Biquad
A biquad is a flexible filter that can be thought up as being made up of two simpler filters; a zero (numerator) and a
pole (denominator). In fact, the pre-defined filters mentioned above are really just special cases of the biquad.
Both the zero (numerator) and the pole (denominator) have a flat frequency response at low frequencies and a ris-
ing frequency response at high frequencies. The transition frequency and damping must be specified for both the
numerator and denominator.
Analyzing the numerator and denominator, the frequency response calculation is simple:
If the numerator and denominator are plotted in dB, the biquad response is numerator – denominator. Under-
standing how the numerator and denominator work is crucial in understanding how a biquad frequency response
is created.
Below is an example of a biquad filter similar to a Lead Lag filter type. To help understand how to determine the
frequency response of the biquad, the numerator and denominator response have been plotted. If the denom-
inator is subtracted from the numerator, the biquad response is the result.
AKD User Guide | 14 Tuning Your System
Kollmorgen | December 2010 173
To Next Page
Loading...
