DFT for convolution like operation

menahemkrief

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Joined
Apr 3, 2014
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1
Hi,


Let x,y be finite real valued sequences defined on 0...N-1 and let g be a non negative integer .




define
35akubq.jpg

also on 0..N-1.




In addition, the DFT of y is known in closed form.
Is there a way to write z as some cyclic convolution, so that with the help of the convolution theorem z can be calculated in NLOG N istead of N^2?




I tried following the convolution therem proff but i get stuck:
10421hy.jpg





The problem is that the second sum depends on k so the double sum doesn't factor to the product of DFTs.




what am I missing?




thank you
 
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