BiquadraticFilterModel
BiquadraticFilterModel[{ω,q}] creates a lowpass biquadratic filter using the characteristic frequency ω and the quality factor q.
BiquadraticFilterModel[{"type",spec}] creates a filter of a given {"type",spec}.
BiquadraticFilterModel[{"type",spec},var] expresses the model in terms of the variable var.
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