On the computation of a minimum-phase spectral factor

The problem of finding the minimum-phase spectral factor of a linear-phase digital filter having double zeros on the unit circle is addressed. It is shown that a simple Newton-Raphson iterative algorithm can compute this factor quickly and accurately and a short Matlab program for doing the computation is given. The Newton-Raphson method is also compared to an alternative approach by finding the zeros of polynomials. The accuracy of solutions obtained is of major emphasis in the work.