请问下如下Notch Filter用的哪种离散方式?
void computeNotchFltrCoeff(DCL_DF22 *coeff, float32_t Fs, float32_t notch_freq,
float32_t c1, float32_t c2)
{
float32_t temp1;
float32_t temp2;
float32_t wn2;
float32_t Ts;
Ts = 1 / Fs;
//
// pre warp the notch frequency
//
//根据实际测试,结果和以下算式接近:wn2 = 2 * notch_freq * PI_VALUE;
//对Wn2使用 Wn2 = 2/Ts * tan(Wn2 *Ts /2); % 角频率预畸变处理。即可,中心频率能够校畸
wn2 = 2 * Fs * tanf(notch_freq * PI_VALUE * Ts);
temp1 = 4 * Fs * Fs + 4 * wn2 * c2 * Fs + wn2 * wn2;
temp2 = 1 / ( 4 * Fs * Fs + 4 * wn2 * c1 * Fs + wn2 * wn2);
coeff->b0 = temp1 * temp2;
coeff->b1 = (-8 * Fs * Fs + 2 * wn2 * wn2) * temp2;
coeff->b2 = (4 * Fs * Fs - 4 * wn2 * c2 * Fs + wn2 * wn2) * temp2;
coeff->a1 = (-8 * Fs * Fs + 2 * wn2 * wn2) * temp2;
coeff->a2 = (4 * Fs * Fs - 4 * wn2 * c1 * Fs + wn2 * wn2) * temp2;
}