a 1 - bit signal processor receives a 1 - bit signal having a first sampling rate eg 64 fs . an upconverter increases the sampling rate to eg 128 fs . a series of delta sigma modulators processes the signal . the processed signal is down - converted by a converter to 64 fs . as least the delta sigma modulators may be implemented on an integrated circuit . the down - converter is arranged to prevent noise being folded back into the signal band .