On the usefulness of group delay and/or phase delay parameters for low distortion transmission

It is argued that transmission systems/filters, etc., design must be carried out basically in the time domain in terms of rise time, overshoot or undershoot of the instantaneous amplitude/ phaselfrequency specifications. No attempt should be made to define the group delay characteristics because it is neither sufficient, nor necessary. Group delay approximating functions and measurements should be kept where they belong; in the design and measurements concerned with delay, lines.