Discrete Fourier Transform Frequency

  • #1
Hi everybody,

I'm in the process of writing a discrete Fourier transform program using the algorithm on the DFT wikipedia page. When I throw in functions that I know the frequency domain signal of it gives the predicted shape but I have absolutely know idea how to generate a frequency axis.

Does anybody here know how I can compute the frequency values?

Thanks in advance.

Chris
 

Answers and Replies

  • #2
Redbelly98
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Try using a sine function at a specific frequency. Then whatever you get for the Fourier Transform corresponds to that frequency.
 
  • #3
jbunniii
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Hi everybody,

I'm in the process of writing a discrete Fourier transform program using the algorithm on the DFT wikipedia page. When I throw in functions that I know the frequency domain signal of it gives the predicted shape but I have absolutely know idea how to generate a frequency axis.

Does anybody here know how I can compute the frequency values?

Thanks in advance.

Chris

The DFT gives you N evenly spaced samples of the DTFT (discrete-time Fourier transform). The frequencies corresponding to these samples are

[tex]\frac{n}{N} F_s[/tex]

where [itex]n = 0,1,\ldots,N-1[/itex] are the indices of the samples, and [itex]F_s[/itex] is the sampling frequency of the input sequence.
 

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