ABSTRACT
This chapter describes ideal filters and then a selected set of practical filters. Filters are widely used to pass signals at selected frequencies and reject signals at other frequencies. An electrical filter is a circuit that is designed to introduce gain or loss over a prescribed range of frequencies. The magnitude functions of causal versions of low-pass, high-pass, band pass, and band stop filters have gradual transitions from the pass band to the stop band. The magnitude function of the n-pole Butter worth filter has a monotone characteristic in both the pass band and stop band of the filter. There are four basic types of ideal filters: low-pass, high-pass, band pass, and band stop.
