ellipap(N, rp, rs)¶
Return (z,p,k) of Nth-order elliptic analog lowpass filter.
The filter is a normalized prototype that has rp decibels of ripple in the passband and a stopband rs decibels down.
The filter’s angular (e.g., rad/s) cutoff frequency is normalized to 1, defined as the point at which the gain first drops below
Filter design function using this prototype
Lutova, Tosic, and Evans, “Filter Design for Signal Processing”, Chapters 5 and 12.