Recursive discrete fourier transformation method and recursive inverse discrete fourier transformation method

摘要

When obtaining the newest N data of successively supplied data while deleting old data to store them temporarily, a difference between a data value supplied just before and a data value to be deleted is supplied from a data updating portion. The difference value and a result of preceding FFT operation just before stored in a memory portion temporarily are supplied to a recursive DFT operating portion. These values are subjected to arithmetic operation according to a predetermined method so as to output the result of FFT operation on the newest N data values.