The bond between causal complex cepstra and Sheffer polynomials

A strong bond is established between causal complex cepstra and Sheffer polynomials. This bond results in the generation of parametric classes of discrete-time signals and their associated complex cepstra. These signals generally have more advanced singularities than the poles of signals with rational z-transforms. Examples are presented which illustrate the behavior of signals having branch points and essential singularities.