Method for reducing group delay distortion

A method is disclosed for eliminating group delay distortion resulting from filtering an information-carrying analog signal. The method allows an analog signal to be converted to digital form and back again with zero group delay distortion. The analog signal is first band or low pass filtered with a filter having a pass band substantially larger than that required to filter only the signal of interest. The filtered signal is then digitized at a rate appropriate to the filtered signal, digitally filtered to remove all but the signal of interest, and down sampled to the transmission rate. A substantially reversed process is described for reconverting the digital signal to analog form. The method is shown to be equally effective with a multiplexed signal.