ABSTRACT
In its broadest sense, a filter can be defined as a signal processing system whose output signal, usually called the
response,
differs from the input signal, called the
excitation,
such that the output signal has some prescribed properties. In more practical terms an electric filter is a device designed to suppress, pass, or separate a group of signals from a mixture of signals according to the specifications in a particular application. The application areas of filtering are manifold, for example to band-limit signals before sampling to reduce aliasing, to eliminate unwanted noise in communication systems, to resolve signals into their frequency components, to convert discrete-time signals into continuous-time signals, to demodulate signals, etc. Filters are generally classified into three broad classes:
continuous-time,
sampleddata,
and
discrete-time
filters depending on the type of signal being processed by the filter. Therefore, the concept of signals are fundamental in the design of filters.
