The Elliptic Filter has a Chebyshev Type I style equiripple passband, an equiripple stopband, a sharp cut-off, a high level group-delay, and the largest stopband attenuation value. As in the Chebyshev Type I Filter, the Elliptic passband attenuation is defined to be the same value as the passband ripple amplitude. However, FilterSolutions allows the user the option of selecting any passband attenuation, (in dB), that will define the filter’s cut-off frequency.
FilterSolutions also offers the user the option of constricting the passband ripple to a percentage of the passband. Shown below are examples of 5th order Elliptic low-pass, high-pass, bandpass and bandstop filters and low-pass step response. The stop band ratio is 1.2 in all cases shown.
It is useful to compare the stopband attenuation and the group delay to that of the Chebyshev II and Hourglass Filters.