How specification methods relate to analog filter prototypes

Filter

Notes

Bessel

You only need to specify the order.

Butterworth

If you specify the order, Embed determines the attenuation. If you specify the attenuation, Embed determines the order.

Chebyshev

If you specify the order, then the order and epsilon define the filter. The attenuation is fixed once a particular order and epsilon are chosen. If you specify attenuation, Embed determines the order based on the attenuation and epsilon. Embed determines the order such that the attenuation and epsilon specifications are met.

Inverse Chebyshev

Whether you specify the order or epsilon, the attenuation needs to be specified. If you specify the order, Embed computes the epsilon based on the attenuation and the attenuation level desired. In general, as the attenuation desired for a fixed-order filter increases, the corresponding epsilon also increases. This property could be exploited to yield very narrow band filters by specifying an extremely high attenuation, along with a narrow band. If you specify epsilon, Embed determines the order based upon the attenuation desired. Embed determines the order such that the attenuation and epsilon specifications are met.

The order of the filter that is generated is twice the order of the filter specified. For example, if you enter 2 in the Order box for a Band Pass filter, the filter generated will have an order of 4.