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What's main difference these two DFT and DTFT ?

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Linspire

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Can anyone explain difference these two DFT and DTFT ?


Regards
Linspire
 

Err, that's too much for me.

Linspire
 

Easy

In DTFT the frequency domain is not sampled. It's rather continuous.

In DFT the frequency domain is sampled. This indicates that the time domain should become periodic.

Anyway there are more to these terms and I don't want to confuse you. The above is the basic.
 
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Are these two some kind of representation mathematical expression for analog input to digital output or vice versa ?

Linspire
 

Yes. They are really helpful in implementing in computers (i.e. processors) where we don't have analog at all and everything is digital.
 

DFT & DTFT are the nothing but how you express an irregular waveform in sine and cosine terms.

If you decompose your continuous periodic signal into sum of sine it is called "fourier series"

Similarly

continuous non periodic : fourier transformation

Discrete periodic : Discrete fourier transformation (DFT)

Discrete non periodic : Discrete time fourier transformation (DTFT)

If you are new to DSP, go through the book "the scientists and engineers guide to DSP" by smith.

It helps you a lot.

Thanks,
Vidya
 

Discrete non periodic : Discrete time fourier transformation (DTFT)

u can consider the part of the sequence u want to make and then it is assumed to be periodic over tht interval
eg: x(n)=0,1,2,3,4
if u want to find the DFT of this sequence x(n) then it is assumed to be periodic like x(n)=0,1,2,3,4,0,1,2,3,4,0,1,2,3,4.....................
then u take the DTFT . DTFT of this sequence is continuous and periodic in frequency domain which is sampled for N-points ( by using twiddle factor - which divides the unit circle into N parts in Z domain) , this the reason it is called N- point DFT . More the samples accurate is your reconstruction using fourier analysis.

cheers,

Pavan :-D
 

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