses (since its periodic)? Why can't we get those two impulses?
and if so, then why does this document (and my experiemental results) contradict this:
Read page 15.
http://www.ee.nmt.edu/~elosery/matlab/matlab.pdf
I have a very basic FFT question. Correct me if I am wrong, but the FFT is a fast implementation of the DFT (which is essentially the same as Discrete Time Fourier series). The DFT is periodic in time and frequency. Thus if you input a time domain made of 4 times samples for example to the FFT block, it will give u a frequency spectrum 4 point output. Both these, the input and output are considered periodic. Also, doesn't the FFT treat its input as periodic?
Shouldnt a cosine input to our FFT block (as long as its sampled above the nyquist) always give us two impulses (since its periodic)? Why can't we get those two impulses?
and if so, then why does this document (and my experiemental results) contradict this:
Read page 15.
http://www.ee.nmt.edu/~elosery/matlab/matlab.pdf