The Filter finds use in circuits of audio equipment, video equipment, broadband and communication. Electronic signal processing filter is described to be linear or non-linear, analogue or digital, shift invariance, passive or active circuit.
The filter frequency response can be classified as:
- all-pass filter
- cut-off frequency.
The order of a filter refers to the slope of the transition to roll-off around the cut-off frequency. A first-order filter responds at -6 dB per octave, a second-order filter decreases at -12 dB, a third-order at -18 dB, on a logarithmic scale. The analogue filter in a linear design of a network synthesis type is known as the Butterworth filter, Chebyshev filter, Elliptic filter, Bessel filter and Gaussian filter.