Overload List
| # | Signature | Description |
|---|---|---|
| 1 | void LowpassToLowpassZ(TVec *Num, TVec *Den, double Freq, double PrototypeFreq); | Apply frequency band transformation from lowpass to lowpass in the z-domain. |
| 2 | void LowpassToLowpassZ(TVec *z, TVec *p, double &k, double Freq, double PrototypeFreq); | The function returns modified z (zeros), p (poles) and k (gain). |
Overload 1: void LowpassToLowpassZ(TVec *Num, TVec *Den, double Freq, double PrototypeFreq);
Apply frequency band transformation from lowpass to lowpass in the z-domain.
Freq is the cutoff frequency of the new filter. The function returns modified num and den. PrototypeFreq is the cutoff frequency of the prototype lowpass filter after it has been mapped to z-domain. Freq and PrototypeFreq must be between 0 and 1 (Sampling frequency = 2). The transformation is defined with the following mapping ([1] p. 260 and [2] p. 434, [3] p. 352): z^(-1) -> (z^(-1) - a)/(1 - a z^(-1)) a = (sin((wc - wn)/2))/(sin((wc + wn)/2))
wc - old cutoff frequency wn - new (desired) cutoff frequency
References:
[1] Theory and application of digital signal processing, Lawrence R. Rabiner and Bernard Gold. Prentice-Hall, 1975
[2] Discrete-time signal processing, Oppenheim and Schafer, Prentice-Hall, 1989
[3] Digital signal processing, Vinay K. Ingle and John G. Proakis, Brooks-Cole, 2000
Overload 2: void LowpassToLowpassZ(TVec *z, TVec *p, double &k, double Freq, double PrototypeFreq);
The function returns modified z (zeros), p (poles) and k (gain).