The Passive Filter
The original passive filter, still much used today. All the elements are passive LCR, as lumped or transmission line
when distributed, thus in contrast to an active filter there will always be a loss factor. These filters come in many
formats, response, in many cases used as prototypes for active (digital) filters. Here are a number of links to different
filter designers
Butterworth Filters
This is a class of maximally flat filters. A compromise between flat group delay, rolloff and flat magnitude.
Butterworth Filters
Bessel Filters
This is a class of maximally flat group delay filters. Poor roll-off, hence a continuous magnitude droop. Emphasis is a flat group delay
Bessel Filters
LinearPhase Filters
This is a class of equi-ripple linear phase filters. Phase Ripple <= 1 degree.
LinearPhase Filters
Guassian Filters
This is a class of pure state Guassian filters.
Guassian Filter
Legendre Filters
This is a class of Legendre or Papoulis Filters.
Legendre Filter
Elliptic Filters
A class of equi-ripple in-band and equiripple out-band filters. ie: a superposition of Chebychev type 1 and Chebychev type 11.
Elliptic Filters