Graphical determination of the group delay characteristics of digital filters

The magnitude and phase responses of IIR or FIR digital filters can be determined analytically or graphically from the filter pole-zero pattern in the z-plane. Only analytical methods of determlning the group delay response have been presented. In this work we shall show that the group delay response of any digital filter can be determined graphically from the pole-zero pattern of the filter transfer function in the z-plane. This would be quite helpful for designers working on the design of digital delay equalizers and digital filters satisfying predetermined delay characteristics. The method, proof and several illustrative examples shall be presented.