int KaiserFirLength(DewArray<double> W, double Ripple, double FS = 2);
Estimate the length of a windowed FIR filter.
| # | Name | Type | Description |
|---|---|---|---|
| 1 | W | DewArray<double> | |
| 2 | Ripple | double | |
| 3 | FS = 2 | double |
Returns the length of the FIR filter, windowed with the Kaiser window, where the maximum allowed ripple of the pass band is Ripple and sampling frequency is FS. The W array holds two parameters: the start and the stop of the narrowest transition band, relative to the specified sampling frequency.
The equation can be found in [1] p. 453, eq. 7.93. The length of the filter designed with kaiser window is about 10% bigger then the length of the filter with the same specifications designed with the remez algorithm. The ripple of the passband and the stopband attenuation of a FIR filter designed with a Kaiser window are related with the equations:
Att[dB] = -20*Log10(Ripple); Ripple = Exp10(Att/-20);
References:
[1] Discrete-time signal processing, Oppenheim and Schafer, Prentice-Hall, 1989.