1 | The recursive structure of the binary FFT algorithm is a complete binary tree of logN levels shown below for N=16 |
2 | At each phase, one relates the FFT of M numbers to FFT of even and odd subsets fE fO of this set -- these are of size M/2 |
3 | Diagram shows binary digit (XXXX) of relevant elements |
4 | e.g. XXX1 are all odd indices m; XX11 is set 4m-+3 where m- lies between 0 and 3 |