Optimizing elliptic filter selectivity

The problem of determining the band-edge selectivity of elliptic filters an d its optimization in filter design is considered. The band-edge selectivit y is derived with respect to the n-th order elliptic function. The selectiv ity formula embodies potential trade-offs in filter requirements for improv ing filter mangitude or delay response. Design examples are submitted in su pport of the theory. A simple proof describes the Chebyshev filter as an el liptic filter in the limit of infinite stopband corner frequency.