A Butterworth filter is an analog filter that consists of frequency-determining components that determine the transmission behavior. Analog filters can be used to influence certain filter characteristics such as the frequency range, bandwidth, attenuation, phase response, slope, group delay, and several others.
In analog filters, there are several types of filters such as the Bessel filter, Chebyshev filter, and Butterworth filter, which have their own distinct characteristics. While the Bessel filter has a constant group delay and a linear phase behavior, the Chebyshev filter shows a steep slope after the cutoff frequency and the Butterworth filter presents itself as a compromise between the transmission behavior of both filters.
The Butterworth filter is named after the British engineer Stephen Butterworth, who documented the behavior in 1930. The Butterworth filter is essentially characterized by the constant damping behavior in the passband( DB), which shows a slight amplitude increase only in the region of the cutoff frequency. In the entire passband, the damping behavior has no ripple, in contrast to the Chebyshev filter. Therefore, the Butterworth filter is also considered to be the filter with the maximum flat damping behavior. It is different with the phase behavior and the group delay. The phase response shows a slight nonlinearity which decreases with increasing frequency and the group delay is also frequency dependent. It shows a strong increase at higher frequencies.
Butterworth filters are therefore particularly suitable for the transmission of narrowband signals with different frequencies, between which no amplitude changesmay occur.