A novel method for designing allpass digital filters

A novel method for designing recursive allpass digital filters is presented in this letter. This method uses cepstral coefficients to design the allpa ss filter. For a stable allpass filter, the denominator polynomial must be of minimum phase. For a minimum phase polynomial the magnitude function and the group delay function are related through the cepstral coefficients. He nce, given the group delay function, the cepstral coefficients correspondin g to the denominator polynomial part are first determined. From the cepstra l coefficients the minimum phase denominator polynomial coefficients are de termined through a nonlinear recursive difference equation.