//! fcd = cut-off (1=sampling rate)
//! ord = Filter order
//! ripple = passband ripple in dB
void chebyshev_iir(iir_coeff& filt, float_type fcd, bool lpf, float_type ripple = 3.0) {
const float_type ten = 10.0;
long order = filt.order;
float_type epi = pow(ten, (ripple / ten)) - 1.0;
epi = pow(epi, (float_type)(1. / (1.0 * order)));
float_type wca = tan(0.5 * PI * fcd);
//! wca - pre-warped angular frequency
long n2 = (order + 1) / 2;
chebyshev_s(filt.poles, filt.zeros, lpf, wca, epi, order, n2);
filt.bilinear();
filt.convert_to_ab();
}
//! fcd = cut-off (1=sampling rate)
//! ord = Filter order
//! ripple = passband ripple in dB
void chebyshev2_iir(iir_coeff& filt, float_type fcd, float_type stopband = 40.0) {
const float_type ten = 10.0;
auto order = filt.getOrder();
float_type delta = pow(ten, -stopband/20.0);
float_type epi = delta/sqrt(1 - delta*delta);
float_type wca = (filt.get_type()==filter_type::high) ? tan(M_PI * (0.5-fcd)) : tan(M_PI*fcd);
chebyshev2_s(filt, wca, epi, order);
filt.bilinear();
if (filt.get_type()==filter_type::bandpass || filt.get_type()==filter_type::bandstop) {
filt.make_band(filt.get_center());
} else {
filt.convert_to_ab();
}
if (filt.get_type()==filter_type::bandpass) filt.set_bandpass_gain();
}