PHASE AND DELAY APPROXIMATION FOR 1-D DIGITAL IIR FILTER IN THE L-INFINITY NORM

The phase response of a digital all-pass filter is often used to appro ximate a prescribed phase or delay. Based on the nonlinear Tchebycheff approximation theory, the phase and delay functions are investigated. A number of necessary and sufficient (NS) conditions that characteriz e the best approximation are obtained. Numerical design methods using the phase or delay functions of a digital all-pass filter yield the mi nimal unique global solution. A trigonometric rational function is der ived for optimal approximation of a desired group delay. (C) 1997 Else vier Science B.V.