Physically Feasible Stable Filters
A filter is considered feasible if its impulse response, denoted as h(t), is zero for t < 0.
Commonly used linear filters include the following types:
Low-pass filters
High-pass filters
Band-pass filters
Band-cut filters
There are also specific filter designs such as Butterworth filters, Chebyshev filters, and elliptical filters (Cauer filter).
The design of linear filters involves using a template that consolidates the characteristics of the desired frequency gain.