A method and apparatus for determining the dispersion characteristics of minimum phase filters using substantially only an amplitude response of a minimum phase filter under test includes fitting an amplitude spectrum of the minimum phase filter with a substantially straight line curve, and determining the dispersion characteristics of the minimum phase filter using the straight line curve and the relationships determined by the inventors. Various inventive equations determined by the inventors representative of the relationship between an amplitude response of a minimum phase filter and the dispersion characteristics of the minimum phase filter are used for determining the dispersion characteristics of the minimum phase filter.