| Аннотація | The problem of realisation of the Discrete Fourier Transform in on-line is analysed because of non-efficient consuming a time for a new recalculation of spectrum samples if one discrete-time signal sample or even some small portion of samples in period are replaced by new sample or by new samples, respectively. Using Fast Fourier Transform (FFT) procedure it is assumed that some signal samples in the respective period available for processing digitally are updated by a sensor in real time. It is urgentfor every new sample that emerges to have a new spectrum. The ordinary recalculation of spectrum samples even with highly efficient Cooley-Tukey FFT algorithm is not suitable due to speedy varying in time real process to be observed. The idea is that FFTprocedure should not be recalculated with every new sample, it is needed just to modify it when the new sample emerges and replaces the old one. We retrieve the recursive formulas for FFT algorithms that refer to the spectrum samples modification. In acas |