A new approximation theory for Z-domain elliptic transfer functions

The authors presents a new approximation theory for the derivation of discrete-domain denormalized lowpass, highpass, bandpass, or bandstop transfer functions with elliptic loss-frequency characteristics. The salient characteristics of the proposed approximation theory is that it makes no recourse to the concept of a corresponding continuous-domain elliptic prototype reference transfer function. The approximation theory is based on the derivation of a discrete-domain normalized lowpass elliptic transfer function, and on the transformation of the normalized lowpass transfer function to the desired denormalized elliptic transfer function by using discrete-domain to discrete-domain frequency transformations