Design of variable fractional delay allpass filter using weighted least squares method

In this paper, a weighted least squares method is presented to design a variable fractional delay allpass filter. First, each coefficient of the variable allpass filter is expressed as the polynomial of the fractional delay parameter. Then, by minimizing the phase approximation error, the optimal polynomial coefficients can be obtained by solving a set of linear simultaneous equations. Finally, the design examples are demonstrated to illustrate the effectiveness of the proposed approach.