Overload List
| # | Signature | Description |
|---|---|---|
| 1 | void LowpassToBandstopZ(TVec *Num, TVec *Den, double Freq, double BW, double PrototypeFreq); | Apply frequency band transformation from lowpass to bandstop in the z-domain. |
| 2 | void LowpassToBandstopZ(TVec *z, TVec *p, double &k, double Freq, double BW, double PrototypeFreq); | The function returns modified z (zeros), p (poles) and k (gain). |
Overload 1: void LowpassToBandstopZ(TVec *Num, TVec *Den, double Freq, double BW, double PrototypeFreq);
Apply frequency band transformation from lowpass to bandstop in the z-domain.
Freq is the center frequency of the stopband with width BW 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, BW 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) -> (a2 - a1 z^(-1) + z^(-2))/(1 - a1 z^(-1) + a2 z^(-2)) beta = (cos((w2 + w1)/2))/(cos((w2 - w1)/2)) k1 = tan((w2 - w1)/2)tan(wc/2) a1 = (2 beta)/(k1 + 1), a2 = (1 - k1)/(k1 + 1)
wc - old cutoff frequency w2 - desired upper cutoff frequency w1 - desired lower 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 LowpassToBandstopZ(TVec *z, TVec *p, double &k, double Freq, double BW, double PrototypeFreq);
The function returns modified z (zeros), p (poles) and k (gain).