Ideal Spectral Interpolation
Ideally, the spectrum of any signal
at any frequency
is obtained by projecting the signal
onto the
zero-phase, unit-amplitude, complex sinusoid at frequency
[264]:
![]() |
(3.43) |
where

Thus, for signals in the DTFT domain which are time limited to
,
we obtain
![]() |
(3.44) |
This can be thought of as a zero-centered DFT evaluated at


![$ k\in[0,N-1]$](http://www.dsprelated.com/josimages_new/sasp2/img101.png)
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Spectral Roll-Off