An elliptic or Cauer filter can be generated with
cauer ( <order> , <ripple> , <stopband> ) ;
The bandwidth of this filter, defined in the same way as for Chebyshev filters, is 1rad/s. The stopband begins at <stopband>, so this variable must be larger than 1.
<order> : integer; order, <ripple> : real; passband ripple in dB, <stopband> : real; normalized lowest stopband frequency.