FFT for ADC output

Discussion in 'Programmer's Corner' started by wks_19, Jun 15, 2010.

  1. wks_19

    Thread Starter New Member

    Jun 15, 2010
    I want to know how the digital output of an ADC can be used to calculate FFT. As FFT input needs real and imaginary parts for its calculation?

  2. davebee

    Well-Known Member

    Oct 22, 2008
    If all you care about is how much power is in the signal as a function of frequency, then you can supply a single array of values as the real part of the signal and supply an array of zeroes as the imaginary part of the input signal.

    You can do the FFT, then combine the sine and cosine outputs into a single power spectrum array which will tell you the power as a function of frequency.

    So if you don't care about the phase relations of the input signals then you don't need to supply any actual data for the imaginary input array.
  3. t06afre

    AAC Fanatic!

    May 11, 2009
    A real FFT function, real because it use real numbers as input. May use an array of samples from an ADC as a input. The output from such a routine will be some sort of complex number. This complex number can be decomposed in a amplitude and phase spectrum.