Fast non-recursive computation of individual running harmonics

It has been recently shown that the fast Fourier transform of a sequence wh ich slides over a time-limited rectangular window can be carried out in a n onrecursive manner by means of O(N) computations. When only certain individ ual harmonics are needed, the application of this technique leads to O(log, N) additions and O(log, N) multiplications per harmonic. In this paper, an improvement is proposed by which any harmonic can be calculated at a cost of O(log, N) additions but only two complex multiplications. The nem techni que stems from the application of the frequency-shifting property to existi ng methods.