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Help me understand this equation (DFT)

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mehtesham

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DFT

hi everybody

x[n] --DFT(N-points)--> X[k] --IDFT(M-points)--> y[n]

how we could find y[n] in terms of x[n] ? (for both M≥N and M<N)

is this correct ?

yp[n]=∑ x[n+rM] for r= -∞ to ∞ , y[n] = yp[n] , 0≤n≤M-1

if it is correct,how could be proved?
 

DFT

In my opinion the number of points should be equall.
 

    M

    mehtesham

    Points: 2
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Re: DFT

what is the differences between DFT and FFT?
 

Re: DFT

In general the DFT is discrete time but continuous
frequency. When the DFT frequency variable is discretized it is usually
still called the DFT.
The FFT is an efficient means of computing the DFT with discrete frequencies.

cheers...

Added after 11 minutes:

hi again,
some more detail for the topic...

The fast Fourier transform (FFT) is simply a class of special algorithms which implement the discrete Fourier transform with considerable savings in computational time. It must be pointed out that the FFT is not a different transform from the DFT, but rather just a means of computing the DFT with a considerable reduction in the number of calculations required.

please checkout this link for the detailed information about the DFT:
**broken link removed**
 

Re: DFT

I'm very interested in this topic because I'm studing DFT and FFT.

Can anyone help with some matlab example or a web where we could find them?.
 

Re: DFT

the best website for the examples in matlab is mathworks site itself. i am pasting the same. just it explains the FFT with some example.. checkout this link: **broken link removed**

if i get any more info abou this i'll be posting those here...

okie...
 

DFT

hi
In answering mehtesham, I think that in the case that M != N u cannot find a expression to relate X and Y. the onl way that may help u is reading upsampling and downsampling cocepts in descrete-time domain. ( a detailed info is saied in DSP by Oppenheim---> is available in EDAboard). read rhe concepts and conclude.
cheers
 

    M

    mehtesham

    Points: 2
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