A new method for digital all-pass filter design

A new method for the design of digital all-pass filters using Chebyshev criterion is introduced. It is based on a phase approximation algorithm for polynomial transfer functions. The algorithm exploits a scheme of iteratively linearizing the nonlinear constraints in a nonlinear programming and converges theoretically. The design method has the advantage that it finds the best uniform phase approximation to an arbitrarily specified phase response without any initial guess of the solution. Design examples of orders up to 80, obtained on an IBM-PC/XT personal computer, are given to show the practicability of the method.