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The Symplectic Finite Fourier Transform (SFFT) of a 2D periodized sequence $x[k,l]$ with periods $(M, N)$ is defined as

$$X[n,m] = \sum_{k=0}^{M-1} \sum_{l=0}^{N-1} x[k,l] e^{-j2\pi \left(\frac{mk}{M} - \frac{nl}{N}\right)}$$

Is the above expression equivalent to an FFT performed on the rows of $x$ and IFFT performed on the columns? If yes, does the following code justify the observation?

function [X] = SFFT(x)

% 1. transpose the sequence x to convert rows into columns
% 2. execute fft() command to compute fft of the columns (which are originally
% rows)
% 3. transpose the matrix back to original form
% 4. execute ifft on the columns

X = ifft(fft(x.').');        
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    $\begingroup$ Yes That right. $\endgroup$ Commented Sep 1, 2020 at 14:14
  • $\begingroup$ In another source, it is given X = ifft(fft(x).').';. Which one is correct? $\endgroup$
    – MaxFrost
    Commented Sep 1, 2020 at 14:54
  • $\begingroup$ Both must give the same results. Do you see it different ? $\endgroup$ Commented Sep 13, 2020 at 2:18

1 Answer 1

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This is the FFT

Y = ifft(fft(X).').';

While this is the inverse FFT

X = ifft(fft(Y.').'); 
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