Method and apparatus for suppression of error accumulation in recursive

Abstract

To limit the accumulation of recursive computation errors while recursively calculating the discrete Fourier transform of an input signal in response to moving window sample sets of that signal, the dependent variables for the recursive calculations are periodically refreshed. One embodiment generates an error limited continuous discrete Fourier transform of the input signal through the use of duplicate channels which are periodically reinitialized in time staggered relationship and alternately switched on-line and off-line in time synchronism with the reinitialization process. Each of the channels of that embodiment is equipped to recursively calculate the discrete Fourier transform of the input signal so that while one channel is on line feeding recursively calculated transform coefficients to the outputs, the other channel or channels are off-line being reinitialized and then computing fresh sets of transform coefficients for subsequent on-line recursive calculations. Another embodiment performs essentially the same function through the use of an on-line main processing channel which recursively calculates the discrete Fourier transform coefficients of the input signal on the basis of successive sets of dependent variables which are computed in and supplied by a periodically reinitialized off-line auxiliary processing channel.