AbstractThe ideal channel-fil or in a digital communication system is a linear phase filter with a specia1 kind of simmetry around the cut-off frequncy. In most practical designs it is impossible to satisfy such phase linearity requirement, there fore the system perform deteriorates. Since the digital simulation technique is becoming powerful tool in the analysis and design of communica ion systems, techniques for the efficient simulation of group delay distortions are considered here. In perticular this paper deals with a method of defining a proper digital filter (IIR), which simulates linear and quadratic distortions of the group delay curves, by using time-dom in algorithms.