TABLE OF CONTENTS Analog filters are defined over a continuous range of frequencies. They are classified as low-pass, high-pass, band-pass and band-elimination (stop-band).
An all-pass or phase shift filter has a constant magnitude response but is phase varies with frequency.
A digital filter, in general, is a computational process, or algorithm that converts one sequence of numbers representing the input signal into another sequence representing the output signal.
A digital filter, besides filtering out unwanted bands of frequency, can perform functions of differentiation, integration, and estimation.
Analog filter functions have been used extensively as prototype models for designing digital filters.
An analog filter can also be classified as passive or active. Passive filters consist of passive devices such as resistors, capacitors and inductors. Active filters are, generally, operational amplifiers with resistors and capacitors connected to them externally.
If two frequencies ? 1 and ? 2 are such that ? 2 = 2 ? 1, we say that these frequencies are separated by one octave, and if ? 2 = 10 ? 1, they are separated by one decade.
The analog low-pass filter is used as a basis. Using transformations, we can derive high-pass and the other types of filters from a basic low-pass filter.
In this chapter we discussed the Butterworth, Chebyshev Type I & II, and Cauer (elliptic) filters.
The first step in the design of an analog low-pass filter is to derive a suitable magnitude-squared function A 2( ?), and...
