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Thread: Discrete Fourier Transform as an interpolater

  1. #1 Discrete Fourier Transform as an interpolater 
    Forum Freshman wonkothesane's Avatar
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    Feb 2007
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    I've been working on frequency domain block digital filters recently and came across some literature that stated that zero padding the end of a time-domain sequence and taking the DFT results in an interpolation of the spectrum.

    eg. x[n] = sinc[n]; 0 < n< N
    Xinterp[p] = DFT{ x[m]; 0 < m < N
    0; N < m < 2N
    };

    resulting in Xinterp[2p] = X(p/2); 0 < p < N
    where X(k) = DFT{x[n]}

    I tried this in SciLab with sinc functions ( for FIR filters ) and the interpolation was perfect, but worked less well for less correlated signal (as I guess would be expected of any interpolater?).

    My questions are:
    1) Does anyone know of a textbook or other reference source with more info on this subject, I haven't come across it in any books I have that treat DFT
    2) What kind of signals is this technique good/bad for and what are some applications

    Cheers


    Fry me a kipper skipper, I'll be back for breakfast!
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  3. #2  
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    Have you tried 'Schaum's outline series' ? That'd be the place I'd look.


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