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Simple Fourier transform problem

  1. Mar 2, 2015 #1
    1. The problem statement, all variables and given/known data
    Given x[n] with transform X(ejw), find the fourier transform in terms of X(ejw).

    x1[n]=[0.9ncos(0.6*pi*n)] * x[n-2]

    2. Relevant equations
    time shift: x[n-k] -> e-jwkX(ejw)
    convolution: x[n] * h[n] -> X(w)H(w)
    freq. shift: x[n]ejwcn -> X(ew-wc)

    3. The attempt at a solution
    I think that this problem has no solution because 0.9n has no Fourier transform (not summable). 0.9nu[n] on the other hand does but not the same case here. am i doing this right?
    Last edited: Mar 2, 2015
  2. jcsd
  3. Mar 2, 2015 #2


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    I am at a loss to understand the problem. It seems to me as if the problem is to calculate the Fourier transform of a constant - or a sequence of constants. Is that correct?
  4. Mar 2, 2015 #3
    yeah, I guess i didn't word it correctly. what it reads exactly is 'given a sequence x[n] with Fourier transform Xejw, determine the Fourier transform of the sequences in terms of Xejw.
  5. Mar 3, 2015 #4


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    Science Advisor

    Still does not make any sense to me...
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