function BilinearUnwarp(Freq: Double; FS: Double): Double;
Unwarp: return the digital frequency that an analog (s-domain) frequency maps to under the bilinear transform.
| # | Name | Description |
|---|---|---|
| 1 | Freq | Analog radian frequency omega_a >= 0 to map into the digital band. |
| 2 | FS | Sampling frequency |
| 3 | default 2. $T = 1/FS$. |
Returns: Double - The corresponding digital frequency omega_d in $[0,1)$ (normalised to Nyquist = 1).
Remarks:
Returns the digital frequency Freq's image under the bilinear frequency map for sampling frequency FS, i.e. given an analog radian frequency omega_a = Freq it returns omega_d = 2/pi arctan( Freq/(2 FS) ) . This is the exact inverse of BilinearPrewarp: Prewarp(Unwarp(f)) = f. The sample period is .
References:
[1] Digital signal processing, Vinay K. Ingle and John G. Proakis, Brooks-Cole, 2000