/// <devdoc>
/// Evaluates the transfer function of a Bessel filter. The gain is normalized to 1 for DC.
/// It returns a complex number that corresponds to the gain and phase of the filter output.
/// </devdoc>
private static Complex TransferFunction(double[] besselPolynomialCoefficients, Complex frequency)
{
var f = new Polynomials.RationalFraction
{
Top = new double[] { besselPolynomialCoefficients[besselPolynomialCoefficients.Length - 1] }, // to normalize gain at DC
Bottom = besselPolynomialCoefficients
};
return(Polynomials.Evaluate(f, frequency));
}
private static double ComputeGainAt(Polynomials.RationalFraction tf, Complex w)
{
return Complex.Abs(Polynomials.Evaluate(tf, w));
}
